Final Report Summary - ADAPTIWALL (Multi-functional light-weight WALL panel based on ADAPTive Insulation and nanomaterials for energy efficient buildings)
Executive Summary:
Achieving EU’s energy-efficiency targets (2050 goals) depends on the right measures to retrofit the existing building stock, which is dominated by residential buildings. Approximately 85% of the existing dwellings were built before 1990 with poor façade and roof insulation. Current retrofitting solutions focus on airtight (thick) insulated envelopes, needing auxiliary heating, ventilation and cooling (HVAC) systems to compensate for shortcomings of airtightness and high insulation (poor indoor air quality and over-heating). Also, by fully disconnecting outdoor from indoor, potential energy savings by using outdoor thermal energy for indoor heating/cooling are lost. Therefore, a paradigm shift is needed from a rigid insulated envelope to a fully responsive, climate adaptive envelope in order to drastically reduce auxiliary systems and as such accelerate installation and create extra energy savings with respect to current retrofitting solutions.
Adaptiwall introduces an innovative prefab wall system that enables energy savings for heating and cooling of more than 50% in comparison with conventional retrofitting (Rc = 5 m2K/W) by allowing adaptive energy exchange with the outdoor climate. Depending on the climate (region) and total area of the façade replaced by Adaptiwall, savings up to 65% are reached, based on real demonstrator data of two 9 m2 facades and a validated full building model.
ADAPTIWALL offers three functions that can be adapted according to real time outdoor and indoor climate conditions and are integrated in the prefab façade wall:
HEATING: Outdoor heat is harvested, stored in the concrete buffer and released to the inside of the building when needed for (additional) heating.
COOLING: Indoor heat is harvested, stored in the concrete buffer and released to the outdoor environment when needed for cooling.
BREATHING: Indoor air is refreshed with outdoor air with minimal energy loss.
The innovations that enable the integration of the above three adaptive functions are as follows:
The integration in the façade of a glass covered solar collector and an indoor radiator, which are connected to an insulated concrete buffer by an adaptive water loop system.
This allows to use the concrete present in a building as temporary storage in contrast to conventional solar harvesting systems where storage is an issue. Also, the inclusion of a glass covered solar collector allows for 20% higher energy savings compared to other non-transparent adaptive concepts.
The use of lightweight aggregate impregnated with phase change materials (PCM) and alumina in the cement binder of concrete.
This allows lightweight concrete (1600 kg/m3) to store three times as much energy (2.72 kWh/m3/ºC) as normal concrete (0,95 kWh/m3/ºC). The PCMs contribute in the storage capacity and the alumina increases the conductivity with 0.2 W/mK as such contributing in conducting the energy towards/from the PCMs.
The integration of compact ventilation and energy recovery within the prefab façade by using a total heat exchanger (THEX) with an innovative honeycomb separator design and a durable membrane improved for moisture regulation by nano-silica particles.
This allows significantly faster installation times and significant space gain for retrofitting as additional centralised HVAC installation on site is no longer needed. The THEX has an energy recovery efficiency of over 75% based on real demonstrator data of two 9 m2 facades and a validated total heat exchanger model. Also, this unique combination of optimized separator and membrane leads to 15% improved energy recovery and improvement of indoor quality compared to traditional HVAC systems.
Project Context and Objectives:
Project context
Problem
For the construction sector, energy efficient refurbishment is absolutely crucial in reaching the EU 2050 goals considering the fact that about half of the existing building stock in 2012 will still be operational in 2050 and approximately 85% of the dwellings were built before 1990 with poor insulation (R ~ 1.6 m2K/W). Ensuring a high quality indoor comfort is largely responsible for the energy consumption of buildings, on which the envelope, separating indoor from outdoor, has a major impact. Therefore the focus of refurbishment should lie on using the envelope (façade and roofing) to improve indoor environment at reduced energy consumption. Current retrofitting solutions to upgrade the envelope are mainly aimed at drastically increasing the insulation (R values > 3 m2K/W). Unfortunately, this requires thick insulation packages, airtight construction and consequently, additional ventilation and heat recovery systems to keep indoor comfort and air quality at the desired levels. As a result, housing corporations and owners are faced with time consuming and expensive refurbishment related to complex installations, while end users experience discomfort related to reduced space, over-heating and poor ventilation and may still have high energy bills related to additional ventilation and heat recovery systems. As a consequence, full replacement of facades (deep retrofitting) is not often considered in refurbishments. A major market potential therefore exists for construction companies and building material producers if they obtain a cost-efficient, easy and quick to install solution for building envelopes, keeping thickness and additional ventilation installations to an absolute minimum while achieving optimal indoor comfort at significant reduced energy consumption.
ADAPTIWALL breakthrough
ADAPTIWALL aims to tackle the above challenge by developing a climate adaptive multi-functional lightweight prefab panel suitable for cost-efficient, rapid and energy efficient retrofitting of facades (this project) and eventually also suitable for roofing, inner walls or entirely new buildings. For the first time, climate adaptive building components will be combined into a lightweight prefab panel in order to
(1) reduce heating and cooling demands with over 50% compared to current highly insulating solutions,
(2) recover energy from ventilated air at an efficiency of over 75% within the façade and as such reduce and eventually eliminate centralized auxiliary heat recovery and ventilation installations,
(3) reduce envelope thickness by at least 30% and weight by 50% to save space and reduce dead load
(4) fulfill the load bearing, fire safety and sound insulation functions in one single product.
The above targets will reduce energy costs and eliminate expensive and time-consuming onsite installations, making ADAPTIWALL a cost-efficient and quick retrofitting solution for envelopes.
ADAPTIWALL principle
The principle behind the breakthrough of ADAPTIWALL is the climate adaptive approach: being able to adapt energy transfer through the façade allows to take advantage of the outdoor conditions to regulate the indoor conditions at reduced energy consumption, provided there is the possibility of temporarily storing the outdoor heat (or cold) until it is needed on the inside. Therefore ADAPTIWALL combines in a prefab panel both adaptive insulation as well as a lightweight concrete buffer, the latter providing other functionalities of loadbearing, fire safety, sound insulation. Creating the high thermal storage capacity for lightweight concrete requires additives such as nano-silica, alumina and lightweight aggregate impregnated with PCMs. Additionally, the integration of ventilation and a compact total heat exchanger in the panel ensures energy recovery during ventilation and at the same time can regulate humidity and eliminate undesirable gases and dust without the need for additional separate installations. Achieving total heat exchange including humidity regulation while avoiding microbial growth requires membranes with nanostructured substrates.
The objectives and their status (rough indication how far from objective is given by % reached) are described in Table 1 in the attached report
Project Results:
4.1.3 Description of the main S&T results/foregrounds
4.1.3.1 Integrated adaptive panel design and simulation (WP2)
A three-stage approach was followed for the development and design of the integrated ADAPTIWALL panel starting with the simple design, via iterative design optimization to the detailed case design. The design in all these three stages was supported both by numerical simulations as well as by the outcome of lab-scale and prototype experiments.
The detailed design phase resulted in the design of two approximately 10 m2 demonstrator panels used for real-time performance measurements. The data from these measurements was used to validate the numerical simulation models used. The validated model was then used to verify the ADAPTIWAL energy savings ambition for different climates.
Simple design
First numerical simulations provided input and/or boundary conditions for the developments in the material work packages adaptive insulation, lightweight load bearing buffer and THEX. These inputs concerned specific boundary conditions and/or optimizations for the individual adaptive materials, e.g. thermal and physical properties. Figure 1 (left) for example shows how there is an optimum in buffer thickness with regard to its potential to contribute to energy savings.
Figure 1 optimum in buffer thickness (left) and effectiveness of different cladding concepts (right)
Besides input for the individual material developments also on the level of the overall ADAPTIWALL concept input was provided based on the outcome of the simulations. Figure 1 (right) for example shows how the type of cladding strongly influences the ability of the ADAPTIWALL concept to contribute to energy savings; i.e. for gaining solar heat a glass cladding is essential. This learning was translated into different insulation concepts to be investigated in WP3 e.g. switchable, removable and conductive insulation. Different insulation concepts however do not only influence the effectiveness of harvesting solar heat. They also impose a different challenge to the exchange of the heat to the buffer.
Based on the simple design phase it was concluded how, with realistic / imaginable material properties, the ADAPTIWALL energy savings ambitions appeared feasible.
Iterative design optimization
The second phase in the design was the iterative design process where the ADAPTIWALL concept developed through the continuous interactions with the adaptive material components. This phase was supported by numerical simulations, design workshops and prototype testing.
Numerical simulations
The developments in the material work packages were iteratively supported by numerical simulations. This involved for example iterations between lab-scale tests for one of the adaptive components and the overall performance of ADAPTIWALL.
In this phase also the effect of ADAPTIWALL in different climates was added to the earlier simple design simulations. It was shown how the relative savings are highest for intermediate climates such as France and The Netherlands and how absolute savings are highest for more extreme climates.
Finally the simulations were used to derive a control strategy for the ADAPTIWALL concept. Switching of the concept depending on the outdoor conditions and indoor conditions and comfort demands was optimized. This involved the switching of the adaptive insulation in order to transmit energy from the outdoor environment via the buffer to the indoor environment in heating mode and vice versa in cooling mode.
Design workshops
To ensure an efficient integration of all 3 adaptive components into one ADAPTIWALL panel design workshops were held both separately as well as during several GA meetings. This resulted in a.o. things:
- Awareness amongst partners how developments in different work packages strongly interact. This did not only concern the material development work packages (WP3, 4 and 5) but also results from the life cycle assessment work package (WP7).
- Physical boundary conditions due to integration of components, for example the restriction to the buffer thickness caused by the decision to place the THEX in plane with the buffer.
- A design for the 4 prototypes to be tested at the ACCIONA demo park in Algete (Spain) including structural and physical boundary conditions.
Figure 2 lab-scale prototype design for thermal performance testing
- A design for a prototype for fire-safety testing.
Prototype testing
From the lab-scale prototype testing it was learned how the loading and unloading characteristics of the prototypes are comparable to the simulations performed earlier, which gave confidence the envisaged energy savings are feasible.
Furthermore the prototype testing provided input for further optimization of the (design of the) ADAPTIWALL concept. The main learning form the prototypes that affected the design of the ADAPTIWAL concept were:
- Seeing the unwanted heat leakages special attention should be paid to the reduction of thermal bridges at structural connections and the integrity of the surrounding insulation;
- The robustness of the collector plate should be improved in order to be able to handle and install the plate with more ease;
- For all installation components a designated installation area should be foreseen;
- A pump should be added to the thermally driven water-loop system to ensure better controllability and a more effective heat transfer from an to the buffer;
- Laminated glass should be used for the glass cladding to prevent the glass from falling in case of breaking under fire loads.
- To improve the effectiveness of heat transfer to the indoor environment a separate indoor radiator is placed in front of inner finishing layer.
Detailed case design
The final phase of the design process focussed on the demonstrator design and on the translation of this design into reference residential building designs for the Netherlands, Poland and France.
Demonstrator panel design
Based on the learnings from the Algete prototype measurements and given the specific PASSYS test-cells constraints and boundary condition the design for the two demonstrator panels was made.
Figure 3 demonstrator panel design (left) and installed demonstrator panels on PASSYS test cells (right)
The design resulted in a total thickness of the panel of 366 mm measuring from the inner plasterboard finishing to the outer glass cladding.
Residential reference building design
The specific design solutions applied in the demonstrator panels design were translated taking into the retrofit design for 3 locale reference residential building cases. This translation has taken into account the local structural, physical and aesthetic boundary conditions for retrofit design as well as local building practice.
Figure 4 Dutch residential building retrofit design with whole building (left) and detail of ground floor element (right)
To demonstrate aesthetical possibilities the translation of the design also include the design of different façade appearances for different local cases. Figure 5 and Figure 6 demonstrate some of the possibilities by showing the ‘before’ and ‘after’ ADAPTIWALL retrofit situation.
Figure 5 Before and after ADAPTIWALL retrofit (Dutch case)
Figure 6 Before and after ADAPTIWALL retrofit (French case)
Numerical model and energy savings validation
Real time monitoring data from the performance measurements on the two demonstrator panels was used to validate the numerical simulation models. The validation showed good accuracy of reproducing the experimental data by the numerical model.
The validated models were then used to validate the 50% additional energy savings of the ADAPTIWALL concept in comparison to state of the art static retrofit solutions. For different façade configurations and orientations the resulting energy demand is compared to the energy demand of a static reference case (R = 5 (m2.K/W)).
Figure 7 Energy demand for different ADAPTIWALL configurations
As is shown in the figure above for the French case the ADAPTIWALL energy savings ambitions are feasible at a total installed ADAPTIWALL (buffer/collector) area of 25% of the total façade (R1). The additional energy savings for all 3 reference cases vary, depending on the percentage of adaptive façade and/or façade orientation, are:
- French case 50% - 64%
- Dutch case 45% to 54%
- Polish case 43% to 51%
The validated model was furthermore used to investigate the control strategy. It was shown how different control set-points, simulating different inhabitant behaviour, does not influence the additional energy savings by more than 5% showing the robustness of the ADAPTIWALL concept and it’s control.
4.1.3.2 Adaptive insulation (WP3)
The ADAPTIVE INSULATION component of Adaptiwall has the aim of providing panels with switchable thermal insulation, including a regulation system linked to an integrated sensor/monitoring system. Such a panel should switch under the influence of certain triggers from a thermal conductive state to a thermal blocking state, and vice versa.
The best performing and feasible adaptive insulation panel concept fulfilling the energy savings and design demands was found to consist of a waterloop system shortcutting static insulation of which the energy transfer to and from the concrete buffer can be regulated in an adaptive manner by a small water circulator on each waterloop.
