An analysis of the factors affecting hybrid ground-source heat pump installation potential in North America

Growing demands for space heating and cooling make ground-source heat pump (GSHP) systems a viable renewable alternative. The economic outlook of potential installations can be addressed by hybridizing GSHP systems with an auxiliary system. To better understand optimization factors in sizing hybrid GSHP systems, a series of sensitivity analyses have been performed. Using a rigorous mathematical, computational approach to size hybrid GSHP systems recently published in Alavy et al. (2013), the use of sensitivity analyses has allowed for a better determination of the impact that variations in input parameters have on the performance of GSHPs. A total of five analyses were performed to determine the effects that operating costs, inflation, geographical location within North America, and a seasonality control strategy have on sizing hybrid GSHP systems. The effects inflation of natural gas and/or electricity prices have depends on a building's energy demands. An inflation (deflation) in electricity rates makes hybrid GSHP systems for very cooling (heating) dominant buildings more economical compared to conventional systems. Installations of smaller GSHP systems are more economical when considering time-of-use electricity rates compared to fixed electricity rates, for buildings with long operating hours during off-peak periods. However, downsizing the ground loop system causes an increase in annual operating costs which result in longer payback periods. Similarly, if a building is situated in a location with warmer weather where ground temperatures are thus higher, an optimally designed system will tend to have a shorter ground loop length. By meeting less of the building's peak energy demands (hybrid shave factor) substantially reduces the initial costs of the ground-loop installation.