Green ground source heat pump using various low-global-warming-potential refrigerants: Thermal imbalance and long-term performance
Tian You, Fang Wang
Abstract
Ground source heat pump is a promising technology for achieving carbon neutrality in the building sector owing to its high energy efficiency in heating and cooling applications. To mitigate global warming , low-global-warming-potential refrigerants are explored as long-term substitutes for ground source heat pumps. However, few studies have examined the long-term characteristics of green ground source heat pump systems using low-global-warming-potential refrigerant. This work fills this gap by comparing the long-term performance of ground source heat pump systems using typical low-global-warming-potential hydrofluorocarbon and hydrofluoroolefin refrigerants, with the conventional R134a as a baseline. Results show that the ground source heat pump system with R161 has the smallest thermal imbalance ratio, while the ground source heat pump system with R1234ze(E) suffers from the largest. Compared to R134a, R161 and R1234yf relieve the soil thermal imbalance, while R152a and R1234ze(E) exacerbate the imbalance. After 10 years of operation, the average soil temperature decreases from 10.40 °C to 9.82 °C, 9.58 °C, 9.41 °C, 9.16 °C, and 9.09 °C for R161, R1234yf, R134a, R152a, R1234ze(E), respectively. R1234ze(E) yields the highest annual average coefficient of performance of 4.16–4.20, while R161 shows the lowest value of 3.55–3.56. Compared to R134a, R152a and R1234ze(E) improve the annual coefficient of performance, while R161 and R1234yf degrade it. This work could guide the rational development of green ground source heat pump technologies using promising low-global-warming-potential refrigerants to achieve low environmental impact and high energy efficiency.