Turbine Generator: Turbine Type Selection for Micro-Hydro Power Plant

Basically, the selection of turbine type for micro-hydro power plant is same with the selection of the conventional hydropower turbines (water turbine) type which ever existed. Basic selection as the driving turbine type generators on micro hydro power plant must first know the amount of head (meters), water discharge (m3/second), and its magnitude turbine rotational speed (n). Turbine rotation speed is obtained by knowing the velocity of water that will enter the turbine blades, by changing a linear velocity to the speed of the circumference (centrifugal) on the turbine shaft speed is called the circumference equation as following below:

U1 = D . π . n

Where:

U1 = Circumferential speed (m/s)

D = Diameter wheel turbine (m)

n = Cycle turbine (rpm)

The selection rotation speed can be determined as high as possible, because with a high rotational speed, moment coupling will be obtained is small, small shaft, and small turbine wheel diameter, so it will make the size smaller generators. Circumferential speed (U1) is increasing with the growing cycle. The next very important to know in turbine plan is to determine the specific speed (nq) that will be crucial in planning the type of turbine that will be used in the micro-hydro power plant. Large specific speed (nq) can be obtained by the following formula:

nq = n. (V^0.5 / H^0.75)

Where:

n = Number of rotation (rpm)

V = water capacity (m³/second)

H = Head / water fall height (m)

Besides using the above formula, the value can also be obtained by using the chart specific speed below after the following parameter has been known such as head, turbine rotation, and water capacity. After know the specific speed, the type of turbine will be used can be determined whether to be used for propeller turbine, pelton, cross flow or the other. Determination of turbine type for micro-hydro power plant can also be directly known through the chart below follows the known value of specific speed of the calculation method above.