Techno-economic performance of photovoltaic-powered air-conditioning heat pumps with variable-speed and fixed-speed compression systems

Abstract

The present study aimed at finding which kind of the two available commercial heat pump types (i.e. the variable-speed and fixed-speed compression systems) would be the appropriate option to become fully photovoltaic (PV)-powered, especially for the office building sector. First, behaviors of the heat pumps are determined based on experimental thermodynamic analyses using T-s (temperature-entropy) cycles. Results reveal that the variable-speed compression system shows up to 400% higher efficiencies under partial loads. The minimum PV systems required for these two systems for 8 working hours (9:00–17:00) in the Tehran climate are designed. The results show that the fixed-speed compression system requires a minimum size of a PV power system twice that of the variable-speed compression counterpart. With the half-sized PV system, the variable-speed compression air-conditioner provides 64% and 88% of the heat and cold of the fixed-speed counterpart, respectively. The economic evaluation shows that it provides 50% and 16% extra cooling and heating compared to those of the fixed-speed counterpart per invested US $. Hence, applying variable-speed compression heat pumps powered by PV systems would be one of the most promising methods for peak-shaving, especially for high cooling demands and in the office building sector.