The cost of electricity from utility-scale wind turbines has dropped by more than 80% over the last 25 years. When the first commercial turbines were installed in the early 1980s, electricity cost as much as $0.30/kWh. Today, commercial wind farms can generate power for less than $0.05/kWh.
The cost to install a commercial wind turbine depends on several variables. Construction and installation costs make up the bulk of the initial capital investment and can ultimately dictate the cost of electricity generated from the turbines. Most commercial-scale turbines installed in the U.S. now have 2-MW nameplates and cost roughly $3.5 million installed. A major portion of that cost is installation, namely setting the tower sections, nacelle, and rotor in place with a crane.
Today in the U.S.
Wind farms on New England ridgelines are likely to be smaller and cost more to install than turbines on the flat terrain of the Northern Plains states. Maine turbines will also experience slower winds. So, while wind power may cost less than $0.05/kWh in the Northern Plains, it may cost $0.06 to $0.07/kWh in New England.
Turbines in the U.S. and Europe are significantly larger than a few years ago. Consequently, contractors and crane rental companies are demanding lifting equipment that does not significantly add to the cost of installation.
Current and future lifting equipment must balance lifting capability with cost effectiveness. Simply using a higher capacity crane isn’t always a best solution for installing larger wind turbines. A larger crane changes the economics of turbine installation and can make the project less attractive to potential investors.
The company recently introduced a special attachment for the Manitowoc 16000, its 440-ton capacity crawler crane. The attachment boosts capacity by 49%, letting it install most makes and models of wind turbines currently in the U.S. The attachment uses existing boom rigging in a new configuration to significantly enhance capacity when working at short radii. Unlike other cranes suited to lifting larger wind turbines, the attachment does not require longer fixed structures such as luffing jibs.
Wind turbines are erected in windy locations, so cranes working with longer jibs, for safety reasons, have a lower cut-off wind speed than cranes working with just a boom and boom tip. That means a crane with a longer jib will have fewer working days than a more weather–tolerant design.
Today in Europe
There is a strong commitment to renewable energy in Europe, especially wind power. The European Union has set targets to increase its share of wind generated power over the next ten years. For instance, Sweden has set a requirement to increase its renewable wind power energy by 20%. This means adding 5,000 to 6,000 MW of capacity to that country alone.
As in the U.S., the average turbine, once smaller than a megawatt, has grown over the last several years to 2.5 MW max output. Hub heights have also increased from about 60 to 70 m, to over 100 m, now the standard hub height for wind turbines in Europe. It is reasonable to expect turbine OEMs to continue building larger machines during the next three to five years. Several 10 MW units are in advanced planning.
In the near future, the commodity turbine will have a 3-MW output and average hub heights of 105 to 125 m. In some instances, hub heights will soar to 160m which is possible with longer booms. Cranes, some from Manitowoc, already place turbines at 105-m heights. The tradeoff is that at such a height, they lift less. Hence, turbine equipment must be erected in more sections or modules which take longer and cost more.
Research shows that increasing hub height increases output. According to one study, increasing hub heights from 70 to 125 m increases turbine output by 59%. Hub heights bumped from 90 to 125 m provide a 26% increase. And if it were possible to boost heights from 90 to 160 m, output would jump by 45%.
The Grove GTK1100 from Manitowoc is a novel and cost-saving crane for wind installations in Europe and Asia. It can lift up to 95 tons to heights of 108 m, and at radii of up to 14 m. The design is a new concept for applications, such as wind turbine erection. It was launched in 2007 with units in Europe, South Africa, and China. The issue in the U.S. is its high axle loading during transport which keeps it off U.S. roads.
Its design includes a wheeled mobile carrier with a telescopic mast and a luffing telescopic boom at its top. The crane’s design maximizes lifting capacity, while offering a lower cost of operation when compared to other options.
The crane has advantages over other types of lifting equipment. For instance, it requires little room to erect and transports with as few as five trailers, while up to 25 trailers are required for cranes with similar capabilities.
The company based the GTK1100’s main carrier around a standard semi-trailer. Just three semi-trailers can transport the rest of the crane. The vertical tower, a six-section telescopic mast, extends up to 81 m (266 ft). Four spreaders at the top of the mast attach by pendant links to four stabilizers at the base of the crane. A telescopic luffing boom mounts at the top of the vertical tower. Fully extended, the GTK1100 has a hook height of more than 140 m (459 ft). The company says the crane maximizes lifting capacity while offering a lower cost of operation than existing equipment.
Through the next decade, wind turbines will continue to grow in output and size. Offshore wind turbines under development will add another level of comp-lexity. These turbines will have a 5 to 6 MW output, with possible hub heights of 120 to 160 m.
Different manufacturers are pursuing various methods for installing these giant turbines. Some projects will be built on shore and erected as a complete unit that could require lifting capacities of 2,000 to 2,500 tons.
The figures are not misprints. A crane’s maximum capacity comes with the boom close-in and to lesser heights. For example, the Model 18000, which is used to erect many turbines, has a maximum possible capacity of 827 tons. However, its capacity is reduced when doing wind power work because it is fitted with a long boom for lifting turbine elements at (reasonable) radii and tall heights. Extrapolate the figures and one conclusion suggests that cranes three times the size will be required to place a future generation of wind turbines. Such equipment may be large, but not inconceivable. Cranes with these capacities already exist – the Manitowoc 31000, for example.
Others projects will use a more modular approach and require cranes with capacities of “only” 1,000 to 1,200 tons. Onshore and offshore turbines will require significant lifting capacity which does not yet exist. WPE
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