Scientists Built Solar Panels That Generate Electricity Even on Cloudy Nights

Solar panels work by absorbing sunlight. Logically, they shouldn't work at night. But in 2022, engineers at Stanford demonstrated a modified solar panel that produces electricity in the dark — by reversing the basic principle of how it works.

The trick is radiative cooling. On clear nights, surfaces facing the sky cool down faster than the surrounding air because they radiate infrared heat into space. The Stanford team coupled this temperature difference to a thermoelectric generator, producing about 50 milliwatts per square meter at night.

That's Not Much. So Why Does It Matter?

• It is enough to power small sensors, LEDs, or charge a phone over a long night
• It is "free" power — using only the temperature difference between Earth and space
• It works in places far from the grid, where every milliwatt counts
• It opens an entirely new source: night-sky cooling as energy

The Bigger Picture

Earth receives about 174,000 terawatts of solar power and radiates about the same back into space at night. Solar panels capture a fraction of the incoming. Radiative-cooling panels capture a fraction of the outgoing. Together, they could harvest energy 24 hours a day from previously untapped flows.