Yet a Massachusetts-based company hopes to do just that by 2013 and has secured preliminary permits from the Federal Energy Regulatory Commission for 55 proposed sites in seven states - including nine in Arkansas.
To learn more about the "hydrokinetic" generators envisioned by Free Flow Power Corp., residents near two sites near Helena-West Helena and the Memphis-West Memphis metro area were invited to public hearings Monday and Tuesday at Memphis' Cook Convention Center.
Barge operators at the Monday hearing were skeptical of a basic premise behind the estimated $3 billion project - that underwater turbines and vessels with thousands of tons of cargo could share the same channels without their striking or otherwise impeding river traffic.
"What physical changes would these structures have on the current?" asked Steve Crowley, executive vice president of Paducah, Ky.,-based Marquette Transportation, which operates 110 tugboats along the Mississippi. "What is the minimum clearance they would have?"
Free Flow officials said each turbine array would need at least 10 feet of river bottom clearance but only the deepest channels are considered viable for the project.
Crowley noted that since 1989, there have been 1,365 days when the Mississippi River has been at zero gauge or below at Memphis. He added that the average depth from Cairo, Ill., to Baton Rouge is about 12 to 14 feet.
"We hear you loud and clear," said Ramya Swaminathan, vice president of project development. "We're working on data right now to determine where the pockets of depth are. We don't want you to hit us, either. So we're trying to figure out where to be so it doesn't interfere with commerce."
The Mississippi offers potential as an alternate energy source, said Jon Guidroz, Free Flow's director of project development.
Dam building is impractical because it would impede barge traffic, he said. But the Mississippi has qualities that make it ideal for the underwater turbine project.
"We've screened more than 80,000 sites, and in terms of velocity and flow, it all comes back to the Mississippi," Guidroz said.
As a result, Free Flow would like to put in about 600 turbines a mile in areas along the Mississippi able to sustain an average flow of 2 meters per second.
Each turbine would produce up to 40 kilowatts each, with a maximum collective output of 7,200 megawatts - though average generation is envisioned at 1,800 megawatts, Guidroz said.
Most turbines would be deployed in rows secured to the riverbed beneath surface traffic.
Individual pylons would support six to 10 turbines each - some mounted vertically in deep areas, others horizontally in shallower spots, he said. Additional methods include attachments to bridge abutments and river banks or suspension from a floating platform.
The blades are designed to spin slow enough to protect fish and other aquatic life yet endure the constant intake of mud and impacts from logs, tires and other debris. Made of polyethylene, the blades are the turbine's only moving part and would require no lubrication, Guidroz said.
Yet another Marquette employee warned that Free Flow may be underestimating the Mississippi's immense power.
"The damage can be phenomenal just from a tree stump. Then there's the abrasion with all that sand and silt," said Leo Visser. "You better have a serious budget for repairs. In fact, it really is a stretch to see how this kind of project is even feasible."
Free Flow officials remain unbowed, noting that entire pylons can quickly be replaced from a maintenance barge.
"We expect a lot of debris. If we don't see it, we'll be disappointed because we've spent a lot of time designing for it," Guidroz said. "If a barge hits them, they can easily be brought up by maintenance crews and replaced. They're not disposable by any means, but they're very cheap."
Free Flow still cannot say for certain whether it will have the money to test its second-generation turbine in actual river conditions.
Free Flow has successfully tested its first-generation turbine in a freshwater tank, Guidroz said. The next step is a larger turbine that can produce 10 kilowatts of electricity in 2.25 meters of muddy Mississippi water flow per second.
The company has been in touch with some utilities, including New Orleans-based Entergy Corp., about the possibility of tapping the turbines' power, though Guidroz describes their reaction as "an optimistic wait-and-see."
Although the company says it's too early to give specific figures on how cost-competitive its turbines can be, Guidroz projects they will be "much more" competitive than wind or solar power.
At present, Free Flow is in the middle of a three-year "pre-approval" licensing phase, which only ensures that the company will be "first in line" to develop such a project, he said. The Memphis hearings were part of a "scoping process" by FERC to determine factors in considering environmental impacts and additional permitting, said Sarah Florentino, a FERC project cocoordinator.
If fully developed, the economic impact of Free Flow's project would center around 4,000 jobs throughout its seven-state system, ranging from manufacturing turbines to maintenance and operations, Guidroz said.
"All of this started in 2007, and if it stays on schedule, we should see construction around the end of 2012," he said. "There's no hierarchy of construction, but we wouldn't build all 180,000 turbines at once, either. A lot of it depends in feasibility of placement, what's nearby on shore, utilities or loading on the grid. All of that is a little difficult to determine right now."
One factor that may play a key role is the recent stimulus package produced by the Obama administration that calls for a 30 percent tax credit for qualified hydroelectric projects by the end of 2013.
"It's no coincidence that that we're hoping to get it on line by 2013," Guidroz said.
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