x Abu Dhabi, UAESunday 23 July 2017

Superconductivity may help renewable energy

Superconductivity could help boost the world's renewable energy.

The UAE's commitment to renewable energy last week won a major accolade, with the announcement that Abu Dhabi is to be the permanent home of the International Renewable Energy Agency (Irena).

To many outside the region, the UAE's enthusiasm for renewable energy comes as a major surprise. Why would one of the world's biggest oil producers, with plentiful reserves of the natural resource, be bothering with the likes of wind farms? Those familiar with the UAE's view of the future have no trouble understanding the motivation. It is simply doing what all prudent nations should be doing: planning for the long-term prosperity of its people.

Seen in that light, the biggest surprise about last week's announcement was that it has taken so long for the world to set up an organisation like Irena. Certainly it is long overdue; its nuclear counterpart, the International Atomic Energy Agency (IAEA), was set up in 1957 when there were only a handful of nuclear power stations in operation. Today, renewables represent around a quarter of all the world's sources of power and provide almost a fifth of global electricity supply.

Despite this, there is still a pervading sense that renewables are a risky basket into which to put the world's energy eggs: fickle, uneconomic and laden with unintended consequences. It's hard to escape the suspicion that there is something missing from the renewable energy equation - a key technology that could transform its status. And some believe they know what it is, a phenomenon that was discovered exactly a century ago this month: superconductivity.

In April 1911, Heike Kamerlingh Onnes of the University of Leiden in the Netherlands was carrying out seemingly esoteric experiments into the effect of ultra-cold temperatures on metals. He was following up suggestions by theorists that something odd might happen to the ability of such metals to conduct electricity if they were chilled to temperatures close to absolute zero, minus 273 degrees Celsius. Most thought the conductivity would plunge to that of materials like rubber. They could not have been more mistaken. As Onnes chilled the metal mercury with ultra-cold liquid helium, he found that its electrical conductivity suddenly soared to levels so high they could not be measured.

Onnes's stunning discovery won him the Nobel Prize for physics just two years later, but superconductivity continued to spring surprises for decades afterwards. And some of them have huge potential for improving the prospects of renewable energy.

Most obviously, superconducting wire is far better for transmitting electricity than conventional cables. That, in turn, can boost the attractiveness of renewable sources such as solar cells and wind farms and enable smaller facilities to deliver the same amount of power. Their economic viability would also be transformed.

For example, in the case of offshore wind farms, most of their cost lies in installing them at remote marine sites. By boosting their effective power output using superconducting cables, the time it takes to recoup investment can be drastically reduced - along with the need for state subsidies.

Superconductivity can also help with another major pitfall of renewable energy: its fickle nature. Wind, wave and solar power all rely on nature's co-operation, which in many parts of the world simply cannot be relied upon. Wind power is especially vulnerable: last December, parts of Northern Europe experienced meteorological conditions that led to a combination of bitterly cold temperatures and virtually no wind. At one stage, wind turbines in Britain were producing barely a hundredth of their normal output - just when energy demand was soaring. Paradoxically, strong winds are hardly less problematic, with turbines having to be shut down to protect their blades and complex gearing systems. Even in day-to-day operation, their output can lurch dramatically, causing severe problems for engineers trying to feed megawatt-sized swings of electrical power into grids.

Superconductors can help tackle such "intermittency" problems via a bizarre phenomenon discovered in the 1930s. If a magnet is brought near a superconductor, it experiences a force field that allows it to defy gravity and levitate. Known as "flux expulsion", this is more than just a party trick, however; it can be used to create frictionless bearings for gigantic energy-storing flywheels. The electricity produced by, say, wind turbines is used to spin up these flywheels, which then spin rapidly at a virtually constant rate on their frictionless bearings. Their huge rotational energy can then be turned back into electricity whenever it is needed - even if the wind turbines that supplied them are no longer turning.

Given these advantages, why aren't superconductors a standard component of renewable energy systems? Part of the answer lies in the fact that their magical properties have yet to be triggered at anything other than very low temperatures. For decades, materials had to be cooled in expensive and dangerous liquid helium before they would become superconducting. A Nobel-winning breakthrough in the mid-1980s led to the discovery of new families of materials that became superconducting at the almost balmy temperature of minus 200 degrees Celsius. But these materials have proved hard to translate into commercial properties.

Even so, such "high temperature superconductors" are starting to make their presence felt in the renewable energy field. The US company American Superconductor recently unveiled a 10-megawatt wind turbine, whose superconducting components are said by the company to make it the most powerful of its type in the world.

Yet if superconductivity is ever to escape its niche, some way must be found to trigger its appearance at room temperature. The problem is that even a century after it was discovered, superconductivity is still far from fully understood. A broad-brush description of how it works has been around for decades, but it gives few clues as to how to make the long-sought room-temperature superconductor.

Theoretical physics is often portrayed as far removed from the challenges of daily life. Yet the history of breakthroughs such as the laser and the transistor show that the biggest advances come from having a thorough understanding of what happens inside the crystal lattices of esoteric materials. Until theorists do the same for the enigma of superconductivity, the solution to the world's energy problems may forever elude us.

 

Robert Matthews is visiting reader in science at Aston University in Birmingham, England