In the HYDROSOL_Plant project, scientists and industrial companies have further developed the process of direct hydrogen production by solar radiation. With improved materials and a new structure of the reactor, it was possible to build a plant with an output of 750 kilowatts. It is thus much more powerful than the previous development stage, which had an output of 100 kW. In the coming months, scientists at Plataforma Solar in Almería (PSA) in southern Spain will be producing hydrogen in a test and demonstration plant to investigate the suitability of the materials.
Hydrogen has the potential to increase the share of renewable energies, especially in the transport and heating sectors. In vehicles with fuel cell drive, for example it can be used as a fuel. It is also a component in the production of synthetic fuels such as methane, methanol, petrol and kerosene. Hydrogen generated from renewable energies can thus significantly reduce carbon dioxide emissions in the transport and heating sectors. Karsten Lemmer, Member of the Executive Board for Energy and Transport at the German Aerospace Research Institute DLR which participates in the project, stresses: “Hydrogen engines can make a significant contribution to climate protection, especially in the transport sector. The research project HYDROSOL_Plant is an essential step on the way to efficient hydrogen production using solar energy.”
Coordinated by the Greek Aerosol and Particle Technology Laboratory (CERTH-CPERI-APTL), DLR, the Spanish research institute Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), the Dutch company HyGear and the Greek energy supplier Hellenic Petroleum are cooperating in the international project. The DLR Institute for Solar Research is responsible for the development of the solar reactor, plant layout and measurement and control technology. The project was funded by the European Fuel Cells and Hydrogen Joint Undertaking (FCH 2 JU).
Hydrogen is produced by the thermal energy of the sun through a thermochemical redox reaction. A large number of mirrors concentrate the sunlight onto a focal point where very high temperatures occur. With the heat generated in this way, water can be split into oxygen and hydrogen. In the first part of the process, the sun heats up redox materials such as nickel ferrite or cerium oxide to 1400 degrees Celsius inside a reactor. At these temperatures, the material is chemically reduced, i. e. oxygen molecules are released and transported out of the reactor. In the second step, which takes place at 800 to 1000 degrees Celsius, the actual water splitting takes place. The researchers let water vapour flow through the reactor, the reduced material absorbs the oxygen from the water – it is chemically oxidized. The oxygen remains in the reactor while the energy carrier hydrogen flows out. Once the material is completely oxidized, it is regenerated by the first process step and the cycle starts again.
Building on previous research projects, the researchers have further developed both the structure of the reaction reactor and the materials. By a second bundling of the solar radiation with an internal mirrored funnel, less heat is lost, which increases the efficiency of the process. Newly developed ceramic foams promise higher hydrogen yield and longer durability.
The scientists expect that they will be able to produce about three kilograms of hydrogen per week in test operation. For example, this could enable an efficient fuel cell vehicle to travel over 100 kilometers.”
Hydrogen is one of the most important basic chemicals. In Japan, more than 200,000 fuel cell systems are already in use in buildings. Hydrogen is also to be used there in large gas-fired power plants to produce electricity and thus replace fossil and nuclear power plants. In addition, the use of hydrogen in industrial processes such as steel production can contribute to significant carbon dioxide savings.
However, researchers do not expect the process to be ready for the market and commercial application until a few years from now: the first applications can be stand-alone solutions if, for example, there is no connection to the electricity grid. In this case, the production process could possibly pay off from a hydrogen production of as little as ten kilograms per week.