Case study on optimal design and operation of detached house energy system: Solar, battery, and ground source heat pump

Government policy impacts the level of sustainability for which houseowners design and operate their energy system. Consequently, there is a need to consider the sustainability level resulting from different policies, assuming optimal design and operation. The present work focuses on detached residential houses, where the energy system consists of photovoltaic systems for energy generation and batteries and optional ground-source heat pump systems for energy storage. A mixed-integer linear programming model is presented, which takes policies and other constraints into account when optimizing system size and operation. The results allow overall sustainability validation through parameters like self-sufficiency and self-sustainability, as well as a detailed drill-down of the optimal operation. From the analysis, two modes of ground-source heat pump usage are seen. With a feed-in tariff present, its main use is as an energy source, while without this tariff the optimal use is for seasonal energy storage. It is also found that ground-source heat pump systems contribute to increased sustainability, but they may not be economically beneficial for single-family homes having low or medium heating requirements. Demands for heating and cooling change with time and place, as do available area for photovoltaic energy generation and externally available energy sources. Therefore, a detailed analysis of the kind presented here is recommended before new energy policies are implemented. For each specific house or project, this kind of analysis will also be useful to evaluate the sensitivity of an energy system's performance towards changing policies.