Based on the dynamic simulations that were performed within WP2 the required system design and its boundary conditions can be summarised as follows:
Figure 8: boundary conditions adaptive insulation development – (note, the buffer thickness is not at scale)
Identification of requirements for adaptive insulation panels
The main application and material requirements that have to be met in order to have a technically and economically viable adaptive insulation system are:
o Energy from solar radiation needs to be harvested in order to achieve the required savings and as such glass cladding is needed
o An adaptive insulation material with a total insulation target value between 0.12 and 5 m2K/W gives an energy savings of approximately 44-50% compared to the reference case of Rc =5.
o Inner insulation: Simulations have shown that the effect of high insulation values for the inner insulation with regard to energy use is limited. The maximum target inner insulation value of approximately 1.5 m2K/W seems sufficient.
o Switching time should be less than an hour - Depending on the way adaptability is achieved, maximum switching time may vary. While heating of the buffer is largely dependent on solar heat gains (radiation) it may be desirable to be able to switch between states quickly. For cooling switching time is not so critical, since it is dependent on the temperature difference. And outdoor temperature does not switch as quickly as solar radiation. For the inside insulation this rationale applies for both heating and cooling.
o Lifetime – Lifetime needs to be at least 20 years, preferably more. Servicing and/or (partial) replacement should be possible. Thermal and UV resistance –determine the lifetime of the final product. The materials used should be stable in the temperature range of -30°C and +100°C (temperatures reached behind glazing).
o Fire retardancy – All materials used should comply with EN 13501-1 - Fire classification of construction products and building elements
o Ecologically friendly – The final solution should not be harmful to human beings or other organisms.
o Low cost - ROI of 7-10 years for the whole ADAPTIWALL system.
Labscale testing of adaptive insulation panel concepts
The following adaptive insulation concepts were selected from applying the above demands and boundary conditions on a large set of brainstorm ideas.
The EPS spheres concept implies that the properties of the insulation layer can be switched by (partly) removing and storing the insulation material. EPS spheres have target declared thermal conductivity values of ca. 0,033 W/(m.K). As such, in the insulated state, thicknesses of 50 (inner layer) and 150 mm (outer layer) should result in R-declared values of 1,5 and 4,5 (m2.K)/W. In the conductive state the spheres will be (partly) removed and transported to a storage space (e.g. a flexitank), for instance in the crawl space or underground. The critical aspects that came out of the components tests were the low insulation value compared to the declared value, thermal instability, static charging and user acceptance for the EPS concept
The general idea of the shortcut-concept is to directly transport heat from the vertical plane (cladding) to the buffer by means of so-called shortcuts in the insulation layer. These shortcuts by-pass a static layer of insulation. The actual adaptive parts of this concept therefore are the shortcuts themselves which become an integral part of the insulation concept. The shortcuts that were considered first are heat pipes because of their high capacity to transfer heat. The critical aspect that came out of the component tests was the amount of aluminium needed for efficient heat transfer from the heat pipes to the buffer and therefore the cost.
An alternative thermosiphon system was developed for the shortcut concept by which flow is generated from density differences in the water created by temperature differences. Such a system is not vacuum and the expansion of the liquid needs to be taken up by an expansion vessel (similar in heating systems). Calculations have shown that temperature differences will be enough to ensure the water flow. Active control of the flow happens by valves that can interrupt flow and therefore heat transfer.
4.1.3.3 Lightweight concrete buffer
The main objective of the concrete design was to obtain a lightweight structural concrete with improved thermal properties. A lightweight concrete can be achieved using lightweight aggregates like expanded clay, perlite, vermiculite... but these aggregates introduce air in the concrete structure with a decrease of the thermal conductivity, the thermal mass and the mechanical strength.
To obtain a concrete with sufficient thermal and mechanical properties (Table 2) for the Adaptiwall ambitions, additives of different nature were used to achieve the specifications: nanomaterials and micromaterials to increase the thermal conductivity, organic and inorganic phase change materials to increase the thermal mass; porous aggregates to decrease the density and nanomaterials and chemical additives to improve consistency and workability.
Table 2: Required properties in de concrete
Properties Range Unit
Density 1500-1800 kg/m3
Strength 25-40 (C20/25) N/mm2
Young’s Modulus 22-25 kN/mm2
Thermal conductivity 1,5-2 W/mK
Energy storage capacity ≥20000 (at the useful T-range) kJ/m2
Fire Resistance EI 180 Classification
Durability Same as traditional concrete
Sound insulation Same as traditional concrete (**)
(**) depending on the use of the building
All the mechanisms used to achieve those properties are explained below.
LIGHTWEIGHT AGGREGATE
The use of lightweight aggregates is necessary to obtain a lightweight concrete but not all of them give structural properties to the final concrete.
Different aggregates of siliceous and clay origins were studied: perlite, expanded vermiculite, pumice, sepiolite, expanded clay (3-8, 0-4). The most promising were perlite and expanded clay 3-8 because their high porosity, but the mechanical tests (compressive strength) showed that expanded clay is the most appropriate.
The type of cement used was CEM I 52.5 to increase the strength.
PCMs in the LIGHTWEIGHT AGGREGATE
To increase the energy storage capacity of the concrete, phase change materials (PCM) are incorporated in lightweight aggregates by means of vacuum impregnation so that the PCMs can enter the micropores of the aggregate.
Different types of phase change materials with melting points between 15-30 ºC have been studied to investigate the thermal behaviour. The results obtained with organic parafine PCM are the most promising, meaning aggregates were obtained with 40% - 50 % of PCM inside the pores. This means a potential increase in heat storage capacity between 50-80 kJ/kg (depending on the PCM used).
The durability of the impregnated aggregates was tested inside an alkaline solution (pH 11) and with multiple freezing-melting cycles. The results showed no degradation of the material.
Organic PCMs and lightweight aggregates have low thermal conductivity. In order to improve this, impregnation tests with the addition of carbon nanofibers were carried out (1% and 2 %) trying to increase thermal conductivity of the aggregates but no significant effect was observed: neither a decrease in the temperature melting range nor an increase in the total latent heat. Considering this result, the improvement of the final thermal conductivity behaviour of the concrete should be focussed on the binder and concrete formulation.
ALUMINA IN THE BINDER
Different binder mixtures have been studied to achieve an optimization of the thermal conductivity of the final concrete. An improved thermal conductivity leads to faster travel times of the energy to and from the aggregates which are the main storage component of the concrete (including lightweight aggregate impregnated with PCMs). In general, there is a linear relationship between density and conductivity of concrete and most conductivity increasing additives have a high density. However, because of the lightweight objective for Adaptiwall, we are looking for additives that increase conductivity without increasing the density. Three types of cements (CEM I, CEM II, CEM III), different W/C ratios, two types of sand (quartzite and limestone) and three types of additives (Al2O3, SiC, BN, steel fibres, carbon fibres) were used to produce specimens and perform thermal conductivity analysis.
The results show that the use of CEM I is the more appropriate (for the mechanical properties) with the lower rate W/C and the use of quartzite sand and the substitution of part of the cement (20%) with alumina increases considerably the thermal conductivity (>25%) without increasing the density (Fig 9).
Figure 9 : Thermal conductivity of mortar with different formulation/additives
CONCRETE DESIGN
The concrete mix was optimized using all the elements selected in the previous steps: quartzite sand, cement type I, expanded clay, organic PCM and alumina.
The main challenge was to find an optimum between lightweight aggregate and PCM amounts and rheological and mechanical properties. More specifically self-compacting properties were needed for easily the mould compartimentalised by both rebars as well as copper piping. Nanosilica additives were needed and a 50% gravel and sand aggregate replacement with lightweight PCM aggregate was the maximum possible whilst maintaining the necessary mechanical properties.
A summary of the concrete characteristics is shown in the following table:
Table 3: Concrete characterization
THERMAL STORAGE CAPACITY
Different thermal tests were carried out to the concrete to analyse the thermal behaviour of some concrete mixes. A laboratory system with thermocouples and heat flux sensors was used as described in Deliverable 4.3. The collected data is used to calculate the amount of energy absorbed by the samples during the test for changing the concrete temperature. The differences between the heat flux that enters and exits the sample as well the temperature gradient obtained during the same time span, are used to calculate the thermal storage capacity of the sample. Figure 10 shows the temperatures changes in the concrete surfaces subjected to this test.
Figure 10: Temperature evolution in different concrete mixes surfaces
Cyclic tests to simulate the temperature changes during Day-Night were made too and different parameters as maximum temperature differences between both concrete sides and the buffering capacity were calculated. Some of these results are in Table 4 and Table 5.
Table 4: Thermal parameters obtained (* Apparent values)
ΔT peak to peak (ºC) ΔT max (ºC) Δt HF (min) Δt peak to peak (min) Heating Delay (min) TES (kWh/m2/ºC) *
Reference 4,24 4,82 23,80 32,00 125,00 0,94
Adaptiwall concrete 2,27 5,83 72,57 56,43 124,43 2,72
LWC 0,55
Table 5: Buffering capacity : Decrement factor calculation.
Decrement Delay
Cold side (ºC) Hot side (ºC) Decrement Factor*
Traditional concrete (10cm) 10,35 14,35 0,69
Adaptiwall concrete (10 cm) 10,15 12,35 0,43
*The higher the decrement factor, the lower the buffering capacity.
Figure 11: Cyclic test of Adaptiwall concrete
CONCLUSION
A lightweight concrete with PCMs in the aggregate and alumina additives in the binder resulted in an increased energy storage capacity of three times (2.72 kWh/m3/ºC) that of normal concrete (0,95 kWh/m3/ºC). Furthermore, the study of the thermal performance of the concrete shows that the use of PCM increases the thermal energy storage capacity and the ability of keeping the temperature within a certain range. This effect avoids quick heating or cooling of the concrete, which reduces the risk for thermal cracking and prolongs the period during which the buffer is able to cool or heat the indoor room.
Compared to normal concrete, a density reduction 32% has been achieved in a lightweight concrete with structural properties of C20/25. Further reduction of weight implies a reduction of energy storage capacity to values lower than those predicted by the simulations to be necessary for heating and cooling objectives. As the energy reduction objectives are met as shown by demonstrator and simulations, for some climates up to 65%, there is room for lower concrete storage capacity and thus total panel weight reduction by density reduction (including more lightweight aggregate) or thickness reduction of the concrete. However, for the design of the 1 m2 prototypes and the demonstrator, it was decided to keep the buffer thickness of both the Adaptiwall concrete and the traditional concrete exactly the same, following the thickness of the THEX casing, namely 16 cm. Keeping the thickness of the concrete and the THEX which comes next to it the same, they can lie within one plane and insulation panels can surround the total assembly in a more robust and easy way.
4.1.3.4 Adaptive insulation-concrete buffer combination: 1 m2 prototypes
After the selection of the final adaptive insulation concept (4.1.3.2) and concrete design (4.1.3.3) 4 lab scale prototypes of the ADAPTIWALL panel were built at the Demo Park of ACCIONA at Algete, in Spain. Purpose of the prototype measurements was to demonstrate the ability of the integrated system to harvest solar energy, store this in the buffer and transmit it (on demand) to the indoor environment.
The construction of the prototypes took place in September and October 2015 and measurements were started in November 2015 and are finished in June 2016.
Different prototypes were produced for the thermal performance study of the panels at the Algete demopark in Madrid and othe for fire resistance test.
For the thermal study, the final decision of the buffer design for the prototypes was 4 concrete buffers with three different natures:
1- Reference: Lightweight (LWC) concrete → 1500 kg/m3
2- Modular: LW concrete (to compare different insulations and switching systems) → 1500 kg/m3
3- Adaptiwall 1: LW concrete with PCM impregnated in aggregates (and alumina)→ 1600 kg/m3
4- Adaptiwall 2:Traditional concrete with PCM in containers→2300 kg/m3
The design and production of the concrete buffer was a complicated task. Due to the fact the concrete buffer is the structural part of the panel, numerous of anchors had to be incorporated inside of the concrete as well as the internal part of the thermosiphon (copper pipes) had to be casted in the concrete.
Figure 12: Piping, anchors and casings installation and sensors placed.
After the internal structure installation, 100 L of concrete was poured and after 28 days of curing, the four panels were installed at the demonstration park.
Figure 13: The 4 concrete panels installed at the demo park.
The outside collector plate (Figure 14) and inside heat exchanging plate (Figure 15) are shown below.
Figure 14: Outside collector
Figure 15: Inside heat exchange / transfer plate
Harvesting-storage potential
The 1m2 prototype measurements successfully demonstrated the operability of the system to harvest solar energy and store it in the buffer. Valves were controlled by actuators to start or stop the thermosyphon heat exchange when necessary. Figure 16 shows the reaction time of the system to the opening of the valves. With the appearance of solar radiation, the temperature in the outside water loop increases. The difference between temperature values at the top (orange) and bottom (yellow) of the water loop corresponds to the increase of the buffer’s temperature (purple). It demonstrates that the targeted heat conduction between the casted pipelines and the concrete buffer, which results heat storage in the concrete, effectively takes place as is shown in Figure 16.
Figure 16: Temperature profiles in an ADAPTIWALL lab-scale prototype (No 2)
Figure 17: Temperature profiles in an ADAPTIWALL prototype (No 2)
In Figure 17 the capacity of the system to heat up the concrete is demonstrated. This was the main objective of the adaptive insulation system: shortcut the static insulation when needed to heat up the concrete buffer behind it when solar radiation is available and heat is needed. Though an effective loading of the buffer was demonstrated, some unwanted heat leakage out of the buffer was found indicating that for the demonstrator panels more attention should be paid to the thermal insulation of the buffer; e.g. the detailing of structural fixings.
The second functionality of the adaptive insulation was to transmit the stored heat from the concrete buffer (yellow line in Figure 18) to the inside air (green line in Figure 18) to contribute to decrease the indoor heating demand. This function is presented in Figure 18.
Figure 18 Effect of buffer loading on room temperature variation: heat transmission by adaptive insulation system
From the prototype measurements it can be concluded that thermosiphon waterloop system system is able to fulfill the function of the Adaptiwall panel requirements. It enables an effective harvesting of solar energy through the outer collector, transmit this energy to the buffer and store it in the buffer. From the buffer the inside waterloop transmits energy to the room ambient air.
Mechanical tests prototypes
We may conclude that the measured mechanical properties of the ADAPTIWALL buffer fulfill the requirements for the structural design of panel which was based on a regular C20/25 concrete standard. Even more satisfying, the use of PCM lightweight buffer exceeds both the characteristic compressive strength (by a 7%), the axial tensile strength of the lightweight LC20/22 standard (in a 30%) and performs a 10% better than C20/25 concrete on the flexural stress test.
