A process that yields hydrogen by using solar energy to split water has received one-third of the €1 million Descartes prize, awarded annually for research financed by the European Commission (Brussels, Belgium). The process was developed under the Hydrosol project, headed by the Chemical Process Engineering Research Institute, Center for Research and Technology-Hellas (Thessaloniki, Greece; edlinks.chemengonline.com/6894-541). The team includes researchers from Denmark, Germany and the U.K.
The key development is a cylindrical reactor whose interior is a monolithic refractory ceramic honeycomb of multiple, millimeter-sized parallel channels, coated with an iron oxide-based redox material that absorbs oxygen. A solar concentrator heats the monolith via a quartz window and heats steam to about 800°C as it enters the reactor. Upon contacting the active coating, the vapor is split into O2 (which is absorbed by the coating) and H2, which passes on and is recovered. When the coating is saturated, the O2 is desorbed by solar energy at 1,000-1,200°C. Two reactors are used in parallel, so that one is producing H2 while the other is desorbing, says Christos Agrafiotis, a principal researcher.
The appeal of the process is that it is environmentally friendly and uses abundant and renewable energy and materials sources, he says. So far, it has been tested at a scale of 3 kWe. The next step will be a pilot test at about 100 kWe.