22 May 2008


Although large scale heat pumps have not been implemented in great numbers,
they have the potential to supply a large amount of useable energy. It is thus of interest to
ensure they operate with maximum efficiency. They are mostly operated within large heat
distribution networks.
Pressure and heat loss, temperature differentials in the distribution network as well as in heat
exchangers all have a direct influence on the heat pump’s efficiency. The result of this investigation
has been to define the influences of these factors.
Large variations were found for domestic hot water supply systems. This report compares
two installations as the extremes of the scale. The electrical (charged) energy input per m3 of
domestic warm water varies between 22.5 and 37.3 [kWh/m3] (by comparison an electric only
heating system requires 58.2 [kWh/m3]). This has a direct influence on the CO2 emission
The auxiliary systems, in particular the source side pumps, hydraulic systems etc. are also
important contributors to the overall efficiency of the heat pump. It is not only important to
match flows to capacity but also to utilize more suitable systems for domestic water production.