Performance Analysis of a Solar-Air Source Absorption Heat Pump with Different Working Fluid

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, has been proposed for water heating. This system runs in SD (Solar-energy driving) or GD (Gas-combustion-heat driving) mode, designed to utilize renewable energies as much as possible. The models for each component were built and the corresponding heat and mass balance equations were established. The performance of SAAHP based on LiBr/H2O and LiNO3/H2O working fluids was simulated and compared with an air source absorption heat pump (AAHP) based on LiBr/H2O. Results indicated that SAAHP based on LiNO3/H2O has a higher solar energy utilization rate than that based on LiBr/H2O due to its lower solar collector inlet temperature in SD mode. In comparison to AAHP based on LiBr/H2O, SAAHP based on both of LiBr/H2O and LiNO3/H2O achieved a higher primary energy COP throughout a year. Relative to a gas-fired hot water boiler, SAAHP based on LiNO3/H2O and LiBr/H2O achieved yearly primary energy saving rates of 46.2% and 40.0%, respectively, whereas AAHP just achieved 12.2%. SAAHP based on LiNO3/H2O shows significant energy saving potential in the building energy consumption.