Wind Turbine Technology in the Baltic Sea

Wind Machines the Envy of Leonardo

Could Today's Turbines Become Passé?

We all know it is critical for us to curb consumption of fossil fuels, not only because most of this "ancient sunlight" comes from unstable parts of the world (and will eventually run out), but also because it damages the future of the only planet we have.
     We need to substitute, where possible, biofuels, hydrogen or electricity to power our transportation, and we need to get as much electricity as possible from sources other than coal, and especially from renewable energy sources. Large renewable energy sources include hydroelectric, wind, solar, and geothermal. Most potential hydroelectric sources are already developed; of the other three renewables, wind power is (so far) more widely
deployed than the other two, despite their huge potential.
     Denmark, Germany and Spain, for example, produce large portions of their electricity from ground-based wind turbines. Even the United States has built a number of "wind farms", mostly in the Southwest and West. Engineers have evolved standard turbine designs that
call for up to 300 ft. diameter three-bladed propellers driving generators mounted on towers up to 300 feet tall. Groups of these devices are located in high wind areas and can generate enough electricity, enough of the time, to be competitive with coal-fired generating plants at less than 10 cents per kilowatt-hour. But these turbines are expensive to build and controversial with local residents despite that they are, at least to some, quite beautiful. An important weakness is that they don't work when the wind is too light, or when it is too strong. Winds Aloft Are More Reliable Aviators and meteorologists know that "winds aloft" are much stronger than surface winds, as well as much steadier, and are therefore a tempting source of power. Between Latitudes 30 degrees North and 50 degrees North, and above 3000 feet, the wind is several times stronger than on the ground. Ground-based turbines obviously cannot reach these winds, but some entrepreneurs and engineers in the US and Italy are developing ingenious new ways to use this higher altitude wind for power, and the costs appear to be extremely promising. In fact, these new designs may be able to deliver electricity at 1-2 cents per kilowatt-hour, a fraction of ground-based wind turbine costs, and highly competitive with any other source of power. But How to Reach Those Winds Aloft? Inventors have been thinking about this question for years, and have developed various designs for capturing the wind energy available above the ground. One such design looks like a twin rotor helicopter that hovers in auto-rotation on a tether while the rotors run generators aboard and the power runs down a wire incorporated in the tether. This method has been shown to work, but is complex, expensive and conjures up images of helicopters crashing and causing damage.
     People have experimented with kites reeling out from spools which run generators on the ground; the same spool then reels the kite back in at a lower altitude, consuming much less power than was generated during the "outstroke". This approach also works; it requires multiple kites flying at the same time to produce a net positive output, and it is complex to design, build and operate.
Enter a Technology Transfer of a Different Sort A sport called kite-boarding has evolved from hang-gliding and wind-surfing. It allows a sailor on a "short-board" with foot straps to control very accurately a semi-circular, semi-rigid fabric kite above his head that tows him around at high speeds on the surface of the water in reasonable safety. It is much more fun than water skiing, especially since it does not require a powerful speedboat. The key to the sport's growth beyond slightly crazed risk-takers to more ordinary athletes is the development of reliable controls for "powering up", steering and "de-powering" the kite at will.
     These are recent developments and potentially important ones for wind-generated electricity.
     Environmentally-aware kite boarders began to see that their highly developed kites generate a lot of controllable power and might be used for other purposes, such as generating electricity. A group of such people has started a company in Alameda, CA, called Makani Power, which can be visited at www.makanipower.com (makani = "wind" in Hawaiian). They are being stealthy about publicizing their approach, but a little information about them can be gleaned from public sources.
Enter Google…Stage Left Google apparently learned of this company and has funded it to the tune of ten million dollars. Given Google's spectacular profitability, its brand acceptance and its "socially conscious" corporate culture, it is hard to imagine a better investor for Makani to have. Google is very conscious of the energy consumption of its uniquely large server farms; this is widely regarded as the reason for their locating an enormous data storage facility in The Dalles, OR, where hydropower and water-cooling are cheap and plentiful.
     Most intriguing is how Makani plan to convert the power available from kites into meaningful amounts of usable power on the ground. In one variation they intend to build large individual kites fitted with a combination motor/generator. The motor is used for vertical take-off and to gain enough altitude for the wind to take over, whereupon the motor becomes a generator sending power down the tether to the ground. Through the control lines, the kite is made to describe high speed "figure eights" in the sky, greatly accelerating the relative wind over the generator/propeller, and increasing the power generated by the square of the increase in apparent wind speed.
     We looked into another design idea from Italy that makes good sense to us. This involves building a large diameter "carousel-like" horizontal wheel that would rotate slowly in one direction and be connected through gearing to generators. The wheel would be driven by standard semi-rigid fabric kites attached at various points around the periphery of the carousel. Each kite would be automatically powered up on one side of the wheel and de-powered on the other side, using standard control lines connected to a straightforward mechanical control system.
     It would be the same principle as an anemometer, writ large. It would overcome the need to transmit power along what is essentially a kite string that might be over 3000 feet long.
     Preliminary analyses indicate that these designs could generate a great deal of power (ca. 1 to 100 megawatts per installation) in a relatively small space at reasonable cost. In fact, one engineer calculated that the airspace that must be restricted (for safety reasons) near a nuclear power plant, could, if fitted with these sorts of wind generators, produce roughly the same amount of power as the nuclear plant itself would produce!
     Of course, many issues need to be resolved and many unknowns explored before this dream becomes a reality. But it is heartening to learn just how many original ideas are sparked by the increasing attention this subject is getting as appreciation of the gravity of the problem grows.
      - Douglas Ayer

