From The Economist:
An innovative approach to making electricity from the wind
Fly a kite that powers a generator
Excerpts:
An innovative approach to making electricity from the wind
Fly a kite that powers a generator
Excerpts:
The wind blows more strongly at higher altitudes. That is why wind turbines have grown ever taller. The blade tips of today’s biggest now reach up a dizzying 260 metres, the height of the Transamerica building in San Francisco. Many dream of capturing stronger winds even higher up than that, but building taller turbine masts and constructing blades able to withstand the terrifying stresses involved in high-altitude wind gathering are costly. A number of firms are therefore developing a different and, they hope, ultimately cheaper approach to generating electricity at great heights. Their idea is to skip the mast altogether. Instead they propose to fly kites.
[...]
The SkySails Power system, as it is called, goes on sale next year. A single unit will produce 200 kilowatts—enough to run about 100 homes. It will, Mr Wrage says, cost about €300,000 ($340,000). At $1,700 a kilowatt, that is half the cost of a conventional turbine of equivalent capacity, and is comparable with the cost per kilowatt of industrial-scale turbines that have outputs measured in megawatts. Nor is SkySails alone in designing a system that works with a simple, wind-launched kite of this type. Kitepower, a competitor in the Netherlands, has come up with a similar arrangement, albeit somewhat smaller, which it, too, expects to be on sale next year. Other firms, however, are working on kites that are launched actively from the ground, rather than relying on winds near the surface for their initial lift.
[...]
Whether power-generation from high-altitude winds actually can compete with existing turbines remains to be seen. The potential is certainly there. Airborne Wind Europe, an industry group based in Brussels, calculates that the wind blows fast enough at heights of around 500 metres for this form of energy production to work almost anywhere in Europe. Lower down, however, the strongest winds are often found in coastal areas. These are places where population densities are frequently high and land for onshore wind farms is thus expensive, while building those farms offshore increases the awkwardness of construction and maintenance.
The mechanics of kite-flying, however, are more stressful than those of a wind turbine revolving smoothly and regularly. Flying tight figures-of-eight in gusty winds while pulling on a tether requires a robustness of structure and a precision of control that go beyond those involved in conventional aeronautics. And if, despite all precautions, a tether were to snap, measures would need to be in place to bring both it and the kite once attached to it safely back to earth. Moreover, air-traffic-control authorities will doubtless have something to say if their airspace seems likely to be invaded by fleets of giant kites.
[...]
[...]
The SkySails Power system, as it is called, goes on sale next year. A single unit will produce 200 kilowatts—enough to run about 100 homes. It will, Mr Wrage says, cost about €300,000 ($340,000). At $1,700 a kilowatt, that is half the cost of a conventional turbine of equivalent capacity, and is comparable with the cost per kilowatt of industrial-scale turbines that have outputs measured in megawatts. Nor is SkySails alone in designing a system that works with a simple, wind-launched kite of this type. Kitepower, a competitor in the Netherlands, has come up with a similar arrangement, albeit somewhat smaller, which it, too, expects to be on sale next year. Other firms, however, are working on kites that are launched actively from the ground, rather than relying on winds near the surface for their initial lift.
[...]
Whether power-generation from high-altitude winds actually can compete with existing turbines remains to be seen. The potential is certainly there. Airborne Wind Europe, an industry group based in Brussels, calculates that the wind blows fast enough at heights of around 500 metres for this form of energy production to work almost anywhere in Europe. Lower down, however, the strongest winds are often found in coastal areas. These are places where population densities are frequently high and land for onshore wind farms is thus expensive, while building those farms offshore increases the awkwardness of construction and maintenance.
The mechanics of kite-flying, however, are more stressful than those of a wind turbine revolving smoothly and regularly. Flying tight figures-of-eight in gusty winds while pulling on a tether requires a robustness of structure and a precision of control that go beyond those involved in conventional aeronautics. And if, despite all precautions, a tether were to snap, measures would need to be in place to bring both it and the kite once attached to it safely back to earth. Moreover, air-traffic-control authorities will doubtless have something to say if their airspace seems likely to be invaded by fleets of giant kites.
[...]
