Solzinc process

The Solzinc process is a thermochemical process supported by the European Union for the production of hydrogen from water using zinc and solar energy . The aim is to store solar energy in the form of metallic zinc. The process was developed in the laboratory for solar technology at the Swiss Paul Scherrer Institute (PSI) at the ETH Zurich .

Procedural steps

Scheme of the process steps in the Solzinc process

The process essentially consists of two steps. In the first step, zinc oxide is thermally split into zinc and oxygen by solar energy ( e.g. solar tower power plants ):

${\displaystyle \mathrm {2\ ZnO\longrightarrow 2\ Zn+O_{2}} }$

In order to lower the temperature necessary for the production of the metallic zinc, up to 15% of the stoichiometric amount of carbon can optionally be added as a reducing agent according to:

${\displaystyle \mathrm {ZnO+C\longrightarrow Zn+CO} }$

The reaction temperature drops from over 1800 ° C to approx. 1200 ° C.

In the second step, the zinc obtained in this way is converted with water to form zinc oxide and hydrogen:

${\displaystyle \mathrm {Zn+H_{2}O\longrightarrow ZnO+H_{2}} }$

This reaction is exothermic and takes place at around 350 ° C.

The efficiency of the process was 30% in the pilot plant at the Weizmann Institute of Science in 2005 , but an efficiency of 60% is expected through process optimization. The resulting hydrogen is used to generate energy through combustion. Alternatively, the zinc can also be used in zinc-oxygen fuel cells to generate electricity. Concepts for large-scale use have already been developed.

If the addition of carbon is dispensed with ( zinc-zinc oxide process ), the design effort for the reactor increases. However, it is advantageous that the process takes place without the emission of carbon dioxide. The carbon monoxide generated directly when carbon is added would only enable a neutral CO ₂ balance if it is used for chemical syntheses in which it replaces other fossil CO ₂ sources.

literature

• T. Osinga, G. Olalde, A. Steinfeld: Solzinc Reactor Modeling and Experimental Validation . Ed .: ETH Zurich . ( PDF ).

Individual evidence

1. ^ ^{A b} Bernd Schröder: Solar chemistry: solar furnace pours energy into metal . In: Spiegel Online . Retrieved June 22, 2009.
2. ↑ Ulrich Frommherz, Stefan Kräupl, Robert Palumbo, Aldo Steinfeld, Christian Wieckert: Zinc stores solar energy . In: spectrum . No. 2 , 2003, p. 4–11 ( PDF ).
3. ↑ Bernd Schröder: Solar thermochemistry . In: telepolis . December 25, 2005. Retrieved January 7, 2010.
4. ^ Michael Epstein, Gabriel Olalde, Sven Santén, Aldo Steinfeld, Christian Wieckert: Towards the Industrial Solar Carbothermal Production of Zinc . In: Journal of Solar Energy Engineering . tape 130 , no. 1 , 2008, p. 014505-014505-4 , doi : 10.1115 / 1.2807214 .