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Part 5 - The Future of Wind Power
Multimegawatt Wind Turbines Near Adair, Iowa, USA
Multimegawatt wind turbines near Adair, Iowa, USA
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Finally Time for Wind Energy?

In the 1990s, the California wind farm market began to be affected by the expiration or forced re-negotiation of attractive power purchase contracts with the major California utilities: Southern California Edison and Pacific Gas and Electric. And much of the existing inventory of 1980's wind turbines were really an albatross around the wind industry's neck.

Renewal was needed, and -- buoyed by "green power" initiatives in Colorado, Texas and elsewhere -- U.S. wind energy development resumed in 1999, with a much broader geographical base.

A variety of new wind projects were installed in the U.S. in the late '90s, including a cluster of Zond Z-40 turbines (at left) operated for a utility in southwest Texas, a wind plant of 46 Vestas machines planned for Big Spring, Texas, a 10-megawatt wind plant in Northern Colorado, a number of plants in the upper midwest, and the "re-powering" of some projects in California. Some of these involve foreign machines manufactured in the U.S. There's a sense that the industry is finally on the move again, with over 2000 megawatts of new capacity planned for 2001 in the U.S. alone. Existing and planned U.S. projects can be explored using the Wind Project Map maintained by the American Wind Energy Association. 

The cost of energy from larger electrical output wind turbines used in utility-interconnected or wind farm applications has dropped from more than $1.00 per kilowatt-hour (kWh) in 1978 to under $0.05 per kWh in 1998, and is projected to plummet to $0.025 per kWh when new large wind plants come on line. The hardware costs of these wind turbines have dropped below $800 per installed kilowatt in the past five years, underpricing the capital costs of almost every other type of power plant.

It's difficult to accurately compare the costs of wind plants and fossil fuel plants because the cost drivers are so different. Low installed-cost-per-kilowatt figures for wind turbines are somewhat misleading because of the low capacity factor of wind turbines relative to coal and other fossil-fueled power plants. (Note: "capacity factor" is simply the ratio of actual energy produced by a power plant to the energy that would be produced if it operated at rated capacity for an entire year.) Capacity factors of successful wind farm operations range from 0.20 to 0.35. These can be compared with factors of more than 0.50 for fossil-fuel power plants and over 0.60 for some of the new gas turbines.

However, the use of "capacity factor" is also misleading because wind has a "rubber" capacity factor that varies with the density of the wind resource. But that wind resource is constant for the life of the machine and is not subject to manipulation or cost increases. One reason why fossil fuels are so popular with investors is that many of the risks are passed on to consumers. Fossil fuel shortages result in an increase in revenues for investors, who are actually rewarded for: 1) speeding the depletion of a nonrenewable resource or 2) not investing enough of their profits in support infrastructure, which (as we saw in 2000-2001) drives up prices. If a big oil coal or gas company could start charging for the wind, they would make sure that wind power development happened. In late 1996, with the purchase of Zond Systems by Enron (a now-defunct gas mining and distribution company), the possibility of this happening became very real.

Even though Enron proved to be a poor steward for the Zond technology, the subsequent purchase of what was one of the only viable Enron divisions by GE Energy in 2003 maintained U.S. visibility in the large wind turbine market. In 2015, GE was still the largest U.S. manufacturer of wind turbines, although recently overtaken by the Danish company Vestas as the largest manufacturer and installer in the world.

Wind farm of Zond-40 600kW wind turbines in Texas. Present wind turbine siting restraints often require a remote area that is not highly prized as a wildlife habitat or recreational area. But see below.

Megawatt-scale Vestas wind turbines installed near Sacramento, California with the help of a large crane.

Three large turbines operating on a family farm in Wyoming County in Western New York, November, 2003. Power sold to Niagara Mohawk.

Lowering the Cost-of-Energy Bar

Since the late 1970's the U.S. cost goals for wind power have continued to be about $0.04 per kilowatt hour, despite inflation. Wind turbines have consistently been able to get close to that level, but until recently, by the time they got there, another reduction in the cost of non-renewable fossil fuels had taken place and the bar was lowered further.

Cost per kilowatt hour figures of $0.05 are now commonly achieved by large U.S. wind turbines in 17 mph or better wind regimes, where capacity factors of over 0.40 can be achieved. Such costs are virtually competitive with natural gas turbine plants. That means that (factoring inflation) the wind energy cost goals of 1980 -- which seemed daunting or impossible at the time -- have been met several times over. The major improvements have been refinements in gearbox and power train design, rotor efficiency and reliability, and electronics. Efficiencies in manufacturing, made possible by higher production volume, also have played a major role. This fact should be remembered by those doubting the achievability of recently refigured cost goals for "advanced" systems -- which are now closer to $0.025/kWh.

The lower cost of energy from advanced turbines is partly a result of higher efficiencies and rotor loading made possible by additional improvements to rotor design, shedding of fatigue loads provided by teetered hubs and flexible structures, and other innovations such as variable speed operation. But reduced weight and material usage and higher reliability are perhaps more important factors in the cost equation.

