Compact energy generator Green hydrogen from small power plant

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Hydrogen generated with solar power can replace fossil fuels. In the Neo-PEC project, researchers have now developed a tandem module that independently and safely produces such green hydrogen.

In order for industrial processes to become more climate-friendly in the future, hydrogen as an energy supplier is a key factor. An energy carrier, which burns without CO₂ release, should ideally be created without CO₂ footprint, as researchers from the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) in Dresden, Germany, point out. A classic method to achieve this is electrolysis. As is well known, water is decomposed into hydrogen and oxygen by electricity. If the electricity needed for electrolysis comes from renewable sources such as photovoltaics, the desired green hydrogen is thus produced. The disadvantage so far, however, is that the electrolyzers needed for this process usually represent rather large and highly complex systems, as the researchers say. The costly and maintenance-intensive devices would also become scarce, especially under the current global and climate policy signs. But a compact alternative is shimmering on the horizon...

Power generation and electrolysis in a single system

An exciting alternative, according to Dresden, is the direct solar water splitting (photoelectrochemical cell—PEC). As part of the already mentioned joint project Neo-PEC, experts from three Fraunhofer Institutes have now developed a modular system which makes a highly flexible hydrogen production and supply by solar energy possible. The core of the Fraunhofer development is a so-called Tandem-PEC module. It is similar to its classic photovoltaic counterpart, but there is a crucial difference: the current is not generated to maintain electrolysis elsewhere later on. The entire process takes place in the same unit. However, caution is necessary! Since hydrogen and oxygen are generated in the process, the setup must be such that the two elements are strictly produced separately and that they remain so, as the participants explain. For the tandem cell, commercially available float or flat glass is coated on both sides with semiconductor materials. When the sun shines on it, one side of the module absorbs the short-wave light of the solar spectrum. At the same time, the long-wave light penetrates the top layer of glass and is absorbed on the opposite side. The module releases hydrogen on the reverse or cathode side, and oxygen on the top or anode side.

Reactor with turbo effect generates a decent amount of hydrogen per year

Over the three-year duration of the project, the Fraunhofer researchers investigated and developed high-purity semiconductor materials, which they can apply to the glass using particularly gentle coating processes. This increases the hydrogen yield in the process. Using the gas phase, the experts create layers on the glass that are only nanometers thin, it continues. The structures that are created have a major impact on the reactor activity. The photovoltaic elements linked in the module supply the system with additional voltage. This acts like a turbo, accelerating activity and thus increasing efficiency. This results in a reactor with an active surface area of half a square meter. Separate from the oxygen, it generates the hydrogen, which can be immediately captured and quantified, it is emphasized. Currently, a single module delivers a performance of over 30 kilos (66 lb) of hydrogen per year over 100 square meters under European solar irradiation. With this yield, for example, a hydrogen car could travel 15,000 kilometers (9,320 miles) to 20,000 kilometers (12,400 miles).