A high-yield turbine for low-wind locations
October 5, 2011 by Windpower Engineering
Filed under Editorial, Turbine Design
The N117/2400 from Nordex is the most recent addition to the company’s Gamma Generation of turbines. The model is intended for light-wind sites, creating power generating potential for previously nonviable locations across the nation.
A glimpse inside the N117, shows the turbine’s components.
The company says that with a 2.4-MW max output, a 117-m rotor diameter, and a rotor sweep of 10,715 m2 (almost 3,000 m2 more than previous models), the N117 is the highest-yielding IEC 3 turbine in its class. It will reach a capacity of over 3,500 full-load hours at a typical site, outperforming other IEC 3 turbines by up to 20%. This translates into a capacity factor of 40%. Furthermore, the N117 has 58.5-m rotor blades, the largest turbine in its category. The manufacturer has kept the blade profile and connection system the same as previous models (the N80, N90, and N100) and geared the rotor dimensions to the requirements of lower wind locations. Carbon fiber-reinforced plastic also ensures the blade’s structural stability.
The N117’s 2.4-MW max output, along with its large rotor diameter and swept area, make it a high-yielding turbine even in light-wind locations.
Attractive wind locations can be close to residential areas. Thus, the turbine’s acoustic power level is limited to a maximum of 105 decibels, allowing use closer to residential areas, as well as optimal turbine layout at wind farms. Also, the model’s hub height on a standard 91-m tubular steel tower totals 150-m, which remains below the 500-ft FAA threshold.
The turbine also features a combined spur and planetary gearbox that turns a 660-V, double-fed asynchronous generator with a liquid and air cooling system. The N117 is PLC controlled and also has a remote-controlled surveillance system. Grid connection is via IGBT converter.
Manufacturing the N117 will begin in July 2012 at Nordex’s U.S. plant in Jonesboro, Arkansas—which opened in October 2010. All of the company’s turbines made in the U.S. contain more than 75% domestic content.
“The N117 will help increase America’s total wind potential by turning many light wind sites into viable power-producing locations,” says Ralf Sigrist, president and CEO of Nordex USA. “That means another step forward in making wind energy a highly competitive alternative even for light wind speed locations.”
WPE
A Turbine that Supports the Grid
July 21, 2011 by Windpower Engineering
Filed under Editorial, Turbine Design
Demand is increasing for reliable turbines with network compatibility and quality power. One turbine manufacturer has incorporated these elements into a recent model. DeWind says it has built on its 2-MW series since 2002, and its latest 2-MW D9.2 is especially grid friendly.
Just as its predecessor, the D8.2 introduced in 2006, the company says the D9.2 boasts a reliable drivetrain that offers excellent grid support and power with increased conversion efficiency through its larger 93-m rotor. The turbine also uses a fixed-speed synchronous generator. In combination with blade and rotor design, the generator provides high-quality power while eliminating the need for a converter or power electronics at the point of interconnect.
By nature of their design, power converters are expensive. To minimize cost, they are designed with small tolerances to overheating that occurs each time a system is required to operate outside of its tolerances. Thus, converters shut down when the grid becomes unstable and outside of its tolerances. Hence, wind farms are required to provide additional compensation devices at the point of interconnect—adding cost to the project—to account for converter-based turbines’ inability to deal with grid instability.
However, DeWind says the D9.2’s design not only operates through grid instability, but also provides dynamic reactive power to support the grid through extreme events. What’s more, because the generator works at high voltage, it can connect to the grid directly through a synchronizing switch without power conversion electronics, converters, or a main power transformer.
The efficiency of a variable-speed blade rotor with the power quality of fixed-speed synchronous generation is possible through a hydraulic torque converter, the WinDrive, supplied by Voith Turbo. The WinDrive converts variable-speed input to constant speed output for the fixed-speed generator, and is a hydraulic couple between the generator and a two-stage planetary gearbox. The coupling dampens excessive forces, such as strong wind gusts, creating a more reliable drivetrain. The converter is based on technology that has been applied successfully in many different industries for over 50 years.
Combining fixed-speed synchronous generation, the work horse of traditional power generation, and the WinDrive with a mean-time-between-failures over 39 years produces a drivetrain with high availability. The durability of the turbine is evident through its successful operation at high elevations. For example, since 2008, a D8.2 turbine installed at an elevation over 4,100m has been generating electricity at a mine site near Veladero, Argentina.
Furthermore, the turbine manages noise emissions using customer-defined criteria, such as wind direction, wind speed, or time of day. The control system works with the turbine active power management system to maximize energy production while complying with local noise codes.
