Technology
A new design tool from Sandia National Laboratories could help accelerate the development of vertical axis wind turbines (VAWTs). Nicholas Kenny speaks with Brandon Ennis, offshore wind technical lead at Sandia National Laboratories, to learn about the benefi ts this tool can provide, how Sandia used this new technology to design a cost-effective fl oating VAWT system – and what it means for the future of the industry.
he form and function of wind turbines has been largely settled for decades. We all know what comes to mind when you think of one – a tall structure with three blades near the top, rotating along a horizontal axis. These horizontal-axis wind turbines (HAWTs) have reigned supreme over global wind energy production since the 1980s – but it was not always so open and shut.
In the 1970s and early 1980s, much of the wind industry was focused on the development of vertical- axis wind turbines (VAWTs). They differ from their horizontal cousins in that their main rotor shaft is set transverse to the wind, and the main components are located at the base of the turbine, rather than the top. This arrangement allows the generator and gearbox to be located close to the ground, making replacement and maintenance simpler and more efficient. VAWTs also don’t need to be pointed into the wind, removing the need for wind-sensing and orientation mechanisms.
So, the advantages of VAWTs were clear to those early pioneers in wind technology. However, there were a number of challenges, too – VAWTs undergo significant torque ripple during each revolution and their blades are prone to fatigue due to the wide variation in applied forces during each rotation, shortening their lifetimes. These challenges are particularly relevant to the Darrieus turbine, a VAWT subtype where the turbine consists of several curved aerofoil blades mounted on a rotating shaft. The Darrieus turbine was first envisioned about 100 years ago, invented by Georges Jean Marie Darrieus, a French aeronautical engineer who patented the design in 1926. It was later introduced to Canada in the mid- 1960s, when another team of inventors applied for the patent without being aware of Darrieus’ work. From there, a large portion of Canadian turbine development was focused toward VAWTs, and several projects were initiated, lasting until the 1990s.
In the early 1970s, Sandia National Laboratories was assigned by the US Department of Energy (DoE) to investigate alternative energy resources and quickly learned about the Canadian VAWT research, explains Brandon Ennis, offshore wind technical lead at Sandia. “Sandia has a really storied history with studying VAWTs,” he adds. “When Sandia’s wind energy department started in the ‘70s, it was in response to the [1973] oil crisis. The government started to realise that energy is security, and Sandia, being a national
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