Professor Kripa Varanasi, a mechanical engineer from MIT, experienced firsthand the escalating severity of global warming in June 2024 when he landed in New Delhi. The capital of India was gripped by a scorching 104-degree Fahrenheit heat, a phenomenon that would intensify to nearly 122 F during the day throughout his conference visit. This extreme heat, far removed from the climate of his youth in India, served as a profound catalyst, inspiring him to confront the urgent global challenge of thermal discomfort and its devastating consequences. His personal experience underscores a critical, increasingly widespread issue: the desperate need for accessible and sustainable cooling solutions, particularly in the world’s hottest and most vulnerable regions.
The Genesis of a Critical Initiative: Addressing a Looming Crisis
The intense heat Varanasi encountered is not an isolated incident but a symptom of a rapidly warming planet, where heatwaves are becoming more frequent, longer, and more intense. The World Meteorological Organization (WMO) reported that 2023 was the hottest year on record, with global average temperatures 1.45 degrees Celsius above pre-industrial levels, nearing the critical 1.5 C limit. Such conditions disproportionately affect populations in the Global South, where economic constraints often limit access to conventional, energy-intensive cooling technologies. This dire reality spurred the MIT Climate Project to launch its Critical Cooling initiative, requesting proposals for innovative, sustainable solutions to combat heat stress.
The initiative, championed by Christoph Reinhart, the Terri and Alan Spoon Professor of Architecture and Climate and head of MIT’s Sustainable Design Lab (SDL), emerged from a collaboration between SDL and Harvard’s Human Rights Entrepreneurs Clinic. Reinhart articulated the core philosophy: “The term ‘critical cooling’ stems from a collaboration between SDL and Harvard’s Human Rights Entrepreneurs Clinic. It is motivated by the fact that climate change increasingly causes heat fatalities, primarily among vulnerable populations, who lack access to active cooling. The impact that MIT can have by ‘cooling people, not spaces’ is enormous.” This humanitarian perspective shaped the grant program, which provided seed funding totaling $450,000 for six months to four teams exploring groundbreaking approaches. The projects, now completed, have all demonstrated significant promise and are actively pursuing further development.
A Collaborative Framework for Global Impact
To ensure the solutions were not only scientifically sound but also practically applicable and scalable, the MIT teams collaborated with the Abdul Latif Jameel Poverty Action Lab (J-PAL). Led by Senior Policy Manager Andre Zollinger on J-PAL’s side, this collaboration began with a workshop that convened a diverse group of stakeholders, including representatives from the World Bank, leaders from the Global South, industry experts, and engineers brimming with innovative ideas. This multidisciplinary approach was crucial for grounding the research in real-world needs and fostering pathways for eventual implementation.
Liana Frey, a managing director at the MIT Climate Project, confirmed the success of these initial endeavors, noting that all teams made substantial progress, with most producing initial prototypes. "We’re continuing to look at different ways of proceeding with the work," Frey stated, signaling ongoing commitment to nurturing these promising concepts into viable solutions. The urgency is undeniable; as Frey emphasizes, "There are a lot of people interested in this heat-stress question. It’s just becoming more and more urgent."
Pioneering Solutions for a Warming World
The four MIT-led projects represent a multi-pronged attack on the cooling crisis, each offering a unique technological pathway to mitigate heat stress while addressing the environmental footprint of traditional cooling systems.
1. Personalized Cooling: Professor Kripa Varanasi’s Wearable Solution
Inspired by his experiences in India, Professor Varanasi spearheaded a project focused on "cooling people, not spaces." His team developed a proof-of-concept prototype for a wearable personal cooling system, drawing inspiration from natural biological cooling mechanisms, such as an elephant’s ability to dissipate heat through its large ears to cool its blood. This innovative device is designed to be highly energy-efficient, consuming only about 33 watts, a stark contrast to the roughly 1,000 watts used by a typical room air conditioner.
The economic implications of Varanasi’s device are particularly compelling for the Global South. While the prototype, using U.S. materials, would cost around $20, Varanasi estimates that local sourcing and manufacturing in India could drive the cost down to less than $1 per unit. This affordability opens up transformative possibilities. Governments could procure and distribute these garments on a large scale to vulnerable communities. Local entrepreneurs could establish charging stations, providing income opportunities while ensuring sustained use. Furthermore, local businesses could emerge to manufacture the systems, fostering economic growth and self-sufficiency. The washable nature of the garments, with the cooling material separable, ensures hygiene and longevity. Such a system could offer immediate relief, enabling individuals to at least achieve a good night’s sleep even amidst extreme heat, which has significant health and productivity benefits.
The proof-of-concept, tested with a simulated foot containing a heater, successfully demonstrated the ability to maintain the necessary temperature zone for body cooling. Varanasi highlighted this success: "Our initial prototype that we were able to build with this funding showed that this can become a viable solution." Beyond wearable garments, the underlying material technology could be adapted for other applications, such as cooling sleeping bags. The team overcame a "fundamental science bottleneck" in treating widely available raw materials, making their innovation possible. Varanasi is now actively exploring commercialization pathways, recognizing that "Ultimately, to make anything work, it has to be a business, otherwise good ideas can die. It has to be a good business and a sustainable business."
