According to IEEE Spectrum: Technology, Engineering, and Science News, researchers at the University of California, Davis have created a radiative cooling device that works like a reverse solar panel, generating power at night. Led by Professor Jeremy Munday, the team used a mechanically simple Stirling engine, which doesn’t require exotic materials, paired with a heat-radiating panel. In nighttime experiments over a year, the device achieved more than 10 degrees C of cooling most months, converting that into over 400 milliwatts of mechanical power per square meter. They used it to directly power a fan and, with a small motor, generate electricity. The power output is about two orders of magnitude lower than solar panels, but the goal is to provide useful work when solar isn’t available—like at night—without needing batteries, wiring, or fuel. The researchers calculated it could generate over 5 cubic feet per minute of airflow, meeting minimum ventilation standards for public buildings.
How this night power actually works
Here’s the thing: the core concept isn’t brand new. Scientists have known about radiative cooling materials since at least 2014—those super-thin surfaces that beam heat into space as specific infrared wavelengths, literally cooling things down without electricity. The big leap here is pairing that physics with a very old-school piece of machinery: the Stirling engine. Basically, you’ve got a sealed chamber of gas. The radiative panel cools one side of it, the ambient Earth heats the other, and that small temperature difference makes the gas expand and contract. That drives a piston. No combustion, no rare semiconductors. It’s elegantly simple. And that’s the point. Munday’s team flipped the script. Instead of an engine rejecting waste heat into the air, this one uses the cold of outer space as its heat sink. It’s a clever, almost philosophical, inversion of how we usually think about energy.
Why this isn’t about replacing solar
Let’s be clear: you’re not going to power your house with this. 400 milliwatts per square meter is tiny. As Munday says, it’s roughly 100 times less power than a solar panel of the same size. So what’s the use case? Look, it’s for niche, off-grid applications where a little bit of mechanical power solves a big problem. Think ventilating a greenhouse at night to manage CO2 and humidity, or providing a trickle of air circulation in a remote shelter. The beauty is it’s completely passive and works precisely when solar panels tap out. It removes the need for a battery bank or a fuel generator for those basic mechanical tasks. For industries that rely on consistent environmental control, like agriculture, a passive, maintenance-light system like this could be a game-changer for operational resilience. When you’re deploying tech in the field, reliability and simplicity often trump raw power output.
The future is in the details
The researchers see a clear path to making this better. Swapping the air inside the Stirling engine for hydrogen or helium could reduce internal friction and boost efficiency. The big goal is to get it working during the day, which is a serious engineering challenge—you’d have to perfectly shield it from direct solar heating while still letting it radiate to space. But if they crack that, you get a truly 24/7 passive power source. Munday’s lab, which you can check out at mundaylab.ucdavis.edu, wants to move from prototype to real-world testing, starting with a greenhouse pilot. The full study is available in the journal *Energy* at ScienceDirect. It’s a reminder that sometimes the most impactful innovations aren’t about chasing the highest efficiency, but about finding the simplest, most robust solution to a specific problem. And in a world obsessed with complex tech, there’s something deeply satisfying about a 200-year-old engine idea finding a new purpose under the night sky.
