American Superconductor has launched a new 12 month collaborative effort with the United States Department of Energy to evaluate the cost of a 10 MWe class wind turbine employing high temperature superconductors. The aim is reduce the costs of wind generated electricity through the use of higher unit capacity wind turbines.
American Superconductor Corporation has entered into what is called a co-operative research and development agreement (CRADA) with the US Department of Energy’s National Renewable Energy Laboratory and the Department’s National Wind Technology Center, with the aim of validating the economics of a 10 MWe wind turbine incorporating superconductors. American Superconductor is separately developing components and system designs for a 10 MWe class machine. According to AMSC, a CRADA “allows the federal government and industry partners to optimise their resources, share technical expertise in a protected environment and speed the commercialization of technologies.”
Under the 12 month programme, AMSC Windtec (www.amsc-windtec.com), a wholly owned subsidiary of AMSC, will analyse the cost of the 10 MW class superconductor wind turbine, including direct drive superconductor generator, blades, hub, power electronics, nacelle, tower and controls. The NWTC will then benchmark and evaluate the wind turbine’s economic impact, both in terms of its initial cost and its overall cost of energy.
The Department of Energy and its National Renewable Energy Laboratory (www.nrel.gov) believe that wind power will represent a significant fraction of the USA’s power production in the years to come and, according to NREL director Dan Arvizu, “high temperature superconductors hold promise for helping lower the overall cost of wind energy.”
Direct approach
Direct drive wind generator systems using high temperature superconductor (HTS) wire instead of copper wire for the generator’s rotor are expected to be much smaller, lighter, more efficient and more reliable than conventional generators with gearboxes. American Superconductor estimates that its high temperature superconductor technology will enable a 10 MW class generator to be manufactured that will weigh as little as 120 metric tons, compared with about 300 metric tons for future direct drive generators of an equivalent power rating but employing conventional (ie non superconducting) generator technology.
In addition, direct drive generators eliminate the need for massive gearboxes, the component with the highest maintenance costs in conventional wind turbines. This will open up the opportunity for the development of wind farms in more areas on land and offshore.
The superconductor generators that AMSC intends to use for the 10 MWe class wind turbines are based on proven technology AMSC has developed for superconductor ship propulsion motors and generators under contracts with the US Navy. AMSC recently announced that a 36.5 MW superconductor ship propulsion motor it designed and manufactured for the Navy was successfully operated at full power and is ready for deployment.
In a parallel development, American Superconductor and TECO-Westinghouse Motor Company have, since October 2007, been working on a project to develop HTS and related technologies for 10 MWe class direct drive wind generators under an award from the National Institute of Science and Technology’s Advanced Technology Program (ATP). The CRADA and ATP programs are intended to serve as a prelude to follow-on programmes aimed at building and testing a full-scale prototype superconductor wind turbines, prior to commercialisation.
Breaking the 6 MW barrier
Wind turbine power ratings have been increasing steadily while the price per megawatt has declined, enabling wind power to achieve economic parity with conventional generation sources in prime wind locations, says AMSC. Due to the limitations of conventional technologies, however, the largest wind turbine ratings top out at approximately 6 MW due in part to practical limitations on the physical size and weight of the generators that must be transported over roads and supported on towers hundreds of feet in the air.
Disruptive technology
“HTS is one of the ‘disruptive technologies’ needed to break through wind power’s capacity barrier and significantly reduce its cost of energy,” says Dan McGahn of AMSC. He also notes that AMSC is well placed to apply the technology to wind turbines, having a good track record in commercial wind turbine design and as a supplier of power electronics, with “strong ties with wind turbine manufacturers around the world, including TECO in Taiwan, Sinovel Wind in China and Hyundai Heavy Industries in Korea.”
According to industry research firm Emerging Energy Research, approximately $27 billion was spent on wind turbines in 2007. That figure is expected to double to over $55 billion annually by 2015.