Power from renewable energy

POWER PLANT ENGINEERING
S.BALAMURUGAN - M.E
ASSISTANT PROFESSOR
MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEERING & TECHNOLOGY
UNIT 4 – POWER FROM RENEWABLE ENERGY

ME 6701 POWER PLANT ENGG. S.BALAMURUGAN AP/MECH AAACET

HYDRO ELECTRIC POWER PLANT

Water reservoir:
Continuous availability of water is the basic necessity for a hydro-electric plant. Water
collected from catchment area during rainy season is stored in the reservoir. Water surface in
the storage reservoir is known as head race.
Dam:
The function of a dam is to increase the height of water level behind it, which
ultimately increases the reservoir capacity. The dam also helps to increase the working head of
the power plant.
Spillway:
Water in the dam after a certain level in the reservoir overflows through spillway
without allowing the increase in water level in the reservoir during rainy season.
Pressure tunnel:
It carries water from the reservoir to surge tank.
Penstock:
Water from surge tank is taken to the turbine by means of pen stocks, made up of
reinforced concrete pipe or steel.
Surge tank:
There is sudden increase of pressure in the penstock due to sudden backflow of
water, as load on the turbine is reduced. The sudden rise of pressure in the penstock is known
as water hammer. The surge tank is introduced between the dam and the power house to keep
in reducing the sudden rise of pressure in the penstock. Otherwise penstock will be damaged
by the water hammer.

Water turbine:
Water through the penstock enters into the turbine through an inlet valve. Prime motors
which are in common use are pelton turbine, francis turbine and kalpan turbine. The potential
energy of water entering the turbine is converted into mechanical energy. The mechanical energy
available at the turbine shaft is used to run the electric generator. The water is then discharged
through the draft tube.
Draft tube:
It is connected to the outlet of the turbine. It allows the turbine to be placed over tail
race level. Due to its shape, the water flowing through the tube is decelerated & it comes out with
minimum kinetic energy.
Tail race:
Tail race is a water way to lead the water discharged from the turbine to the river. The
water held in the tail race is called tail race water level.
Step-up transformer:
Its function is to raise the voltage generated at the generator terminal before
transmitting the power consumers.

TYPES OF HYDRO ELECTRIC POWER PLANT
Conventional Plants:
Conventional plants use potential energy from dammed water. The energy extracted
depends on the volume and head of the water. The difference between height of water level
in the reservoir and the water outflow level is called as water head.
Pumped Storage Plant:
In pumped storage plant, a second reservoir is constructed near the water outflow from the
turbine. When the demand of electricity is low, the water from lower reservoir is pumped
into the upper (main) reservoir. This is to ensure sufficient amount of water available in the
main reservoir to fulfill the peak loads.
Run-Of-River Plant:
In this type of facility, no dam is constructed and, hence, reservoir is absent. A portion of
river is diverted through a penstock or canal to the turbine. Thus, only the water flowing
from the river is available for the generation. And due to absence of reservoir, any
oversupply of water is passed unused.

TYPES OF HYDRO ELECTRIC POWER PLANT

KAPLAN VS FRANCIS TURBINE
• Radially in ward or mixed flow
Turbine
• very large number of blades 16 to 24
• France Turbine disposition of shaft is
in vertical or horizontal direction
• Runner vanes are not adjustable
• medium head is required
• medium flow rate is required
• Kaplan Turbine is partially axial
flow
• very small number of blades 3 to 8
• Kaplan Turbine disposition of shaft is
only in vertical direction
• Runner vanes are adjustable
• very low head is required
• very large flow rate is required

GOVERNING OF TURBINES
Steam Turbine Governing is the procedure of monitoring and controlling the flow rate of steam
into the turbine with the objective of maintaining its speed of rotation as constant. The flow
rate of steam is monitored and controlled by interposing valves between the boiler and the
turbine

SITE SELECTION FOR HYDRO ELECTRIC
POWER PLANT
• Availability of water
• Water storage
• Water Head
• Accessibility of the site
• Distance from the load center
• Type of land of the site
– Cheap & Rocky – Impervious Rock
– Rock – Strong enough to withstand the stresses
transmitted from Dam & Thrust of water

WIND ENERGY
• What is wind?
Wind is air in motion. It is produced by the uneven heating of the earth’s surface
by the sun.
• The earth’s surface is made of various land and water formations, it absorbs the
sun’s radiation unevenly.
• As the sun warms the Earth's surface, the atmosphere warms too.
• Warm air, which weighs less than cold air, rises. Then cool air moves in and replaces
the rising warm air. This movement of air is what makes the wind blow.
• Two factors are necessary to specify wind: speed and direction.

