9th October 2014

Fusion reactor concept could be cheaper than coal

The University of Washington is developing a new fusion reactor design that could be one-tenth the cost of ITER – while producing five times the amount of energy.

Fusion energy sounds almost too good to be true – zero greenhouse gas emissions, no long-lived radioactive waste, and a nearly unlimited fuel supply. Perhaps the biggest roadblock to adopting fusion energy is that the economics haven't worked out. Fusion power designs aren't cheap enough to outperform systems that use fossil fuels such as coal and natural gas.

Engineers at the University of Washington (UW) hope to change that. They have designed a concept for a fusion reactor that, when scaled up to the size of a large electrical power plant, would rival costs for a new coal-fired plant with similar electrical output. The team will present its reactor design and cost-analysis findings on 17th October at the Fusion Energy Conference in St. Petersburg, Russia.

“Right now, this design has the greatest potential of producing economical fusion power of any current concept,” says Thomas Jarboe, a UW professor of aeronautics and astronautics and an adjunct professor in physics.

The reactor – called the dynomak – began as a class project taught by Jarboe two years ago. After the class had ended, Jarboe and doctoral student Derek Sutherland (who previously worked on a reactor design at MIT) continued to develop and refine the concept.

The design builds on existing technology and creates a magnetic field within a closed space to hold plasma in place long enough for fusion to occur, allowing the hot plasma to react and burn. The reactor itself would be largely self-sustaining, meaning it would continuously heat the plasma to maintain thermonuclear conditions. Heat generated from the reactor would heat up a coolant that is used to spin a turbine and generate electricity, similar to how a typical power reactor works.

“This is a much more elegant solution, because the medium in which you generate fusion is the medium in which you’re also driving all the current required to confine it,” Sutherland says.

There are several ways to create a magnetic field, which is crucial to keeping a fusion reactor going. The UW’s design is known as a spheromak – meaning it generates the majority of magnetic fields by driving electrical currents into the plasma itself. This reduces the amount of required materials and actually allows researchers to shrink the overall size of the reactor.

Other designs, such as the ITER experimental fusion reactor being built in France – due to be operational in 2022 – have to be much larger than UW’s because they rely on superconducting coils that circle around the outside of the device to provide a similar magnetic field. When compared with the fusion reactor concept in France, the UW’s is much less expensive – about one-tenth the cost of ITER – while producing five times the amount of energy.

The UW researchers factored the cost of building a fusion reactor power plant using their design and compared that with building a coal power plant. They used a metric called “overnight capital costs,” which includes all costs, particularly startup infrastructure fees. A fusion power plant producing a gigawatt (1 billion watts) of power would cost $2.7 billion, while a coal plant of the same output would cost $2.8 billion, according to their analysis.

“If we do invest in this type of fusion, we could be rewarded because the commercial reactor unit already looks economical,” Sutherland said. “It’s very exciting.”

Right now, the UW’s concept is about one-tenth the size and power output of a final product, which is still years away. The researchers have successfully tested the prototype’s ability to sustain plasma efficiently, and as they further develop and expand the size of the device, they can ramp up to higher-temperature plasma and get significant fusion power output. The team has filed patents on the concept with the UW’s Centre for Commercialisation and plans to continue developing and scaling up its prototypes. The research was funded by the U.S. Department of Energy.

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