Monitoring of the condition of rotor blades is performed visually by experts every one to two years, but it is very subjective and superficial. As is common in energy facilities, the increases in stress resulting from greater blade size, coupled with the rising prices for rotor blades, call for a new approach. The continuous monitoring of the status of highly stressed parts offers preventative maintenance as well as troubleshooting of existing problems.

Satellites orbiting and observing Earth offer potential for the offshore wind farm industry. Of particular interest are the images from the Synthetic Aperture Radars (SAR) on board satellites belonging to the European Space Agency (ESA): the satellites ERS-1 and ERS-2 from 1992 to present and Envisat from 2002 to present. In the April/May 2005 issue of Windtech International we published an article about this topic. The current article describes more specific issues concerning offshore wind farms.

Coupling an energy storage facility with a wind farm can improve that wind farm’s interaction with the power grid. This can be crucial, as recent estimates put the cost of integrating wind energy into the grid at 5 to 30% of the cost of generation. Energy storage can benefit wind power in many ways, including providing a balancing function for a rapidly changing load and wind output, smoothing the ramp rates so the power flows are more gradual, and providing reliable, firm output from the wind farm at any time. Sizing and choosing the correct storage technology and operational profile depends upon a number of factors – one size does not fit all.

By Richard Baxter, Senior Technology Analyst, Ardour Capital Investments, USA

Design Considerations and Approaches

In the pursuit to increase the megawatts per surface area and to maximise the megawatts/hour output per project dollar the size of wind turbines has been increasing steadily. To capture the higher winds and to accommodate the larger rotor diameter the hub heights have also been steadily increasing. Wind park prospectors and promoters are now required to measure at greater heights than ever before. From 40 to 50 then to 60 metres, the minimum level now seems to be the 80-metre level. The traditional tubular anemometric masts have not been able to go beyond the 60-metre level without becoming inordinately heavy. However, by revisiting the 250-year old Euler column equations and by using the aircraft design approach, a new lightweight structure is now able to achieve the 80-metre measurement at a fraction of the cost of the traditional lattice tower.

Global component shortages, rising project costs and the risks of ‘offshore’ have hampered a much-anticipated Pan-European offshore wind market. These market inhibitors have provided a reality check for the industry and have stalled plans for new offshore entrants. Meanwhile the US offshore market, which does have some high profile projects in the works, has yet to take off and the Asia Pacific market is still years away from large-scale offshore development.