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The 1% Solution:

Wind Power: Increasingly Viewed as "The Most Cost-Effective and Scalable" Renewable

March 10, 2009
The wind-power industry presently generates about 1% of all electricity worldwide. The wind turbines now in use have a typical capacity of around 1.5 to 2.5 megawatts, have rotor diameters as broad as 100 meters (see photo), and rotate around an area roughly the size of a football field.
     Public opinion is divided about these devices. Many feel that they are majestic symbols of new energy sources; others reject them as an eyesore—a distraction from the beautiful landscape.
     In theory, wind is so readily available throughout the world that it could meet the world’s current energy needs. Stanford University energy researchers recently found that global wind energy potential in 2000 was about 72,000 GW—almost five times world demand. Furthermore, wind technology is steadily getting less costly—from around 30 cents per kilowatt hour in the early ‘80’s to around ten cents in 2007. Tax credits and feed-in tariffs have made wind power as cost-efficient as gas and coal-generated electricity in many energy markets. Maria Sicilia of the International Energy Agency says that energy produced from wind could compete with gas and coal in most markets, even barring subsidies.
     The European Union set a goal of getting 20% of its energy from wind and other renewable sources by 2020. America’s Department of Energy wants US wind-power to reach 20% by 2030—a far less significant goal for a country of this size. Asia’s ambitions are more grandiose than either, and it may become the world’s biggest user of wind power in the next five years.
     Wind-power technology is growing and expanding at a brisk rate, but there are problems ahead. Cities are generally not near the areas where the wind blows, which means that the electricity the cities require will have to travel to them across new transmission lines that must be planned, constructed, and integrated into the existing power grid. The program is also largely dependent on subsidies, which governments could cut off at any time, depending on their priorities. Imposing prices on carbon emissions would go a long way to eliminate this problem by funding wind and other renewable with the revenue.
     Another concern for wind-power planners and advocates is that many people need to be convinced that the noise of wind farms erected close by will be tolerable.

They are much larger than you thought. Photo shows a single blade undergoing manufacture at a Vestas plant. A Danish company, Vestas is the world's largest producer of wind machines.

     A third problem is that wind power is not always available as needed. Operators of the power grids need to make certain that alternative power is available when the wind doesn’t blow. But according to the US department of Energy’s wind advisory group, the power reserves needed for support of wind-power that represents 20% of the total power grid are actually minimal—only a small percentage of total installed wind machine capacity.
A Short History of Wind Power      Countries began looking for alternate sources beyond fossil fuels following the first oil crisis in 1973. One of the countries most deeply affected was Denmark, which was almost entirely dependent on foreign oil sources. Wind, however, is in particular abundance there, so the country began an intensive research project on wind power to markedly reduce that dependence.
     America followed suit, with funds from the government, and Boeing and NASA began creating huge, multi-megawatt wind turbines, but many of these machines were expensive to run and maintain. Entrepreneurs got into the act, although their machines were smaller and came in a wide variety. There were models with two-bladed rotors on a horizontal axis, as well as vertical axis machines. Denmark experimented with similar designs.
     By the early ‘80’s, however, one design was emerging as the standard: the three-bladed wind turbine, operating on a horizontal axis. The two-blade designs were ultimately rejected because they were not as dynamically balanced as were the three-blade rotors, they were harder to design, and spun faster, which created more noise. The three-blade turbines were also more aesthetically pleasing to the eye.
     Since the American machines were designed to “bend with the wind”, they were of a softer design, and did not hold structure under heavy loads. The Danish machines were rigid, and much heavier structures, that weighed almost twice as much as the American machines.
     Nevertheless, with the technology still in its infancy, in the early 1980’s California gradually installed over 1.2 GW of wind power, which was at the time nearly 90% of the total wind power capacity globally, which some called the great “wind rush”. It was fueled by federal tax credits and substantial state incentives for wind power. Large wind machine arrays began to appear, which came to be known as “wind farms”. In the mid-1980’s, the credits expired, and with it, the immediate and near future of wind power in California. American companies tied to the technology went bankrupt, as did several in Denmark, which had been largely manufacturing and servicing the California effort. One significant result of this period, however, was the worldwide standardization on the Danish three-blade design.
     Gradually, the Danish engineers developed more efficient means to deal with the stretching, bending and vibration, to reduce weight, and thus optimize the devices. The Modern Wind Machine      These machines now achieve around 50% of the kinetic energy in the wind, with a theoretical limit of 59%. These achievements have come at a cost, however, in problems with the gearboxes, which endure considerable vibration and movement inside the turbines. A German firm, Enercon, has developed a direct-drive device with a low rotational-speed generator that does not require a gearbox. Unfortunately, these generators are generally heavier, and come at a higher cost, so there is some doubt as to the long-term viability of this approach.
     The very large machines of today with their long blades capture more energy from the wind, since the blades sweep over a much larger area, which allows the turbine to produce its rated power at lower wind speeds and at a higher percentage of the time. Other innovations are variable pitch, which allows the angle of the blades to the wind to be adjustable, so that the effect of the wind on the drive train and rotor can be minimized, and variable-speed, which enable the turbines to operate at higher efficiency over a wider range of wind speeds, thus converting more of the wind’s speed into electricity.
     As a matter of interest, the worldwide distribution of working wind power as of the end of 2007 is as follows:

