Farm windmills restored by J.B. Buchanan on Hwy 270 between Stinnett and Spearman, TX.
The second one from the left is used for the house.
|1.4||Generation of Electricity for Utilities|
Industrialized societies run on energy. Economists look at monetary values (dollars) to explain the manufacture and exchange of goods and services. However, in the final analysis, the physical commodity is the transfer of energy units. While industrialized nations comprise only one-fourth of the population of the world, they use four-fifths of the world's energy. Most of these forms of energy are solar energy, which are subdivided into the two classifications.
Other forms of energy are tides (due to gravitation), geothermal (heat from the earth) and nuclear (fission and fusion).
The main source of energy in industrialized nations is fossil fuels and when that factor is combined with the increasing demand and increasing population of the world, a switch to other energy sources is imminent. Whether this will be rational or catastrophic depends on the enlightenment of the public and their leaders.
The use of wind as an energy source begins in antiquity. At one time wind was a major source of energy for transportation (sailing), for grinding grain and for pumping water. Except for pleasure sailing, the main long term use of wind has been for pumping water.
The Dutch windmills for pumping large volumes of water from a low head are a famous attraction (Figs. 1.1-3). Windmills of the same type were also used for grinding grain (Fig. 1.2) and even for sawing wood. These machines were as large as 25 m in diameter and were almost all of wood. They were quite sophisticated in terms of the aerodynamics of the rotor and blades. Another famous example is the sailwing turbines for pumping water for irrigation on the island of Crete.
Figure 1.1 Dutch windmills for pumping water.
Figure 1.2 Dutch post mill.
Figure 1.3 Dutch windmill, high volume, low lift.
Farm windmills were one of the primary factors in the settlement of the great plains of the United States . Beginning in the mid 19th century, water pumping windmills were manufactured in the tens of thousands. These early wood machines (see Chapter photo) have largely disappeared from the landscape, except for an isolated farm house or in museums.
By 1900, almost all windmills were made of metal, still with multiblade vanes, and the fan or blades were 12-16 ft in diameter (Fig. 1.4). Although the peak use of farm windmills was in the 30's and 40's when over 6 million were in operation, these windmills are still being manufactured and are being used to pump water for livestock and residences. The American Wind Power Center in Lubbock, TX has an outstanding collection of farm windmills.
The farm windmill proves that wind power is a valuable commodity. For example, there are an estimated 30,000 operating farm windmills in the Southern High Plains of the United States. Even though the power output is low, 0.2 to 0.5 kilowatt (kW), they collectively provide an estimated output of 6 million watts or 6 megawatts (MW). If these windmills for pumping water were converted to electricity from the grid, it would require around 15 megawatts of thermal power at the generating station and over one billion dollars (1990 dollars) for the transmission lines, electric pumps, etc. This does not count the dollars saved by not using fossil fuel with an energy equivalent of 130 million kilowatt hours (kWh) per year (equivalent to 80,000 barrels of oil per year). However, because many of these windmills are 30 years or older and maintenance costs are $200 to $300 per year, farmers and ranchers are looking at alternatives such as solar water pumping rather than purchasing new farm windmills.
Figure 1.4. Farm windmill for pumping water for livestock and Residences.
As electricity became practical, isolated locations were too far from generating plants and transmission lines were too costly. Therefore, a number of manufacturers built stand alone wind systems for generating electricity (Figs. 1.5, 1.6). Most of these systems had a direct current generator, 6 to 32 volts, and stored the electricity in batteries. Some of the later models were 110 volts.
These systems are quite different from the farm windmill in that two or three propeller blades are used. The farm windmill is too inefficient for generating electricity, although it is well engineered for pumping low volumes of water.
The wind chargers became obsolete in the United States when inexpensive electricity (subsidized) became available from rural electric cooperatives in the 40's and 50's. After the energy crisis of 1973, a number of these units were repaired for personal use or to sell. Small companies also imported wind machines from Australia and Europe to sell in the United States during the 70's.
Figure 1.5. Wincharger, small DC system (100 W) with air brakes.
Figure 1.6. Jacobs wind turbine, DC generator, 4 kW, blade pitch for overspeed control.
Located on Joe Spinhirne farm near Vega, TX.
There were a number of attempts to design and construct large wind turbines for utility use [3-8]. These designs centered on four different concepts for capturing wind energy (Fig. 1.7): Magnus Effect, Savonius, and airfoil shaped blades with the axis of the rotor being horizontal or vertical.
Figure 1.7 Examples of rotors for wind turbines.
A rotating cylinder in an airstream will experience a force or thrust perpendicular to the wind, the Magnus Effect. In 1926 Flettner built a horizontal axis wind turbine with four blades where each blade was a tapered cylinder driven by an electric motor. The cylinders (blades) were 5 m long and 0.8 m in diameter at the midpoint. The rotor was 20 m in diameter on a 33 m tower. Rated power was 30 kW at a wind speed of 10 meters/second (m/s).
Madaras proposed mounting rotating cylinders (vertical) on railroad cars which would go around a circular track propelled by the Magnus Effect. The generators would be connected to the axles of the railroad cars. In 1933, a prototype installation, which consisted of a cylinder 29 m tall and 8.5 m in diameter mounted on a concrete base, was spun when the wind was blowing to measure the force. Results were inconclusive and the prospect was abandoned.
The Magnus Effect has been used for ships, called Flettner rotors, [9, 10] and one ship operated using rotors for fuel saving from 1926 to 1933. In 1984 the Cousteau Society had a sailing ship, Alcyone, built which used two fixed cylinders with an aspirated, turbosail .
