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Harvesting solar energy with multifunctional glass-polymer windows

Final Report Summary - HARWIN (Harvesting solar energy with multifunctional glass-polymer windows)

Executive Summary:
Very ambitious technical key objectives for new window concepts were defined by the EeB Smart Windows Program EeB.NMP.2012-5 in the Seventh Framework programme:

▪ Energy savings over live cycle up to 15%
▪ Weight reduction up to 50%
▪ Insulating window with 0,3 W/m²/K at VLT > 50%
The HarWin approach to fulfil these goals is based on material development for both: the window glazing and the frame.
Weight and energy demand reduction over the life cycle is achieved by selection of lightweight materials with low embodied energy and by simultaneous improvement of the mechanical and thermal as well as optical performance of these materials by utilization of most advanced strengthening methods for glazing and frame, and by reduction of thermal conductivity of polymer-glass composites.
Energy harvesting is based on use of Phase Change Materials (PCM) in the glazing as additional thermal mass and new glass with Luminescent Down Conversion (LDC) properties to increase the Visible Light Transmission (VLT).
With thin glass laminated panes reinforced with new polymer-glass composite materials performance figures of U-value (0.4 W/m²/K) and VLT (75%) comparable or even superior to existing triple glazing can be achieved at almost 50% lower weight.
The new extremely stiff and thermally insulating frame, based on polymer foam core-glass fiber reinforced polymer skin materials offers additional embodied energy savings due to weight reduction by a factor of 5-10 as compared to existing polymer/metal or metal frame.
In addition to development of new materials also simulation methods have been developed for the next generation of light weight windows, which due to their modular structure also enable extension of window functionality, like wavelength specific energy management, including wave length conversion with coatings but also with a new active luminescent glass and with PCM (phase changing materials).
A data base and a simulation tool which is including End of Life (EoL) recycle ability of materials were developed for LCEA analysis of HarWin windows. Furthermore, a HarWin window module for building performance simulation has been implemented into existing sophisticated building performance software (Virtual Environment, IES, UK). Extensive characterisation of optical and thermal properties of HarWin windows enabled the implementation of a data base for the new materials into a cost analysis tool, which is used to validate the cost saving potential of the new window materials.
The benefits of the light weight glazing and frame materials in terms of energy and cost savings and in particular for refurbishment of old buildings were clearly demonstrated. For energy harvesting with the help of PCM a thorough analysis of inorganic and organic materials has been accomplished, showing the superiority of organic materials for achievement of high light transmission. Even thin layers of PCM have proven to offer energy savings for cooling in certain climatic zones.
For harvesting the UV part of sun radiation for increased VLT a new Luminescent Down Conversion glass has been developed which converts UV radiation into visible range of wavelengths with almost 30% photonic efficiency.

Project Context and Objectives:
Work performed since the beginning of the project is divided into two areas: I. Material and component development for Smart Windows and 2. Development of simulation and LCEA methodology for windows to define energy savings over life cycle as well as added value and building constraints. The material and component development includes the following Workpackages: WP1, Material development for light weight glazing; WP 2 Added functionality for solar energy harvesting; WP3 Laminated composite glazing components with added functionality; WP 4 Light weight frame and glazing. The simulation and LCEA methodology development includes two Workpackages: WP 5 Modelling of glazing constraints, component performance and building integration; WP 6 LCEA of windows integrated in buildings. The following main results were achieved:
▪ Energy savings over live cycle up to 15% were reached and even exceeded. Based on experimental data obtained from HarWin Demonstrator glazing and frame energy savings over life cycle were shown to be achievable up to 25% of total energy for heating and cooling.
▪ The degree of energy consumption reduction depends upon building type: a detached single family house versus an office building or apartment, and the climate zone as well as the character of the building, e.g. new versus refurbished old were included in different building simulations.
▪ In addition energy saving is achieved by reduction of amount of materials used as well as by use of materials with high recycle potential. Quantitative results from a new LCEA tool developed in HarWin were used to guide the material and component development. Life Cycle Inventory datasets for the applied materials were established.
▪ Weight reduction of almost 50% (triple glazing) is achieved with new laminated and particle reinforced thin glass panes and new light weight frame. A weight reduction of 47% is achieved for triple glazing with specialized laminated glass panes. Compared with state of art triple glazing thin glass particle reinforced laminated panes have the capability for the required mechanical strength. In addition a light weight frame has been developed which would further reduce the overall weight of multiple glazing windows.
▪ Insulating window with 0,3 W/m²/K at VLT >50%: The required U value reduction cannot be achieved with single laminated panes with optimized reinforcing particle amount and geometry but based on thin laminated glass panes reinforced with such polymer-glass composite interlayers multiple glazing was developed with UG value of 0.4 W/m²K at VLT of 75%.
▪ The weight reduction potential of the newly developed frame has not been added to the overall weight reduction figures because of the low TRL of the frame manufacturing and testing. From LCEA analysis the high innovation potential of such light weight frame materials has been clearly shown, in particular if strengthening is done with the help of Basalt Glass fibers developed in HarWin.
The general technical features of the different Demonstrator variants are shown in Figure 1. and performance figures are shown in Table 1.
LCA, LCC, Building simulation (WP 1-6). The LCA tool developed in HarWin enables for the first time a quantitative analysis of contribution of different windows to buildings environmental impact. This methodology is capable of guiding further development of smart windows. It was already used in HarWin to improve the construction and reduce the embodied energy of the new light weight frame and to show added value of new materials, like e.g. basalt glass and glass flakes. Photographs of HarWin glazing and window Demonstrators are shown in Figure 2.
Tables and figures: see attached pdf-file.

