As wind energy continues to grow in Germany and the offshore market gears up for massive development, electricity network expansion and stability are no longer issues the industry can ignore. "The feed-in and forget phase of the national wind powered electricity generation market is over," says Jens-Peter Molly, who heads Deutsche Windenergie Institut (DEWI), the Germany wind institute. "We are facing a situation where we have to find ways of transmitting wind generated power to consumer centres and to stabilise the networks."
Such has been the over-capacity in both generation and transmission in Germany until now, that absorbing wind power and its fluctuations has not posed much of a problem. Where there have been local bottlenecks, network operators -- obliged by the Erneuerbare Energien Gesetz law to take all renewables generation onto their grids -- have fixed them. In practice, the fixing has mainly been done by E.on Netz, the huge operator covering the entire north of Germany where most wind plant are installed. E.on, so far, has digested the costs of grid expansion and German wind turbine operators have been little troubled by the logistics of ensuring a stable supply of power to the customer.
Those days, however, are nearing their close. Bottlenecks will start to occur in getting wind electricity from where it is generated to the major urban centres of consumption. New network will be required. Who will mastermind its construction and how its costs will be funnelled through to consumers are questions still to be answered.
E.on Netz, however, is moving to meet the wind industry's needs. As owner of the corridor of high voltage network stretching from Germany's Danish border through to Austria, it expects to invest EUR 550 million in new 110 kV and 380 kV network for transport of wind generated power over the next 12 years. The costs will be added to its network usage charges, levied on all customers whose supply uses the E.on Netz network.
But with plans for 20-40 GW of wind power in northern Germany (on land and offshore) all expecting to feed into the north German network, "It becomes a European problem to distribute the power," warns Uwe Radtke of E.on Netz. Once offshore stations are built, continues Radtke, an "overlay grid" is necessary. "As a rule of thumb, for every 15 GW you need 1000 km of network, so if you escalate to 25 GW of wind, you can multiply up to get the length of network you'll need," he adds. The required expansion will also involve high transmission networks owned by other companies, like RWE and Vattenfall Europe, which have less experience with wind generation than E.on.
Molly stresses the European dimension to system security posed by growth in German wind development. If a 1200 MW nuclear power station connected to the E.on Netz network suddenly went offline, the network frequency could drop below 49.5 Hertz, triggering the cut-out of 3-4 GW of wind capacity, he says. The total outage of up to 5 GW of nuclear and wind capacity could not be stabilised by the European network, which has a limited instantaneous generation reserve of just 3 GW, Molly warns.
To tackle this problem, E.on Netz is introducing new regulations aimed at improving network stability. New turbines must be less sensitive to frequency fluctuations, with a lower threshold for disconnection of 47.5 Hertz. The present trigger point of 49.5 Hertz is too high to weather the consequences of a large power station outage, Molly explains.
The new regulations will help, but Molly still suggests that as wind energy use spreads, a joint European grid control management with a focus on wind may be useful. This could be a task for the Union for the Co-ordination of Transmission of Electricity, based in Luxembourg. It co-ordinates the interests of transmission system operators in 20 European countries "providing a reliable market base by efficient and secure electric power highways."
Looking further ahead, strong political support for wind energy in Germany could drive expansion at such a pace that by 2030, Germany may have 20-25 GW of wind generation onshore and 26 GW offshore. The 47 GW would be more than half of Germany's peak national demand, then expected to be about 75 GW.
Whether cross-border co-operation can help Germany absorb wind fluctuations at that level of generation is not clear. Molly is sceptical and anticipates that "some of the wind's energy may have to be put to uses other than electricity generation." He urges that measures to this end be initiated now "because new energy applications take 20 to 30 years to mature."
Part of the dilemma is due to uncertainty over exactly where -- and how fast -- wind development will continue and how it will integrate with conventional power station new-build. The period from 2010, when German offshore wind is expected to take off, coincides with the years in which conventional generators anticipate renewing much of their middle-load coal station capacity and in which nuclear stations will be steadily decommissioned under Germany's nuclear phase-out legislation.
The job of finding some answers to the many questions has been handed to the Deutsche Energie Agentur (DENA), the German energy agency. It will be commissioning an economic study into network integration of German wind energy development onshore and offshore to 2020. The work will draw up several scenarios for the short, middle and long term outlook and investigate what conventional and renewable power station capacities are likely to be built where and when.
"The project will take nine to twelve months. Uniquely, it will be jointly financed by the renewables and broader electricity sector," says Markus Kurdziel, head of renewables at DENA. Among the backers are the Bundesverband Erneuerbare Energien (the federal renewables association), wind organisations, the network operators of major energy companies E.on, RWE and Vattenfall Europe, as well as various electricity lobby organisations. No government funding is available for the study, Kurdziel says. The investigation will not include a European dimension. "We have to take things step by step," he says.