Superconductors in Wind Turbines

Currently wind energy is one of the most booming renewable energy sources in America. From the year 2000 to 2008 wind energy consumption has gone from 57 trillion BTU to 514 trillion BTU [1]. Although this is still a very small portion of the 100 quadrillion BTU consumed every year in America, that is almost a tenfold increase in only eight years and more and more wind turbines are being installed every day.

One of the major factors that is limiting wind energy’s potential of becoming a major player in the U.S. energy sector is the cost, efficiency, and size constraints of large capacity wind turbines. Currently, the largest wind turbines being produced have reached a barrier at 5-6 MW due to the sheer size and weight of the conventional turbines that use copper winding construction [2].

6 MW Conventional Wind Turbine

(Source)

The solution to break through the 5-6 MW barrier is high temperature superconductors. High temperature superconductors (HTS) are a special class of materials that have essentially no electrical resistance at relatively high temperatures (-197 °C or higher) compared to other superconductor materials [3].  This means that HTS can use relatively cheap liquid nitrogen as a coolant to reach its required superconducting transition temperature.

HTS wind turbines use HTS wire in the generator’s rotor instead of copper wire. Since HTS wire has more than 100 times the current density of copper wire, HTS turbines are much lighter, smaller, and more efficient. Also, research is being conducted on making HTS wind turbines direct drive generators, which eliminates the use of heavy gearboxes that are associated with high maintenance costs in conventional wind turbines.

Conventional vs. HTS Wind Turbines

(Source)

Although HTS wind turbines that are currently in production have a capacity of around 2 MW, HTS turbines have the potential to reach 10 MW or more [4]. This is because HTS generators are more efficient and can be made half the size and weight of conventional generators of the same capacity. In early February 2009, American Superconductor Corporation (AMSC), a major company in the superconductor industry, announced that it is partnering with the U.S. Department of Energy’s National Renewable Energy Laboratory to produce a financial model for 10 MW HTS wind turbines. If the partnership results in a financially viable 10 MW wind turbine, wind energy could become a major energy contributor in the future. Especially if off-shore wind technology takes off.

One  issue that I did not see addressed in my research is the cost and energy consumption of large scale liquid nitrogen use in the HTS turbines.  If HTS wind turbines become popular, I would imagine a liquid nitrogen infrastructure would have to be developed to keep up with demand.

It will be interesting to see how wind energy technology develops, but as of now some major technological breakthroughs will have to come along if wind is going to make a major contribution to U.S. energy production.

Sources:

1) EIA Annual Energy Review 2008

2) Renewable Energy Focus, “Rise of the superconductor”. http://www.renewableenergyfocus.com/view/3224/rise-of-the-superconductor-/

3)American Superconductor Corporation. “MSC and U.S. Department of Energy Agree to Collaborate on 10 Megawatt-Class Superconductor Wind Turbines”. http://phx.corporate-ir.net/phoenix.zhtml?c=86422&p=irol-newsArticle_Print&ID=1254866&highlight=

4) AZoMaterials, “American Superconductor Receives Order for Wind Turbine Electrical Control Systems”, http://www.azom.com/news.asp?NewsID=20526

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2 Comments

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2 responses to “Superconductors in Wind Turbines

  1. aktownsend

    I am impressed by the stated potential reduction in both weight and cost (25% for each) in http://www.renewableenergyfocus.com/view/3224/rise-of-the-superconductor-/. However, I doubt a liquid-nitrogen infrastructure would be needed. Given that they’re mostly discussing these 10 MW turbines for offshore sites, I suspect the liquid nitrogen (or other low-temperature cooling fluid) would be created automatically onboard the turbines using a gas refrigeration cycle. I am more curious about the cost associated with manufacturing these materials and the generators, and what mechanisms they will need to fail-safe when the cooling system fails.

  2. alisonwhitt

    It looks like one of the main obstacles of this technology is the fact that HTS wire has a cost that is double that of the normal copper wire [1]. If the government set up an incentive program that gave extra tax cuts for using the new technology, it may be easier to implement.
    However, there do seem to be enough benefits to outweigh the extra cost. With the increased power output, the HTS turbines would most likely pay back the investment more quickly, especially with no maintenance costs for the gearboxes. Plus, with smaller scale turbines, transportation would be easier. Right now, for a “project of 150 megawatts (MW), transportation requirements have been as much as 689 truckloads, 140 railcars, and eight ships to the United States” [2]. Transporting lighter components, or more at once, could make large-scale installations easier than with normal wind turbines.

    [1] http://jrse.aip.org/04_14_09_high_temperature_superconductors_in_wind_turbines
    [2] http://www.awea.org/pubs/factsheets/transportation.pdf

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