Clean Tech

A breakthrough in the air

M. Ramesh | Updated on January 15, 2018

wind turbine

MRamesh on how the next big thing in wind energy is superconducting generators that will soon be on test

Next year, a wind turbine on the western coast of Denmark will turn out to be a very special one, and will be marked out for close monitoring and intense study. A consortium of nine companies, working on an EU-funded project, will remove the existing generator from the turbine, and replace it with a very different gadget – a superconducting generator. The 3.6 MW machine, made by Envision Energy of China, will be the world’s first windmill to feature a superconducting generator and its success will be nothing short of epochal.

Few doubt that the device will work well, the object of the study is more to get data and see if some tweaks are required. Once perfected, it could pave the way for large scale offshore wind farms.

The wind industry has been eyeing superconducting technology for some time. The science behind superconductivity is well-known, but milking it for benefits has been a challenge. Superconductors are super-cooled electricity conductors through which current zips through, meeting with almost no resistance (see box).

A crucial milestone

The EcoSwing project is meant to develop a generator with superconducting coils. Now, the generator is ready. In June, one of the members of the consortium, a German company called Theva, whose role in the group was to supply the superconductors, announced success in lab testing. It was a crucial milestone, because the superconductors were the heart of the project. Now that the generator is ready, they are gearing up to fix it in a windmill to see it in action.

This is an exciting phase, because the benefits of superconductive generators are significant. Due to limitations of land availability, wind speeds and logistics. large wind turbines are not appropriate for onshore installations; on the seas, where wind blows much faster and ‘land’ is unlimited, you can build huge machines. As a thumb rule, the bigger the machine the lower the cost of energy. Siemens’ 6 MW offshore turbine is said to be a winner of a product and the industry would like to move on to 10 MW and beyond—but, beyond a point in size the economics behave differently.

Larger machines require more foundation and demand more rupees for transportation to site and setting up.

Here is where superconductive generators come into play. For the same purpose, they are much smaller and light-weight than conventional generators. EcoSwing’s resources say it can be 40 per cent smaller than a conventional generator of comparable capacity.

Leap of faith

Superconductive generators are new animals and to adopt one, an investor needs to take a leap of faith. The superconducting generator that EcoSwing consortium will test in the 3.6 MW machine in Denmark is expected to provide proof of the pudding. Its success can expand the market for wind power.

However, EcoSwing is not the first. The American company, AMSC, has some experience in handling superconductivity and has provided a mammoth 36.5 MW superconducting motor to the US navy for propelling ships. Motors and generators are similar. Generators produce electricity using rotation while a motor does the opposite—it uses electricity to produce rotation. On the basis of its motor experience, AMSC has developed the design for a 10 MW superconducting wind turbine.

The company does not produce the machines, but licences technology (incidentally, India’s Inox Wind is an AMSC licensee.) While the design for the 10 MW superconducting machine is ready, it appears that AMSC is yet to select a licensee, presumably because of the difficulty in finding someone to bell the cat.

Therefore, the more people talk about and work on superconductive generators for wind power, the better it is for confidence. For sure, these new generation machines are not for Monday morning—they will take time to mature. Dr Marcus Bauer of Theva gives it a decade. “Ten years from now, we will be seeing a lot of superconducting technology out there,” Dr Bauer says.

Envision Energy, founded only in 2007, might be one of the earlier adopters, judging by the statements of its founder, Lei Zhang. The company has developed conviction in superconductive generators. “It is not science fiction (anymore),” says Jesper Hansen, a Senior Project Manager with Envision Energy. “It is something that is here and now.”

A miracle technology

When current passes through a conductor its flow experiences an obstruction, called resistance. Metals, like copper, offer low resistance and hence are good conductors, whereas materials like wood are the opposite. Resistance causes the conductor to heat up, resulting in loss of energy.

It has been found that if certain materials are cooled to very, very low temperatures, their resistance goes down and electricity rushes through (somewhat like pods in a vacuumised tube that Elon Musk hopes to bring in for rapid transportation.) Super cooled materials that offer no resistance to electricity are called ‘superconductors’.

Different materials exhibit superconductive properties at different temperatures. Search is constantly on to discover materials that become superconductive at less low-temperatures. Thus, when they speak of ‘high temperature superconductivity’ (HTS), they are talking about temperatures such as minus 240 degrees Celsius. In 2001, some Japanese scientists discovered that a compound called magnesium diboride (MgB2) turns superconductive at 39 K, (around minus 234 degrees Celsius). Today, MgB2 is a favourite among the HTS aficionados.

Now, it is not enough to cool a wire to that extent once—the wire must be kept cooled all the time. That involves keeping the wire in a bath of liquid helium or liquid nitrogen, with all the appurtenances such as cryostats for keeping the helium cool – thus superconductivity is not easy to handle. But if you get it right, you suck out much larger amounts of electricity from a generator or transfer more power over transmission lines without much loss.

Published on November 09, 2016

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