Wind power engineering is governed by a simple fact: The higher you go, the stronger and steadier the wind gets and the more power you can generate. So the evolution of wind power over the years has largely been a process of building bigger and bigger blades and perching them atop higher and higher towers.
The turbine being assembled in this video, by MidAmerican Energy, will be the tallest land-based wind turbine ever built in the US, with a hub height (ground to center of blades) of 115.5 meters (379 feet) and a capacity of 2,415 kW. It's not quite up to the level of the best turbines in Europe, but it's mainly meant as experiment.
Here's a nice graphic showing the growth of wind towers over the years:
Wind towers in Europe now routinely reach 120 to 140 meters (over 500 feet).
US wind towers are catching up with Europe's
The US has not quite caught up. Since 2011, average hub height in the US has stalled out at about 80 meters (or 262 feet):
What explains this? Part of it is the fact that US wind resources are generally stronger, especially in the upper Midwest, which somewhat reduces the incentive to build higher. Some of it is cost and regulations. But a surprisingly big piece is transport.
The taller a wind tower gets, the bigger the diameter of the base. But at this point, those giant cross sections of steel tower are getting so big that they can't be transported via interstate. In a fascinating post on the future of wind technology, energy analyst Ramez Naam pulled this image out of the Department of Energy's Wind Vision report:
Tower sections bigger than the standard (80-meter) kind have to be transported via special trucks, and only on certain highways. It's a huge bottleneck.
(Another reason EU turbines are taller is that more of them are in the ocean, where transport can be done by boat.)
Concrete turbine towers can get around transport restrictions
So engineers and designers have begun looking to concrete. The advantage of concrete towers, besides the fact that concrete is an extremely well-understood material with a well-developed industry behind it, is that they are modular. They come in smaller pieces, which can be transported via regular trucking and safely assembled on site.
(Theoretically, steel could be cut in smaller pieces too, but assembling steel pieces, i.e., welding, on site is much more difficult and technical than snapping concrete Legos together.)
It's still a fairly new idea — only a few concrete wind towers are currently in operation — but as the drive to push turbines ever higher continues, it could take off.
The MidAmerican Energy turbine in Iowa is testing the concrete model. If it succeeds, there is little limit to how tall towers could get, though at a certain point land use considerations come into play. Concrete is extremely carbon-intensive at present, but there's lots of work underway to make it lighter, stronger, and greener. (There's also work being done to develop hybrid concrete/steel towers.)
It would be somewhat ironic if concrete, one of the oldest and most boring elements of industry, were the future of wind.
Finally, just for kicks, here's a bonus video on the advantages of concrete for wind towers, from a company called Acciona: