The Subtleties of Wind Energy in Washington State

There have been a number of stories in local media about wind energy in Washington State, including questions about its availability throughout the year.  So let's examine the wind energy potential of the State--perhaps some aspects will be surprising.

A good place to start is the NREL (National Renewable Energy Lab) maps of annual wind speed at 80 meters above ground level, high enough to be applicable to giant wind turbines  (see below).   

You might think that Puget Sound is windy, but that is simply not the case; only along the coast is wind sufficient for wind energy in western Washington  (the orange and red areas).  

The crest of the Cascades and its eastern slopes are a different story, as are several areas over southeastern Washington.   Some decent wind locations.  The best region includes the hilltops near and east of Ellensburg, a region where wind turbines are now everywhere. And the hills surrounding the Columbia Gorge, from The Dalles to Walla Walla, are also good wind energy locations.

The origin of the strong winds from the Cascade crest eastward

There are two major sources of these winds.

First, there are the strong westerly (from the west) winds of the cool season, associated with the jet stream and powerful storms coming off the Pacific.  Such westerly winds are accelerated over the Cascade crest and can remain strong and even accelerate as they descend the eastern slopes of the Cascades.   Hilltops in eastern WA can get a piece of it.   But often the strong inversion (temperature increasing with height) capping the Columbia Basin during winter, often prevents strong westerly wind from getting to lower elevations of eastern Washington during the cold season.  Another reason why the hilltops are favored for wind turbines.

Second, there are the warm-season westerly winds that increase each afternoon and evening during summer.  Eastern Washington is much warmer than western Washington during the summer, and the warmth causes pressure to fall east of the Cascade crest during the day.  Over the ocean, the eastern Pacific high-pressure area is in place much of the summer.  With high pressure offshore and lower pressure over eastern Washington, air accelerates down the eastern slopes of the Cascades during summer afternoons and evenings.   You can think of it as a giant diurnal (daily) sea breeze.

But why are winds so strong around Ellensburg?  

Because there is a weakness in the Cascades called the Stampede Gap, which provides a favored conduit of strong winds from western to eastern Washington.  This gap enhances winds at major wind energy facilities around Ellensburg, such as the Wild Horse Project (see terrain map below from my book).

The near sea-level gap of the Columbia Gorge can also aid in allowing strong winds to reach some of the wind energy projects near the Columbia River.

Are the winds always there?

If one puts up a wind energy project, it would be nice if reliable strong winds were there all the time, but that is unfortunately not the case for the windy locations in Washington.  And it would be useful if wind energy availability corresponded with energy demand, but that is not necessarily the case either.

 Most potential wind energy sites in Washington have a substantial seasonal variation of wind.  To illustrate how wind varies with season, below is another plot from my book showing winds at various locations around the State.  Hoquiam on the coast and Seattle in Puget Sound have their strongest winds in the winter and substantial declines during the summer.   Walla Walla, with some wind turbines on nearby hills, has the strongest winds from April to September, but they really aren't that much stronger than during winter.  

But Ellensburg is a different animal. Very strong winds during the summer, but weak winds during the winter.  

So you see the problem?   Our primo wind generation area has the strongest wind during the summer when power demand tends to lessen over Washington State (less electric heating and lighting is required during the summer).  But the summer wind energy peak could be very valuable for us if electric car usage expands or if we need more electricity for air conditioning due to global warming.

According to a local wind-energy expert, Dr. Justin Sharp, the higher hills in portions of eastern Washington are sufficiently tall to get a piece of the westerly winter winds and thus offer more year-round energy potential. 

As discussed in the media, a wind energy project is planned for the Horse Heaven Hills (see map)

Using the NREL wind site, Dr. Sharp plotted the wind speeds throughout the year at a location in the center of the proposed Horse Heaven Hills project (winds shown below, months are noted on the x-axis, wind speed in mph). Stronger in the winter and weaker dring the summer.

In contrast, a site near the Columbia Gorge in Oregon (Klondike area, see map) has its maximum winds, and thus potential, generation in summer (see below)

You can see why it is important to have lots of wind turbines at different locations and elevations--it helps spread out the generation across the year--which is a good thing.

Finally, it is interesting to note that although wind energy may be a useful part of the mix in Washington State, our wind energy potential is in the bush leagues compared to the Great Plains of the U.S., which might be considered the Saudi Arabia of wind energy (see NREL wind map below).  Absolutely huge wind energy potential from the Dakotas to Texas.