In the future, green hydrogen could be produced directly on the roof of a house using new photoreactor panels. Based on the model of plant photosynthesis, these solar panels photochemically split water passed through using sunlight and a catalyst. Thanks to the modular design suitable for mass production and inexpensive materials, the system is efficient and versatile, as the team from the Karlsruhe Institute of Technology and its spin-off photreon explains.
Nature shows us how: During photosynthesis, plants produce energy-rich compounds using only CO2, water and light. This is made possible by special enzymes that act as photocatalysts to initiate the necessary reactions. The so-called solar-to-gas processes imitate this principle. As with the natural model, the incident light triggers a chemical reaction that produces hydrogen. Specially developed, light-active materials absorb the energy of solar radiation and are thereby put into an excited state. This releases electrons, which initiate the splitting of water (H₂O) into hydrogen (H₂) and oxygen (O₂).
With sunlight and catalyst
Solar panels developed by researchers at the Karlsruhe Institute of Technology (KIT) work according to this principle. “We skip the detour via electricity-based electrolysis and produce chemical energy from the sun and water,” explains Paul Kant from the Institute for Microprocess Engineering (IMVT) at KIT. Together with colleagues, he initiated the KIT spin-off photreon, which is now responsible for the technical implementation and is intended to bring the system to market maturity.
The core element of the solar hydrogen system are numerous reaction channels running in parallel. “In cross-section, such a channel consists of a V-shaped concentrator that captures light from different directions of incidence and directs it into a tubular, mirrored chamber,” explain the researchers. This creates optimal temperatures and light intensities for the photocatalyst in the reactor chamber. The new photoreactor panel has four times higher photocatalytic efficiency than a simple photoreactor made of glass capillaries, says Kant. Water flows through the reaction chamber, which is then split into hydrogen and oxygen by the catalyst.
Cost-effective materials and modular construction
The modular panels with an integrated hydrogen reactor are intended to simplify solar hydrogen production and make it cheaper. “Photovoltaics and electrolyzer are replaced by the photoreactor panel in one process step,” explains co-founder Maren Cordts from IMVT. “This significantly reduces system costs and complexity when producing green hydrogen.” The design of the modules is also designed so that it can be manufactured using common mass production processes – and from cost-effective materials: The basic structure of the panels consists of the common plastics polycarbonate and polyethylene, the reflector layer made of sprayed aluminum. “The material costs for these components are only around 9.40 US dollars per square meter,” report Kant and his team.
Thanks to the modular approach, the new hydrogen panels can be used for both small, decentralized applications and large systems. For example, medium-sized companies – for example in the specialty chemicals, food industry or metal processing – could use this to cover their hydrogen needs. The modules are also suitable for the industrial production of green hydrogen in sunny regions. “Especially where there are neither electricity networks nor a connection to a hydrogen network, our technology opens up new scope for local generation,” says Cordts.
Source: Karlsruhe Institute of Technology, photreon