In Finland, Savonius built 'S' shaped rotors which were similar to two halves of a cylinder separated by a distance smaller than the diameter. With a vertical axis there are no orientation problems due to different wind directions.
In 1927, Darrieus invented a wind machine where the shape of the blade was similar to a jumping rope. His patent also covered straight vertical blades, a giromill. Later the Darrieus design was invented again by researchers in Canada.
In 1931 the Russians built a 100 kW wind turbine (Fig. 1.8) near Yalta on the Black Sea. The rotor was 30 m in diameter on a 30 m rotating tower. The rotor was kept facing into the wind by moving the inclined supporting strut which was on a carriage on a circular track. The blade covering was galvanized steel and the gears were of wood. Rotational speed and power were controlled by the adjustable pitch of the blades.
Figure 1.8 Russian wind turbine. 100 kW.
The Smith-Putnam wind turbine (Fig. 1.9) was developed, fabricated and erected in two years, 1939-1941 . The turbine, which was located on Grandpa's Knob, Vermont, was connected to the grid of Central Vermont Public Service. The rotor was 53 m in diameter on a 38 m tower. Blades were stainless steel with a 3.4 m chord and each weighed 8,700 kg. The generator was synchronized with the line frequency by adjusting the pitch of the blades. At windspeeds above 35 m/s the blades were changed to the feathered position to shut the unit down. Rated power output was 1,250 kW at 14 m/s. The rotor was on the downwind side of the tower and the blades were free to move independently (teeter; perpendicular to the wind) due to wind loading.
Figure 1.9 Smith Putnam, 1,250 kW.
Testing started in October, 1941 and in May, 1942, after 360 hours of operation, cracks were discovered in the blades near the root. The root sections were strengthened and further cracks were repaired by arc welding. A main bearing failed in February 1943 and it was not replaced until March, 1945 because of a shortage of materials due to the war. After the bearing was replaced, the unit was operated as a generating station for three weeks when a blade failed due to stress at the root. Total running time was around 1,100 hours. Even though the prototype project was considered successful, it was not further pursued because of economics.
Percy Thomas, an engineer with the Federal Power Commission, pursued the feasibility of wind machines. He compiled the first map (Fig. 1.10) for wind power in the United States and published reports on design and feasibility of wind turbines .
Figure 1.10 Early wind map for the United States
After World War II research and development efforts on wind turbines were centered in Europe. E. W. Golding summarized the efforts in Great Britain  and further efforts are reported in the conference proceedings of the United Nations .
The British built two large wind turbines. One was built by Enfield, based on a design by the Frenchman, Andreau, and was erected at St. Albans in 1952. The other was built by John Brown on Costa Hill, Orkney in 1955. The John Brown unit (Fig. 1.11) was rated at 100 kW at 16 m/s. Rotor diameter was 15 m on a 24 m tower. The unit only ran intermittently in 1955.
Figure 1.11 John Brown wind turbine, 100 kW, on Island of Orkney.
The Enfield-Andreau wind turbine rotor was 24 m in diameter on a 30 m tower (Fig. 1.12), with a rated power of 100 kW at 13 m/s. This unit was quite different in that the blades were hollow and when they rotated the air flowed through the generator at ground level and out of the tip of the blades. This unit was moved to Grand Vent, Algeria, for further testing in 1957. Frictional losses were too large for this unit to be successful.
The French also built several prototype wind turbines from 1958 to 1966. These included the 130 kW Neyrpic machine (Fig. 1.13), which had a rotor diameter of 21 m on a 17 m tower; a 800 kW wind turbine (Fig. 1.14) located at Nogent Le Roi, which had a rotor diameter of 31 m on a 32 m tower; and another unit located at St. Remy-Des-Landes with a rated power of 1000 kW at 17 m/s.
Dr. Hutter of Germany designed wind turbines with lightweight fiberglass blades (Fig. 1.15). The larger unit had a rotor 35 m in diameter and produced 100 kW at 8 m/s . This machine ran for one year 1957-1958.
Figure 1.12 Enfield-Andreau wind turbine, 100 kW.
Figure 1.13 Neyrpic wind turbine, 120 kW.
Figure 1.14 Nogent Le Roi wind turbine 800 kW.
Figure 1.15 German wind turbines: left 100 kW, right 10 kW.
Since the Danes did not have any fossil fuel resources, they looked at connecting wind turbines into their national grid. The Danes had the only successful program. It began in 1947 with a series of investigations on the feasibility of using wind power and continued until 1968 [6, pp. 229-240]. A prototype wind turbine of 7.5 m diameter was built and remained in operation until 1960, when it was dismantled. A wind turbine at Bogo (Fig. 1.16), originally constructed for direct current (DC) power in 1942 was reconstructed for alternating current (AC) in 1952. Rotor diameter was 13.5 m with a 45 kW generator. The results of the two experimental wind turbines were encouraging and culminated in the 200 kW Gedser wind turbine (Fig. 1.16). This unit was erected in 1957 and was on line until 1968 when maintenance costs became too high. The rotor was 35 m in diameter on a pre-stressed concrete tower 26 m high. Blades were fixed pitch with tip brakes for overspeed control. In 1976 the ERDA (US) and DEFU (Denmark) furnished money to place the Gedser wind turbine in operation for a short time period.
The successful program of the Danes was overshadowed by the failure of other large machines. The machines failed due to technical problems, mainly stresses due to vibration and control at high wind speeds. Others were economic failures. Everyone agreed there were no scientific barriers to the use of wind turbines tied to the utility grid.
In the 60's development of wind machines was abandoned since petroleum was easily available and inexpensive.
Figure 1.16 Danish wind turbines: left, 45 kW at Bogo, right, 200 kW Gedser.