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Described as working like an artificial tree, the reactor was developed and installed at the Swiss Federal Institute of Technology Lausanne (EPFL).
The parabolic dish concentrates solar radiation nearly 1,000-times, which is focused on the integrated photoelectrochemical reactor above the dish. The reactor uses the sunlight to convert water into renewable hydrogen and oxygen, while also providing heat.
“This is the first system-level demonstration of solar hydrogen generation. Unlike typical lab-scale demonstrations, it includes all auxiliary devices and components, so it gives us a better idea of the energy efficiency you can expect once you consider the complete system, and not just the device itself,” said Sophia Haussener, head of EPFL’s Laboratory of Renewable Energy Science and Engineering (LRESE).
“With an output power of over 2kW, we’ve cracked the 1kW ceiling for our pilot reactor while maintaining record high efficiency for this large scale. The hydrogen production rate achieved in this work represents a really encouraging step towards the commercial realisation of this technology.”
After the dish concentrates the Sun’s rays, water is pumped into the focus spot. Within the reactor, photoelectrochemical cells use solar energy to electrolyse the water molecules, splitting them into hydrogen and oxygen. Generated heat is passed through a heat exchanger so it can be harnessed, potentially for central heating. The oxygen molecules are also recovered and used.
“Oxygen is often perceived as a waste product, but in this case, it can also be harnessed – for example for medical applications,” said Haussener.
The system is suitable for industrial, commercial, and residential applications, the researchers said. LRESE spin off SoHHytec SA is already deploying and commercialising the technology, working with a Swiss metal production facility to build a demonstration plant that will work in the hundreds of kilowatts scale, producing hydrogen for metal annealing processes, oxygen for nearby hospitals, and heat for the factory’s hot water needs.
“With the pilot demonstration at EPFL, we have achieved a major milestone by demonstrating unprecedented efficiency at high output power densities. We are now scaling up a system in an ‘artificial garden-like’ set up, where each of these ‘artificial trees’ is deployed in a modular fashion,” said SoHHytec co-founder and CEO Saurabh Tembhurne.
The system could be used to provide residential and commercial central heating and hot water, and to power hydrogen fuel cells. At an output level of about half a kilogram of hydrogen per day, the team said the EPFL campus system could power around one-and-a-half fuel cell vehicles driving an average annual distance, or meet up to half the electricity demand and more than half of the annual heat demand of a typical four-person Swiss household.
The lab is also working on a large-scale solar-powered system that would split carbon dioxide instead of water, yielding useful materials such as syngas for liquid fuel, or the ‘green’ plastic precursor ethylene.
The work built on preliminary research demonstrating the concept at lab-scale, using LRESE’s high-flux solar simulator, which was published in Nature Energy in 2019. The new work was also included in the same publication.
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