Low Cost, Large Diameter, Shallow Ground Loops for Ground-Coupled Heat Pumps
Facilitating the design, installation, and market acceptance of low-cost ground heat exchangers.
The project is complete. Current GCHP model is improved by enabling better prediction of fluid temperatures in the bore. The simulated results show good agreement with field and laboratory data. This provides more accurate estimates of energy use for the system. The model was shared at ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) conferences. ASHRAE's guidelines on heat pumps and other measures were considered a primary reference in the industry. The recipient presented its model to the CEC's Building Standards Office and discussed updating Title 24's models. The Building Standards Office will include improved performance maps which could accommodate ground couple heat pumps in future versions of the Residential ACM Reference Manual. The project team intents to submit a Statewide Utility Codes and Standards Enhancement Report in the next Title 24 update.
This project is researching shallow (20-30 feet deep) and large diameter (2-3 feet diameter) helical coil, ground heat exchanger designs for ground source heat pumps. This project seeks to fill the current informational void with the materials and tools needed to eliminate the risks involved with engineering this new technology into homes. To this end, the project analyzed the performance of different designs of large diameter shallow bore GHEs, produced a calibrated model that can predict the performance of these GHEs and incorporate them into industry-standard design tools, and produced the materials that the industry needs to confidently move forward with the deployment of this technology. Also, a draft compliance option was prepared to facilitate this technology's incorporation into the California Energy Commission's residential energy compliance process. Determining a path of compliance of this technology will allow it to receive proper credit for incentives under the California Advanced Home Program, and will give policymakers the information they need to make policy decisions that will encourage the adoption of this technology
Improve market conditions for GCHPs in California;
Develop and disseminate tools
Increased use of GCHPs would eliminate noisy and visually unappealing outdoor condensing units. Also, GCHPs could improve comfort for residents compared to forced air systems.
This project seeks to reduce the cost of GHEs for heat pumps. Affordable GCHPs may result in lower utility costs for heating and cooling, lower maintenance costs, and improved system reliability compared to forced air systems. Estimated annual energy savings is over 67 billion BTU, assuming 40,000 single family homes built annually and 10% of new homes equipped with GCHPs. Annual electric savings from cooling efficiency in new homes is roughly 1.2 million kWh. For a 2100 sq ft home and a 2 ton system, and comparing the incremental cost for a GCHP system with conventional HVAC system, the annual cost savings per home is $173, when amortized over 30 years with tax credits.
If ground coupled heat pump systems were installed on all new single-family homes built in 2019, 110,000 homes a year, there would be an 8500 MTCO2e GHG reduction.