Reliable power from multiple sources

By 2050, Germany aims to meet all its electrical-power needs from renewable sources such as wind, water, sun and biomass. Most experts agree that this is a realistic goal. But the country still has a long way to go to wean itself off its reliance on nuclear energy and fossil fuels: there are many windmills yet to build, solar panels to erect and cogeneration units in private households to be installed. And while all this is happening, the old, rigid, region-based power network must be overhauled and its flexibility increased.

Petr Korba and Mats Larsson have made major contributions to developing a more intelligent network of that kind. In recognition of their work, which originally aimed at making large power networks less prone to blackouts, they have now been nominated for the European Inventor Award 2011, to be awarded on 19 May in Budapest.

All experts agree that constant electricity supply can be guaranteed only when tomorrow's power - produced in a decentralised system using a wide variety of sources - can be fed into the grid in a flexible yet stable way. In particular, the system must compensate reliably for overcast or windless weather - sun and wind are not always there when demand for electricity peaks. The Swiss researchers' contribution to the "smart grid" of the future impressed the prestigious Massachusetts Institute of Technology (MIT) so much back in 2004 that it identified their Wide Area Monitoring System (WAMS) for power networks as one of the ten technologies that would change our lives by 2014. 

Synchronised by GPS

In a WAMS, devices known as phasor measurement units collect data on voltage and current at certain places in the network, supplemented by GPS time and location data, and forward it to a system control centre. There it is evaluated by special computer programs which track it right down to microsecond level. This makes the new monitoring system at least 100 times faster and more accurate than its predecessors.

Not only does this help to stabilise supply and demand, it also optimises transmission capacities, as the system works out the best ways to react to power swings or overloads. "Our inventions are about the intelligent control and automation of electrical currents with a view to making our networks more stable", is how Larsson describes their work. "The main difficulty with electricity is that it always has to be produced and consumed in equal amounts," explains Korba. "Otherwise the system becomes unstable and starts to oscillate".

Power swings, due for example to minor system disruptions, can cause large amounts of electricity to get shunted backwards and forwards in seconds between, say, Portugal and Poland. This takes up valuable network capacity and increases costs for system providers. The cause may be just a brief, unexpected outage at a provider somewhere. Others then automatically try to bridge the gap. This can lead to over-compensation, which triggers swings. "There are always swings like this in networks. As long as they are properly damped, there is no problem. But if not, they can even cause blackouts", explains Korba.

To equip European power networks for the future, Europe would need to spend around EUR 200bn by 2020, estimates EU energy commissioner Günther Oettinger. China has announced that it plans to invest nearly EUR 470bn in its electricity network over the same period. The International Energy Agency reckons with annual spending of EUR 35bn to 55bn on intelligent networks worldwide.