WIND TURBINES

COMPONENTS OF WIND TURBINE
• Anemometer: Measures the wind speed and transmits wind speed data to the
controller.
• Blades: Lifts and rotates when wind is blown over them, causing the rotor to
spin. Most turbines have either two or three blades.
• Brake: Stops the rotor mechanically, electrically, or hydraulically, in emergencies.
• It includes Brake pad, Brake shoe, brake solenoid, Oil reservior, Accumulator,
Hydraulic pump & Hydraulic control
• Controller: Starts up the machine at wind speeds of about 3.5 m/s and shuts off
the machine at about 56 m/s. Turbines do not operate at wind speeds above
about 56 m/s because they may be damaged by the high winds.
• Gear box: Connects the low-speed shaft to the high-speed shaft and increases
the rotational speeds from about 30-60 rotations per minute (rpm), to about
1,000-1,800 rpm; this is the rotational speed required by most generators to
produce electricity. The gear box is a costly (and heavy) part of the wind turbine
and engineers are exploring "direct-drive" generators that operate at lower
rotational speeds and don't need gear boxes.
• Generator: Produces 50-cycle AC electricity; it is usually an off-the-shelf
induction generator.

High-speed shaft: Drives the generator.
Low-speed shaft: Turns the low-speed shaft at about 30-60 rpm.
Nacelle: Sits a top the tower and contains the gear box, low- and high-speed
shafts, generator, controller, and brake. Some nacelles are large enough for a
helicopter to land on.
Pitch: Turns (or pitches) blades out of the wind to control the rotor speed, and to
keep the rotor from turning in winds that are too high or too low to produce
electricity.
Rotor: Blades and hub together form the rotor.
Tower: Made from tubular steel, concrete, or steel lattice. Supports the structure
of the turbine. Because wind speed increases with height, taller towers enable
turbines to capture more energy and generate more electricity.
Wind direction: Determines the design of the turbine. Upwind turbines—like the
one shown here—face into the wind while downwind turbines face away.
Wind vane: Measures wind direction and communicates with the yaw drive to
orient the turbine properly with respect to the wind.
Yaw drive: Orients upwind turbines to keep them facing the wind when the
direction changes. Downwind turbines don't require a yaw drive because the wind
manually blows the rotor away from it.
COMPONENTS OF WIND TURBINE

EXPRESSION FOR POWER DEVELOPED BY WIND TURBINE
• P α
1
2
m V2
• P = Cp
1
2
m V2
• Mass Flow Rate = m = ρ A V
• ρ = Air Density, 1.226 kg/m3 at 1 atm & 15° C
• P = Cp
𝟏
𝟐
ρ A V3
• A =
π
4
d2, d-Sweep or diameter of rotor
• Cp – Power Coefficient
• A – Swept Area
• V – Wind Velocity
• P – Power in Wind Turbine

Sound pressure is measured in decibels (dB).
The average person can hear sounds down to about 0 dB, the level of rustling leaves. Some
people with very good hearing can hear sounds down to -15 dB.
If a sound reaches 85 dB or stronger, it can cause permanent damage to your hearing. The
amount of time you listen to a sound affects how much damage it will cause.

TIDE FORMATION

TIDAL POWER PLANT
• It is a periodic rise & fall of water level in sea due to the attraction
of moon & sun on the water of the earth.
• Potential energy of the high tide is more than low tide. This
difference is called Tidal Energy.

