Category The Homeowner’s Guide to. Renewable Energy

Water Intake

All microhydro systems require an intake at the highest point in the system to divert water from the stream into the penstock* As noted earlier, all intakes need to be screened to prevent debris from entering the pipeline. Ideally, the screen should be self-cleansing. In other words, it should be designed so that debris washes off natu­rally* Otherwise, you’ll have to manually remove debris blocking water flow into the pipeline — and do so regularly* Blockages can seriously reduce a system’s output* Screens are immersed in water 24 hours a day, so they should be made of a durable material that won’t rust* One excellent choice is stainless steel...

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BUYING AND INSTALLING A SYSTEM

If you are designing a system on your own, you’ll need to consider each component of the system separately, starting with the intake structure* This section will help you understand a bit more about each compo­nent* If you are relying on a microhydro expert to design your system, he or she will specify the components and suggest the best design* Nonetheless, it is wise to read the material in this section so that you better understand what they’re up to* The more informed you are, the more likely you are to get the system that you will be happy with over the long haul*

As you read the following material, remember that microhydro can be com­bined with any other renewable energy technology For example, a system can combine PVs and microhydro, or a wind turbine and microhydro, or perhaps al...

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What’s the Next Step?

After determining head and water flow, you need to measure the length of pipeline* You can measure the length by pacing off the distance from the inlet to the turbine; however, it is best to measure it directly, using a 100-foot tape measure* You’ll also need to measure the distance from the tur­bine to your house and the battery bank* As in other renewable energy systems that produce DC power, it is best to keep the batteries as close as possible to the source of electricity (in this case, the turbine)* Low-voltage DC electricity doesn’t travel

well, and longer distances require larger diameter wire that is much more ехреп – sive than standard 12-gauge electrical wire* This is one reason why it is a good idea to install an AC generator in a micro­hydro system* The higher voltage AC trav...

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Protecting the Environment

Once you have determined flow rate, you need to determine how much water can be removed from the stream without disrupt­ing the aquatic ecosystem* Obviously, the less water that’s removed, the less impact you’ll have* To make an assessment will require more training than most readers possess* I recommend that you consult an aquatic biologist for a site assessment and recommendations* Your state division of wildlife may be able to help you out* Local permitting agencies may also have guidelines or may supply personnel* A professional stream biologist may be able to give you the best information about the potential impact of damming up part of the river and/or removing water from the stream* Renewable energy is clean and great for the environment, but you don’t want to trash your stream to p...

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Measuring Flow Rates

Stream flow can be measured by one of three methods. The simplest is the con­tainer fill method (Figure 10-6), This is particularly useful in really narrow streams. It requires a large bucket and a stop watch. To make a measurement, you simply find a narrow spot in the waterway

where you can fill a single bucket, A bucket is then thrust into the spot and filled by one person. Someone else uses a stop­watch to time how long it takes the bucket to fill. If the five-gallon bucket fills in 15 seconds, you would multiply five gallons by four to determine the amount of flow in a minute. In this instance, the flow rate would be 20 gallons per minute.

The second method is the float method, well described in Dan News piece in Home Power...

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Measuring Flow Year Round

Stream flow can be measured in one of several ways. For best results, stream flow should be measured during different times of the year because fluctuations are com­mon in perennial streams (those that flow year round). Even in temperate rain forests like those of the Pacific Northwest, theres a dry season during which stream flows are diminished. In mountainous areas, like the Sierras and the Rocky Mountains, peren­nial streams flow year round, but stream flows peak during the spring months as a result of spring snowmelts. Flows decline dramatically in the summer, fall, and win­ter, So, to determine how much power a system can generate, you need to know a streams high-, medium-, and low-flow rates.

Flows in perennial streams can be reduced to a mere trickle, forcing home­owners to turn...

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Measuring Head

Head is an engineering term for water pressure created; in the case of microhydro systems, it is created by the difference in elevation between the water intake and the turbine. Head is usually measured in feet or meters when assessing site potential. The difference in elevation between the intake and turbine can be measured by a variety of methods. For example, you can use an altimeter on a wrist watch (although cheaper ones can be off by 150 feet or more). You can also use a topographical

map of your site to determine the differ­ences in altitude between the intake and turbine*

While both of these methods work, they’re often subject to error* As Scott Davis points out, "The accuracy of the power estimate and jet sizing *** requires measurement of head within 5 percent or so*" As a resu...

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Assessing Head and Flow

Rather than go into minute detail on the ways you determine the potential of a microhydro site, I will give you a gen­eral overview of the process. If you want to install a system, you will need more information than I could possibly sup­ply here. You should also consult one or all of the following resources: (1) Dan News article in Home Power magazine, “Intro to Hydropower. Part 2: Measuring Head and Flow;” (2) Scott Davis book, Microhydro: Clean Power from Water; and (3) Residential Microhydro Power with Don Harris, a video produced by Scott Andrews (you can purchase a copy through Gaiam Real Goods).

When assessing the potential of a site, you need to determine two factors: head and flow. In the words of Dan New, “You simply cannot move forward with­out these measurements...

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