Energetic, exergetic, environmental and economic (4E) analysis of a direct-expansion solar-assisted heat pump with low GWP refrigerant

Abstract

The main objective of this study was to develop, validate and apply a mathematical model for analysing the performance of a Direct-Expansion Solar-Assisted Heat Pump (DX-SAHP) based on the energetic, exergetic, environmental, and economic (4E) analysis. The DX-SAHP produces domestic hot water using the low-global-warming-potential (GWP) refrigerant R290 which is the best candidate for energy, environmental, and logistical performance among six previously evaluated candidates (R152a, R744, R1234yf, R1234ze(E), R170, R290). Environmental and economic analysis are founded, respectively, on Total Equivalent Warming Impact (TEWI) and payback. The proposed model was validated using an experimental test bench developed for this study. Using the validated model, simulations were conducted to investigate the influence of geometric parameters (evaporator area and condenser length) on the system's performance. The results show that increasing the evaporator area yields the greatest increase in COP (117 and 80.4%) and the greatest decrease in TEWI (53.8 and 44.5%) for final water temperatures of 45 and 65°C, respectively. However, this also leads to a drop in collector efficiency (58.7 and 60.8%) but results in a shorter payback time (6.06 and 3.87 years) for final water temperatures of 45 and 65°C, respectively. The greatest increase in exergy efficiency (11.5 and 14.1%) occurs with an increase in condenser length for final water temperatures of 45 and 65°C, respectively.