30 May 2005
A transcritical CO2 heat pump prototype for a combined space and hot water heating system for residential
European-style low-energy-houses has been designed, built and tested. The goal of the project was
to verify the potential of the CO2-heat pump process in such an application and to gain experience with
the CO2-heat pump for later commercial realisation.
In this report the heat pump performance data are presented. The heat pump was implemented in a
typical heating system of a European-style low-energy house which consists of a hot water supply, a heating
system for floor and/or radiator heating system and a room ventilation facility. The heating system
was modified to account for the characteristic performance losses of the transcritical heat pump at heat
sink inlet temperatures above approximately 25-30°C. Design aspects of the heating system and overall
system performance data are presented. The CO2 heat pump was found to be capable to significantly improve
the overall performance of the heating system compared to similar systems with subcritical HFC or
propane heat pumps. Based on the experimental results a preproduction prototype of a house heating system
is built and tested. Field tests with the prototypes are going to be carried out to gain more experience
on the system characteristics.