Costs of smaller systems vary widely, with installed costs from $2000 to $3000 per installed kilowatt. Energy costs for small turbines of $0.12 to $0.20 are still the norm in the U.S. market.

An early German Enercon machine featured a huge, low speed "ring" generator.

Concepts like the ultra-light Wind Eagle could one day revolutionize wind energy
conversion technology

Worldwide, there are 14 major manufacturers of large, utility-scale systems, marketing 200kW to 5.0 MW systems that primarily use the three-bladed configurations, with various type of control systems. There are a number of other smaller companies working on advanced configurations, such as two-bladed, stall control machines with teetering hubs. News on these developments is available from the major industry magazine, The Windpower Monthly

The more advanced configurations (from an aerodynamic standpoint at least) were developed under the U.S. Department of Energy Advanced Turbine Program. 

European manufacturers like Tacke, Micon, Vestas, and Enercon (at left) commercialized turbines with more conventional rotors, but featuring such important innovations as low speed generators and complete variable speed systems incorporating advanced power electronics. GE Energy (which purchased the wind division of defunct Enron) adopted the European design philosophy in the U.S., with its merger of the technical expertise of Zond and Tacke. 

The result of mergers was that, by 2001, there was a virtual internationalization of the wind turbine industry and research community. In 1995, pundits like Paul Gipe could claim that the Europeans' use of smaller machines with conventional aircraft airfoils meant that low tech had beaten high tech in the wind business. In 2001, with European wind turbine power ratings pushing 2 megawatts, Denmark's Riso Laboratories touting its new wind turbine airfoil designs (modeled closely after pioneering activities in the U.S.), and the U.S. company Enron marketing machines from both the U.S. and Europe, there was really very little difference between European and U.S. technology.

One of the latest innovations being investigated in the U.S. and Europe is the addition of a hinge at the nacelle-tower attachment, allowing the turbine to "nod" up and down in response to turbulence and wind shear (the difference in wind speed at the top and bottom of the  rotor disk). This configuration has been tested at Denmark's Riso Laboratory and promised substantial reductions in rotor and drive-train loads and in control system costs. A model intended for commercial development operated in California for several years and has been investigated by the National Wind Technology Center. However, such innovations may not be necessary for wind to meet its cost goals for several years. 

One of the last remaining major areas of controversy is the issue of two versus three blades for large wind turbines. Theoretically, a two-bladed machine should be less expensive and more efficient than a three-bladed one. But considerable refinements are still needed to offset the greater stability and lower per-blade loads of three-bladed designs. And the optical illusion of speed fluctuations and out-of-plane rotation associated with two-bladed machines makes them less attractive to some onlookers. Time will tell if one design will win out or if both will be able to exist in specific applications.

Based on the mid-1980's ESI-80,
the 2-bladed, AWT 26-meter machine was a contemporary expression and refinement of the Hutter design philosophy. Whether or not such designs will ever be widely commercialized is uncertain.

The Future Is Now

In the near future, wind energy will be the most cost effective source of electrical power. In fact, a good case can be made for saying that it already has achieved this status. The actual life cycle cost of fossil fuels (from mining and extraction to transport to use technology to environmental impact to political costs and impacts, etc.) is not really known, but it is certainly far more than the current wholesale rates. The eventual depletion of these energy sources will entail rapid escalations in price which -- averaged over the brief period of their use -- will result in postponed actual costs that would be unacceptable by present standards. And this doesn't even consider the environmental and political costs of fossil fuels use that are silently and not-so-silently mounting every day.

The major technology developments enabling wind power commercialization have already been made. There will be infinite refinements and improvements, of course. The eventual push to full commercialization and deployment of the technology will happen when the consequences of climate change are finally recognized and admitted.

Status Report, 2014

  • Over the past decade, world wind power capacity grew more than 20 percent a year.

  • By the end of 2014, global wind generating capacity totaled 369,000 megawatts, enough to power more than 90 million U.S. homes.

  • China generates more electricity from wind farms than from nuclear plants, and has an easily-reachable wind power goal of 200,000 megawatts by 2020.

  • In nine U.S. states, wind provides at least 12 percent of electricity. Iowa and South Dakota each generate more than 25 percent of their electricity from wind.

  • In the Midwestern United States, contracts for wind power are being signed at a price of 2.5 per kilowatt-hour (kWh), which compares with the nationwide average grid price of 10–12 per kWh.

  • A wind farm can cover many square miles, but its footprint typically comes to just over 1 percent of the total land area covered by all of the infrastructure of the project.

  • Wind energy yield per acre is a powerful argument against the intransigence of some oil and gas industry-supported politicians in the US. A farmer in the Midwest U.S. can obtain a lease for a turbine that generates $300,000 worth of electricity per year and receive royalties of $3,000 to $10,000 per turbine each year. This compares favorably with an acre of corn that would yield only $1,000 worth of fuel-grade ethanol per year, without using the precious water resources or the fertilizer and pesticides required to grow corn.

Xcel Energy Ponnequin wind farm in northeastern Colorado.

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