Combining rivers and tides

Just as it seems like solar is about to turn the corner, wind power technology is out of its adolescence, and even Biodiesel has its own day (March 18th, Rudolf Diesel's Birthday), there isn't much left to do but twiddle our thumbs and wait around for these technologies to be refined and adopted. The people at Verdant power have other ideas. They have developed riverine, or tidal, 'kinetic' hydropower. It requires no damming or redirection of water, and uses relatively small slow spinning turbines which resemble wind turbines. They are currently testing it in New York City's East River, powering a parking garage and a supermarket on Roosevelt Island. The technology is clean, out of sight, and the New York State Energy and Research Authority (NYSERDA) has identified over a Gigawatt (1,000 Megawatts) of potential capacity in the state. California has identified over 1.5 Gigawatts of potential (put into perspective, 1 GW is enough power to run approximately 1 million homes).

Verdant's turbines take advantage of not just the run of river kinetic energy, but power generated by tidal forces. They estimate that tidal power can run at capacity around 41% of the time, and the flow of big rivers can run between 80 and 90%, which is far beyond was many windfarms are capable of sustaining. More important than the sustained generation is the predictability with which it is accomplished. Wind and solar power are subject to the whims of the weather, while tidal power is tied directly to the gravitational forces of the sun and moon which are predictable a thousand years in advance.

Possibly the most interesting thing about this form of hydropower is its unobtrusive nature. Visitors to Roosevelt Island who want to see the installation will be disappointed - there is nothing to see, not even a water wheel. To contrast, hydroelectric dams flood river valleys, wind turbines have what some people refer to as a destructive force on scenic vistas, but the installation in the East River is only in sight of the few fish that live that part of the river. The people of New York City can't see it, hear it, or smell it. This unobtrusive nature, and the capability to scale the installation to the size of the population it serves by controlling the number and size of turbines makes this design a perfect compliment to any city or town with sufficient running water or available tidal area.

However great the technological potential for kinetic hydropower is, there are still many questions to be answered as far as wildlife issues are concerned. Those effects are under study in the East River now, but in that area of the river there are few fish to disturb, and possibly be killed by the spinning blades. The generator's turbine spins relatively slowly, but the tip speed of the blades can be enough to easily kill a large fish. As with wind turbines, wildlife must be carefully studied before these generators ever make it into the water.

What we do know, is that the generators are clean, and take advantage of a plentiful natural resource. It remains to be seen if they can stand up to the physical stresses, or the approval processes they will be subject to.