A new tool will help make vertical wind turbine farms possible

Making offshore wind turbines lighter and cheaper to construct.
Ameya Paleja
Sandia’s experimental 34-meter-diameter, vertical-axis wind turbine.

Sandia 

A new design tool built by Sandia National Laboratories could help accelerate the development of vertical axis offshore wind turbines, a press release from the multimission laboratory for the U.S. Department of Energy’s National Nuclear Security Administration said.

Conventional wind turbines use a horizontal axis where the turbine is placed on top of a high tower to maximize the energy generation from blowing wind. The bigger the sweep of the turbine, the higher the energy generation, prompting turbine manufacturers to go bigger with their designs.

However, this presents a problem when planning offshore wind farms. In the U.S. for instance, offshore wind farms can generate maximum power if placed in areas where the sea is over 200 feet (60 m) deep. This raises the cost of construction for the turbines significantly, which then increases the cost of production of renewable power, making the transition to emission-less power more difficult.

The vertical axis wind turbine

The horizontal axis wind turbine is not the only way to generate energy from the wind. Instead of a three-blade design, one can also use two blades placed vertically with a generator under them. Called a Darrieus vertical-axis turbine, this design weighs far less than the horizontal axis design and has a low center of gravity, making it suitable for offshore applications on floating platforms.

The adoption of these turbines has lagged due to one major drawback, their inability to withstand extreme winds. Unlike horizontal axis turbines that can simply turn away from strong winds, the Darrieus design cannot escape extremely powerful winds. Brandon Ennis, the technical lead for offshore wind at Sandia National Laboratories, had a solution to this problem.

In his design, the vertically placed turbine blades would be without a central tower but held together with adjustable guy-wires that can be shortened or lengthened to control the strain on the turbine blades during turbulent weather. Since the central shaft is not required in this design, the overall weight and the turbine's size are further reduced, making it ideal for offshore applications. Sandia filed a patent application for this design in 2020.

The need for a validation tool

For the company to deploy the turbine, it needed to demonstrate that the design could withstand the conditions at sea and generate power optimally. However, there was no tool that could validate the design of a vertical-axis wind turbine. So, Sandia set about creating a design tool that could be used for this process. To do so, the team used data from Sandia's own vertical axis turbines that were built in the 1980s.

Now that the team has completed building its tool, it plans to use it to design a cost-effective floating vertical-axis wind turbine system that it believes will be ready by the end of the year.

"Normally one company will design the turbine, another company designs the floating platform for that fixed turbine design, and then a third company installs that with other systems to make an offshore wind plant; and you get what you get in the end in terms of cost," Ennis said in the press release. "We’re designing the entire system, the turbine and platform, and their control, concurrently to reduce the levelized cost of energy, not just the cost of the turbine itself."

Additionally, Sandia also plans to use the tool to certify other vertical axis wind turbine designs that others may develop in the future.

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