Different types of turbines used in hydroelectric power plants based on the working parameters such as head, flow, etc., Characteristics of a turbine; specific to its applications in a dam.

1. APPLICATIONS OF TURBINES-HYDROELECTRIC
POWER PLANTS

2. • Hydroelectric and coal-fired power plants produce
electricity in a similar way.
• In both cases a power source is used to turn a propeller-
like piece called a turbine, which then turns a metal shaft
in an electric generator, which is the motor that produces
electricity.
• A coal-fired power plant uses steam to turn the turbine
blades; whereas a hydroelectric plant uses falling water
to turn the turbine.
• The most important part of the hydroelectric power plant
is the dam, which acts as the water reservoir.

3. The basic components of a conventional hydropower
plant are:
• Dam - Most hydropower plants rely on a dam that holds back
water
• Intake - Gates on the dam open and gravity pulls the water
through the penstock, a pipeline that leads to the turbine.
• Turbine - The water strikes and turns the large blades of a
turbine, which is attached to a generator above it by way of a
shaft.
• Generators - As the turbine blades turn, so do a series of
magnets inside the generator. Giant magnets rotate past copper
coils, producing alternating current
• Transformer - The transformer inside the powerhouse takes
the AC and converts it to higher-voltage current.
• Power lines - Out of every power plant come four wires: the
three phases of power being produced simultaneously plus a

5. • Turbines are versatile and can be used in a number of
applications such as steam turbines used at coal-burning
electricity plants to liquid water turbines used at hydro-
electric plants.
• Large scale electrical energy production largely depends
on the use of turbines. Nearly all of the world's power that
is supplied to a major grid is produced by turbines.
• The simplistic design, versatility, and efficiency of
turbines allow for its widespread use in electrical power
generation.

6. • A turbine is a simple device
with few parts that uses
flowing fluids (liquids or
gases) to produce electrical
energy.
• Fluid is forced across blades
mounted on a shaft, which
causes the shaft to turn.
• The energy produced from
the shaft rotation is collected
by a generator which
converts the motion to
electrical energy using a

7. • The type of hydropower
turbine selected for a
project is based on the
head and the flow or
volume of water at the site.
• Other deciding factors
include how deep the
turbine must be set,
efficiency, and cost.
• There are two main types
of hydro turbines: impulse
and reaction.

8. • The impulse turbine generally uses the velocity of the
water to move the runner and discharges to atmospheric
pressure.
• The water stream hits each bucket on the runner.
• There is no suction on the down side of the turbine, and
the water flows out the bottom of the turbine housing
after hitting the runner.
• An impulse turbine is generally suitable for high head,
low flow applications.
• Impulse turbines consist of: Pelton turbine, Turgo wheel
and cross flow turbine.

9. • Pelton turbines are used on
medium to high head hydropower
sites with heads from 20 metres
up to more than 300 metres.
• Power outputs can range from a
few kW up to tens of MW’s on the
largest utility-scale Pelton
systems.
• Because the operating head is
high, the flow rate tends to be low,
ranging from 5 litres/second on
the smallest systems up to 1 m3/s
on larger systems.

10. • Compared to the power produced Pelton turbines are
relatively compact, and because the flow rates are
relatively low the associated pipework is relatively small.
• This means that a Pelton turbine itself is generally easier
to install than an equivalently-powered Kaplan turbine.
• But Pelton turbines need a high pressure water supply
from a penstock pipe, and designing and installing the
penstock pipe is normally more challenging and is more
expensive than the turbine.
• Once through the spear-jet the water impinges on the
rotor and transfers around 97% of its kinetic energy into
the rotational energy of the rotor. To achieve this transfer
of energy the buckets are precisely designed to minimise
all losses.

11. • The surface of the buckets is normally highly polished to
minimise drag and the rotor itself is finely balanced.
• The small ‘cut-out’ in the tip of the bucket is to ensure that
the next bucket doesn’t cut through the jet of water on the
previous bucket prematurely as the rotor rotates.
• Once the water jet leaves the rotor it falls to bottom of the
turbine casing and returns to the river through a discharge
pipe.
• To get a higher flow rate, hence more power through a
single pelton rotor it is possible to have multiple spear-jets,
six jets normally considered to be the maximum.

