Sunday, June 04, 2006

Wind farm requires purchase of extra energy

Surprise: Reality doesn't live up to the sales claims. From the Helena (Mont.) Independent Record, June 4, 2006:
New Judith Gap wind farm causing headaches on the grid

The clean, green power from the Judith Gap Wind Farm that debuted last fall has been more intermittent than anticipated.

And that is causing problems for NorthWestern Energy, the utility that must balance supply and demand on its transmission lines. ...

In April, the Western Electricity Coordinating Council [WECC] in Salt Lake City sent a letter to NorthWestern saying that its transmission system may have fallen 3 percent short of its minimum control performance standards of 90 percent. ...

"This is unconfirmed and ordinarily this information isn't even made public," he said. ...

Joel Schroeder worked as project manager for Invenergy Wind LLC's Judith Gap project, the largest of the company's four wind farms. Reached at company headquarters in Chicago, Schroeder said wind is by nature intermittent.

"If you have a storm move in and the wind picks up, that will boost production, or if you have the opposite and the wind drops out, you'll lose power," Schroeder said. "It's completely dependent upon the wind."

Everyone knows wind power is variable and that other backup power from coal or hydro or natural gas is needed to fill in the calm times.

However, the hourly ups and downs are harder to manage than expected, [vice president of wholesale operations at NorthWestern Energy David] Gates said.

"The wind's blowing and in that hour, the output goes from 20 MW (megawatts) to 80 MW," he said. "The average is 50 MW, but as control operator we have to manage that move from 20 to 80 MW (on the transmission lines)." ...

You can store water behind a dam. But you cannot store electricity, and that fact creates lots of challenges for delivering power and pricing power.

Engineers may have more elegant explanations, but you can think of a power transmission line as a teeter-totter.

To keep the board level, the supply of power sitting on one side must balance the demand sitting on the other side.

When there is too much supply, the utility has to sell power right now. When demand outweighs supply, the utility must buy more power right now.

Long-range power contracts that run for years are relatively inexpensive. But, like shopping at a convenience store, buying power on the spot market costs more, often far more.

So variability at the Judith Gap project is costing NorthWestern's consumers more, they just don't know how much yet.

... On May 7, more than 30 energy developers, power company representatives and rural electric cooperative executives met in Helena with Gov. Brian Schweitzer's staff to discuss Montana's energy future.

One topic was how to build more wind farms, yet keep the transmission lines balanced.

Dave Wheelihan, chief executive of the Montana Electric Cooperatives Association, said the gist of that part of the conversation was that NorthWestern has had to buy more short-term power than expected to balance Judith Gap.

"You can go out and contract for it, but the pricing will be interesting," Wheelihan said.

He said the utility has purchased another 15 megawatts of incremental power from Avista Energy to balance the load. ...
wind power, wind energy, wind farms