Small Hydropower Systems: Energy Efficiency and ... - NREL

1 If you re considering building a smallhydropower system on water flowingthrough your property, you have a longtradition from which to draw your inspi-ration. Two thousand years ago, theGreeks learned to harness the power ofrunning water to turn the massive wheelsthat rotated the shafts of their wheat flourgrinders. And in the Hydropower heydayof the 18th century, thousands of townsand cities worldwide were located aroundsmall Hydropower sites. Today, Small Hydropower projects offeremissions-free power solutions for manyremote communities throughout theworld such as those in Nepal, India,China, and Peru as well as for highlyindustrialized countries, like the fact sheet will help you determinewhether a Small Hydropower system willwork for your power needs and whetheryour location is right for Hydropower tech-nology.

2 It will also explain the basic systemcomponents, the need for permits andwater rights, and how you might be able tosell the excess electricity you generate. Uses of HydropowerIn the United States today, hydropowerprojects provide 81 percent of the nation srenewable electricity generation and about 10 percent of the nation s total elec-tricity. That s enough to power mil-lion homes, according to the NationalHydropower Association. Small Hydropower SystemsCLEARINGHOUSEENERGYEFFICIENCY A NDRENEWABLEENERGYTOFENERGYDEPARTMENUENIT EDSTATSOFAERICAMThis document was produced for the Department of Energy (DOE) by the National Renewable Energy Laboratory ( nrel ), a DOE national laboratory. Thedocument was produced by the Information and Outreach Program at nrel for the DOE Office of Energy Efficiency and Renewable Energy .

3 The Energy Efficiencyand Renewable Energy Clearinghouse (EREC) is operated by NCI Information Systems, Inc., for nrel / DOE. The statements contained herein are based oninformation known to EREC and nrel at the time of printing. No recommendation or endorsement of any product or service is implied if mentioned by with a renewable-source ink on paper containing at least 50% wastepaper, including 20% postconsumer wasteDOE/GO-102001-1173FS217 July 2001 This Small -scale Hydropower system is helping an Alaskan community save money on Hippe, nrel /PIX 04410 The vast majority of the Hydropower pro-duced in the United States comes fromlarge-scale projects that generate morethan 30 megawatts (MW) enough elec-tricity to power nearly 30,000 Hydropower systemsare thosethat generate between.

4 01 to 30 MW ofelectricity. Hydropower systems that gen-erate up to 100 kilowatts (kW) of electricityare often called microhydro ofthe systems used by home and Small busi-ness owners would qualify as microhydrosystems. In fact, a 10 kW system generallycan provide enough power for a largehome, a Small resort, or a hobby Hydropower WorksHydropower systems use the Energy inflowing water to produce electricity ormechanical Energy . Although there areseveral ways to harness the moving waterto produce Energy , run-of-the-river systems,which do not require large storage reser-voirs, are often used for microhydro, andsometimes for Small -scale hydro, run-of-the-river hydro projects, a por-tion of a river s water is diverted to achannel, pipeline, or pressurized pipeline(penstock)that delivers it to a waterwheelor turbine.

5 The moving water rotates thewheel or turbine, which spins a shaft. Themotion of the shaft can be used formechanical processes, such as pumpingwater, or it can be used to power an alter-nator or generator to generate fact sheet will focus on how todevelop a run-of-the-river project. Is Hydropower Right for You?Of course to build a Small hydropowersystem, you need access to flowing quantity of falling water mustbe available, which usually, but notalways, means that hilly or mountainoussites are best. Next you ll want to determine the amountof power that you can obtain from theflowing water on your site. The poweravailable at any instant is the product ofwhat is called flowvolume and what iscalled headHead is the vertical distance that waterfalls.

6 It s usually measured in feet, meters,or units of pressure. Head also is a func-tion of the characteristics of the channel orpipe through which it Small Hydropower sites are catego-rized as low or high head. The higher thehead the better because you ll need lesswater to produce a given amount ofpower, and you can use smaller, lessexpensive equipment. Low head refers toa change in elevation of less than 10 feet (3meters). A vertical drop of less than 2 feet( meters) will probably make a Small -scale hydroelectric system , for extremely Small power gen-eration amounts, a flowing stream with aslittle as 13 inches of water can support asubmersible turbine, like the type usedoriginally to power scientific instrumentstowed behind oil exploration ships.

7 When determining head, you need to con-sider both gross headand net is the vertical distance between thetop of the penstock that conveys the waterunder pressure and the point where thewater discharges from the turbine. Nethead equals gross head minus losses dueto friction and turbulence in the piping . 2A10 kW system canprovide enough powerfor a large home, asmall resort, or ahobby this microhydropower system, water is diverted into the penstock. Some generators can be placed directly into the stream. IntakeCanalForebayPenstockPowerhouse3 The quantity of waterfalling is called get a rough estimate of the vertical dis-tance, you can use Geological Surveymaps of your area or the hose-tube method involves takingstream-depth measurements across thewidth of the stream you intend to use foryour system from the point at which youwant to place the penstock to the point atwhich you want to place the turbine.

8 Youwill need an assistant; a 20 to 30 foot (6 to9 meters) length of Small -diameter gardenhose or other flexible tubing; a funnel; anda yardstick or measuring tape. Stretch the hose or tubing down thestream channel from the point that is themost practical elevation for the penstockintake. Have your assistant hold theupstream end of the hose, with the funnelin it, underwater as near the surface aspossible. Meanwhile, lift the downstreamend until water stops flowing from the vertical distance betweenyour end of the tube and the surface of thewater. This is the gross head for that sec-tion of stream. Have your assistant moveto where you are and place the funnel atthe same point where you took your mea-surement. Then walk downstream andrepeat the procedure.

9 Continue takingmeasurements until you reach the pointwhere you plan to site the turbine. The sum of these measurements will giveyou a rough approximation of the grosshead for your site. Note: due to thewater s force into the upstream end of thehose, water may continue to movethrough the hose after both ends of thehose are actually level. You may wish tosubtract an inch or two (2 to 5 centimeters)from each measurement to account forthis. It is best to be conservative in thesepreliminary head your preliminary estimates look favor-able, you will want to acquire more accu-rate measurements. The most accurate wayto determine head is to have a professionalsurvey your site. But if you know youhave an elevation drop on your site of sev-eral hundred feet, you can use an aircraftaltimeter.

10 You may be able to buy, borrow,or rent an altimeter from a Small airport orflying club. A word of caution, however:while using an altimeter might be lessexpensive than hiring a professional sur-veyor, your measurement will be less accu-rate. In addition, you will have to accountfor the effects of barometric pressure andcalibrate the altimeter as necessary. Determining flowThe quantity of water falling is calledflow. It s measured in gallons per minute,cubic feet per second, or liters per easiest way to determine yourstream s flow is to obtain data from localoffices of the Geological Survey, Army Corps of Engineers, the of Agriculture, your county sengineer, or local water supply or floodcontrol authorities. If you can t obtainexisting data, you ll need to conduct yourown flow can measure flow using the bucketmethod, which involves damming yourstream with logs or boards to divert itsflow into a bucket or container.