Grantee Research Project Results
Final Report: Component Optimization for Improved Refrigerant Recovery
EPA Contract Number: 68HERC23C0021Title: Component Optimization for Improved Refrigerant Recovery
Investigators: Nasuta, Dennis
Small Business: Optimized Thermal Systems, Inc.
EPA Contact: Richards, April
Phase: I
Project Period: December 1, 2022 through May 31, 2023
Project Amount: $99,945
RFA: Small Business Innovation Research (SBIR) Phase I (2023) RFA Text | Recipients Lists
Research Category: SBIR - Air and Climate , SBIR - Sustainability , SBIR - Water , SBIR - Homeland Security
Description:
Most of the chemical refrigerants currently used in heating, ventilation, air conditioning, and refrigeration (HVAC&R) have global warming potential (GWP) values thousands of times higher than that of carbon dioxide. An increasing focus on curbing the climate impacts of these refrigerants has led to global cooperation in the form of the Kigali Amendment to the Montreal Protocol. In the US, ratification of the Kigali Amendment and the implementation of the American Innovation and Manufacturing (AIM) Act have set specific timelines to phasedown the use of hydrofluorocarbon (HFC) refrigerants. As these policies limit the consumption of new HFCs, the industry will adopt new refrigerants with lower GWPs in new products over the coming years. However, the presence of high-GWP refrigerants in existing products presents both a significant environmental threat and economic value to OEMs and service technicians facing coming HFC scarcity.
Today, EPA-certified refrigerant reclaimers report reclaimed refrigerant quantities less than 2% of the annual consumption of HFCs (EPA, 2022), indicating that a large portion of refrigerants are leaked, illegally vented, and/or stored/utilized in channels that don’t require reporting to the EPA. The significant environmental and economic value of refrigerants will continue to grow in coming years; ensuring proper recovery and reclamation or destruction is critical to ensuring compliance with EPA’s policies and meeting global objectives for climate change mitigation.
EPA’s 2023 SBIR Phase I BAA sought “technologies for improved recovery of refrigerant from air conditioning and refrigeration equipment”. The recovery process is often time-consuming and costly for technicians. Although legally prohibited, enforcement actions on individual contractors venting refrigerants are relatively uncommon. Recovery adds significant time to a service job and reclaimers typically offer minimal incentive for returned refrigerants. As a result, some technicians illegally vent refrigerants; others incur significant cost, which is passed onto the consumer, to properly recover them. Solutions that can make refrigerant recovery easier, faster, and more lucrative will incentivize HVAC&R technicians to recover refrigerant during equipment servicing and end of life. The project effort summarized herein seeks to develop a deeper understanding of the factors influencing the refrigerant recovery process in order to develop new solutions that can significantly reduce recovery time, thereby improving the economics of recovery for all parties.
The project consists of three key elements: experimental testing, modeling and simulation, and engineering design. Experimental work focused on identifying the key factors that influence refrigerant recovery time to provide guidance into areas for improvement. This experimental data is useful for model validation and is generally valuable to industry and policymakers in providing quantitative information about recovery speeds, behaviors, and efficiency. Physics-based models were developed to build a deeper understanding of the physical processes behind recovery and inform the product design process. Finally, product ideation and engineering design led to the development of several product concepts with the ability to significantly reduce refrigerant recovery times.
Summary/Accomplishments (Outputs/Outcomes):
Experimental work explored the impacts of recovery machine design, flow restrictions, recovery tank temperature/pressure, and ambient temperature on recovery speed. A representative residential 3-ton split air conditioner was installed in an environmental chamber and repeatedly charged with and evacuated of refrigerant. Recovery machines from two manufacturers were compared and the more advanced model consistently reduced recovery time by ~31% compared to the basic model. Removal of the restrictive Schrader cores built into the AC unit reduced recovery time by 34~38% by reducing the compressor pressure lift and raising the suction density of refrigerant. Recovery typically took ~45% longer on a hot, 95°F day than a moderate 67°F condition. The high pressure of the recovery tank on hot days significantly slowed the recovery process; cooling the recovery tank in ice before recovery reduced the required time by ~40% on 95°F days. On average, about 50% of recovery time was spent capturing the last 5% of refrigerant mass, and the process of purging, connecting, and disconnecting hoses and equipment resulted in the loss of ~3.5% of refrigerant charge on average.
Experiments revealed that with conventional technology, recovery times can already be reduced dramatically from what is currently typical and many project objectives could be met without the introduction of a new product. Experiments demonstrated that using a better machine, removing Shrader cores and cooling the recovery tank reduced recovery time by as much as 73% overall. Outreach and education about best practices could help some technicians improve their recovery profitability. Eliminating Schrader cores at the factory or replacing them with high flow valves could save technicians valuable time. Technicians currently receive negligible benefits (and in some cases pay a fee) for returned refrigerants; new programs through OEMs and reclaimers that provide payments closer to the virgin refrigerant cost (or social cost of carbon) would greatly incentivize technicians to recover all available refrigerant.
Conclusions:
Refrigerant recovery machines are primarily comprised of a compressor and a heat exchanger. Just like HVAC systems which contain the same components, recovery machines can be optimized to increase performance by manipulating the compressor and heat exchanger design parameters. Testing and modeling confirmed that the current performance bottlenecks were not solely thermal, but primarily driven by compressor performance. To improve speed, a larger compressor would be required. Today’s machines are limited by the power available through typical 120VAC outlets; the compressors are already as powerful as they can be. To bypass this constraint, a battery-powered recovery machine design with a more powerful brushless DC motor was conceived. The team selected components for two designs that would achieve 2-4x the volumetric flowrate of the current state of the art. Modeling suggests that these designs could reduce recovery time by 44-65%; when Schrader cores are also removed, recovery speeds might decrease as much as 76-88%.
Because the recovery machine market is saturated and most technicians already own machines that do not need to be replaced, an alternative product concept was also developed to provide cooling to recovery tanks. The product can be fitted to existing tanks, does not require replacement of recovery equipment or changes to current practices, and can be recharged nightly in a consumer freezer. This recovery tank cooling device provides a low-cost solution capable of reducing recovery time by more than 50% (>60% if Schrader cores are also removed). These tank coolers can be integrated into insulated storage racks installed in technicians’ vehicles to secure them during transport and maximize utilization of stored cooling capacity.
This research project has led to the successful development of several product concepts capable of significantly reducing refrigerant recovery time. With these time savings, technicians can transform the recovery process from one that costs them money into a profitable activity. The OTS team will continue to pursue the development and commercialization of these products that have the potential to increase the amount of refrigerant recovered in the future. Furthermore, this report establishes new findings about the process of refrigerant recovery that can inform OEMs, technicians, and policymakers. This new information about a rarely-considered topic will help stakeholders with an interest in refrigerant recovery to better understand the underlying physical and economic factors and the opportunities for improvement.
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.