Harnessing the gales of November
A young scientist leads the charge to tap the power of Lake Superior’s waves.
Every fall, 10-foot, storm-driven waves pound the Lake Superior shoreline near Duluth. Few people besides surfers benefit.
But at the University of Minnesota Duluth, Craig Hill and his team are engineering new ways to capture wave power. With 40 percent of the world’s people living near a coast, his work lays a basis to help them shift to a local, climate-friendly energy source. Waves may power, for example, marine observation stations, aquaculture, or desalination plants to provide freshwater for areas in need.
Aboard the research vessel Blue Heron, Craig Hill's research group deploys moorings on Lake Superior to estimate the energy available from waves and currents and engage students in multiple marine engineering field activities.
“We are exploring how much power is available in the waves on the Great Lakes, and how we can harness that power to create usable energy,” says Hill, an assistant professor in the Department of Mechanical and Industrial Engineering at UMD’s Swenson College of Science and Engineering.
No other Great Lake can match Lake Superior’s raw wave power, especially from September through May. For example, by tapping just 10 percent of the energy from those 10-foot waves along the half-mile shore between downtown Duluth and the Canal Park lighthouse over the course of 24 hours, “we’d realistically be able to generate enough power to support about 2,100 average Minnesota homes for a day,” Hill says.
“The challenge is to figure out how to efficiently harness this without causing harmful outcomes to the environment or society.”
Local initiative, national potential
Hill’s work aligns with the Department of Energy’s marine energy initiative, Powering the Blue Economy. And UMD is in an ideal spot to develop it.
Craig Hill's research is a prime example of the amazing discovery that's possible here at UMD. His exploration of wave energy, coupled with the accessibility of the tools and data that he's working with, can make an impact both locally and across the world. We're proud of the work that he and his students are doing, and can't wait to see the impact his research has in the future.
Charles Nies
Chancellor, University of Minnesota Duluth
Buoying up research
A central goal of Hill’s work is to build devices that convert wave energy into storable electrical energy. Such devices, called wave energy converters (WECs), would be deployed strategically to maximize the energy harvest.
One promising type of WEC could attach to existing infrastructure.
“That would provide a lot of unique opportunities to harness wave energy, protect harbors and/or communities, and contribute to the growth of this new interdisciplinary industry,” Hill explains.
As a computer science student, I’ve worried that I’ll find myself … focused on optimizing algorithms just to keep people glued to their screens. When I saw the opportunity to work on a project focused on clean energy and making a positive impact, I had to get involved.
Liam Gaeuman
Undergraduate researcher, Hill lab
Craig Hill's team is exploring WEC concepts such as point absorbers and oscillating surge converters. Design concepts for each vary, but both have advantages for extracting energy from waves, through either vertical "heaving" motion (first design in video) or horizontal "surging" motions (second design in video) as waves pass by. Diagrams courtesy of the US Department of Energy.
To turn this vision into reality, Hill and his team track conditions via existing small wave buoys while developing new, low-cost systems to monitor waves and water quality. And not just in Lake Superior. He envisions the new, compact buoys also being used to monitor water quality in smaller, inland Minnesota lakes.
“Our buoys currently cost about $2,000, while the big NOAA [National Oceanic and Atmospheric Administration] buoys probably cost upward of $50,000,” Hill notes.
The gales of November
With a graduate student colleague, Hill determined that Superior’s waves pack 10 times more power in winter than in summer. As winter conditions change, that gap could widen. For example, last winter, the Great Lakes had little ice cover. Winds blowing over long stretches of open water whipped up waves close to 15 feet high. Westerly winds, with their long “fetch,” make waves in the lake’s eastern section the strongest. There, winds generated both the Great Lakes’ largest reported significant wave height—nearly 29 feet—and those that sank the freighter Edmund Fitzgerald.
While ice makes winter data collection challenging, Superior is a natural laboratory for Hill to explore how WECs and buoys operate in cold climates and to develop technologies able to withstand icy conditions. As the Arctic sea ice thins, these devices, plus WECs integrated into buoys, will be crucial for navigation or other activities at high latitudes.
A pioneer’s vision
The Hill lab is also developing technologies to harness the energy of river and tidal currents. For example, Andrew Walz, a mechanical engineering graduate student, specialized in optimizing the performance of a dual-rotor turbine to capture that energy.
Still, the field of wave energy technology is in a pre-commercial state. For example, its effects on fish, aquatic mammals, and other organisms, plus the functioning of coastal sediments on which many depend, are unknown. And, as in the early days of wind power, the industry has barely begun to narrow the options for device architectures.
Its growth will rest on the work of pioneers like Hill and his colleagues to integrate wave- and current-driven technology into the grid or small communities on the shores of Great Lakes, rivers, or oceans. In his words:
“We are trying to use our local environment to attract developers and researchers to this area and take advantage of the conditions on Lake Superior, use our existing maritime industries to support their endeavors, and show how local work in Duluth and at UMD can translate to impactful actions around the world.”
