Engineering news
Engineers in the US are set to install the world’s first prefabricated concrete wind turbine next year after reporting successful laboratory fatigue tests for the structure.
The 2.3MW Hexcrete turbine, which will also be one of the tallest in the world, is to be built at the Adams Windfarm in Iowa. It will measure 115m from ground to hub, and 169m to the tip of its blade at the highest point.
The wind turbine tower, which is being developed at Iowa State University, is made from precast columns and panels of high-strength concrete. The columns and panels of the Hexcrete system are tied by cables to form hexagon-shaped cells that can be stacked vertically to form towers as tall as 140m.
The fatigue tests have involved using hydraulic equipment, to simulate the twisting loads that the tower will have to withstand, on a test column over a duration of months. The 3.65m high and 2m wide test column is rocked with 100,000 lb of force (224.81kN) every 1.25 seconds. Around 65 strain and displacement sensors collect data 50 times every second over weeks of fatigue testing. A researcher also examines the test section
for signs of wear.
The fatigue test is ongoing, but after almost 200,000 load cycles, the researchers have detected no damage. The tower cross-section had no trouble resisting the loads, and preliminary data analysis confirms that observation, said Sri Sritharan, Wilson Engineering professor in civil, construction and environmental engineering at Iowa State University.
“These tests were a success. We’ve made great progress in validating a new concept of using prefabricated concrete for taller wind turbine towers. Our goal is to build a full tower in the field,” he said.
Mike Gehringer, vice-president of renewable energy at MidAmerican Energy, which owns and operates the Adams Windfarm, said: “The process of building a concrete tower is quite different from the process we use to construct turbines with steel towers. Instead of building the tower sections in a factory and transporting them to the site to be fitted together, crews pour the concrete in segments and manufacture the tower onsite.”
The researchers believe the ability to construct higher towers will enable wind turbines to access faster and steadier winds, increasing the electricity produced and reducing the cost of transport and of deployment of windfarms.
Partners on the project include Siemens and concrete producer Lafarge. The research will produce a commercialisation plan.
Large commercial wind turbine towers are usually around 100m tall. The current tallest turbine is Vestas’ V164 8MW prototype at Denmark’s national test centre in Østerild.