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Energy Blog: NW Wind Power – Too Much of a Good Thing?
By Andy Silber

Too Much of a Good Thing?

The Challenges of Wind Development in the Northwest

It was recently reported that the Northwest power grid operators (primarily the Bonneville Power Administration (BPA)) plan to instruct wind farm operators to turn their turbines off occasionally this spring, because our grid can’t handle all of the power. Why are we turning off wind farms now and not shutting down Washington’s only coal power plant until 2025?

We often hear that the problem with wind power is that it is an “intermittent” source: the turbines generate electricity when the wind blows, not when the demand is high. This is also true of solar, but it’s less of a problem because it is more predictable (they tend to generate more electricity during the day than at night) and that power generation is high when demand is high. This is especially true in areas where solar energy is plentiful and the peak demand is caused by air conditioning, like LA and Phoenix.

What we don’t often hear about is the intermittency of hydro. Most of us imagine a dam holding back water, waiting until we need it. The truth is a bit more complicated. I’ll take Seattle City Light’s (SCL) situation as an example. SCL has 4 main dams, 3 on the Skagit River (Gorge, Diablo and Ross) and the Boundary project on the Pend Oreille River in Northeast Washington. For 3 of these dams, the amount of water flowing into the “lake” behind the dam in a given day is about equal to the amount of water flowing out of the lake that day: there is very little storage. SCL does turn most of the generators down at night, saving the water for the time of day when demand is highest. The other complication is the salmon in the Skagit River. The salmon runs are very healthy on the Skagit, in part because of SCL’s salmon first policy in running the hydro facilities. The output of the most downstream dam (Gorge) is relatively constant when the salmon are in the river, because that leads to healthy salmon runs. Ross Dam and Lake are the exception. Ross can hold enough water to run for months. So the level of Ross Lake is lowered during the late winter, waiting for the spring run-off. When that happens Ross Dam is turned way down. There’s still enough water from the melting snow nearby to keep Diablo and Gorge producing a lot power.  Meanwhile on the Pend Oreille, the Boundary dam is producing huge amounts of electricity. Even with Ross producing much less energy that it can, our other dams produce more than we need during the spring melt.

The same thing is happening with all of the dams and rivers across the region, including the big federal dams that make up the BPA. There are very few big lakes like Ross that can store much water. In a wet year, like we’re having right now, the wholesale price of electricity plummets for months. We can export some of that power to California via the Pacific DC intertie (which was built as a federal project, not a state or private one), but not all of it. The key to operating the Northwest Grid during the spring run-off is to reduce generation. One way to do that is “spill” water over the dams (i.e. pass water over the top of the dam, rather than through the turbine/generators). This does happen, but it mixes air into the water, which is bad for the fish. Another way is to take a few big plants off-line for awhile. For instance, at the moment the only nuclear plant in Washington State is down for re-fueling.

So when the wind starts blowing in the spring, the grid operators get nervous. The amount of electricity being put into the grid must exactly equal the amount being used. If the dams are already as low as they can go given the constraints of flood control and fish habitat and the Pacific Intertie is at capacity and everything else that can be turned down already has been, they’re in a pickle. Wind operators have an extra inducement to sell their power; they only get their federal production tax credits if they sell the power. They can sell the power at a negative price and still make some money. That actually happens; the wholesale price of electricity can go negative. If you have a power plant that you can’t turn down you need a place for that electricity to go and if needed, you’ll pay someone to take it.