Table 6: Mechanical properties comparison of standard classification and test results
CONCRETE SAMPLES Compressive Stregth (fck,cube) Bending tensile strength (fctm) Density
(ρ) Classification (EN206-1)
Lightweight concrete (test) 24.2 MPa 1.42 MPa 1510 kg/m3 LC20/22
ADAPTIWALL Lightweight concrete +PCM 23.1 MPa 2.11 MPa 1630 kg/m3 LC20/22
Traditional concrete (standard values C20/25 *) 25 MPa 2.6 MPa 2400 kg/m3 C20/25
Lightweight concrete (standard values LC20/22 *) 22 MPa 1.97 MPa 1401-1600 kg/m3 LC20/22
*Eurocode 2 data and calculations
Fire test prototype
The standard followed for the fire test is UNE EN 13823:2012 for which a specific test specimen is needed. A corner of 1,5 m high and 20 cm of thickness was designed for the whole panel. Due to the limitation of the thickness, only half of the panel could be tested and only the external face of the panel was included (glass+ external thermosiphon+insulation+10 cm of concrete).
Figure 19: Formwork and fire test prototype
Recommendations demonstrator
Based on the 1m2 prototype monitoring campaign in Algete and the mechanical and fire testing, the following recommendations are made for Adaptiwall which are included in the 10 m2 demonstrator.
Table 7: final design recommendations
Total heat exchanger
The objective of this work was to develop a compact Energy Recovery Ventilation (ERV) system panel component that fits within the Adaptiwall prefab panel, allowing heat recovery between fresh and exhaust air with an efficiency of over 75% and humidity control during ventilation. This development can be divided into three subtasks:
As a first step, specifications and requirements have been set for the realization of a total heat exchanger (THEX) integrated within the size of the ADAPTIWALL panel. A numerical model were set up, so several parametric studies were performed in order to:
Define technologies and dimensions of separator
Define membrane properties to target, in order to reach latent efficiency as defined in the specifications, as well as to determine a baseline membrane to be improved
Define arrangement of system in the wall
Define the THEX modulus for the TRNSYS dynamic simulation (done in WP2)
The second step of the development concerned the definition of the available place to integrate the THEX module to the ADAPTIWALL demo panels.
The third step was the post treatment study of selected membranes of THEX.
The relevant points to retain from the first step are the following:
In general it can be said that the mass transfer area available for each kind of separator and the ability to develop large convection coefficients, thermal and mass transfer, play a combined and a major role in the moisture transfer performance.
The separator “Nidab Large” is clearly the one which brings the best sensible performances. However, a potential pressure drop generation, which could surely be a bit larger than the conventional separators, has to be taken into. But, as the Reynolds number in the channel will be very low in the demonstration configuration (<200), the extra pressure drops, comparing to standard separators will not be critical indeed.
Whereas the identified baseline membrane Pebax1657 is cheaper and more durable, its moisture transfer performances are clearly not as good as the ones of the commercial microporous reference membrane of the market. Mass efficiency is between 5 and 15% lower, depending on the average humidity condition at the membrane, but the moisture transfer is well effective and is improved in step 2 and 3.
The graph below shows evolution of Nusselt number as function of Reynolds number for all the membrane separators tested. Nusselt number allows qualifying the ability of technology to promote convection in the flux and at the surface of the membrane. Indeed “Nidab Large” separator brings strong advantage in comparison with other configuration of channel.
The relevant points to retain from step two (potential membrane’s formulation improvement) are the following:
The dispersion of nanoparticles of silica (170m²/g) in a blown-extruded membrane of 33μm of thickness allows a net improvement of moisture transfer, comparing to the Pebax MH1657 baseline membrane. Experimental apparent diffusion coefficient as function of relative humidity at the membrane is slightly better than the one found for the baseline membrane. In terms of performance, the latent efficiency is almost at the level of the commercial membrane, reference of the market. These results open furthermore a lot of optimization perspectives, especially concerning the multiple parametric configuration, like the concentration, the process to disperse nanoparticles in the compound, or other hydrophilic nanoparticles.
A numerical comparison (calibrated with experimental results) of the state of the art (SoA) configuration (commercial membrane and conventional separator) with the ADAPTIWALL solution (improved baseline membrane with “Nidab large” separator), has demonstrated that the ADAPTIWALL solution allows an increase of sensible and latent performances between 10% and 20%.
The initial objective to achieve a global enthalpy efficiency of 75% is anticipated to be reached based on the results of lab scale experiments and with the help of numerical model (in summer and winter condition) and the demonstrator experimental campaign has to validate also this result.
The figure below illustrates these numerical projections.
The relevant points to retain from step three (potential membrane improvement by a post treatment) are the following ones:
Experimental results show that embossing and/or application of a hydrophilic coating, bring improvements for some membranes and conditions, but did not seem to bring significantly strong advantages on the moisture mass transfer rate in the membrane in general but are too dependent on the relative humidity at the membrane. It was surprising that imprinting did not improve the performance of the moisture transport, as it was observed with numerical modeling with the kind of structure studied.
Unfortunately, the silica modified membrane of 33µm thickness was not included in the post treatment research as the results of the efficiency of this membrane was not known at the time of the post treatment experiments were performed and the PVA modified material seemed the better choice at that time. As no post treated membranes are available with properties better than the 33µm silica modified membrane, no post treated membrane will be used for the membrane of demonstrator.
THEX system arrangement in the panel
This task had been treated in collaboration with the other work packages (WP2 and WP6) and deals especially with the following detailed points:
Mechanical assembling aspects (integration in Adaptiwall panel)
Technical assembling aspects (fan, frame, casing, separator, filter, maintenance access...)
Control and regulation aspects (by-pass and condensation management...)
Piping and instrumentation aspects (sensors, actioner, pipe connection...)
CFD flow distribution studies are done, pressure drop of heat exchanger and filter are being calibrated, with a focus on the pressure drop of the system (specifically due to the by-pass) and also on the homogeneity of the flow rate at the nose of channels in the admission area. Design of air flux distribution of THEX has been optimized in this way. The figures below illustrate the assembling of the THEX prototype as a standalone appliance. Two instrumented prototypes were manufactured.
Firstly, the casing of the system with the top cover is described. Air tightness has been studied especially.
Secondly, frame and separator are assembled together by adhesive strip.
The stacking of the plates of each pass of fluid (a frame plus a separator), including membrane intercalation between each plate, is achieved. Membrane is set in a one way mode, by wrapping alternatively one side of each plate, double face adhesive strip is used to fix membrane on the frame and assure air tightness of assemblage.
By-pass system is configured directly in the casing. The calibration of the bypass rate is planned on the month of July. A specific algorithm is setup in the way to assure zero condensation occurrences in the THEX while the energy saving is optimized. This algorithm allows to determine a ratio fresh air bypass in function of two only parameter (fresh air and exhaust air temperatures inlets).
Demonstration total Adaptiwall
The aim of demonstration activities is to integrate all Adaptiwall elements, adaptive insulation, buffer and THEX, into two demonstration panels and asses the thermal performance of the multi-functional system through monitoring. First task focussed on the integration and manufacturing of the two panels to be installed at INCAS experimental platform of CEA INES. The following parts of the process were handled within the project:
Manufacturing of sub-components (e.g. lightweight buffer) and supplying all elements to CEA,
Drafting a handbook for the assembly process,
Security procedures of lifting
Reception on the INES platform.
Supplying
The concrete buffer production was covered by ISODAL who was responsible for casting and transporting the buffer to CEA. All the necessary elements were supplied to Isodal, e.g. the PCM impregnated aggregates by ACCIONA, the shortcut adaptive insulation (water loops) by CEA and mechanical resistance calculations and rebar positioning by Snijders. All supplementary elements such as Window, glass cladding, timber frame, auxiliary elements were delivered by FASADA directly to CEA for final assembly in the two demonstrator panels. Originally the assembly of the demonstrator panels was scheduled to take place in Poland at Fasada. However it was decided that, mainly from a pragmatic point of view, not to ship all Adaptiwall elements back and forth all over Europe. Assembly and manufacturing directly at CEA in France was found to be more efficient. This change resulted in an unforeseen a delay of the installation process which resulted in an reduction of available measurement period. Consequently deep winter conditions were not addressed, nevertheless heating demand reduction have been assessed according to the initial work plan enabling the validation of the overall ADAPTIWALL energy savings ambitions.
For the assembly process a handbook was edited by Fasada (supported by Snijders) describing the assembly / manufacturing of the panels and the actual installation of the panels on the PASSYS cells step by step. Based on the experience with the manufacturing of the prototypes special attention is paid to the division of activities and/or responsibilities during the process.
Security procedure of lifting
Lifting and handling heavy façade elements requires some extra security check within CEA’s experimental activities. Potential risks of shared responsibilities was studied between actors of WP6 and discussed with the CEA INES security-officer intensively. Detailed process was reported in deliverables D6.1 and D6.2.
Reception on the INES platform
INCAS platform dispose 4 PASSYS test cells from whom 2 were used for ADAPTIWALL for demonstration activities. In order to be able to assemble all elements to the PASSYS test cells, a special technical area has been blocked around the work zone. Finalized demonstrator panels are presented in Figure 20.
Figure 20: Finalised ADAPTIWALL panels at INES
The next step concerned the performance testing of the demonstration façades. This task covers measurement activities on two demonstration façades installed at INCAS experimental platform at CEA INES. Three main activity were distinguished:
Optimisation
Instrumentation
Data recording and analysis.
Optimization:
The composition of the ADAPTIWALL demonstrator panels is very similar to the lab scale prototypes installed at Algete, Spain in 2015 (cf. WP2 activities). The differences are due to the optimisation process engaged since the Spanish experimental campaign and the efforts to get the closest to the real case situation. Main differences are:
Water loops are simplified, no thermosiphon functioning but pump controlled water flow is set up. The importance of the water pumps is that the heat storage and the heat discharge can be better controlled and optimised by controlling the operation and the flow rate of the outside and the inside pumps. Hence, more energy saving potential can be achieved compared to the thermosiphon system (no pumps) by considering this optimisation even though the pumps will consume some amount of electrical energy.
Less actuator is involved;
Two demonstrators were installed: PASSYS4 without PCM in concrete buffer, PASSYS 3 with PCM in concrete buffer (see Figure 20).
Window was added in each demonstrator to represent real dwellings.
Roller shutter was installed in front of the window and of solar absorber (overheating protection supposed not to be used).
Total heat exchanger (THEX) was added in each demonstrator in order to verify its performance (that was previously measured at lab scale) under real conditions.
Technical area was included in each wall panel to show the space that this area will occupy in real future installations
Inside radiator is included in the inside water loop (brand Radson, type Vertical) that represents the water-to-air heat exchanger between the buffer system and the inside space.
Instrumentation:
The prototypes (presented in Figure 20) are prefabricated and composed by the three main ADAPTIWALL components, namely: the lightweight concrete buffer, the shortcut concept adaptive heat insulation and the THEX (total heat exchanger air handling unit). A standard window and a glass cladding in front of the solar thermal collector complete the final version of demonstrators.
As a first step, instrumentation had been defined and casted sensors delivered to ISODAL during the manufacturing process of the concrete buffer. A special support was developed to fix thermocouples to the cooper pipeline in order to keep sensors in place during the casting process. Surface sensors were installed directly at INES in and on the demonstrators as shown in Figure 21 and Figure 22.
Figure 21 Sensors placed on buffer surface
Figure 22 Sensors installed in THEX air ducts
Data recording and analysis:
Global measured data with scenarios are presented in Figure 23 and Figure 24.
Figure 23 Measurement scenarios N°1 to N°6 in PASSYS 3
Figure 24 Measurement scenarios N°7 to N°14 in PASSYS 3
The working principle of the system: heat transmission from outside to the buffer, energy storage in the buffer, and heat transmission from buffer to the inside was demonstrated as shown in Figure 25. This is the normal functioning of the ADAPTIWALL concept during heating period or during mid-season when indoor climate requires additional heating, which in the case of ADAPTIWALL is provided by harvesting solar energy. The cooling behaviour was much more complicated to demonstrate. Here we conclude that added devices are required to achieve the desired cooling performance objectives: shading in front of the window to limit solar gains and rolling shutter in front of the outside solar collector during the day to avoid solar energy harvesting. With this latter we limit the warm up of the collector and keep the temperature difference between the buffer and the plate optimal to be able to discharge the stored heat from the buffer to the outside during the cooler (night) periods.
Figure 25 Experimental data
Measured data served to calibrate and validate WP2 numerical models. With these calibrated models the ADAPTIWALL energy saving objectives were validated and are presented in 4.1.3.1.
THEX results
During demonstration activities, one THEX was integrated in each ADAPTIWALL demonstrator panel. Special scenarios as well as background functioning were tested during measurements. Main achievements with efficiency measurement are presented below.
The performance indicators of the THEX panel are defined by the sensible, latent (moisture), and enthalpy effectiveness as shown in Figure 26. It is sure that these indicators are calculated when the by-pass is closed. They are also dependent on the working conditions; i.e. the temperature and humidity ratio at the inlets.
For the temperature effectiveness, η_s is in the range of 0.7 to 0.8. At night time, we obtain higher values for η_s than that during daytime due to the higher temperature gradient between the inlets. During all the considered period, η_s decreases to low values (0.5-0.6) during daytime of the last day. The reason is the very low temperature difference between the inlets. For the moisture effectiveness, η_l is in the range of 0.5 to 0.7. η_l shows very high values, more than 0.7 for very high absolute humidity differences between the inlets. For lower differences, η_l is around 0.55-0.6. For scenario three, when the moisture generation is turned OFF, we obtain a high dispersion in the moisture effectiveness due to the very low differences (less than 0.5g/kg) between the two air flow inlet absolute humidity. Accordingly, the effectiveness calculation during this scenario is not accurate. The enthalpy effectiveness is between 0.6 and 0.7. Its behaviour follows the behaviour of the temperature effectiveness.