Germany 23.7% Italy 2.9%
United States
18.0% Britain 2.6%
Spain 15.6% France 2.6%
India 8.3% Portugal 2.3%
China 6.3% Other countries combined 14.4%
Denmark 3.3%  

Bigger and More Powerful      In spite of the problems of shipping, installing, and maintaining very large wind-power machines, the industry is committed to the “bigger is better” approach. Machines onshore are moving up to a capacity of 3MW, and offshore devices up to 10MW. Offshore installations are 40% more expensive than their onshore counterparts—a good reason why there are far fewer of them at present. Nonetheless, many believe that the offshore potential is very promising, since carefully selected offshore sites usually offer higher and more consistent wind speeds. Moreover, many wind farms can be situated where they can be neither seen nor heard from land, which eliminates objections from many quarters. (This has been a particularly persistent issue in America, where locals have protested wind-farm installations planned for nearby areas). A Look to the Future      For now, at least, the most serious impediment to a more universal adaptation of wind power is the necessity of overhauling the existing power grid to accommodate it. Costly new transmission lines must be installed to transmit the power from rural, strong-wind areas to highly populated areas where the demand lies.
     At present, no one can tell if the DOE group’s stated goal of 20% will be reached any time in the near future, but wind power will surely play a significant part in America’s energy future. Almost 35% of new electricity-generating power came from American wind generation in 2007. By 2030 it is predicted that 14% of all electricity generated in the European Union will come from wind power.
     As Victor Abate, the vice-president of renewables for GE Energy has stated, “From a zero-fuel-cost, zero-carbon perspective, wind power is currently the most cost-effective and scalable technology available to mankind.”
     Wind power is here to stay. It remains to be seen to what extent governments and their supporters will see fit to make wise use of it.
     - John Burr

The Kite Runner:

A Cargo Ship Returns to the Era of Sail

In late January, a modern cargo ship "set sail" across the Atlantic transporting Danish wind turbine equipment for installation in the United States, appropriately using using wind and sail power of its own as a backup to its propulsion system. The 10,000 ton ship successfully completed a round trip between Germany and Venezuela saving 20 percent of the usual fuel use.
     A standard freighter in other respects, the 460-foot Beluga Skysails, owned by a shipping company based in Bremen, Germany, is fitted with a 3,000 square meter kite — the size of an American football field — that tows the ship to reduce its fuel costs and emissions by as much as 50% under ideal wind conditions.
     The kite flies high above the deck at altitudes between 100 and 500 meters (roughly 300 to 1600 feet), where winds are steadier than at sea level.
Compressed air continually alters the shape of the kite, an airfoil shaped something like a wing, by thinning and thickening its cross-sectional profile to maximally exploit the current wind. The kite is not hauled in during a storm. It stays aloft despite its unchangeable area, but it can be decompressed so as to minimize the pull of the strongest winds, according to its designers, Skysails of Hamburg.
     The sail is tethered to a “car” that serves to winch in and pay out the kite to desired altitudes. The car travels a track fore and aft along the hull (see illustration) to enable the ship to sail degrees of reach. Software then optimizes the ship’s route to take maximum advantage of wind direction.
     The world’s shipping fleet, including military, burns about 5.5 million barrels of oil daily (2 billion barrels annually) as reported in a 2003 University of Delaware study. With oil prices of $20-$30 a barrel likely to become historical artifacts as the price verges on $100/bbl, shipping companies the world over are expected to be watching this maiden voyage in prayerful anticipation.
     Cargo ships adopting auxiliary wind power offer a benefit beyond the usual swap of wind for oil. They use low-grade fuel oil that accounts for some 7% of worldwide sulphur dioxide output. As well, Skysails estimates that, were its technology adopted by the 40,000 ships capable of retrofit, 0.6% of global CO2 emissions would be eliminated.      - Stephen Wilson