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HydropowerUsing Hydropower in Montana

Hydropower in Montana

Harnessing the energy in falling water is nothing new to Montanans. Early small-scale hydro projects pumped water for irrigation and mining, turned sawmill blades, and generated electricity for remote farms, homesteads and factories. On a larger scale, beginning in the late 1800s, dams built on the Missouri River supplied power to hoist ore from mine shafts, to compress air for lead and copper smelters and to power electric lights for growing cities. Although most large-scale sites have now been developed, the small-scale hydro potential of the state's many rivers and streams is still untapped. Small-scale hydro includes projects with a generating capacity between 100 kilowatts and 1 or 2 megawatts; micro-hydro projects are systems having power outputs of less than 100 kilowatts.

If you're thinking of starting a small hydropower project, here are some basics.

Accessibility to the Land

Although most project developers own the land on which the project will be located, others must those rights from landowners. The system intake may have to be located on land owned by a state or federal agency or by another private party. In other cases, both intake and powerhouse may sit on the project developer's land, but the penstock that connects them might cross another person's property.

The feasibility of an entire project should be determined before any purchase or lease agreements are arranged. Also, if it is known that the property in question is not available under any circumstance, alternate plans should be considered.

Determining Site Potential

In order to determine the hydro potential of a site, information regarding amount and variation of streamflow is essential. You should find out if streamflow records have been kept for the stream at any time. A good place to begin inquiries is with the U.S. Geological Survey (USGS) Water Data Discovery, where you'll find realtime streamflow data and historical streamflow data, including lists of active and discontinued stations.

If historic flow records are not available, you should immediately begin monitoring the streamflow at the site: the feasibility of constructing a small power plant is dependent on exactly how much power your stream will put out. The two most important factors to consider are flow and head.

Low head

Flow is the quantity of water flowing past a point at any given time. This amount varies both seasonally and annually, so it is important to collect accurate data for each season of a full year. These data should then be compared to USGS information from your area to decide if it was a dry year or a wet year. You can obtain snow pack information for your area at the U.S. Department of Agriculture Natural Resources Conservation Service in Montana.

Minimum flow rates are necessary to accurately assess the minimum continuous power output you can expect from your hydro unit. Also, maximum flow estimate is needed to ensure that your structure will withstand peak flooding.

Head is the vertical distance in feet from the surface of the supply water to where the water leaves the turbine. The head exerts pressure that can be turned into usable power, so the greater distance the water falls, the more energy is available.

Low head is considered to be less than 60 feet; high head is 60 feet or more. Although there are exceptions, 10 feet of head is usually the minimum necessary to generate power.

Once you have determined the net head and the average flow rate for your site, you can calculate the power output from your stream.

Determining Energy Needs

A central question to project feasibility is whether or not the site will produce enough power to meet your energy needs. Two types of energy estimates should be evaluated - peak demand and total consumption. Peak demand is the maximum power needed at any one time. In household use peak demand occurs when all electric loads are on at once. Total consumption is the number of kilowatt-hours used in a given period. Utility companies usually use the measure kilowatt-hours per month.

A system capable of meeting total consumption will not necessarily cover peak power needs; consumption or power needs may have to be adjusted. If your power needs are greater than your potential energy source, you may consider storing electricity in batteries or buying extra electricity from a utility to supply peak demand needs. Contact your nearest Montana utility to seek assistance early in the process. (utility page link)

Another good place to find information on determining stream head and flow, calculating the power output of your stream is Solar Plexus in Missoula.

Water wheels and water turbines are two basic types of hydropower machines. Water wheels are the traditional devices used to convert the energy in flowing and falling water into mechanical power. They are used in grinding grain, and operating saws, lathes, drill presses, and pumps. Usually large in diameter and slow turning, water wheels work well in streams with large variations in stream flow. Trash racks and screens are usually not needed because sticks, stones, and dirt will flow over the wheel in the stream of water. Water wheels can be used to produce electricity, although the large diameter and slow rotation requires the rotational shaft to be geared up to a much higher RPM.

Because water wheels operate at slow speeds, they are considerably less efficient than water turbines in producing electricity. Water wheels are also bulky and in harsher climates have to be housed in large structures to avoid ice buildup in the winter.

Water turbines spin at high speeds, are used for electrical generation and can be as high as 70 percent - 80 percent efficient in producing mechanical or electrical energy. While water wheels use water carried in an open flume or channel, turbines receive their energy from water carried in pressure conduits. Water turbines are complicated pieces of equipment and must be carefully installed.

Also, debris such as rocks, sticks and sand can interfere with the blades, so a trash rack or screen is required to prevent this material from going through the turbine.

System Components

A typical micro-hydro system consists of several components. An intake structure controls the flow of diversion water to be used. A penstock, or flume, carries the water from the intake structure to the turbine. The powerhouse contains the water turbine, generator and controls.

Calculating Costs

Once the head, flow and system output are known, you can contact equipment suppliers to get accurate cost data. There is no point in contacting these people before the site details are known, as costs of equipment would vary considerably with different sites.

Costs vary widely with each site and size of system.

Environmental Considerations

Water wheels and water turbines alone have a negligible effect on the environment. Most hydro systems, however, require a dam to ensure a continuous source of water. Damming a river or stream can have a long-term effect on the environment surrounding the site. Streamflow is changed, and the water table is usually raised behind the dam and lowered downstream from the structure. You are creating a pond or lake where a stream ecosystem used to exist, so silt may accumulate and you may have constructed an ideal breeding ground for mosquitoes.

Fish movement may be blocked if a fish ladder isn't used. Access roads may contribute to erosion and disrupt the landscape. In general, the larger the dam, the greater the impact on the environment. If you foresee the ecological impact of installing a hydroplant, you can keep stream disruption to an absolute minimum. Keep in mind that you may have to radically change your design to work with your local ecosystem or, in some cases, abandon the hydropower project completely.

Permitting and Licensing

Before you do any construction on your stream, you should be aware of the regulatory conflicts you may face. A variety of institutional and legal barriers exist and your project will go much smoother if these potential problems are identified early in the schedule so you can take the required actions.

Although numerous agencies have potential permitting or review authority, small hydropower projects are likely to require only a few permits. Nevertheless, the time required for obtaining all permits and licenses may be a major part of the project duration, so it is important for you to begin the permitting process in the early stages of developing your site.

Local Permitting Requirements

First of all, you should contact local government offices to determine local permit requirements. The local city and county planning and public works departments can tell you which permits are needed. All local permits or requirements must be satisfied before federal hydropower licenses will be issued. Generating facilities affecting only the developer's property should encounter few problems.

State Permitting Requirements

A hydropower developer in Montana will have to obtain a number of permits. The best source for information on those permits is the Montana Department of Environmental Quality, Environmental Permitting Dept. and Water Quality Info.

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