Hydroelectric Power Plants
Hydroelectric Power Plant is a Power generation plant which uses the hydraulic energy of water and convert into electric energy by using the Hydraulic turbines and Electric Generator
Hydraulic Turbines
The hydraulic turbine is a prime mover that uses the energy of flowing water and converts is into the mechanical energy in the form of rotation of the runner. (A prime mover is a machine which uses the raw energy of a substance and converts it into the mechanical energy) Since the fluid medium is water, these turbines are also known as the ‘ water turbines’ . Hydraulic turbines coupled with hydro — generators form the so —called ‘ hydrounits’ which are widely used now a days for generating electrical power.
CLASSIFICATION OF TURBINES
Hydraulic turbines may be classified in the following ways:
(A)According to the type of energy at inlet.
(a) Impulse turbine (b) Reaction turbine.
(B) According to the direction of flow through runners.
(a) Tangential flow b) Radial flow c) Axial flow d) Mixed flow turbines.
(C)According to the head and quantity of water
(a) High head turbines —which work under high heads (above 250m) but with less quantity of water. Example: Pelton wheel
(b) Medium head turbines —work under medium heads (60m to 25m) —they require relatively large quantity of water. Example: Francis turbines
(c) Low head turbines —work under heads less than 60m —they require a very la quantity of water. Example: Kaplan turbine
(D)According to position of shaft
(a) Horizontal turbines —These turbines have horizontal shafts. Example: Pelton wheel
(b) Vertical turbines —These turbines have vertical shafts. Example: Francis and Kaplan turbines.
Advantages of Hydro Power
i. Water source is perennially available. No fuel is required to be burnt to generate electricity. It is aptly termed as ‘the white coal’. Water passes through turbines to produce work and downstream its utility remains undiminished for irrigation of farms and quenching the thirst of people in the vicinity.
ii. The running costs of hydropower installations are very low as compared to thermal or nuclear power stations. In thermal stations, besides the cost of fuel, one has to take into account the transportation cost of the fuel also.
iii. There is no problem with regards to the disposal of ash as in a thermal station. The problem of emission of polluting gases and particulates to the atmosphere also does not exist; Hydropower does not produce any greenhouse effect, cause the pernicious acid rain and emit obnoxious NO. iv. The hydraulic turbine can be switched on and off in a very short time. In a thermal or nuclear power plant the steam turbine is put on turning gear for about two days during start-up and shut-down.
v. The hydraulic power plant is relatively simple in concept and self contained in operation. Its system reliability is much greater than that of other power plants.
vi. Modem hydropower equipment has a greater life expectancy and can easily last 50 years or more. This can be compared with the effective life of about 30 years of a thermal or nuclear station.
vii. Due to its great ease of taking up and throwing off the load, the hydropower can be used as the ideal spinning reserve in a system mix of thermal, hydro and nuclear power stations.
viii. Modern hydro-generators give high efficiency over a considerable range of load. This helps in improving the system efficiency.
ix. Hydro-plants provide ancillary benefits like irrigation, flood control, afforestation, navigation and aqua-culture.
x. Being simple in design and operation, the hydro-plants do not require highly skilled workers. Manpower requirement is also low
Disadvantages of Hydro Power:
i. Hydro-power projects are capital-intensive with a low rate of return. The annual interest of this capital cost is a large part of the annual cost of hydropower installations.
ii. The gestation period of hydro projects is quite large. The gap between the foundation and completion of a project may extend from ten to fifteen years.
iii. Power generation is dependent on the quantity of water available, which may vary from season to season and year to year. If the rainfall is in time and adequate, then only the satisfactory operation of the plant can be expected.
iv. Such plants are often far way from the load centre and require long transmission lines to deliver power. Thus the cost of transmission lines and losses in them are more.
v. Large hydro-plants disturb the ecology of the area, by way of deforestation, destroying vegetation and uprooting people. Strong public opinion against erection of such plants is a deterrent factor. The emphasis is now more on small, mini and micro hydel stations.
vi. Silt content in Indian River is too high, and that creates lot of problems to hydro station. vii. Some site is so remote there is no access road, for that we have to make road first
Selection of site for a Hydro Project:
The following factors should be considered while selecting the site for hydroelectric power plant.
I. Availability of water
II. Water storage capacity
Available water head
IV. Accessibility of the site
V. Distance from the load centre
VI. Type of land of site
Important Questions
Match List I with List II and select the correct answer using the codes given below the lists:
| List 1 (Water Turbines) | List 2 (Applications) |
| A. Pelton | 1. High Head & Low Discharge |
| B. Francis | 2. High Head & High Discharge |
| C. Kaplan | 3. Medium Head & Medium Discharge |
| 4. Low Head & High Discharge |
CODES
| A | B | C | A | B | C | ||
| (a) | 1 | 3 | 2 | (b) | 2 | 4 | 3 |
| (c) | 1 | 3 | 4 | (d) | 3 | 2 | 4 |
Ans. (c)