| What is Micro-Hydro?
Micro-Hydro is a form of renewable energy where the force of falling water is used to generate electricity. Micro-Hydro systems generally do not construct new dams or impoundments to generate power. Earthbound Services, LLC designs systems that preserve the natural stream environment. So, micro-hydro can be low impact and ecologically sensible. Micro-Hydro can also be the cheapest form of renewable energy, per kilowatt-hour of electricity produced. However, micro-hydro is also very site specific. It is only economically practical at sites where the water resource and site constraints are favorable for a micro-hydro system. Unfortunately, many properties with streams do not have practical micro-hydro sites.
Can Micro-Hydro work for me?
There are a few key factors in determining whether you have a practical site for Micro-hydro. The first step is to determine how much power you need to generate. This means looking at how much power you currently use and where you can use electricity more efficiently or where you can switch from electricity to another fuel. The next step is to determine what the head or vertical drop of the flowing water is from where the water intake will be to where the hydro turbine will be generating the power. The straight-line horizontal distance between the intake and turbine is also important information. Next, it is necessary to determine the flow in the stream at various times of year. If the system is expected to generate power year-round, the flow during the driest time of year (late August, early September) should be considered.
Measuring Head
Head is most easily measured using a hand level or "pea-shooter". This work is done with another person. The person using the level stands at the low point, where the turbine would be and directs the other person (siting person) to walk uphill until they can see their feet when siting level. The level person walks to where the siting person is standing and the process is repeated. The number of times this process is repeated is counted. That number is multiplied by the height between the ground and the level person's eye when standing straight. While measuring head with a level, a 200' tape can be used to measure the horizontal distance needed for the head drop.
Determining Flow
At Earthbound Services, we prefer to determine flow by correlating your site to another stream with a U.S. Geological Survey (USGS) gaging station on it. That way we can approximate decades of flow measurements for your site. This work can generally be done at the computer without a site visit.
Some on-site flow measurements can be useful to confirm or adjust the correlated flow estimates. The two most common ways of measuring flow are the bucket method and the cross-section method.
For the bucket method, find a narrow part of the stream where the flow can be easily channeled. Find a way to channel most or all of the water into a 5-gallon bucket. Time how long it takes to fill the bucket. Divide 5 gallons by the measured time to get gallons per minute (gpm).
For the cross-section method, find a relatively flat stretch of the stream about 20 to 50 feet along the stream's flow path. This should be marked by stringing a rope across at the upstream and downstream ends of the stretch. Measure the depth of the stream at 1-foot intervals across the stream in the middle of the stretch. This can be used to calculate the cross section area. Then float something bright and bio-degradable, like an orange, in the middle of the stream. Time how long it takes for the orange to travel between the two ropes. Repeat timing the float three times altogether and average the results. Multiply the cross-sectional area (sq.ft.) by the float speet (ft/sec) to get the flow (cubic feet per second or cfs). Depending on the nature of the stream bed, there is a correction factor since the speed of water at the surface is not the average speed of the water in the river.
Once we have determined the stream flow at various times of year, and it seems like the project might be worthwhile, the state agency responsible for issuing a EPA Clean Water Act Section 401 Water Quality Certificate (401 WQ Cert) is contacted to get an approximate idea of how much flow will be required to be left in the stream for aquatic life and not withdrawn to generate power. This is called the bypass flow. After subtracting the required bypass flow, we now have a good idea of how much flow we can use to generate power.
Calculating Power
Generally, Head X Flow = Power. Head (in feet) X Flow (gallons per minute) / 10 = Power (watts continuously generated). Power (watts) x 24 (hours/day) / 1,000 = Kilowatt-hours per day. To get some perspective, the typical U.S. home (not an energy conserving home) uses from 5,500 KwH to 10,000 KwH per year.
Other Considerations
• Distance from location of turbine to building using power
• Length of penstock or pipe required to conduct water from intake to hydro turbine
Permitting Issues
• The Federal Energy Regulatory Commission (FERC) has jurisdiction over hydro projects on virtually all waterways in the United States. More information is available at the FERC website
• The U.S. Army Corps of Engineers (USACE) has jurisdiction over withdrawls of water on virtually all waterways in the United States. More information is available at the Army Corps website
• Also involved are the particular state Department of Natural Resources as they must issue the EPA Clean Water Act Section 401 Water Quality Certificate (401 WQ Cert) which is required for getting a FERC license or exemption.
• Both the state Department of Natural Resources and USACE consult with the federal and state Fish & Wildlife divisions to get their input, in many cases.
• A state and/or USACE wetlands permit might be required depending on the wetlands impact of the potential project.
• Other state and local permits might apply.
• The permitting process can take from 12 - 24 months. The different permits can be applied for at the same time to minimize the total time it takes to get all the necessary permits.
Links to Manufacturers of Quality Residential Scale Turbines
• Energy Systems and Design
• Harris Hydroelectric
Summary - Information we will need for a first-cut feasibility analysis to see if your site would be useful for Micro-Hydro
• Measurement of available head
• Measurement of horizontal distance for head drop
• Measurements of flow, if any
• Distance from turbine location to building using power
• 911 Address for property or exact directions to site WITHOUT landmarks for location on USGS map (if 911 Address is not available)
• Name of stream, if it is named
• Times of year that power generation is needed or desired
• Amount of power, in kilowatt-hours in a typical month, needed from the micro-hydro system
• Other information might be required to determine if micro-hydro is feasible on your property
Information provided on this website is not to be construed as professional advice. Please call us or email us about your unique project. | 
