Residential demand-side management using integrated solar-powered heat pump and thermal storage

Due to the mismatch between rooftop solar energy generation and residential electrical demand, considerable solar energy is exported into electricity networks causing a range of issues such as voltage instability and connection overload. To address these problems, we propose and analyse a residential hot water, heating and cooling system, which features a heat pump combined with thermal energy storage to align peak thermal loads with output from a rooftop solar system. This work quantifies the impacts of thermal storage on residential space-conditioning peak load reduction. Annual hourly thermal and domestic hot water loads were determined for a representative Australian house, located in Brisbane, using building energy simulation software and verified using measured data. Combined with the measured sub-metered electrical loads of other electrical appliances, this data was used to simulate the solar system export, heat pump demand, and thermal storage system performance. Results show that by combining a 5-kW solar system, the proposed system can reduce annual grid-electricity demand by approximately 76% compared with a conventional non-thermal storage system. Peak electrical load was also observed to undergo a temporal shift and reduce by approximately 45%. Furthermore, the solar fraction for air-conditioning and domestic hot water loads reached 84%, while solar self-consumption increased to about 56%. This study demonstrates that the proposed system is an effective means of managing electricity demand, shifting peak load and improving solar utilization, thus relieving stress on electricity networks from high penetration of solar photovoltaics.