AASHE Campus Sustainability Hub

At the height of the COVID-19 pandemic, many (if not all) universities’ sustainability offices had to reimagine what engaging with their communities looked like and how they’d meet campus sustainability goals in such unprecedented times. However, such challenges did not set back Tilden Chao, Yale College Class of 2023, from engaging his peers and staff sustainability leaders to found the Yale Refrigerants Initiative with a $25,000-grant from the Office of Facilities’ Student Green Innovation Fund.

The YRI operates through the Office of Facilities, Office of Sustainability, and Yale Student Environmental Coalition and is aimed at developing refrigerant management solutions that can be applied to other university campuses. As Yale electrifies buildings on campus, using more refrigerant-based systems such as heat pumps, it is anticipated that the proportion and magnitude of refrigerants in our greenhouse gas inventory will rise significantly. As such, this work is essential so that Yale can account for and plan to mitigate refrigerant emissions on campus. This project is the first of its scale in the country.

The project initially focused on refrigerant emissions from mini fridges in student dorm rooms, until Tilden realized that the biggest culprit was larger equipment used for food services and the thousands of refrigerators and freezers used by Yale’s research community. With support from the Yale Office of Facilities and the Office of Sustainability, a group of Yale undergraduates led by Tilden catalogued almost every major piece of equipment that uses refrigerants on campus. They then compiled their findings into a database that the university can use to gain a fuller picture of its greenhouse gas inventory, and that will help to achieve Yale’s goal of reaching zero-carbon status by 2050. Tilden’s capstone paper, entitled A Roadmap for Lifecycle Refrigerant Management at Yale University, was completed in May 2023, and proposes a five-component strategy to direct Yale’s efforts in reducing fugitive refrigerant emissions to meet Yale’s climate targets.

Reducing fugitive emissions of refrigerant gases such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) will be a significant challenge in reaching Yale’s net zero emissions commitment. Although these gases currently account for only 1.6 percent of the University’s reported scope 1 emissions, deficiencies in past greenhouse gas inventories have led to an underestimate of Yale’s total refrigerant emissions.

Several deficiencies in greenhouse gas reporting standards result in significant underreporting of HFC emissions on campus. First, because CFCs and HCFCs are covered under the Montreal Protocol for Ozone-Depleting Substances rather than the Kyoto Protocol, which covers all other major greenhouse gases, emissions of CFCs and HCFCs are not required to be reported on The Climate Registry, Greenhouse Gas Protocol, and other major emissions reporting platforms. Although the new production of CFCs and HCFCs is prohibited consistent with the Clean Air Act, HCFCs and CFCs continue to be used widely in cooling equipment across campus, particularly in large chiller systems. Yale, like most institutions, opts not to report emissions of these gases.

Second, Yale currently accounts for three major sources of refrigerant emissions in its greenhouse gas inventory: power plant chillers, “non-plant” buildings, and fleet vehicles. Power plant chillers are significant contributors to refrigerant emissions (1,297 metric tons CO2e) given their large refrigerant charge which often totals several tons of gas per chiller. These chillers generate chilled water that is pumped underground to some buildings on campus. These buildings then blow air over the chilled water, producing cold air. Yale calculates emissions using refrigerant purchasing data, with the amount of refrigerant purchased each year as a proxy for how much refrigerant was leaked in that year. Notably excluded from this list are categories of smaller equipment, such as dining hall refrigerators, laboratory cooling equipment, and building air conditioners. Although individual small cooling units do not have a substantial impact on climate, their impact in aggregate can be quite large.

Tilden became interested in refrigerants in high school after reading Project Drawdown, a climate science investigation listing top solutions to climate change and seeing that refrigerants were among the top climate stressors. With a friend, Tilden won a grant from Sustainable Tompkins, a local environmental nonprofit, to work with food retailers in upstate New York to improve the management of refrigerants in their stores. Though he wasn't planning to continue working on refrigerants in college, the Yale Student Green Innovation Fund (SGIF) was initiated during Tilden’s first year at Yale, which created a new opportunity to work on refrigerant management on campus. Initially, the draft project focused on student mini fridges, though Tilden soon realized, with the help of peers and Facilities personnel, that the major refrigerant challenges were in dining halls, laboratories, data centers, and power plants. From discussions with Facilities staff, Tilden determined that the University was unclear on and not fully accounting for the full scope of refrigerant emissions on campus, and that much work remained to be done, starting with a refrigerant inventory.

The Yale Refrigerants Initiative (YRI) is aimed at developing refrigerant management solutions at Yale and phasing down hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) refrigerants on campus, and to better manage both in line with forthcoming EPA regulations. Yale also has robust climate targets which phasing down refrigerants is essential to meet; as such, a primary goal of the initiative is to account for refrigerants in and reduce their share of Yale’s scope 1 emissions.

With support from the Yale Office of Facilities and the Office of Sustainability, Tilden and seven fellow undergrads catalogued every major piece of equipment that uses refrigerants on campus, including air conditioning and refrigeration equipment, between March 2021 and September 2022. This is the first attempt at a refrigerant inventory at an institution of Yale’s size. In the 2022-2023 academic year, the YRI team tested dining hall compressor racks for refrigerant leaks using Bacharach refrigerant leak detection equipment, which detects fluorocarbons in ambient air. These leak detection surveys turned up several leaks, which were then reported to the appropriate stakeholders.

