A solar-air source heat pump with thermosiphon to efficiently utilize solar energy

Traditional solar heat pump cannot utilize either solar energy efficiently or thermal energy in ambient air. A hybrid solar–air source heat pump with thermosiphon using a multi-function evaporator was proposed to take the advantages of both air thermal energy and solar energy. The novel heat pump can absorb heat from single heat source (i.e. solar energy or ambient air) or their combination. Moreover, it can work in the thermosiphon mode or the heat pump mode according to the solar intensity. A validated numerical model was established to simulate the performance of the proposed system under different working conditions, and a comparison with conventional heating systems was also made. It shows that the coefficients of performance of the proposed heat pump in the air source heat pump mode, solar-air source heat pump mode and solar heat pump mode are 3.12, 3.45 and 3.89, respectively. Besides, it's able to supply heat without energy consumption by solar thermosiphon mode when the solar energy is sufficient. The primary energy efficiency of the proposed system during a heating season are 1.14, 1.15, 1.54, and 0.97 in Beijing, Chengdu, Lhasa, and Shenyang, respectively. The energy saving rates can reach 48% and 66% compared with air source heat pump and the conventional solar heating system, respectively.