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PES essential
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Upwardly-mobile turbines present increasing transportation challenges
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The late economist E F Schumacher (1911- 1977) became something of a hero to the early environmental and ecological movements, not least because of his oft-quoted maxim: small is beautiful. But if that was true back in the 1970s it is nevertheless a rule which is being ignored in the current wind generation industry. If small was beautiful back in those far-off days, it is now very much the case that B-I-G is the current watchword for the movers and shakers of the US wind business. But ‘big’ does not come without a series of attendant logistical problems, especially in the area of transporting these behemoths around the highways and byways of the North American landmass. PES investigates . . .
The University of Dayton Research Institute (UDRI), was recently granted $270,000 in order to research, design and test structures and materials for composite wind turbines of up to 100m in height. These composite towers will stand as much as 65ft taller than the steel towers currently used. In fact let’s not pussyfoot around here – they would be some of the largest composite structures ever built – so much for those Egyptian pyramids, then.
According to Brian Rice, Division Head for Multi-Scale Composites and Polymers at UDRI, wind turbine towers have to be strong enough to carry the weight of the turbine (which can be as much as 100 tons) but also resist buckling under the stress of the rotating machinery. Steel monopoles are pre-fabricated in sections as large as 14ft in diameter and 70ft long, then trucked individually to the wind site to be put together and installed on a concrete foundation.
When finished, the average utility-grade wind turbine tower is about 80m (approximately 265ft) tall. But the wind industry had been setting its sights on a new standard for tower height at 100m (328ft), Rice said. Putting larger turbines on top of taller towers, of course, facilitates access to greater wind speeds, which, in turn, improves operating performance and cost so it is not difficult to see the financial attractions. As the size of wind turbines continues to grow, however, so do the problems and expense associated with transporting and building the towers.
“If you increase the height of the tower, you have to increase its diameter as well,” Rice explains. “This means that next-generation wind turbines will require towers that will be too large to ship via highway, even in sections.”
The solution here, he says, could be to use fibre-reinforced plastic (FRP) composite tower sections that would be manufactured on site at the wind farm.
“On-site fabrication eliminates the transportation problems and makes more sites accessible to wind power development,” he said. “Even today there are good potential wind farm sites in remote or hilly locations, but there aren’t sufficient roads to allow for trucking in steel towers, the new design would solve that problem as well.”
In addition, the corrosion-resistant properties of composites will be far more suitable than steel for the offshore wind farms which are just starting to be developed in US waters. Mr Rice’s international team has been working for more than two years on testing materials and coupon samples and are now ready to move into product demonstration. The partners will design, analyse, build and test a series of progressively-larger components with the ultimate goal of completing and testing a full-scale 100m composite tower.
So let’s take a more in-depth look at the potential transportation problems the industry could soon be squaring-up to. Naturally, an increase in commercial wind turbine size brings bigger challenges in transportation but it's definitely a sort of catch 22 situation, as the wider the wind turbine blades, the more energy the turbine produces – so the incentives are most definitely there. Additionally, taller wind turbines are better equipped to take advantage of the stronger winds at higher altitudes. Negative environmental impacts of these jolly green giants grow with their size.
Wind turbine size and financial costs
Some of the biggest commercial wind turbines now reach over 500ft tall with blades over 300ft wide. You may have seen these wind turbine blades lurching down an interstate on top of oversized rig beds. How about attempting to navigate a corner in a small town? Sometimes police are forced to direct traffic, ironically so that these beacons of green energy can arrive at their destination. A 2009 New York Times article quoted John Dunlop of the American Wind Energy Association (AWEA) as saying that transporting just one solitary wind turbine costs ‘around $100,000 to $150,000’.
Dan Laird, a researcher at Sandia National Labs in Albuquerque, New Mexico, said: “Within the US each state has its own regulations governing transport of large structures such as wind turbine blades. If you're transporting blades you have to know the route, which states your passing through, the various length, width and height limits for each state." In some states, lengths are accepted up to a certain limit but then you need an escort. This does not mean it's impossible to transport a wind turbine blade, but it is going to increase the cost. Then there are the hard limits of getting under the highway overpasses. This one is difficult to get around. "Obviously you could come up with some alternative route avoiding the interstates," Laird says, "but that would get cost-prohibitive in a hurry."
On the cutting edge of research focusing on wind energy, Laird's studies involve the design, analysis and manufacturing of utility-scale wind turbine blades. "The obvious first-step here is asking this question: can you break blades into pieces? For example, have some type of span-wise or even cord-wise joints which would then let you assemble the pieces and the blade at the site. As of now, nobody has figured out a cost-effective way to do that," he said.
Another researcher at Sandia is leading an effort, Laird notes, on trying to come up with cost-effective joints for composite blades. Laird doesn't believe this is right around the corner because this is something people have been looking at for a long time and haven't figured out yet. Problems arise when you add a joint to a blade, for instance, because then you’ve added a location where you are going to have a stress concentration or fatigue issues. "This shortens the life of the blade," Laird says. "It is actually a very difficult problem. The blades are designed to last for 20 years with zero maintenance." Asked if larger blades could be transported in one piece but not on the ground, Laird said that was one of the many appeals of offshore wind implementation. "If you can build the blades close to a port, and install them offshore, you're not going to have the numerous limitations that are endemic to land transport," he says.
