(Berlin) - Hydrogen from renewable energies is currently even more expensive than gray hydrogen from natural gas. “But the production of green hydrogen with sunlight can be profitable,” says a study by the Helmholtz Center (HZB) and the Technical University of Berlin. Part of the hydrogen is used to process raw chemicals from biomass into high-quality chemicals for industry. This concept of co-production is “very flexible,” according to the researchers. The technology could be used to produce different products depending on demand.
The photoelectrochemical systems (PEC) used for this offer a “promising approach”. The scientists examined how the balance changes when some of the hydrogen is used to produce methylsuccinic acid (MSA) with itaconic acid (IA) within the same PEC plant. The raw material itaconic acid comes from biomass and is supplied. Methyl succinic acid is required by the chemical and pharmaceutical industries.
Target: 1,50 euros per kilogram
“With a realistic efficiency of the PEC system of ten percent and taking into account primary costs as well as operating, maintenance and decommissioning costs, pure PEC hydrogen production remains too expensive compared to production from fossil methane,” say the scientists. This applies even if the service life of the PEC system is set at 40 years.
Illustration of solar powered photoelectrochemical PEC and hydrogenation plant. The technology uses sunlight to produce hydrogen. Some of the hydrogen reacts with biomass raw materials to form valuable chemicals. © Helmholtz Center Berlin for Materials and Energy GmbH / H. Tahini, ScienceBrush Design
However, the balance changes when the PEC system is coupled with the hydrogenation process. “Even if only eleven percent of the hydrogen produced is converted into MSA, the costs fall to 1,50 euros per kilogram of hydrogen and are therefore at the same level as for hydrogen from methane steam reforming.” This already applies from the lifespan of the PEC system of just five years. Experimentally, it was possible to “target between eleven percent and up to 60 percent of the hydrogen for the production of MSA.”
Instead of MSA, other compounds could in principle be produced in the plant as co-products if other starting materials and catalysts were used, for example acetone could be hydrogenated to isopropanol. “We have discovered a promising way to make solar hydrogen production economical,” says Fatwa Abdi, who worked at the HZB until mid-2023 and now works at the City University in Hong Kong.
“Nature communications (2023): Solar-driven upgrading of biomass by coupled hydrogenation using in situ (photo)electrochemically generated H2.
Keisuke Obata, Michael Schwarze, Tabea A. Thiel, Xinyi Zhang, Babu Radhakrishnan, Ibbi Y. Ahmet, Roel van de Krol, Reinhard Schomäcker & Fatwa F. Abdi The study is available free of charge PDF (11 pages).
Photos
Researcher: The production of green hydrogen using direct sunlight alone can be profitable without using solar power from a photovoltaic system. © Enel Green Power
