USU Applied Energy and HVAC Design - Setty Family Foundation Engineering Challenge 2025
Team: Cole Ashton, Maggie Bartholomew, Dax Hatch and Carson Packer
Project Description
Design an innovative system for rejecting heat to domestic hot water and absorbing heat from domestic cold-water systems in residential applications for space heating and cooling involving a ground source heat pump (GSHP) to reduce CO2 emissions.
Our Solution
Our solution is an integrated piping and controls system that captures waste heat from a GSHP to heat incoming domestic city water. The design uses two preconditioning tanks, 3-way control valves, and a PLC to direct the heat to either preheat hot water or dissipate excess energy into cold water. The preheated tank reduces natural gas demand, thus reducing CO2 emissions.
Performance Review
The main requirement for this project is reducing yearly CO2 emissions by 33%. The other requirements and constraints are assumptions and values needed to work towards this goal. After reviews of water usage reports, equipment spec sheets, and extensive mathematical analysis, our design exceeds the required 33% reduction of yearly CO2 emissions by nearly 4%.
| Requirement/Constraint/Goal | Target | Threshold | Predicted Performance | Actual Performance |
|---|---|---|---|---|
| Yearly Carbon Reduction | 33% | 20% | 33% | 36.7% |
| Determine domestic hot water usage parameters | Hot water usage per person per day: 30 gal | Hot water ≥ 20-30 gal/person/day | Hot water usage per person per day: 30 gal | Hot water usage per person per day: 30 gal |
| Determine domestic cold water usage parameters | Cold water usage per person per day: 40 gal | Cold water ≥ 40-60 gal/person/day | Cold water usage per person per day: 40 gal | Cold water usage per person per day: 40 gal |
| Temperature limits for designed system hot water inside tanks | Hot: 120 °F | Hot: 120-140 °F max | Hot: 140 °F max | Hot: 212 °F max |
| Temperature limits for designed system cold water inside tanks | Cold: 35 °F | Cold: 35-50 °F min | Cold: 35 °F min | Cold: 32 °F min |
| Estimate seasonal cooling energy potential | Summer: Cooling 70,056 BTU/day | 72,800 - 109,200 BTU/day | Summer: Cooling 109,200 BTU/day | Summer: Cooling 109,200 BTU/day |
| Estimate seasonal heating energy potential | Winter: Heating 70,056 BTU/day | 72,800 - 109,200 BTU/day | Winter: Heating 83,700 BTU/day | Winter: Heating 83,700 BTU/day |
| Control system working | System works 100% automatically | System works 100% manually | System works 100% automatically | System works 95% automatically |
Design for Theoretical System
The theoretical system integrates a ground source heat pump with domestic hot and cold-water tanks to improve energy efficiency. Heat is rejected to a pre-heated hot water tank and absorbed from a pre-cooled cold-water tank, reducing load on the ground loop. A bypass loop selectively routes flow through either the ground loop or domestic tanks, minimizing compressor work and maximizing heat recovery. This reduces energy consumption and carbon emissions.
Control System Design and Building
The control system simulates the theoretical design by regulating flow paths and operation. A PLC monitors temperature and flow of the incoming water, actuating the pump and 3-way valves. Based on demand, flow is directed to the “hot” bucket or the “cold” bucket.
Control Enclosure Wiring Diagram
The PLC receives flow data from the flow meter and temperature data from the RTD through the transmitter, then uses this information to execute programmed control logic. Based on these inputs, the PLC activates the SSR to control the pump in response to flow conditions and energizes the relay to position the three-way valve according to temperature thresholds.
Conclusion
This project demonstrated the integration of a ground source heat pump with domestic water systems to improve efficiency and reduce emissions. The bypass loop and control system enabled dynamic optimization of heat transfer. We developed skills in HVAC design, electrical wiring, controls integration, and component selection. Future work includes refining control algorithms and expanding testing under varying conditions.
Special thanks to Zac Humes and Nick Roberts for their support on this project.