Wind Energy : Properties of wind, availability of wind energy in India, wind
velocity and power from wind; major problems associated with wind power, wind
machines; Types of wind machines and their characteristics, horizontal and
vertical axis wind mills, elementary design principles; coefficient of performance
of a wind mill rotor, aerodynamic considerations of wind mill design, numerical
Tidal Power: Tides and waves as energy suppliers and their mechanics;
fundamental characteristics of tidal power, harnessing tidal energy, limitations.
Ocean Thermal Energy Conversion: Principle of working, Rankine cycle, OTEC
power stations in the world, problems associated with OTEC.
4. WIND ENERGY:
Winds are caused from 2 main factors:
• Heating & cooling of the atmosphere which generates convection
currents. Heating is caused by the absorption of solar energy on the
Earth’s surface & in the atmosphere.
• The rotation of the Earth with respect to atmosphere & its motion
around the sun
5. • The energy available in the wind over the Earth’s surface is estimated
to be 1.6×107 MW
• In India, high wind speeds are obtainable in coastal areas of Saurashtra,
Western Rajasthan & some parts of Central India.
• Data quoted by some scientists that for India wind speed value lies
between 5 Km/hr to 15-20 Km/hr
6. The problems associated with Utilizing wind energy
• The energy is available in dilute form, because of this conversion
machines have to be necessarily large.
• The availability of the energy varies considerably over a day and with
7. Advantages of Wind energy
• The wind energy is free, inexhaustible and does not need transportation.
• Wind mills will be highly desirable and economical to the rural areas which are far from
• Wind power can be used in combination with hydroelectric plants. Such that the water level
in the reservoir can be maintained for longer periods.
• Wind energy is friendly to the surrounding environment, as no fossil fuels are burnt to
generate electricity from wind energy.
• Wind turbines take up less space than the average power station. Windmills only have to
occupy a few square meters for the base; this allows the land around the turbine to be used
for many purposes, for example agriculture.
8. Disadvantage of Wind energy
The main disadvantage regarding wind power is down to the winds unreliability factor.
In many areas, the winds strength is too low to support a wind turbine or wind farm.
Wind turbines generally produce less electricity than the average fossil fueled power
station, requiring multiple wind turbines to be built in order to make an impact.
Wind turbine construction can be very expensive and costly to surrounding wildlife
during the build process.
The noise pollution from commercial wind turbines is sometimes similar to a small jet
engineIt has low power coefficient.
Careful survey is necessary for plant location.
9. Factors lead to increase wind Energy conversion:
Availability of high strength fiber composites for constructing large low-cost
Falling prices of power electronics.
Variable speed operation of electrical generators to capture maximum energy.
Improved plant operation, pushing the availability up to 95%.
Economy of scale, as the turbines & plants are getting larger in size.
Accumulated field experience (the learning curve effect) improving the capacity
10. WIND MACHINES:
1) Tower structure.
2) Rotor with two or three blades attached to the hub.
3) Shaft with mechanical gear.
4) Electrical generator.
5) Yaw mechanism, such as the tail vane.
6) Sensors and control.
12. Classification of wind mills
Based on the amount of the power generated
1) small (< 25 kW)
2) medium (25-100 kW),
3) large (100-1000 kW)
4) very large (>1000 kW)
Based on their rotation direction
1) Horizontal Axis Wind Turbines (HAWT)
2) Vertical Axis Wind Turbines (VAWT)
13. Based on the direction of receiving the wind
1) upwind wind turbines
2) down wind turbines
17. • Rotor must move more rapidly to capture same amount of wind
• Gearbox ratio reduced
• Added weight of counterbalance negates some benefits of lighter
• Higher speed means more noise, visual, and wildlife impacts
• Blades easier to install because entire rotor can be assembled on
• Captures 10% less energy than two blade design
26. The power in wind:
Wind possesses energy by virtue of its motion.
There are 3 factors determine the output from a wind energy converter,
1] the wind speed
2] The cross section of wind swept by rotor
3] The overall conversion efficiency of the rotor, transmission system &
generator or pump.
27. • Only 1/3rd amount of air is decelerating by the rotors & 60% of the
available energy in wind into mechanical energy.
• Well designed blades will typically extract 70% of the theoretical max,
but losses incurred in the gear box, transmission system & generator
could decrease overall wind turbine efficiency to 35% or less.
• The power in the wind can be computed by using the concept of
kinetics. The wind mill works on the principle of converting kinetic
energy of the wind to mechanical energy.
28. Major factors that have lead to accelerated development of the
wind power are as follows:
• Availability of high strength fiber composites for constructing large low-cost rotor
• Falling prices of power electronics.
• Variable speed operation of electrical generators to capture maximum energy.
• Improved plant operation, pushing the availability up to 95%.
• Economy of scale, as the turbines & plants are getting larger in size.
• Accumulated field experience (the learning curve effect) improving the capacity
• Short energy payback ( or energy recovery) period of about year.
29. Power in wind
• Kinetic energy = k.E= ½ mv2
• But m = ρAv and ρ = f(Z,T) where Z and T are elevation and
• Available wind Power =Pa = 1/8 ρπD2V3 ......Watts
31. Efficiency of wind Turbine (Power coefficient)
• Power coefficient =
where PT is the actual power developed by the turbine rotor.