Project Results:
i. The material development for HarWin glazing follows the concept of decoupling of mechanical and thermal properties from the visible light transmission and sound characteristics of the glazing, by designing polymer-glass composites with different structural features at the micro-, meso- and macro scale. Using the guidance from simulation different manufacturing methods were tested to arrive at the desired microstructure of the composite interlayers and to find an optimum between stiffness and weight of the glazing at the macroscale. A very good agreement is achieved between mesoscale simulation and experimental verification of the elastic and sound damping properties of the composite interlayers.
ii. Experimental verification of thermal properties of the polymer-glass composites has shown a very good matching between simulated and real thermal properties. The results of thermal measurements combined with experimental results of Visible Light Transmission (VLT) and haze measurements on such composites revealed the conflict to achieve a very low thermal conductivity with polymer-glass particle interlayers at the required high VLT and low haze values. Lowering of the U-value at macroscale of a window is therefore achieved with gas filled gaps in a light weight multiple glazing.
iii. For the achievement of a high VLT and low haze of polymer-glass particle composites a perfect matching of refraction index between the polymer and the glass particles has been found to be crucial. This has been accomplished by adjustment of glass composition and melt-based manufacturing of glass flakes for assembly of the 3rd stage Demonstrators.
iv. Besides optimization of the polymer-glass particle composites also different methods to laminate thin glass panes with the newly developed polymer-glass flake composites were investigated with the goal of perfect connectivity between the composite interlayers and the thin glass panes.
v. LCI (Life Cycle Inventory) data sets and basic LCA methodology of glass flake polymer composite materials and for light weight frames were developed to enable analysis of the specialized HarWin windows benefits as compared to state of art triple glazing windows.
WP2: In order to enable solar energy harvesting the glazing must have a high Visible Light Transmission and as low as possible heat gain. This is achieved with Anti-Reflective (AR) and low emissivity, low E coatings applied on the individual panes of a multiple glazing. Detailed investigations were performed on laminated glazing as compared to state of the art multiple glazing to establish the optimized arrangement of the different coatings to thin glass laminated panes reinforced with polymer-glass composite interlayers and other glass panes arranged within the multiple glazing.
Application of porous SiO2 coatings on the outer glass pane of the laminated glazing yields a VLT increase in the range of 4-6%, depending upon the cleanliness of the lamination process while low E coatings cause a significant reduction of VLT. In multiple glazings low E coatings are needed to reduce the thermal gain and enable a small U-value. It is therefore required to combine different coatings and use additional principles of energy harvesting to develop smart windows with reduced energy over the life cycle.
The goal of solar energy harvesting in HarWin is based on a thermal and on a lighting effect. Thermal energy is stored and released with the help of Phase Changing Materials, PCM, which are encapsulated in porous glass particles and embedded with the help of polymers in laminated glazing.
The lighting effect is based on Luminescent Down Conversion, the absorption of high energy photons from the UV part of sun radiation by a special glass which converts the absorbed UV light into the visible wavelength range and emits radiation at ~500 nm.
Based on material development in WP 1, WP2 for glazing and WP4 for frame in WP 3 demonstrator-size glazing components were manufactured along with demonstrator size light weight frame. The glazing area is 500x500 mm, the total area of glazing and frame is 600x600 mm.
Weight reduction of almost 50% as compared to state of the art triple glazing is achieved by reducing the thickness of the glass panes and increasing the stiffness of the glazing by lamination of thin glass panes with glass particle reinforced polymer interlayers.
The selection of individual glass pane thickness, arrangement of laminated and single panes of different thickness as well as of the width of gas filled gap was guided by macro-simulation to arrive at as low as possible U-value, highest possible VLT and lowest possible weight.
The required high visible light transmission (VLT) is achieved by combined effect of high visible light transparency of the polymer-glass composite foils, AR-coatings at the outer glass pane, ultra-white glass panes and low haze.
Integration of passive solar energy harvesting by means of PCM latent heat storage at daytime and release at night has been made possible with organic PCM-materials. For implementation of PCM into laminate glazing restrictions with respect to choice of PCM material and polymer interlayers were identified. Also, unexpected physical effects were discovered upon infiltration of PCM into porous glass particles, the phase transformation was retarded in the nano-scaled pores of the porous glass and the composition of the inorganic PCM was irreversible changed upon infiltration of the PVM into the porous glass particles in an autoclave process. A
As feasible solution organic PCM incorporated in porous glass and laminated with different polymers between panes has been identified and processed in Demonstrator size of 500x500 mm. The constraints of specialized glazing and PCM-containing glazing were analyzed for different types of buildings and environments.
In WP 4 the material development results from WP1 and WP 2 as well as processing concepts developed in these workpackages were taken further towards development of manufacturing methods for different glazing components, light weight polymer-glass composite frames and demonstrators which assembly both types of newly developed components.
Data on mechanical and thermal properties of the glazing and frame components were collected from experimental investigation on lab-scale samples processed with the same methods which were also applied for manufacturing of the Demonstrators. These data were used for macroscopic simulation performed with the aim to support and improve the final design of the Demonstrators. Also, component and processing data were provided to further develop the new LCEA toll for windows established by JRC.
With respect to frame improvement experimental results revealed the optimum sandwich structure to be composed of Expanded Polypropylene -GF reinforced tapes with final specific density of 120 kg/m³, (EPP 120) and a Polyethylene-Terephtalt (PET) as foam core. For these structures a very high adhesive strength was found along with a low thermal conductivity and a high flexural stiffness. Based on LCEA results a “monomaterial” sandwich structure is to be preferred, made of Polypropylene matrix polymers.
