Electricity generation from German solar installations topped national wind generation in May for the first time. Together, wind and solar are ousting conventional forms of generation, prompting major new investment in the transmission system. But predicting exactly where and how much new transmission capacity is needed is a tall order for transmission system operators (TSOs) and the federal energy regulator.
Solar output reached 4.15TWh in May compared with 2.89TWh of wind generation, according to energy analyst Spider Energy. The last time solar came close to topping wind was in July 2010 when wind output reached 1.58TWh and solar 1.57TWh, the analysis of electricity trading data reveals. Around 27GW of solar capacity is currently installed in Germany compared with around 29GW of onshore and offshore wind.
Although the weather obviously plays a role in how much wind or solar energy is generated, solar's performance in May made it clear that photovoltaic is now on a par with wind in terms of generation capability and is also swiftly becoming cheaper. Already, on days when national electricity demand is low, coal and gas fired stations are often largely ousted from the generation mix, either by wind, by solar or by a mix of both.
This has implications for the country's electricity transmission system. The main locations for coal, lignite and nuclear power stations are different to those of the mainly decentralised photovoltaic plants, the largely rural locations for wind farms more often found in northern Germany, and offshore stations in the North and Baltic Seas. Some power transmission routes are becoming much more heavily trafficked and new routes need building, while other routes are required to a lesser extent.
In preparation for the new network investment required, Germany's four transmission system operators (TSOs) are currently drawing up a masterplan to establish what is needed. The plan will be adjusted year by year to take potential new developments into account such as swift wind and solar expansion in southern Germany or expansion of electricity storage, which could reduce transmission need.
The draft network development plan - NDP2012 - presented at the end of May by TSOs is based on three scenarios for development that were accepted as plausible by the federal energy regulator, Bundesnetzagentur last December. After consultation and potential adjustments, the plan is due to be ready by the end of the year.
The investment of EUR19-23 billion foreseen in the first draft of NDP2012 for the next ten years will make Germany's transmission system fit for the future, said Hermann Albers, president of Germany's wind energy association Bundesverband Windenergie (BWE). Albers said the existing network is totally outdated and that the expansion of renewables, increased interconnection with other European networks and the future feed in of conventional power stations renders it no longer fit for purpose.
This investment would cost the consumer an extra EUR0.004 per kWh, according to the federation of new energy suppliers, BNE, around EUR16 per year for an average household. But further costs are looming, warned the BNE in June, referring to reports that EUR25 billion more needs to be spent on the local electricity networks and up to EUR17 billion on offshore cables to shore.
Some question whether such large investments are really necessary. A reduction in electricity consumption and accelerated expansion of wind in southern Germany could make much of the planned new onshore cable routes superfluous, said environment organisation BUND.