A 200-year-old secret could revolutionize solar energy: technology promises electricity day and night.

Published 07/01/2026 às 23:14

Updated 07/01/2026 às 23:15

Research conducted by UCLA scientists revives a physical principle described in 1821 to demonstrate the generation of electricity from nighttime radiative cooling, expanding the possibilities of solar energy beyond exclusive reliance on direct sunlight.

The year 2025 saw a significant increase in global installed renewable capacity, particularly in solar energy, driven by innovative projects such as “dark photovoltaics” developed by UCLA, which revives a scientific concept from 1821 and demonstrates low-cost nighttime electricity generation.

Growth in renewable energy capacity and the leading role of solar energy.

In 2025, global installed renewable capacity advanced significantly compared to 2024, with solar energy reaching new heights. This growth was associated with innovative solar projects that expand generation possibilities beyond the traditional limits of photovoltaic technology.

Among these projects, the creation of so-called “dark photovoltaics” by researchers at the University of California, Los Angeles, stands out. The proposal explores a rare natural phenomenon and points to ways to increase electricity generation during periods without direct sunlight.

This initiative arises in a context of accelerated expansion of solar energy, in which solutions capable of operating at night or in adverse conditions gain technical and strategic relevance for the global energy sector.

Historical origin of the concept and revival of an idea from 1821.

The conceptual basis of dark photovoltaics dates back to 1821, when Thomas Seebeck developed a pioneering device known as a thermocouple. timeAlthough the equipment was a major technological obstacle, it established the principle now known as the Seebeck Effect.

The Seebeck effect occurs when two different types of metal wires are joined at their ends and subjected to different temperatures. This thermal difference generates an electrical voltage, which can be converted into a temperature reading using calibration data.

Researchers at UCLA and Stanford University drew inspiration from this principle to create a new type of electricity generation, adapting the historical concept to a natural phenomenon observed in open environments at night.

Scientific development and team responsible for the study.

The project was led by Aaswath Raman, assistant professor of materials science and engineering at UCLA. The study was published in 2019 in the scientific journal Joule, bringing together researchers from two academic institutions.

In addition to Raman, the work involved Wei Li, a postdoctoral student at Stanford University, and Shanhui Fan, a professor of electrical engineering. The team combined knowledge of materials, electrical engineering, and thermal physics.

The researchers sought to demonstrate, on an experimental scale, that converting heat radiated into the night sky could result in measurable electricity generation, even in the absence of direct sunlight.

Device operation and prototype results

The device developed by the team consists of an aluminum disc painted black on one side, positioned with the dark side facing the sky. This disc radiates heat from the surrounding air through a phenomenon known as radiative sky cooling.

The resulting temperature difference is then captured by a thermoelectric generator, which converts the thermal gradient into electricity. According to the results obtained, the prototype was able to produce up to 25 milliwatts per square meter.

This amount of energy is sufficient to power an LED light bulb, demonstrating the technical feasibility of the concept. The prototype cost less than US$30, making the experiment economically accessible for initial testing.

Potential applications and prospects for improvement.

According to Raman, the device can be used to produce electricity both during the day and at night, especially when integrated with existing solar installations. This feature expands the continuous use of photovoltaic infrastructure.

The International Energy Agency estimates that more than 1 billion people worldwide lack reliable access to electricity. In this context, technology can represent a springboard for populations living or working in extremely remote areas.

Raman also stated that the technology’s production could be improved up to 20 times compared to the current prototype if advanced components are used. Efficiency tends to be higher in dry, hot climates with high levels of radiative cooling from the sky.

Implications for clean energy and future steps

The research demonstrates that clean energy production can become commercially viable even during darkness. This result broadens the scope of renewable technologies available to diversify the global energy mix.

As the team progresses to new phases of research and development, the focus remains on technical validation and optimizing the device’s performance. These steps are considered essential before any larger-scale application.

Other advances mentioned in the field of solar energy include innovative panels, such as the Apollo Panda, which wrap around various objects. These examples illustrate how ongoing research continues to push the boundaries of photovoltaic generation, even though some challenges still persist.