|Introduced in 2014, GE’s five-legged Space Frame Tower is covered by a plastic fabric. Photo courtesy GE.|
Leading wind turbine and components suppliers, specialized service providers and inventors gathered at Windpower 2014.
By Eize de Vries, Contributing Editor
Thousands of wind power professionals descended on Las Vegas in May to check out Windpower 2014, the annual wind energy conference and expo put on by the American Wind Energy Association. The expo hall was filled with both large and small wind companies showcasing the technologies, products and services that will help bring more clean energy to the U.S. and the rest of the world.
GE Unveils new Turbine Technologies
One of the innovative solutions GE presented in Las Vegas was its “blade extension,” a dedicated solution for 1.5-MW SLE turbines offering a rotor diameter increase from an initial 77 meters to 91 meters. To begin the process, the original 37-meter blades are cut in half roughly in the middle. Next, the blade halves are re-joined but with a seven-meter insert incorporated into them. The complete cutting, extension and re-joining process was shown on video but in highly accelerated mode and with the most critical steps and especially the actual joints and two joining areas blurred.
Between 2007 and 2008 GE installed about 9,000 SLE-series turbines across the U.S. and all were put atop 80-meter tubular steel towers. According a GE spokesperson, a 77-meter rotor was that time the only standard size available, including for turbines operating at poor wind sites with only 5.5 -6.0m/s average wind speeds. The turbine blade modification increases the rotor swept area by 40 percent, which the company claims increases annual energy production by more than 20 percent under wind speed conditions mentioned above.
GE said that the solution comes with built-in advanced controls offering substantial load mitigation benefits. Two prototypes fitted with the blade extension feature have been in operation since June 2013 at sites in the U.S. The SLE-series rotor enlargement does not take place simultaneously with hub height increases, and this could potentially become an issue at low-wind sites hampered by high wind shear.
GE also announced an expansion of its “brilliant” platform with a new 2.2-MW turbine plus integrated wind farm wake management software for reduced wake loss and optimized mechanical turbines loads. Noteworthy, the 2.2-MW turbine builds on GE’s 1.5-MW series and is not a de-rated 2.5-MW platform. With this new 2-MW+ turbine model introduction the original platform split between ‘1.X’ (up to 2 MW) and ‘2.X’ (from 2 MW) is no longer valid according GE. The company’s current evolutionary product development strategy focuses on migrating to new 1-2 MW and 2-3 MW turbine class portfolios. With regard to performance and operating economics, the 2.2-MW offers a 12 percent increase in capacity factor and 33 percent higher yield, according to GE. The figures should be compared to the current 1.85-82.5 model, which is geared towards Brazil’s Class II wind regime.
Wind farm wake management software improves output at the plant level through turbine-to-turbine communication, harmonizing wind farms with more than 20 turbines to achieve greater output as a single, efficient plant. With the initial applications, customers can expect to see 5 to 10 percent reduced wake loss and improved mechanical loads due to lower wake turbulence, said GE.
|TenderLand Renewables’ wind turbine refurbishment process. Photo Courtesy TenderLand Renewables|
Upgrades to Existing Turbine Technology
Refurbished and redesigned/upgraded kW class turbines, often fitted with a new modern control system and of which the original design is sometimes more than 25 years old, continue to serve a wind market niche. California–based Tenderland Renewables is one of these market players and at Windpower 2014, the company displayed an “open” nacelle of a refurbished 160-kW Danwind 23E, a classic Danish turbine but with an unusual geared drivetrain layout.
Turbine lifecycle extension as a theme is closely interlinked with keeping second-hand turbines running, and it enjoys increasing wind industry recognition. Gamesa of Spain is one of the main pioneers in this area. A company expert explained that the trend is reinforced by the fact that it is often not possible to exchange old turbines with bigger more modern equivalents because of permitting and other reasons. Planning a product lifetime extension from, for instance 20 to 25 years or longer should be prepared well in advance, he added. Because product lifetime extension is a dedicated process it also incorporates careful analysis and ongoing monitoring of a turbine’s condition. This careful analysis can indicate that a given turbine component such as the gearbox of a specific model has suffered premature failure. It is then possible to either bring back the failed component to original factory specifications (100 percent) or alternatively recondition and redesign/modify to a higher specification level by systematically incorporating design improvements.
Small Turbine Offerings
Regarding small turbine offerings up to 100 kW, the number of suppliers is rather limited. Chinese company Hummer displayed some nacelles in Las Vegas. The models are available in power ratings up to 100 kW and a shared key product characteristic is a permanent magnet type direct drive generator mounted in front of the rotor hub.
On a much smaller overall scale was the U.S. Department of Energy Collegiate Wind Competition for undergraduate students teams from ten different colleges and multiple engineering and other disciplines. Each individual team had to design, build, and test a micro-wind turbine capable of performing according to a customized, market data-derived business plan. For testing each turbine’s individual performance, a wind tunnel was brought to Las Vegas. This year the competition was focused on creating a lightweight, transportable wind turbine that could be used to power small electronic devices. Pennsylvania State University was crowned the winner with a three-bladed horizontal-axis design, but the various teams displayed a rich variety in solutions using rather unusual concepts.
One such unusual design was a vertical-axis Darrieus-type turbine with a Savonius rotor incorporated inside the main rotor, which was aimed at providing self-starting capability to the system.
It was also interesting to note that several teams had taken advantage of the increasingly popular 3D printing trend, making their blades and/or other components with this new technology.
High towers continue to be an onshore wind industry main focus. In Europe, concrete-steel hybrid towers with hub heights in excess of 140 meters have become a popular offering in several key markets including Germany, Austria and Finland. At least two companies – Siemens and Lagerwey – have developed alternative bolted steel towers.
Earlier this year, GE introduced a five-legged Space Frame Tower, with a current largest 139-meter hub height for the latest 2.75-120 model. A company expert stressed that the tower architecture is not limited to 140 meters. Unusual is that the lattice type Space Frame Tower structure is covered by plastic fabric. A renowned German tower expert within this context commented that high towers are large landscape dominant objects and a basic requirement for each (high) tower solution then is a visually pleasing overall design.
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