Nowadays, the trend is towards offshore stations, as good sites both inland and onshore are becoming rare, local protests must be reckoned with, and increasingly larger windpower stations are becoming viable marketwise.

Yields greater by 40 to 100 per cent argue in favour of using windpower at sea. An offshore station can work up to 3,500 hours at full load as contrasted with 2,000 hours inland. Thus, correspondingly more can be harvested at sea. The technically usable potential for Germany is estimated at over 200 terawatt hours — or half of the present electricity consumption. The maximum size of the rotors already installed or under development is between diameters of 80 and 110 metres, with a rated output of 2.5 to 5 megawatts and with a hub height of up to 100 metres. However the costs for offshore stations are higher due to:

• expensive foundation work
  
• distance to nearest high-voltage transmission unit involving a considerable cost outlay and line power losses
  
• complicated maintenance and repair
  
• the necessity for floating cranes.
  
  

In cases of unfavourable weather, stations may be inaccessible for extended periods of time. It is generally assumed that these additional costs can be compensated for by the higher energy yield from offshore.

Assuming a suitably constructed and dimensioned bridge is available, it could help to avoid such additional costs. because:

• No foundations need be constructed; the horizontal forces exerted on pylons by the wind via large rotors can be absorbed instead from small to medium-sized rotors by the bridge structure (including, for example, the 30 m wide road surface of the motorway)
  
• Rotors of smaller size can be arranged on and below the bridge
  
• The wind power stations can be located immediately adjacent to the high- voltage lines running underneath the bridge
  
• Maintenance and repair of the units on and under a bridge is easier and more economic than out at sea.
  

The bridge over the English Channel proposed by Friedman and Schulze-Fielitz in 1963 as a competitive alternative to the Eurotunnel is here a good example.

Thanks to the extremely favourable wind conditions, for example in the English Channel (prevailing winds from the SW, high wind velocities, greater height of the rotors working at up to 3,500 hours at full load), it would be possible, depending on the arrangement and size of the wind power units, to install 1,500 — 3,500 MW along the 35 km bridge, i.e. the amount of energy consumed by up to 3 million households or 12 million inhabitants, an investment of approx. 7 milliard DM (current Euro value).