12. • Pelton turbines can reach up to 95% efficiency, and even
on ‘micro’ scale systems 90% peak efficiency is
achievable.
• With more spear-jets the Pelton turbine would operate at
high efficiency over an even wider flow range.
• Thus pelton wheels are only ideal for low power

13. • Turgo turbines were
developed by Gilkes in
1919 and are a
development of the Pelton
turbine.
• They can handle a higher
flow rate than a physically
similar-sized Pelton turbine
and the rotor is slightly
cheaper to manufacture.
• In most other respects they
are very similar to Pelton
turbines.

14. • The main physical difference is that the water jet
strikes one side of the rotor and exits from the
opposite side.

15. • Crossflow turbines are widely used on small hydro sites with
typical power outputs from 5 kW up to 100 kW till 3MWon the
very largest systems.
• They will work on net heads from just 1.75 metres all of the way
to 200 metres, though there are more appropriate turbine
choices for sites with heads above 40 metres.
• They will work on average annual flows as low as 40
litres/second up to 5 m3/s, though on the higher flow rates there
may be better other turbine types to consider.

16. • The water flows over and under the inlet guide-vane
which directs flow to ensure that the water hits the rotor
at the correct angle for maximum efficiency.
• . Most of the power is extracted by the upper blades
(roughly 75%) and the remaining 25% by the lower
blades.
• One of the advantages of a crossflow turbine is that it is
self-cleaning to a degree.
• The water exits the rotor and falls into the draft tube,
which can be 1/3rd of net head.
• In good quality crossflows the guide-vanes fit the turbine
casing with such precision that they can stop the water
flow 100%.

17. • The peak efficiency shown of
86% is a little high: 82% is more
realistic for a high quality
crossflow turbine.
• Crossflows are available in a
number of rotor diameters,
normally in 100 mm steps from
100 mm to 500 mm.
• The smaller diameters are for
higher-head sites.

18. • A reaction turbine develops power from the combined
action of pressure and moving water.
• The runner is placed directly in the water stream flowing
over the blades rather than striking each individually.
• Reaction turbines are generally used for sites with lower
head and higher flows than compared with the impulse
turbines.
• It includes propeller turbines such as bulb turbine,
straflo, tube turbine, kaplan turine,etc., and francis
turbines.

19. • A propeller turbine generally has a runner with three
to six blades in which the water contacts all of the
blades constantly.
• Through the pipe, the pressure is constant; if it isn't,
the runner would be out of balance. The pitch of the
blades may be fixed or adjustable.
• There are several different types of propeller
turbines:
• BULB TURBINE: The turbine and generator are a
sealed unit placed directly in the water stream.
• STRAFLO: The generator is attached directly to the
perimeter of the turbine.
• TUBE TURBINE: The penstock bends just before or
after the runner, allowing a straight line connection to
the generator.

20. • A Kaplan turbine is
basically a propeller with
adjustable blades inside a
tube.
• It is an axial-flow turbine,
which means that the flow
direction does not change
as it crosses the rotor.
• The inlet guide-vanes can
be opened and closed to
regulate the amount of flow
that can pass through the
turbine.

21. • The rotor blade pitch is also adjustable, from a flat profile for
very low flows to a heavily-pitched profile for high flows.
• Kaplan turbines could technically work
across a wide range of heads and flow
rates, but are relatively expensive.
• They are used on sites with net heads from 1.5 to 30 metres
and peak flow rates from 3 m3/s to 30 m3/s.
• Such systems would have power outputs ranging from 75 kW
up to 1 MW.
• The smallest good quality Kaplan turbines available have rotor
diameters of 600 mm and the largest rotors available have 3 to
5 metre diameters.

22. • There are variants of Kaplan turbines that only have
adjustable inlet guide-vanes or adjustable rotor blades,
which are known as semi-Kaplan’s.
• Although the performance of semi-Kaplan’s is
compromised when operating across a wide flow range.

