Techno-economic assessment of the advantages of smallscale turbo compressor adoption within brine-to-water heat pump
This paper presents and discusses the results of a research study focused on the technological advancement of heat pump systems, with the primary objective of reducing their Total Cost of Ownership (TCO) and assessing the feasibility of lowpressure refrigerants as low-environmental-impact alternatives to currently marketed fluids. The study investigates the replacement of traditional scroll compressors with small-scale turbo compressors in brine-to-water vapor compression heat pump cycles operating at three power levels — 5 kW, 15 kW, and 100 kW — representative of small domestic, light commercial, and large commercial applications. The analysis is based on numerical simulations of two single-stage heat pump configurations: one equipped with a scroll compressor and the other with a turbo compressor. The simulations are performed using a custom numerical environment and a standard thermophysical property database, and incorporate a range of medium- and low-pressure refrigerants: R32, R290, R1234yf, R152a, R134, R1234ze(E), R1336mzz(E), R1234ze(Z), R1233zd(E), and R1336mzz(Z). The turbo compressor is modelled using an experimentally validated inhouse 0D model, while the scroll compressor isentropic efficiency is estimated based on manufacturer performance selection software. The performance of both systems is evaluated under operating conditions defined by the European Standard EN 14825. The TCO is annualized and includes purchase cost, installation cost, and energy consumption over a 20-year lifetime, with a 5% interest rate applied to account for cost discounting. Results suggest that the adoption of a turbo compressor enables significant TCO reduction, mainly due to higher Seasonal Coefficient of Performance (SCOP) and smaller, more efficient heat exchangers. This improvement is driven by the turbo compressor’s ability to modulate power output and maintain high isentropic efficiency across different operating conditions. In addition, the use of gas bearings eliminate the need for oil lubrication, which prevents refrigerant contamination and enhances heat exchanger performance