New “Dark Photovoltaics” Could Make Clean Power Even at Night

Scientists at UCLA (University of California, Los Angeles) have developed a new way to make electricity even when the sun isn’t shining. This technology, called dark photovoltaics, uses a natural cooling effect in the sky to produce power — a big step forward in renewable energy research.

How It Works Without Sunlight

Traditional solar panels make electricity from sunlight hitting them. But this new device works even at night using a different principle called radiative sky cooling:

• At night, the ground and objects on Earth radiate heat up into the cold sky.
• Because the sky is very cold, objects can become cooler than the air around them.
• UCLA researchers used this temperature difference to generate electricity.

They painted an aluminum disk black and pointed it toward the sky. The disk lost heat to the air and became cooler, while a thermoelectric generator turned the temperature difference into a small electrical current. 

First Results: Electricity in Darkness

The prototype device — made from simple parts that cost about $30 — produced up to 25 milliwatts per square meter. That’s enough to power a small LED light bulb.

Right now this output is far lower than normal solar panels produce, but researchers say it shows electricity generation is possible at night and could improve with better materials and design.

Why This Is Exciting

This “dark solar cell” idea could help solve big renewable energy challenges:

• Nighttime power: Solar panels usually stop making power after sunset, requiring batteries or other sources. Dark photovoltaics could help fill that gap.
• Remote energy: Places without reliable electricity, especially in developing countries, might use this kind of technology to produce power without fuel or batteries.
• Blending with solar: Future clean energy systems might combine normal solar cells with dark photovoltaics to produce power day and night.

Experts also think the technology could generate more power in dry, hot climates where the cooling effect is stronger.

How Is This Different From Normal Solar Panels?

This new technology does not replace ordinary solar panels yet, but it opens a new way to produce clean electricity around the clock.

Where the Idea Came From

The work is inspired by an old effect known from the 1820s, when scientists first noticed that objects at different temperatures can produce voltage. UCLA researchers used this idea and combined it with modern materials science to make electricity from cooling temperatures. 

The original concept includes a simple black disk that radiates heat into the sky and a thermoelectric device — a small generator that turns temperature differences into electric current.

Why It Matters for Clean Energy Goals

One big challenge with renewable energy is that sunlight isn’t always available — at night, on cloudy days, or during winter. Finding ways to get power outside of sunshine hours without fossil fuels is key for reaching net-zero emissions and reliable clean power systems. 

Dark photovoltaics may one day help fill that need alongside solar, wind, hydro, and storage technologies, making clean electricity more steady and widespread.

Bottom Line

UCLA’s “dark photovoltaics” are not just a new lab toy — they are proof that solar-like electricity can be generated without sunlight, using the natural cooling of the sky. While the power output is small now, scientists think future versions could be stronger and used with traditional solar power to help provide clean energy day and night. 

This development shows how renewable energy research continues to push boundaries and find innovative ways to power the world sustainably.