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BPA Testing New Energy Storage Method to Avoid Wind Power Curtailment by Laura DiMugno North American Windpower, April 12, 2012

The Bonneville Power Administration (BPA) has come up with a new method to help relieve some of the electricity oversupply that caused it to curtail hundreds of megawatts' worth of wind energy generation in the Pacific Northwest last year.

BPA, United Electric Co-op and the Southwest Irrigation District (SWID) are testing a procedure that they say has the potential to relieve the oversupply it commonly experiences in the spring, when snowmelt runoff is high.

For the pilot project - which will be conducted in Cassia County, Idaho - BPA will study how adjusting certain irrigation pumping procedures - known as "aquifer recharge" - to help address oversupply. An aquifer is a body of geologic material that supplies groundwater to natural springs and water wells. When rainwater seeps through the soil into an aquifer, it is called aquifer recharge.

Increasing irrigational pumping in times of low electricity demand or decreasing pumping during times of high demand lowers operational costs for SWID, BPA explains. For the pilot project, SWID will pump water from the Snake River in March and November, instead of between mid-April and mid-October, when electricity demand is higher, thus reducing deep-well-pumping costs, BPA explains.

If, after the pilot project is complete, BPA determines that these adjustments are feasible, there could be 50 MW to 100 MW - or even more - of pumping load in that region. According to Lee Hall, BPA's smart grid program manager, these pumps can store excess electricity when there is too much wind power being produced.

"This important test could provide benefits to utilities and irrigation districts across the Northwest," Hall said in a statement. "This practice could save utilities and irrigation districts money, and use pumps that recharge aquifers as a repository for excess electricity created, at times, by high wind and high river flows."

The pilot is just a small-scale project - a 1.8 MW proof-of-concept field test. However, according to Terry T. Uhling, chairman of the Idaho Water Resource Board, the aim is to apply the adjusted practices permanently and on a larger scale.

"The board hopes this can become a permanent program, and that it might be expanded in the future as there are other existing and planned managed aquifer-recharge projects," he said in a statement.

Ongoing controversy

This is BPA's most recent attempt to solve this hotly contested issue. In addition to hydro oversupply due to seasonal runoff, wind generation on the BPA system has also broken records lately. Last month, for instance, wind turbines connected to the BPA grid generated 4 GW - nearly twice as much energy as that generated by coal, gas and nuclear plants connected to BPA's system at that time.

Needless to say, BPA's decision to curtail 350 MW of wind power last spring did not sit well with wind energy generators, which consequently filed a complaint with the Federal Energy Regulatory Commission (FERC).

"This is setting a dangerous precedent for the sanctity of contracts in the Pacific Northwest and the nation, and will greatly jeopardize the development of renewable energy in the region," Don Furman, senior vice president at Iberdrola Renewables, said at the time.

In December, FERC ruled that BPA did, indeed, discriminate against wind power and gave preferential treatment to hydropower. As a result of the ruling, BPA was required to submit a new policy to FERC.

In its first attempt, BPA said it would compensate wind energy producers within its section of the grid for periodically reducing their output when necessary to keep the electricity supply from exceeding demand during high river flows.

When wind energy generators were not satisfied with that proposal, BPA tried again with a new plan, in which it would first work with the U.S. Army Corps of Engineers and the U.S. Bureau of Reclamation to manage federal hydroelectric generation and spill water up to dissolved gas limits.

However, that plan did not address the issue of preferential treatment, either, according to the Renewable Northwest Project (RNP), the group representing wind energy generators.

With this most recent plan, however, BPA may be on the right track. RNP Executive Director Rachel Shimshak told NAW that energy storage is actually one of the steps it recommended to BPA to solve the oversupply issue.

"We think the pump idea is a good one, and we support it," she said. "It is an example of how it's possible to reconfigure the use of existing systems to meet various regional needs. While the BPA pilot is small, it can demonstrate strong future potential."

Nonetheless, it is not a be-all-end-all solution.

"There is no single solution to the seasonal challenge of overgeneration, but a combination of good options to alleviate it is within grasp," Shimshak added. "Accessing existing storage and solutions within the system is an important step."