24. • It was named after James
Bicheno Francis (1815-
1892), the American
engineer who invented the
apparatus in 1849.
• The Francis turbine is a
reaction turbine designed
to operate fully submerged.
• It has a runner with fixed
buckets (vanes), usually
nine or more.

25. • Water is introduced just above the runner and all around
it and then falls through, causing it to spin.
• Francis turbines have the highest efficiencies of all hydro
electric turbines – typically over 95 per cent.
• In addition to this high efficiency, they can cover a wide
range of heads between 30 m and 300 m, and have the
widest and highest range of power outputs.
• Large scale turbines used in dams are capable of
delivering over 500 MW of power from a head of water of
around 100 metres with efficiencies of up to 95%

26. • Archimedean screws are
relatively newcomers to the
small-scale hydro world having
only been used over the last
ten years.
• They have been particularly
used in sewage treatment
works.
• They can work efficiently on
heads as low as 1 metre,
though are not generally used
on heads less than 1.5 m (for
economic reasons).

27. • The water enters the screw at the top and the weight of
the water pushes on the helical flights, allowing the water
to fall to the lower level and causing the screw to rotate.
• Single screws can work on heads up to 8 metres, but
above this multiple screws are generally used.
• The maximum flow rate through an Archimedean screw is
determined by the screw diameter.
• The smallest screws are just 1 metre diameter and can
pass 250 litres / second and larger screws are 5 metres
in diameter with a maximum flow rate of around 14.5
m3/s.
• In terms of power output, the very smallest Archimedean
screws can produce as little as 5 kW, and the largest 500
kW.

28. • Archimedean screws typically rotate at around 26 rpm,
but when the top of the screw is connected to a gearbox,
the speed increases to 750-1500 rpm to make it
compatible with standard generators.
• Though they rotate relatively slow they can splash water
around, which is reduced by the use of a splash guard.
• Good quality Archimedean screws have a design life of
30 years

29. • A significant advantage of Archimedean screws is their
debris tolerance.
• The low rotational speed and large flow-passage
dimensions of Archimedean screws also allow fish to
pass downstream through the screw in relative safety.

30. • The maximum power output is entirely dependent on how
much head and flow is available at the site.
• Power output is given by: P = m x g x Hnet x System
efficiency
Where, P = Power, measured in Watts (W),
m = Mass flow rate in kg/s,
g = the gravitational constant, which is 9.81 m/s2,
Hnet = the net head.
• For a ‘typical’ small hydro system the turbine efficiency would
be 85%, drive efficiency 95% and generator efficiency 93%, so
the overall system efficiency would be 0.85 x 0.95 x 0.93 =
0.751 or 75.1%.
• Therefore for a head of 2.25m, a flow rate of 3 m3/s, the
maximum power output of the
system=3,000x9.81x2.25x0.751=49.7kW.

31. Maximum Power Output Estimated Project Cost £ / kW installed
5 kW £100k £20k
25 kW £190k £7.5k
50 kW £330k £6.5k
100 kW £560k £5.6k
250 kW £1.13M £4.5k
500 kW £1.86M £3.7k

32. Maximum Power Output Estimated Annual Operational Costs
5 kW £2,200
25 kW £4,000
50 kW £6,300
100 kW £11,000
250 kW £25,000
500 kW £48,300

33. • Good head
• Good flow
• Simple site layout with main parts close together
• Good grid connection
• Good site access
• Single ownership of the site, or cooperative neighbours
• Not too many environmental sensitivities

34. • The table shows the minimum annual mean (i.e.
average) flow rate required for a given head to generate
a maximum power output of 25 kW
Low-
head
Hydropo
wer Sites
High-
head
Hydropo
wer Sites
Max.
Power
Output
GrossHea
d
2 m
GrossHea
d
5 m
GrossHea
d
10 m
GrossHea
d
25 m
GrossHea
d
50 m
GrossHea
d
100 m
25 kW 1.9 m3/s 0.75 m3/s 0.38 m3/s 0.15 m3/s 75 litres/s 38 litres/s