Figure 26: The sensible, latent, and enthalpy effectiveness of the heat exchanger
From the demonstration activities we concluded that:
The sensible effectiveness is more than 77% when the temperature difference between the inlet fresh air and the inlet exhaust air is more than 8°C. This temperature difference is usually the case when considering winter and/or summer conditions depending on the climate. The sensible effectiveness decreases with the decrease in the inlet temperature difference
The latent effectiveness is 60% - 70% when the humidity ratio difference between the inlet fresh air and the inlet exhaust air is more than 5g/kg. The latent effectiveness decreases with the decrease in the inlet temperature difference.
The total (enthalpy) efficiency is also a little bit lower than that found in the lab-scale measurement (around 3% lower) at 70 %.
For highly insulated buildings, the heating demand due to ventilation requirements represents around 30-40% of the total heating demand of the building. Therefore, the total heat exchanger solution integrated into the façade as a decentralised ventilation system can reduce up to 75-80% the energy consumption due to ventilation requirements. In addition, thermal comfort is enhanced due to the high humidity recovery potential of the system.
Potential Impact:
4.1.4.1 Environmental and economic impact
Here, a summary is presented of the LCA, LCC and HHRA assessment of the materials, developed panel and refurbishment strategies carried out for the Adaptiwall Panel. The overall conclusions of this study are discussed below, for figures accompanying these conclusions is referred to Deliverable D7.1.
• GWP results in the production stage of the three alternative materials (EPS Spheres, Heat pipe, and Thermosiphon system) present that the Thermosiphon alternative is the most favorable alternative in terms of the environmental aspect.
• The GWP simulation results in the production stage of the four concrete alternatives: typical lightweight concrete, lightweight concrete with PCM, lightweight concrete with PCM and alumina and concrete, show that two lightweight concrete alternatives with PCM have just 2% of difference in emission of CO2 to atmosphere. Contrary to typical lightweight concrete studied in the chapter 6.3.1 this difference between typical lightweight concrete and lightweight concrete with PCM and with PCM and alumina is about 19-21% , but it is much smaller than in the case of concrete and typical lightweight concrete (approx. 31%). It is because there is less cement in concrete than in a typical lightweight concrete. The difference in performance between regular lightweight concrete and lightweight concrete with PCM impregnated aggregates is currently being measured in the WP6 demonstrator. Preliminary results show that the difference in terms of energy savings lies around 60%. This means that pay-back time is 14 years, for an additional investment for a typical Dutch reference case of 3600 €, lies around. Therefore this option was selected for the ADAPTIWALL studies.
• The presented economic results in the production stage of the three alternatives (EPS Spheres, Heat pipe, and Thermosiphon system) show that the Thermosiphon is the most favorable alternative in terms of the economic aspect. This confirmed earlier environmental studies (chapter 6.2) that this material should be taken into account in further ADAPTIWALL panel analysis.
• From an LCA point of view is ADAPTIWALL retrofit is more preferable than state-of-the-art retrofits (Rc = 5 m2K/W) only in the construction and end of life stages. For the total LCA, Adaptiwall has a higher total CO2 footprint (around 150-200 kg CO2/m2 façade) than state-of-the-art retrofitting (around 100-150 kg CO2/m2 façade). However, it should be emphasised that comparison is made with a state-of-the-art retrofit of already Rc = 5 m2K/W. If comparison is made with the total CO2 impact of an average non-retrofitted reference house, which is at least a few 1000 kg CO2/m2 façade (see for example the reference house of EU funded project EmInInn (2011-2015)), the LCA impact difference between current state-of-the-art retrofitting and Adaptiwall retrofitting is not very significant. Together with this, it should be noted that an even more honest case comparison both for LCA and LCC should include a deep retrofit, also replacing the inner wall in the state-of-the-art retrofit as is done in the Adaptiwall retrofit because that increases the material use and comfort in the reference to levels more comparable to Adaptiwall.
• In general, the above observations are related to the fact that there is a trade-off between adding technologies for energy reduction to buildings versus extra material use for these materials. This is even seen already in the state-of-the-art reference in which the CO2 impact in the use stage is only counting for 6% of the total impact in the use stage which is mainly related to material replacement. One of the conclusions of the EU funded project EmInInn (2011-2015) which developed environmental macro indicators for innovation, is for example that stimulation is needed for sustainable innovations in the built environment, which do not steer so much towards reducing energy consumption (e.g. insulation, eco-boilers) but replace the energy source, i.e. make use of renewable energy sources. If use is made of renewable sources, the rebound effect of higher energy impact related to energy needed for cooling and comfort by extra installations is less of a problem for environmental impact. This is exactly what Adaptiwall is doing, energy harvesting is included in the façade.
• Further development of Adaptiwall including optimisations for the concrete panel: thinner, less or no PCM (depending on proven energy savings in future), optimization rebars etc will further bring the LCA and LCC of Adaptiwall at similar levels as for state-of-the-art retrofits (Rc = 5 )
• In all cases, no health risks are expected due to indoor domestic exposure as a consequence of the materials installed during the renovation, since all exposures remain well below the derived health limit values, if available. There is overlap in emitted substances between traditional and ADAPTIWALL retrofitting, although ADAPTIWALL potentially emits more different substances. From the HHRA point of view ADAPTIWALL panel is not classified as a dangerous, it has the same impact as traditional retrofit panel.
• Dust and quartz emission do not cause major health concerns. However, it is recommended to use a respiratory protection that sufficiently reduce the risk of quartz exposure
• As described in previous paragraphs, it is foreseen a reduction from 430€/m2 of initially calculated material cost for ADAPTIWALL retrofit, to an average in between 354-371 €/m2 depending on where the upscaling of manufacturing will take place.
• It is also predicted and estimated economic optimization in overall investment costs from a total of 391 to 591 €/m2 depending on where the final production stage and building retrofitting is going to take place. This value can compete with for example state-of-the-art deep retrofitting in which the total façade is replaced.
• Because of the relatively high initial costs of Adaptiwall and the different TRL levels of its components, the implementations strategy is set up around individual Adaptiwall components for early exploitation towards exploitation of the full Adaptiwall in later stages.
4.1.4.2 Implementation and commercial exploitation strategy strategy
In general it was shown in the LCC study that ADAPTIWALL is a highly competitive solution in comparison to current (near zero energy) deep retrofit solutions. One key distinguishing element is the fully prefabricated and integrated ventilation solution besides other competitive advantages such as:
- Better Indoor (cooling) comfort
- More efficient transport (due to weight reduction)
- Space savings
- Faster renovation time related to the use of decentralised heating/ventilation units.
Although the rate of deep retrofit is expected to grow, currently this type of renovation solution represents approximately 1.5 to 2% of current retrofit market. On the short term emphasis will be put on in the implementation of individual parts and/or technologies of the ADAPTIWALL concept. On the longer term the ADAPTIWALL concept as a whole will be implemented.
Below the exploitation strategy for the different exploitable results are further detailed.
Implementation strategy as a basis for commercial exploitation strategy (through producers and chains of subcomponents)
For all of the results, exploitation strategy in short, mid and long term perspective was analysed and developed. The list of updated key exploitable results is presented in Section B (table B2).
Results: 1 Smart thermal façade and 6 ADAPTIWALL panel
In short term perspective following sub-results are expected:
• 1/6a. Standardized small dimension (1-2m2) adaptive façade panels: In mid-September TNO will submit national research project with industrial partners in order to optimize adaptive façade panels.
• 1/6b. Simplified ADAPTIWALL façade panels: Optimization of the solution through the integration of “invisible solar collector” (for example TNO currently participates in other research project in this topic with AKZO). Promising exploitation route is to use standard roof collectors and in this way achieve freedom in choice of the cladding material. Currently this solution is discussed with Dutch prefabrication industry. Currently the ADAPTIWALL collector is optimized for intermediate EU climate, but has the intrinsic flexibility to anticipate to more extreme climates; e.g. an uncovered collector to optimize cooling efficiency for warm climates. Also currently an ADAPTIWALL panel holds a separate THEX unit and technical area, both separately accessible for installation and maintenance. Integration of both, preferably only one per panel, minimized and positioned behind the inner radiator seems favourable giving better occupant acceptance.
• 1/6c. Improved energy efficiency: The goal is to optimize the solutions in order to improve the use of stored heat in concrete buffer. Currently the temperature of the buffer is >25°C and it transmitted via radiator. However if the temperature would be between 20°C-25°C the transfer with the ventilation would be performed. In case of temperature in the buffer <20°C the heat can be a source for heat pump.
In Mid- term perspective:
• 1/6d. Adaptive insulation with normal lightweight concrete: Market introduction should be made through the pilot retrofits and implementation of ADAPTIWALL in real building. Important aspect is to optimize the collector and energy efficiency (better use of stored heat) for full ADAPTIWALL solution. Another aspect is the optimization of the design in order to achieve plug and play solutions. Currently CEA is investigating the patenting of the control system of ADAPTIWALL
In Mid and Long-term perspective
• 1/6e. Adaptive insulation with PCM concrete
Results: 2 Concrete formulation and 3 ADAPTI-buffer
In short and mid-term perspective following sub-results are expected:
• 2/3a. Lightweight buffer for floor/wall heating in low energy massive houses: PCM’s results in better energy efficiency due to a better energy storage capacity. However because of relatively high cost of PCMs, there is potential for use of standard concrete for a buffer. This option also will allows to achieve significant energy savings. Lightweight buffer (without PCMs) can be apply for floor heating in low energy massive houses (on-going discussion with manufacturer of prefab building components).
• 2/3b. Lightweight PCM impregnated buffer for floor/wall heating in low energy massive houses. In mid-term perspective lightweight buffer with PCMs for floor/wall heating can be applied
• New application of concrete with improved thermal conductivity: Increased thermal conductivity can contribute to control heat development during production (casting) of large (usually infrastructural) concrete structures, potentially even avoiding additional cooling. TNO is currently investigating the potential advantages in terms of sustainability, process optimization and costs amongst contractors in the Netherlands.
• 2/3c. Consultancy and development on PCM impregnation and application: Further development of PCMs impregnation process will be performed by Acciona. The applied PCM’s are optimized for intermediate EU climate. The potential to anticipate to more extreme climates can be investigated; e.g. PCM’s with low melting points (<200C) to optimize cooling efficiency for warm climates.
Results: 4. Non porous membrane / 5. THEX
In short and mid-term perspective following sub-results are expected:
• 4/5a. THEX in prefab retrofit panels with (patented) separator and conventional membrane: Part of market introduction should be done through pilot retrofits and implementation of ADAPTI-WALL in real building. Significant cost advantages of integrated auxiliary installations should to be exploited, especially in deep retrofit projects. CEA will check the possibility for next patent regarding a new method of bypass management for Energy Recovery Ventilation system
• 4/5b. THEX technology applied in / translated to traditional HRV: Efficiency of centralized state of the art systems lies in the order of 65% showing potential for application in centralized Heat Recovery Ventilation (HRV) systems . CEA is currently consulting manufacturers of HRV systems for potential development and installation in buildings (both new built and retrofit).
• 4/5c. THEX technology with improved nano (structured) membrane: Nano structuring of the membrane was discarded for practical reasons in current solution but has shown great potential. Therefore the second generation membrane will be developed by PROCHIMIR and CEA.
• New application of membrane technology: Further exploitation by PROCHIMIR (membrane developer) and application of membrane in different sectors: medical sector, food packages sector.
4.1.4.3 Dissemiation and exploitation within project
Partners of ADAPTIWALL project participated in almost 50 conferences and workshops, published 4 scientific papers, submitted one patent application no PCT/EP2015/071944 on Heat exchanger system with improved performance and improved compactness. The patent was submitted by CEA and consists of a specific arrangement of the Energy Recovery Ventilation system into the wall, which enable simultaneously, a better efficiency (due to an pseudo adiabatic peripheral behavior), a bypass function when it is necessary, a better flow distribution (no air short cut possible), and an improved compactness of the appliance. Currently CEA is interested in depositing of second patent about on a new method of bypass management for Energy Recovery Ventilation system.
During the project duration following dissemination tools were created:
see table in the attached report.
Several meetings with industry were undertaken in order to verify and analyse the market acceptance and short-term possibilities for the ADAPTIWALL system. First set of meetings were undertaken by the TNO and Snijders in the Netherlands. The concept of the ADAPTIWALL system was discussed with two manufacturers of prefabricated building components: IQ-woning and Hurks. Those stakeholders offer completely prefabricated standardized units for new construction and intend to develop renovation concepts. Second parts of the meetings took place in Poland, France and Spain:
- In Poland the concept was discussed by FASADA with the architect office IBJK architects), construction company (KB Doraco) and the City of Gdynia (which is a public stakeholder)
- In France a meeting with GA was undertaken by CAE. This company manufactures various components required for buildings, amongst them is the system NEWSKIN, which is an innovative, flexible, quick solution for building renovation.
- In Spain, Acciona had a meeting with the Spanish Institute of Cement and its Applications – IECA.
During the project timeframe several internal exploitation workshops were organized. During those workshops IPRs issues, market potential of each results and further exploitation activities were discussed.
Final ADAPTIWALL workshop was organized at month 41 during trade fairs BAU 2017, the German Leading Trade Fair for Architecture, Materials and Systems . The fairs were organised in Munich between 16 – 21th of January 2017. ADAPTIWALL and project REESEEPE, FASIDUR, ECO-BINDER, GELCLAD, QUANTUM, HOMESKIN, InDeWag and WALL-ACE under the umbrella of European Construction Technology Platform co-shared the exhibition booth and presented various solutions and technology for energy efficient retrofits that are developed under research projects funded by European Commission. The visitors of the booth had the opportunity to be informed about the working concept of ADAPTIWALL prefab system, received the publicity material about the project, saw the promotional video and small prototypes of selected components. Together with cluster projects ADAPTIWALL co-organised the workshop “From research to market, Innovative technologies and ICT solutions for energy efficiency” that was held on 19th of January, 2017.
Participation in BAU 2017 increased the visibility of the project to target audience and was a great opportunity for project partners to discuss with other exhibitors about potential collaboration and market uptake of ADAPTIWALL system.