• The max theoretical power coefficient is equal to 16/27 or 0.593
32. Rotor speed-wind velocity interaction
Where R is the radius of the Rotor.
It is the maximum theoretical torque. In practice the rotor shaft can
develop only a fraction of this maximum value.
Where CT is the torque coefficient and TT is the actual torque developed by the rotor.
33. TIP SPEED RATIO
Where Ω is the angular velocity and N is the rotational speed of the rotor. There is an
optimum λ for a given rotor at which the energy transfer is most efficient.
We know that power coefficient
34. The Betz limit
The maximum theoretical power coefficient of a horizontal axis wind
turbine is 16/27, known as the Betz limit.
39. Lift coefficient:
∗ 𝜌𝑣2 ∗ 𝐴 ∗ 𝐶𝐿
∗ 𝜌𝑣2 ∗ 𝐴
L -lift force, and CL- Coefficient of lift
∗ 𝜌𝑣2 ∗ 𝐴 ∗ 𝐶𝐷
∗ 𝜌𝑣2 ∗ 𝐴
41. Ocean energy sources may be broadly divided into the following three categories:
1. Tidal Energy.
2. Ocean Thermal Energy Conversion (OTEC).
43. TIDAL POWER PLANT
The periodic rise and fall of the water level of sea which are carried by the action
of the sun and moon on water of the earth is called the 'tide'.
Tidal energy can furnish a significant portion of all such energies which are
renewable in nature. The large scale up and down movement of sea water
represents an unlimited source of energy. If some part of this vast energy can be
converted into electrical energy, it would be an important source of hydropower.
44. Components of Tidal Power Plants
Power house: the turbines, electrical generator and other
auxiliary equipments are the main component of a power
Dam or Barrage: The function of dam to form a barrier
between the sea and basin or between one basin and the
other in case of multiple basins.
Sluice ways: the sluice ways are used either to fill the basin
during the high tide or empty the basin during the low tide ,
as per operational requirement. These are gate controlled
45. CLASSIFICATION OF TIDAL POWER PLANTS
1. Single basin arrangement
(i)Single ebb-cycle system
(ii) Single tide-cycle system
(iii) Double cycle system.
2. Double basin arrangement.
48. iii) Double cycle system:
In double cycle system the turbine is used to operate continuously irrespective of
the tides the turbine is rotate in clockwise and anticlockwise direction.
During the high tide water will allowed to flow to the barrage through turbine. At
the end of the high tide or at the beginning of the low tide water flows back to the
sea through turbine, during the backflow of water turbine rotates in opposite
direction, hence power can be generated in both the tides.
In this system the sluice ways are not present.
50. Advantages of tidal energy:
1. Tidal power is completely independent of the precipitation (rain) and its
uncertainty, besides being inexhaustible.
2. Large area of valuable land is not required.
3. When a tidal power plant works in combination with thermal or hydro-electric
system, peak power demand can be effectively met with.
4. Tidal power generation is free from pollution.
51. Limitations of tidal energy:
1. Due to variation in tidal range the output is not uniform.
2. Since the turbines have to work on a wide range of head variation (due to variable tide range) the
plant efficiency is affected.
3. There is a fear of machinery being corroded due to corrosive sea water.
4. It is difficult to carry out construction in sea.
5. As compared to other sources of energy, the tidal power plant is costly.
6. Sedimentation and silteration of basins are the problems associated with tidal power plants.
7. The power transmission cost is high because the tidal power plants are located away from load
53. Thermal Energy Conversion is an energy technology, which uses the ocean’s natural
temperature gradient to drive a turbine, which is connected to a generator. It is
desirable that the temperature difference between the warm surface water and the
cold deep water be at least 200C (680F).
OTEC systems are works on the basic relationship between pressure (P),
temperature (T) and volume (V) of a fluid, which can be expressed by the following
Ocean Thermal energy Conversion (OTEC)
54. There are basically three types of OTEC systems developed that can utilize sea water
temperature differentials they are
1. Closed Rankine cycle or vapour cycle or Anderson cycle
2. Open cycle or Claude Cycle or Steam Cycle
1. OTEC uses clean, renewable, natural resources. Warm surface seawater and cold water from the ocean
depths replace fossil fuels to produce electricity.
2. Suitably designed OTEC plants will produce little or no carbon dioxide or other polluting chemicals.
3. OTEC systems can produce fresh water as well as electricity. This is a significant advantage in island
areas where fresh water is limited.
4. There is enough solar energy received and stored in the warm tropical ocean surface layer to provide
most, if not all, of present human energy needs.
5. The use of OTEC as a source of electricity will help reduce the state's almost complete dependence on
imported fossil fuels.
1. OTEC-produced electricity at present would cost more than electricity generated from fossil fuels at
their current costs.
2. OTEC plants must be located where a difference of about 20º C occurs year round. Ocean depths must
be available fairly close to shore-based facilities for economic operation. Floating plant ships could
provide more flexibility.
3. No energy company will put money in this project because it only had been tested in a very small
4. Construction of OTEC plants and lying of pipes in coastal waters may cause localized damage to reefs
and near-shore marine ecosystems.
5. Construction of floating power plants is difficult.
6. Plant size is limited to about 100 MW due to large size of components.
7. High investment is required.