Micro-Power Hydro: An Energy Alternative Whose Time Is Coming

Kansas is not a state that’s known for its water resources. In fact, when European settlers first reached this region, it was a semi-arid, treeless plain of grass. In 1931, when historian Walter Prescott Webb wrote about the settlement of Kansas, and other Great Plains states, he described “the search for water” as a “continuous and persistent” issue.

It’s not terribly surprising then to learn that Kansas has only a trifling supply of hydroelectric power. Throughout the whole state, the annual mean in production is just 1 megawatt * – enough to power fewer than 800 homes, or roughly 0.01 percent of the Hoover Dam’s nameplate capacity.

But Kansas has the potential for much more. In fact, the state could be getting almost 300 megawatts of electric capacity from water power – enough electricity for 240,000 homes. The key: That potential is only accessible if you’re willing to think local.

Across the United States, changes are afoot that are making smaller-scale energy generation make appealing. One of the major benefits of this localized power is that it enables us to take advantage of renewable resources that were previously out of reach. This is particularly true for hydroelectric power. In fact, without smaller scale generation, hydro doesn’t have much of a future at all.

A dramatic shift

The United States really can’t build many more large-scale hydroelectric dam and reservoir systems. According to the U.S. Geological Survey, there weren’t enough good reservoir locations to supply all of the energy the United States consumes. What’s more, the best spots are already being used.

Amoskeag Hydro Station, Maryland. Capacity 16 MW. Courtesy Flickr user PSNH

In 2006, though, the Department of Energy (DOE) released a paper that took a second look at the potential for hydro power in the United States. It paid serious attention to places where you could make electricity without building a dam.

These sites identified by the DOE would all have capacities of less than 30 megawatts, with some less than 1 megawatt–in contrast to large hydroelectric dams, which usually have capacities of hundreds and thousands of megawatts. What these new sites lack in size, however, they make up for in numbers. The study found 5,400 sites in forty-nine states where dam-less hydroelectric power could be developed in a practical way. Taken together, the sites represent as much as 18,000 additional megawatts of electric capacity we could be using but currently are not. It’s enough to increase the total U.S. hydroelectric capacity by 50 percent —something that wouldn’t be possible to do if we focused only on developing more large hydroelectric dams.

This would require a dramatic shift in the way we think about energy. In fact, for the better part of the 20th century, it made much more economic sense to build large power plants, facilities that can serve millions of homes. But that is starting to change.

Limits to centralized plants

Electricity is a commodity and we make it in bulk. More than 95 percent of our electric generation (pdf) comes from what are called “centralized” power plants (pdf). These are large facilities–most have hundreds of megawatts of capacity each–and they’re located far away from the people who actually use the electricity they produce. Centralized power plants include those that feed on coal and natural gas, but we make renewable energy this way, as well. In 2009, according to the U.S. Energy Information Agency, 7 percent of our electricity came from hydroelectric power and almost 90 percent of that came centralized hydroelectric power plants (pdf).

Centralized generation is cheaper because it creates economies of scale – you need fewer facilities to serve the same number of customers. But there is a catch. When you centralized electric generation, you have to build a lot of transmission lines to move the electricity to customers.

“That means you have to deal with more people,” says Neal Elliott, associate director for research at the American Council for an Energy Efficient Economy. “You can buy your neighbors out to build a power plant, but it’s harder for the transmission lines. You’re talking about thousands of landholders, any of whom can sue you. In many cases, you’re talking about crossing federally protected lands.”

All of that adds cost. Today, say experts like Elliott, it can actually be more expensive to build the transmission lines that feed a centralized power plant, than it is to build the power plant itself. This economic case opens the door for smaller-scale generation that can serve thousands, or hundreds of thousands, rather than millions.

East River hydro

Economic opportunities for smaller-scale electric generation mean opportunities to build more hydroelectric power plants. These dam-less hydroelectric power plants can take many forms, but generally they involve finding ways to use the natural movement of water in a river to electricity generating advantage.

A Verdant Power turbine installed in New York's East River in 2006. Courtesy Verdant Power Inc.

Some of these systems are modern takes on very old-fashioned ideas. The first hydroelectric power plant in the world worked by putting a wheel into the free-flowing Fox River in northern Wisconsin. The river turned the wheel, and that motion operated the electric generator. Some run-of-river hydroelectric systems operating today work in much the same way. Often, these projects involve digging a channel, which diverts part of the river through a hydroelectric power plant. Water runs through, spinning the generator turbines, and then gushes out the other end of the channel, back into the river.

Other options are more futuristic. For instance, a company called Verdant Power ran a demonstration project unlike any hydroelectric power plant in the United States. This system turned the motion of water into electricity with the help of what looked like a wind farm that got lost on its way to the field. The company built a series of triangular platforms, each dotted with several skinny poles, and each pole topped with a rotating fan, similar to the propellers on the wings of a small airplane. Then, they sunk the platforms in New York City’s East River.

As river water flowed by the poles, the blades of fans slowly turned, producing electricity. The five-turbine, 175-kilowatt pilot program spun away under the East River for nine thousand hours, off and on, between December 2006 and September 2009, providing power to a parking garage and the only grocery store on Roosevelt Island. No one generates power commercially like this today but the system is simple and effective. The company is currently in the process of building a larger system, with thirty turbines grouped into sets of six. It will have a generating capacity of 1 megawatt.

* Number reflects Department of Energy energy production data, not total capacity as stated in an earlier version. Total capacity is about 2.35 MW.

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