Electrical Power Generation Notes

7/25/2019 Electrical Power Generation Notes

1/20Vinayaka BG, Asst.Professor, Dept of E& E, BI ET, Davanagere

Unit 1

SOURCES OF ELECTRICAL POWER

Syllabus: Wind, solar, fuel cell, tidal, geo-thermal, hydro-electric, thermal-steam, diesel, gas, nuclear power

plants (block diagram approach only).Concept of co-generation. Combined heat and power distributed

generation.

Discuss conventional and non conventional energy in generation. Give examples

for each method.

There are two types of energy sources

Conventional (non-renewable) sources

non-conventional (renewable) sources

Conventional energy sources:

The sources of energy which are exhaustible in nature are called conventional

energy sources.

The energy sources which once used cannot be recovered any more. They are

depleting in nature

The sources of energy which are used for the mass generation of power are

called conventional energy sources.

Ex: 1) Diesel

2) Gas

3) Coal

4) Nuclear

Non-conventional sources or renewable energy sources:

JUNE 11, 12. 4 M



These energy sources are available abundantly in nature and they can be

reused again.

The energy sources which are non-exhaustible in nature are called Non-

conventional sources.

Ex: 1) Solar energy

2) Wind energy

3) Tidal energy

4) Geo-thermal energy

5) Biomass energy6) Ocean thermal energy

7) Biogas energy

8) Fuel cells



WIND ENERGY:

Wind flow is created as an effect of solar energy which creates low and high

pressure regions on the earth due to heating.

Wind energy is inexhaustible, plentiful and pollution free source of energy.

Wind possesses energy by virtue of its motion. Any device capable of slowing

down the motion of air can convert its energy into useful work.

Wind mills or wind energy converters converts wind power into electrical

power.

The typical system range from 30kW for individual units to 5 MW for

combined multiple units.

Mention any three advantages and three disadvantages of wind energy

conversion system.

Advantages

It is renewable source of energy.

It can be installed any locations where topographical conditions are suitable.

It is non-polluting in nature, so it has no adverse influence on the

environment.

These plants avoid fuel provision and transport.

Cost of generation is low.

Disadvantages

Wind energy available in fluctuating in nature.

It requires large area to collect the energy.

Noisy in operation.

Wind energy requires storage capacity because of its irregularity.

Power generated is quite small.

It is site specific.

DEC 09, 6 M



Explain the working of wind energy conversion system with block diagram

OR

With a neat sketch, explain the basic working principle of wind energy conversion

system.

Figure 1 : Block diagram of wind energy conversion system

Aero turbine converts wind energy into rotary mechanical energy.

This aero turbine requires pitch control and yaw control for proper operation.

Mechanical interface consisting of a step up gear and suitable coupling to

transmit the rotary mechanical energy into electrical generator.

The generator converts mechanical energy into electrical energy.

The output of the generator is connected to the load or power station.

The controller senses the wind direction, wind speed, generator output and

other necessary performance quantities & generates a control signal to take

proper corrective actions.

JUNE 09, DEC 10, 6 M

JUNE 12, 6 M



FUEL CELLS:

Write a short note on fuel cell.

A fuel cell is a device that converts the chemical energy from a fuel into

electricity through a chemical reaction with oxygen or another oxidizing agent .

Hydrogen is the most common fuel, but hydrocarbons such as natural gas and

alcohols like methanol are sometimes used. Fuel cells are different from

batteries in that they require a constant source of fuel and oxygen to run, but

they can produce electricity continually for as long as these inputs are supplied.

There are many types of fuel cells, but they all consist of an anode

(negative side), acathode (positive side) and anelectrolyte that allows charges to

move between the two sides of the fuel cell. Electrons are drawn from the

anode to the cathode through an external circuit, producing direct current

electricity. As the main difference among fuel cell types is the electrolyte, fuel

cells are classified by the type ofelectrolyte they use. Fuel cells come in a variety

of sizes. Individual fuel cells produce very small amounts of electricity, about 0.7

volts, so cells are "stacked", or placed in series or parallel circuits, to increase the

voltage and current output to meet an applications power generation
http://en.wikipedia.org/wiki/Fuel_cell#cite_note-0http://en.wikipedia.org/wiki/Fuel_cell#cite_note-0http://en.wikipedia.org/wiki/Fuel_cell#cite_note-0http://en.wikipedia.org/wiki/Methanolhttp://en.wikipedia.org/wiki/Battery_%28electricity%29http://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Cathodehttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Anodehttp://en.wikipedia.org/wiki/Battery_%28electricity%29http://en.wikipedia.org/wiki/Methanolhttp://en.wikipedia.org/wiki/Fuel_cell#cite_note-0http://en.wikipedia.org/wiki/Fuel_cell#cite_note-0



requirements. In addition to electricity, fuel cells produce water, heat and,

depending on the fuel source, very small amounts ofnitrogen dioxide and other

emissions. The energy efficiency of a fuel cell is generally between 40-60%, or

up to 85% efficient if waste heat is captured for use.

