Converting solar energy into hydrogen could solve storage woes

A device that allows solar energy to be stored as hydrogen could solve one of the major issues with solar panels – providing a consistent flow of electricity even when the sun is not shining.

It is capable of converting solar energy into hydrogen at a rate of 14.2 per cent, and has already been run for more than 100 hours straight under test conditions. The process does not use rare metals unlike typical hydrogen production, of which there is a finite amount on Earth.

The co-creators of the project, French University EPFL and Swiss research body CSEM, claim their method offers high levels of performance and stability that are unique to the device.

The device uses the electrical current produced by a solar panel to 'split' water molecules into hydrogen and oxygen in a process known as water electrolysis.

The clean hydrogen can then be stored away for future use to produce electricity on demand, or even as a fuel.

Even though different hydrogen-production technologies have produced promising lab results in the past, they are too unstable or expensive and need to be further developed to use on a commercial and large scale.

But the approach taken by EPFL and CSEM researchers is to combine components that have already proven effective in industry in order to develop a robust and effective system.

Their prototype is made up of three interconnected, new-generation, crystalline silicon solar cells attached to an electrolysis system that does not rely on rare metals.

"A 12-14 metre square system installed in Switzerland would allow the generation and storage of enough hydrogen to power a fuel cell car over 10,000km every year," said Christophe Ballif, who co-authored the paper on the project.

The process makes the most of existing components, and uses a 'hybrid' type of crystalline-silicon solar-cell-based on heterojunction technology.

The cells are formed in a ‘sandwich structure’, using layers of crystalline silicon and amorphous silicon to allow for higher voltages.

This means that just three of these cells, interconnected, can already generate nearly the ideal voltage for electrolysis to occur.

The electrochemical part of the process requires a catalyst made from nickel, which is widely available.

"With conventional crystalline silicon cells, we would have to link up four cells to get the same voltage," said co-author Miguel Modestino at EPFL. "So that's the strength of this method."

The researchers used standard heterojunction cells to prove the concept; by using the best cells of that type, they would expect to achieve a performance above 16 per cent.

In February, a number of hydrogen vehicle records were broken following the demonstration of a plane that can fly for six hours and a car capable of travelling for 480km on one tank.

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