Opportunities for Renewable Energy

In renewable-based energy systems PEM electrolysis seems to have an advantage over alkaline in that the thin membrane and ion transport mechanism can react to nearly instantaneously with the rapidly changing energy output of renewable sources, especially wind. Stacks involving the circulation of a liquid electrolyte have inherently more inertia in the transport of ions in solution than the PEM systems. 

On the turbine side, variable-speed wind turbines (which will soon be the norm as a result of enhanced energy capture relative to constant-speed machines) rely on power electronics to convert the variable frequency, variable voltage AC produced at the generator to DC. Small turbines used in battery-charging applications stop here  

There are a number of weaknesses with this configuration, namely a redundancy of power electronics leading to increased cost and potential for failure. The inability to match wind turbine power output to electrolyzer power requirements because of separate power electronic controllers ultimately results in reduced energy capture. 

Renewable electrolysis can help overcome one of the key barriers to realizing a hydrogen-based economy by replacing the carbon-intensive one that exists today. There is an excellent opportunity for research in renewable hydrogen production both in terms of understanding the operation of the electrolyzer under variable sources and optimizing, in terms of efficiency, cost, and robustness, the link between a renewable source and electrolyzer stack. 

If the environmental benefits of the long-term development of the hydrogen economy are to be realized, the production of hydrogen via electrolysis from RE sources will be a vital component. Today s commercially available electrolyzers are 

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Hooper R. J., Cox B. Gifford J. Li J. (2000) Opportunities for renewable energy from woody biomass A New Zealand perspective. Proceedings (CD Rom) of Chemeca 2000 Conference. 

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