Influence of system design on the efficiency of heat pump systems for space conditioning (key note)

Paper in proceeding, 2011

Heat pump research often focuses on the efficiency of the heat pump per se. However, it is usually easier to raise overall efficiency by improving the external systems. This paper discusses the effect on system efficiency of the total drive energy for space conditioning in a Nordic climate. Results show that fan energy for air distribution often surpasses drive energy for chillers and that Specific Fan Power (SFP) must be very low, even with free-cooling by outdoor air, to make air distribution competitive in relation to liquid-based distribution. It is currently more efficient to increase room-cooling capacity by reducing supply-air temperature than by increasing air flow. Typically the fan drive power must increase more than the compressor drive power will drop if a given capacity increase is achieved by increased air flow. The cooling system coefficient of performance will decrease even if the heat pump coefficient of performance increases.