Third-generation, small-scale electricity storage system

Metal-air redox flow battery

Electricity storage systems could well be central to the future of our electricity supply. Looking ahead, we may expect decentralized power generation to play a bigger role and the volume of sustainable wind and solar energy to increase. The output from such power sources is hard to control or to match with the demand, and this has implications for the stability and quality of electricity networks.

Several technologies for local, small-scale storage are currently available or under development. For systems of more than 100 MW(h), however, the only feasible options are pumped storage and compressed air energy storage (CEAS). Systems based on these technologies have a major geographical impact. For small-scale electricity storage, the redox flow battery is an attractive alternative.

Redox flow storage units of the present generation need a reactor with an expensive membrane and two large vessels with electrolytes in an acid environment. With all the controls and auxiliary equipment, the capital cost of such a system works out at about € 100 per kWh.

Objectives
The objectives of this project are to find a way of using atmospheric oxygen as the cathodeside electrolyte and to develop membranes that are easy and cost-effective to produce on a large scale. If these objectives are realized, the resulting third-generation redox flow systems should provide power at about € 50 per kWh – half the cost of the current systems.

The project phases are
> Market survey
> Membrane development
> Development of the electrode and catalyst
> Development of a membrane-electrode assembly
> Integration of the separately developed components into one operational system
> Management, communication and dissemination

Benefits
The use of electricity storage systems will enable more small-scale, sustainable generating units to be integrated into the distribution network without compromising the quality of electricity supply. Metal-air technology will decrease the volume and weight of redox flow batteries and reduce their cost.

Project coordinator
>KEMA, the Netherlands

Project partners
> University of Twente, European Membrane Institute (EMI), the Netherlands
> MAGNETO Special Anodes, the Netherlands

Project details
> EOS-LT NEO Program
> Duration: November 2006 – April 2011