Energetic, economic and environmental analysis of a direct expansion photovoltaic solar assisted heat pump with low-GWP refrigerants

Abstract

The use of heat pumps may contribute to a substantial reduction in greenhouse gas emissions which is in accordance with climate commitments. A direct expansion photovoltaic thermal solar assisted heat pump (DX-PVT-SAHP) is capable of generating both electrical and thermal energy and this work explores the lack of studies of DX-PVT-SAHP using refrigerants with low Global Warming Potential (GWP). The main objective of this work is to evaluate the performance of low GWP refrigerants from an energy, economic, and environmental (3E) perspective when used in a DX-PVT-SAHP. To achieve this objective, a mathematical model was developed to simulate the heat pump operation under different operating conditions. A bench test was constructed to validate the proposed model. The numeric model that employs a moving boundary model for the heat exchangers and a semi-empirical model for the compressor was used to compare the COP of refrigerants and power output of R134a, R1234yf, R290, R600a, R513A, R454C and R455A. Additionally, the Seasonal Performance Factor (SPF) and Total Equivalent Warming Impact (TEWI) were calculated considering the hourly mean solar irradiation, ambient temperature, dew point temperature and wind speed from 07:00 a.m. to 6:00 p.m. in 2024 for Belo Horizonte-MG. R1234yf presented the best results of COP among the compared low GWP pure refrigerants, increasing the COP value from 2.21 at 50 $W/m^2$ to 4.06 at 1000 $W/m^2$, additionally the best TEWI value was presented by R1234yf due to its low GWP value combined with the best SPF among the low GWP fluids. The payback for R1234yf was 2.8 years.