Hydroelectric power plant

HYDROELECTRIC POWER PLANT

INTRODUCTION

In hydrelectric power plants the energy of water is utilized to rotate the turbine and the turbine runs the generator to produce electricity. The main source of hydroelectric power is the river and it has a poetential difference relative to the ocean towards which it flows. The water falls from appreciable vertcal distance. So the potential energy is converted to shaft work of the generator.

The hydrolic power is produced is given by

p=gρQHƞ

Electrical energy produced is                     

W=gρQHƞt

where g=9.81m/s2

ρ=1000kg/m3

Q=Discharge of water in m3/s

H=water head height in m

ƞ=efficiency(0.5 to 0.9)

t= time of discharge(8760h/year)

ADVANTAGES AND DISADVANTAGES OF HYDROELECTRIC POWER PLANT

ADVANTGES

      Water is available in ample amount whose supply is automatic .

      Water reaches the power house site in its own so no mining operation and transportation is required.

      After using the water it can be reused for drinking water and irrigation purpose.

      IT has high efficiency near about 80%.

      No polluton is caused by this power plant.

      The running cost is comparatively low.

      Maintence is easy and less expensive compare to thermal power plant.

      It offers more flexiblity in operation.

      It has very long life.

DISADVANTAGES

      The initial cost is very high.

      The huge amount of water is not available throghout the year depanding onthe weather condition.

      Transmission cost is high as it is installed at the hilly areas.

      Interruption in contionous power generation.

      Skilled and experienced labour are required.

SELECTION OF SITE

1. Availability of water -  Since the primary requirement of a hydro-electric power station isthe availability of huge quantity of water, such plant should be built at a place where adequate water is available at a good head.

2. Storage of water -  Since there is wide variation in rainfall all round the year, it is always necessary to store the water for countinuous generation of power . The storage capacity can be estimated with the help of mass curve.

3. Available water head-  The availability of head depends upon the topography of the area. High head means high potential energy. To get most economical an effective head, it is necessary to consider all possible factors which affect it.

4. Distrance from the load centre - If the side is located near the load centre, the transmission line cost and transmission loses will be reduced.

5. Accessibility of the site - The site should be easily accessed by rail or road for transporting the plant equipments .

6. Cost and type of land - The land for construction the plant should be available at a reasonable cost. The bearing capacity of the ground should be adequate to withstand the weight of heavy equipments.