Tilden Chao ’23 has spent the last year unraveling a climate change mystery by cataloging the planet-warming refrigerants used in Yale dining halls, power plants, lab equipment and even dormitory refrigerators.
Refrigerant gases such as hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) are an underreported contributor to global warming. In fact, these invisible, odorless gases are “climate super-pollutants”, with thousands of times the global warming potential of carbon dioxide. They leak from refrigerators and other equipment during their lifetime and can suddenly spread into the atmosphere if not disposed of properly when the equipment is removed.
With support from Yale’s Office of Facilities and Office of Sustainability, Tilden and seven other undergraduates set out to catalog every major piece of equipment that uses refrigerants on campus. After a year of painstaking detective work, they compiled their findings into a database that the university can use to get a more complete picture of its greenhouse gas inventory, which will help achieve the goal of Yale to achieve zero carbon status by 2050.
“Tilden’s leadership and dedication have had an extremely positive impact on our office’s mission to build a more environmentally and socially responsible Yale,” said Ginger Chapman, director of the Office of Sustainability. “It makes Yale aware of contributions to our greenhouse gas emissions that we weren’t fully accounting for.”
“We can’t manage what we can’t measure.”
Refrigerant leaks currently account for less than 2% of total greenhouse gas emissions reported by Yale. This amount includes only certain types of refrigerant emissions (HFC refrigerants and those from large units such as power plant chillers), which are reported in accordance with standards established by the World Resources Institute (WRI), the standard worldwide enabling companies and organizations to measure and manage their greenhouse gas emissions.
What Tilden and his comrades have helped identify are literally thousands of smaller units – as well as those using HCFCs and other types of refrigerants – that are not required to be subject to a report as part of the WRI, but are essential to a full understanding of Yale. greenhouse gas emissions. When he compiled them, Tilden found that including these units more than doubled the proportion of refrigerants in the greenhouse gas inventory, to 4.3%.
Ice buildup on a compressor rack containing refrigerant on the roof of one of Yale’s residential colleges. A refrigerant leak likely caused this ice buildup. Photo by Tilden Chao
Additionally, as Yale moves away from fossil fuels and toward electric refrigerant-based systems to heat and cool buildings, the proportion of refrigerants in the university’s greenhouse gas inventory will increase dramatically. That makes careful management of these systems all the more important, says Julie Paquette, director of engineering and energy management at the Facilities Office, who oversaw Tilden’s research.
“Heat pumps are a very important aspect of Yale’s decarbonization strategy,” says Paquette. “We have been using refrigeration and electrical equipment to cool buildings for many decades, combined with fossil fuel-based heating equipment. As heat pumps are adopted both for cooling and the heat buildings, we will increase the amount of refrigerant we have on campus and the likelihood of leaks. »
Paquette explains that Yale will proactively remove refrigerants with the highest global warming potential and replace them with low-impact refrigerants. At the same time, Yale is exploring improved systems to monitor and repair refrigerant leaks when they unavoidably occur, to minimize fugitive emissions.
Creating the Refrigerant Database required Tilden and other students to explore dining halls, rooftops, and mechanical rooms, taking photos of labels containing information about the type and amount of refrigerant used. in a given device. When the units didn’t have labels, Tilden dug up old user manuals using an app called Bluon to find the relevant data. With support from the Office of Sustainability, Tilden even became an EPA Section 608 Certified Refrigerant Manager and learned how to use refrigerant detection sensors to “sniff out” leaks.
The refrigerant gas in this 25-pound bottle, sourced from a Yale residential dining hall, is 1,273 times more powerful than CO2 pound for pound. If all of its contents were released at once, it would have an impact equivalent to 15 metric tons of CO2. Photo by Tilden Chao
Tilden is energized by the work because he knows what’s at stake. This month, the Intergovernmental Panel on Climate Change noted that HFC refrigerants are the fastest growing climate pollutant. fast in the world. Gradually reducing these emissions will be an essential part of meeting the Paris Agreement’s 1.5 degree warming target.
R-134a, a commonly used HFC refrigerant, is 1,430 times more powerful than CO2 as a greenhouse gas. To put that into perspective, Yale’s West Campus Power Plant emitted enough R-134a last year to have the same climate impact as burning more than 1.4 million pounds of coal.
Statistics like these could inspire doom for many, but Tilden sees an opportunity. “I’m really excited about Yale’s net zero carbon goal,” he says, “but until we have an incomplete understanding of the refrigerant problem, we’ll never achieve true net zero. We can’t manage what we can’t measure.
Solutions and Obstacles
The problem is less the refrigerant gases themselves than our inability to manage them, says Tilden. While there is no leak-free refrigerator, there are ways to minimize leaks as well as alternative refrigerants that pollute far less when they leak.
“The stark reality of climate change is that the very chemicals that will help billions of people adapt to extreme heat are themselves driving the climate crisis,” Tilden observes. “We must be prepared to manage an ever-growing bank of these harmful refrigerant gases.”
Detection systems like those used by some grocery stores offer a potential solution, with some systems able to alert technicians to potential leaks before they even occur. Refrigerants can also be recovered from obsolete equipment and reused, reducing the demand for virgin gases. Finally, some equipment can be equipped with new refrigerant blends that have half the global warming potential of the most common HFCs.
The Yale Refrigerants Initiative is the first such project in the country, and Tilden has shared its research as a best practice with other universities in the Ivy Plus Sustainability Consortium. He also studies global cooling and refrigerant gases at the Yale Carbon Containment Lab.
“Refrigerants are a surprisingly exciting and powerful solution to climate change,” says Tilden. “With the information we’ve gathered here on campus, we can develop new, targeted solutions for a problem we previously didn’t know existed on this scale.”