Research by BTM Consult shows that in the period 1995-2004 aggregated global installation capacity grew from around 1,000mW to 8,152mW. The researchers’ predictions for the future are even more impressive, however. By 2015, BTM predicts that more than 32,750mW of generating capacity will have been installed, rising to as much as a million megawatts in 2025.
Birger Madsen of BTM Consult explained that the current maximum generating capacity of turbines in commercial use onshore is around 2.5-3mW, with some 5mW turbines under development.
Globally, the average installed capacity of turbines is 1.3mW. However, this average does not provide a full picture . In developing markets, such as China and India, average sizes stood at less than 1mW in 2005. In Denmark, Germany, Spain, Sweden and the USA, turbines averaged 1-1.5mW. In the UK, average turbine sizes were above 2mW.
In the west, this demand growth is being driven by a combination of environmental concerns, rising fuel prices, and a recent political focus on ‘energy security’. Elsewhere in the world, in countries such as China, wind power promises to provide small-scale, local, generation to far flung rural populations who, until now, have been out of the reach of electricity infrastructure projects.
While wind energy may appear to be a panacea for these political and economic ills, it throws up a new range of problems for the crane industry. On offshore sites, where the highest capacity turbines are being installed, cranes and turbine parts need to be moved, requiring the development of specialised barges and mobile platforms. On land, the problems are perhaps even more intense.
The best place to put an onshore turbine is often on the crest of a hill, in the middle of peat moorlands or in wooded areas, places considered to be particularly scenic and in need of protection from damage by access roads, but which may also suffer from difficult ground conditions.
To get the most benefit from any site, multiple turbines need to be installed, usually around 100m apart. The heaviest component in any turbine is the nacelle – the generating unit to which the blades are attached – which can weigh from 22t for a small 750kw or 1mW generator, to 65-90t for a large 2-3mW unit. On smaller units this may need to be lifted up to 80m, and as high as 110m for the largest turbines.
As Jean-Louis Lapointe, director of Guay crane rental in Montreal, Canada, explains, “We’re usually lifting five main components – three mast sections, the nacelle, and rotor. The pad is prepared and the first tower section is erected using a smaller crane. Once the crawler has installed the remaining tower sections, the nacelle needs to be installed the same day, to provide stability and to protect the mast against wind damage. This means the job needs to be quick and precise. We need excess lifting capacity to be able to do this.”
Ground conditions are often an issue. In Scotland, Weldex often installs turbines in peat moorlands. As Brian Hyde, technical services manager at Weldex in Scotland, explains, “The planning restrictions mean we can’t dig down into the peat more than one metre. If the peat’s deeper than that, we can’t dig down to hard ground, so have to use floating roads – we put in a couple of layers of material, and then hardcore. There’s still a lot of bounce, so we have to take care with weights.”
Crawlers v. mobiles
For many people in the wind energy industry, truck mounted cranes have been the preferred tool for turbine installations. As Hugh McNally, MD of Windhoist-McNallys, explains, “We generally use truck-mounted cranes. They’re more flexible, very powerful, and easily moved. They’re much more efficient than crawlers. Sites we’ve worked on in France may be suitable for crawlers, as they’re flat, arable, land. In the UK, where we work on mountains and peat, we prefer to use mobile cranes. Roads are a big problem on these sites.
“We can erect most turbines using mobiles. This involves less civil engineering work than using crawlers. Our 500t truck-mounted crane will erect most available turbines.
“We’ve recently put in an order for a new 1,000t telescopic boom that Liebherr is developing. We expect it to feature a 100m main boom on a 9-axle carrier, with a range of boom attachments.”
David Slack, MD of Nationwide of the UK, concurs: “We use a 500t Liebherr LTM1500-8.1. One of the biggest problems on wind turbine sites is wind. The LTM1500-8.1’s Y-system boom back mast strengthens the boom, and reduces deflection both sideways and laterally. We do a lot of maintenance work, and the mobile booms are good for this.” Like McNally, Slack is also looking ahead to Liebherr’s planned 1,000t mobile boom, which he believes will have the capacity needed for installing 2.3mW turbines.
Not everyone in the industry agrees however. For companies such as KR Wind, Weldex and Guay, a new generation of crawler cranes aimed specifically at the wind turbine installation sector provide a much needed combination of power and mobility.