WPE
Direct drive needs only half the parts of conventional wind turbines
October 4, 2010 by Paul Dvorak
Filed under Turbine Design
The illustration shows some of the equipment inside the Siemens 3.0 101 DD. The red mechanism at the top is a crane to assist with heavy items.
You get the impression that wind-turbine OEMs are shying away from designs that use gearboxes. Take the Siemens SWT-3.0-101 DD for instance. The company eliminated its gearbox and in the process eliminated about half the parts needed for a similarly sized gear-driven turbine. The 3-MW unit works with a 101-m dia. rotor with blades made in one piece. The nacelle is smaller and lighter than previous designs, which simplifies transportation. For those technical feats, the Siemens SWT-3.0-101 DD is our Turbine of the Month. The prototype, near the company’s wind power headquarters in Denmark, was tested and validated before the design launched for sale this year.
“Compared to a conventional gear-driven wind turbine, we managed to reduce by half the number of parts in the SWT-3.0-101,” says Siemens Wind Power CTO Henrik Stiesdal. “With fewer moving parts, the direct-drive design has potential to significantly reduce maintenance, which could result in higher turbine availability.” The machine will be targeted for onshore and offshore markets.
“This direct-drive turbine is also lighter than its geared counterparts. The nacelle of a 3.0 MW direct-drive turbine is 12 tons lighter than the nacelle of a 2.3 MW geared turbine with the same rotor diameter,” says Stiesdal. “This is important for transportation and installation.”
The turbine features a compact synchronous generator excited by permanent magnets. The advantage of PM
The recent SWT-3.0-101 uses many tested components from previous designs.
generators is a simple design that requires no excitation power, slip rings, or excitation controls. This leads to high efficiency even at low loads. The company installed the first of two 3.6-MW direct-drive turbines in 2008 to assess the drive technology’s competitiveness with geared machines. “We concluded that the concept machines are operating well and we should proceed with a commercially competitive product,” he adds.
Siemens says the generator is completely new. With fewer than half the number of moving parts of an induction generator, the new design is easy to maintain and reliable. The compact size avoids specialized transports that larger nacelles often require.
The nacelle, 6.8-m long and 4.2-m dia., weighs 73 tons. This is “light” enough to be carried on trucks available in most markets. The dimensions of the new wind turbine allow for greater flexibility in road transportation. For instance, key bridge and tunnel clearances were considered when designing the turbine. An advantage of the new nacelle size is that transporting it in one piece minimizes expensive and risky on-site assembly of critical components.
Eliminating the gearbox reduces complexity, and increases reliability. Unlike electrically excited machines (induction generators) with a gearbox, a PM excited generator expends no energy for the excitation needed to generate electrical fields. Furthermore, the SWT-3.0-101 generator uses an outer rotor that spins around the internal stator. This design leads to the smallest possible diameter, which aids in reducing nacelle dimensions. It also allows for rigid support of the stator, which allows manufacturing to narrow air-gap tolerances and thereby high generator efficiency.
Despite the smaller nacelle, the turbine gives service technicians more space for their work. The part reduction gets credit for the extra space and making key components readily accessible. The “plug and play” design for most components allows swapping them out without affecting other components.
The SWT-3.0-101 is liquid cooled. Coolant temperature is regulated with a top-mounted, passive cooling system, avoiding high-power fans and thereby improving energy efficiency.
Of the five key wind turbine components – blade, rotor hub, nacelle, tower, and controller – all but the nacelle, come from existing company designs. Using proven components lets the company eliminate many variables traditionally associated with the introduction of a new product.
Grid-stability requirements grow as more wind power is fed into it. The company says its electrical equipment (NetConverter) efficiently decouples generator and turbine dynamics from the grid. The converter is said to offer good flexibility in the turbine’s response to voltage and frequency control, fault ride-through, and output adjustments. As a result, company turbines can be configured to comply with a variety of relevant grid codes in major markets and can be readily connected to the grid. Lightning protection is based on the IEC 61400-24 Lightning Protection Level I.
The rotors of the SWT-3.0-101 are manufactured using the company’s patented process. The blades are made in one piece from fiberglass reinforced epoxy resin in a single production step. As a result, there are no glue joints, which minimizes environmental effects on the blade. WPE
4-MW direct drive headed offshore
August 7, 2010 by KRemington
Filed under Wind Power News
A quick scan of recent news shows that U.S. coastal waters are the next big development area for wind plants. It makes sense to put the largest practical units in the steady winds offshore. GE, for one, says it will apply its experience to the offshore wind industry as it matures, growing from a 1.5 GW installed based in 2008 to a forecasted 30-GW opportunity by 2020. So for having the right turbine at the right time – as the offshore market blooms – the GE 4.0-110 turbine is our Turbine of the Month.
