23 September 2011

EVALUATING ENVIRONMENTAL BENEFITS OF GROUND SOURCE HEAT PUMPS: THE STRENGTHS AND WEAKNESSES OF COP AND SCOPi


In North America, many governments and utilities base their grants and financial
assistance program on the theoretical coefficient of performance (COP) of heat pumps at a
fixed temperature as determined by test carried under CAN/CSA-C13256 or CSA C748-
94(2005). In Canada a thorough analysis of ground source heat pump (GSHP) design also
indicates that many designers tend to undersize their systems, relying on back-up energy
systems for part of the annual heating loads. This tendency to undersize systems reflects C-
448 Standard’s recommendations to design at between 70% and 105% of design heating
load. Independent studies conducted on Canadian residential GSHP systems concluded that
the seasonal coefficient of performance (SCOP) show total-system performances on average,
15% below the laboratory tested applicance COP. We conclude that simple claimed energy
efficiency and environmental advantages reflect wishful thinking based on faulty logic about
COP. This paper presents technical analysis between the theoretical COP of the heat pumps
and the SCOP of installed systems under real life operating conditions.