Case Study: The Benefits of Small Hydro in Boulder, Colorado
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With good reason, hydro-power has gotten a bad rap from the environmental crowd over the years. Large-scale dams obliterate the ecosystems that exist both upstream of the dam and down. But hydro-power shouldn’t be discounted based solely on the faults of massive dams. Small-scale hydro power (and micro-hydro power) can be (and should be) a key element in the re-localization of our power infrastructure in this country. Think of all the water-powered mill buildings you’ve seen along the roads with broken windows, dirty bricks, and raging rivers. These old properties can make local power.
Boulder, Colorado recognized that hydro-power doesn’t always mean the destruction of ecosystems. By rethinking their local water resources, the city has been able to generate much of the power they need, in an innovative way that benefits the citizens and the environment.
The following is an excerpt from The Citizen-Powered Energy Handbook: Community Solutions to a Global Crisis by Greg Pahl:
Large dams have definitely fallen out of favor in the United States in recent years; almost two hundred have been demolished since 1999. While only a few of these dams were ever used to generate hydroelectricity, their removal reflects a general trend toward river restoration initiatives in many communities. Despite the decline in the fortunes of large-scale projects, there has been a recent surge of interest in small hydro nationwide. Driven by high energy costs, a number of federal incentives, and an eased licensing process contained in the Energy Policy Act of 2005, at least 104 small hydro projects in twenty-nine states have been given “preliminary permits” by FERC recently. These projects have a combined generating capacity of 2,400 megawatts, but even more projects are reportedly in the works according to industry observers. “I have noticed a trend of what I call ‘incremental hydro,’ where people are adding a new generator or a new powerhouse to an existing facility,” says Fred Ayer from the Low Impact Hydropower Institute. “There is a great deal of interest and activity in that right now.” Most of these recently proposed projects are small—producing less than 20 megawatts of power. But if all 104 projects were built, they would make a substantial contribution to the nation’s hydroelectric generating capacity. And if most of the approximately 77,000 dams that do not currently generate electricity were retrofitted to do so, they could generate as much as 17,000 megawatts, according to a recent U.S. Department of Energy report.
The growing interest in smaller hydro projects has resulted in some interesting developments. As I mentioned in the last chapter, municipal (public power) systems in the United States have led the industry in renewable energy production, including wind, solar, geothermal, landfill gas, biomass, and—especially—hydropower. Public power, in fact, leads all other power producers in the percentage of hydropower in its portfolio with over 21 percent, compared to just over 6 percent for investor-owned utilities, and 2.5 percent for co-ops and nonutility generators. This strong emphasis on hydro largely reflects the development of local hydropower sites by communities in the early days of the electric industry. However, since many of these communities developed their hydro sites over one hundred years ago, the potential for additional large-scale municipal projects is rather limited in most parts of the country.
There is, however, one category of community-owned hydropower that has not been widely exploited: municipal water systems. These systems offer a lot of smaller-scale opportunities, according to Johnny Weiss, executive director of Solar Energy International in Carbondale, Colorado. “Often communities have existing infrastructure that could be used or adapted,” he says. “For example, Carbondale has a municipal water line that comes down from its source in Nettle Creek. This water line has a lot of pressure that could be used for electrical generation. I think people should look at existing infrastructures and explore what opportunities they might have to make more productive use of them. When they upgrade that infrastructure, that’s a good time to think about micro-hydro.” In addition to its many course offerings in solar energy technologies, SEI also offers regular workshops on micro-hydro design and installation.
Boulder, Colorado
The city of Boulder, Colorado, has taken advantage of this combination strategy, and eight hydroelectric generators incorporated into the city’s municipal water system now generate enough power to provide 11 percent of the electricity needed by the city’s 96,000 residents. Five of the turbinegenerator units, with a combined rated capacity of 4.1 megawatts, were installed between 1985 and 1987, with one on a raw-water (natural water prior to treatment) transmission pipeline and the other four within the city’s water-distribution network. In 1999 and 2004, two more turbinegenerators were installed on raw-water transmission pipelines that together provide an additional 6.2 megawatts of generating capacity. A third turbine- generator was purchased from a local utility in 2001 and has 10 megawatts of generation capacity. Boulder’s main water supply originates from Boulder Creek in the mountains high above the city and is fed by gravity to the distribution system. Because of the high pressure resulting from the long drop, pressure reducers are needed in the supply lines. The turbine-generators were installed to bypass the pressure-reducing valves. The older generators are rated from 68 up to 800 kilowatts, while the newer units are rated at up to 3.1 megawatts.
From 1990 to 1998, the city’s hydroelectric stations generated an average of 15.5 million kWh per year. Including the newer generators, that figure has risen to 42.5 million kWh in 2005. The total installed cost of the first
five generating plants was $5.2 million, while the cost of installing the additional two turbine-generators was $6.6 million. In 2005, Boulder received $1.7 million from the local electric utility for the hydroelectricity the city produced. Boulder’s total revenue from hydropower sales since the beginning of the project is $16.6 million. The environmental impact of the project was minimal, since the water-supply infrastructure was already in place. “That’s what makes all of these turbines economical; they are being added to an existing water system,” says Carol Ellinghouse, Boulder’s water resources coordinator. “And because it’s such a huge drop from where we gather the water down into the city, we have to reduce the pressure somehow, and installing a turbine makes sense both from an engineering and financial standpoint.”
The city did have one problem with its hydro project, however—finding the turbines and generating equipment. “We’ve had to look all over the world to get the equipment for these systems,” Ellinghouse notes. “We have turbines from England and China and mechanical equipment from Spain. Europe in particular has really moved ahead of the United States with small-hydro technology, and it’s really hard to find equipment for this kind of application here in this country.” Nevertheless, the hydro project has been so successful that the city is continuing to explore additional hydro
potential, and has identified several more sites on municipal water-supply facilities. “It’s been a fantastic program,” Ellinghouse says of the hydro project. “We’ve not only made money that offsets the cost of the water supply for our citizens, but we’ve also offset an awful lot of coal burning that otherwise would have had to take place.” Boulder’s hydropower project is estimated to have displaced the need to burn 170,000 tons of coal since the first generator went online. Several other cities such as Denver and Colorado Springs have similar municipal water/hydroelectric systems.
The potential in other cities and towns across the nation and around the world is substantial, and a company called Rentricity was formed in 2003 to promote the idea. Headquartered in New York City, the company uses a proprietary system to transform the energy of flowing water (and potentially other materials) in pipes into electricity. A single system can produce between 20 and 300 kilowatts. So far, the company has three projects in Connecticut and Rhode Island and has begun to expand into Pennsylvania.
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