Beyond batteries: new solar device makes fuel straight from sunlight

The latest solar promise: liquid fuel made automatically whenever the sun shines

The great Achilles heel of photovoltaics is that it produces power exactly when it is least needed, at midday, and stops as soon as clouds roll in. Storing that energy in lithium batteries is expensive and has a limited lifespan. That is why every so often an alternative emerges that promises to turn sunlight into something like gasoline, but without emissions. The latest comes from a Japanese laboratory in the form of a filed patent: a device that, according to its developers, produces formic acid directly from the sun and regulates itself without any external electronics.

The trick lies in the built-in chemistry: instead of relying on an external control system to adjust production, the material itself responds to light intensity. When the light is strong, it speeds up; when the sun fades, it slows down. The end product, formic acid, is no ordinary fuel: it can be stored for months in conventional tanks and later release hydrogen or generate electricity through a fuel cell. Something like a liquid battery that never fully discharges.

But some are keeping their feet on the ground. The efficiency? It has not even been published. The scale? At least a decade away. And there are those who suspect that, if it works, someone with interests in oil or batteries will silence it before it ever reaches a garage. For now, the only tangible thing is a patent application in Japan and the promise that the system regulates itself. Not much, but in a world where intermittent energy still lacks a cheap solution, any clue deserves a look.