Fears over energy security and climate change have led to record investment in renewable energy. But a major problem threatens to stall progress towards a more sustainable future: national electricity grids are far from ready to cope with the variable output from the new technologies.
A solution might be at hand, though, and would not involve radical changes to the existing infrastructure. Treating groups of dispersed power sources, such as solar and wind generators, as a single entity could solve the problem, creating the virtual equivalent of a single large power station.
ā[The power companiesā existing] philosophy is that theyāre going to run the grids as if these new renewable sources did nothing to help ā a āfit and forgetā strategy,ā says at Imperial College London, UK.
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Thatās because grids must always match the regionās energy requirements, second by second, and renewable sources go through extreme fluctuations as the sun goes in, night falls, or the wind drops, says Peter Lang, at , the Distribution Network Operator for London, East and South East of England.
If energy generation doesnāt match energy use, power cuts or overload is the result. But as investment in renewable sources grows, grids will have to adapt to less reliable sources.
Chaotic grids
The ever-growing number of wind farms in Europe, and the US are in particular forcing the hand of grid maintainers. And growing interest from consumers in microgeneration ā installing, say, solar panels to cover their own needs and selling any excess back to the grid ā presents an even greater headache.
In coming years, the number of generators contributing to the grid is set to balloon dramatically by thousands or even millions. āThe logistics of controlling even a few hundred large power stations are difficult,ā says Strbac.
The best solution suggested so far is a concept known as the āvirtual power plantā, says Lang. Each virtual plant consists of several hundred or thousand microgenerators lumped together in cyberspace into a unit comparable to that of a large power station.
Mixed bag
A virtual power plant can contain a mixture of different generators, for example wind turbines, solar cells, hydroelectric dams, and biomass-fuelled combined heat and power stations. A well-chosen mix of all these types can offset the inherent unreliability of different generators to make a virtual plant that can be treated much the same as a conventional one.
Homeowners might benefit from the arrangement too. Strbac says that, in theory, the owner of, say, a few photovoltaic cells could opt to switch between a number of virtual power plants during the day to find the best price for their power at any precise moment.
Implementing virtual power plants is possible with relatively little modification to existing infrastructure, says Lang. āItās not about wholesale replacement of the existing system ā youād never be allowed to do something so disruptive ā itās about looking at the existing network and seeing what we have to do to monitor it more successfully,ā he says.
Large-scale trial
Field trials of the virtual power plant concept have taken place in Woking, UK, and are due soon in the Ćlava province in Spain, as part of a EU-funded project called . The project brings together academics like Strbac from across Europe, along with a number of large energy distributors, including EDF and .
The Ćlava trial will begin in September, and will see the FENIX team use live data from renewable energy generators in the area to see how it could be repackaged into virtual power plants. Although it wonāt use that to control real energy demand, the team hopes to show the technique works.
āThe portfolio [of energy systems in the Alava virtual power plant] has around 100 megavolt-amperes [100 megawatts] installed capacity,ā says Juan Marti Rodriguez of Iberdrola, which could provide Ćlavaās 300,000-strong population with around half of its peak load.
The trial will account for 1 per cent of Spainās entire energy distribution Rodriguez adds: āItās not too difficult to imagine applying the FENIX concept for the whole country.ā
