Energy

Solar dish reactor produces hydrogen and captures waste products

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The parabolic dish that plays a key role in the new solar hydrogen reactor from EPFL
LRESE EPFL
The parabolic dish that plays a key role in the new solar hydrogen reactor from EPFL
LRESE EPFL
The reactor at the heart of the new EPFL solar-to-hydrogen system
LRESE EPFL

Engineers at EPFL have built and tested a solar reactor that can generate hydrogen gas from sunlight and water. The system is not only highly efficient at producing hydrogen, it also captures the “waste” products of oxygen and heat to put them to use too.

Hydrogen is set to be a key player in renewable energy, and one of the most effective ways of producing it is by splitting water into its constituent molecules. When done using solar energy, this process is called artificial photosynthesis, and that’s the process this new reactor is tapping into.

The EPFL reactor looks like a satellite dish, and it works on a similar principle – the large curved surface area collects as much light as possible and concentrates it onto the small device suspended in the middle. In this case, the dish is collecting the heat from the Sun and focusing it by around 800 times onto a photoelectrochemical reactor. Water is pumped into this reactor, where the solar energy is used to split its molecules into hydrogen and oxygen.

The reactor at the heart of the new EPFL solar-to-hydrogen system
LRESE EPFL

The reactor also captures two waste products of the process that are usually just released – oxygen and heat. The oxygen could be handy for hospitals or industrial use, while the heat is passed through a heat exchanger and could be used to heat water or a building’s interior.

The reactor was tested on the EPFL campus over 13 days, in August 2020 and February and March 2021, to get a sense of how it worked in different weather conditions. Its solar-to-hydrogen efficiency was found to be over 20% on average, producing around 500 g (1.1 lb) of hydrogen per day. The team says that with this output, over a year the system could power 1.5 hydrogen fuel cell vehicles driving the average distance, or provide about half of the electricity demands of a four-person household.

“With an output power of over 2 kilowatts, we’ve cracked the 1-kilowatt ceiling for our pilot reactor while maintaining record-high efficiency for this large scale,” said Sophia Haussener, corresponding author of the study. “The hydrogen production rate achieved in this work represents a really encouraging step towards the commercial realization of this technology.”

The next step, the researchers say, is to build a demonstration plant of a few hundred kilowatts at a metal production facility, where the hydrogen will be used for metal annealing, the heat for hot water, and the oxygen collected for nearby hospitals.

The research was published in the journal Nature Energy.

Source: EPFL

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11 comments
martinwinlow
And, where, prey is the 8 litres of (*ultra-pure*) water required to make every 1kg of hydrogen going to come from in a world already desperately short of even potable water let alone ultra-pure? For this and a *raft* of other monumental practical reasons the sentence "Hydrogen is set to be a key player in renewable energy..." is extremely moot.
Expanded Viewpoint
How many years must this thing run to show any kind of a profit? Where does the energy that is needed to compress the Oxygen into cylinders come from? How much energy and money does it take to build one of these things and then maintain it? What is the life span of the reaction chamber, and how much does it cost to replace it, in both materials and labor? It looks like another boondoggle, because that is what it really is.
Karmudjun
Nice article Michal, but this is somewhere between a Satellite dish and a Astronomy Satellite dish! The Source article showed it dwarfing a human being!. Just how big it is I didn't find in a short read - but it is not your "personal hydrogen source", it would be an institutional device. I can see how an industrial scale of these dominating the roof of academia and hospitals might be useful, but you have to have scale to make it worthwhile. Of course, the issue of water when you have a high heat source and plenty of waste water to process - forced evaporation processing could yield distilled water for the hydrogen production - since this is PV and thermal utilization as you scale, these "where is the water coming from" questions only become a footnote, one regarding the reduction in efficiency due to processing available waste water. But great write up otherwise Michael - while on the surface it looked user friendly but it turns out it is industrial friendly only, and so big for so little output of hydrogen!
Douglas Tooley
Although the skepticism of Martin and Expanded is certainly warranted it is by no means proven. This knee jerk reaction to possible futures is unfortunately all too common these days.

That said, cost information of any sort is missing from this article. For proprietary considerations that is understood. One can presume that the oxygen created is a substantial part of the benefit.

That said I do have to wonder if a mid-scale version of this tech is feasible, say as part of a retirement or hospital facility electric micro-grid.

I do share these commenters skepticism about the current powers that be’s ability to do much of anything these days. However not to try is an even more assured failure.

Smaller scale efforts are needed for lots of reasons and the ability to fail is at the foundation of success for both democracy and capitalism. And even more so, science.
Adrian Akau
Good. I am sure that the process can be scaled up.
oldpistachio
A researcher has discovered that EPFL stands for École Polytechnique Fédérale de Lausanne. Lausanne, Switzerland.
It is not East Paducah Fusion Lab as originally suspected.
Graeme S
Well said Douglas Tooley!
meofbillions
The 20% overall efficiency is very good. Compare this to conventional methods, using an alkaline electrolyzer with 0.77 efficiency and PV panels of 0.20 efficiency, for an overall efficiency of 15%.
BlueOak
Cool stuff. Wake me up when I can install one at our rural off-grid property for surviving in the Armageddon times. That will truly be amazing. No need to scrounge for fuel, whether gas or firewood.
Alexander Cokonis
It's worth to expand this technology as much as possible. Converting water directly to oxygen and hydrogen economicly is a huge plus for planet Earth. We spend millions in energy methods which cause harm to the environment on the long run and we pretend they are acceptable because they look good in the front end. We have unlimited land areas which are dessert or semi desert which should be converted to harness the sun's energy. With a front investment we can create unlimited amount of energy the eco friendly way. Oh by the way hydrogen is the most abundant and most versatile fuel in the universe. All fossil fuels which are 90% of our energy and chemical industry are hydrogen with a carbon container.