A novel configuration for an STES system based on a novel SWS material was developed. The operational conditions of the system were defined by simulating the climatic conditions at central and northern Europe, whereas the system alongside its control software were designed to meet the specific needs of a typical single-family house in these regions. Devoted occupant-building interaction models were developed and integrated in the building models to fully define the demand profiles in the considered climatic zones while at the same time ensuring optimal thermal comfort for the end users. According to this analysis all the necessary components were designed and manufactured. The most crucial components were the Heat Exchangers (HEXs), the heating distribution system (i.e. a storage tank with minimal losses being able to store heat at different temperature levels) and naturally the SWS material.
The developed novel SWS material showed superior compactness showing high heat storage density (1.1-1.3 GJ/m3 - over 20 % greater than existing SWS materials). The SWS material was not degraded, nor did it lose adsorption capacity after 1,000 ageing test cycles under severe working conditions . A single-plate heat HEX was designed to be used as an adsorber/desorber as well as an evaporator/condenser. This technological feat will significantly reduce costs since only one type of HEX is needed. Critically, this HEX has more than double capacity of adsorbent volume compared to commercial HEXs. This means much more adsorbent to trap water molecules, enhancing storage density and performance. Simulations of the performance of tthis HEX were really promising. However, due to the COVID pandemic, commercial HEXs were used and the experimental confirmation of the benefits of the novel HEXs are one of the major future tasks for further developing this technology. As regards the designed compact vacuum combi-storage tank, it proved to be cost effective whilst achieving enhanced stratification and minimal heat losses.
All these components were individually tested before being installed at a demonstration prototype: a container was reformed into a prototype SWS-HEATING system next to a “living room” simulating the thermal needs of a single-family house.
The tests were successful and to study the system operation even under punishingly cold conditions. Most importantly, this technology can be considered as a proven technology but at low level towards commercialization. Moreover, according to system simulations, the advanced features of the control unit and the optimized design make it possible to achieve and overcome the performance threshold of 60% solar fraction. Finally, a technology roadmap was developed, showcasing the next steps towards further developing this promising technology. This roadmap alongside three videos showing the project concept and the developed technology can be found on the project website.
