A hydrogen solar system that cogenerates heat and oxygen

17 Apr. (EUROPE PRESS) –

Researchers in Switzerland have built a pilot-scale solar reactor that produces usable heat and oxygen, in addition to generating hydrogen with unprecedented efficiency for its size.

A satellite dish on the EPFL campus (Federal Polytechnic School of Lausanne) easily overlooked, it resembles a satellite dish or other telecommunications infrastructure. But this plate is special, because it works like an artificial tree. After concentrating solar radiation nearly 1,000 times, a reactor on the dish uses that sunlight to convert water into valuable, renewable hydrogen, oxygen and heat.

“This is the first demonstration at the solar hydrogen generation system level. Unlike typical lab-scale demos, it includes all ancillary devices and components, so it gives us a better idea of ​​the energy efficiency you can expect once you consider the entire system, and not just the device itself.” , says it’s a statement Sophia Haussener, director of the Renewable Energy Science and Engineering Laboratory (LRESE) of the Faculty of Engineering.

“With a power output of more than 2 kilowatts, we have broken the 1 kilowatt ceiling for our pilot reactor while maintaining record efficiency for this large scale. The hydrogen production rate achieved in this work represents a truly encouraging step towards the commercial realization of this technology”.

The work builds on preliminary research demonstrating the concept at laboratory scale, using LRESE’s High Flux Solar Simulator, which was published in Nature Energy in 2019. Now, the team has published the results of its scalable, efficient and multi-process product under real world conditions in the same magazine.

The production of hydrogen from water using solar energy is known as artificial photosynthesis, but the LRESE system is unique in its ability to produce heat and oxygen at scale.

After the dish focuses the sun’s rays, water is pumped to its focus point, where an integrated photoelectrochemical reactor is housed. Inside this reactor, photoelectrochemical cells use solar energy to electrolyze, or split, water molecules into hydrogen and oxygen. Heat is also generated, but instead of being released as a loss from the system, this heat passes through a heat exchanger so that it can be used, for example for space heating.

In addition to the primary outputs of hydrogen and heat from the system, the oxygen molecules released by the photoelectrolysis reaction 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,” says Haussener.

The system is suitable for industrial, commercial and residential applications; in fact, SoHHytec SA, spin-off of LRESE, is already implementing and commercializing it. The EPFL startup is working with a Swiss-based metal production facility to build a multi-100 kilowatt scale demonstration plant which will produce 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 an important milestone by demonstrating unprecedented efficiency at high output power densities. We are now scaling up a system in an artificial garden-like configuration, where each of these ‘artificial trees’ is implemented in a modular fashionsays 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. With a production level of approximately half a kilogram of solar hydrogen per day, the EPFL campus system could power around 1.5 hydrogen fuel cell powered vehicles that travel an average annual distance; or meet up to half of the demand for electricity and more than half the annual heat demand of a typical four-person Swiss household.

With his artificial photosynthesis system well on its way to scaling, Haussener is already exploring new avenues of technology. In particular, the lab is working on a large-scale solar power system that would split carbon dioxide instead of water, producing useful materials like syngas for liquid fuel or ethylene, precursor of green plastic.