Tens of thousands of turbines anchored to the bottom of the Mississippi River could someday provide more than a gigawatt of renewable energy, enough to power a quarter of a million homes. That’s the vision of Free Flow Power, a startup based in Gloucester, Massachusetts, that recently received preliminary permits from the U.S. Federal Energy Regulatory Commission (FERC) granting it the right to explore energy production at dozens of sites along the lower Mississippi over the next three years.
The proposed development is one of a number of “hydrokinetic” projects in the works. Such projects seek to generate electricity from wave movement, tidal flows, or river currents, without the use of dams.
The ambitious Mississippi project, however, relies on relatively unproven technology. The only commercial hydrokinetic river-power system operating in the U.S. is a single turbine deployed by Hydro Green Energy close to a conventional hydropower dam on the Mississippi River in Hastings, Minnesota.
Free Flow hopes to deploy hydrokinetic power on an unprecedented scale: hundreds of 40-kilowatt turbines, each the size and shape of a large jet engine and attached to pylons jutting out from the riverbed at 88 locations along the Mississippi.
Although most companies developing hydrokinetic technology have focused on tidal or wave energy, Free Flow’s chief financial officer, Henry Dormitzer, argues that river power has distinct advantages. “The water flows in one direction, it doesn’t have salt in it, and, in the case of the Mississippi, people have spent 100 years tracking water flows and velocities,” he says.
But the Mississippi is also one of the world’s busiest waterways, and the company will have to demonstrate that its turbines will not interfere with commercial shipping, and that it will have no negative impact on the river’s wildlife.
In July 2009, Free Flow began a six-month test of a pilot turbine (a third the size of the planned commercial ones) in the Mississippi, and the company is now testing a commercial-scale prototype in the lab. Free Flow has also received $7.4 million in funding from investors and from the U.S. Department of Energy that will allow it to test its most recent prototype in the Mississippi next year. Free Flow Power is seeking additional funding to test four turbines, each attached to a separate pylon, over a 12-month period, as required by FERC as part of the licensing process.
Free Flow uses a “shrouded turbine” design that channels water through the turbine’s blades. Water passes through a rotor with seven blades that are designed for a slow spin rate to minimize fish strikes. The turbines will be sited 10 or more feet off the riverbed. At this depth, water moves, on average, at one to three meters per second.