Test field death of turbine technician
An accident at the Kaiser-Wilhelm-Koog wind turbine testing facility in Germany resulted in the death of a technician on April 3 and the complete destruction of a wind turbine which ran out of control during a squall. The dead man was Bernhard Saxen, 42, an employee of the wind turbine's manufacturer, Husumer Schiffswerft (HSW).
Saxen was one of four technicians working on the prototype 600 kW machine when the 19 tonne nacelle and 11 tonne rotor toppled 55 metres to the ground, damaging the tower in the process. He was in the upper section of the tower at the time, under the azimuth bearing. Although suffering visible head injuries he managed to climb to the ground, but died later in hospital having been taken there by ambulance.
At the request of the public prosecutor in Itzehoe, an account of the accident and evaluation of the turbine computer records was drawn up by insurance company Allianz Versicherung and certification company Germanischer Lloyd (GL), both based in Hamburg. This report was presented on April 17, says Bernhard Richter from GL. He declines to give details on possible causes of the accident until the public prosecutor releases the report, but rules out gross negligence or malicious intent. Richter is also managing director of Windtest Kaiser-Wilhelm-Koog. He says no Windtest staff were present at the time of the accident.
The 600 kW prototype, with a newly developed active stall control system, was designed by German wind consultancy Aerodyn Energiesysteme of Rendsburg and built by HSW at Husum, says Christian Schult of HSW. He is the appointed spokesman on the accident for both HSW and Aerodyn. With a rotor diameter of 48 metres, the turbine was designed for use in low wind speed areas. According to Richter the prototype was installed on March 6. Power was first generated on April 1.
On the day of the accident various tests, including shutting down the turbine at nominal wind speeds, were being carried out by the four technicians, two from HSW, one from Aerodyn and the fourth from SSB of Salzbergen, which produced the hardware for the active stall control, says Richter. Wind speeds were 10-16 m/s.
Before the accident occurred the machine had been running for about an hour in normal operation, says Schult. At the time of the accident at about six o'clock in the evening, with the machine running in normal operation, Saxen had climbed the tower for a last check inside the nacelle when a squall blew in. The first suddent gust was measured at over 33 m/s by testfield anemometers.
The HSW wind turbine's safety systems registered the gust and the mechanical brake was activated. The blades are not equipped with air brakes at the tip, confirms their manufacturer, Abeking und Rasmussen. Considerable wear on the mechanical brake was later evident, Richter says. The turbine sped out of control and fell apart. It is not clear exactly how the HSW technician was injured, says Richter. He may have been hit by parts falling into the tower. Saxen, from the village of Hattstedt near Husum, leaves a wife and four children. He had worked in the wind energy department at HSW for seven years. A report on the accident was due late last month.
HSW had planned to install 12 of the HSW 600 kW turbines at a site in Mecklenburg-Vorpommern in the autumn. "There will now clearly be delays in delivering the machines, so whether the project will be realised with HSW machines depends on whether the owner company can wait," admits Winfried Gerold from HSW. The company stresses, however, that it will be proceeding with the design, making modifications if necessary.