An experimental approach for the dynamic investigation on solar assisted direct expansion heat pumps

In this paper, a direct expansion solar assisted heat pump (DX-SAHP) is investigated as one of the possible low environmental impact solutions to the domestic thermal energy demand, even if due to some technological and control strategy limitations, the DX-SAHP systems do not have a competitive role in the actual renewable energy market. An instrumented prototype of a small DX-SAHP system is here designed and presented, within the context of developing safe and affordable sustainable energy applications, to determine the best control strategies and to measure the energy performance indices with good reliability and accuracy. The property calculation tool and the main issues related to the performance measurements and calculations are reported, with an estimation of the measurement error. The results of test series evidence that the apparatus can fulfil significant thermal loads, with a coefficient of performance (COP) up to 6.