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Planned new high-voltage transmission cables in northern Germany -- ostensibly to transport growing wind energy generation -- have become a matter of hot dispute. Local protest groups are intervening in permitting procedures with concerns about health, the landscape and value of their properties as network companies E.ON Netz and RWE Transportnetz Strom seek to install pylons carrying 380 kV transmission cables across kilometres of countryside, encroaching on single dwellings and groups of housing and threatening to sweep through landscape protection areas.

The spotlight is currently on E.ON Netz' plans for a 60 kilometre overhead cable between Ganderkesee and St Hülfe, near Diepholz in Lower Saxony, designed to strengthen the high voltage network in the region between the rivers Ems and Elbe for both wind energy transmissions and for power trading.

The new cable is one of several identified as being indispensable for the growth of wind power in a report released early last year by the German energy agency, The Deutsche Energie-Agentur (DENA), on network integration of wind. The cable would increase the capacity of existing connections between E.ON's high voltage grid and RWE Transportnetz Strom's network, allowing more power to be transmitted to the industrial Ruhr region to the south. There are three existing north-south cables in north-west Germany. There is no west-east high voltage link north of Hannover.

Gaining permits for the new cable involves around 50 public authorities while 1600 critical contributions have been submitted by the general public. The process is expected to take many years, according to Lower Saxony's ministry for rural affairs. When the newest stretches of high voltage network were built in the 1970s and 1980s for connection of new nuclear power stations the permit process was far simpler. "Standards were much laxer then. The plan covered one sheet of paper, about five public authorities were involved, procedures took around four weeks and the final documentation may have been ten pages long," according to one planner.

Warning -- high voltage

A local pressure group from Eydelstedt, Vorsicht-Hochspannung (Warning -- High Voltage), with over 2500 members, questions whether the new route is really needed. "Those arguing for the new cable say it is required to accommodate the maximum possible power generation from future offshore wind energy -- but peak load will only occur for about 6% of the time," argues Vorsicht-Hochspannung.

The group has a point. According to wind energy research centre ForWind, the three existing north-south transmission routes in northern Germany, owned by E.ON Netz, have a maximum capacity of 6200 MW. Minimum consumption in the region is currently 3300 MW while maximum wind input is 4700 MW. Conventional power stations and power imports feed in 3800 MW. The difference between maximum total input of 8500 MW and minimum consumption of 3300 MW gives a theoretical surplus of 5200 MW. This can currently be transported away by the three 380 kV double-cable north-south routes, says ForWind.

But according to current forecasts for 2010, some 11,000 MW of wind energy, including 3600 MW offshore, will be feeding into the network. Even if conventional generation is reduced to zero in times of high winds and low consumption, ForWind argues that transmission capacity needs to be upped from today's 6200 MW to 7700 MW to take overflow power out of the area. "E.ON Netz investigations conclude that only the Ganderkesee-Diepholz route is feasible," says ForWind.

As Vorsicht-Hochspannung argues, however, wind plant do not operate at full power all of the time. Even in the unheard of event of very strong winds occurring in the summer at the same time as consumption in the area is just 3300 MW, the wind plant are extremely unlikely to produce more than 8800 MW. That would leave 700 MW of today's 6200 MW of transmission capacity free for conventional generation. More probably, wind power output would never be more than 7200 MW during periods of low summer demand, leaving 2300 MW of transmission capacity for export of other generation and energy trading.

In that case, the requirements of wind power would not seem to warrant the new cable, despite the contention of E.ON and RWE. Neither is it clear what limits would be placed on wind power's growth if the cable was not built. "To establish the precise extent to which wind energy developments would be hindered without the network expansion would require a separate study," says DENA.

Is it necessary?

Some light is shed on the real need for the cable by Windland Energieerzeugungs GmbH, a company which is independently developing a competing north-south high voltage cable route in the region (“uåX˜äŠÊ˜·³Ç, February 2005). The company's Joachim Falkenhagen points out that E.ON, which is required to buy all wind power generated by independent competitors to its own generation business, is anxious to make sure enough transmission capacity is available for its nuclear and coal generation in periods of strong winds.

Other generators are no doubt also interested in seeing transmission capacity boosted in the region. Belgian utility Electrabel is planning a new 800 MW coal station at the northern port of Wilhelmshaven, close to an existing 750 MW coal plant owned by E.ON. "Without wind energy the Ganderkesee-Diepholz link would probably not be built," says Falkenhagen.

