Nanotechnology

A wind turbine for the home

Good news for homeowners: with small wind turbines, you will soon be able to generate your own electric power right out in the backyard. The manufacturers produce the rotor blades using nanoparticles from Bayer MaterialScience.

If you have room in your backyard for a cherry or apple tree, you will soon be able to generate power there too. Just install a wind turbine from Eagle Tuulivoima, hook it up to the power grid and you’re good to go.

The Finnish company has just begun producing small wind turbines. “We’re starting off with two models: one with a rated output of two kilowatts and one with five kilowatts,” says company founder Juha Siitonen. The product range is to be expan-ded next year to include 10 and 20 kilowatt models. To compare, large systems generate over 1,000 kilowatts, “but ours are big enough for home use.”

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Lightweight: Eagle employee Mika Vanhatalo manufacturing a rotor blade reinforced with carbon nanotubes.

Oddly enough, the idea of build-ing wind turbines for the home originated in Lahti, an inland ci-
ty in Finland where only a light breeze usually blows. But it’s also home to Amroy, a company with very special expertise: it incorporates carbon nanotubes (CNT) into plastic resin by a unique method, resulting in a material with significantly improved mechanical properties.

Hybtonite is the name of the reinforced epoxy resin. If it sounds familiar, that’s because it’s a deliberate allusion to the legendary kryptonite of Superman fame.

The material’s unusually high strength is attributable to Baytubes brand carbon nanotubes supplied by Bayer MaterialScience. Hybtonite has already demonstrated its toughness in other fields of application. For example, the material is used to produce ice hockey sticks and skis. A Bayer MaterialScience customer in China manufactures rotor blades between 40 and 50 meters long from Hybtonite for large wind power plants. So why not use the same material to make small wind turbines?

One day, Amroy employee Kimmo Kaila discussed this idea with his friends Miamari and Juha Siitonen in Lahti, and they were immediately taken with it. So much so that they quit their jobs and founded their own company in 2007: Eagle Tuulivoima. Tuulivoima is the Finnish word for wind power.

The Siitonens soon learned, however, that you need more than just the right material to make lightweight rotor blades. The generators that convert the rotation into electrical energy proved to be something of a problem. “Conventional devices need about 260 rotations per minute to generate electric power,” explains Miamari Siitonen. In other words, to produce electricity, they need a wind speed of 7 (51-60 km/h) or more.

Because weather conditions of this kind are not a daily occurrence, the Finns devised their own solution. The company had an innovative generator engineered that operates efficiently at wind s d thus meets one of the key requirements for mass production.

Vision of the future of Carbon Nanotubes: Carbon Nanotubes enable materials to achieve greater strength, and more: plastics become conductive, and the thermal conductivity of metals is improved.

The smallest system is the two kilowatt turbine. Its rotor blades weigh only 4.5 kilograms, even though they are 2.5 meters long. If they were made of glass fiber reinforced plastic, they would weigh twice as much. These blades would also have a much smaller surface area in contact with the wind. This means that the blades on the new system produce a higher wind yield. As a result, they are much more efficient.

If you have bigger and lighter rotor blades, the first question probably has to be whether they will break more easily in high winds. The answer in this case is no, thanks to the tiny carbon nanotubes incorporated into the plastic compound by supplier Amroy. These little CNTs enable the material to bear high mechanical stresses. “They also prevent material fatigue and ensure a long service life,” emphasizes Amroy CEO Antti Valtakari. This effect stems from both the elongated shape of the carbon structures and the fact that the company chemically anchors them in the plastic. What’s more, it takes the addition of just one percent of CNTs by weight to achieve this performance.

For individual homeowners, this method of alternative power generation naturally is only an attractive option if the price is right. It is expected to cost less than EUR 10,000 for a two kilowatt wind turbine including installation. The system can generate approximately 4,000 to 8,000 kilowatt hours of electric power annually, although the figure varies from region to region. Miamari Siitonen has calculated that a wind turbine this size can provide a single-family home with average consumption with all the electricity it needs. If the turbine produces surplus energy, it can be fed into the public grid, as is commonly done with solar power. Alternatively, the surplus can be stored.

In targeting customers, the Finns have their eye on more than just environmentally conscious homeowners in the industrial nations. “We are mainly focusing on regions accustomed to a very unreliable power supply, such as India or countries in Africa,” Siitonen says. If all goes well, the company may one day be as well known as a certain Finnish mobile communications corporation.

Small particles, big effect
In a computer model, carbon nanotubes (CNT) look like meshed, hollow, very thin straws. They have an unbelievably small diameter of just 15 nanometers, making them 5,000 times thinner than a human hair.

In contrast, a CNT particle can reach one micrometer in length, or one thousandth of a millimeter. To make these dimensions easier to visualize: if you lined up one gram of these CNT particles end to end, they would wrap around the earth one hundred times. Carbon nanotubes are four times lighter than steel, but their mechanical strength is five times greater. They also lend plastics yet another unusual property: they make the material electrically and thermally conductive.

Bayer MaterialScience is currently building the world’s largest pilot production facility for carbon nanotubes at its Leverkusen site, capable of turning out 200 tons per year. CNTs (brand name: Baytubes) already are used to mechanically strengthen skis, hockey sticks and surfboards.