Utility eases off back-up demand -- Japan learns about wind

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Japanese utility Tohoku Electric Power is permitting up to 100 MW of wind power capacity to link to its grid without the megawatt-for-megawatt generation back-up capacity that it previously thought necessary. The policy shift comes after a re-evaluation of how much reserve capacity is actually needed to cover for the addition of wind energy to a power system.

The 100 MW represents two thirds of a call for proposals for 160 MW of wind power issued by Tohoku for the current fiscal year, which runs to March. In recent years, Tohoku has not permitted "large scale" wind plant, which it qualifies as single turbines with rated capacities of 2 MW and more, to be connected without storage back-up. But the company now says a campaign by Japan's electric companies promoting the use of electric power in the home over gas has increased power consumption overnight, making the integration of wind power into the network easier.

For wind project developers in Japan, who have bitterly complained about power storage requirements that unnecessarily double the cost of wind energy, Tohoku's change of heart is likely to be welcome. In return for easing off on the back-up requirement, however, Tohoku demands that owners of prospective wind farms agree to curtail production in periods when grid supply exceeds demand.

Of the remaining wind capacity sought by Tohoku, 50 MW must still be equipped with power storage batteries or other means of "easing" fluctuations in output, the company says. Japanese utilities and government experts often express concern that variability in wind power causes instability on the grid. The wind sector, for its part, refutes the claim as exaggerated and unsubstantiated.

The remaining 10 MW of capacity is to come from "medium" sized plant between 20 kW and 2 MW, to be idled during periods of low demand, but requiring no equipment to manage power output.

The 160 MW tender was to close on January 23. Fifty-six companies attended a mid-December explanation session on the invitation for proposals. Tohoku expects to announce the winning bids by the end of next month.

In November, Tohoku raised the cap on the estimated maximum capacity of wind power it could accommodate on its grid without requiring dedicated reserves from 520 MW to 850 MW. The company says its higher cap on wind is based on data collected in the six years to March 2008, at which point the company had contracted a total of 470 MW wind power from 65 plant. "It is necessary to increase wind power on the grid in a step-wise fashion," to maintain quality of supply, says Tohoku.

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