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Exploring the Future of Wind and Hydrokinetic Energy

Oct 23, 2013   |   by Kirsten Mabry   |   TriplePundit

Brenden Epps
Professor Brenden Epps

Brenden Epps is an assistant professor of engineering at Thayer School of Engineering at Dartmouth. He is currently researching fluid mechanics as related to marine propulsion, wind energy and hydrokinetic energy.

Kirsten Mabry: What triggered your research focus on wind and hydrokinetic energy?

Brenden Epps: Energy is the foundation of human society. Each leap in energy technology—from fire, to the steam turbine, to renewables—brings with it a revolution in the way humans live. I believe that we are in the midst of another revolution, moving towards sustainability as a way of life. Renewable energy technology will get us there. Why study wind and hydrokinetic? Those technologies combine my love of fluid dynamics with this important problem of providing energy for a sustainable society.

KM: How does hydrokinetic power work as a source of renewable energy?

BE: Hydrokinetic power is the production of electrical power via flowing water in rivers or tidal estuaries. It is the underwater analog of wind power. In either wind or hydrokinetic, the flowing fluid spins a turbine rotor (which might look like a propeller). This rotor uses lift and drag forces to create torque that drives an electric generator.

KM: What are the goals of your research?

BE: My goal is to efficiently and cost-effectively harness wind and hydrokinetic energy in the U.S. as viable renewable energy sources. Broadly speaking, my research lies at the intersection of fluid dynamics and energy. With a focus on blade design and the aero- or hydro-elastic behavior of the blades, I am developing open-source computational engineering tools that can be used for the design and analysis of offshore floating wind turbines. That is, how the blades flex in response to the lift and drag forces they feel during operation. I do both numerical model development (i.e. writing computer programs to calculate these forces and deflections) as well as building and testing scale-model prototypes in order to characterize the behavior of these turbine systems in unsteady wind and waves.

KM: How is your research leading to a more economical, cost-effective way to harness wind and tidal energy?

BE: With more confidence in our simulation and design tools, turbine designers can optimize blade shape and reduce mass and cost. They can also develop smarter blades and control systems that mitigate peak unsteady loads during unsteady winds and tidal flows.

KM: What is the potential of tidal and wave technologies to meet a larger percentage of U.S. energy demand?

BE: Hydrokinetic power is attractive due to its abundance, particularly near population centers. It is estimated that 370 TWh/yr (terawatt-hours per year) of hydrokinetic power is available from rivers and tidal currents in the United States, which equates to about 9% of the total annual U.S. energy demand. An additional 1,170 TWh/yr (29% of US energy demand) is available from wave power (DOE EERE Water Power Program, 2013).

KM: What is the commercial viability for hydrokinetic energy?

BE: The hydrokinetic power industry is still in its infancy, with few devices in the water or utility scale projects. Two companies are leading the commercialization efforts in the United States: Verdant Power is scheduled to have 30 axial flow turbines (which look like underwater wind turbines) operating in the East River by 2015, supplying over 1MW of power to New York City residents; Ocean Renewable Power Company is in the pilot phase of a project that will eventually create 4MW of power for coastal communities in Maine. If these projects are successful, we could see more devices deployed in rivers and tidal estuaries around the country.

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