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Storage capacity capable of delivering 40% of rated output of a wind farm for two hours would overcome uncertainties in wind prediction and so enable the owner to bid into a market with confidence. If constant output was required, however, then the capacity of the store would need to be about 60% of the rated output of the wind farm. This was the message delivered by Simon Watson of Unit(e), a renewable energy supply company, at the Commercially Viable Electricity Storage conference in London, January 30-31.

A main theme was how storage would fare on open markets under new electricity trading arrangements. It was agreed that "dedicated storage" will rarely be the most cost-effective option for renewables, except in small or isolated networks (“uåX˜äŠÊ˜·³Ç, October 2000). Several speakers noted that contract-based trading systems invariably pay a premium for firm or constant power, so it may well make sense for renewable generators to include storage in their portfolios. This would give them the option to "level" wind output when necessary. For the rest of the time the storage device would earn its keep by trading in the market.

It is too early to say whether the UK's New Electricity Trading Arrangements (NETA) will enhance the prospects for storage. Although they seem likely to penalise intermittent sources such as wind -- quite unfairly from a technical standpoint -- they will, ironically, ease its assimilation because the overall level of spinning reserve on the system will need to be increased.

Any expansion of storage capacity in electricity markets is likely, directly or indirectly, to improve the prospects for large-scale introduction of wind energy. There are few technologies available at competitive prices as yet, but UK power company Innogy, developer of the Regenesys system, (“uåX˜äŠÊ˜·³Ç, October 2000), believes that by 2010 the global market for storage might be around 15,000 MW a year.