The latest episode of "Growing Impact" discusses the future of wind energy, including floating offshore wind turbines and a shift in turbine blade design. Credit: Brenna Buck.
'Growing Impact' looks at wind energy, floating offshore wind turbines
Aug 2, 2024
Editor's note: This article originally appeared on Penn State News.
UNIVERSITY PARK, Pa. — The latest episode of "Growing Impact" discusses the future of wind energy, including floating offshore wind turbines and a shift in turbine blade design. Wind energy is the highest-producing renewable energy source in the U.S. Additionally, it continues to grow. According to the U.S. Energy Information Administration, the U.S. went from generating six billion kilowatt hours (kWh) in 2000 to about 434 billion kWh in 2022. However, there is room to grow, especially in deep water offshore where it is prohibitive to construct traditional moored offshore turbines, according to a team of researchers led by Mark Miller, assistant professor in aerospace engineering. The group is investigating how to improve the design and affordability of floating offshore wind turbines.
“The idea with floating is that we get rid of the fixed element, and we make a buoyant platform so that it's literally floating in the ocean,” Miller said. “There are many promising areas for offshore wind in the U.S., but the water is just too deep to do a fixed base.”
Miller said there are numerous challenges that come with making a wind turbine float. The height of the structure can be 150 meters, about the height of the Washington Monument, and the rotor diameter can be over 200 meters, about the height of the Gateway Arch in St. Louis. Due to these sizes, engineers and scientists must be mindful of multiple challenges, including balancing the structure vertically while addressing the movement of the ocean, the movement of the rotor and the force of the wind.
In addition to engineering challenges, there are cost considerations. The estimate for floating offshore wind energy — because there are no operational floating offshore wind farms at this scale — is three times the amount of onshore wind. Additionally, until there is more confidence in floating platforms and the ability to install them, the cost risk is high.
“One of the interesting things about wind is that it has come down in price so much,” Miller said. “There's reason to believe the same will happen with floating, because the industry has been able to reduce the cost of onshore and offshore significantly in the past couple of decades, and that's only accelerating.”
The research team is using a unique wind tunnel that was recently brought online at Penn State. The wind tunnel is built inside a pressure vessel that can increase the atmospheric pressure inside the tunnel. The benefit of this is that a small 10-inch rotor can be tested in the tunnel, and the pressure recreates the exact aerodynamics of a 30-foot diameter rotor, Miller said.
“There's a big change when you go from that really small, 10-inch size at atmosphere up to 30 feet at full scale,” Miller said. “We get the best of both worlds when it comes to the scaling ability of this tunnel.”
Sven Schmitz, the Boeing/Welliver Professor in aerospace engineering, is a member of the research team. He said there are multiple reasons why society should be exploring additional offshore sites.
“I think part of the answer is that most of the good onshore wind sites have already been taken, and there's just a larger wind resource available offshore,” Schmitz said. “It also does not impact people with unpleasantries such as noise. Offshore can also have larger rotors, longer blades, and you can run them faster, which increases efficiency.”
The research team is also considering how to modify rotor blades so that they interact with the platform in a beneficial way.
“One of the concepts we are looking at is the so-called low-induction rotor,” Schmitz said. “What it means is that you design an aerodynamic turbine that does not maximize power but minimizes cost of energy. By sacrificing some power capture, we reduce the aerodynamic loads on the structure. This could make the floating foundation less heavy, less expensive, less complex, and it could reduce the overall cost of wind-produced energy."
"Growing Impact" is a podcast by the Institute of Energy and the Environment (IEE). It features Penn State researchers who have been awarded IEE seed grantsand discusses their foundational work as they further their projects. The podcast is available on multiple platforms, including YouTube, Apple, Amazon and Spotify.
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