The key argument against using crawlers in the past has been the width of the crawler tracks, and their perceived lack of stability and agility. This has demanded that wider roads are built on difficult terrain. The regular nature of wind turbine installation – with generally the same loads needing to be lifted to the same height, under similar conditions – has meant that crane manufacturers are able to plan highly specialised solutions. By making use of different configurations of outriggers on crawler bases, they have been able to add stability to some of their most powerful cranes and spread the load exerted on difficult ground conditions.
Terex-Demag CC2800-1 NT
Terex-Demag’s approach to the problem of wind turbine installation has been to develop a narrow track system for its 600t CC2800-1 crawler launched last month. Using a 102m SH/LH SGLmax main boom and a 12m LF2 fixed jib, the crane can lift loads of 109t to a hub height of 106m. With Demag’s Superlift system, which uses a second boom on the rear of the crane to carry extra counterweight, loads of up to 97.5t can be lifted up to 130m above ground level.
The narrow track (NT) system allow the crane to travel on 5m roads, meaning it can be moved between wind turbine installation pads without disassembly. When moving, the crane’s outriggers can be raised into a vertical position, increasing its side clearance.
For Jean-Louis Lapointe of Guay, the NT system and the CC2800-1’s lifting capacity are key selling points: “At the site, using the narrow track helps with our PR with wind farms and local communities. Many Canadian wind farms are in wooded areas, and using the narrow track means we don’t need to cut down as many trees when roadbuilding. This also saves money with access, both in terms of the amount of work and payments we need to make to farmers.”
Terex-Demag has also focussed on making the CC2800-1 NT more manoeuvrable with electronic control systems and a low centre of gravity. The crane can also manage a 10° inclination forwards and backwards and an inclination of up to 2.5° side to side.
As Rüdiger Zollondz, Terex Demag’s lattice boom crane product manager, explains, “A big problem on these sites is the stiffness of ground and geotechnical conditions. The electronic system on the CC2800-1 NT is monitoring and displaying the centre of gravity even on the remote control, thus the operator can easily make the necessary adjustments of boom angle, making the crane more stable.
Although only recently launched, the CC2800-1 NT appears to be selling well. Klaus Meissner, director of R&D at Terex-Demag, says, “So far we’ve sold eight NTs, and 15 S7 boom systems. We’ve got a lot of requests too. Customers are looking at a six month wait for the NT system for an existing crane, and slightly longer to buy a complete CC2800-1 NT, due to component shortages.”
One of the first firms to buy the NT has been KR Wind in Denmark. At the time of writing, KR Wind had just finished rigging their new CC2800-1 NT at Kjøllefjord wind farm near Mehamn, Norway. Over the coming months, it will be used to erect 17 2.3mW turbines on 70m high towers, travelling between 300-1,000m between each lift.
The crane is up against the Liebherr LR 1400/2-W, launched dramatically at Bauma two years ago.
Liebherr LR1400/2-W
Liebherr worked closely with Weldex to develop the 400t, 132m lifting height, LR 1400/2-W crawler crane. Dougie McGilvray, MD of Weldex explains, “The development of the LR1400/2-W system came out of meetings we had with Liebherr Ehingen in Germany. Up until then, we’d been using smaller 150-280t crawler cranes with narrow track systems, or standard crawler cranes that needed to be dismantled and re-assembled between turbine bases on windfarm contracts.
“At this time the crawler crane that we had could only erect turbines up to 1.3mW. We wanted a crawler crane with narrow tracks that could erect turbines in the 2.3/2.5mW class; this would require a 400t-class crawler crane.”
David Milne, director of Liebherr UK, was also at the meeting: “So, as a piece of ‘back of the envelope’ design at the meeting we came up with the idea of a double slewing ring with 4.8m wide track width for travel. In a normal crawler, you have the centre section with slew ring, then the superstructure. In the 2-W system, we have the centre section, the first slewing ring, the outriggers, a second slewing ring, and then the superstructure. This allows the crane to negotiate tight bends by lifting up on the outriggers and then turning the tracks.
Weldex used the LR1400/2-W on a Siemens Windfarm contract in Norway where it erected 48 2.3mW turbines in 55 days. Brian Hyde of Weldex notes, “We needed these new narrow track systems for our production rate. Previously, stripping crawlers down, moving and rigging them again at each pad could take two days. If we can just walk between pads, that only takes two or three hours. That means that we can complete the installation in one day, and have it ready at the next pad for Siemens’ typical 7am start.”
