Researchers at École polytechnique fédérale de Lausanne (EPFL) and the Swiss Center for Electronics and Microtechnology (CSEM) have designed a new device using commercially available solar cells, and none of the usual rare metals, that stores solar energy as hydrogen more stably, efficiently and at lower cost than all previous methods.
Solar energy is stored for periods without sun by converting the energy into hydrogen via electrolysis, using the electrical current produced by the solar panel to split water molecules into their hydrogen and oxygen components.
The hydrogen can then be stored for future use as fuel or to produce electricity. The issue encountered so far is that although there are hydrogen-production technologies with potential, they have been too unstable or expensive to be used on a commercial scale.
The method used by the EPFL and CSEM team involved a combination of components that have already been proven to be effective in the industry.
The researchers’ prototype consists of three interconnected, new-generation, crystalline silicon solar cells attached to an electrolysis system that does not rely on rare metals.
The device can convert solar energy into hydrogen at a rate of 14.2% and has so far been run for more than 100 straight hours in test conditions. This represents a world record for silicon solar cells, as well as for the production of hydrogen without the use of rare metals.
The team’s effort outdoes all prior attempts in regards to stability, performance, lifespan and cost efficiency.
“A 12-14m² 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 EPFL researcher Christophe Ballif, who co-authored the paper and who also heads the CSEM PV-center.
The key to the team’s success is two-fold, resting on both the efficient use of existing components and the employment of a ‘hybrid’ crystalline-silicon solar cell based on heterojunction technology.
The device is structured using layers of crystalline silicon and amorphous silicon that allow for higher voltages, meaning that with only three of these interconnected cells, it is possible to generate a near perfect voltage for electrolysis.
Additionally keeping the cost down is the usage of a nickel catalyst for the electrochemical part of the process. The concept was proven using standard heterojunction cells, but it is expected that by using the best available cells, they could achieve performance rates as high as 16%.
“We wanted to develop a high performance system that can work under current conditions,” said Jan-Willem Schüttauf, a researcher at CSEM and co-author of the paper.
“The heterojunction cells that we use belong to the family of crystalline silicon cells, which alone account for about 90% of the solar panel market. It is a well-known and robust technology whose lifespan exceeds 25 years. And it also happens to cover the south side of the CSEM building in Neuchâtel.”