Classification of a hydroelectric power plant according to water flow regulation -a hydroelectric power plant can be classified according to the extent of water flow regulation available into the following categories
Run-off river plants without pondage
these plants are located such that they use water as it comes without any pondage or storage.there is no control over the flow of water.During the high flow and low load, water is wasted.During low flow of water, the capacity of the plant is very low.This type of plant has very low firm capacity.In such site the water is mainly used for irrigation or navigation and power pant is only incidental.Such plant can be built at a considerably low cost but the head available and the amount of power generated are generally low.its principle aim is to used whatever flow is available for electrical energy generation and save coal that would otherwise be necessary for the steam plant.During the period of the high flow this plant can supply a substantial portion of base load.
Run of river plant with pondage
Pondage means storage of water at near the plant to take care of hour to hour fluctuation in load on the station.pondage increases the plant capacity provided the floods do not raise the tail race water level thus reducing the effective water head and plant output.Such pant can serve as base load or peak load plant depending on the stream flow.When plenty of water is available then these pant can be used as base load plant.When stream flow decreases then these pant can be made to work as peak load plant.These pant offer maximum conservation of coal and other fuel when work with integration of other power plant.
Reservoir Plant
Most of the power plant across the world belonging to this category of hydro electric power plant.When water is store in a very big reservoir behind a dam then it is possible to control the flow of the water and use it most effectively.Storage of water increases the firm capacity of the plant.the pant can be used as a base load plant or as a peak load plant depending on the amount of water stored in the reservoir .
Classification of hydro electric power plant according to load
According to the load hydro plant can be classified as base load pant,peak load plant and Pumped storage Plant .
Base Load Plants
This type of plant feed the base load of the system.thus they supply almost constant power at constant load throughout the operation period and operate on a high load factor. These plants are always of large capacity .Run-off river plant without ondage and reservoir plant is termed as baseload plants.For a plant to be used as baseload plant its energy generation cost may be very low.
Peak Load plants
As the name suggests that this type of plant always supply the peak load of the system. Run-off river plants with pondage can be used as a peak load plant during the low flow period. The reservoir plant can of course be used as a peak load plant. Peak load plants have large seasonal storage .it stores water during off peak period and are running a peak load period. this plant operates at a low load factor.
Pumped Storage Plant
it is a special type of plant meant to supply peak loads. During peak load period water is drawn from the headwater pond through the penstock and generates power for supplying the peak load. During the off period, the same water is pumped back from the tailwater pond to the headwater pond so that this water may be used to generate energy during the next peak load period. Generally, the pumping of water pond is done at night when loads are low. Such plants operate in an interconnected system, where other generators are also available. This plant helps in improving the load factor of the system plant. A general arrangement of the pumped storage plants is shown in the figure given below.
Also, Read