In a world where cooling solutions usually demand massive energy consumption, Dave Borlace highlights a counter-intuitive breakthrough: using the sun's heat to actively cool our homes without electricity. This isn't about solar panels powering an air conditioner; it is about a material architecture that turns sunlight into a refrigerant, potentially solving a critical bottleneck in global food security and climate resilience.
The Physics of Passive Cooling
Borlace begins by acknowledging the paradox of our current trajectory. Citing the International Energy Agency, he notes that while half the world's air conditioners are in China and the US, only eight percent of people in the hottest mid-latitude regions have access to cooling. "By 2050, the IEA projects that around two-thirds of all homes in the world will have an air conditioning system installed," Borlace writes, warning that if this demand is met with fossil-fuel-powered units, we face a feedback loop of rising emissions and heat. The core of his argument is that efficiency alone isn't enough; we need a fundamental shift in how heat is managed. "Current air conditioning technology is incredibly energy hungry... they only transfer heat from one place to another, they don't actually cause heat to leave the overall planetary system." This distinction is crucial. Traditional AC moves heat outside, often making urban heat islands worse, whereas the new technology aims to eject heat entirely.
"Nature's way of keeping us cool is the process of evaporation... and nature also uses radiative cooling to keep the entire planet at a livable temperature."
Borlace explains that the new system, developed by researchers at the Massachusetts Institute of Technology (MIT), merges two natural phenomena: evaporative cooling and radiative cooling. He describes the device as a "triple layer sandwich" that functions even under direct sunlight. The top layer is an aerogel, a porous material that insulates while allowing infrared light and water vapor to pass through. Beneath it sits a hydrogel that provides the water for evaporation, and at the base, a mirror-like layer reflects any remaining sunlight to prevent the device from warming up. "The novel insight that the team has shown here is simply to bring together the three principles of evaporation, radiation, and insulation into a single design architecture to overcome these previous deficiencies," Borlace notes. This synthesis is the piece's strongest intellectual contribution, moving beyond incremental efficiency gains to a structural reimagining of thermal management.
Critics might note that the reliance on water, even in small amounts, could be a limiting factor in the world's most arid regions, though Borlace counters that the system requires refilling only once every four days in the hottest, driest areas. The argument holds weight because it addresses the specific thermodynamic failures of previous attempts, which often struggled with solar absorption.
From Lab Bench to Real World
The transition from theory to practice is where many academic breakthroughs stall, but Borlace presents evidence that this MIT design has already been tested on a rooftop. "Even in sub-optimal weather conditions it could achieve just over 9 degrees Celsius or about 19 degrees Fahrenheit of cooling," he reports. This is a significant delta for a passive system. The potential applications are vast, ranging from keeping food fresh in off-grid areas to improving the efficiency of conventional air conditioners by cooling their condensers. "By design condensers get very hot; if chilled water could be channeled around the condenser then heat could be dissipated much more quickly and the overall efficiency of the AC system would be greatly improved," Borlace argues. This secondary application could be the real game-changer, as it upgrades existing infrastructure rather than requiring a complete replacement of the global cooling fleet.
However, the path to commercialization is not without friction. Borlace is candid about the economic hurdles, specifically the cost of producing the aerogel. "The pores are produced by mixing the polyethylene with solvents... until it reaches something called a critical drying point... that requires specialist equipment which of course costs money." The research team is actively exploring cheaper alternatives like freeze-drying, but the material science remains a bottleneck. This transparency strengthens Borlace's credibility; he isn't selling a fantasy but a promising technology with a clear, albeit difficult, engineering challenge to overcome.
"If they can get that wrinkle ironed out then this one does look like a very promising development especially for food storage and safety in those parts of the world with limited access to the resources we all enjoy in Western societies."
Bottom Line
Borlace effectively reframes the cooling crisis not as an energy generation problem, but as a heat rejection problem, offering a tangible solution that bypasses the grid entirely. The argument's greatest strength is its dual focus on immediate humanitarian needs—food preservation in developing nations—and systemic climate mitigation through improved efficiency of existing infrastructure. Its primary vulnerability remains the manufacturing cost of the specialized aerogel, a hurdle that must be cleared before this technology can scale from a lab experiment to a global standard.