Reaping renewable energy from un-dammed portions of great American rivers like the Mississippi, Ohio, or even the Columbia is an idea that has been bandied about for decades.
But only now is the turbine technology set to make these possibilities a reality — it is being fine-tuned for deployment in both small rivers that flank Alaska’s Great White North as well as along a portion of the massive St. Lawrence River and Seaway that separates New York State from the Canadian province of Ontario.
The idea is to harness the hydrokinetic energy of a swiftly-moving freshwater river with underwater turbines, all without significantly impacting the riverine environment.
“Moving water impacts the turbine’s foils to give it lift just like an airplane,” said Chris Sauer, CEO and President of ORPC (Ocean Renewable Power Company), headquartered in Portland, Maine. “This lift rotates the turbine and generator. It’s like hydro without the dam.”
ORPC is targeting its first freshwater hydrokinetic operation in Igiugig, Alaska on the Kvichak River, some 800 miles southwest of Anchorage.
With a year-round population of only a few dozen people, diesel fuel at 80 cents per kWh or above, remains the village’s sole source of fuel to generate its needed 25 kW of electricity. ORPC’s prototype two-turbine Riv-Gen power system, which can operate in depths of 15 feet or more, would connect into Igiugig’s grid directly.
The Alaska Energy Authority is providing 80 percent of the $1.9 million in funding for the Igiugig Riv-Gen Power System project, with ORPC providing the remainder.
Necessary minimum flows range about 2.5 to 3 meters of water per second; not exactly the slow pace of the lazy Mississippi, but something less than the fast-paced surface rapids found in some western rivers like the Snake.
“We’re going to do preliminary testing of that system in Anchorage’s Cook Inlet this summer,” said Sauer. “A year from now we’ll ship it to Igiugig, install it and interconnect it to their diesel micro-grid.”
Unlike tidal and wind energy, in theory, river flows are not only predictable but available 24/7. But in Alaska, that’s not always the case.
During winter, the entire Alaskan land mass freezes; causing river flows to decrease dramatically, says Dennis Witmer, a Spokane, Wa.-based independent energy consultant for the Alaska Center for Energy and Power (ACEP).
And during stormy weather, river debris can wreak havoc on any hydrokinetic operation. In fact, as much as 60 percent of a hydrokinetic operation’s costs are wrapped up in anchoring, deployment, maintenance and repair.
“Unlike tidal hydrokinetics, in a river situation you have no slack time,” said Witmer. “You’re always working in a current and if the current is strong enough to generate power, it’s strong enough to be dangerous.”
That’s a lesson that Alaska Power and Telephone (AP&T) learned the hard way three years ago, during deployment of its Eagle, Yukon River Hydrokinetic Project.
“We got the project’s 25-kW-rated river turbine unit established in the Yukon River and generating 17-kw of hydrokinetic energy feeding the towns of Eagle and Eagle Village,” said Mark McReady, director of marketing at Alaska Power and Telephone. “But within 24 hours, a significant rain event upstream sent whole trees downriver, creating insurmountable difficulties.” Thus, the project was abandoned.
Witmer says such slushy curtains of ice crystals mixed with water can wipe out any structure in front of it.
However, even though the Kvichak River at Igiugig does not freeze over, Monty Worthington, ORPC's director of project development in Alaska, says it will still be necessary to understand such frazil ice phenomena on colder days. But he notes current flow rates are high enough to be viable throughout the winter period, and the climate is not as extreme as in Alaska’s interior.
In contrast, most Alaskan rivers have around 130 days of viable Riv-Gen deployment, says Worthington.
Even so, the issue of frozen rivers in the far North only highlights the potentially tenuous nature of operating in high-flow areas.
“There's not that much cross-sectional area available in rivers for turbine rotors, particularly in the areas of high flow,” said Brian Polagye, a mechanical engineer at the University of Washington in Seattle. “This makes it difficult to get the same economies of scale in devices, turbine foundations, and cabling that you can for individual rotors in a tidal or ocean current environment.”
Thus, New York-headquartered Verdant Power is taking a slightly more ambitious approach in its first potential foray into fresh-water hydrokinetics.
However, since 2009, Verdant Power Canada has been conducting a resource assessment of the St. Lawrence River, adjacent to the St. Lawrence Seaway at Cornwall, Ontario and downstream from Ontario’s Saunders power station.
The aim is to determine whether to proceed with its proposed CORE (Cornwall Ontario River Energy) project, which could potentially generate as much as 5 MW of hydrokinetic energy for the Province of Ontario’s grid system. If the $15 million project sees fruition, it would involve deploying some 60 turbines in a 50/50 funding partnership with the Ontario Ministry of Research and Innovation.
“We’re in the St. Lawrence River where there’s no commercial vessels,” said Trey Taylor, President, Verdant Power Canada. “The tip of the turbine rotor would be about ten feet down from the surface, although the system itself will be anchored to the bottom [or] about 40 feet down.”
Taylor says that although a decision about proceeding with the CORE project will be made within the next six months, he says it would then take another two years until it began full operation.
The key to maximizing hydrokinetic electricity, says Taylor, is to make sure that the turbines are placed within the river’s core current, which typically lies a few feet below the surface and sometimes moves as much as 1.5 times faster than surface currents.
As for ORPC’s riverine future outside Alaska?
The goal is to prove the Riv-Gen technology in Alaska and Canada, says Sauer, before taking it to developing nations in South America and Asia, where some areas still have no power whatsoever.
“In five to ten years our costs are going to come down dramatically,” said Sauer. “But we see our initial market as the high-cost areas.”
Although, currently the generation of hydroelectric power from dams is more efficient than hydrokinetics, these underwater turbines could also offer environmentalists and renewable energy advocates a point of compromise here at home — one that could stave off future dam projects while still offering new renewable sources of electricity.
“New dam construction is now constrained,” said Paul Jacobson, a senior project manager for the EPRI (Electric Power Research Institute). “So if there’s a resource that can be exploited without adverse impacts, conventional electric utilities will eventually be interested in this.”
As for concern about aquatic life and fish populations, Sauer is quick to point out that thus far, environmental studies for riverine hydrokinetics look promising.
“But we’re not starting with the Columbia River because you’d be picking a fight,” said Sauer, in reference to Oregon’s active environmental lobby. “Part of the site selection criteria is picking sites that are less sensitive.”
However, aside from environmental issues, riverine hydrokinetics is still not competitive with conventional hydropower generation in the continental U.S.
Although that could change within a few short years, Sauer says in the interim the whole idea is to make the technology efficient enough to be practical for slower-flow rivers, like the Mississippi and Ohio.
If that happens, he says riverine hydrokinetics could ultimately make up as much as ten percent of the U.S.’ current electricity budget. “That’s not an insignificant piece of the puzzle,” said Sauer.
Lead image: River in Alaska via Shutterstock