Record-breaking device promises low cost, efficient solar energy storage

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.

Image courtesy of Infini Lab / EPFL 2016

Image courtesy of Infini Lab / EPFL 2016

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.

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Traditional solar panels, which have seen growing worldwide use over the last decade

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.”

Mass adoption of electric vehicles would put a dent in climate change: study

A research team at the Massachusetts Institute of Technology has just completed the most comprehensive study yet into the impact that existing electric vehicles can have on climate change, concluding that the vehicles can bring about a meaningful reduction in greenhouse-gas emissions, in spite of their limited driving range.

The study found that it would be possible to enact a wide-scale replacement of conventional vehicles with electric ones today and that such a replacement would play a significant role in achieving climate change mitigation goals. Accounting for the emissions from electricity-providing power plants, the replacement would reduce transportation emissions by roughly 30%.

“Roughly 90 percent of the personal vehicles on the road daily could be replaced by a low-cost electric vehicle available on the market today, even if the cars can only charge overnight,” Trancik said, “which would more than meet near-term US climate targets for personal vehicle travel.”

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The study has been a four-year project, involving the integration of two massive datasets: one highly detailed set of second-by-second driving behaviour based on GPS data, and another broader, more comprehensive set of national data based on travel surveys. Combined, these two datasets include trips in the millions, made by drivers from across the US.

In the process of integrating the datasets, the MIT team was able show that around 90% of personal cars on the road in the US could have their day-to-day energy requirements met by today’s electric vehicles, at a cost no greater than that of a conventional vehicle. The cost analysis included both purchase and operating costs, and took into account the current range of electric vehicles.

The team further looked into the replacement potential by studying once-daily charging, both at homes and workplaces, and the existing charging infrastructure.

They found that a large-scale replacement would be capable of meeting America’s near-term emissions-reduction targets for personal vehicles’ share of the transportation sector, which overall is responsible for roughly a third of the country’s greenhouse emissions, the majority of which is from private vehicles.

The Tesla Model S, one of the more expensive electric vehicles on the market.. Image courtesy of Tesla Motors.

The Tesla Model S, one of the more expensive electric vehicles on the market.. Image courtesy of Tesla Motors.

The point of contention however, comes about from those that argue current electric vehicles are too expensive and lack the range to efficiently replace conventional vehicles.

And while the team found that the vast majority of cars on the road consume no more energy in a day than the battery energy capacity in affordable EVs available today, the study also cautions that for electric vehicle ownership to rise to the hoped for levels, the vehicles must be able to meet driver needs all day, every day.

“This is an issue where common sense can lead to strongly opposing views,” Trancik said.

“Many seem to feel strongly that the potential is small, and the rest are convinced that is it large. Developing the concepts and mathematical models required for a testable, quantitative analysis is helpful in these situations, where so much is at stake.”