KC-03-03-3 -- Assessment of the Viability of Hybrid Geothermal Heat Pump Systems with Solar Thermal Collectors

Closed-loop, geothermal heat pump (GHP) systems installed in buildings with large annual imbalances in the ground load may utilize hybrid systems to reduce first costs and improve system performance. Hybrid GHP systems employ supplemental components to handle a portion of the building thermal loads, permitting the use of smaller, lower-cost borehole fields. This study presents a system simulation approach to assess the feasibility of hybrid GHP systems with solar thermal collectors in heating-dominated buildings. An actual school building is modeled with typical meteorological year weather data for six U.S. cities with varying climates and insolation. Conventional and hybrid solar GHP systems are sized for each case for 20 years of operation, with a minimum design entering fluid temperature of 32°F (0°C). A life-cycle cost analysis indicates that the drilling costs must exceed the range of $6/ft to $10/ft ($19.68/m to $32.81/m) for hybrid solar GHP systems to be economically viable.

Units: Dual