22 May 2008
The intention of this R&D project is the development of an electrical driven heat
pump with the refrigerant CO2 for the retrofit marked, which is reaching the demands of
existing houses. The main barriers for using heat pumps in old buildings for the retrofit are
the high inlet temperatures of 70 °C up to 90 °C. This is too high for the present heat pumps.
The designed heating system with heat pump and electric heater permits to cover the
heating demand of a house with 20 kW max. capacity at design temperature. The Seasonal
Performance Factor (SPF) target is 3.3. Space heating (90%) and tap water heating (10%)
will be realised with an economiser cycle and hot gas injection in the compressor. The
bivalent point is fixed at -7 °C (13 kW). The annual energy consumption of the electrical
heater amounts to 5% (calculation result).
Also a prototype of a CO2 compressor with the necessary capacity, high efficiency, high
condensing temperatures, a perspective of low production costs and with a long lifespan will
be developed during this project.