What is the solution then for on-shore transport of blades? Mr Laird says the market for utility-scale turbines is starting to diverge a little with land-based turbines and the larger off-shore turbines. Up to the last few years, all the global wind turbine manufacturers were trying to keep their product lines somewhat simple but, as they made the turbines larger, they were trying to develop the same turbines for an offshore application as well as land-based applications.
"This is not going to continue," Laird predicts. "Because of these transportation issues, you rather reach a sweet spot for land-based turbines of the 1.5-3MW size, whereas for offshore turbines, their foundations are very expensive and there are a number of reasons that push you toward larger machines. So maybe they'll be 5-10MW machines offshore where you don't have these transportation issues."
The making of larger turbines is going to have to be a bit more nuanced where we have land-based machines in the 1.5-3MW range and offshore machines as large as the manufacturers can feasibly put together. "If the machine gets large enough then the nacelle will have the same transportation issues where you can't get the nacelle underneath the highway overpasses," Laird concludes. "You would have to start sending that in pieces as well."
Cost benefit assessments of wind turbine electricity generation focus on how much atmospheric emissions are saved by replacing fossil fuel-generated kilowatts with wind power-generated ones. More recently, a promising shift to focusing on the total life cycle analysis of the wind turbines has been taking place. Considering the entire life cycle, from extraction of ores to dismantling a turbine is a complex process. Comparing a wind farm life cycle to that of a coal plant is ridiculously complex, as is apparent when considering the extreme variations of study results. The financial implications of these studies, for both the researchers and the competing industries, likely contribute to differing results.
So what are some possible solutions to the growing problem? Building turbines, or at least the blades and towers, near wind farms is one logical way to cut the environmental and financial costs of transportation. But with varying companies producing rotors, blades and towers in the US this could prove a difficult task. The train industry, of course, is pushing towards rail transportation, as railroad cars are better suited for wind turbine size. There's also little argument that it's cheaper to move them by train. But one potential problem here is that the country’s railroad infrastructure is incomplete at best.
But we ignore the potential of rail at our peril, it seems. Railroads have a huge advantage, noted Union Pacific Director Ken Adams – “Union Pacific operates in 23 states, and we don’t need permits.” At the same time, though, railroads can only transport products up to a certain size. Using rail for parts that are larger than 14ft in height is very problematic. As a result, Mr Adams said, the railroad was communicating with turbine designers to encourage them to find ways to keep their components within a size range that allowed comparatively straightforward transportation.
Panelists at the recent Transportation and Logistics session at AWEA’s Fall Symposium generally said that efficient communication was the key to success in transporting larger and larger wind turbine components. One major factor is shorter project lead time. As Gary Kowaleski, Logistics Director for Suzlon Wind Energy, pointed out, a few years ago it was common in the industry for wind turbine manufacturers to sign large-scale frame agreements, in which a major wind farm developer would agree to buy hundreds of wind turbines over a period of years.
In that environment, wind turbine components might be manufactured in large numbers and transported to a storage location. With reduced demand and the transformation of the industry to a buyer’s market, developers are buying wind turbines more on an individual wind power project basis, and manufacturers are seeking to deliver them ‘just in time’. This change means shorter advance time for delivery of components, compressed schedules, and increased emphasis on actively communicating with state transportation agencies to obtain permits for the very large, heavy truckloads the wind industry requires.
Ryan Reed, a transportation and logistics planner for Siemens Wind Power, agreed: “Carriers have problems getting permits in time, regulatory issues with departments of transportation, and then issues with local communities. We try to get to communities well in advance so we can discuss potential problems with them and work them out.”
Mr Reed also said pressure on state budgets had added a new dimension to the problem. A police escort was required for heavy trailers in California, he said, and recently the escort for a planned shipment did not show up due to a ban on police overtime: “We went to the Department of Transportation and explained that we were paying for the overtime, and got it worked out.”
The sad fact is it seems that wind energy has outpaced many aspects of logistics and transportation and has become a big infrastructural problem due to the size, weight and length of today’s generators. International project and transport forwarder deugro is working on the art of delivering turbines around the globe. The turbines are normally shipped as separate components from the country of manufacture. In Europe, where it all began, trailers have been specifically designed to transport the various components to construction sites, for instance.
With such large, heavy and long loads, there are many constraints faced in transporting turbines from overseas factories to the final wind farm site. Constraints are faced moving them on inland roads, handling and storing them in the port and while stowing them on board a vessel. Many loads also require transportation through a number of state boundaries involving police and road authorities as well as requiring special permits to be transported. All these operations need careful planning and control to get all the plant and equipment to a remote site to build a wind farm.
One common challenge for instance, is finding a sufficient and suitable storage area in the loading and discharge port. This is why outports are often chosen for wind farm projects. These ports are located away from the major traffic hubs and can supply more available space and less traffic congestion. Heavy lift multipurpose vessels offer extra flexibility and independence by loading and discharging the heavy cargoes with a ship’s own gear. Assessing the local infrastructure and conditions in both the export and the import country forms the foundation of successful project planning. Performing comprehensive feasibility studies at the initial planning phase of each project is a basic necessity to determine the most viable transportation solution.