TIDAL ENERGY:

With a neat schematic diagram, explain the working of tidal power plant.

What is tidal power? Tide is periodic rise and fall of the water level of thesea. Tides occur due to the attraction of seawater by the moon. These tides can

be used to produce electrical power which is known as tidal power.

It is another source of renewable energy. The large scale up and down

movement of sea water represents an unlimited source of energy and a part of

this energy can be converted into electrical energy.

When the water is above the mean sea level, it is called flood tide and

when the level is below the mean level, it is called ebb tide.

The main feature of tidal cycle is the difference in the water elevations at

high tide and at low tide, this differential head could be utilised in operating the

DEC 09, 4 M
http://en.wikipedia.org/wiki/Fuel_cell#cite_note-1http://en.wikipedia.org/wiki/Fuel_cell#cite_note-1http://en.wikipedia.org/wiki/Fuel_cell#cite_note-1http://en.wikipedia.org/wiki/Nitrogen_dioxidehttp://en.wikipedia.org/wiki/Nitrogen_dioxidehttp://en.wikipedia.org/wiki/Fuel_cell#cite_note-1



hydraulic turbine, the tidal energy converted into electrical energy by means of

attached generator.

A dam is constructed in such a way that a basin gets separated from the sea and a

difference in the water level is obtained between the basin and sea. Theconstructed basin is filled during high tide and emptied during low tide passing

through sluices and turbine respectively. The Potential energy of the water

stored in the basin is used to drive the turbine which in turn generates electricity

as it is directly coupled to an alternator.

Explain with sketches the working of single basin and double basin tidal power

plant.

Single basin tidal plant:

It has only one basin schemeSingle basin scheme can generate power intermittently.

In single basin system only one basin interacting with sea

The sea and basin are separated by dam or barrage or dyke.

The sluice ways are located conveniently along the dam.

The flow of water between sea and dam is provided by rise and fall odf

tidal water level.

Along with sluice gates the dam also contains low head turbine sets

DEC 07, JUNE 10, 6 M



Double basin power plant:It requires two separate but adjacent basins. In

one basin called upper basin (or high pool), the water level is maintained

above that in the other, the low basin (or low pool). Because there isalways a head between upper and lower basins, electricity can be

generated continuously, although at a variable rate.

In this system the turbines are located in between the two adjacent basins,

while the sluice gates are as usual embodied in the dam across the mouths

of the two basins.

At the beginning of the flood tide, the turbines are shut down, the gates of

upper basin A are opened and those of the lower basin B are closed. The

basin A is thus filled up while the basin B remains empty. As soon as the

rising water level in A provides sufficient difference of head between the

two basins, the turbines are started. The water flows from A to B through

the turbines, generating power. The power generation thus continues

simultaneously with the filling up the basin A.

At the end of the flood tide when A is full and the water level in it is themaximum, its sluice gates are closed. When the ebb tide level gets lower



than the water level in B, its sluice gates are opened whereby the water

level in B, which was arising and reducing the operating head, starts falling

with the ebb. This continues until the head and water level in A is sufficient

to run the turbines. With the next flood tide the cycle repeats itself.

Advantages of tidal power:

Inexhaustible

Free from pollution

These plants do not demand large area of valuable land because they

are on bays or sea shore

Peak demand can be effectively met when it works in combination with

thermal or hydroelectric plants.

Limitations:

Variable output due to variations in tidal power plant

There are feasible only in certain range of tidal cycle

Sea water is corrosive and it was feared that machinery may get corroded

Construction is difficult

High cost



GEO THERMAL POWER PLANT:

With a neat sketch explain working of geo-thermal power plant

OR

With a neat block diagram, explain working ofgeo-thermal power plant

The centrifugal separator removes particulate matter from the steam. The steam is

admitted into the steam turbine . The steam expands in the turbine buckets

producing rotary kinetic energy. The low pressure steam at the exhaust of the

turbine is condensed in condenser the condensate is re injected into the earth via

the reinjection wall.