2. Harnessing Earth’s Coolness: Professor Yet-Ming Chiang’s Subsurface Wells
Professor Yet-Ming Chiang, the Kyocera Professor of Materials Science and Engineering, investigated a radically different approach: leveraging the stable, cooler temperatures found beneath the Earth’s surface. His research explored the potential of subsurface wells incorporating heat-absorbing materials to supply spaces with air significantly cooler than peak ambient temperatures. This method promises substantial energy savings compared to conventional evaporation-compression heat pumps, which are energy-intensive.
The primary aim of Chiang’s system is to provide sustainable cooling for small apartment buildings and single-family homes, particularly in India and other parts of the Global South. By utilizing the Earth’s natural thermal inertia, these systems could offer consistent, low-energy cooling, reducing reliance on expensive and often unreliable electricity grids. This technology could be particularly impactful in regions where conventional air conditioning is unaffordable or impractical due to infrastructure limitations.
3. Revolutionizing Refrigeration: Professor Asegun Henry’s Solid-State Cooling
Traditional air conditioning units frequently rely on hydrofluorocarbon (HFC) refrigerants, which are potent greenhouse gases, often thousands of times more impactful than carbon dioxide over their atmospheric lifetime. Professor Asegun Henry, the George N. Hatsopoulos Professor in Thermodynamics, tackled this environmental challenge head-on by exploring an alternative, energy-efficient approach that eliminates HFCs entirely.
Henry’s innovative system utilizes a cheap, widely abundant solid "caloric" material – specifically, rubber – to achieve a cooling effect. This method exploits the elastocaloric effect, where materials heat up when compressed and cool down when released. Plain water then serves as an efficient heat transfer fluid, further enhancing the system’s environmental profile. The initial target market for this technology includes single-family houses and apartment buildings. However, the scalability of this approach means that larger systems could also be developed to meet the intensive cooling demands of modern data centers, which are significant energy consumers and contributors to heat generation. This solid-state cooling represents a paradigm shift, offering a pathway to refrigeration without the detrimental environmental impact of current chemical refrigerants.
4. Next-Generation Refrigerants: Professor Gang Chen’s Climate-Neutral AC
Professor Gang Chen, the Carl Richard Soderberg Professor of Power Engineering, addressed the twin problems of expensive, power-hungry air conditioning units and their reliance on potent greenhouse gas refrigerants. Beyond the operational emissions, these coolants frequently leak during the lifespan of the device and particularly during disposal, further contributing to global warming.
Chen’s approach is to develop and utilize a completely different kind of chemical refrigerant that has virtually no greenhouse impact. He explained the motivation: worldwide, only about 8 percent of the 2.8 billion people in the hottest parts of the world have access to air conditioning. Yet, current AC systems already contribute between 3 and 4 percent of global warming emissions. With the market for air conditioners projected to triple or quadruple in the coming years, their contribution to global warming will escalate proportionally unless fundamental changes are made.
The Critical Cooling grant enabled Chen to test previously theoretical ideas through experiments. After building and testing three prototypes, he remarked, "I’m not at the stage where I can say that I know this will work." However, the promising experimental results have motivated him to build a further prototype. If this next iteration performs as expected, it could lead to a dramatic global transformation in air conditioning technology, offering a truly climate-neutral cooling solution for homes, offices, and even the demanding cooling requirements of new data centers.
The Urgent Need and Broader Implications
The global context for these innovations is dire. The Intergovernmental Panel on Climate Change (IPCC) projects a significant increase in the frequency and intensity of extreme heat events. The human cost is immense, with heat stress leading to increased mortality, especially among the elderly, children, and those with pre-existing health conditions. Beyond direct fatalities, extreme heat significantly impacts productivity, with studies estimating billions of hours of lost labor annually in regions like India and Southeast Asia. The economic burden extends to healthcare costs and infrastructure strain.
The "critical cooling" projects offer multifaceted implications:
- Health and Well-being: By providing accessible cooling, especially for vulnerable populations, these technologies can significantly reduce heat-related illnesses and fatalities, improve sleep quality, and enhance overall quality of life.
- Environmental Sustainability: The innovations directly address the climate crisis by either drastically reducing energy consumption (Varanasi, Chiang), eliminating potent greenhouse gas refrigerants (Henry), or introducing climate-neutral alternatives (Chen). This is crucial as the world seeks to meet Paris Agreement targets and transition to a low-carbon economy.
- Energy Equity and Access: Many regions in the Global South face energy poverty, with unreliable or unaffordable power grids. Solutions that are energy-efficient, low-cost, or self-sustaining can democratize access to cooling, a basic human need in a warming world.
- Economic Empowerment: Varanasi’s vision of local manufacturing and charging stations exemplifies how these technologies can spur local economies, create jobs, and foster entrepreneurial ecosystems in underserved communities. Reduced energy bills for cooling can free up household income for other essential needs.
- Technological Advancement: These projects are pushing the boundaries of materials science, thermodynamics, and engineering, leading to new scientific discoveries and opening avenues for future innovations in thermal management.
The journey from proof-of-concept to widespread adoption is fraught with challenges, including further research, development, scaling manufacturing, and navigating regulatory landscapes. However, the initial successes of the MIT Critical Cooling initiative offer a powerful beacon of hope. The commitment from the MIT Climate Project and the ongoing interest from various stakeholders signal a sustained effort to bring these life-saving and planet-saving technologies to fruition. As the planet continues to warm, the imperative to provide sustainable, equitable cooling solutions becomes not just an academic pursuit, but a moral and existential necessity.