Modeling of composite frame integrated with polymer-composite glazing was performed based on measured mechanical data, and the potential for implementation of micro-mechanical models was tested. Results of LCE analysis of the embodied energy of materials used were implemented into the optimization of frame and glazing integration with respect to material consumption needed to achieve the required mechanical performance. The detailed results of LCEA and added value analysis are reported in WP 5. The design of the frame and glazing was modified to improve thermal resistance and overcome restrictions from a certain manufacturing technology. In order to improve the thermal insulation of the glazing, a gas filled gap like in all multiple glazings is also applied in HarWin glazing structure.
In the first half of the project the virtual test environment using Dynamic Simulation Modeling (DSM) method based on IES software has been used to define different building types, climate zones and characteristic features of new as well as old buildings to establish a ranking list of building applications for the newly developed HarWin windows. In the second period of the project modelling of building performance with specialized HarWin glazing and frame has been performed and compared against a reference case with state of the art multiple pane windows.
Experimental data collected from the 1st and 2nd Demonstrator glazing and frame were implemented into the existing software with the help of a new tool. Simulation of different design variants – specialized pane and new light weight frame has been performed to establish a ranking list of building applications.
24 baseline scenario models are presented in D5.5 i.e. 3 building types x 4 climate zones x 2 construction scenarios per building type. In addition to the 24 baseline scenario models a further 6 models per scenario model have been created representing the following HarWin demonstrators: 1) Glazing 1 and frame 1, 2) Glazing 1 and frame 2, 3) Glazing 2 and frame 1, 4) Glazing 2 and frame 2, 5) Glazing 3 and frame 1, 6) Glazing 3 and frame 2. Each demonstrator combination of glazing and frame creates a new modelling scenario, a total of 168 modelling scenarios and variants were simulated.
With respect to holistic analysis a “Life Cycle Environmental Assessment (LCEA) HarWin tool” has been created with the aim of helping the HarWin partners to address the environmental loads of the innovative glazing and framing systems during the different stages of the design process.
The tool has been thought to help with the identification of the most influencing parameters under the environmental point of view. The tool is presented in the format of an Microsoft (MS) Excel tool (see M20). The tool is a simplified Life Cycle Assessment (LCA) tool streamlined to HarWin windows. These features allow manipulation of the tool by non LCA experts (i.e. partners of the consortium) so that Research and Development (R&D) decisions can be made not only on technical and functional grounds but also on environmental grounds.
The aim of WP 6 tasks it to define an adapted methodology to assess the environmental impacts of new multi-purpose windows along their life cycle. The environmental assessment must provide quantitative information which enables distinction between different material and construction variants of windows for different building applications. With such information those variants which will reach the project goal of 20% energy saving over the life cycle as compared to existing windows should be identified.
This is a very ambitious goal because windows are multi-component systems therefore a new methodology had to be developed to define boundary conditions and the most relevant parameters for LCE analysis.
Within the HarWin project the new LCE approach is required to characterize environmental impacts of the multi-purpose window and to identify and rank its most influencing parameters.
An important role of the new LCE methodology is to support dissemination of technical achievements of the HarWin project as well as to disseminate the LCEA tool as such and to help implement smart windows with low embodied energy into buildings to enhance the project impact. The major achievements include a new methodology to assess the environmental impacts of new multi-purpose windows along their life cycle by provision of :
i. An adapted “LCEAHARWIN” method and “Recyclability analysis” method
ii. Datasheet for environmental primary data gathering;
iii. Feature-specific tool for the ecodesign “LCEA HarWin tool”
This new methodology is applicable as design tool for new window components – throughout the development of HarWin components the environmental analysis of possible materials and processes for polymer-glass composite glazing and glass-fibre reinforced light weight frame has been carried out to support the different phases of the design process.
The most influencing parameters for the HarWin windows were identified and ranked. The environmental analysis of product functionality integrated into buildings has been achieved in comparison to the reference case. Based on these results the potential for replacement of existing windows could be evaluated for different building types and climate zones.
The tools developed for LCA were integrated into existing databases of building simulation software, e.g. HarWin window into the and a dataset to be published through the Life Cycle Data Network.
A very intensive Dissemination has been practiced through conference papers and posters as well as peer-reviewed journal papers.
Finally, the HarWin organizational set-up can be seen as a successful example of integration of the environmental dimension into the R&D project management.
Full text see attached pdf-file.
Potential Impact:
i. Increase of awareness among experts as well as the wider public of the possibilities to reduce the energy consumption of buildings with the help of new materials and new design of windows.
ii. Provide new materials and processing technologies to achieve weight reduction of windows in the order of magnitude of 50% as compared to triple glazing windows and achieve an easier installation and maintenance of windows in building
iii. Provide new methodology for LCEA of windows and window components and a foundation for guiding further development of windows components according to LCEA guidance
iv. Provide methods for cost analysis of new window components as compared to existing ones
v. Provide simulation tools for analysis of building performance and buildings constraints resulting from use of new window materials and design
vi. Enlarge the technology variants to save, store or harvest solar energy with the help of multifunctional materials for windows.

