A solar-assisted low-temperature district heating and cooling network coupled with a ground-source heat pump

Towards the development of highly integrated and energy efficient heating and cooling systems, with an energy community perspective, the present paper proposes a novel technical solution for the provision of air-conditioning, domestic hot water and electricity to a small residential district in heating-dominant regions. Three reference climates have been considered: Helsinki, Berlin and Strasbourg. Detailed dynamic models have been created using TRNSYS and NeMo, and long term operations of the energy system, including a new-generation ultra-low temperature district heating and cooling network have been performed. The core of the energy system is the network supplied by a high-efficiency ground source heat pump and used as the source and sink by booster heat pumps installed in the substations. Rooftop photovoltaic thermal panels partially meet the electrical demand of the district, as well as the thermal load for domestic hot water production. Moreover, the panels are cooled by the network, obtaining a reduction in the thermal unbalance to the ground and enhancing their electrical efficiency. This solution allows obtaining high coefficient of performance for the heat pumps in the substations and supply stations, reaching values of 5.4 and 4.0, respectively, for heating provision in the coldest locality. The proposed multi-energy district reaches an electrical self-consumption of 71% in the coldest locality and efficiently combines different renewable energy sources at district level in cold climates.