Energy: Something in the Wind

Intriguing new wind machines may finally demonstrate that wind energy is economically feasible as well as clean and infinitely renewable

NORTH DAKOTA may not have much, but it does have wind. Lots of it. Almost the entire state is combed by what wind-energy analysts call Class 4 winds, which average a kite-tugging 13.4 miles per hour at about a hundred feet above the ground. With enough wind turbines capable of running efficiently in such breezes, North Dakota would become the Saudi Arabia of airflow. The state could, in fact, provide 35 percent of the fortyeight contiguous states’ electrical needs through wind alone. Add South Dakota and the figure jumps to about 60 percent. And that’s with much of the land in those two states left out of the picture for environmental or other reasons.

The goals of most wind-energy enthusiasts are more modest; their hope is that by the year 2010 wind turbines running on big “wind farms” in the West, Midwest, and Northeast could supply about five percent of U.S. energy needs. But the higher figures give some idea of the potential and the appeal of this energy source. As a form of solar energy (heat from the sun interacts with the earth’s rotation to create and direct wind), wind is an infinitely renewable energy resource. In several key regions wind tends to blow when it is needed most—during the summer in California, the winter in the Pacific Northwest, summer and winter in the Midwest. It is nonpolluting (although some complain about the visual blight of turbine towers) and highly compatible with agriculture. And in principle wind can fairly easily be turned into electricity: A generator is attached to a large rotor, the blades of which are patterned after aircraft wings, and placed atop a tower. Wind passing through the rotor creates lift that makes the rotor spin, cranking the generator to produce electricity, which can then be fed into a power grid.

But there’s a catch. “Designing a wind turbine that generates power really isn’t a big challenge—people have been doing it for a long time,” says Bob Guertin, the vice-president of engineering for U.S. Windpower, a turbine builder in California. “The challenge is putting a turbine out there that delivers energy at a price people want to pay.” A utilitygrade wind turbine must be easy to maintain and able to produce energy in relatively low winds. And it must be rugged. Gusts and eddies of wind, slamming into a turbine from several directions, cause stresses that are difficult to predict fully. Erecting multiple turbines exacerbates the problem: they’re like fleets of low-flying aircraft, each creating turbulence that can batter the machine behind or next to it. The problem of price has been a particular bugbear in an industry that always seems long on bright ideas but short on cash. To cut costs a decade ago American turbine designers pared weight, a decision that in combination with widespread ignorance of wind dynamics produced disastrous results. Gear boxes ruptured and generators fried. Things got so bad during the early 1980s that wind engineers at the Solar Energy Research Institute (now the National Renewable Energy Laboratory, or NREL), in Golden, Colorado, covered their field labs with thick steel cages to protect themselves from rotor blades that occasionally broke off turbine prototypes and pirouetted through the clear Colorado sky.

Improved maintenance and better turbine siting have made wind turbines much more reliable. Costs have gonedown too, from more than 25 cents per kilowatt hour ten years ago to about eight cents today (a kilowatt hour is enough energy to run ten 100-watt light bulbs for one hour). Precise cost comparisons are extremely difficult, because utilities base their energy prices on widely varying sources and peak loads. But in general energy from wind still costs more than twice as much as energy from natural gas, currently the cheapest energy source, and also more than power from existing coal and hydroelectric facilities. So at present the nickel is the holy grail of the wind industry. If wind turbines can supply power for five cents per kilowatt hour, allowing for installation, capital, and maintenance costs, then wind will be competitive—especially if fossil-fuel prices rise.

The last time wind power was competitive, turbine fever hit California. The rolling hills of Altamont Pass, thirty miles east of San Francisco, are dotted with thousands of wind turbines, most built during the mid-1980s with the help of generous state and federal tax credits and energy contracts. Their disparate designs reflect considerable uncertainty about the most efficient way to tap the wind: some models have two blades, others three; some point upwind and others downwind; some have eggbeaterlike vertical-axis turbines; one is a picturesque Dutch machine with elaborate paddles which conjures up images of the windmills of old. Altamont and the wind farms at San Gorgonio Pass, near Palm Springs, and Tehachapi, near Edwards Air Force Base, generate enough power each year from their 16,000 turbines to supply the residential needs of San Francisco and Washington, D.C., combined. But the tax credits expired in 1986, and the contracts will soon have paid out their fat front-end sums. Few wind machines have been built here in recent years; most builders of these turbines have long since gone bust.

THE EXCEPTION is U.S. Windpower, based downhill from AlJL tamont Pass in Livermore. It has survived largely by operating its own machines, learning to fix and improve what it produced. Today some 3,500 of U.S. Windpower’s model 56100 turbines, a model introduced in 1983, fly at Altamont—roughly half of all the machines there. The 56-100, a 100-kilowatt turbine with a fifty-sixfoot rotor diameter, is perhaps best understood as the Jeep of wind turbines. It’s tough and reliable, but not big or sophisticated enough to come close to the nickel-a-kilowatt-hour ideal. As I toured Altamont Pass recently with Robert Sims, the manager of systems planning for U.S. Windpower, we came across a row of four enormous wind machines standing partly assembled on a ridge. Each had blades fifty feet long and a housing the size of a Chevy van for its generators. These were early production models of U.S. Windpower’s new wind turbine, the 33M-VS, which can create up to 400 kilowatts of electricity—enough to power eighty homes with central air-conditioning. Now that thirty-eight of these turbines are in full operation, it’s the first model in commercial production that is generating power for five cents a kilowatt hour.

