Wind Energy Solution: Wires Across the Water

by Bill Chameides | April 13th, 2010
posted by Erica Rowell (Editor)

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A new study of wind power may have solved the intermittency problem. (NREL)

The rap on wind energy has been you can’t depend on it. Maybe not.

How many times have you heard this: Renewable energy is the wave of the future. And how many times have you heard someone retort with something like: Renewables are great but they’ll never replace good ole fossil fuels. The sun doesn’t always shine, the wind doesn’t always blow, and highest wind speeds tend to be strongest at night.

This intermittency problem has so far proved a big stumbling block for upgrading our energy system. Who wants to forgo their favorite TV show or do without air conditioning when the wind goes south, so to speak? Few if any, and so, the argument goes, only something like a fossil fuel plant can provide the dependable, continuous electricity we demand — wind energy is just too intermittent to provide the baseload of electricity that underpins our energy system.

The bottom line to date: build all the wind turbines you want, but forget about doing without traditional fossil fuel plants.

Where It’s at With Wind: Location, Location, Location

The intermittent nature of renewable power seems like a powerful argument against over-reliance on it.

But wait a second. Any meteorologist will tell you that while it’s true winds wax and wane, when they stall in one location, they’re certainly blowing somewhere. So why can’t we just create a grid that connects wind turbines over a large geographical region and draw energy from them all? When winds are weak in one part of the region, wouldn’t there be sufficient winds in another so that on balance the combined system would provide a fairly stable, constant source of electricity?

That’s the question Willett Kempton of the University of Delaware and co-authors addressed in a paper published last week in the Proceedings of the National Academy of Science. The authors considered a hypothetical interconnected system of offshore wind turbines extending along the U.S. East Coast from Maine to Florida. Using five years of wind data, they then estimated the amount and variability of electricity that the system could generate.

Their analysis shows that such an interconnected regional system can indeed provide a relatively stable electricity source, mimicking the kind of baseload that one typically gets from a networked fossil-fuel plants.

Strategically Pooling Wind Sources

It’s a simple idea. If you connect wind farms situated far enough from each other that they experience different large-scale weather patterns, you increase that likelihood that when one area has poor wind, a distant wind farm will have better wind. This is just what Kempton et al found: more specifically, while the outputs of two distant stations could change by more than 50 percent in an hour, the combined capacity along the Eastern seaboard changed by only by 10 percent. Such performance mimics fossil-fuel baseload power in two important ways:

  1. The total power output of the connected wind farms would change slowly, providing time to ramp up other power sources as needed; and
  2. Connecting the hypothetical farms appears capable of producing the mid-level power that provides our current (outdated) grid’s backbone.

Study: Yes, Wind Was Intermittent, but It Never Stopped Completely

As to the intermittency problem, the authors found that over the course of the study’s five years, while wind output was not continuous at every station, wind output never dropped to zero over the entire system. This is an interesting observation, especially considering that individual fossil-fuel plants do not run continuously either — what makes them reliable is that they are connected via a grid so that when one plant goes down, power can be produced elsewhere.

Orientation could also maximize power output. Kempton et al found that weather patterns along the East Coast tend to move in an east-west direction, so having wind farms spread out along such a vector would enable them to capture more wind over more days than if they were aligned solely in a north-south pattern.

An interesting implication of the Kempton et al work is that while the current strategy for siting wind turbines is to look for the windiest sites in a given location regardless of its wind diversity, the authors point out that it might be more effective “to optimize grid power output by coordinated meteorological and load analysis of an entire region.”

So the solution to a perplexing and complicated problem — supplying continuous energy from a variable source — could have a fairly simple solution: make connections, create a network, share the resource. Sound familiar?

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