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Integrated porous cementitious Nanocomposites in non-Residential building envelopes for Green active/passive energy STORAGE

Periodic Reporting for period 1 - NRG-STORAGE (Integrated porous cementitious Nanocomposites in non-Residential building envelopes for Green active/passive energy STORAGE)

Reporting period: 2020-04-01 to 2021-09-30

The IEA actions aim at ensuring reliable, affordable and clean energy solutions for its 29 member countries and beyond. One of the mission is guided by an“energy concept”, which has the ambition to reduce by 20% in 2020 and 50% in 2050 the primary energy consumption compared to the 2008 levels. Energy demand for heating and cooling represents a large part of non-residential buildings' energy consumption around the world. Building envelope (either in residential or non-residential applications) is actually one of the most important building objects that could take effective energy designs and innovations. Storing solar and/or environmental heat/cooling energy in building components of non-residential constructions is a way to level-out daily temperature differences and to significantly cut back energy demands. A way to achieve this goal is to develop novel Phase Change Materials (PCMs) – based cementitious products, characterised by a specific/responsive porous microstructure that accommodates the PCMs and has the potential to store/release energy due to a reversible and repeatable change from a solid to a liquid phase and vice-versa.
The main objective of the project is to develop and demonstrate a novel ultra-light cementitious insulation material that includes PCMs for both active/passive energy storage in non-residential buildings. The NRG-STORAGE project will ultimately contribute to the fast growing market of building envelopes, for both retrofitting and newly built objects, by implementing the TRL levels 5 to 7 of a next generation of prefabricated insulation material, called NRG-Foam. The proposed product complies with a more than 25% improved insulation capacity, more than 10% higher energy-storage capacity, at least 10% higher water and air tightness, and less than 15% cost increase than the actual solutions.The project proposes a highly efficient and sustainable solution with excellent advantages compared to the currently applied class of insulation materials. For example, it has an improved heat storage capacity (8 times better) and reduced layer thickness (50% thinner, “skin layer”) than EPS, it is a non-flammable product, it has a very low CO2 footprint, is non-toxic, has acoustic insulation/absorption capabilities, is dimensionally stable, it doesn’t affect the indoor air quality and can easily be recycled. The proposed NRG-Foam can be produced as prefabricated panels, with minimum manufacturing and installation costs.
The following work was performed during the first reporting period:

- Design and production of nano-modified components (graphene-based) to be added in cement and for encapsulations.

- Development and production of microencapsulated PCMs to reduce their reactivity with the outside environment increase the heat-transfer area, allows the PCMs to withstand frequent changes in volume inside the particles.

- Development of nano-modified encapsulated-PCM (hybridised Graphene + Capsules) and thermally and electrically conductive Phase Change Cementitious Composite (PCCC).

- Preliminary checks and characterisation of components (steady-state and dynamic thermal properties).

- Design and numerical optimisation of the NRG-Foam composites.

- Casting the NRG-Foam composites and analysis of microstructures.

- Structural design and initial construction of the demonstration buildings and skin layer design as well as structural connection.

For dissemination and exploitation a Project website was launched, registered under the url: www.nrg-storage.eu.
The project is also present on various social media networks. It is registered under the urls www.facebook.com/NRGSTORAGE and www.instagram.com/nrg_storage/.
A "Technical Committee" (TC) of the organization RILEM was founded with the name TES (Thermal energy storage in cementitious composites) and the project partners NETZSCH and TUDa are members of the DIN Standardisation Committee NA 062-08-14 AA "Thermal Analysis" into which results of the project are embedded. A Data Management Plan (DMP) was developed to professionally manage project results data.

Work needed to achieve the objectives for all work packages was accomplished within the schedule as outlined in the DoA.
When compared to state of the art, the newly developed NRG-Foam should bring an improvement of at least 25% for the insulation properties at component level for a given weight, when in isolation (passive) mode; 10% improvement in energy-storage capability when in active mode(s); Water and air tightness should be at least 10% higher than existing solutions (when it is proposed a controllable solution); Cost increase of less than 15%, in order to allow market uptake across Europe and contribute to social affordability. Beyond the state of the art the following results are expected:

NRG-STORAGE will offer significant improvements of the thermal insulation property. Preliminary research confirmed that improvements up to 40% can be obtained when the system is used in passive mode. Moreover, being an “ultra-light” system, the improvements will be even higher when results are compared with respect to the weight of currently available insulation systems.

Improvements of the energy storage capacity will be achieved through two active systems which will work together in an optimised configuration as: (i) an active system at the material scale level, activating the embedded graphene via electricity and aimed at actively imposing the PCM to melt, and ii) an active external full-scale system, developed in a previous EU project, which will be mainly utilised for re-solidifying the melted PCMs. These complementary systems will be optimised to have the best performance among the three different climatic conditions (Mediterranean, oceanic and humid continental) chosen as a reference for the demonstration sites. In this context, at least 15% improvement in energy-storage capability has been confirmed by preliminary simulations.

The characteristics of the NRG-Foam composites will enable water and airtight products of high quality. On one hand, the presence of Graphene will improve the mechanical properties of the composite, with a significant reduction of the hardening shrinkage phenomena and associated aging effects. On the other hand the presence of PCM will hugely attenuate the hydration heat after the precast process. This will allow the possibility of realising a better shaping of complex precast geometries with enhanced tolerances. At the same time it will be easy to design a NRG-Foam composite while avoiding possible macro- and microcracks. The result will be a very noble product in terms of water and air tightness. Therefore, hydration simulations with the Hymostruc model, for various mix designs, optimisation procedures and validation activities showed the final product to have a water and tightness increase of at least 20% compared to existing solutions.

The developed solutions proposed in the project are also characterised by a strong reduction of the costs and less complexity on the product installation due to their low weights and high compatibility with traditional construction systems. Preliminary cost calculations showed that an increase is expected in the first years when the product is launched in the market (probably around 7 - 10%), when the NRG-Foam is substituted for conventional EPS. However these costs will rapidly decrease whenever the product will be used at larger scale.
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