EPFL engineers build solar reactor for efficient hydrogen production

Researchers at École polytechnique fédérale de Lausanne (EPFL) have successfully constructed and tested a highly efficient solar reactor capable of generating hydrogen gas from sunlight and water. This innovative system not only produces hydrogen but also utilizes the byproducts of oxygen and heat that are typically considered waste.

The EPFL reactor operates on the principle of artificial photosynthesis, where water molecules are split into hydrogen and oxygen using solar energy. The sunlight is concentrated approximately 800 times by a large curved dish and directed onto a suspended photoelectrochemical reactor at the center.

In addition to producing hydrogen, the system captures the usually released waste products, oxygen and heat, and repurposes them. The collected oxygen can be utilized in hospitals or industries, while the captured heat can be transferred through a heat exchanger to heat water or a building's interior.

Thorough testing of the reactor took place over 13 days on the EPFL campus during different weather conditions in August 2020, February, and March 2021. The system demonstrated an average solar-to-hydrogen efficiency exceeding 20%, resulting in a daily production of around 500 g (1.1 lb) of hydrogen. This output could power 1.5 hydrogen fuel cell vehicles covering average distances or fulfill approximately half of the electricity requirements for a four-person household throughout a year.

The researchers intend to construct a demonstration plant with a capacity of a few hundred kilowatts at a metal production facility. The hydrogen generated by the plant will be employed for metal annealing, the heat will be utilized for hot water, and the collected oxygen will be supplied to nearby hospitals.

The development of this solar reactor carries substantial potential for the renewable energy industry. By harnessing solar energy to produce hydrogen, it becomes possible to reduce carbon emissions and dependency on fossil fuels. Moreover, the ability to repurpose waste products enhances the system's efficiency, making it more economically viable.

Nevertheless, the implementation of this technology may face certain challenges. The construction and maintenance costs of such reactors could be significant, and the availability of raw materials like water and sunlight might be limited in certain regions. Additionally, the storage and transportation of hydrogen gas can present difficulties due to its low density and high flammability.