The fact that wood is not being used more extensively in vehicles, aircraft, construction, and perhaps even in machines mainly originates from a lack of insight and might be based on prejudice as well. The comment from a German manufacturer of wind energy plants was highlighted in a flashback story by senior editor Jim Bowden in August 2011.
“In combination with modern adhesives technologies, wood is an ideal material for the construction of wind turbine units,” says Gregor Prass, an executive of Timber Tower GmbH which specialises in the manufacture of wind energy plants.
More than 22,000 wind turbines already cover about 10% of Germany’s electricity needs. It would take about 26 coal-fired or nuclear power plants to produce the same amount of energy. Worldwide, roughly 100,000 new units will be built in the next three years.
But there are problems to be solved, especially those that present obstacles as tower heights continued to increase.
“Frequency problemsthat occur as a result of resonances between blades and towers in large units can be solved much more elegantly with wood,” says Mr Prass. “The costof building towers is significantly lower with wood in comparison to steel and concrete.”
He points to the predictability of the costs: in the period 2003-2007 the price of steel increased by a factor of 13, a decisive factor for an industry that ranks only behind automakers in steel usage.
The outlay involved in wind energy facilities must be calculated with project lead times of at least five years and given the price fluctuations of steel in the recent past, it is no longer possible to make reliable projections.
In Canada last year the world’s first industrial wind turbine installed on an engineered timber tower was constructed of cross-laminated timber, the same material used to construct a nine-storey, 27-unit apartment building in London.
Gregor Prass says the cost of maintenance is expected to be considerably lowerfor both offshore and onshore wood towers.
“Wind farms are often built in coastal locations; and the salty climate entails a corrosion- protection effort that should not be underestimated.
Of course, it is difficult at this point to calculate the fatigue strength of wood, but Timber Tower GmbH guarantees a tower lifecycle of at least 20 years.
Mr Prass says wood offers highly decisive advantages in terms of the logistics involved in building ever-higher towers to more than 100 m.Steel structures must be delivered to the construction site with heavy-load vehicles; additionally, their diameter is limited to 4.20 m because of the clearances of highway bridges.
Conversely, wood towers are manufactured out of glued laminated timber panels and designed to be transported to the site as individual modules which are then assembled on location.
For this purpose, standard containers are sufficient and no special heavy-load transport vehicles are needed.
“Last, but not least, wood is a renewable resource of considerable ecological significance,” says Mr Prass.
“The wood used for timber tower structures comes from sustainably managed forests. The wood suppliers operate under PEFC (Program for the Endorsement of Forest Certification) schemes which guarantee compliance with ecological, economical, and corporate citizenship benchmarks in forestry.
Mr Prass is convinced that wood ranks among the key resources of the future – but not necessarily as a reflection of ecological awareness, he points out.
“It’s price/performance ratios and hard technical data that count because in the domain of wind energy, the money also comes from hardline investors – and their emphasis is on profit.
“The fact that wood is not being used more extensively in vehicles, aircraft, construction, and perhaps even in machines mainly originates from a lack of insight and might be based on prejudice as well.”
“Fire protection specialists know that wood resists fire much better than reinforced concrete but have second thoughts about its stability. Civil engineers might trust the stability of wood but are sceptical about its fire resistance.
“There is a huge repository of knowledge about its fire resistance. In the 1930s, machines, propellers, and even entire aircraft were made of wood.”
But in his opinion, the knowledge is not being properly evolved. Faculties for timber engineering at universities are gradually disappearing and new ones are established only very rarely. But thanks to innovative bonding technologies that make wood arbitrarily formable and simultaneously more predictable, Prass says the conquest of wood is unstoppable.
