Performance study and life-cycle cost analysis of a ground-source heat-pump system in a commercial building in Norway.

High-performance systems are a prerequisite for profitable borehole thermal-energy storage. This paper presents performance measures for a system operating at a seasonal performance factor of 4.5 and evaluates the life-cycle costs of the actual and alternative system configurations. Compared to systems using dry cooling and electric or district heating the as-built system represents a profitable investment with internal rates of return of respectively 4.9% and 5.9% over a 50-year life cycle. Consequently, ambient-temperature borehole thermal-energy storage is economically competitive in North-European climates at current prices. [ABSTRACT FROM AUTHOR]