Background on Wind Turbine Rotor Blades
A very tangible token of the development of the wind industry is the increasing size of wind turbines. Today, the world’s most powerful turbine is MHI Vestas’ V164 — at 220m (722 ft), it’s also the world’s tallest turbine; with blades of 80m in length, it has a total diameter of 164m (538 ft), and a rated capacity of 8MW. It’s enormous, and designed for offshore operations.
The principal driver for the lengthening of wind turbine rotor blades to such lengths is an economic one. A wind turbine’s power output is proportional to the square of its blade length — this is because longer blades equate to a larger swept area (the area through which blades pass as they rotate); with a larger swept area, a wind turbine is able to capture a higher amount of wind energy. (The V164, for instance, has a swept area of 21,124m2.)
Again due to larger swept areas, longer blades allow turbines to operate more efficiently at low winds speeds because they’re able to capture more energy from the wind, even when speeds are low. For all wind farms, such capability ensures they continue to operate even when the wind drops — therefore reducing intermittency of generation –. But efficiency at low-winds also opens up opportunities for establishing wind capacity in regions that are persistently subject to low-winds — recognised as holding massive market potential.
The net result of longer blades is reduction in levelised cost of electricity (LCOE) — the key metric for developing renewable energy, reflecting the final cost of electricity that’s produced when all factors are taken into consideration.
Simply put, larger blades allow turbines to produce more electricity, more efficiently. But there are huge challenges at play in this area of innovation.
The following article, published in Renewable Energy World, discusses this topic, and considers how novel testing methods are being explored to facilitate the trend for longer blades.
(A nice video from MHI Vestas – Building blades for the V164 – shows some of the blade testing that’s discussed in the following article and gives a sense of how large the machine really is.)
The following text is an excerpt from article published in full at Renewable Energy World, by William Steel.
At the heart of blade innovation is testing. A juncture between design and commercialization, blade testing is necessary to develop novel concepts, assure manufacturers that designs meet specification, and ultimately gain certification for market entry.
As it stands today, blade certification processes involve a comprehensive battery of tests, including mandatory full-scale blade testing — something Simon Pansart, head of section rotor blades, renewables certification at DNV GL Energy, describes as “one of the key elements of the type certification process,” on account of how it “drive[s] the time-to-market date,” but also since “it’s one of the largest cost factors in certification,” owing to the duration, and infrastructure requirements of the tests.
With wind power RD&D as intense and competitive as it now stands, there’s cause for faster validation and certification of designs. As Florian Sayer, head of department division structural components at Fraunhofer Institute for Wind Energy System Technology (IWES), said, “The industry requires new, more sophisticated, more efficient approaches to testing and certification to assure the pace of innovation.” Sayer’s company, IWES, is a German applied sciences institute at the forefront of blade testing, and in describing his perspective on innovation in blade testing, highlights the importance of “looking towards the trends in blade design and developing future test concepts accordingly.”