22 May 2008

HEAT PUMP PERFORMANCE SENSITIVITY TO HORIZONTAL AND VERTICAL COLLECTOR CONFIGURATIONS IN A MARITIME CLIMATE REGION


Ground source heat pumps extract heat from the ground surface layer using either a horizontal or vertical collector. While numerous studies have characterised heat pump performance in continental climates few have focuses on maritime climates. This experimental study was carried out in Ireland’s maritime climate and it utilised two identical, 15 kWth heat pumps. One heat pump was connected to a 430m² horizontal collector while the other was connected to a series of three, 100m deep, single U-tube vertical collectors. The goals of this study were to identify the quantifiable differences in heat pump performance that could be attributed to either a) collector configuration; vertical or horizontal, b) climate; continental or maritime, c) operating environment; standard laboratory test environment or actual application, and d) use conditions that mimic either typical or extreme duty cycles. Experimental results are presented for 2007 and 2008 and the data highlights collector sensitivity to climate and use conditions along with ground temperature recovery rates
depending on collector configuration. This study will aid the development of guides to support heat pump collector design based on measured performance under maritime climate conditions. Heat pump COP variations of between 5.1 and 2.9 were recorded with brine output temperatures of between 35°C and 50°C.