In close cooperation with Henkel, the German start-up company TimberTower GmbH implemented a pilot project that could herald a new era for the wind power industry.
Reaching a height of some 100 meters, a wind turbine tower of spruce and the first of its kind has now been built near Hanover, Germany. Yet no dowels, no nails, and no screws or bolts are used to hold this timber construction together. Instead, the support tower has been adhesive-bonded using a special process with various wood adhesives of the Purbond brand manufactured and marketed by Henkel Industrial Adhesives. The associated turbine-generator set is due to be hooked up to the grid this December.
The project offers great promise for the future because switching to wood raises the prospect of increased tower heights. From the point of view of the operator, this aspect is particularly interesting because, at an onshore site, every additional meter gained means roughly 1% more in revenue, says the company. Currently, tubular steel towers are made by assembling massive rings that have to be transported under highway bridges. With this technology, the ring diameter is always going to be a limiting factor. Hence, the maximum height of construction currently lies at 110 meters. Wood is a potential problem-solver as the components can be moved with relative ease to the site where they are then be assembled to create the larger-sized parts.
Close cooperation with Henkel
As a renewable resource, moreover, timber is in many respects superior to conventional materials such as steel and concrete. The service lifetime alone of the new system is likely to be double that of conventional solutions, according to the new German start-up company TimberTower GmbH, which implemented this project in close cooperation with Henkel.
In a direct comparison, steel and concrete are prone to much faster fatigue development. Particularly under heavy strain, both materials lose much of its meager elasticity, causing brittleness. And that is why wind turbines tend to be disconnected from the grid after around 20 years. Wood does not have this handicap. The structure-strengthening effect of the glue also helps, with the result that the TimberTower generator with its capacity of around 1.5 MW should be able to supply electricity to around 150 households in Germany’s Lower Saxony for the next 40 years.
20 to 30% less expensive
“The way we see it, a timber tower offers nothing but advantages,” says TimberTower’s General Manager, Holger Giebel. “It has greater stress resistance, can be built significantly higher and is 20 to 30% cheaper to make. The Purbond adhesive joints had to prove their suitability right from the start of the construction project, with each one duly receiving a certificate of worthiness from the DIBt, Germany’s institute of building technology.”
Now a white waterproofing membrane has been placed around the octagonal, wooden outer shell to protect the tower from the elements. The massive cross-laminated timber located underneath are bonded with Purbond. Bolts were only used in the initial assembly phase in order to secure the structure. Once the tower was complete, all the mechanical fixtures were removed and the stabilizing inner construction was then adhesive-bonded from the inside using a specially developed application technique involving the 2-component casting resin, Purbond CR 421. The adhesive penetrates deep into the pores of the wood and interconnects the cross-laminated timber panels with the perforated steel plates. The timber tower weighs more than 90 metric tons, with the top-mounted gondola and rotor blades adding another 100 tons.
Filed Under: Construction, News, Towers
Georg Becker-Birck says
Unfortunately, the named limit of 110m for steel towers is not correct. It is true, that eventually ring diameter become a limiting factor in transportation, but there are several all steel towers on the market, mass produced, with higher hub heights, for example the V90 2MW 125m or the V112 3MW 140m.
The Timbertower is an interesting alternative to choose from when you compare it with currently available all steel, all concrete or steel-concrete hybrid towers.
Pedro Perrelli says
Excelent news, specially for developing Markets eager to cut construction costs.
In Brazil we suffer from a steel plates high pricing and concrete towers are growing more and more popular.
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