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Mini-Micro Hydro Power Plants
From CopperWiki
Mini-micro hydro power is a term used for hydroelectric power installation units that generate less than 100kw of power. Hydro power systems convert potential energy stored in water held at height to kinetic energy (or the energy used in movement) to turn a turbine to produce electricity.
Energy available in a body of water depends on the water’s flow rate and the height (or head) from which the water falls. These are divided into low head, medium head and high head, where the height drop is greater. Hydro power is mainly used in remote areas where there is plenty of natural water supply.
There are lots of such small units used in remote areas across the world. It is one of the most economical ways of generating captive power for self-consumption as it is cheaper than other power generating units, such as those depending on solar power and wind power. In some cases, a mini-micro hydro plant is combined with solar energy systems. Solar energy can be optimised in the summer when the water level decreases in the streams, and hydro power can be exploited in the winters when the water in the streams is at the maximum and solar energy is low.
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[edit] Different Turbines
There are many different types of mini-micro hydro turbines. They use different technologies and are used for different heights (fall in height of water) and water speeds.
| TURBINE | HEAD IN METRES |
|---|---|
| Kalpan | 2<H<40 |
| Francis | 10<H<350 |
| Pelton | 50<H<1300 |
| Michell-Banki | 3<H<250 |
Source: Azad Engineering, India
Comparison of Various Turbines
- Pelton turbines: These are impulse machines and use Newton’s Second Law (that is, force equals mass multiplied by acceleration). Lester Allan Pelton (1829-1908) invented the machine in the 1870s. These are very efficient turbines that have lots of cups on the wheels to capture the energy of moving water. The cups are made of stainless steel and stand up well to abrasion.
- Kalpan turbines: These are axial flow reaction machines. These are generally more adaptable to low heads. Being low-speed turbines, axial flow machines can be coupled with high-speed generators using a bevel.
- Francis turbines: These are mixed flow reaction machines that have a better peak load performance than Kaplan or Pelton turbines. They can be both horizontal and vertical and have a spiral casing with a guide vain assembly.
- Cross-flow turbine or Michell-Banki: A cross-flow turbine is used where the water head is low, but is at high flow. Unlike Pelton turbines, which use many small buckets, cross-flow turbines use long turbine blades to accommodate the large flow of water. These turbines are used when the velocity is lower but a large quantity of water is available. They spin at lower speeds than Pelton turbines, but have higher torque due to the volume of water.