OTEC – OCEAN THERMAL ENERGY CONVERSION
• OTEC takes advantage of the temperature differential
between the relatively warm surface waters (25° C) and the
significantly cooler deep waters (5° C at 1000 m) to drive an
electrical turbine.
• Open-cycle - Warmer surface water is flash evaporated in a
very low-pressure environment and the water vapour is then
used to drive the electrical generator. The vapour is
condensed using the cold sea water pumped up from below
to complete the cycle. This system has the advantage of
generating desalinated water.
• Hybrid - Firstly electricity is generated using the closed cycle
system, however instead of discharging the warm seawater it
is evaporated using the open-cycle OTEC system and then
later condensed with cool water. This has the advantage of
harnessing the advantages of both closed- and open-loop
systems

OTEC – CLOSED CYCLE
• Warm water (25°C) is used to ‘flash evaporate’ a working fluid such as
Ammonia, Propane or Chlorofluorocarbon (CFC) with a much lower boiling
point than water by passing it over a heat exchanger.
• The vaporized working fluid drives an electrical turbine before condensing
as it comes into contact with a heat exchanger cooled with cool sea water
(5°C), which is then pumped back to the evaporator to start the cycle once
again.
• Closed-cycle systems operate more efficiently than open-cycle but are
often smaller in scale as the secondary working fluid operates at a higher
pressure.
Ammonia = Boiling Point - (-33.3°C)
Titanium or Alloy of copper & Nickel

FLASH CHAMBER
• Flash steam is produced when high pressure
condensate is discharged to a lower pressure.
• The word ‘flash’ describes the way it is formed.
• When this pressurized condensate is exposed to
atmospheric pressure, it has energy more than it
can contain at atmospheric pressure.
• This excess energy is used to convert a portion of
this condensate into steam. This phenomenon is
called as flashing and the steam so generated is
referred to as flash steam.

GEOTHERMAL POWER PLANT• The renewable type thermal energy that is naturally present in the interior
of the earth surface.
• Generated from radioactive decay and continual heat loss from Earth's
formation. Temperatures at the core–mantle boundary may reach over
4000 °C.
• Geo – of the earth, Thermal – Process of Heating
• Mantle – the part of the earth that lies between the crust & the core.
Applications
Generation of Electric Power
Space Heating for Buildings
Industrial process heat
At depth 3 km – 8 × 1021 joules
At depth 10 km – 4 × 1022 joules
The Effluent will be salty & contains
Sodium, Potassium.
In some cases, Lithium, Fluorine, Boron &
Arsenic – Severe Pollution Problem.
Treatment Plant

GEOTHERMAL POWER PLANT
Hot Solid rocks – Water don’t have a access – Absence of Ground water & Low permeability of
rock
Man made passages – Fractured at suitable depth
Cold Water injected - Steam or Hot Water – Turbine – Power Generation
MAGMATIC (Molten Rock) Chamber System
Extraction of heat energy from hot magma (1450°C)
Difficult – Energy recovery from deeper sources (Drilling distance)
Solidification of MAGMA around heat exchanger tubes

GEOTHERMAL POWER PLANT
• Dry steam raised from the
underground by the continuous
supply of water
• Centrifugal Separator – Liquid
particles & suspended solid are
removed
• Water at high temperature coming out from
hot well. It is made to flash in the flash
chamber to produce steam.
• Steam Turbine
• Condensed steam & Brine from separator is
taken back to Geo thermal field.
• Corrosion Issue (Wet) – Requires large land
area

BIO-GAS POWER PLANT
• Anaerobic Digestion – Biomass waste ( Animal waste, aquatic waste, Agro industry waste,
etc.) – Fermentation – Biogas
• Biogas – Methane(55%) – Carbon dioxide(35%) – Hydrogen (5%) – Other gas & moisture (5%)
• Calorific Value – 23MJ/Kg Petrol CV – 45.8 MJ/Kg

SOLAR ENERGY
• Sun emits 3.7 × 1026 watts.
• Earth intercepted the energy of 1.7 × 1017 watts
• The energy emitted by sun for 3 minutes = World
energy consumption for year
• Sun radiation = Visible light + Infrared (Heat)

SOLAR PHOTO VOLTAIC CELL
Semiconductor materials – Silicon, Cadmium, Telluride, Gallium arsenide
Principle
• Creation of pairs of positive & negative charges (Electron hole pairs) in the solar cell by
absorbed solar radiation
• Separation of the positive & negative charges by a potential gradient with in the cell