Cooling water for condensing the steam is circulated through the cooling tower by

means of cooling water pump. The synchronous generator generate electrical

power at high voltage 50 Hz A.C. The turbine and generator form one unit.Completepower plants has several units.

DEC 10, DEC 09, 6 M

DEC 08, 6 M



Geothermal energy in the form of dry steam is converted into mechanical energy by

the turbine. The mechanical energy is converted to electrical energy by the

generator.

OCEAN THERMAL ENERGY CONVERSION:

Tropical oceans collect and store very large amount of solar energy. Utilization of

this energy with associated temperature difference and conversion of this thermal

energy into work and hence into electricity is the basis of ocean thermal energy

conversion (OTEC) systems.

OPEN CYCLE OTEC SYSTEM :

Open cycle refers to the utilization of sea water as the working fluid, wherein sea

water is flash evaporated under a partial vacuum. The low pressure steam is passed

through a turbine, which extracts energy from it, and then the spent vapour is

cooled in a condenser.

This cycle drives the name open from the fact that the condensate need not be

returned to the evaporator, as in the case of the closed cycle.

Instead, the condensate, can be utilized as desalinated water if a surface condenser

is used, or if a spray (direct-contact) condenser is used, the condensate is mixed

with the cooling water and the mixture is discharged back into the ocean.&schematic diagram of the open cycle system is shown in Fig.



SOLAR POWER:

With a neat schematic diagram, explain the working of a solar power plant. What

is the importance of this plant in the present energy crises in the world?

The basic components of solar power plant are also exactly identical to thermal

power plant except boiler is replaced by a flat plate solar collector.

The energy from solar radiation is collected and utilized to generate a steam to

run steam turbines. For obtaining reasonably high efficiency, concentration type of

collectors are used when steam is used as working fluid. The cost of concentrating

collector is more than flat plate collector. Therefore, new working fluid whose

saturation temperature is lower than that of water at considerably high pressures

are normally used in this type of power plant. But the thermal efficiency of the plant

will be low due to low temperature range.

This is more suitable in rural areas for house lighting and water pumping for

irrigation purpose.

1) Solar radiation does not disturb ecological balance.

2) It is available freely in nature.

3) It is non-depleting source.

4) It is easily available all over the wind.

DEC 10, JUNE 08 10 M



NUCLEAR POWER PLANT:

Nuclear reactor. It is an apparatus in which nuclear fuel (U235) is subjected to

nuclear fission. It controls the chain reaction* that starts once the fission is done. If

the chain reaction is not controlled, the result will be an explosion due to the fast

increase in the energy released.

A nuclear reactor is a cylindrical stout pressure vessel and houses fuel rods of

Uranium, moderator and control rods. The fuel rods constitute the fission material

and release huge amount of energy when bombarded with slow moving neutrons.

The moderator consists of graphite rods which enclose the fuel rods. The moderator

slows down the neutrons before they bombard the fuel rods. The control rods are of

cadmium and are inserted into the reactor. Cadmium is strong neutron absorber and

thus regulates the supply of neutrons for fission. When the control rods are pushed in

deep enough, they absorb most of fission neutrons and hence few are available for

chain reaction which, therefore, stops.

However, as they are being withdrawn, more and more of these fission neutrons

cause fission and hence the intensity of chain reaction (or heat produced) is increased.



Therefore, by pulling out the control rods, power of the nuclear reactor is increased,

whereas by pushing them in, it is reduced. In actual practice, the lowering or raising

of control rods is accomplished automatically according to the requirement of load.

The heat produced in the reactor is removed by the coolant, generally a sodium

metal. The coolant carries the heat to the heat exchanger.

Heat exchanger. The coolant gives up heat to the heat exchanger which is utilised in

raising the steam. After giving up heat, the coolant is again fed to the reactor.

Steam turbine. The steam produced in the heat exchanger is led to the steam turbine

through a valve. After doing a useful work in the turbine, the steam is exhausted to

condenser. The condenser condenses the steam which is fed to the heat exchanger

through feed water pump.

(iv) Alternator. The steam turbine drives the alternator which converts mechanical

energy into electrical energy. The output from the alternator is delivered to the bus-

bars through transformer, circuit breakers and isolators

GAS TURBINE POWER PLANTS:

(i) Compressor: The compressor used in the plant is generally of rotatory type.

