Energy demand for heating and cooling represents a large part of non-residential buildings´ energy consumption around the world.

Building envelope (like walls, roofs and floors), either in residential or non-residential applications, is one of the most important building objects that could benefit from energy efficient designs and innovations. Storing solar and/or environmental heating/cooling energy in building components is a way to level-out daily indoor temperature variation and to significantly cut back energy demands.

A way to achieve this goal is to develop novel Phase Change Materials (PCMs) – based cementitious products, characterized by a specific/responsive porous microstructure that accommodates the PCMs and has the potential to store/release energy due to a reversible change from a solid to a liquid phase.

In this context, the NRG-STORAGE project aims to launch a novel breakthrough solution that replaces the currently available insulation materials used in building envelopes, by proposing a multi-functional and energy saving cementitious Foam (NRG-Foam).

NRG-Foam composites are designed to achieve the best compromise between thermal insulating properties and heat storage capacity by incorporating Microencapsulated bio-based Phase Change Materials (bio-MPCMs) in the initial cement paste.

In addition, graphene-based nano-additives, added to both cementitious foam matrix and MPCMs fraction help to improve the composite mechanical properties and to reduce the hardening shrinkage phenomena and associated ageing effects.

Improvements in the energy storage capacity of the foam will also be achieved through two active systems which will work together in an optimized configuration as: (i) an active system at the material scale level, triggering the PCM melting by the electrical activation of the embedded graphene; and (ii) an active external full-scale system, developed in a previous EU project, which will recover the storage capacity of the envelope by re-solidifying the melted PCMs.

These complementary systems will be optimized 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, an improvement of, at least, 15% in energy-storage capability than actual solutions has been confirmed by preliminary simulations.

The 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 the next generation of prefabricated NRG-Foam insulation material.

The proposed product aims to comply 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 existing solutions based on synthetic materials, glass fibers or stone wools.

This highly efficient and sustainable solution also shows a reduced layer thickness (50% thinner than EPS), a non-flammability, a very low CO₂ footprint, a non-toxicity, acoustic insulation/absorption capabilities, dimensional stability, without affecting the indoor air quality and it is easily recyclable.

Finally, the proposed NRG-Foam can be produced as prefabricated panels, with minimum manufacturing and installation costs, allowing its use in new buildings and for retrofitting purposes.

To reach these ambitious goals, the NRG-STORAGE project is based on a multidisciplinary consortium of 13 partners.

CIC energiGUNE’s role

CIC energiGUNE Thermal Energy Solutions (TES) area is particularly involved in two work packages of the NRG-STORAGE project: the design of components for thermal energy storage (WP1) and the identification of strength improvements and development of NRG foam (WP2).

The center, in close collaboration with other partners, is thus mainly in charge of the NRG-Foam design through the in-depth thermal characterization of all the ingredients of the compounds of this innovative material (cement paste, graphene oxide nanoplatelets and microencapsulated PCM) to ensure the reproducibility of its production and to determine the key thermodynamic properties that ensure the greatest amount of energy storage/release.

After 2 years and half

Since the beginning of the project (April 2020), the following progress has been achieved:

• Design and production of nano-modified components (graphene-based) to be added in cement paste and in microencapsulated Phase Change Materials.
• Development and production of microencapsulated PCMs (bio & paraffin-based) to reduce their reactivity with the outside environment, increase their heat-transfer area and allow the PCMs to withstand frequent changes in volume inside the particles.
• Development of nano-modified microencapsulated-PCM (hybridized Graphene + Capsules) and thermally and electrically conductive Phase Change Cementitious Composite (PCCC).
• Characterization of components (steady-state and dynamic thermal properties).
• Design and numerical optimization of the NRG-Foam composites.
• Casting of NRG-Foam composites and analysis of microstructures.
• Structural design and construction of the demonstration buildings. Skin layer design as well as structural connection. Installation of the monitoring system.
• Simulations of cracking of the walls and the NRG-Foam insulation panels during seismic pushover analysis of the demo houses.

The next stage of the NRG project seems to be an exciting one with the integration of the most promising foams into monitored experimental facilities and real buildings. The project is thus on track to demonstrate the effectiveness in terms of insulation & storage capacity, of water/air tightness, eco-sustainability and cost of this new cementitious material including phase change materials for active/passive energy storage in buildings.

NRG-STORAGE project (number 870114) is financed by the European Union H2020 Framework under the LC-EEB-01-2019 call, H2020-NMBP-ST-IND-2018-2020/H2020-NMBP-EEB-2019FOR GREEN ACTIVE/PASSIVE ENERGY STORAGE.