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For those with a river or stream nearby, micro hydro power systems offer a cleaner, greener, locally made source of energy. These systems are relatively inexpensive, reliable, and in many cases result in little ecosystem disturbance.

How to use micro hydro power

Do you picture water wheels when you contemplate a micro hydro system? You’re not far off. Micro hydro systems, alternatively known as mini hydro and pico hydro, function as run-of-river systems, much like grist mills of old. This means they run alongside a river or stream, diverting a small amount of water into a turbine and then returning it to the source. Unlike dams, they do not generally interrupt the entire water flow or create a backlog of water in a reservoir, and therefore they cause much less eco-damage than those cement monsters.

Still need some help picturing one? Check out this illustration or watch this short video demonstrating how these green energy systems work.

Micro hydro is intended for homes or businesses that require between 100 and 1,000 kilowatts of energy daily. Additional specifications for these energy generators are as follows:

  1. Some permits required: Many states have codes and requirements, and some request that you get a permit to install any local generating system, so check into the legal restrictions in your area before going too far.
  2. Location limitations: There are some key factors to consider when looking into the feasibility of micro hydro generation, regardless of the type of turbine you choose. First, you must measure the flow rate and head, then calculate the power potential.
    • Flow rate, measured in cubic meters per second (m3s), liters per second (lps), gallons per minute (gpm), and cubic feet per minute (cfm). Determine your stream’s flow rate with these measurement methods. A flow rate less than 0.60 lps (or 10 gpm) is likely not enough to warrant a micro hydro system.
    • Head, or the vertical height (in meters or feet) measured from the level where the water enters the intake pipe (also called a penstock) to where it leaves the turbine housing. Head is usually classified as high or low. Anything below 10 ft (3 meters) is low, and vertical drops of less than 2 feet are not likely to provide suitable conditions for a micro hydro system.
    • Now calculate the power potential by using the formula Pth = Q 3 H 3 g, where Q is flow rate, H is gross head in meters, and g is the gravitational constant of 9.8 meters per second squared. This will give you the theoretical power output (Pth) in kilowatts.
    • You’ll also need to know how much energy you require in an average day. Try this wattage calculator and then compare your daily wattage requirements to your water system’s power potential. If it’s enough, you’re in business!
  3. On or off the grid?: You can generally choose to either remain connected to your city’s power system or go totally independent. Hybrid systems are also good options.
    • Assert your independence: Stand-alone systems, which require batteries to store power, are ideal for those in remote locations. Generally, you’ll need a combination of energy generating techniques (solar, wind, hydro, geothermal) to provide consistent power when you’re off the grid.
    • Stay connected: You can choose to have your micro hydro system grid-connected, which allows you to access normal power systems during periods when water flow is low. Batteries are not generally required for grid-connected systems since any excess power generated is pumped back into the power provider’s pipeline. So aside from government incentives and rebates, you can take advantage of net metering options to offset the costs of your clean energy system. Your state may have regulations in place that require your power company to pay you for any extra renewable energy you pump back into their system.
  4. DYIers delight: Micro hydro is especially popular with those willing to get their hands dirty in the production of clean energy. They can be complex to build, connect, and maintain so hiring a professional is recommended. However, many people have successfully constructed their own generators, and with so many turbine styles to choose from, you may be able to find something suitable for your skills, tools, materials, and location. Check out these do-it-yourself resources for detailed information on how to go from start to finish:

Drawbacks

While hydro is efficient, reliable, cost effective, and can operate without a reservoir, there are some downsides to this type of system. Not all locations are suitable for micro hydro, and if the location is not properly assessed, water diversion can cause ecological damage. Also, power levels tend to fluctuate with the seasons as water levels increase and decrease, so this should also be taken into consideration.

Find it! Micro hydro professionals and supplies

Micro hydro power generation helps you go green because…

  • By relying less on dirty coal, natural gas, or nuclear power plants, you’ll be cleaning up your energy act.
  • Producing your own local energy requires less resource-intensive electrical infrastructure.

Water constantly cycles through the earth via evaporation of oceanic water into clouds (water heated by the sun), precipitation through rain or snow, and the movement of water through rivers back to the ocean.[1] Using mechanical processes, hydro power (also known as hydroelectricity) harnesses water’s energy by directing or channeling it through a penstock and turbines, which rotate to create energy that is fed into a generator. Some hydro power plants require the use of dams to increase the force of the moving water,[2] while others use a diversion technique to channel part of a river through a penstock system.[3]

Offering what many believe is one of the cleanest forms of energy, hydro power does not require the burning of fossil fuels and therefore does not pollute the atmosphere.[4] It is the oldest form of renewable energy, dating back 2,000 years to the time of the Greeks.[5] The first hydroelectric power plant was built in Wisconsin in 1882,[5] and in 2005, hydro power accounted for 73 percent of US renewable energy generation.[6] It is also the world’s largest source of renewable energy, with over 150 countries using hydro power to generate electricity.[7] Small-scale hydroelectric systems are being adapted for use in many developing countries as a low-cost option available to low-density communities in rural areas.[8]

Controversies

Though the potential for increasing the capacity of US hydro power systems is great,[9] critics maintain that they are fraught with environmental downsides—the most obvious being the disruption of fish migrations to spawning grounds and the displacement of land-dwelling plants and animals resulting from flooded areas.[2] Additional drawbacks include decreased water quality due to low oxygen levels,[4] increased sedimentation from erosion and leaching of chemicals in reservoirs,[2] changes in local climate, disruption of socially sensitive areas, and risk of dam breaks due to system failures or military attacks.[10]

China’s level 7.9-magnitude earthquake in May 2008 illustrates this last problem. Shortly after the incident, 30,000 soldiers were sent in to shore up quake-weakened dams in danger of breaching and causing massive floods.[11] Many scientists believe that mega dams (China’s Three Gorges Dam is the world’s largest and only 700 km from the epicenter) may actually trigger quakes if they’re close enough to fault lines.[12][13]

Tax breaks and subsidies

Of all the homegrown power systems available, micro hydro is probably the most affordable. Nevertheless, many states have incentive programs in place to help mitigate the setup costs associated with green power systems. Check out the Database of State Incentives for Renewables & Efficiency listings for something in your area (choose “Hydroelectric” from the “Select a Technology” menu).

Glossary

  • penstock: A pipe used in hydropower systems.

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