Batteries that can store and release energy from wind farms (wind mills) are becoming more cost effective and are expected to increase the competitiveness of wind energy. Coal plants can increase power production to meet high demand times of day, then decrease it, but wind doesn't offer that option. A common power storage technology, a pumped hydro plant, involves pumping water uphill when demand is low, from a lower reservoir to to a higher one. "At hours of peak demand the water flows back down through a turbine, creating electricity." The new generation of batteries may achieve the same goal at less cost.
New York Times
The rapid growth of wind farms, whose output is hard to schedule reliably or even predict, has the nation’s electricity providers scrambling to develop energy storage to ensure stability and improve profits.
As the wind installations multiply, companies have found themselves dumping energy late at night, adjusting the blades so they do not catch the wind, because there is no demand for the power. And grid operators, accustomed to meeting demand by adjusting supplies, are now struggling to maintain stability as supplies fluctuate.
On the cutting edge of a potential solution is
Renewable goals can be met, many in the industry insist. But if the energy source is intermittent, “you can’t do that without batteries of some sort,” said Peter Rosegg, a spokesman for the Hawaiian Electric Company.
His company has agreed to buy electricity from a wind farm on the northern
The spot is one of
30-megawatt wind farm, which will have enough power to run about 30 Super
Wal-Marts, will have Xtreme Power of
Computers will work to keep the battery exactly half-charged most hours of the day, said Carlos J. Coe, Xtreme Power’s chief executive. If the wind suddenly gets stronger or falls off, the batteries will smooth out the flow so that the grid sees only a more gradual increase or decrease, no more than one megawatt per minute at some hours of the day.
The battery system can also be used for arbitrage, storing energy at times when prices are low and delivering it when prices are high. It can hold 10 megawatt-hours, which is as much energy as a 30-megawatt wind farm will produce in 20 minutes if it is running at full capacity. That is not much time, but it is huge in terms of storage capacity.
Neither First Wind nor Xtreme Power would say what the project cost, but publicly disclosed figures put the project in the range of $130 million, with about $10 million for the battery. The Energy Department has provided a $117 million loan guarantee.
Across the country, it is proving hard to predict the cost and the value of power storage to consumers. The electricity stored in off-peak hours could be quite low in cost, and prices at peak hours could be quite high. If the reliance on renewable energy reduces the need to burn coal and natural gas, that would yield an additional advantage.
Mr. Coe estimated the battery system’s round-trip efficiency — that is, the amount of electricity the batteries could deliver per megawatt-hour stored in them — at over 90 percent. If that figure is borne out, it would be a significant advance from the largest form of energy storage now in general use, pumped hydropower, whose efficiency is put at 70 to 85 percent.
At a pumped hydro plant, off-peak electricity is used to pump water from a reservoir at a low elevation to one at a higher one. At hours of peak demand the water flows back down through a turbine, creating electricity.
Electric companies are using other strategies for storage and frequency
Atop each flywheel is a device that can be a motor at one moment and a generator the next, either taking energy and storing it in the flywheel or vice versa. The Energy Department provided a $43 million loan guarantee to assist in the $69 million project.
The Energy Department is also supporting storage projects that rely on compressed air. Surplus electricity is used to pump air into an underground cavity; when the electricity is needed, the air is injected into a gas turbine generator. In effect, it acts as a turbocharger that runs on wind energy captured the previous night, instead of natural gas burned at a peak hour.
The department is contributing to two projects explored by PSEG Global, an
affiliate of Public Service Electric and Gas, based in
Both will be used to store power made in off-peak periods and deliver it in peak times, when prices are higher, said Paul H. Rosengren, a spokesman for P.S.E.G.
In Presidio, Tex.,
American Electric Power and MidAmerican Energy Holdings have just completed
four-megawatt battery system that is not tied to any particular wind farm
but is intended to improve reliability in the town, served by only one major
transmission line. American Electric Power already has smaller batteries working