Is Superconductivity Cleantech?

I’ve heard some feedback from people asking why superconductivity is given a voice in a cleantech blog. This is a good question. There are a few reasons.

In one area in particular–power quality–superconductors are directly related to renewable energy. Advanced, flywheels, superconducting magnetic energy storage, superconducting fault current limiters, etc. are all being proposed as technologies that will allow for erratic, geographically distributed generation sources such as wind and solar to be brought onto power grids more effectively. Basically, superconducting power systems developers believe without some way of balancing load versus supply, electric utilities have a difficult time matching load with supply, and all the resulting economic and technical problems that come with it. Also, add-on generation grids such as wind farms are prone to introducing fault currents to the main grid, or require VAR compensation—both of which increase the cost of using that energy. Superconductors are being used in the development of solutions for all three of these problems. Siemens, GE, Sumitomo Electric, IGC SuperPower, American Superconductor, SC Power, CAS in China, KEPRI in Korea, and a bunch more are, or have been, working in this area, and their technologies and businesses have been reported on in some detail.

Perhaps more speculative, developers of high temperature superconducting (HTS) generators are looking to put them in wind turbines. The main reasons for this have to do with the electrical properties of AC superconducting machines, an also because such machines would be dramatically lighter and smaller than conventional generators. There is also some improvement in generation efficiency.

The cost of cooling superconductors is not necessarily a significant hurdle, and refrigerators that cool superconducting devices to their 30 to 65 degrees Kelvin operating temperature are commercially available. Admittedly, the technical challenges of integrating the cooling systems within the device are sometime daunting.

One last reason why superconductors may be considered by some to be “clean tech” is because they may, in fact, provide a cleaner alternative to conventional technology.

For example: in a story we are preparing in Superconductor Week, we look into the massive transformers that are used in substations to take power from transmission voltages to distribution voltages. These devices are inefficient, dangerous, and environmentally hazardous. One company researching the topic concluded that existing conventional 26MVA transformers contain seven tons of copper winding, 16 tons of iron, and 14,000 liters of highly flammable oil. In contrast, an equivalent HTS transformer could contain just 200kg of superconductor in its windings, which are immersed in non-flammable and environmentally benign liquid nitrogen.

In addition, this research concluded that operating at full load, such a HTS transformer would provide an annual abatement of 1,500 ton of CO2 and save $900,000 in electricity over its lifetime. The study concluded “that by including the installation of HTS transformers as part of their national abatement strategy… countries could meet a significant proportion of their Kyoto protocol targets.”

The question of whether superconductors are “clean tech” is semantic. The real question is, can developers make HTS devices that work, and can utilities be persuaded to buy them?

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