Wind Turbines

In the coming years the global wind turbine market is projected to be $65 billion per year. The worldwide leader in wind power is Germany, having invested $9 billion in it. In 2007, her 20,000 wind turbines generated 5% of electricity consumption, but Germany is running out of places where new turbines can be located. The second largest user of wind power is Spain. The DOE estimates that by 2030 it could reach 20% of American electricity capacity. Electricity generation capacity is growing at an annual rate of 30% and in 2007 reached 17 gW. In the United States, wind-based total energy capacity is around 1% of the national electricity generation capacity and is nearing 15 gW (Texas: 4.3; California: 2.4; Minnesota, Iowa, Washington and Colorado: about 1.2 ea.; Oregon, Illinois and Oklahoma about 0.8; and New Mexico and New York: about 0.5 gW). The largest wind turbine suppliers include General Electric Energy, Siemens, Power Generation, Vestar Wind Systems, Aero Vironment, Clipper Turbine Works, Sualon Energy, and Gamesa Corp.

In Texas, 3% of the electricity is already being generated by wind turbines and a fivefold increase is projected by 2012. The highest wind potentials are in Texas, Montana, and the Dakotas. These states are sparsely populated and do not have good electricity transmission. Therefore, an important aspect of converting to a renewable energy economy is to develop a nationwide electric grid.

The size of wind turbines has also increased as new and lighter construction materials have become available. Today, thousands of 75 m (250 ft) tall wind turbines with 45 m (140 ft) wings are in operation in Texas and in many other locations, each generating about 1 mW.

In May 2007, the National Academy of Sciences released a study indicating that by 2025 the use of wind turbines could reduce the nation's CO2 generation by 4.5%. In the United States, between 2000 and 2006, the quantity of electricity generated by wind farms quadrupled.

Figure 1.20 illustrates a typical wind farm. The DOE estimates that in the next 15 years wind generator capacity in the United States will reach between

figure 1.21

Grid connected solar and wind energy installations. (Left) Grid connected home in Colorado meets nearly 100% of the homeowner's annual electric needs. (Right) Grid connected wind turbine installation. (Courtesy of EERE/DOE.)

figure 1.21

Grid connected solar and wind energy installations. (Left) Grid connected home in Colorado meets nearly 100% of the homeowner's annual electric needs. (Right) Grid connected wind turbine installation. (Courtesy of EERE/DOE.)

20 and 70 gW, which is 2 to 7% of the national electricity generating capacity. Their share of electricity production will naturally be much less because wind turbines do not operate continuously. In Europe, some estimates suggest that if fully exploited, they could meet 30% of their electricity needs by wind power.

The wind turbine-generated electricity is already cost competitive (5-9tf/ kwh) with natural gas-based electricity and in some locations also with nuclear- or coal-based electricity. During the last few years, the cost of wind turbines in the United States has been increasing because the price of commodities and the value of the Euro have been rising (most turbine components are imported from Europe).

In many parts of the world, government support is available to finance wind turbine installations. In the United States, the production tax credit for wind-generated electricity is 1.9i/kWh. This, in 2006-2007, cost the treasury $2.75 billion. In California, for example, a $32,000 wind turbine (about 12 ft in diameter and 30-100 ft tall) is supported by a $16,000 state rebate.

The average generating capacity of a "home turbine" in the United States is 2-10 kW, and the federal government is considering a one-time credit of $3,000/kW. For household applications, the cost of a 3 kW wind turbine is about $6,000 (Hgeneratorsâ„¢). The daily production of a 3 kW generator is about 20 kWh/d if the wind is blowing for 210 h/month and the average wind velocity is 12 m/s. If the generated electricity exceeds the needs of the home, it can be stored by sending it to the grid (Figure 1.21). Naturally, it can also be stored in batteries or in the chemical energy of H2. If H2 is generated, it can also be used as transportation fuel.

It is estimated that to generate and liquefy 10 tons of LH2 per day would require a wind farm with a 100 mW rated (a 30 mW average) capacity. This installation would call for about 200 wind turbines with 40 m spans at an installed cost of about $75 million. Calculating at a 20-year payback, the cost of electricity would be about 6i/kWh, and the cost of 1 kg of LH2, about $7.*

* nTheWind.f.pdf.

In many locations, excess electricity is accepted by power companies on a "net metering" basis (meters "run backward" when renewable energy is being sent into the grid). The accumulation of this excess can compensate for (or exceed) the amount of electricity needed when there is no wind. The Dutch utility Nuon reports that in 2005 the electricity cost on the spot market was 5.6i/kWh when there was no wind, and it dropped to 3i/kWh when the wind speed reached 13 m/s, because the fuel (wind) is free.

A small company, General Compression, is experimenting with the direct storage of wind energy in compressed air. The air-compressing windmills eliminate the use of electrically driven compressors and thereby increase the efficiency of the operation. In another new development the Alameda, California-based Makani Power Inc. is developing high-altitude wind technologies.

In order to meet wilderness preservation considerations, it has been suggested that birds, bats, and other animals will be better protected if slowly rotating, larger blades are utilized. As to the aesthetic aspects, some artists are working on coming up with more aesthetic shapes and colors for these structures.

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