Somewhere on a Stanford rooftop, water got colder than the air around it, and nothing was plugged in to make that happen. No compressor hum, no electricity-meter spike, nothing. It was just pipes, sunlight, and a very clever mirror. In 2017, Stanford researchers Eli Goldstein, Aaswath Raman and Shanhui Fan published a study titled ‘Sub-ambient non-evaporative fluid cooling with the sky’ in Nature Energy describing rooftop panels that cool flowing water without using electricity. The panels were tested on the roof of Stanford’s Packard Electrical Engineering Building, and they lowered the water temperature 3 to 5 degrees Celsius below the outside air temperature, with no compressor, no refrigerant and no power cord. They just sent the water's excess heat outward into space.
How do you send heat into space?