Work on the 33M-VS began in 1987, financed by a consortium that consisted of U.S. Windpower, California’s Pacific Gas and Electric, New York’s Niagara Mohawk Power, and the Electric Power Research Institute (EPRI), a Palo Alto—based utility think tank. This group has poured some $50 million into the 33M-VS. To use wind-speak, the 33M-VS is an upwind, active yaw-drive machine with mechanical pitch control. Translation: Its rotor points into the wind, not away from it, so that “wind shadow” from the tower doesn’t increase the loads on the blades of downwind machines. It employs a hydraulic motor-and-pinion assembly to aim itself mechanically. And its three one-ton blades are hydraulically “pitched,” or rotated, to adjust to the wind. The 33M-VS’s big breakthrough, though, is its ability to vary speed. Most turbines turn at a constant speed to produce electricity at sixty cycles per second— the U.S. standard for alternating current. They must do so, however, in varying wind speeds. One solution is to monitor the wind with an anemometer: as winds change, a computer orders hydraulic mechanisms to change the pitch of the blades so that they face low winds directly, capturing more energy, or turn away from high winds, so that not too much torque is passed to the generator. A pitch-control mechanism, however, often ends up chasing its own tail, constantly trying to adjust to wind conditions that existed moments before but have already changed.

The 33M-VS uses an electronic “black box” to adjust its power output, enabling it to spin slowly in winds as gentle as nine miles per hour or turn faster in winds of up to sixty-five miles per hour and still produce sixty-cycle power. That enables it to use pitch control to fine-tune its capture of energy without the problems of pitch lag. It can slough off the stress of a sudden gust by turning faster, allowing the pitch-control mechanism to prompt smaller, less-frequent adjustments.

IRONICALLY, THE greatest challenge to the 33M-VS for wind supremacy comes from a technology that it was in part designed to circumvent. That is the alternative to pitch-control systems and black boxes for managing peak loads: “stall-control” rotors. Stall-control blades are fixed, and are designed so that high winds create turbulent flow on the downwind side of the blade; the blades then lose lift, like those on an airplane trying to climb too steeply. Decreased lift produces less usable torque, so the rotor produces less power. But stall-control blades have had problems. They continue to generate too much lift in high winds, causing generatorbusting power peaks. They are inefficient, in the sense that each turbine in a wind farm steals energy from machines downwind. And in some areas dead insects piling up on the blades can cut power output by as much as half, necessitating frequent, costly cleaning.

If wind power finally takes off, it may be in large part because of Jim dangler, a senior scientist with NREL, a division of the Department of Energy. Tangier, a soft-spoken man in his early fifties, took on the problems of stall-control blades back in 1984, believing that design improvements could yield big dividends at a small cost. His contribution was to understand what wind turbines wanted that the aircraft wings they were patterned after did not: a low-lift airfoil. High lift is the sine qua non of flight. By placing a low-lift airfoil (the curved cross-section of a wing) at the tip of a blade and then blending it into high-lift airfoils at the blade’s base, Tangler and Dan Somers, a freelance airfoil designer, fashioned a blade that performed better in low winds than previous stallcontrol blades but would not overpower the generator in high winds. As a bonus, these airfoils also proved to be significantly less sensitive to bug buildup and pitting from flying sand.

One who immediately saw the potential of the new airfoils was Robert Lynette, an engineer who had left Boeing in 1979 to found his own wind-energy firm, R. Lynette and Associates, of Redmond, Washington. Lynette is nowdeveloping a wand machine called the AWT-26 that employs a blade based on the breakthrough airfoils, along with a slew of improvements gleaned from the years Lynette’s firm spent monitoring some 800 wind turbines under a contract with EPRI.

The 275-kilowatt AWT-26 is a very different machine from U.S. Windpower’s 33M-VS. It is a downwind, passiveyaw machine with a two-bladed, stallregulated “teetered” rotor. Its turbine points away from the wind, and the machine aims itself, much as a weather vane does. Two-bladed rotors are more difficult to design than three-bladed ones, but because blades are costly, a twin-blade system is often more economical. In addition, the blades are not rigidly fixed to the hub but are allowed to pivot, or teeter, a few degrees to either side. That’s because wind speeds are higher farther above the ground. The pivoting system allow-s the rotor to equalize the wind forces and decrease thrust briefly without passing it through to the drive shaft.

