Feasibility Study of a Combination Geothermal and Solar Thermal Heating System in a Heating Dominant Climate
Renewable energy technologies are becoming more attractive and gaining more attention as the world becomes increasingly aware of the negative impacts of global warming and greenhouse gas (GHG) emissions. Two such emerging technologies are geothermal heat pumps (GHP) and solar thermal heating which can be used for heating and cooling of buildings. GHP systems are a well-studied technology that have been proven to be more efficient than traditional air-source heat pumps for space conditioning of buildings. Solar thermal heating has become more common as a way to heat domestic hot water (DHW) in homes, but the two technologies are not often combined. This study presents the findings of combining an open-loop GHP with 100 ft2 of flat plate solar thermal panels and a 5,655-gallon sensible water storage tank for space heating and DHW heating needs of a residential home in Bozeman, MT, USA. The goal of this system was to use energy from the solar panels and storage tank first to decrease pumping energy from the GHP well. The open loop system was designed to be a backup system to the solar thermal panels and sensible storage tank. An actual home was modeled to determine potential energy and cost savings of such a system compared to a traditional propane boiler. Then, a case study was performed on the installed system from January to June 2021. Results obtained from April 2nd to June 5th, 2021 indicated that the combination system supplied all necessary heat, and that heat was supplied from the thermal storage tank 55% of the time. This represents a savings of 330 kWh of energy and $36 compared to operating just the open loop geothermal system. From April 2nd to June 5th the combination system consumed a total of 2,510 kWh of energy and
cost $274 to operate. Based on data obtained, there is significant potential for energy savings compared to a propane boiler, however only small potential for cost savings.
Nicole Harvey has a BS in Mechanical Engineering from South Dakota State University and an MS in Mechanical Engineering from North Carolina State University. She has worked as an HVAC and plumbing engineer as well as performed ASHRAE Level 1 and Level 2 energy audits for industrial facilities. Currently she is working as a mechanical engineer for Aspen Springs Consulting where she is helping to design sustainable cannabis facilities. She is passionate about renewable energy systems and energy efficiency and hopes to help reduce greenhouse gas emissions and create a sustainable future. In her free time Nicole loves to be outdoors rock climbing, skiing, hiking, and rafting.