Within the project timeframe exploitation strategy for individual exploitable results was developed. The strategy is presented in Chapter 4.1.4.2
List of Websites:
www.adaptiwall.eu
Achieving EU’s energy-efficiency targets (2050 goals) depends on the right measures to retrofit the existing building stock, which is dominated by residential buildings. Approximately 85% of the existing dwellings were built before 1990 with poor façade and roof insulation. Current retrofitting solutions focus on airtight (thick) insulated envelopes, needing auxiliary heating, ventilation and cooling (HVAC) systems to compensate for shortcomings of airtightness and high insulation (poor indoor air quality and over-heating). Also, by fully disconnecting outdoor from indoor, potential energy savings by using outdoor thermal energy for indoor heating/cooling are lost. Therefore, a paradigm shift is needed from a rigid insulated envelope to a fully responsive, climate adaptive envelope in order to drastically reduce auxiliary systems and as such accelerate installation and create extra energy savings with respect to current retrofitting solutions.
Adaptiwall introduces an innovative prefab wall system that enables energy savings for heating and cooling of more than 50% in comparison with conventional retrofitting (Rc = 5 m2K/W) by allowing adaptive energy exchange with the outdoor climate. Depending on the climate (region) and total area of the façade replaced by Adaptiwall, savings up to 65% are reached, based on real demonstrator data of two 9 m2 facades and a validated full building model.
ADAPTIWALL offers three functions that can be adapted according to real time outdoor and indoor climate conditions and are integrated in the prefab façade wall:
HEATING: Outdoor heat is harvested, stored in the concrete buffer and released to the inside of the building when needed for (additional) heating.
COOLING: Indoor heat is harvested, stored in the concrete buffer and released to the outdoor environment when needed for cooling.
BREATHING: Indoor air is refreshed with outdoor air with minimal energy loss.
The innovations that enable the integration of the above three adaptive functions are as follows:
The integration in the façade of a glass covered solar collector and an indoor radiator, which are connected to an insulated concrete buffer by an adaptive water loop system.
This allows to use the concrete present in a building as temporary storage in contrast to conventional solar harvesting systems where storage is an issue. Also, the inclusion of a glass covered solar collector allows for 20% higher energy savings compared to other non-transparent adaptive concepts.
The use of lightweight aggregate impregnated with phase change materials (PCM) and alumina in the cement binder of concrete.
This allows lightweight concrete (1600 kg/m3) to store three times as much energy (2.72 kWh/m3/ºC) as normal concrete (0,95 kWh/m3/ºC). The PCMs contribute in the storage capacity and the alumina increases the conductivity with 0.2 W/mK as such contributing in conducting the energy towards/from the PCMs.
The integration of compact ventilation and energy recovery within the prefab façade by using a total heat exchanger (THEX) with an innovative honeycomb separator design and a durable membrane improved for moisture regulation by nano-silica particles.
This allows significantly faster installation times and significant space gain for retrofitting as additional centralised HVAC installation on site is no longer needed. The THEX has an energy recovery efficiency of over 75% based on real demonstrator data of two 9 m2 facades and a validated total heat exchanger model. Also, this unique combination of optimized separator and membrane leads to 15% improved energy recovery and improvement of indoor quality compared to traditional HVAC systems.
Project Context and Objectives:
Project context
Problem
For the construction sector, energy efficient refurbishment is absolutely crucial in reaching the EU 2050 goals considering the fact that about half of the existing building stock in 2012 will still be operational in 2050 and approximately 85% of the dwellings were built before 1990 with poor insulation (R ~ 1.6 m2K/W). Ensuring a high quality indoor comfort is largely responsible for the energy consumption of buildings, on which the envelope, separating indoor from outdoor, has a major impact. Therefore the focus of refurbishment should lie on using the envelope (façade and roofing) to improve indoor environment at reduced energy consumption. Current retrofitting solutions to upgrade the envelope are mainly aimed at drastically increasing the insulation (R values > 3 m2K/W). Unfortunately, this requires thick insulation packages, airtight construction and consequently, additional ventilation and heat recovery systems to keep indoor comfort and air quality at the desired levels. As a result, housing corporations and owners are faced with time consuming and expensive refurbishment related to complex installations, while end users experience discomfort related to reduced space, over-heating and poor ventilation and may still have high energy bills related to additional ventilation and heat recovery systems. As a consequence, full replacement of facades (deep retrofitting) is not often considered in refurbishments. A major market potential therefore exists for construction companies and building material producers if they obtain a cost-efficient, easy and quick to install solution for building envelopes, keeping thickness and additional ventilation installations to an absolute minimum while achieving optimal indoor comfort at significant reduced energy consumption.
ADAPTIWALL breakthrough
ADAPTIWALL aims to tackle the above challenge by developing a climate adaptive multi-functional lightweight prefab panel suitable for cost-efficient, rapid and energy efficient retrofitting of facades (this project) and eventually also suitable for roofing, inner walls or entirely new buildings. For the first time, climate adaptive building components will be combined into a lightweight prefab panel in order to
(1) reduce heating and cooling demands with over 50% compared to current highly insulating solutions,
(2) recover energy from ventilated air at an efficiency of over 75% within the façade and as such reduce and eventually eliminate centralized auxiliary heat recovery and ventilation installations,
(3) reduce envelope thickness by at least 30% and weight by 50% to save space and reduce dead load
(4) fulfill the load bearing, fire safety and sound insulation functions in one single product.
The above targets will reduce energy costs and eliminate expensive and time-consuming onsite installations, making ADAPTIWALL a cost-efficient and quick retrofitting solution for envelopes.
ADAPTIWALL principle
The principle behind the breakthrough of ADAPTIWALL is the climate adaptive approach: being able to adapt energy transfer through the façade allows to take advantage of the outdoor conditions to regulate the indoor conditions at reduced energy consumption, provided there is the possibility of temporarily storing the outdoor heat (or cold) until it is needed on the inside. Therefore ADAPTIWALL combines in a prefab panel both adaptive insulation as well as a lightweight concrete buffer, the latter providing other functionalities of loadbearing, fire safety, sound insulation. Creating the high thermal storage capacity for lightweight concrete requires additives such as nano-silica, alumina and lightweight aggregate impregnated with PCMs. Additionally, the integration of ventilation and a compact total heat exchanger in the panel ensures energy recovery during ventilation and at the same time can regulate humidity and eliminate undesirable gases and dust without the need for additional separate installations. Achieving total heat exchange including humidity regulation while avoiding microbial growth requires membranes with nanostructured substrates.
The objectives and their status (rough indication how far from objective is given by % reached) are described in Table 1 in the attached report
Project Results:
4.1.3 Description of the main S&T results/foregrounds
4.1.3.1 Integrated adaptive panel design and simulation (WP2)
A three-stage approach was followed for the development and design of the integrated ADAPTIWALL panel starting with the simple design, via iterative design optimization to the detailed case design. The design in all these three stages was supported both by numerical simulations as well as by the outcome of lab-scale and prototype experiments.
The detailed design phase resulted in the design of two approximately 10 m2 demonstrator panels used for real-time performance measurements. The data from these measurements was used to validate the numerical simulation models used. The validated model was then used to verify the ADAPTIWAL energy savings ambition for different climates.
Simple design
First numerical simulations provided input and/or boundary conditions for the developments in the material work packages adaptive insulation, lightweight load bearing buffer and THEX. These inputs concerned specific boundary conditions and/or optimizations for the individual adaptive materials, e.g. thermal and physical properties. Figure 1 (left) for example shows how there is an optimum in buffer thickness with regard to its potential to contribute to energy savings.
Figure 1 optimum in buffer thickness (left) and effectiveness of different cladding concepts (right)
Besides input for the individual material developments also on the level of the overall ADAPTIWALL concept input was provided based on the outcome of the simulations. Figure 1 (right) for example shows how the type of cladding strongly influences the ability of the ADAPTIWALL concept to contribute to energy savings; i.e. for gaining solar heat a glass cladding is essential. This learning was translated into different insulation concepts to be investigated in WP3 e.g. switchable, removable and conductive insulation. Different insulation concepts however do not only influence the effectiveness of harvesting solar heat. They also impose a different challenge to the exchange of the heat to the buffer.
Based on the simple design phase it was concluded how, with realistic / imaginable material properties, the ADAPTIWALL energy savings ambitions appeared feasible.
Iterative design optimization
The second phase in the design was the iterative design process where the ADAPTIWALL concept developed through the continuous interactions with the adaptive material components. This phase was supported by numerical simulations, design workshops and prototype testing.
Numerical simulations
The developments in the material work packages were iteratively supported by numerical simulations. This involved for example iterations between lab-scale tests for one of the adaptive components and the overall performance of ADAPTIWALL.
In this phase also the effect of ADAPTIWALL in different climates was added to the earlier simple design simulations. It was shown how the relative savings are highest for intermediate climates such as France and The Netherlands and how absolute savings are highest for more extreme climates.
Finally the simulations were used to derive a control strategy for the ADAPTIWALL concept. Switching of the concept depending on the outdoor conditions and indoor conditions and comfort demands was optimized. This involved the switching of the adaptive insulation in order to transmit energy from the outdoor environment via the buffer to the indoor environment in heating mode and vice versa in cooling mode.
Design workshops
To ensure an efficient integration of all 3 adaptive components into one ADAPTIWALL panel design workshops were held both separately as well as during several GA meetings. This resulted in a.o. things:
- Awareness amongst partners how developments in different work packages strongly interact. This did not only concern the material development work packages (WP3, 4 and 5) but also results from the life cycle assessment work package (WP7).
- Physical boundary conditions due to integration of components, for example the restriction to the buffer thickness caused by the decision to place the THEX in plane with the buffer.
- A design for the 4 prototypes to be tested at the ACCIONA demo park in Algete (Spain) including structural and physical boundary conditions.
Figure 2 lab-scale prototype design for thermal performance testing
- A design for a prototype for fire-safety testing.
Prototype testing
From the lab-scale prototype testing it was learned how the loading and unloading characteristics of the prototypes are comparable to the simulations performed earlier, which gave confidence the envisaged energy savings are feasible.
Furthermore the prototype testing provided input for further optimization of the (design of the) ADAPTIWALL concept. The main learning form the prototypes that affected the design of the ADAPTIWAL concept were:
- Seeing the unwanted heat leakages special attention should be paid to the reduction of thermal bridges at structural connections and the integrity of the surrounding insulation;
- The robustness of the collector plate should be improved in order to be able to handle and install the plate with more ease;
- For all installation components a designated installation area should be foreseen;
- A pump should be added to the thermally driven water-loop system to ensure better controllability and a more effective heat transfer from an to the buffer;
- Laminated glass should be used for the glass cladding to prevent the glass from falling in case of breaking under fire loads.
- To improve the effectiveness of heat transfer to the indoor environment a separate indoor radiator is placed in front of inner finishing layer.
Detailed case design
The final phase of the design process focussed on the demonstrator design and on the translation of this design into reference residential building designs for the Netherlands, Poland and France.
Demonstrator panel design
Based on the learnings from the Algete prototype measurements and given the specific PASSYS test-cells constraints and boundary condition the design for the two demonstrator panels was made.
Figure 3 demonstrator panel design (left) and installed demonstrator panels on PASSYS test cells (right)
The design resulted in a total thickness of the panel of 366 mm measuring from the inner plasterboard finishing to the outer glass cladding.
Residential reference building design
The specific design solutions applied in the demonstrator panels design were translated taking into the retrofit design for 3 locale reference residential building cases. This translation has taken into account the local structural, physical and aesthetic boundary conditions for retrofit design as well as local building practice.
Figure 4 Dutch residential building retrofit design with whole building (left) and detail of ground floor element (right)
To demonstrate aesthetical possibilities the translation of the design also include the design of different façade appearances for different local cases. Figure 5 and Figure 6 demonstrate some of the possibilities by showing the ‘before’ and ‘after’ ADAPTIWALL retrofit situation.
Figure 5 Before and after ADAPTIWALL retrofit (Dutch case)
Figure 6 Before and after ADAPTIWALL retrofit (French case)
Numerical model and energy savings validation
Real time monitoring data from the performance measurements on the two demonstrator panels was used to validate the numerical simulation models. The validation showed good accuracy of reproducing the experimental data by the numerical model.
The validated models were then used to validate the 50% additional energy savings of the ADAPTIWALL concept in comparison to state of the art static retrofit solutions. For different façade configurations and orientations the resulting energy demand is compared to the energy demand of a static reference case (R = 5 (m2.K/W)).
Figure 7 Energy demand for different ADAPTIWALL configurations
As is shown in the figure above for the French case the ADAPTIWALL energy savings ambitions are feasible at a total installed ADAPTIWALL (buffer/collector) area of 25% of the total façade (R1). The additional energy savings for all 3 reference cases vary, depending on the percentage of adaptive façade and/or façade orientation, are:
- French case 50% - 64%
- Dutch case 45% to 54%
- Polish case 43% to 51%
The validated model was furthermore used to investigate the control strategy. It was shown how different control set-points, simulating different inhabitant behaviour, does not influence the additional energy savings by more than 5% showing the robustness of the ADAPTIWALL concept and it’s control.
4.1.3.2 Adaptive insulation (WP3)
The ADAPTIVE INSULATION component of Adaptiwall has the aim of providing panels with switchable thermal insulation, including a regulation system linked to an integrated sensor/monitoring system. Such a panel should switch under the influence of certain triggers from a thermal conductive state to a thermal blocking state, and vice versa.
The best performing and feasible adaptive insulation panel concept fulfilling the energy savings and design demands was found to consist of a waterloop system shortcutting static insulation of which the energy transfer to and from the concrete buffer can be regulated in an adaptive manner by a small water circulator on each waterloop.
