A wind turbine blade is largely made of a mixture of composite resins which guarantees strength, flexibility, and lightness wind turbine blade is largely made of a mixture of composite resins which guarantees strength, flexibility, and lightness.
There are glass fibers, carbon fibers, polyester resins and epoxy resins, but balsa is also essential for the manufacture of the blades. To reinforce their rigidity, this rigid and light wood with multiple qualities is used over the entire length of the blade to ensure flexibility between two layers of fibers.
Raid on the balsa
While forty years ago the blades were barely 10 meters long, those of offshore wind turbines now reach 100 meters and allow turbines to produce up to 14 MW. However, according to engineers from the US National Renewable Energy Laboratory (NREL), no less than 150 cubic meters of balsa are needed to make a single 100-meter-long blade.
Balsa is a fast-growing species; it reaches its maximum density in just five to seven years. But with the wind boom, demand has far exceeded supply. And when we know that Ecuador accounts for more than 75% of the world production of balsa, we quickly realize the economic and strategic challenges linked to this wood. No wonder either to see its price reach 1,800 euros per cubic meter in 2020, double the price of 2019, and triple that of 2018.
An alternative at all costs In 2020, three-quarters of Ecuadorian balsa exports went to China. The volatility of material prices, the risks associated with the supply chain dominated by a handful of voracious Asian competitors, as well as the environmental damage caused by wild logging in the Amazon rainforest, prompted builders to find an alternative and to modify the composition of the wind turbine blades.
Because the felling of this light and flexible wood does not spare the environment: even if balsa does not store much carbon, unlike other rare species of the Ecuadorian forest, the lack of regulations regarding the species growing rapidly leads to various perverse effects. Hunting parties, destruction of other plant and animal species, and various trafficking are commonplace.
LM Wind Power the first company developed a blade made by recycled bottles
After several years of research, the Danish company LM Wind Power, a world leader in the manufacture of wind turbine blades, developed in 2017 a blade whose main laminate is made of recycled polyethylene terephthalate, or R-PET. It is a plastic commonly used in food and beverage packaging and is widely collected and recycled in Europe.
The qualities of R-PET differ from those of balsa, but PET foam sheets are further reinforced during the manufacturing process, making the blades even stronger.
Avoiding the shortage of balsa
In 2019, the demand for balsa was such that several blade manufacturers had to shut down their production lines due to a lack of supply.
Some manufacturers like LM Wind Power, who have relied on recycled PET, have been able to maintain production and have experienced growth of 30%.
Vestas, the world’s leading manufacturer of wind turbines, delivered its first machines fitted with blades made entirely from PET. Since then, other manufacturers have followed suit.
It remains to be hoped that the extraordinary growth of the balsa market, and the supply disruptions that followed, will have definitely convinced the most reluctant turbine manufacturers to turn to R-PET which, even if it has long regarded as lower quality material, makes it possible to manufacture foam that is more durable, much cheaper, and guarantees the supply chain.