By By Andrew Drwiega, International Bureau Chief | July 1, 2013
The rapid growth of offshore wind farms, particularly off the northern European coastlines bordering the United Kingdom, Denmark and Germany, is fuelling the need for more helicopters to help transport turbine engineers and other support staff out to where the energy is being generated.
The distance from the shoreline is steadily increasing too as bigger wind farms are located further offshore. While the offshore oil and gas sector is mature, and lessons are being learned and applied relating to the establishment of this similar – yet different – energy sector, the speed of development is causing experienced helicopter professionals to sound notes of caution. Peter Lloyd, global head of Environmental Protection, Health and Security with Siemens Energy Renewables, one of the companies designing and supplying wind turbines, said: “We are taking industry into dangerous territory – and it can bite us.”
He was addressing a small gathering of specialists dedicated to the provision and management of helicopters to service the growing offshore wind farm market at the Helicopters & Offshore Wind conference, organized by Haymarket Conferences, in central London during May. Lloyd, an ex-chief of staff with the UK Royal Air Force Search and Rescue (SAR) Force, is well aware of the dangers of conducting helicopter operations in potentially hazardous environments. But both aviation and maritime operations that are conducted to support offshore wind farms face their own particular difficulties. Lloyd is firmly of the view that aviation is complimentary to marine support for offshore wind farms, each being relevant depending on the task and as weather conditions dictate.
With the range to wind farms beginning to increase from the current 10-40 nautical miles out to 100 nm and beyond, Lloyd believes that the aerial support side of the wind industry is becoming more professional as more people join it who have aviation, particularly helicopter, experience. As the number of wind farms increase, so will the number of helicopters and those operating them.
The cost of a single wind turbine not generating its normal amount of power is approximately £15,000 (approximately $23,500) per day according to Graham Robb, helicopter superintendent with DONG Energy Wind Power. In areas such as the North Sea, where the weather conditions can remain bad for long periods, especially during the winter months, this can rapidly lead to a significant loss of revenue in a short period of time.
Figures provided by Robb indicated that during the period October through March 2011-2012, offshore wind turbines in some areas of the North Sea were not accessible 49 percent of the time. Although access during the summer improved, this meant that overall the turbines could not be accessed by sea for one third of the year. In December 2011, one of the Horns Reef wind farms was only accessible by sea for two days. The potential for helicopters to increase accessibility has not been overlooked.
The general consensus in the offshore wind energy sector industry is that support to the wind farm fields is best conducted by a mix of maritime vessel transfer and helicopter hoist operations. Robb said that the deciding factor on which mode of transport to use was dependent on wave height verses weather limitations. While maritime transfer of engineers and equipment is cheaper, the physical act of landing personnel on wind towers is restricted by the choppiness of the sea decided by wave height. There is also the factor of crews getting seasick due to rough seas during transit times in boats. With helicopter flying times substantially less than a boat trip, there is less chance of airsickness occurring and winching operations can be carried out in fairly windy conditions.
The current maritime transfer restriction is usually reached when wave swells reach around 5 feet (1.5 meters), although this may rise to 6.5 feet (2 meters) when new technological improvements to boat stability are introduced, and there are several companies currently looking at new designs.
Trying to forecast the need for helicopters, Robb explained that at DONG Energy all future substations serving offshore wind farms will have helicopter landing platforms. Further, he said that the potential of basing helicopters offshore was something that was currently being examined. This would mean that they could be housed in hangars and be able to refuel in order to maximize their stay offshore. Crews would also have accommodation.
Helicopters naturally also have their limitations. Conditions that hinder their operations include when visibility falls below 3 km, the cloud base is less than 600 feet, or the wind rises above 60 knots. Bernd Brucherseifer, managing director of HTM (Helicopter Travel Munich) said his company picked up its first wind farm contract for the Alpha Venus offshore wind farm in 2009. A string of successful contract wins have followed, resulting in an increase in the number of helicopters HTM operates in support of offshore wind farms to 16 (14 of which are Eurocopter variants). With one of the contracts, to the Global Tech 1 field, the distance to shore is 72 miles. “For that mission we are probably out all day including trips back to land to refuel,” he said.
Brucherseifer explained that operators must consider multiple factors when deciding on a helicopter for offshore wind farm operations: One Engine Inoperative (OEI) performance; rotor diameter (very important as explained later); downwash, limitations of type; inspection levels and a good time between overhauls performance (which can be between 25-100 hours).
The rotor diameter is an important factor in helicopter type selection. Robb said that there was no “level playing field” in the heli-hoist operation concerning the type of helicopter and type of turbine, as the rotor radius of some helicopters could come too close to the line of the turbine blade relative to where the heli-hoist maintenance platform was situated.
Related: Offshore News