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(Monet's "Zaan River at Zaandam," 1871)

Part 2 - 20th Century Developments



The most obvious influence on 20th century wind power was the increasing use of electricity. But this started with a look to the past.

First Use of Wind for "Large-Scale"  Generation of Electricity

The first use of a large windmill to generate electricity was a system built in Cleveland, Ohio, in 1888 by Charles F. Brush. The Brush machine (shown at right) was a postmill with a multiple-bladed "picket-fence" rotor 17 meters in diameter, featuring a large tail hinged to turn the rotor out of the wind. It was the first windmill to incorporate a step-up gearbox (with a ratio of 50:1) in order to turn a direct current generator at its required operational speed (in this case, 500 RPM.)

Despite its relative success in operating for 20 years, the Brush windmill demonstrated the limitations of the low-speed, high-solidity rotor for electricity production applications. The 12 kilowatts produced by its 17-meter rotor pales beside the 70-100 kilowatts produced by a comparably-sized, modern, lift-type rotor.

In 1891, the Dane Poul La Cour developed the first electrical output wind machine to incorporate the aerodynamic design principles (low-solidity, four-bladed rotors incorporating primitive airfoil shapes) used in the best European tower mills. The higher speed of the La Cour rotor made these mills quite practical for electricity generation. By the close of World War I, the use of 25 kilowatt electrical output machines had spread throughout Denmark, but cheaper and larger fossil-fuel steam plants soon put the operators of these mills out of business.

By 1920, the two dominant rotor configurations (fan-type and sail) had both been tried and found to be inadequate for generating appreciable amounts of electricity. The further development of wind generator electrical systems in the United States was inspired by the design of airplane propellers and (later) monoplane wings.


Figure 6. The Brush postmill in Cleveland, Ohio, 1888. The first use of a large windmill to generate electricity. Note the man mowing the lawn at lower right.

Charles F. Brush Special Collection, Case Western Reserve University, Cleveland, Ohio

 

Small System Pioneers

The first small electrical-output wind turbines simply used modified propellers to drive direct current generators. By the mid-1920's, 1 to 3-kilowatt wind generators developed by companies like Parris-Dunn and Jacobs Wind-electric found widespread use in the rural areas of the midwestern Great Plains. (A 3-kilowatt Jacobs unit is shown at right, being adjusted by a cigarette-puffing M.L. Jacobs at Rocky Flats, Colorado in 1977.) These systems were installed at first to provide lighting for farms and to charge batteries used to power crystal radio sets. But their use was extended to an entire array of direct-current motor-driven appliances, including refrigerators, freezers, washing machines, and power tools. But the more appliances were powered by the early wind generators, the more their intermittent operation became a problem.

The demise of these systems was hastened during the late 1930s and the 1940s by two factors: the demand of farmsteads for ever larger amounts of power on demand, and the Great Depression, which spurred the U.S. federal government to stimulate the depressed rural economies by extending the electrical grid throughout those areas.

A lot is made of this development and how horrible it was for the government to intervene. (At this point in most wind energy documentaries, there's a plaintive whine of a harmonica and a shot of a rusting wind turbine hulk.) But I doubt the farmers who were helped by the new electrical grids would share this feeling. And the growing demand for electrical power created by the wind generator, combined with the inability of the technology to adapt, helped make the situation inevitable. The early success of the Midwest wind turbines actually set the stage for the possibility of more extensive wind energy development in the future.

While the market for new small wind machines of any type had been largely eroded in the United States by 1950, the use of mechanical and electrical system continued throughout Europe and in windy, arid climates such as those found in parts of Africa and Australia.


Figure 7. M.L. Jacobs adjusting the spring-actuated pitch change mechanism on a Jacobs Wind-electric in 1977.

"Bulk" Power from Wind

The development of bulk-power, utility-scale wind energy conversion systems was first undertaken in Russia in 1931 with the 100kW Balaclava wind generator. This machine operated for about two years on the shore of the Caspian Sea, generating 200,000 kWh of electricity. Subsequent experimental wind plants in the United States, Denmark, France, Germany, and Great Britain during the period 1935-1970 showed that large-scale wind turbines would work, but failed to result in a practical large electrical wind turbine.

The largest was the 1.25 megawatt Smith-Putnam machine (Figure 8, at right), installed in Vermont in 1941. This horizontal-axis design featured a two-bladed, 175-foot diameter rotor oriented down-wind of the tower. The 16-ton stainless steel rotor used full-span blade pitch control to maintain operation at 28 RPM. In 1945, after only several hundred hours of intermittent operation, one of the blades broke off near the hub, apparently as a result of metal fatigue. This is not surprising considering the huge loads that must have been generated in a structure that had a lot in common with a gigantic rotating erector set.


Figure 8. Palmer Putnam's 1.25-megawatt wind turbine was one of the engineering marvels of the late 1930's, but the jump in scale was too great for available materials.

European Development

European developments continued after World War II, when temporary shortages of fossil fuels led to higher energy costs. As in the United States, the primary application for these systems was interconnection to the electric power grid.

In Denmark, the 200 kW Gedser Mill wind turbine operated successfully until the early 1960s, when declining fossil-fuel prices once again made wind energy made uncompetitive with steam-powered generating plants. This machine featured a three-bladed upwind rotor with fixed pitch blades that used mechanical windmill technology augmented with an airframe support structure. The design was much less mechanically complex than the Smith-Putnam design. In fact, it was not that far removed from Poul La Cour's 1920-era windmill (a fact that worked to its advantage.)

Figure 9. Yes, that's an airframe holding together the three blades of the "Gedser Mollen." Fiberglass later eliminated this design requirement.

In Germany, Professor Ulrich Hutter developed a series of advanced, horizontal-axis designs of intermediate size that utilized modern, airfoil-type fiberglass and plastic blades with variable pitch to provide light weight and high efficiencies. This design approach sought to reduce bearing and structural failures by "shedding" aerodynamic loads, rather than "withstanding" them as did the Danish approach. One of the most innovative load-shedding design features was the use of a bearing at the rotor hub that allowed the rotor to "teeter" in response to wind gusts and vertical wind shear. Hutter's advanced designs achieved over 4000 hours of operation before the experiments were ended in 1968.

Post war activity in Denmark and Germany largely dictated the two major horizontal-axis design approaches that would emerge when attention returned to wind turbine development in the early 1970s. The Danes refined the simple, fixed pitch, Gedser Mill design, utilizing advanced materials, improved aerodynamic design, and aerodynamic controls to reduce some of its shortcomings. The engineering innovations of the light-weight, higher efficiency German machines, such as a teeter hinge at the rotor hub, were used later by U.S. designers.

The development of modern vertical-axis rotors was begun in France by G.J.M. Darrieus in the 1920s. Of the several rotors Darrieus designed, the most important one is a rotor comprising slender, curved, airfoil-section blades attached at the top and bottom of a rotating vertical tube. Major development work on this concept did not begin until the concept was reinvented in the late 1960s by two Canadian researchers.

U.S. efforts with the Darrieus concept at Sandia National Laboratories began after the 1973 oil embargo, with the entry of the U.S. Federal Wind Energy Program into the cycle of wind energy development.

NEXT: Making Wind A Federal Case

Figure 10. Hutter's wind turbines, like other German devices of the mid-20th century, were advanced for their time.


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