Page 45 - North American Clean Energy July/August 2019 Issue

turbines have to be more e cient with higher yields. To this end, there is a much greater focus on technical solutions like modern hybrid towers, which promise greater e ciency in the design and construction of wind turbines through higher hub heights.
High hub heights are ef cient
Reduced subsidies aren’t the only reason the U.S. wind power market is facing major challenges. e cost e ciency
of wind turbine towers made from
steel in the U.S. is partially dependent on uctuating steel prices. Moreover, steel towers in 2017 had an average
hub height of only 80 meters, and a turbine output of 1.63 megawatts. ese comparatively small dimensions place limits on economic viability – limits that can be overcome with hybrid towers and signi cantly higher hub heights.
e modular tower concept, made up of steel and concrete elements, allows the economically viable implementation of hub heights up to 190 meters. e lower part of the tower is made of concrete elements, and the steel tube upper sections are placed on top. Each
additional meter increases the energy yield of the turbine by up to 1 percent. Especially at inland locations, it is often the case that, the taller the wind turbine, the better the wind shear and hence the yield. At a reference site in Iowa, for example, an average additional yield of 0.8 percent per extra meter was achieved when the average hub height was raised from 80 meters to 140 meters.
e technology in new wind turbines is becoming more powerful, larger, and heavier. Rotor diameters are also growing to generate electricity even more e ciently from the wind, and the forces acting on wind turbine towers
are increasing. Hybrid Towers are able to meet these challenges. Using hybrid construction, it becomes possible to nd the economic optimum for required tower heights of 130 meters and above. e concrete component is completely maintenance-free and especially durable.
Production with local labor and raw materials
Another factor that speaks for the innovative tower concept is mobile fabrication. National or regional logistical requirements can be met. Just as importantly – especially in the current market climate - punitive import tari s avoided. On-site production facilities can use local raw materials and labor, and the concrete elements for the tower can
be transported with regular trucks, so there’s no need for oversize load transportation over long distances. All of these factors bene t the environment and the bottom line.
Christoph Bosch is Head of Distribution at Max Bögl Wind AG, a worldwide company that manufactures hybrid wind turbine towers on site.
Max Bögl /// www.mbrenewables.com
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