Micro-Hydroelectric Power
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HOW MUCH POWER CAN YOU GENERATE?
The amount of power available depends on the dynamic head, the amount of water flow and the efficiency of the turbine/generator combination. To get an idea about available power in watts, multiply the head in feet, times flow in GPM, times 0.18 times efficiency. Turbine efficiency ranges from 25% to 50%, with higher efficiency at higher heads. To get a rough idea, use 0.30 (re cp resenting 30%) as a multiplier for efficiency.
The Harris Pelton turbines are well suited to higher head and lower flow situations. Flow is limited by nozzle size (a maximum 1/2"). With the Harris, adjustment to variable flows is as easy as switching a valve and dialing in the alternator. Harris turbines are now available with permanent magnet (PM) alternators. This option provides up to 30% more efficiency than the standard alternators.
Higher flows are accommodated by the ESD Turgo Turbines. (They can have nozzles of up to 1" in diameter.)
The ESD LH-1000 provides better efficiency at low heads and can handle higher flow rates. The High Voltage Hydros are ideal for sites where water is available at long distances from power needs. They generate 100+ AC power that is stepped down and rectified at the batteries. This allows the use of relatively small wire for a distance of up to 10,000 feet. They can also deliver up to 4000 watts where higher power is needed.
Pipelines
A hydroelectric turbine operates from the pressure at the bottom end of a pipeline. This pressure, usually measured in pounds per square inch (PSI), is directly related to the head, or vertical distance from where the water goes into the pipe at the top of the pipeline, to the turbine located at the bottom of the pipeline. The pressure at the lowest point of a pipeline is equal to 0.433 times the head, (the vertical distance in feet). Pressure is important because it is a determining factor
in how much power is available and what type of pipe is required. Polyethylene pipe can be used for pressures
up to 100 PSI, PVC pipe is available with pressure ratings from 160 to 350 PSI and steel pipe can withstand 1000 PSI or more. Check with your local plumbing supplier for pipe ratings. Pipe diameter is very important. All pipelines will cause the water flowing in them to lose some energy to friction. The pipe must be large enough for the maximum quantity of water it will carry. The pressure at the bottom of a pipeline when water is not flowing is called static pressure. When water is flowing through the outlet or nozzle of the hydroelectric turbine, the pressure at the outlet is the dynamic pressure or running head. If you install a gate valve on the pipeline just above the turbine and a pressure gauge on a “T” fitting just above the gate valve, you will read the static pressure on the gauge when the valve is closed and the dynamic pressure when the valve is opened.
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The maximum power that can be delivered by a pipeline will occur when the dynamic pressure is approximately 2/3 of the static pressure. The actual flow rate of the water in a hydroelectric system is determined by the diameter of the nozzle. We will supply a turbine with the proper size nozzle for your site, depending on the head, flow, length and diameter of the pipe. We carry hydroelectric generators made by Energy Systems and Design, and Harris Hydroelectric. Use the descriptions on the following pages to help determine which turbine will work better for your site and power needs.
Let us help you design the system
If you think you have a suitable site, contact us and we will help you choose the best unit for your situation. Determine the following information about your site before you contact us:
1. Head– The total vertical elevation from the place
where the water enters the pipe to the point where
the turbine will be located.
2. Flow– The number of gallons per minute that are
available.
3. Distance– The length of pipe that will be necessary
to carry the water from the pickup to the turbine. If the pipe is already installed, what is the type and diameter?
4. Location– Distance from turbine to batteries.
Nozzle Selection
Power output of a hydroelectric generator is determined by the pressure of the water at the nozzle and the amount of water flowing out of the nozzle. The larger the nozzle, the greater the flow will be. The nozzle must also be sized small enough to keep your pipeline full and keep the speed of the water in the pipe below 5 feet per second. The nozzle selection chart on page 31 shows water flow through various size nozzles at given pressures. Use this chart to determine what size nozzle and how many nozzles you need to accommodate the flow of water you have and to deliver the amount of power you need. A pressure gauge in the pipe feeding your turbine, installed before the shutoff valve, can help you check proper operation and diagnose problems. When the valve is shut off, the gauge will read the static pressure in pounds per square inch PSI (head in feet x .433). When the valve is turned on the gauge will read a lower pressure. The difference between these two pressures represents your loss to friction in the pipe. The greater the flow, the greater your loss will be. (See pipe loss chart on page 31 for PVC pipe.)
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