For chemical reactions, the zinc–zinc oxide cycle or Zn–ZnO cycle is a two step thermochemical cycle based on zinc and zinc oxide for hydrogen production with a typical efficiency around 40%.
Process description
The thermochemical two-step water splitting process uses redox systems:4
- Dissociation: ZnO → Zn + 1/2 O2
- Hydrolysis: Zn + H2O → ZnO + H2
For the first endothermic step concentrating solar power is used in which zinc oxide is thermally dissociated at 1,900 °C (3,450 °F) into zinc and oxygen. In the second non-solar exothermic step zinc reacts at 427 °C (801 °F) with water and produces hydrogen and zinc oxide. The temperature level is realized by using a solar power tower and a set of heliostats to collect the solar thermal energy.
See also
- Cerium(IV) oxide–cerium(III) oxide cycle
- Copper–chlorine cycle
- Hydrosol-2
- Hybrid sulfur cycle
- Iron oxide cycle
- Sulfur–iodine cycle
External links
References
Solar Hydrogen Production from a ZnO/Zn Thermo-chemical Cycle Archived July 24, 2008, at the Wayback Machine http://www.solarpaces.org/Tasks/Task2/SHP.HTM ↩
Project PD10 http://www.hydrogen.energy.gov/pdfs/review06/pd_10_weimer.pdf ↩
Novel Method for solar hydrogen generation Archived February 5, 2009, at the Wayback Machine http://www.switt.ch/files/technologien/Solar%20Hydrogen%20Production_04-014.pdf ↩
Solar thermal ZnO-decomposition https://web.archive.org/web/20060505180329/http://solar.web.psi.ch:80/data/research/zno/roca/ ↩