Intermittency of Wind Power

Wind is created by differential solar heating of the Earth and its atmosphere. The resulting temperature differences involving the land, sea, and air masses and the interaction of air masses with the earth's irregular topography cause air pressure differences that, along with the earth's rotation on its axis, produce wind. Wind is intermittent yet quite predictable on a regional basis and at certain sites and could meet 20 percent or more of U.S. electricity needs without undermining the power grid's reliability. This percentage rises as other dispatchable generating technologies, such as dams and conventional power plants, are used to compensate for wind plant output fluctuations. Energy storage systems are also useful for mitigating the intermittence of renewable energy sources and are discussed later in this chapter.

With sufficient installed wind capacity, wind and other intermittent renew-ables could easily provide 30 percent of the capacity of an electrical grid without energy storage and a much greater proportion of the grid capacity if storage were provided. According to European researchers, "no absolute physical limit exists to the fraction of wind penetration on a large power system."13 However, because wind power (and other intermittent renewables) have a lower capacity factor than fossil and nuclear power plants, wind capacity must be installed at twice or two and a half times the capacity of conventional generation to provide equal average annual energy output.14 For example, for a wind power plant with a 30 percent capacity factor to equal the average generation of a conventional fossil-fired plant with a 60 percent capacity factor, twice as much wind power capacity would have to be installed. Whereas this would not alter the levelized per unit cost of the delivered wind power, it would require twice the initial capital investment for the wind generation.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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