Q. Dear Umbra,
Please tell me you didn’t just imply that hydroelectric is a clean energy source. You didn’t just say that, did you?
Brian K.
Eugene, Ore.
You’ve got the power in your hands.iStockA. Dearest Brian,
In my recent column on living off the grid, I pledged to discuss micro-hydro as a power source for homeowners. Your question, which dates from a while back, is the most related I could find in my inbox—although it sets a bit of a sad and awkward tone. As Brian suggests, large-scale hydropower is a renewable energy source that does have problems. Problems such as habitat destruction and forced relocation of entire communities. I welcome more questions about large-scale hydro, but let’s not think about those sad things today. For now I want to give a brief overview of micro-hydro.
Micro-hydro power is less environmentally destructive than regular old hydro, and a feasible way for some of us to produce our own electricity. Admittedly, it’s not hard to be less destructive than the Grand Coulee dam. With small hydro in a backyard stream, there is likely no need to dam or even seriously divert the flow of water, much less relocate sacred burial grounds or doom an entire salmon run.
In a micro-hydro system, falling and moving water is funneled into a tube and diverted to a turbine. The turbine powers a generator, which in turn either feeds directly to your home energy needs and storage batteries, or goes into the power grid. This aquatic idea should be familiar to those of us who dimly remember our exploration of tidal and wave power. Hydro power can be fairly constant, which is not true of wind or solar power; and it can potentially produce more energy in the winter months, when humans generally need it.
The key aspects to micro-hydro potential include the “flow,” which is the amount of water in a stream (or other moving body); the “head,” which is the vertical drop between the water intake area and the turbine; the distance the water must travel in pipes between the intake and the turbine; and the distance the resultant energy would need to travel to get to your home or other place of energy use. Fun jargon: the pipeline from the intake to the turbine is also known as the “penstock.” The intake can be as simple as a small box covered with a slanted debris screen, with the penstock pipe reminiscent of home plumbing piping emerging out of the box side.
Logically, the bigger the head and/or the heavier the flow, the more potential power one can get out of a water body. The potential watt output is equal to the feet of head multiplied by the gallons per minute of flow and divided by ten, according to one calculator. Or here is a handy chart, which indicates that 25 feet of net head (gross head minus lost power in the penstock) and 20 gallons per minute of flow will generate approximately 40 watts. I also liked this Home Power magazine series on hydro, which includes articles on measuring the head and flow of your stream.
As I promised, this a very brief introduction to the idea of generating electricity from nearby streams. I would love to discuss it in more detail, and eagerly await any interest you may have in the topic, so that I need not scrape the bottom of the question reservoir (as it were).
Couleely,
Umbra
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Comments
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kristen510 Posted 8:38 am
06 May 2009
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amykober Posted 3:59 pm
06 May 2009
• Increase efficiency at existing hydropower dams: Most of our nation’s hydropower dams were built 50, 75, even more than 100 years ago. Many of these dams use antiquated, inefficient generating equipment. Dam owners should be required to bring their plants up to modern standards in order to ensure that they are generating the maximum amount of power from every drop of water that they use.
• Consider adding hydropower capacity to existing dams: There are more than 90,000 dams in the United States, and only a fraction of those dams have hydropower capacity. Adding hydropower to dams in good repair that are still serving another useful purpose is appropriate if it can be done without further degrading the local environment that is already compromised by the existence of the dam
• Uphold environmental safeguards: If a hydropower dam can't be operated economically while meeting modern environmental standards, then either its operations should be improved, or the dam should be removed. New hydropower added to existing dams must be able to comply with all existing environmental laws and regulations; if it cannot, then it should not be developed. There are plenty of other sources of renewable energy that can be operated at a profit without harming the environment.
• Hold hydropower developers responsible for dam safety: The majority of our nation’s dams are in need of significant repairs. Would-be developers of hydropower on existing dams must take these costs into consideration and must be responsible for ensuring that these dams are safe and secure.
• Recognize that dams have finite lifespans: For a structure to be truly "green," it must be built with its full life cycle in mind. New or retrofitted dams must have a decommissioning strategy, including a set aside fund dedicated to restoring the river when the dam becomes obsolete.
• Judge dams on their impacts, not on their size: Low-power dams (many of which are physically quite large, despite insistence by developers that they are “small”) harm streams in the same ways as larger-scale dams. Multiple low-power dams scattered on multiple streams add up to major environmental impacts that can be greater than that of a single large dam. The power provided by smaller-scale hydro is a drop in the bucket compared to our overall energy needs. Low-power hydro projects currently account for 40 percent of all hydropower dams, but generate less than 1 percent of the power.Here are some resources for those who want to read more about dams:www.americanrivers.org/our-work/restoring-rivers/dams
www.hydroreform.org
http://dameffects.org
www.lowimpacthydro.org
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Sebulba Posted 8:22 am
08 May 2009
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sindark Posted 8:05 am
10 May 2009
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lizalt Posted 10:11 am
12 May 2009
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