Germany's wind industry also argues that existing transmission capacity could be better optimised, for instance by thermal monitoring to raise available transmission capacity during colder weather. That would postpone the date at which a new high-voltage route is needed. But considering the length of time it takes to gain permits for new cables, the process must start now, says Falkenhagen. Offshore wind will grow to much more than 3600 MW, if all goes to plan.

He points out that transmission cables can be operated above rated capacity to take peak surges in generation. Even though line losses are pushed up and the extra heat can shorten the life of transmission equipment, it is a better economic solution for short periods of time than not utilising available wind power.

The European Federation of Energy Traders (EFET) shares Vorsicht-Hochspannung's scepticism about a pending network capacity shortage for wind energy. EFET says network operators are "routinely underestimating the [network] capacity they could make available to market participants using existing infrastructure, and routinely overestimating how much [network] capacity must be withheld in case of outages or unusual loop flows." According to Peter Styles, chairman of EFET's electricity committee, "Instead of offering the maximum capacity, transmission system operators tend to go to the other extreme. After making the maximum number of provisions they often end up offering the minimum capacity."

Underground

If E.ON Netz' new cable really is unavoidable, Vorsicht-Hochspannung calls for it to be laid underground. An investigation instigated by the Lower Saxony rural affairs ministry into the potential costs of new overhead and underground cables reveals that overhead lines appear to be a clear winner.

The study was carried out by ForWind, which is connected to the universities of Oldenburg and Hannover. It finds that a gas-insulated transmission line (GIL) laid underground, as favoured by Vorsicht-Hochspannung, would cost EUR 323-401 million, or 4.7 to 5.4 times more than the cost of overhead cable at EUR 88.92 million, taking into account investment and operating costs, including losses, over a period of 40 years.

But Vorsicht Hochspannung is undaunted. Network expansion using underground cables would add only EUR 0.001/kWh to the price of electricity or just EUR 3.5 to the annual electricity bill of an average household, it says. ForWind's Marcel Krämer counters that higher costs could force large industrial electricity users out of the area, with negative effects on the local economy and employment.

Germany's new energy regulatory office, the Bundesnetzagentur (BNA), may not even approve expenditure on an underground cable. BNA's job is to keep network charges under control. Higher capital costs must be balanced by later economic benefits, says the BNA's Renate Hichert. "The BNA makes no value judgement on technical aspects. We only look at the efficiency of performance." So far, the BNA has not seen an application for the cable project, says Hichert.

How the BNA's remit will dovetail with Germany's renewable energy law remains to be seen. The law states that grid system operators "may add the costs of network expansion when determining the charges for use of the grid" as long as the costs are "economically reasonable," meaning that the total valuation of wind generation in the 20 years following the grid upgrade must "substantially exceed" the cost of the upgrade. While underground cable may be a more expensive option, laying the line can usually be completed faster than an overhead line, bringing more wind power on line much faster. The value of this extra wind would exceed the additional cost of putting the cable underground, say renewables experts Lorenz Jarass and Gustav Obermair, both professors at ATW Forschung in Wiesbaden.

For and against

Irrespective of the potential legal inconsistencies, ForWind's Krämer says there are a number of other issues. Among them, cable manufacturer Nexans says the around 150 kilometres of cable for the underground Ganderkesee-Diepholz route will take three to four years to manufacture, with unsightly trench work ongoing throughout that period. If GIL is used, the cable route must remain open till the project is completed to allow testing of the cable gas insulator system. It all comes at an environmental cost. "The wind sector needs to take a more differentiated view of the problems. It's too easy to simply say all cables should go underground," says Krämer.

"Ultimately, new high-voltage transmission routes are a problem for federal politics. It's unfair to place such decisions with planners in a subordinate authority of a subordinate authority of a state ministry," he says, arguing that if there is to be a change in the conventional energy generation mix, "Then infrastructures have to be altered and it makes sense to build an intelligent system."

ForWind believes the federal environment ministry should sponsor a broad study to include the views of sociologist, lawyers, technical experts and economists, in which the economics of new high voltage network are balanced against public acceptance of them.

An extra dimension was added to the controversy in late November, when BNA received a tough lesson on the cost of a failed high voltage overhead line. After heavy snow, electricity pylons in the Münster region collapsed under nearly 19 kilograms of ice per metre of cable. About 120,000 people were left without power for four days and nights. Network operator RWE is resisting claims for damage by companies and private people adding up to around EUR 100 million. The repair bill alone will cost RWE up to EUR 35 million.