Design and development of a high temperature heat pump (HTHP) for industrial applications

Abstract

The transition toward renewables and the need for energy decarbonization can be achieved with the electrification of thermal systems. Heat pump technology can play an important role in achieving these objectives and for 2050 it is expected to share 60% of heat generation, (SolarPower Europe; LUT University, 2020). High-temperature heat pumps (HTHPs) can be used as a solution for the decarbonization of heat in the industrial sector for heat demand temperatures above 90 °C, (Arpagaus et al. 2018).

In this study, two prototypes have been developed to analyse and evaluate the technology as a solution. The first is a heat pump part of a demonstration site which was integrated into a district heating loop and was tested under real operating conditions. The temperature of the sink side was limited by external parameters and could not reach the expected temperatures. Therefore, a second HTHP prototype was developed to operate in controlled testing conditions. The lessons learned from the first prototype were implemented in this prototype including the usage of an alternative environmentally friendly working fluid.

The demo heat pump was a water-to-water system that used R245fa. It operated under heat source conditions between 31.2 to 40 °C, and on the sink side, the temperatures were limited to 54.5 °C. It delivered heating capacity up to 43.7 kW and its COP ranged from 5.3 to 6. The saved emissions during one year of operation resulted in 1.44 tnCO2/yr.

The HTHP prototype was tested with R1233zdE under laboratory conditions. The heat source temperatures ranged from 40 to 70 °C and delivered outlet temperatures up to 123.4 °C. Its heating capacity ranged from 18.8 to 39 kW resulting in COP values between 2.5 and 4.5. The maximum isentropic and volumetric efficiencies resulted in 75 % and 85 % respectively, for pressure ratios from 4.2 to 9.

As a replacement of a gas boiler the HTHP showed different payback periods depending on the operating conditions, it resulted in values between 2.3 years (W60/W90) up to 3.4 years (W60/W110). However, the CO2 emissions saved by the actual HTHP replacing a gas boiler resulted in very high percentages of up to 85 % for W60/W80 and 37% for W40/W100 operating conditions

Date of Award	Oct 2023
Original language	English
Supervisor	Caterina Brandoni (Supervisor), Ming Jun Huang (Supervisor) & Nikhilkumar Shah (Supervisor)