Feasibility of combined solar thermal and ground source heat pump systems in cold climate, Canada

Abstract This document presents a study for examining the viability of hybrid ground source heat pump (GSHP) systems that use solar thermal collectors as the supplemental component in heating dominated buildings. Loads for an actual house in the City of Milton near Toronto, Canada, were estimated. TRNSYS, a system simulation software tool, was used to model yearly performance of a conventional GSHP system as well as a proposed hybrid GSHP system. Actual yearly data collected from the site were examined against the simulation results. This study demonstrates that hybrid ground source heat pump system combined with solar thermal collectors is a feasible choice for space conditioning for heating dominated houses. It was shown that the solar thermal energy storage in the ground could reduce a large amount of ground heat exchanger (GHX) length. Combining three solar thermal collectors with a total area of 6.81 m2 to a GSHP system will reduce GHX length by 15%. Sensitivity analysis was carried out for different cities of Canada and resulted that Vancouver, with mildest climate compared to other cities, was the best candidate for the proposed solar hybrid GSHP system with a GHX length reduction to solar collector area ratio of 7.64 m/m2. Overall system economic viability was also evaluated using a 20-year life-cycle cost analysis. The analysis showed that there is small economic benefit in comparing to the conventional GSHP system. The net present value of the proposed hybrid system based on the 20-year life-cycle cost analysis was estimated to be in a range of 3.7%–7.6% (or $1500 to $3430 Canadian dollar) lower than the conventional GSHP system depending on the drilling cost.