Energy: Producing hydrogen and oxygen from water using sunlight

Hydrogen and oxygen production through thermal water splitting using solar energy. This is the subject of a new patent devised  by the ENEA laboratories  of  the "Fusion and Technologies for Nuclear Safety" and "Energy Technologies and Renewable Sources" Departments at the Frascati and Casaccia Research Centers

“Thermochemical water splitting uses high temperatures to decompose water molecules into hydrogen and oxygen, subsequently separated. Since it demands very high operating temperature, traditional processes cannot support this requirement” the ENEA researcher Silvano Tosti explained.

In order to reduce these extremely high temperatures, the patent proposes an innovative membrane reactor comprising a reaction chamber containing two types of membranes: one in tantalum to separate hydrogen and one in a ceramic material to separate oxygen.

“This allows to produce the same amount of hydrogen and oxygen at 500 ° C less than a conventional reactor”, Tosti said.

The other innovation is combining this membrane reactor with concentrating solar systems, capable of supplying heat at high temperatures, thus making it possible to produce hydrogen directly from sunlight.

"The direct production of hydrogen using solar energy, in comparison with other systems such as solar photovoltaics coupled with alkaline electrolysers, is of great interest for the creation of a green energy chain, since it is characterized by high energy efficiencies and low investments costs both in stationary applications, such as civil and industrial electrical users, and in mobile ones, like electric vehicles ”, Tosti concluded.

Another sector significantly impacted is the high purity gases industry.  In this case, hydrogen and oxygen can be used in fine chemicals, pharmaceuticals, and electronics industry. Further development of this type of reactor will benefit from technological advances in high temperature solar systems and materials for high heat flows.

For more information please contact:

Silvano Tosti,  ENEA - Head Nuclear Technologies Laboratories, silvano.tosti@enea.it

Project team: Alfonso Pozio; Luca Farina; Alessia Santucci