Like the CC2800-1 NT, the LR1400/2-W’s outriggers can be retracted to save space while travelling. While the Demag crane’s outriggers rise upwards, the Liebherr’s swing laterally from a 4.8m wide front-and-rear position to an 11.5m wide star configuration. One LR1400/2-W boom configuration generally used for 2.3mW turbines features a 63m main boom, with a 10.5m fixed fly at 20° offset, sufficient to lift a 90t nacelle to a maximum height of 71m. With an SF2 boom system, using a 77m main boom and 10.5-38.5m heavy luffing jib, 2.5mW class nacelles can be erected on 80m high towers.
Kobelco CKE 2500-2 WS
Kobelco boasts that the hydraulic controls of the CKE 2500-2 offer a level of precision that makes the cranes ideal for the high-level placement of heavy loads, such as nacelles on turbines. A new, stronger, luffing jib has been introduced and a new tapered system means that the luffing jib can be used for long boom configuration. The maximum main boom length for the crane is now 91.4m; the 76m standard crane boom can be combined with a 30m fixed jib, and in a luffing jib variation a 61m boom can be fitted with an equal-sized jib.
As this article was going to press, Kobelco confirmed that it was to launch a new Windmill Special, or ‘WS’ version of the CKE 2500-2. The special version of the crane will feature retractable crawler frames and a special 36m fixed jib head.
Like the Liebherr and Terex-Demag cranes, the WS specification will allow the crane to travel on narrow roads at installation sites — in this case, the retractable crawlers mean the crane’s overall width can be changed from a 7.62m lifting configuration, to a 5m travelling configuration.
A fully equipped CKE 2500-2 WS will feature a 61m main boom and a special 36m fixed jib. This combination will be capable of lifting 42t at 15m radius, up to a height of 85m — suitable for most nacelle installations.
Kobelco has signed its first orders for the CKE 2500-2 WS, with Transbiaga in Spain, where they will be used for a range of general contracting and rental jobs, but with a focus on windmill erection.
Manitowoc Model 16000
Manitowoc has also targeted the wind energy market with its 400t Model 16000 crawler. As Raman Joshi, global product manager for Manitowoc Crane Group explains, “This crane has a lifting capacity of 400t with a main boom designed to reach 89m. The attachment that sets it apart is the pin-on heavy duty 97.6t detachable upper boom point. This allows the 400t machine to work on 80m towers.” This attachment allows the crawler to get close to the mast, and still lift heavy components.
In South Korea, local firm Unison Co used a Manitowoc Model 16000 to install 49 2mW turbines, with 73t nacelles, at Gangwon Wind Power Park in Kangwondo.
Unlike the Liebherr and Terex-Demag cranes, the 16000 can’t generally be walked between turbine sites without derigging. However, Manitowoc’s modular design and FACT connection technology meant that re-assembly times were cut significantly, compared with conventional crawlers, the company says. Unison job site manager Park Gyu-Tae commented that, “Although it sounds time consuming, actually assembling and disassembling the Model 16000 is very easy.”
Earlier this year, the same model was used by HB White Canada to install eight 46t nacelles on 80m masts at Canada’s largest wind farm near St Leon in Manitoba. On this job the crane used an 89m boom with a 7m extended upper boom point, and 205t of counterweight. The firm has also used the crane at the Erie Shores Wind Farm in Ontario. At this site, they installed 66 80m high turbines along 18 miles of the lake’s north shore, using the same configuration of main boom and pin-on extension.
The outlook
Wind turbines’ popularity is likely to grow. They are also likely to grow larger, because bigger turbines generate more electricity. This will push current lifting technology to its limits. As David Milne at Liebherr explains: “The industry’s currently heading towards 3mW turbines, which the Liebherr 1400 can handle. Beyond that, at the 5mW size, you face issues relating to road travel and erection, and site accessibility.We have developed a 1350t crawler, which could lift 5mW turbines, but it will be very expensive to rig and de-rig.”
Klaus Meissner at Terex-Demag shares these sentiments, “The CC2800-1 NT will be meeting the market’s needs for at least the next five years. There needs to be an urgent debate on the size of the next generation of turbines, and the economic optimisation of their design, specifically, whether they are broken down into more components for lifting.
“End users need to reach a balance between time spent on lifting and time spent on rigging cranes and preparing the site. The CC8800 could lift larger turbines, but it will take more time to rig. Using more components in turbine construction would mean that smaller cranes such as the CC2800 could be used, but each installation would take longer.”