A prototype of the AWT-26 has been running in California since early this spring. Another will be built by the end of this year. Although about two years behind the 33M-VS in development, the AWT-26 may be able to give U.S. Windpower a run for the lead in the domestic wind market. Its design is simpler, which should result in lower production costs and easier maintenance. It weighs half what most three-blade models do, yet is better engineered than the lightweight machines of a decade ago that came to grief. And the new airfoils may allow the AWT-26 to capture as much energy as, if not more than, U.S. Windpower’s pitch-controlled turbine— without the complex pitch apparatus.

The Conservation and Renewable Energy System, a newly formed public-utility consortium in Washington state, is negotiating a contract with the Bonneville Power Administration for the installation of a wind farm near Goldendale, Washington. The wind farm will generate twenty-five megawatts of power with AWT-26s that were bid at $.056 per kilowatt hour. Bonneville is giving a similar boost to a proposed wind farm in Carbon County, Wyoming, which will use U.S. Windpower’s 33M-VS.

Part of the financing for the AWT-26’s design came from a $7 million NREL program aimed at using the best current technology to create reliable utilitygrade turbines intended to be commercially available by mid-decade. But encouraging utilities to use wind involves as much education as engineering. Only a handful of utilities outside California have any experience with wind energy; even in California the experience is indirect, since wind companies like U.S. Windpower run the wind farms, not the utilities themselves. State utility commissions are also ignorant about wind, and are apt to view it as a risky experimental technology.

NEW MACHINES and technical developments like the new airfoil have given the U.S. wind industry the potential to develop a global market for its products. China is seen as a huge market; so are India and Eastern Europe. But the United States will have stiff competition from Western Europe, which is aggressively pursuing wind energy in order to cut acid rain, decrease its reliance on nuclear energy, and launch a new domestic industry that can then expand worldwide. Last year the United States, on the strength of the three California wind farms, far outstripped Europe in installed capacity—1,600 megawatts to 750. But by the year 2000 Europe may have 4,000 megawatts of installed wind capacity, half again what the United States is likely to have. The Germans, for instance, have agreed to install 250 megawatts of wind turbines.

U.S. efforts seem rather feeble by comparison. “Our budget was cut about ninety percent during the 1980s,” Jim Tangler says. “We were zeroed out several times tinder Reagan, but a little bit always got put back in.”At present the Department of Energy devotes about $24 million of its $257 million renewable-energy budget to wind, spending most of it at NREL and the rest at Sandia National Laboratory, in New Mexico, and the Pacific Northwest Laboratory, in Washington. Not everyone is happy with the amount wind is getting. “The U.S. is nickel-and-diming research in this area,” says Robert Lynette. “We had seventy million dollars a year tor research during the Carter years. And what is it now? We could accelerate this technology so much faster, and attract some new players to it as well.”

Lynette sees a solution: draw the aerospace industry into wind energy. Wind and aerospace seem a natural pairing. Aerodynamics, structural dynamics, advanced electronics—everything turbine makers hope to focus on in coming generations of machines— are everyday problems for Boeing and McDonnell-Douglas. Such companies could also bring sophisticated manufacturing techniques to what is today a craft industry. “These blades are essentially boat technology,” an NREL engineer, Walt Musial, told me while we were touring the lab’s field site. His hand rested on a big fiberglass U.S. Windpower blade that the lab was stress-testing. “It takes a lot of people to just lay up layers of cloth and resin in the molds. We see this as an area where we can make big gains in cost, with more-advanced manufacturing techniques.” The blades for Lynette’s machine are wooden—for all practical purposes long pieces of cabinetwork, and also highly labor-intensive. But they’re lighter than equivalent fiberglass blades. Lighter still would be blades made from carbon fiber, a material aerospace companies are well acquainted with. “These guys are kind of shellshocked now,” Lynette says, alluding to aircraft makers’ travails with defense cutbacks and the chaos among their commercial customers. “But pretty soon they’re going to say, ‘We need products.’” If aerospace firms did become involved, this would encourage other large companies to support what might at first be limited production runs of wind turbines, and would give utilities the confidence that the manufacturer of their new turbines would be around to maintain them.

Will wind power catch on? Perhaps. Scattered wind projects in Minnesota, Wyoming, the Pacific Northwest, and New England are now in the planning stage—not enough to attract much additional interest. But the 1992 Energy Policy Act gives a 1.5 cent tax credit for each kilowatt hour of energy produced from wind (the previous federal and California credits applied only to equipment costs). When this provision of the Energy Policy Act takes effect, next year, a number of wind projects may follow. An even bigger boost may have come last April, when President Clinton vowed to cut greenhouse gases to 1990 levels by the year 2000. Wind may prove to be one of the most effective ways for utilities to meet power needs without burning coal or gas.

Wind energy is no longer a research project. It works, and works cheaply and reliably enough to compete with other energy sources. Still, it must overcome a somewhat shady past to sell balky utilities and the public on its advantages. Its long-elusive promise, though, may soon be fulfilled. “We don’t really need a big breakthrough,”says Edgar DeMeo, the head of EPRI’s solar-power program. “If wind just gets a chance in a few places, it will make its own case.”

—Douglas Gantenbein