Scientists at KU Leuven in Belgium have developed a device that combines incoming solar energy and water vapor from the surrounding air to produce a record-breaking daily average of 250 liters (66 gal) of hydrogen throughout the year. According to the researchers' estimations, an array of 20 such panels paired with an underground pressurized tank could provide the totality of a household's entire electricity and heating needs for a modest price.

Going solar comes with a couple of significant drawbacks, particularly when it comes to managing your reserves. First, storing an energy buffer for a rainy day is all but cheap: a home battery pack will run you up thousands of dollars, and its charge will keep you off the grid for a few extra days at most. Secondly, lithium-ion batteries lose capacity with use, and slowly self-discharge with disuse.

Professor Johan Martens and his team have turned to hydrogen for a cheaper, year-round green energy alternative. Their device has been under development for a decade, and can currently reach a energy conversion of 15 percent.

Commercial solar panels can easily surpass that figure, often reaching 18 or 20 percent, but the advantage of this approach is that large amounts of hydrogen can be stored in an underground pressurized tank (at a pressure of approximately 400 bar) without the inevitable losses in capacity that come with battery technology. Using fuel cells, the reserves from the tank can then be converted at will into heating, electricity, or fuel for a hydrogen-powered car with a 90 percent conversion efficiency.

Hydrogen is often produced from non-green sources such as gas and oil, and it's also expensive to produce and store. This project aims to buck the trend thanks to a combination of high conversion efficiency and the use of small-scale systems designed to work at the local scale.

"We wanted to design something sustainable that is affordable and can be used practically anywhere," says Martens. "We're using cheap raw materials and don't need precious metals or other expensive components."

The researchers estimate that an array of 20 panels and four cubic meters of pressurized storage would meet the energy and heating needs (in Belgium) of a household throughout the year, with the assumption that the reserves will build up during the summer months and last through the winter.

A prototype of this setup will soon begin field testing on a property in the rural Belgian town of Oud-Heverlee. Over the next two years, the researchers are will be focusing on testing the panels for household, agriculture and retail applications, with the eventual goal to mass produce and commercialize the system.

Source: KU Leuven