The announcement of the retrofit comes after a number of mechanical setbacks have prevented the Eemsmond wind plant from consistently achieving its targeted production of 73 million kWh a year since its expansion in May 1996. Problems at the site first became evident shortly after 94 variable speed turbines from now bankrupt California company Kenetech -- amounting to 38 MW of installed capacity -- were added to 40 Danish Micon units already on site to create what was at the time said to be Europe's largest wind plant.
Officially opened the day after 5% stakeholder Kenetech sought bankruptcy protection in the US, EDON was optimistic that Kenetech's Chapter 11 application would present no problems in terms of financing or maintenance of the project. But the failure of two blades on the Kenetech units during storms in summer 1996 proved this optimism to be ill-founded.
Analysis at Holland's National Air and Spacecraft Laboratory showed the breakage was due to a construction fault which is likely to have affected all the rotors manufactured by Kenetech's supplier, TPI Inc of Rhode Island. Consequently, all 94 of the 360 kW turbines have had to be shut down at high wind speeds and during maintenance work despite theoretically being designed to withstand wind speeds of up to 200 kilometres an hour.
Early hopes that the blades could be repaired eventually proved unrealistic and according to EDON's Dick Honnef the contract for replacing the TPI rotors has now been awarded to Dutch company Aerpac BV. It will be refitting the plant with specially designed blades.
Further problems with the wind farm's Kenetech machines came to light last summer when a routine inspection by the Waterschap, the authorities charged with the maintenance of Holland's dike system, revealed that the gear boxes on a number of turbines were leaking oil (Windpower Monthly March, 1998). Initially it was thought that only the 19 units situated on the sea wall were affected but further inspection showed the problem to be more widespread. EDON has subsequently repaired the damage to the asphalt covering of the dike and believes the replacement of the affected gear boxes will prevent further leaks.
The retrofit program will be carried out by EDON engineers and will begin in September. It is expected to be completed by Spring 1999. The cost of refitting the NLG 80 million project has not been disclosed, but the Zwolle-based utility still hopes to recover some of the amount from Kenetech. EDON is a member of the international user's group currently pursuing claims against Kenetech in the American courts.