Abstract
An innovative thermal energy storage system (TESSe2b) was retrofitted in a residential building in Cyprus with a typical Mediterranean climate. The system comprises flat-plate solar collectors, thermal energy storage tanks filled with organic phase change material, a geothermal installation consisting of borehole heat exchangers with and without phase change material and a ground source heat pump, an advanced self-learning control system, backup devices and several other auxiliary components. The thermal energy storage tanks cover the building’s needs at certain temperature ranges (10–17 °C for cooling, 38–45 °C for heating and 50–60 °C for domestic hot water). A performance evaluation was conducted by comparing the TESSe2b system with the existing conventional heating and cooling system. The systems were simulated using commercial software, and the performance of the systems and the building’s energy needs were calculated. Based on the energy quantities, an economic analysis followed. The equivalent annual primary energy consumption with the conventional system resulted in being 43335 kWh, while for the storage system, it was only 8398 kWh. The payback period for the storage system was calculated to be equal to 9.76 years. The operation of the installed storage system provided data for calculations of the seasonal performance factor and storage performance. The seasonal performance factor values were very high during June, July and August, since the TESSe2b system works very efficiently in cooling mode due to the very high temperatures that dominate in Cyprus. The measured stored thermal energy for cooling, heating and domestic hot water resulted in being 14.5, 21.9 and 6.2 kWh, respectively. Moreover, the total volume of the phase change material thermal energy storage tanks for heating and domestic hot water was calculated to be roughly several times smaller than the volume of a tank with water as a storage medium.
Highlights
Climate change necessitates solutions for the reduction of buildings’ thermal energy needs
Solar energy has been utilized in residential cooling and heating and domestic hot water (DHW) production systems [2,3], it is a time-dependent energy resource
The weak point in borehole heat exchangers (BHEs) is that heat transfer in the ground is mainly conductive with low thermal diffusivity, which leads to a much slower ground thermal response than the heat pump’s requirements, resulting in a lower coefficient of performance for ground source heat pumps (GSHPs)
Summary
Climate change necessitates solutions for the reduction of buildings’ thermal energy needs Along these lines, the European Commission recently revised the Energy Efficiency. Thermal energy storage is a technology that has gained popularity over recent years [6,7,8] as it can help to integrate high shares of renewable energy in power generation, industry and buildings. It is a key element of the energy transition measures for all countries in the post-COVID period. In light of the above, in the TESSe2b project [12] the potential for a thermal energy storage system for energy-efficient buildings was investigated. The thermal energy storage supported a 44.8% shift of the heating needs from day to night and a 30.3% shift in the cooling needs
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