23 September 2011

HIGH EFFICIENT HEAT PUMPS FOR SMALL TEMPERATURE LIFT APPLICATIONS


Today, one of the most promising type of heating system for achieving significant
primary energy savings in heating of buildings is a heat pump. Their efficiency as measured
by the coefficient of performance (COP) is closely related to the inner temperature lift, i. e.
the temperature difference between condensation and evaporation. The potential for highly
efficient systems is not fully exploited as standard heat pumps are designed for large lifts of
30–60 K. The integration of small temperature lift heat pumps in efficient overall heating
systems leads to a considerable reduction in the use of primary energy and operating costs.
The development of efficient heat pumps for small temperature lifts requires a new approach
in the design and selection of the components. In order to demonstrate the improved efficiency, a system for small internal temperature lifts was developed and tested. By using
geothermal heat probes and efficient heat delivery and supply systems a COP above 9 can
be achieved for a temperature lift of 20 K. The heat pump can also be employed as a highly
efficient chiller for building cooling. For an evaporation temperature of 15°C, the cooling COP
is 11.5 at a temperature lift of 12.5 K.