Based on the dynamic simulations that were performed within WP2 the required system design and its boundary conditions can be summarised as follows:
Figure 8: boundary conditions adaptive insulation development – (note, the buffer thickness is not at scale)
Identification of requirements for adaptive insulation panels
The main application and material requirements that have to be met in order to have a technically and economically viable adaptive insulation system are:
o Energy from solar radiation needs to be harvested in order to achieve the required savings and as such glass cladding is needed
o An adaptive insulation material with a total insulation target value between 0.12 and 5 m2K/W gives an energy savings of approximately 44-50% compared to the reference case of Rc =5.
o Inner insulation: Simulations have shown that the effect of high insulation values for the inner insulation with regard to energy use is limited. The maximum target inner insulation value of approximately 1.5 m2K/W seems sufficient.
o Switching time should be less than an hour - Depending on the way adaptability is achieved, maximum switching time may vary. While heating of the buffer is largely dependent on solar heat gains (radiation) it may be desirable to be able to switch between states quickly. For cooling switching time is not so critical, since it is dependent on the temperature difference. And outdoor temperature does not switch as quickly as solar radiation. For the inside insulation this rationale applies for both heating and cooling.
o Lifetime – Lifetime needs to be at least 20 years, preferably more. Servicing and/or (partial) replacement should be possible. Thermal and UV resistance –determine the lifetime of the final product. The materials used should be stable in the temperature range of -30°C and +100°C (temperatures reached behind glazing).
o Fire retardancy – All materials used should comply with EN 13501-1 - Fire classification of construction products and building elements
o Ecologically friendly – The final solution should not be harmful to human beings or other organisms.
o Low cost - ROI of 7-10 years for the whole ADAPTIWALL system.
Labscale testing of adaptive insulation panel concepts
The following adaptive insulation concepts were selected from applying the above demands and boundary conditions on a large set of brainstorm ideas.
The EPS spheres concept implies that the properties of the insulation layer can be switched by (partly) removing and storing the insulation material. EPS spheres have target declared thermal conductivity values of ca. 0,033 W/(m.K). As such, in the insulated state, thicknesses of 50 (inner layer) and 150 mm (outer layer) should result in R-declared values of 1,5 and 4,5 (m2.K)/W. In the conductive state the spheres will be (partly) removed and transported to a storage space (e.g. a flexitank), for instance in the crawl space or underground. The critical aspects that came out of the components tests were the low insulation value compared to the declared value, thermal instability, static charging and user acceptance for the EPS concept
The general idea of the shortcut-concept is to directly transport heat from the vertical plane (cladding) to the buffer by means of so-called shortcuts in the insulation layer. These shortcuts by-pass a static layer of insulation. The actual adaptive parts of this concept therefore are the shortcuts themselves which become an integral part of the insulation concept. The shortcuts that were considered first are heat pipes because of their high capacity to transfer heat. The critical aspect that came out of the component tests was the amount of aluminium needed for efficient heat transfer from the heat pipes to the buffer and therefore the cost.
An alternative thermosiphon system was developed for the shortcut concept by which flow is generated from density differences in the water created by temperature differences. Such a system is not vacuum and the expansion of the liquid needs to be taken up by an expansion vessel (similar in heating systems). Calculations have shown that temperature differences will be enough to ensure the water flow. Active control of the flow happens by valves that can interrupt flow and therefore heat transfer.
4.1.3.3 Lightweight concrete buffer
The main objective of the concrete design was to obtain a lightweight structural concrete with improved thermal properties. A lightweight concrete can be achieved using lightweight aggregates like expanded clay, perlite, vermiculite... but these aggregates introduce air in the concrete structure with a decrease of the thermal conductivity, the thermal mass and the mechanical strength.
To obtain a concrete with sufficient thermal and mechanical properties (Table 2) for the Adaptiwall ambitions, additives of different nature were used to achieve the specifications: nanomaterials and micromaterials to increase the thermal conductivity, organic and inorganic phase change materials to increase the thermal mass; porous aggregates to decrease the density and nanomaterials and chemical additives to improve consistency and workability.
Table 2: Required properties in de concrete
Properties Range Unit
Density 1500-1800 kg/m3
Strength 25-40 (C20/25) N/mm2
Young’s Modulus 22-25 kN/mm2
Thermal conductivity 1,5-2 W/mK
Energy storage capacity ≥20000 (at the useful T-range) kJ/m2
Fire Resistance EI 180 Classification
Durability Same as traditional concrete
Sound insulation Same as traditional concrete (**)
(**) depending on the use of the building
All the mechanisms used to achieve those properties are explained below.
LIGHTWEIGHT AGGREGATE
The use of lightweight aggregates is necessary to obtain a lightweight concrete but not all of them give structural properties to the final concrete.
Different aggregates of siliceous and clay origins were studied: perlite, expanded vermiculite, pumice, sepiolite, expanded clay (3-8, 0-4). The most promising were perlite and expanded clay 3-8 because their high porosity, but the mechanical tests (compressive strength) showed that expanded clay is the most appropriate.
The type of cement used was CEM I 52.5 to increase the strength.
PCMs in the LIGHTWEIGHT AGGREGATE
To increase the energy storage capacity of the concrete, phase change materials (PCM) are incorporated in lightweight aggregates by means of vacuum impregnation so that the PCMs can enter the micropores of the aggregate.
Different types of phase change materials with melting points between 15-30 ºC have been studied to investigate the thermal behaviour. The results obtained with organic parafine PCM are the most promising, meaning aggregates were obtained with 40% - 50 % of PCM inside the pores. This means a potential increase in heat storage capacity between 50-80 kJ/kg (depending on the PCM used).
The durability of the impregnated aggregates was tested inside an alkaline solution (pH 11) and with multiple freezing-melting cycles. The results showed no degradation of the material.
Organic PCMs and lightweight aggregates have low thermal conductivity. In order to improve this, impregnation tests with the addition of carbon nanofibers were carried out (1% and 2 %) trying to increase thermal conductivity of the aggregates but no significant effect was observed: neither a decrease in the temperature melting range nor an increase in the total latent heat. Considering this result, the improvement of the final thermal conductivity behaviour of the concrete should be focussed on the binder and concrete formulation.
ALUMINA IN THE BINDER
Different binder mixtures have been studied to achieve an optimization of the thermal conductivity of the final concrete. An improved thermal conductivity leads to faster travel times of the energy to and from the aggregates which are the main storage component of the concrete (including lightweight aggregate impregnated with PCMs). In general, there is a linear relationship between density and conductivity of concrete and most conductivity increasing additives have a high density. However, because of the lightweight objective for Adaptiwall, we are looking for additives that increase conductivity without increasing the density. Three types of cements (CEM I, CEM II, CEM III), different W/C ratios, two types of sand (quartzite and limestone) and three types of additives (Al2O3, SiC, BN, steel fibres, carbon fibres) were used to produce specimens and perform thermal conductivity analysis.
The results show that the use of CEM I is the more appropriate (for the mechanical properties) with the lower rate W/C and the use of quartzite sand and the substitution of part of the cement (20%) with alumina increases considerably the thermal conductivity (>25%) without increasing the density (Fig 9).
Figure 9 : Thermal conductivity of mortar with different formulation/additives
CONCRETE DESIGN
The concrete mix was optimized using all the elements selected in the previous steps: quartzite sand, cement type I, expanded clay, organic PCM and alumina.
The main challenge was to find an optimum between lightweight aggregate and PCM amounts and rheological and mechanical properties. More specifically self-compacting properties were needed for easily the mould compartimentalised by both rebars as well as copper piping. Nanosilica additives were needed and a 50% gravel and sand aggregate replacement with lightweight PCM aggregate was the maximum possible whilst maintaining the necessary mechanical properties.
A summary of the concrete characteristics is shown in the following table:
Table 3: Concrete characterization
THERMAL STORAGE CAPACITY
Different thermal tests were carried out to the concrete to analyse the thermal behaviour of some concrete mixes. A laboratory system with thermocouples and heat flux sensors was used as described in Deliverable 4.3. The collected data is used to calculate the amount of energy absorbed by the samples during the test for changing the concrete temperature. The differences between the heat flux that enters and exits the sample as well the temperature gradient obtained during the same time span, are used to calculate the thermal storage capacity of the sample. Figure 10 shows the temperatures changes in the concrete surfaces subjected to this test.
Figure 10: Temperature evolution in different concrete mixes surfaces
Cyclic tests to simulate the temperature changes during Day-Night were made too and different parameters as maximum temperature differences between both concrete sides and the buffering capacity were calculated. Some of these results are in Table 4 and Table 5.
Table 4: Thermal parameters obtained (* Apparent values)
ΔT peak to peak (ºC) ΔT max (ºC) Δt HF (min) Δt peak to peak (min) Heating Delay (min) TES (kWh/m2/ºC) *
Reference 4,24 4,82 23,80 32,00 125,00 0,94
Adaptiwall concrete 2,27 5,83 72,57 56,43 124,43 2,72
LWC 0,55
Table 5: Buffering capacity : Decrement factor calculation.
Decrement Delay
Cold side (ºC) Hot side (ºC) Decrement Factor*
Traditional concrete (10cm) 10,35 14,35 0,69
Adaptiwall concrete (10 cm) 10,15 12,35 0,43
*The higher the decrement factor, the lower the buffering capacity.
Figure 11: Cyclic test of Adaptiwall concrete
CONCLUSION
A lightweight concrete with PCMs in the aggregate and alumina additives in the binder resulted in an increased energy storage capacity of three times (2.72 kWh/m3/ºC) that of normal concrete (0,95 kWh/m3/ºC). Furthermore, the study of the thermal performance of the concrete shows that the use of PCM increases the thermal energy storage capacity and the ability of keeping the temperature within a certain range. This effect avoids quick heating or cooling of the concrete, which reduces the risk for thermal cracking and prolongs the period during which the buffer is able to cool or heat the indoor room.
Compared to normal concrete, a density reduction 32% has been achieved in a lightweight concrete with structural properties of C20/25. Further reduction of weight implies a reduction of energy storage capacity to values lower than those predicted by the simulations to be necessary for heating and cooling objectives. As the energy reduction objectives are met as shown by demonstrator and simulations, for some climates up to 65%, there is room for lower concrete storage capacity and thus total panel weight reduction by density reduction (including more lightweight aggregate) or thickness reduction of the concrete. However, for the design of the 1 m2 prototypes and the demonstrator, it was decided to keep the buffer thickness of both the Adaptiwall concrete and the traditional concrete exactly the same, following the thickness of the THEX casing, namely 16 cm. Keeping the thickness of the concrete and the THEX which comes next to it the same, they can lie within one plane and insulation panels can surround the total assembly in a more robust and easy way.
4.1.3.4 Adaptive insulation-concrete buffer combination: 1 m2 prototypes
After the selection of the final adaptive insulation concept (4.1.3.2) and concrete design (4.1.3.3) 4 lab scale prototypes of the ADAPTIWALL panel were built at the Demo Park of ACCIONA at Algete, in Spain. Purpose of the prototype measurements was to demonstrate the ability of the integrated system to harvest solar energy, store this in the buffer and transmit it (on demand) to the indoor environment.
The construction of the prototypes took place in September and October 2015 and measurements were started in November 2015 and are finished in June 2016.
Different prototypes were produced for the thermal performance study of the panels at the Algete demopark in Madrid and othe for fire resistance test.
For the thermal study, the final decision of the buffer design for the prototypes was 4 concrete buffers with three different natures:
1- Reference: Lightweight (LWC) concrete → 1500 kg/m3
2- Modular: LW concrete (to compare different insulations and switching systems) → 1500 kg/m3
3- Adaptiwall 1: LW concrete with PCM impregnated in aggregates (and alumina)→ 1600 kg/m3
4- Adaptiwall 2:Traditional concrete with PCM in containers→2300 kg/m3
The design and production of the concrete buffer was a complicated task. Due to the fact the concrete buffer is the structural part of the panel, numerous of anchors had to be incorporated inside of the concrete as well as the internal part of the thermosiphon (copper pipes) had to be casted in the concrete.
Figure 12: Piping, anchors and casings installation and sensors placed.
After the internal structure installation, 100 L of concrete was poured and after 28 days of curing, the four panels were installed at the demonstration park.
Figure 13: The 4 concrete panels installed at the demo park.
The outside collector plate (Figure 14) and inside heat exchanging plate (Figure 15) are shown below.
Figure 14: Outside collector
Figure 15: Inside heat exchange / transfer plate
Harvesting-storage potential
The 1m2 prototype measurements successfully demonstrated the operability of the system to harvest solar energy and store it in the buffer. Valves were controlled by actuators to start or stop the thermosyphon heat exchange when necessary. Figure 16 shows the reaction time of the system to the opening of the valves. With the appearance of solar radiation, the temperature in the outside water loop increases. The difference between temperature values at the top (orange) and bottom (yellow) of the water loop corresponds to the increase of the buffer’s temperature (purple). It demonstrates that the targeted heat conduction between the casted pipelines and the concrete buffer, which results heat storage in the concrete, effectively takes place as is shown in Figure 16.
Figure 16: Temperature profiles in an ADAPTIWALL lab-scale prototype (No 2)
Figure 17: Temperature profiles in an ADAPTIWALL prototype (No 2)
In Figure 17 the capacity of the system to heat up the concrete is demonstrated. This was the main objective of the adaptive insulation system: shortcut the static insulation when needed to heat up the concrete buffer behind it when solar radiation is available and heat is needed. Though an effective loading of the buffer was demonstrated, some unwanted heat leakage out of the buffer was found indicating that for the demonstrator panels more attention should be paid to the thermal insulation of the buffer; e.g. the detailing of structural fixings.
The second functionality of the adaptive insulation was to transmit the stored heat from the concrete buffer (yellow line in Figure 18) to the inside air (green line in Figure 18) to contribute to decrease the indoor heating demand. This function is presented in Figure 18.
Figure 18 Effect of buffer loading on room temperature variation: heat transmission by adaptive insulation system
From the prototype measurements it can be concluded that thermosiphon waterloop system system is able to fulfill the function of the Adaptiwall panel requirements. It enables an effective harvesting of solar energy through the outer collector, transmit this energy to the buffer and store it in the buffer. From the buffer the inside waterloop transmits energy to the room ambient air.
Mechanical tests prototypes
We may conclude that the measured mechanical properties of the ADAPTIWALL buffer fulfill the requirements for the structural design of panel which was based on a regular C20/25 concrete standard. Even more satisfying, the use of PCM lightweight buffer exceeds both the characteristic compressive strength (by a 7%), the axial tensile strength of the lightweight LC20/22 standard (in a 30%) and performs a 10% better than C20/25 concrete on the flexural stress test.
