A renewable energy source that could serve the majority of the U.S. population often flows by unnoticed, even as it continuously rolls and crashes onto the shores of a country searching for petroleum alternatives.
Electrical and Computer Engineering PhD student Jennifer Vining has brought the attention of Wisconsin Electric Machines & Power Electronics Consortium researchers to the sea. “Water is much more energy-dense than air, and you can feel this when you’re swimming, because it’s more difficult to pass your arm through water than air,” Vining says. “As such, a unit area of ocean has the ability to produce far more energy than the same area of wind.”
One of the most common types of ocean wave energy converters is known as a point absorber, which is a buoy-like device that heaves up and down with the waves. The point absorber is connected to a generator, which typically sends power via undersea cables to a substation on shore.
Waves produce a linear heaving motion in point absorbers, and current devices convert this energy into rotational motion to drive conventional rotary generators (like wind turbines). Commercial solutions for this conversion process include hydraulic intermediaries, which decrease system efficiency and reliability.
Vining decided to eliminate the problems with these intermediaries. She modeled, constructed and tested a new class of linear generators that are wound-field devices, meaning the generator field is composed of coils, rather than permanent magnets, which are made from rare, expensive materials. Vining’s generator could be made from more common, ocean-friendly materials, such as copper and iron. “Developing an efficient means for extracting energy from wave motion is poised to be the next research challenge in the field of electrical power,” says Grainger Professor Emeritus of Power Electronics and Electrical Machines Thomas Lipo. “Jennifer’s PhD on new wave motion generators introduces an important alternative and clearly places UW-Madison at the forefront of this rapidly developing technology.”