While big hydroelectric power projects attract more protestors than investors these days, days, new developments in river-run, hydro power could prove there’s more than one way to get clean energy from water.
River-run, hydro systems, also called hydrokinetic power, sit in running waterways like rivers, irrigation canals and even wastewater ditches, and generate power without needing to build a massive dam that interrupts water flow completely.
That allows other users of the waterway—from ships to fish—unobstructed access while power is generated.
“[Our] systems can be applied to each river's environment, culture and commercial activities as seamlessly and invisibly as possible,” says Chris Catlin, president of Bourne Energy, a California-based firm building hydrokinetic power equipment.
He adds the always-flowing nature of these waterways makes hydrokinetic power more reliable than other renewable energy sources.
“The river runs when the wind dies down and when the sun goes down,” he says.
Hydrokinetic technologies, including Catlin’s, typically use some form of turbine placed in the water stream, and look like a boat motor or an underwater windmill.
Energy generated is sent to shore via transmission lines built into the turbines’ tethering system.
A river flowing at 2.2 meters/second can generate 1.5 kilowatts of electricity per every hour. Doubling that speed—not unusual in some rivers—generates up to 8 kilowatts per hour.
“Water down a river is much different than wind,” says Catlin. “It’s more dense.”
Smaller generation units are deployed as a array—either spread out over a wider area in the river, or stacked vertically if water depth allows—to generate enough power to be provide utility-scale amounts of power.
Widespread use of hydrokinetic energy, however, faces two big challenges: A lack of ways to get the power to market and a tough operating environment.
A report from energy consulting firm Navigant Consulting says the potential energy resources from flowing rivers in the US is four times the current output from hydroelectric dams, which currently provide about 7% of the nation’s power.
But while resources may be large, the national transmission grid is more limited.
“Rivers and ditches are a lot easier to build in than the ocean,” says Michael Kanellos, researcher and editor-in-chief at research firm Greentech Media/GTM Research, comparing the two experimental-phase, water-power renewable energy sources. “But often watercourses are in places without transmission.”
And the energy density praised by Catlin is tough on equipment.
Wear and tear is inevitable with any hydrokinetic technology, says Catlin says, who says Bourne's designers have partly addressed that issue by making the replacement of gear as easy as possible. “They’re a sealed unit cooled by water,” he says of Bourne’s technology. “It can be pulled out and replaced and have the other [turbines] continuing to run.”
To date, the amount of river-run hydro power being generated can be measured in kilowatts; the technology is experimental and small-scale.
A Canadian firm, Run of River Power Inc., has been contracted to install the biggest planned hydrokinetic plant to date, a 25-megawatt array in British Columbia.
That's tiny compare to the 80,000 megawatts of current hydroelectric power capacity in the US—the cheapest and most plentiful renewable energy available to the nation today.
The problem is hydro electric plants typically do not qualify for state renewable energy mandates, and public opposition over environmental impacts have made these projects even more unpopular than new coal-fired power plants.
So, while the U.S. has the world’s fourth-largest capacity of installed hydropower today, not one of the top 25 planned or under-construction hydroelectric dams is in the U.S. (almost all are in China.)
Hydrokinetic plants can help fill that gap, says Caitlin. Plans are also in place to use them in conjunction with existing hydroelectric plants, using the spillway water or the head-pond flows behind the dam to add additional energy.
“Near-term opportunities exist because you’re adding to an existing dam,” says Peter Asmus, analyst with cleantech research firm Pike Research. He adds that this approach solves both the location and transmission issues facing hydrokinetic power, since it can use the hydroelectric plant’s resources.
But while there may be a lot of potential flowing water to tap for this energy, the constraints of transmission and access to flowing water means “it’s never likely going to be something huge,” says Pike’s Asmus.
Most likely, it’ll look like the residential solar energy space -- with a few companies, similar to Akeena Solar, focusing on installing small projects that let homeowners, farmers, or businesses offset their grid power usage by installing river-run systems.
“It could be a cottage industry in ten years,” adds Greentech’s Kanellos. “It could be a successful niche for a few companies.”