Combined solar thermal and ground source heat pump system

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 were estimated. TRNSYS, a system simulation software tool, was used to model the yearly performance of conventional GSHP as well as the proposed hybrid GSHP system. The house was equipped with data monitoring system which was installed to read and record fluid flow, temperature and electricity consumption in different components of the system. The actual yearly data collected from the site was examined against the simulation results. In addition, a sensitivity analysis has been carried out to determine the relationship between the solar collector area and the ground loop exchanger (GHX) length. It was shown that the ratio of GHX length reduction to solar panel area of 4.7 m/m2, results the optimum ratio which corresponds to 32m GHX length reduction with 6.81m2 solar collectors area.    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 loop heat exchanger length. Combining three solar thermal collectors with total area of 6.81m2 to the GSHP system will reduce GHX length by 15% (from 222m to 188m). The system malfunctioning in the cooling season was also detected and options for fixing the problem were presented. Sensitivity analysis was carried on different cities of Canada and results were demonstrated that Vancouver, with mildest climate compared to other cities, was the best candidate for the proposed solar hybrid GSHP system with 7.64 m/m2 GHX length reduction to solar collector area ratio. 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 GSHP. The net present value of the proposed hybrid system and GSHP system were estimated to be $44,834 and $41,406 respectively.