“Compact REtrofit Advanced Thermal Energy storage - An economically affordable, compact and loss-free heat battery for existing buildings.”
The CREATE project is a research project supported by the European Commission under the Horizon 2020 programme with the main aim to develop and demonstrate a heat battery, i.e. an advanced thermal storage system based on Thermo-Chemical Materials (TCMs), that enables economically affordable, compact and loss-free storage of heat in existing buildings. The project duration is set to 48 months and, at the moment, the CREATE finds itself in the 22nd month.
A storage system which will cover the domestic hot water and space heating demand of a single-family house with a high solar fraction is being developed under the CREATE project. To achieve this goal, a system design based on the following components has been chosen as the most suitable:
- Heat Battery (seasonal storage)
- Absorber modules with thermochemical material
- Central evaporator/condenser with water reservoir
- Buffer Storage (diurnal storage)
- Heat Pump
- Solar thermal collector
- Ground source
To select the most fitting material for the Thermo-Chemical Material (TCM) used in the storage system, a database of approximately 600 hydrate reactions of salt hydrates has been made based on the salts’ characteristics such as the energy density and the (un)loading temperatures. From this list, K2CO3 was selected for further materials development. Approximately 20 different TCM composites of K2CO3 were produced on lab-scale by partners DOW and CALDIC and extensively tested at the Eindhoven University of Technology. The testing scheme involved experiments to determine the energy density, cyclic (un)loading, pressure-temperature relations, outgassing, mechanical stability and thermal conductivity. Based on the characterization results, two composites have been selected for further upscaling. Currently, these two composites are being tested in a 1kg-reactor at TNO and partners DOW and CALDIC are developing methods for up-scaled production of these composites.
At AEE INTEC, critical components of the storage module, such as the absorber heat exchanger, are designed and tested. The heat exchanger of one module will hold 250 litres of the storage material K2CO3. It will be used to transfer heat to the storage material during the dehydration process in summer and to return heat to the heating system during the hydration process in winter.
The heat exchanger for condensation and evaporation is one of the critical components in the thermochemical storage system. Especially during the discharging phase, the evaporation of water is difficult due to the low-temperature heat source in winter and the unfavourable fluid properties such as the surface tension or higher influence of the hydrostatic pressure. Thus, the design of an efficient evaporator with high heat transfer is necessary as it leads to smaller temperature overheating for the required evaporation performance and consequently enhances the energy density of the storage system.
However, there is still a lack of knowledge regarding the design of the optimal evaporator. For this reason, different concepts and options will be experimentally investigated at the test facility at AEE INTEC. The outcomes of these experiments will help to find the suitable heat exchanger for the final storage system.
This project is supported by the European Commission under the Energy Theme of the Horizon 2020 for research and Technological development Grant Agreement number: 680450
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