Helicopter operators and manufacturers are seeing offshore wind turbine maintenance as the next growth opportunity, as wind farms are developing quickly around Northern Europe countries.
Such turbines need regular servicing and their numbers are increasing, according to information provided at a conference at Helitech 2011 in Duxford, UK. However, the increased number of turbines has yet to translate into significant business for either operators or manufacturers.
According to the European wind energy association, 101 new offshore windmills were connected to the power grids in the UK, Germany and Norway during the first six months of this year. As of June 30, there were 1,247 offshore wind turbines fully grid connected in 49 wind farms in nine European countries. So far, the UK and Denmark have the lion’s share, with a combined 74 percent of the installed power, said Anne-Bénédicte Genachte, regulatory affairs advisor with the European wind energy association.
Europe forecasts that it will have turbines generating 40 gigawatts installed offshore in 2020; that translates to thousands of turbines, as recently built wind turbines average 3.4 megawatts. The Dogger Bank wind farm alone, in the North Sea, will encompass approximately 1,600 turbines when complete. One turbine requires five to 10 visits per year (scheduled maintenance and repairs), and the helicopter operators and manufacturers see significant potential there.
The offshore wind farm market is “huge,” according to Eurocopter UK CEO Markus Steinke. Some offshore oil-and-gas helicopter operators already have plans with hub-and-spoke schemes to bring workers to destination. A 20-seat-or-so helicopter would fly from the coast to an offshore heliport. From there, lighter aircraft would bring technicians to the wind turbines. Steinke, however, foresees a mere 20 helicopters flying wind farm missions in the UK in 2020.
Ship-based Operations
The discrepancy lies in the fact that not all visits to the wind turbines will be performed by helicopter, as ships are used for the same purpose. Peter Lloyd, head of environmental, health and safety strategy at energy specialist Siemens, sees these vehicles as complementary because of their discrete advantages in varied weather conditions. A ship can drop off personnel at a wind turbine's “downstairs door” in relatively poor visibility, but it needs a calm sea (five-foot sea state maximum) and, therefore, moderate wind.
A helicopter, on the other hand, requires good visibility but can cope with stronger winds to hoist a technician down to the upper platform. For example, Unifly drops personnel off at wind speeds up to 40 knots. The Denmark-based operator flies from Esbjerg Airport to the Horns Rev I offshore wind farm. The Eurocopter EC135 hovers some 260 feet above sea level.
Lloyd pointed out that helicopter transport to a turbine offers productivity advantages. “One day of revenue from one turbine can buy you four to six flight hours,” he said. Scott Butler, commercial manager with Bristow, concurred, noting that, over a contract life, the helicopter will ensure more passenger movements. As for safety, “15,000 hoisting cycles have been performed without any accident reported,” Lloyd added.
So how does a helicopter approach a wind turbine platform? The target is the drop-off area located opposite the blade’s hub, at the top of the mast. The wind turbine is first stopped. The blades are feathered and locked in a “Y” position. They are placed so that the hub’s axis is perpendicular to the wind’s direction. As a result, the nacelle holding the drop-off area is perpendicular to the wind, too. Therefore, the helicopter can approach into the wind and is not affected by the blades’ turbulence.
What about rescue (one construction worker was recently rescued from a wind turbine)? Fresh from a training exercise at the Gunfleet Sands wind farm, Flight Lieutenant Lee Turner and Master Aircrew Chris Bodiam from the RAF’s UK SAR Force gave delegates an insight into their experience of wind farm rescue techniques. They emphasized that hazard to aircraft includes turbulence from other wind turbines. “It would be a good idea to stop the turbines upwind as well,” they said. For the winchman, the confined area can make casualty handling a highly skilled procedure, particularly if a stretcher is needed, Bodiam said.
