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Sustainability Solutions No. 13: Microhydropower at the Spotted Bear Ranger Station
Image of the Spotted Bear Ranger Station sign.
Figure 1—The Spotted Bear Ranger Station in
western Montana.

The Spotted Bear Ranger Station (figure 1) at the Flathead National Forest in western Montana uses microhydropower to supply electricity at its compound. The electrical system includes a generator and turbine with a maximum capacity of 50 kilowatts (kW).

Typically, Addition Creek flow is sufficient to produce enough electricity for the compound's peak demand (25 kW). When creek flow is insufficient, the station uses a propane generator to supply power.  Employees recently replaced older lighting and appliances in an effort to reduce energy demand.

Microhydropower generates electricity using changes in water elevation (figure 2). Water flowing downhill rotates a small turbine. The turbine spins a magnet next to a conductor, causing electricity to flow and create electrical current. Though the definition of microhydropower varies, systems that generate less than 300 kW are considered microhydropower.

Image of the microhydropower system used at the Spotted Bear Ranger Station.
Figure 2—The intake structure for the microhydropower
system at the Spotted Bear Ranger Station.

The main factors that determine the energy a waterway can generate are "head" and flow rate. Head is the water pressure created by the vertical drop between an intake pipe and turbine, minus friction losses in the pipe. Head and flow rate determine the size of pipe required, the turbine type, and the power output. Typical power outputs are about 1 kW of power for 98 feet of head combined with an available flow rate of 5 gallons per minute.

Microhydropower has many possible applications in the Forest Service. Prime locations for microhydropower systems are remote cabins (figure 3), workstations, and campgrounds. The Forest Service also can use microhydropower to supplement existing solar power systems during winter months or to defray the high cost of connecting to a power grid.

To determine whether a microhydropower system can be installed in a waterway, consult the National Environmental Policy Act (NEPA). Some NEPA considerations are the

Image of the Red Ives cabin located in the Idaho Panhandle National Forest.
Figure 3—A microhydropower system may be the perfect
solution to supply electricity for Red Ives cabin at the Idaho
Panhandle National Forest.

presence of endangered species (such as bull trout) and the volume of water required to run the system in relation to the available water in the waterway. A permit must be obtained from the water resources department of the specific State before a microhydropower system can be installed.

For more information on the microhydropower system installed at the Spotted Bear Ranger Station, please contact:

Mike Shoup

We're interested in what is happening in your unit. Contact Bob Beckley at 406–329–3996 to share your sustainability solutions with others in the Forest Service.