Summary on exploitation & dissemination activities:
The Dissemination and Exploitation Plan was developed by BayFOR and GX based on inputs from the entire HarWin consortium. Analysis of future markets has been undertaken to support the partners during the project and to adjust the scientific and technical development according to the industrial needs and also to customer acceptance. The exploitation plan has been continuously updated. Contents were kept up to date through discussions with the project partners. The topics of Dissemination, Exploitation, project risk and IPR where discussed at the Exploitation Strategy Seminars at the M12 meeting in Brussels.
Potential future markets and products where analyzed by GX, resulting in the specification of product requirements for HarWin project results which show potential for implementation as marketable products. An example of market analysis is shown in Figure 2.7-1.
The analysis was based on the demands arising from regulation, industrial needs, customer acceptance and product value proposition (in comparison to current state-of-the-art products). These requirements were added as an appendix to the Dissemination and Exploitation Plan.
European-wide dissemination of the project results to the scientific community took place through conferences in Italy, Germany, Serbia, Switzerland, Spain, Poland, Greece, Latvia, Austria, to name some.
Within the World Sustainable Energy Days a special workshop and exhibition on Smart Windows has been organized together with other EU-Smart Windows projects. In addition two Dissemination and Exploitation workshops were organized: in 2013 in Szczecin (Poland) and in 2015 in Nürnberg (Germany) with strong participation from Industry.
Additional specialized workshops were organized on LCEA, in 2014 in Ispra, Italy and on Standardization within the Smart Windows workshop in Wels, Austria.
A strong contribution to Dissemination and Exploitation came through the involvement of EUROWINDOR as Industrial Advisory Board.
Through this professional network SME and large companies became aware of HarWin. The final outcomes of the project will be communicated through the newsletter of EUROWINDOR.
In addition, HarWin is participating in the AMANAC Cluster, which also intensifies the Dissemination activities beyond the lifetime of the HarWin project. A summary of major dissemination activities:
i. Home page kept up-to-date, e.g. with links to SMART WINDOWS projects
ii. Clustering and knowledge exchange among sister “SMART WINDOWS” projects EELICON, SmartBlind, MEM4WIN, WinSmart and HarWin
iii. Joint “Smart Windows” workshop at WSED in Wels, February 2015, Austria
iv. Two HarWin-workshops: in Stettin (together with WUT) and Nuremberg: fostering scientific and economical discussions between the HarWin consortium and external stakeholders
v. Fostering standardization discussions between the HarWin consortium and European and international stakeholders, e.g. EUROWINDOR
vi. Presentation of HarWin with talks at several conferences (e.g. Prague, Rosenheim, Biel, San Sebastian)
vii. Presentation of HarWin Demonstrators at several exhibitions and workshops.

tables and figures are included in the pdf-file.

List of Websites:
Project website address: