The deadline for most purposes is mid-2010, for advanced network support, summer 2011. From those dates, all new wind turbines tying into the German electricity network must comply with the country's grid services rules, as detailed in a ruling that came into force on July 11 2009. Failure to comply with the new rules will disqualify offending machines from the premium power purchase rate for wind production paid to all wind turbine owners in Germany.
The deadline extension for fast-response dynamic network support during any type of grid failure to mid-2011 was negotiated with the wind industry as part of a transition period to allow development of new technology to comply with the rules.
In return for the grid support services that retrofitted old wind turbines and new turbines with the new technology will provide, the owners become eligible for a "system service" bonus per kilowatt hour produced, as has long been the case in Denmark, Germany's neighbour to the north and, more recently, in Spain.
Germany, as an early starter in wind energy, is home to thousands of old wind turbines installed during the 1990s, many of which are not technically equipped to provide basic grid support, such as riding through voltage dips on the network without tripping offline and providing momentary boosts of power to help stabilise the system when required. But with about 8% of Germany's electricity now coming from nearly 25 GW of wind power - with expectations of 36 GW of wind online by 2020 - wind turbines are being legally required to fully comply with a series of grid code specifics.
The new ordinance is described as a breakthrough by Jens Bomer of Dutch Ecofys, which provides network consultancy services for wind integration. According to Bomer, keeping the grid stable is essential if older wind turbines are not to trip offline whenever there is a grid fault. With so many turbines producing so much power, no longer can the transmission system operators (TSOs) tolerate them cutting out whenever there is a momentary network disturbance - and remaining offline until manually restarted. Ensuring grid stability to stop this happening is the job of all other power stations, including newer wind turbines.
Grid services rules in Germany, known as Grid Codes, are traditionally the responsibility of the four TSOs. Two years ago they adopted the Transmission Code 2007 for high-voltage lines (110 kV, 220 kV and 380 kV) that, like the 2003 code, takes wind power into account. That code was further developed into a Distribution Network Code for lower-voltage wires, introduced in 2008. It is only now, however, that the details of the texts have been clarified and the wind specifics of the Grid Code enforced by a system services ordinance, the Systemdienstleistungsverordnung, or SDLWindV. The ordinance contained some surprises, however.
While the wind industry had long prepared for strict application of the code, it had not expected the ordinance to include specifics that were tougher than the TSOs Grid Codes. The ordinance introduces a sophisticated requirement for fast-response dynamic network support during any type of grid failure - such as that caused by a short circuit at the Krummel nuclear plant on July 4.
In future, wind turbines are being asked to provide the same kind of grid support as conventional power plants, also in connection with reactive power. From now on they must provide near instantaneous injections of reactive current to stabilise even mild network faults - a speed and reach of response in the ordinance that was not included in the 2007 and 2008 codes. Of all other major wind markets in the West, only Spain by law also requires wind turbines to provide reactive power, but not as rapidly as Germany is demanding. The need for suppliers to develop and install equipment that can achieve this in new turbines to comply with the rules is the main reason the extended transition period to mid-2011 was introduced, says Ralf Bischof of the national wind association, the Bundesverband Windenergie.
Older turbines
The level of grid support required by the new ordinance depends on when each wind plant was first operational. After mid-2011, all new turbines being connected to the grid must be fully compliant with the ordinance - that is the both the Grid Codes and the additional fast-response dynamic network support requirement. Turbines installed between 2009 and mid-2010 are eligible for the system service bonus provided they meet the Grid Code requirements, whether or not they can provide fast-response reactive power. Wind turbines installed between 2002 and 2008 are not obliged to comply with the Grid Codes nor the stringent reactive power requirement, while older machines that cannot comply with the Grid Codes without major component replacement are largely unaffected by the guidance. Prototype turbines have a two-year period from commissioning before they must comply with the rules, when the bonus is backdated to the start of operation.
The bonus amounts to EUR0.005/kWh for all turbines commissioned between 2009 and the end of 2013. From that point, the government expects the necessary technology for meeting grid operator requirements to be ex-factory standard for wind turbines rather than a costly add-on. The bonus is applicable for an effective specified volume of production, or for the first five years of operation, whichever comes first. For turbines installed from 2002 to 2008, compliance with Grid Code rules by retrofitting before the end of 2010 releases a higher bonus of EUR0.007/kWh, payable for five years. Of the 14.5 GW of wind capacity installed in that period, about one third cannot be retrofitted economically at the level of the available bonus.
The country's major turbine supplier, Enercon, is quietly critical of the requirements in the ordinance that are tougher than those originally requested by the TSO grid codes. "This may be partly due to the limited participation by turbine manufacturers in drawing up the list of requirements," the company says.
Vestas, Enercon's main competitor in Germany, says wind stations comprising only its turbines can be retrofitted to meet most of the requirements. "The extent to which the then more stringent requirements can be fulfilled with current wind turbine configurations is being investigated in-house," says Vestas.
Repower Systems expects to be able to make a public statement at the end of the summer on the impact of the new rules.
Bomer says the government's deadline is tight and it may not be possible to retrofit all the turbines that could economically benefit from complying with the ruling. "The challenge certainly lies in the time allowed," he says. "Turbine builders will probably react by prioritising certain of their turbine types for retrofitting."
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