Surplus Renewable Energy: An Update

Source: MATTHEW L. WALD • New York Times • Posted: Thursday, February 9, 2012

The Kittitas Valley wind farm near Ellenburg, Wash.

Matthew Ryan Williams for The New York Times. The Kittitas Valley wind farm near Ellenburg, Wash.

Last year I wrote about sudden surges in renewable energy that set up a conflict between wind producers in the Pacific Northwest and the Bonneville Power Administration, a federal agency that runs hydroelectric dams and the regional grid. When unseasonable storms created a simultaneous surplus of wind and water, Bonneville gave free power away but still had to deal with an oversupply that could overwhelm the grid.

Eventually it resorted to unplugging the wind machines because routing excess water around its dams could create excess bubbles in the river, hurting salmon. The Federal Energy Regulatory Administration eventually ruled that Bonneville had been wrong to unplug the machines because this was discriminating against the wind producers, and this week, Bonneville proposed a monetary settlement with them.

Bonneville proposes to share the damages incurred by the wind producers, who not only lose the value of their production when their machines are turned off but also the federal production tax credit.

But at a two-day National Electricity Forum sponsored by the Energy Department and others, the federal energy secretary, Steven Chu, on Wednesday proposed a different set of solutions to the problem, which is likely to emerge elsewhere as installations of renewable energy expand and systems have to cope with surges or deficits of power they cannot predict.

One solution would be to break down the barriers between utilities so that the variability of generation can be leveled out over a larger area, Dr. Chu suggested. Routing more power to California would be a good first move, he said.

(Bonneville does not agree; renewable energy generation tends to peak in California at the same time that it does in the Pacific Northwest, the agency says.)

Another would be using batteries, the secretary of energy said. The problem is that at the moment, the batteries needed to store just one kilowatt-hour (the amount needed to run an window air conditioner for an hour) cost about $350.

That is steep, given that the average price of that amount of energy is about 11 cents. But at $100, Dr. Chu said, batteries would “go viral’’ and change the energy equation.

But there are simpler solutions, the secretary said. He said he recently visited a medical center in Houston that ran a power plant that produced both electricity and steam and could run at very high efficiency when both were needed. The problem, Dr. Chu said, is that at some hours, especially at night, there was not much need for the steam. So the medical center was using it to run a cooling device that was usually a component of an air conditioning system.

In this case, it was simply chilling water in a tank that could be used to cool the building the next day. “The amount of energy needed to keep that tank cold is one-tenth of what you’d need to chill it,’’ he said, describing a method of storing energy as cold water instead of as electricity.

There are “more exotic” forms of storage that take up less space — making ice, for example — “but water works just fine,” he said.

As the use of renewable energy spreads, some companies are storing energy as heat rather than cold. And some are harnessing batteries at the point of generation.

Dr. Chu described a synergy between batteries for plug-in hybrid or electric cars and batteries for the grid. “If I look at the world 10 years ago versus today, we were kind of a sleepy outpost’’ for batteries, he said, with no demand beyond “laptops, some power tools, and toothbrushes.”

“And now they’re saying it’s a $150 billion market,’’ he said.

Dr. Chu predicted that some of that would spill over into the grid. Until then, Bonneville proposes that its customers share the costs of unplugging the wind machines during times of high river flows with the wind producers.