Additionally, Tilden et al. used myriad strategies to gather data for different refrigerant end uses, which included commercial refrigeration equipment in dining halls and cafés, split system air conditioners and rooftop chillers, laboratory equipment, and power plant equipment. This entailed ample time spent by students physically in the basement of dining halls, looking at equipment and collecting data, and remotely, processing data and estimating equipment emissions. Most site visits occurred during the COVID-19 pandemic, and thus the team faced some challenges in accessing buildings and including larger numbers of student volunteers.

Tilden aggregated existing sources of data from refrigerant purchasing logs and equipment surveys, acquiring data for power plant chillers (Sterling Power Plant, Central Power Plant, and West Campus Power Plant) from WSP, the consultant to the Yale Office of Sustainability. To assess commercial refrigeration equipment, Tilden physically surveyed each of Yale’s 14 residential college dining halls, as well as other dining facilities such as the 344 Winchester Central Kitchen, Charley’s Place at Evans Hall, and STEEP Café at the Yale Science Building. At each location, he collected data on equipment nameplates, including model name, serial number, refrigerant species, and refrigerant charge with the help of Yale Hospitality and refrigerant technicians at Commercial Kitchens. He estimated leakage emissions from all equipment in the inventory in line with refrigerant leak rate parameters set by the California Air Resources Board. He then added up expected emissions from every piece of equipment to determine estimated emissions for that entire end use and added up total emissions in each end use to estimate total unaccounted refrigerant emissions at Yale.

The Office of Facilities and the Office of Sustainability were the primary advisors to the project, though support was also received from Environmental Health and Safety (EH&S) staff. The Yale Carbon Containment Lab also played a supporting role throughout the project.

In 2020, Tilden wrote a grant proposal to the Student Green Innovation Fund and founded the Yale Refrigerants Initiative, with support from HVAC technicians in the Yale Office of Facilities. Between March 2021 and September 2022, Tilden and a group of Yale undergraduates conducted an inventory of Yale’s air conditioning and refrigeration equipment. During this time, the group completed a working inventory of refrigerant-containing equipment at Yale, organizing and presenting at an AASHE webinar in 2021 and to a group of over twenty US research institutions in 2022, and detecting for leaks in Yale dining halls and reporting them to the Office of Facilities. In 2023, Tilden graduated from Yale leaving a legacy by way of the YRI and his continuing work through the Yale Carbon Containment Lab (CC Lab).

Funding for the project came from the Office of Facilities’ Student Green Innovation Fund, a $100,000 grant fund which provides awards to student projects that can measurably reduce Yale’s greenhouse gas emissions. Tilden applied for this funding in the winter of 2020 and received funding (in the range of ~$25,000) shortly thereafter.

First, the YRI team completed a working inventory of most refrigerant-containing equipment at Yale. This undertaking showed that Scope 1 emissions of refrigerants at Yale have been significantly underreported (by more than half) in previous emissions inventories published via The Climate Registry. One major conclusion is that refrigerants compose at least 3.3 percent of the University's Scope 1 emissions tab, compared to previous estimates of 1.6 percent. Small equipment that is traditionally excluded from institutional refrigerant inventories has an exceptionally high greenhouse gas impact. Estimated refrigerant emissions from the University's laboratory freezers and refrigerators (when aggregated) were the single-greatest refrigerant emissions source on campus. Second, Tilden spent time (with support from partners throughout Facilities) educating about refrigerants and discussing pre-publication research with sustainability managers at other universities. This work included organizing and presenting during an AASHE webinar in 2021 and presenting to over twenty US research institutions 2022. His presentations were well received and led to the beginning of similar efforts at the University of Virginia, University of Chicago, and Notre Dame.

Third, Tilden and fellow YRI team members occasionally found evidence of refrigerant leakage, which in each case was immediately reported to the Office of Facilities. This regular leak detection effort is unusual and unprecedented among universities, which typically check equipment for refrigerant leaks only once per year, if at all. Outcomes from YRI’s research have not yet been translated into concrete actions or commitments from the University but have significantly raised the profile of refrigerants among the issues of campus environmental concern. The refrigerant inventory in particular lays the groundwork for improved procurement and maintenance practices for cooling equipment.

Tilden’s capstone paper, entitled A Roadmap for Lifecycle Refrigerant Management at Yale University (completed May 2023), documents refrigerant emissions composing at least 3.3 percent of campus scope 1 emissions, compared with current estimates of 1.6 percent. The data will support the development of a formal strategy to improve refrigerant management practices at Yale. Tilden proposes a five-step strategy to improve lifecycle refrigerant management practices on campus, including committing to procuring climate-friendly technology, reducing refrigerant leak rates, and improving reporting of refrigerants in the University’s public-facing greenhouse gas inventory.

Recommendations for pricing carbon/refrigerants also came of Tilden’s research in the form of a published white paper (White Paper on Pricing Refrigerants | Yale Refrigerants (yalerefrigerantsinitiative.org)). Recent technology pilots with refrigerant management startups may provide greater insight into the connections between refrigerant leaks and energy efficiency. Several pilots are forthcoming at Yale, including on large compressor racks serving food preparation facilities and data centers.

Tilden found the greatest challenge of this project to be accessing all campus locations with equipment containing refrigerants. As there are refrigerants everywhere, from car air conditioners, to dehumidifiers in classroom basements, Tilden determined that future efforts to manage refrigerants would benefit from a student team working closely with building managers across campus.

One broadly applicable lesson from Tilden’s efforts is that one can learn a lot about emissions and environmental issues by conducting on-site visits and measuring whether assumptions made hold up. In the case of refrigerants, the students learned that their initial assumptions weren't true, as their in-person visits revealed much more equipment using refrigerants than Yale had been accounting for.

• Tilden Chao | Yale University

• Link: Yale Refrigerants Initiative