Glass Reflecting surface – 10-14
panels (manufacture &
transportation – Rectangular)
Plastic reflecting surface – Low
in reflectance – Strength – less
cost – Air supported plastic
bubble protects from wind load

DIRECT ENERGY CONVERSION SYSTEMS
Energy conversion devices accept energy as
Heat & produce mechanical work
Fuel - Heat(Steam) - Mechanical work – Electricity
Direct Energy Conversion Devices
Natural available energy – Electricity (without mechanical)
• Energy Sources – Solar, Thermal, Chemical
– Photo Voltaic power system
– Fuel cell
– Thermoelectric conversion system
– Thermionic conversion system
– Magneto hydrodynamic system

FUEL CELL
• Electro chemical device
• Chemical energy of fuel Directly to Low voltage,
• It is a Primary battery in which the fuel & oxidizer are stored external to the battery & fed
to it as needed.
• Fuel gas diffuses through the anode & is oxidized, releasing electrons to the external circuit
• The oxidizer diffuses through the cathode & is reduced by the electrons
• Hydrogen – Oxygen fuel cell = Potassium hydroxide (KOH) – Electrolyte
• Chemically treated electrodes – To repel the electrolyte – minimum leakage of electrolyte
• Conversion efficiency high
• Little maintenance, can be installed near load center – reducing transmission loss
• Doesn’t make noise – Little time to go into operation
• High cost – Low service life

• Fuel preparation – Receiving, processing, filtering, heating the fuel
• Fuel cell - Chemical energy of fuel Directly to Low voltage
• Electric power conditioning system – DC-AC convertor – Regulate three phase power supply
• Switch gear & Supply system – Delivers power to load. It includes switches, circuit breakers,
Protect & isolate the fuel cell fro the grid
• Control system - To control voltage, current, fuel input & temperature. This can be done by
controlling the fuel supply by feed back control
• Heater – In High temperature fuel cell, to maintain the working temperature of the fuel &
electrolyte
• Applications – Domestic use, Automotive vehicles, Central power stations, Space power
plant

THERMOELECTRIC CONVERSION SYSTEM
•SEEBECK EFFECT – If two dissimilar materials are joined to form a loop & the two junctions
maintained at different temperatures, an e.m.f will be set around the loop. E = α ΔT.
•α – seebeck coefficient, ΔT – Temperature difference (Thermocouple)
•Converts heat flow into DC electrical power
•Two thermoelectric materials required: P-type (red) and N-type (yellow)
•Material – Bismuth telluride alloyed with Bismuth selenide, Antimony telluride
•Several thermocouples are connected in series to increase voltage & Power. Then DC to AC
•Source of Heat – Small oil or Gas Burner, a radio isotope, Direct solar radiation
Thermocouple
Hot & Cold junctions
600° C & 200° C = 0.1 V & 2 A
1 kW device = 5000 couples in series

THERMIONIC GENERATOR
• Work function (eV) – The energy required to extract an electron from the metal. Varies with
nature of material & its surface.
• It comprises a heated cathode ( Electron Emitter) & an anode (Electron collector),
Separated by a vacuum. Distance between anode & cathode is one millimeter.
• The electrode with a large work function is maintained at a higher temperature than one
with the smaller work function.
• The heat is which is supplied to the cathode raises the energy of its electron to such a level
that it enables them escape from the surface & flow to anode.
• At anode, the energy of electrons appears partially as heat, removed by cooling & Partially
received as electrical energy delivered to the external circuit.
• Heat Source – Fossil fuel, Nuclear fuel, Solar energy
• Emitter – High Electron Emission with a low rate of deterioration.
• Collector – it should have a low work function. (Molybdenum)
Thermionic Emission –
Emission of Electrons when
it is heated.

MAGNOHYDRODYNAMICS SYSTEM (MHD)
• It is a device which converts heat energy of a fuel directly into electrical energy
without a conventional electric generator.
FARADAY’S LAW OF ELECTROMANETIC INDUCTION
• When a conductor and a magnetic field move in respect to each other, an electric
voltage is induced in the conductor. The conductor may be solid, Gas or liquid.
• This device uses this principle by forcing a high pressure high temperature
combustion gas through a strong magnetic field.
• Seed Material – Potassium Carbonate – To increase the Electrical Conductivity

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