Table 6: Mechanical properties comparison of standard classification and test results
CONCRETE SAMPLES Compressive Stregth (fck,cube) Bending tensile strength (fctm) Density
(ρ) Classification (EN206-1)
Lightweight concrete (test) 24.2 MPa 1.42 MPa 1510 kg/m3 LC20/22
ADAPTIWALL Lightweight concrete +PCM 23.1 MPa 2.11 MPa 1630 kg/m3 LC20/22
Traditional concrete (standard values C20/25 *) 25 MPa 2.6 MPa 2400 kg/m3 C20/25
Lightweight concrete (standard values LC20/22 *) 22 MPa 1.97 MPa 1401-1600 kg/m3 LC20/22
*Eurocode 2 data and calculations
Fire test prototype
The standard followed for the fire test is UNE EN 13823:2012 for which a specific test specimen is needed. A corner of 1,5 m high and 20 cm of thickness was designed for the whole panel. Due to the limitation of the thickness, only half of the panel could be tested and only the external face of the panel was included (glass+ external thermosiphon+insulation+10 cm of concrete).
Figure 19: Formwork and fire test prototype
Recommendations demonstrator
Based on the 1m2 prototype monitoring campaign in Algete and the mechanical and fire testing, the following recommendations are made for Adaptiwall which are included in the 10 m2 demonstrator.
Table 7: final design recommendations
Total heat exchanger
The objective of this work was to develop a compact Energy Recovery Ventilation (ERV) system panel component that fits within the Adaptiwall prefab panel, allowing heat recovery between fresh and exhaust air with an efficiency of over 75% and humidity control during ventilation. This development can be divided into three subtasks:
As a first step, specifications and requirements have been set for the realization of a total heat exchanger (THEX) integrated within the size of the ADAPTIWALL panel. A numerical model were set up, so several parametric studies were performed in order to:
Define technologies and dimensions of separator
Define membrane properties to target, in order to reach latent efficiency as defined in the specifications, as well as to determine a baseline membrane to be improved
Define arrangement of system in the wall
Define the THEX modulus for the TRNSYS dynamic simulation (done in WP2)
The second step of the development concerned the definition of the available place to integrate the THEX module to the ADAPTIWALL demo panels.
The third step was the post treatment study of selected membranes of THEX.
The relevant points to retain from the first step are the following:
In general it can be said that the mass transfer area available for each kind of separator and the ability to develop large convection coefficients, thermal and mass transfer, play a combined and a major role in the moisture transfer performance.
The separator “Nidab Large” is clearly the one which brings the best sensible performances. However, a potential pressure drop generation, which could surely be a bit larger than the conventional separators, has to be taken into. But, as the Reynolds number in the channel will be very low in the demonstration configuration (<200), the extra pressure drops, comparing to standard separators will not be critical indeed.
Whereas the identified baseline membrane Pebax1657 is cheaper and more durable, its moisture transfer performances are clearly not as good as the ones of the commercial microporous reference membrane of the market. Mass efficiency is between 5 and 15% lower, depending on the average humidity condition at the membrane, but the moisture transfer is well effective and is improved in step 2 and 3.
The graph below shows evolution of Nusselt number as function of Reynolds number for all the membrane separators tested. Nusselt number allows qualifying the ability of technology to promote convection in the flux and at the surface of the membrane. Indeed “Nidab Large” separator brings strong advantage in comparison with other configuration of channel.
The relevant points to retain from step two (potential membrane’s formulation improvement) are the following:
The dispersion of nanoparticles of silica (170m²/g) in a blown-extruded membrane of 33μm of thickness allows a net improvement of moisture transfer, comparing to the Pebax MH1657 baseline membrane. Experimental apparent diffusion coefficient as function of relative humidity at the membrane is slightly better than the one found for the baseline membrane. In terms of performance, the latent efficiency is almost at the level of the commercial membrane, reference of the market. These results open furthermore a lot of optimization perspectives, especially concerning the multiple parametric configuration, like the concentration, the process to disperse nanoparticles in the compound, or other hydrophilic nanoparticles.
A numerical comparison (calibrated with experimental results) of the state of the art (SoA) configuration (commercial membrane and conventional separator) with the ADAPTIWALL solution (improved baseline membrane with “Nidab large” separator), has demonstrated that the ADAPTIWALL solution allows an increase of sensible and latent performances between 10% and 20%.
The initial objective to achieve a global enthalpy efficiency of 75% is anticipated to be reached based on the results of lab scale experiments and with the help of numerical model (in summer and winter condition) and the demonstrator experimental campaign has to validate also this result.
The figure below illustrates these numerical projections.
The relevant points to retain from step three (potential membrane improvement by a post treatment) are the following ones:
Experimental results show that embossing and/or application of a hydrophilic coating, bring improvements for some membranes and conditions, but did not seem to bring significantly strong advantages on the moisture mass transfer rate in the membrane in general but are too dependent on the relative humidity at the membrane. It was surprising that imprinting did not improve the performance of the moisture transport, as it was observed with numerical modeling with the kind of structure studied.
Unfortunately, the silica modified membrane of 33µm thickness was not included in the post treatment research as the results of the efficiency of this membrane was not known at the time of the post treatment experiments were performed and the PVA modified material seemed the better choice at that time. As no post treated membranes are available with properties better than the 33µm silica modified membrane, no post treated membrane will be used for the membrane of demonstrator.
THEX system arrangement in the panel
This task had been treated in collaboration with the other work packages (WP2 and WP6) and deals especially with the following detailed points:
Mechanical assembling aspects (integration in Adaptiwall panel)
Technical assembling aspects (fan, frame, casing, separator, filter, maintenance access...)
Control and regulation aspects (by-pass and condensation management...)
Piping and instrumentation aspects (sensors, actioner, pipe connection...)
CFD flow distribution studies are done, pressure drop of heat exchanger and filter are being calibrated, with a focus on the pressure drop of the system (specifically due to the by-pass) and also on the homogeneity of the flow rate at the nose of channels in the admission area. Design of air flux distribution of THEX has been optimized in this way. The figures below illustrate the assembling of the THEX prototype as a standalone appliance. Two instrumented prototypes were manufactured.
Firstly, the casing of the system with the top cover is described. Air tightness has been studied especially.
Secondly, frame and separator are assembled together by adhesive strip.
The stacking of the plates of each pass of fluid (a frame plus a separator), including membrane intercalation between each plate, is achieved. Membrane is set in a one way mode, by wrapping alternatively one side of each plate, double face adhesive strip is used to fix membrane on the frame and assure air tightness of assemblage.
By-pass system is configured directly in the casing. The calibration of the bypass rate is planned on the month of July. A specific algorithm is setup in the way to assure zero condensation occurrences in the THEX while the energy saving is optimized. This algorithm allows to determine a ratio fresh air bypass in function of two only parameter (fresh air and exhaust air temperatures inlets).
Demonstration total Adaptiwall
The aim of demonstration activities is to integrate all Adaptiwall elements, adaptive insulation, buffer and THEX, into two demonstration panels and asses the thermal performance of the multi-functional system through monitoring. First task focussed on the integration and manufacturing of the two panels to be installed at INCAS experimental platform of CEA INES. The following parts of the process were handled within the project:
Manufacturing of sub-components (e.g. lightweight buffer) and supplying all elements to CEA,
Drafting a handbook for the assembly process,
Security procedures of lifting
Reception on the INES platform.
Supplying
The concrete buffer production was covered by ISODAL who was responsible for casting and transporting the buffer to CEA. All the necessary elements were supplied to Isodal, e.g. the PCM impregnated aggregates by ACCIONA, the shortcut adaptive insulation (water loops) by CEA and mechanical resistance calculations and rebar positioning by Snijders. All supplementary elements such as Window, glass cladding, timber frame, auxiliary elements were delivered by FASADA directly to CEA for final assembly in the two demonstrator panels. Originally the assembly of the demonstrator panels was scheduled to take place in Poland at Fasada. However it was decided that, mainly from a pragmatic point of view, not to ship all Adaptiwall elements back and forth all over Europe. Assembly and manufacturing directly at CEA in France was found to be more efficient. This change resulted in an unforeseen a delay of the installation process which resulted in an reduction of available measurement period. Consequently deep winter conditions were not addressed, nevertheless heating demand reduction have been assessed according to the initial work plan enabling the validation of the overall ADAPTIWALL energy savings ambitions.
For the assembly process a handbook was edited by Fasada (supported by Snijders) describing the assembly / manufacturing of the panels and the actual installation of the panels on the PASSYS cells step by step. Based on the experience with the manufacturing of the prototypes special attention is paid to the division of activities and/or responsibilities during the process.
Security procedure of lifting
Lifting and handling heavy façade elements requires some extra security check within CEA’s experimental activities. Potential risks of shared responsibilities was studied between actors of WP6 and discussed with the CEA INES security-officer intensively. Detailed process was reported in deliverables D6.1 and D6.2.
Reception on the INES platform
INCAS platform dispose 4 PASSYS test cells from whom 2 were used for ADAPTIWALL for demonstration activities. In order to be able to assemble all elements to the PASSYS test cells, a special technical area has been blocked around the work zone. Finalized demonstrator panels are presented in Figure 20.
Figure 20: Finalised ADAPTIWALL panels at INES
The next step concerned the performance testing of the demonstration façades. This task covers measurement activities on two demonstration façades installed at INCAS experimental platform at CEA INES. Three main activity were distinguished:
Optimisation
Instrumentation
Data recording and analysis.
Optimization:
The composition of the ADAPTIWALL demonstrator panels is very similar to the lab scale prototypes installed at Algete, Spain in 2015 (cf. WP2 activities). The differences are due to the optimisation process engaged since the Spanish experimental campaign and the efforts to get the closest to the real case situation. Main differences are:
Water loops are simplified, no thermosiphon functioning but pump controlled water flow is set up. The importance of the water pumps is that the heat storage and the heat discharge can be better controlled and optimised by controlling the operation and the flow rate of the outside and the inside pumps. Hence, more energy saving potential can be achieved compared to the thermosiphon system (no pumps) by considering this optimisation even though the pumps will consume some amount of electrical energy.
Less actuator is involved;
Two demonstrators were installed: PASSYS4 without PCM in concrete buffer, PASSYS 3 with PCM in concrete buffer (see Figure 20).
Window was added in each demonstrator to represent real dwellings.
Roller shutter was installed in front of the window and of solar absorber (overheating protection supposed not to be used).
Total heat exchanger (THEX) was added in each demonstrator in order to verify its performance (that was previously measured at lab scale) under real conditions.
Technical area was included in each wall panel to show the space that this area will occupy in real future installations
Inside radiator is included in the inside water loop (brand Radson, type Vertical) that represents the water-to-air heat exchanger between the buffer system and the inside space.
Instrumentation:
The prototypes (presented in Figure 20) are prefabricated and composed by the three main ADAPTIWALL components, namely: the lightweight concrete buffer, the shortcut concept adaptive heat insulation and the THEX (total heat exchanger air handling unit). A standard window and a glass cladding in front of the solar thermal collector complete the final version of demonstrators.
As a first step, instrumentation had been defined and casted sensors delivered to ISODAL during the manufacturing process of the concrete buffer. A special support was developed to fix thermocouples to the cooper pipeline in order to keep sensors in place during the casting process. Surface sensors were installed directly at INES in and on the demonstrators as shown in Figure 21 and Figure 22.
Figure 21 Sensors placed on buffer surface
Figure 22 Sensors installed in THEX air ducts
Data recording and analysis:
Global measured data with scenarios are presented in Figure 23 and Figure 24.
Figure 23 Measurement scenarios N°1 to N°6 in PASSYS 3
Figure 24 Measurement scenarios N°7 to N°14 in PASSYS 3
The working principle of the system: heat transmission from outside to the buffer, energy storage in the buffer, and heat transmission from buffer to the inside was demonstrated as shown in Figure 25. This is the normal functioning of the ADAPTIWALL concept during heating period or during mid-season when indoor climate requires additional heating, which in the case of ADAPTIWALL is provided by harvesting solar energy. The cooling behaviour was much more complicated to demonstrate. Here we conclude that added devices are required to achieve the desired cooling performance objectives: shading in front of the window to limit solar gains and rolling shutter in front of the outside solar collector during the day to avoid solar energy harvesting. With this latter we limit the warm up of the collector and keep the temperature difference between the buffer and the plate optimal to be able to discharge the stored heat from the buffer to the outside during the cooler (night) periods.
Figure 25 Experimental data
Measured data served to calibrate and validate WP2 numerical models. With these calibrated models the ADAPTIWALL energy saving objectives were validated and are presented in 4.1.3.1.
THEX results
During demonstration activities, one THEX was integrated in each ADAPTIWALL demonstrator panel. Special scenarios as well as background functioning were tested during measurements. Main achievements with efficiency measurement are presented below.
The performance indicators of the THEX panel are defined by the sensible, latent (moisture), and enthalpy effectiveness as shown in Figure 26. It is sure that these indicators are calculated when the by-pass is closed. They are also dependent on the working conditions; i.e. the temperature and humidity ratio at the inlets.
For the temperature effectiveness, η_s is in the range of 0.7 to 0.8. At night time, we obtain higher values for η_s than that during daytime due to the higher temperature gradient between the inlets. During all the considered period, η_s decreases to low values (0.5-0.6) during daytime of the last day. The reason is the very low temperature difference between the inlets. For the moisture effectiveness, η_l is in the range of 0.5 to 0.7. η_l shows very high values, more than 0.7 for very high absolute humidity differences between the inlets. For lower differences, η_l is around 0.55-0.6. For scenario three, when the moisture generation is turned OFF, we obtain a high dispersion in the moisture effectiveness due to the very low differences (less than 0.5g/kg) between the two air flow inlet absolute humidity. Accordingly, the effectiveness calculation during this scenario is not accurate. The enthalpy effectiveness is between 0.6 and 0.7. Its behaviour follows the behaviour of the temperature effectiveness.
