Windpower

Form of solar energy, winds are created by the differential heating of the Earth

About 2% of solar energy goes into making winds. This is still about 10 times more energy than we currently use on a global scale.

Problems include reliability and distribution.

Old form of energy. Windmills, sailing ships, etc. date back thousands of years.

Typical efficiency is about 30%. Maximum theoretical efficiency is thought to be about 60%.

Readings and web sites to visit:

National Wind Technology Center: take the tour (required)

http://www.nrel.gov/wind/index.html

Department of Energy's Wind Energy Program. Read the section: How Do Wind Turbines Work? (required), http://www.eren.doe.gov/wind/

How does it work?

Technology is simple, use wind energy to turn fan blades, which turn the turbine, and you now know the rest.

Technology development is in more efficiently capturing wind (blade types) and in making more robust towers that can work in high winds.

High winds are a problem as they can damage the windmills.

We want to position wind turbines in areas of constant wind, yet these areas typically have high winds as well.

System is simple…

Wind turns blade, gears used to increase speed of generator

Fan types

Blades: most efficient, about 40%. About 150 feet tall; winds are more constant above the ground.

Savonius Rotor: advantages include generator at ground level (easier to service) and no directional mechanism required. Less efficient, about 30%.

Windpower potential:

Energy units are watts per meter squared

Useful energy is mostly above 300 watts per square meter.

Percent land area with useful windpower potential

Potential is greatest in mid west plains states.

Montana, Wyoming, Colorado, New Mexico, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, Texas, Iowa and Minnesota have more than 90% of US potential.

Because of subsidies, most wind power in the United States is produced in California (Altamont Pass, for example, below);

during the 1980's, many wind farms built, especially in California, because of tax breaks in that state given to investments in renewable energy.

As of 1995, there was not a single windmill in South Dakota, yet the potential there is many times more than in California.

Internationally, Denmark is a major user of wind power and a major producer of wind power technology.

Issues to consider

Reliability is a key issue, as the wind does not always blow. Hence, wind energy can augment, not replace, more reliable energy forms.

Wind power is best used as a local source of energy, as each tower generates only a small amount of energy

But…while many windmills dispersed about communities makes the most sense from a production point of view, it does not make sense from an aesthetic point of view.

Drawbacks also include their impact on the scenery, killing of birds, and radio-TV interference.

Costs

Cost is very competitive, currently about 5 cents per kilowatt-hour.

This is down from 7 to 10 cents per kilowatt-hour in 1995 and 15 cents per kilowatt-hour in the 1980's.

This is another example of subsidies creating a viable market.

It is estimated that the costs could be lowered to 3-4 cents per kilowatt-hour as wind technology improves.

Improvements in technology may also open less windy areas up for economically useful and viable wind power.

Bottom line for windpower

Overall potential is about 10% of US electricity needs, with caveats for reliability.

This is if we blanket the areas with useful wind energy with windmills, about 50 million windmills, or one every 10 square kilometers (spacing to avoid interference with each other).

Probably 1 to 2% of electricity is a more reasonable estimate for future potential.

Keep in mind that electricity needs are only about 1/5^th of our total current energy needs.

Current Wind Energy Program budget is $29M… this is not much!