The company says its 4.0 MW wind series platform removes the single most costly failure in turbines, gearboxes, and replaces it with a reliable slow speed generator. GE is able to add this turbine to its portfolio of machines because it bought the developer, Norway’s ScanWind, in September 2009.
A few technical features of the 4.0 MW unit include about a 6-m diameter permanent magnet generator the company says delivers high efficiency at low wind speed. At just 10 rpm, magnets at the rotor tip will be moving at about 188 m/min. The generator’s 20 sections or modules allow replacing a portion of it without a complete removal of the 90-ton unit. Two main bearings transfer axial and bending loads from rotor to bedplate for higher reliability. The unit also sports continuous close-wind tracking to capture more energy. Also important are what it does not have: No yaw brakes or hydraulics.
Through development, installation, and operation of Ireland’s Arklow wind farm, GE has more than six years of experience and an understanding of what it takes to deliver and operate offshore wind turbines. In 2005, 13 direct-drive wind turbines using the same design principles were installed along Norway’s coast. GE reports that the turbines have since accumulated 50 years of equivalent operating experience under some of the most challenging conditions nature can whip up: Salt spray, storms and lightning, winds averaging 9.7 m/s, and temperatures from –25°C to +25°C.
The 4.0 turbine boasts of several maintenance and safety advantages thanks to a spacious nacelle and internal-hub access which means not having to exit the nacelle to access machinery in the hub. The design also offers redundant operation, automatic lubrication, and in–situ repairs wherever possible to maximize unit availability and reduce operating costs.
Lastly, the blades on the 4.0 MW turbines, made partially with carbon fiber, are of the company’s proprietary design. They twist in high wind to soften the impact of gusts, while their airfoil is shaped to increase torque. WPE
Four Onboard Generators Mean Almost Never Having to Shut Down
October 23, 2009 by Windpower Engineering
Filed under Featured Wind Power Articles, Turbine Design
The Liberty 2.5 MW wind turbine from Clipper Windpower, Carpenteria, Calif., is Windpower Engineering’s first Turbine of the Month because its unusual engineering features address common industry headaches, most of them in unscheduled maintenance. Downtime often comes from gearbox stresses, swapping out large components, and unscheduled crane call-outs. The company’s Quantum Drive distributed drive train is a two-stage helical, load-splitting gearbox, with four (yes, four) separate permanent-magnet synchronous generators, and controls for variable-speed operation with power conversion.
In the Liberty, Clipper engineers uses a compact, two-stage helical, distributed load powertrain for higher efficiency than that provided by three-stage designs. Also, the company uses four smaller high-speed shafts to distribute torque to the four generators, thereby reducing potential for premature bearing failure and decreasing the time and cost associated with generator service and repair.
The permanent magnet generators are said to have advantages over induction generators in terms of increased power density, and increased efficiencies at lower wind speeds. The four-generator configuration and control lets the turbine continue operating even with one or more generators are removed for repair. The small, compact generators can be replaced using an onboard hoist instead of an expensive ground-based crane. Two IP54 cooling configurations, one water-to-air and the other air-to-air cooling, offer arrangements for mild or harsh operating environments. Effective generator cooling maintains temperature at less than Class F rise under all conditions. Lower operating temperature provides for increased reliability, and longer life due to a greater thermal margin.
The company adds that two pre-loaded, low-speed taper-roller main bearings absorb thrust loads and mitigate problematic axial motion and main-shaft misalignment associated with low-speed bearing failures. In addition, high-speed gear sets are in “cartridge” form so maintenance personnel can replace gear sets using the onboard hoist without removing the gearbox. This removes more need for ground-based cranes.
In addition, the design uses no slip rings or brushes. Historically, these have been a maintenance issue requiring replacement more frequently than anticipated.
There are no moving parts on the rotor in the rotating frame, thus eliminating the need for complex replacements of brushes, rotating rectifiers, and exciters typical found in doubly-fed generators.
Lastly, the design’s variable speed generator and inverter completely decouples the generator from the grid, eliminating grid induced drivetrain torque excursions. The company says it designed the Liberty turbine in partnership with the U.S. Department of Energy and its National Renewable Energy Lab, which provided development funding and support for drivetrain and blade testing. The DOE awarded the company an ‘Outstanding Research and Development Partnership Award’ in 2007.
