Performance Analysis of a Solar–Air Source Absorption Heat Pump with Different Working Fluids

A solar–air source absorption heat pump (SAAHP), which mainly consists of a solar collector, a fan coil, and an absorption heat pump equipped with a gas-fired combustor, was proposed for water heating. This system runs in either SD (solar-energy-driving) or GD (gas-combustion-heat-driving) mode and is designed to utilize renewable energies whenever possible. The models for each component were built, and the corresponding heat and mass balance equations were established. The SAAHP’s performance with the LiBr/H2O and LiNO3/H2O working fluids was simulated and compared with an air source absorption heat pump (AAHP) using LiBr/H2O. The results indicated that the LiNO3/H2O-based SAAHP has a higher solar energy utilization rate than the LiBr/H2O-based pump due to its lower solar collector inlet temperature in SD mode. Similarly, it achieved a higher primary energy COP throughout the year than both the LiBr/H2O- and LiNO3/H2O-based SAAHPs. Compared to a gas-fired hot water boiler, the SAAHPs based on LiNO3/H2O and LiBr/H2O achieved yearly primary energy-saving rates of 46.2% and 40.0%, respectively, whereas the AAHP only achieved a rate of 12.2%. Thus, the LiNO3/H2O-based SAAHP shows significant energy-saving potential in building energy use.