ADVANTAGES AND DISADVANTAGES OF 13.
It can be made multipurpose so as to give
HYDRO STATIONS additional advantages of irrigation and flood
control.
Advantage:
Disadvantage:
1. The plant is highly reliable and its operation
and maintenance charges are very low. 1. Initial cost of the plant including the cost of
dam is high.
2. It is quick starting and can be brought on load
within few minutes, and the load can be 2. Hydro-station has special requirement of site
increased rapidly. which usually is an isolated area with difficult
access.
3. Hydro stations are able to respond to rapidly
changing loads without loss of efficiency. 3. Power generation by the hydro-plant is only
dependent on the quality of water available,
4. The plant has no standby losses.
which in turn depends on rain. During the dry
5. The efficiency of the plant does not change year, the power production may be curtailed or
with age, whereas there is considerable even discontinued. This availability of power
reduction inefficiency of thermal as well as from such plants is not much reliable.
nuclear power plant with age.
4. The site of hydro-electric station is selected
6.The plant and associated civil engineering on the basis of water availability at economical
structures have a long life. head. Such sites are usually away from the load
centres. The transmission of power from power
7. Less labour is required to operate the plant, station to the load centre requires long
much of the plant is under automatic control. transmission lines. This substantially increases
8. In this case no nuisance of smoke, exhaust the capital expenditure and also there is loss of
gases, soot etc. exists. power in such transmissions.
9. It uses non-wasting natural source, i.e. water 5. It takes long time for its construction as
power. compared to thermal plants.
10. Cost of land is not a problem, as the hydro MAIN EQUIPMENT PROVIDED IN A
stations are situated away from the developed POWERHOUSE
areas.
1. Prime movers (turbine) coupled with
11. The cost of generation of energy varies with generators
little with the time. 2. Turbine Governors
12. The machines used in hydel plants are more 3. Relief valve for penstock fittings
robust and generally run at low speeds (300 to 4. Gate valves
400 rpm) where the machines used in thermal 5. Water circulating pumps
plants run at a speed of 3000 to 4000rpm. Due 6. Flow measuring devices
to low speed and temperature, there are no 7. Air ducts
complications of special alloys required for 8. Transformers
construction. 9. Reactors
10. Switch board equipment and
instruments
11. Oil Circuit breakers part of the area supports the
12. Low tension and High tension bus bar buttresses.
13. Cranes 3. The foundation treatment also
14. Shops and offices becomes easier. Although the
buttresses transmit concentrated load
FACTORS TO BE CONSIDERED IN THE
to their footings, overall requirements
SELECTION OF SITE
of the foundation are not as stringent
1. Quantity of water available as in case of gravity of arch dams.
2. Storage of water 4. The dam is inherently stable against
3. Sedimentation over-turning and sliding due to the
4. Availability of head of water vertical component of water pressure
5. Water pollution on the sloping deck.
6. Distance from load center 5. If the need so arises, the height of the
7. Geological investigations dam can he easily raised subsequently.
8. Access to site 6. Less weight of concrete is required than
for the solid gravity dams.
MERITS AND DEMERITS OF EARTH FILL DAMS 7. Powerhouse and other associated
Merits: equipment can be housed in the space
1. It can be built on all types of foundation. between buttress thus saving in cost
2. It can be constructed quickly. and space
3 Usually less costly than a masonry dam.
4. If protected from erosion, this type of dam is
the most permanent type ot construction. DIFFERENT TYPES OF SYSTEMS AND
5. It fits best in natural surroundings and COMPONENTS USED IN STEAM POWER
becomes stronger with age.
1. High pressure boiler
2. Prime mover
Demerits:
3. Condensers and cooling towers
1. Greater seepage loss than other dams.
4. Coal handling system
2. It fails suddenly without any warning and is
5. Ash and dust handling system
subjected to erosion and flood damage. 3. The
6. Draught system
earth dam is not suitable for a spillway,
7. Feed water purification plant
therefore, a supplementary spillway is required.
8. Pumping system
4. It is not suitable in areas of heavy rain fall.
S. It requires heavy maintenance. ADVANTAGES OF WATER TUBE BOILERS
6. It is limited in height.
1. High pressure can be obtained.
2. Heating surface is large. Therefore
steam can be generated easily.
ADVANTAGES OF BUTTRESS DAM:
3. Large heating surface can be obtained
1. The buttress dams are much lighter in by use of large number of tubes.
weight as compared to the gravity 4. Because of high movement of water in
dams. the tubes the rate of heat transfer
2. They also have no problem of becomes large resulting into a greater
foundation drainage or uplift, as only efficiency.
STEAM TEMPERATURE CONTROL arrangements are required for
conversion of Reciprocating Motion into
1. Excess air control
circular motion. But in Steam Turbine
2. Flue gas recirculation
no friction losses are there.
3. Gas By-pass control
8. Steam Turbines are quite suitable for
4. Control of combination superheaters
large Thermal Power Plant as they can
5. Adjustable burner control
be built in size from few Horse Powers
to over 200000 HP in single unit.
FACTORS AFFECTING BOILER PERFORMANCE
NEED FOR PERFORMANCE ANALYSIS OF STEAM
1. Periodical cleaning of boilers TURBINES
2. Periodical soot blowing
1. To increase availability and reliability.
3. Proper water treatment programme
2. To reduce operating cost and maximize
and blow down control
production.
4. Draft control
3. To assess the effect of blade washes.
5. Excess air control
4. To identify optimum range of throttle
6. Percentage loading of boiler
loading rates.
7. Steam generation pressure and
5. To maintain power demand to the plant
temperature
or grid.
8. Boiler insulation
6. To avoid catastrophic shutdowns.
9. Quality of fuel
7. To reduce maintenance expenditure.
ADVANTAGES OF THE STEAM TURBINE OVER 8. To determine the underlying causes of
RECIPROCATING ENGINE operating deviations
1. Thermal Efficiency of a Steam Turbine is VARIOUS HEAT LOSSES IN BOILER
higher than that of a Reciprocating
1. Dry flue gas loss
Engine.
2. Loss due to hydrogen in fuel
2. The Steam Turbine develops power at a
3. Loss due to moisture in fuel
uniform rate and hence does not
4. Loss due to moisture in air
require Flywheel.
5. Partial combustion of C to CO
3. No internal lubrication is required for
6. Surface heat losses
Steam Turbine as there are no rubbing
7. Loss due to Unburnt in fly ash
parts inside.
8. Loss due to Unburnt in bottom ash
4. No heavy foundation is required for
Turbine because of the perfect
balancing of the different parts.
5. If the Steam Turbine is properly
designed and constructed then it is the
most durable Prime Mover.
6. Much higher speed may be developed
and a far greater range of speed is
possible than in the case of
Reciprocating Engine.
7. There are some frictional losses in
Reciprocating Engine as some
