Research on the Optimisation of Dual-Heat-Source Heating Systems in Nearly Zero-Energy Buildings

A nearly zero-energy building is characterised by its low energy demand and enhanced thermal insulation, with great potential to integrate renewable energy systems to satisfy various demands and improve energy efficiency. Solar energy is a primary renewable energy resource that can be harnessed in different ways to provide electricity, heating, and cooling in building applications. In this study, a solar–ground-source heat pump system was designed and established in a nearly zero-energy building. The system’s performance was presented, and its control strategy was optimised. To evaluate and assess the operation of the solar energy system, an experimental setup was built, and the experiment was divided into two periods, taking into account the weather conditions. In the first experimental period, different parameters of the heating system were tested and evaluated. In this regard, the variation trends of the heat pump unit’s coefficient of performance, the system coefficient of performance, the collector start-up temperature difference, and the heat pump setting temperature were analysed under different parameter combinations. On this basis, the optimal operating parameters were identified for different heating periods. In the second period, the optimal operating parameters identified were used to carry out heating experiments. The results highlighted that the adoption of the preferred operating parameters increases the percentage of direct solar energy supply by 2.0%. Additionally, the system coefficient of performance increases by 8.9%, the unit coefficient of performance increases by 6.7%, the carbon emissions are reduced by 4.18 tonnes, the SO 2 emissions are reduced by 0.143 tonnes, and the dust emissions are reduced by 0.1 tonnes. The findings of this study can provide useful data and a guiding reference for optimising and promoting the implementation of renewable-energy-driven heating systems for nearly zero-energy buildings in severe cold regions.