EXTRACTION OF TERRESTRIAL HEAT BY A BORE-HOLE HEAT EXCHANGE SYSTEM IN AN ALLUVIAL AQUIFER

Abstract

A Bore-hole Heat Exchange System (BHES) has been originally developed for thermal energy storage in rock basin. One of characteristics of the BHES in Fukui University, is that it was built in an alluvial aquifer, and this was the first such system built in Japan. To evaluate the effect of groundwater flow on the thermal performance of the BHES is an important research theme.
This paper describes, both experimentally and theoretically, the thermal behaviors of the fluid in the bore-hole and the surrounding ground temperature in an aquifer (permeable layer) and in an aquitard (semi-permeable layer). The data indicate that the fluid temperature recovery in the bore-hole after shutting off the circulation pump following a snow melting operation was much more rapid at levels with aquifers than at those without. It is concluded that sensible heat associated with groundwater flow contribute substantially to an effective extraction of terrestrial heat by the BHES.