Figure 26: The sensible, latent, and enthalpy effectiveness of the heat exchanger
From the demonstration activities we concluded that:
The sensible effectiveness is more than 77% when the temperature difference between the inlet fresh air and the inlet exhaust air is more than 8°C. This temperature difference is usually the case when considering winter and/or summer conditions depending on the climate. The sensible effectiveness decreases with the decrease in the inlet temperature difference
The latent effectiveness is 60% - 70% when the humidity ratio difference between the inlet fresh air and the inlet exhaust air is more than 5g/kg. The latent effectiveness decreases with the decrease in the inlet temperature difference.
The total (enthalpy) efficiency is also a little bit lower than that found in the lab-scale measurement (around 3% lower) at 70 %.
For highly insulated buildings, the heating demand due to ventilation requirements represents around 30-40% of the total heating demand of the building. Therefore, the total heat exchanger solution integrated into the façade as a decentralised ventilation system can reduce up to 75-80% the energy consumption due to ventilation requirements. In addition, thermal comfort is enhanced due to the high humidity recovery potential of the system.
Potential Impact:
4.1.4.1 Environmental and economic impact
Here, a summary is presented of the LCA, LCC and HHRA assessment of the materials, developed panel and refurbishment strategies carried out for the Adaptiwall Panel. The overall conclusions of this study are discussed below, for figures accompanying these conclusions is referred to Deliverable D7.1.
• GWP results in the production stage of the three alternative materials (EPS Spheres, Heat pipe, and Thermosiphon system) present that the Thermosiphon alternative is the most favorable alternative in terms of the environmental aspect.
• The GWP simulation results in the production stage of the four concrete alternatives: typical lightweight concrete, lightweight concrete with PCM, lightweight concrete with PCM and alumina and concrete, show that two lightweight concrete alternatives with PCM have just 2% of difference in emission of CO2 to atmosphere. Contrary to typical lightweight concrete studied in the chapter 6.3.1 this difference between typical lightweight concrete and lightweight concrete with PCM and with PCM and alumina is about 19-21% , but it is much smaller than in the case of concrete and typical lightweight concrete (approx. 31%). It is because there is less cement in concrete than in a typical lightweight concrete. The difference in performance between regular lightweight concrete and lightweight concrete with PCM impregnated aggregates is currently being measured in the WP6 demonstrator. Preliminary results show that the difference in terms of energy savings lies around 60%. This means that pay-back time is 14 years, for an additional investment for a typical Dutch reference case of 3600 €, lies around. Therefore this option was selected for the ADAPTIWALL studies.
• The presented economic results in the production stage of the three alternatives (EPS Spheres, Heat pipe, and Thermosiphon system) show that the Thermosiphon is the most favorable alternative in terms of the economic aspect. This confirmed earlier environmental studies (chapter 6.2) that this material should be taken into account in further ADAPTIWALL panel analysis.
• From an LCA point of view is ADAPTIWALL retrofit is more preferable than state-of-the-art retrofits (Rc = 5 m2K/W) only in the construction and end of life stages. For the total LCA, Adaptiwall has a higher total CO2 footprint (around 150-200 kg CO2/m2 façade) than state-of-the-art retrofitting (around 100-150 kg CO2/m2 façade). However, it should be emphasised that comparison is made with a state-of-the-art retrofit of already Rc = 5 m2K/W. If comparison is made with the total CO2 impact of an average non-retrofitted reference house, which is at least a few 1000 kg CO2/m2 façade (see for example the reference house of EU funded project EmInInn (2011-2015)), the LCA impact difference between current state-of-the-art retrofitting and Adaptiwall retrofitting is not very significant. Together with this, it should be noted that an even more honest case comparison both for LCA and LCC should include a deep retrofit, also replacing the inner wall in the state-of-the-art retrofit as is done in the Adaptiwall retrofit because that increases the material use and comfort in the reference to levels more comparable to Adaptiwall.
• In general, the above observations are related to the fact that there is a trade-off between adding technologies for energy reduction to buildings versus extra material use for these materials. This is even seen already in the state-of-the-art reference in which the CO2 impact in the use stage is only counting for 6% of the total impact in the use stage which is mainly related to material replacement. One of the conclusions of the EU funded project EmInInn (2011-2015) which developed environmental macro indicators for innovation, is for example that stimulation is needed for sustainable innovations in the built environment, which do not steer so much towards reducing energy consumption (e.g. insulation, eco-boilers) but replace the energy source, i.e. make use of renewable energy sources. If use is made of renewable sources, the rebound effect of higher energy impact related to energy needed for cooling and comfort by extra installations is less of a problem for environmental impact. This is exactly what Adaptiwall is doing, energy harvesting is included in the façade.
• Further development of Adaptiwall including optimisations for the concrete panel: thinner, less or no PCM (depending on proven energy savings in future), optimization rebars etc will further bring the LCA and LCC of Adaptiwall at similar levels as for state-of-the-art retrofits (Rc = 5 )
• In all cases, no health risks are expected due to indoor domestic exposure as a consequence of the materials installed during the renovation, since all exposures remain well below the derived health limit values, if available. There is overlap in emitted substances between traditional and ADAPTIWALL retrofitting, although ADAPTIWALL potentially emits more different substances. From the HHRA point of view ADAPTIWALL panel is not classified as a dangerous, it has the same impact as traditional retrofit panel.
• Dust and quartz emission do not cause major health concerns. However, it is recommended to use a respiratory protection that sufficiently reduce the risk of quartz exposure
• As described in previous paragraphs, it is foreseen a reduction from 430€/m2 of initially calculated material cost for ADAPTIWALL retrofit, to an average in between 354-371 €/m2 depending on where the upscaling of manufacturing will take place.
• It is also predicted and estimated economic optimization in overall investment costs from a total of 391 to 591 €/m2 depending on where the final production stage and building retrofitting is going to take place. This value can compete with for example state-of-the-art deep retrofitting in which the total façade is replaced.
• Because of the relatively high initial costs of Adaptiwall and the different TRL levels of its components, the implementations strategy is set up around individual Adaptiwall components for early exploitation towards exploitation of the full Adaptiwall in later stages.
4.1.4.2 Implementation and commercial exploitation strategy strategy
In general it was shown in the LCC study that ADAPTIWALL is a highly competitive solution in comparison to current (near zero energy) deep retrofit solutions. One key distinguishing element is the fully prefabricated and integrated ventilation solution besides other competitive advantages such as:
- Better Indoor (cooling) comfort
- More efficient transport (due to weight reduction)
- Space savings
- Faster renovation time related to the use of decentralised heating/ventilation units.
Although the rate of deep retrofit is expected to grow, currently this type of renovation solution represents approximately 1.5 to 2% of current retrofit market. On the short term emphasis will be put on in the implementation of individual parts and/or technologies of the ADAPTIWALL concept. On the longer term the ADAPTIWALL concept as a whole will be implemented.
Below the exploitation strategy for the different exploitable results are further detailed.
Implementation strategy as a basis for commercial exploitation strategy (through producers and chains of subcomponents)
For all of the results, exploitation strategy in short, mid and long term perspective was analysed and developed. The list of updated key exploitable results is presented in Section B (table B2).
Results: 1 Smart thermal façade and 6 ADAPTIWALL panel
In short term perspective following sub-results are expected:
• 1/6a. Standardized small dimension (1-2m2) adaptive façade panels: In mid-September TNO will submit national research project with industrial partners in order to optimize adaptive façade panels.
• 1/6b. Simplified ADAPTIWALL façade panels: Optimization of the solution through the integration of “invisible solar collector” (for example TNO currently participates in other research project in this topic with AKZO). Promising exploitation route is to use standard roof collectors and in this way achieve freedom in choice of the cladding material. Currently this solution is discussed with Dutch prefabrication industry. Currently the ADAPTIWALL collector is optimized for intermediate EU climate, but has the intrinsic flexibility to anticipate to more extreme climates; e.g. an uncovered collector to optimize cooling efficiency for warm climates. Also currently an ADAPTIWALL panel holds a separate THEX unit and technical area, both separately accessible for installation and maintenance. Integration of both, preferably only one per panel, minimized and positioned behind the inner radiator seems favourable giving better occupant acceptance.
• 1/6c. Improved energy efficiency: The goal is to optimize the solutions in order to improve the use of stored heat in concrete buffer. Currently the temperature of the buffer is >25°C and it transmitted via radiator. However if the temperature would be between 20°C-25°C the transfer with the ventilation would be performed. In case of temperature in the buffer <20°C the heat can be a source for heat pump.
In Mid- term perspective:
• 1/6d. Adaptive insulation with normal lightweight concrete: Market introduction should be made through the pilot retrofits and implementation of ADAPTIWALL in real building. Important aspect is to optimize the collector and energy efficiency (better use of stored heat) for full ADAPTIWALL solution. Another aspect is the optimization of the design in order to achieve plug and play solutions. Currently CEA is investigating the patenting of the control system of ADAPTIWALL
In Mid and Long-term perspective
• 1/6e. Adaptive insulation with PCM concrete
Results: 2 Concrete formulation and 3 ADAPTI-buffer
In short and mid-term perspective following sub-results are expected:
• 2/3a. Lightweight buffer for floor/wall heating in low energy massive houses: PCM’s results in better energy efficiency due to a better energy storage capacity. However because of relatively high cost of PCMs, there is potential for use of standard concrete for a buffer. This option also will allows to achieve significant energy savings. Lightweight buffer (without PCMs) can be apply for floor heating in low energy massive houses (on-going discussion with manufacturer of prefab building components).
• 2/3b. Lightweight PCM impregnated buffer for floor/wall heating in low energy massive houses. In mid-term perspective lightweight buffer with PCMs for floor/wall heating can be applied
• New application of concrete with improved thermal conductivity: Increased thermal conductivity can contribute to control heat development during production (casting) of large (usually infrastructural) concrete structures, potentially even avoiding additional cooling. TNO is currently investigating the potential advantages in terms of sustainability, process optimization and costs amongst contractors in the Netherlands.
• 2/3c. Consultancy and development on PCM impregnation and application: Further development of PCMs impregnation process will be performed by Acciona. The applied PCM’s are optimized for intermediate EU climate. The potential to anticipate to more extreme climates can be investigated; e.g. PCM’s with low melting points (<200C) to optimize cooling efficiency for warm climates.
Results: 4. Non porous membrane / 5. THEX
In short and mid-term perspective following sub-results are expected:
• 4/5a. THEX in prefab retrofit panels with (patented) separator and conventional membrane: Part of market introduction should be done through pilot retrofits and implementation of ADAPTI-WALL in real building. Significant cost advantages of integrated auxiliary installations should to be exploited, especially in deep retrofit projects. CEA will check the possibility for next patent regarding a new method of bypass management for Energy Recovery Ventilation system
• 4/5b. THEX technology applied in / translated to traditional HRV: Efficiency of centralized state of the art systems lies in the order of 65% showing potential for application in centralized Heat Recovery Ventilation (HRV) systems . CEA is currently consulting manufacturers of HRV systems for potential development and installation in buildings (both new built and retrofit).
• 4/5c. THEX technology with improved nano (structured) membrane: Nano structuring of the membrane was discarded for practical reasons in current solution but has shown great potential. Therefore the second generation membrane will be developed by PROCHIMIR and CEA.
• New application of membrane technology: Further exploitation by PROCHIMIR (membrane developer) and application of membrane in different sectors: medical sector, food packages sector.
4.1.4.3 Dissemiation and exploitation within project
Partners of ADAPTIWALL project participated in almost 50 conferences and workshops, published 4 scientific papers, submitted one patent application no PCT/EP2015/071944 on Heat exchanger system with improved performance and improved compactness. The patent was submitted by CEA and consists of a specific arrangement of the Energy Recovery Ventilation system into the wall, which enable simultaneously, a better efficiency (due to an pseudo adiabatic peripheral behavior), a bypass function when it is necessary, a better flow distribution (no air short cut possible), and an improved compactness of the appliance. Currently CEA is interested in depositing of second patent about on a new method of bypass management for Energy Recovery Ventilation system.
During the project duration following dissemination tools were created:
see table in the attached report.
Several meetings with industry were undertaken in order to verify and analyse the market acceptance and short-term possibilities for the ADAPTIWALL system. First set of meetings were undertaken by the TNO and Snijders in the Netherlands. The concept of the ADAPTIWALL system was discussed with two manufacturers of prefabricated building components: IQ-woning and Hurks. Those stakeholders offer completely prefabricated standardized units for new construction and intend to develop renovation concepts. Second parts of the meetings took place in Poland, France and Spain:
- In Poland the concept was discussed by FASADA with the architect office IBJK architects), construction company (KB Doraco) and the City of Gdynia (which is a public stakeholder)
- In France a meeting with GA was undertaken by CAE. This company manufactures various components required for buildings, amongst them is the system NEWSKIN, which is an innovative, flexible, quick solution for building renovation.
- In Spain, Acciona had a meeting with the Spanish Institute of Cement and its Applications – IECA.
During the project timeframe several internal exploitation workshops were organized. During those workshops IPRs issues, market potential of each results and further exploitation activities were discussed.
Final ADAPTIWALL workshop was organized at month 41 during trade fairs BAU 2017, the German Leading Trade Fair for Architecture, Materials and Systems . The fairs were organised in Munich between 16 – 21th of January 2017. ADAPTIWALL and project REESEEPE, FASIDUR, ECO-BINDER, GELCLAD, QUANTUM, HOMESKIN, InDeWag and WALL-ACE under the umbrella of European Construction Technology Platform co-shared the exhibition booth and presented various solutions and technology for energy efficient retrofits that are developed under research projects funded by European Commission. The visitors of the booth had the opportunity to be informed about the working concept of ADAPTIWALL prefab system, received the publicity material about the project, saw the promotional video and small prototypes of selected components. Together with cluster projects ADAPTIWALL co-organised the workshop “From research to market, Innovative technologies and ICT solutions for energy efficiency” that was held on 19th of January, 2017.
Participation in BAU 2017 increased the visibility of the project to target audience and was a great opportunity for project partners to discuss with other exhibitors about potential collaboration and market uptake of ADAPTIWALL system.
Within the project timeframe exploitation strategy for individual exploitable results was developed. The strategy is presented in Chapter 4.1.4.2
List of Websites:
www.adaptiwall.eu