The air at atmospheric pressure is drawn by the compressor via the filter



which removes the dust from air. The rotatory blades of the compressor

push the air between stationary blades to raise its pressure. Thus air at high

pressure is available at the output of the compressor.

(ii)

Combustion chamber: The air at high pressure from the compressor is led to

the combustion chamber via the regenerator. In the combustion chamber,

heat is added to the air by burning oil. The oil is injected through the burner

into the chamber at high pressure to ensure atomization of oil and its

thorough mixing with air. The result is that the chamber attains a very high

temperature (about 3000 0F). The combustion gases are suitably cooled to

13000F to 1500

0F and then delivered to the gas turbine.

(iii) Gas turbine: The products of combustion consisting of a mixture of gases at

high temperature and pressure are passed to the gas turbine. These gases in

passing over the turbine blades expand and thus do the mechanical work. The

temperature of the exhaust gases from the turbine is about 900 0F.

(iv) Alternator OR generator: The gas turbine is coupled to the alternator. The

alternator converts mechanical energy of the turbine into electrical energy.

The output from the alternator is given to the bus-bars through transformer,

circuit breakers and isolators.



COGENERATION:

What is co-generation? Explain the necessary block diagram of concept of co-

generation.

Write the concept of co-generation plant with neat block diagram.

Explain the concept of co-generation & discuss its benefits.

Discuss the benefits of co-generation.

Discuss the concept of co-generation, its merits & demerits

Cogeneration is a process capturing waste heat from manufacturing,

industrial process or heating systems and using it to generate electric power

Cogeneration is the concept of producing two forms of energy from one fuel.

One of the forms of energy must always be heat and the other may be

electricity or mechanical energy.

DEC 11, 8 M

JUNE 09, 6 M

JUNE 12, 6 M

JUNE 10, 6 M

DEC 09, 8 M



i)Topping Cycle

The input is first used to produce power and the exhaust heat from the

power producing prime mover is used to generate steam or used directly in

heating process.

Thermal energy is a byproduct used in this process.

This is most popular method of cogeneration.

ii) Bottoming Cycle

It is the reverse of topping cycle, utilizes waste heat from heating process

such as an industrial furnace, to produce electricity.

Primary fuel produces high temperature thermal energy.

Rejected heat is used to generate power

Suitable for manufacturing processes

The potential for cogeneration primarily in sugar, distilleries, petrochemicals

,rice industries steel, cement, fertilizers, paper industries etc.

Operational advantages:

1. Base load electrical supply

2. Security of supply

3. Increased diversity on heating and hot water

4. Steam raising capabilities

5. Tri-generation, using absorption/mechanical chillers for cooling

Financial advantages:

1. Reduced primary energy cost

2. Stabilized electricity cost over a fixed period



3. Flexible procurement solutions

4. Reduced investment in surrounding plants eg. Boilers

Environmental advantages:1. Improved fuel efficiency

2. Reduced CO2 emissions

3. No transmission losses

DISTRIBUTED GENERATION:

When small generators of capacities around 2 - 50 MW output are installed at

typical points in the area such that each of these generators supply power to a small

number of consumers nearby then it is called distributed generation. The generators

may be operated through renewable energy sources such as solar, wind or gas

turbines, small hydro or micro turbines as these are most economical choices.

Dispersed generation is use of still smaller generating units of less than 500 kW and

use for individual houses or small business. The distributed or dispersed generators

may be standalone or grid connected depending on the requirement.

Distributed generation proves to be economical as it requires to transmission

network and reduced need of distribution equipments. Another advantage is this

generation is portable or compact as compared to big power stations located far

away from consumers. Also they are modular and relocatable. The fuel cells and

micro gas turbines are two new types of techniques evolved in distributed

generation.

The main challenge is to upgrade existing technology and to promote development,

demonstration of new and upcoming technologies for widespread adaptation of

distributed generation.



Co-generation is defined as the sequential generation of two forms of

useful energy from a single primary energy source; typical two forms of energies

are mechanical energy and thermal energy. Mechanical energy may be used may

be used to either to drive an alternator to produce electricity or rotate anequipments like motor, compressor, pump or fans etc., for delivering different

services. Thermal energy may be used directly for the process for heating

purpose or indirectly to produce the steam generation, hot water or hot air for

dryer and chilled water generation for process cooling.

Generation of three different forms of energy from the single primary energy

source is called as Tri-generation, i.e., generation of Electricity, Steam or Hot

water and Chilled water from single source of primary fuel. Above both systems

is also called as Total Energy System

Thermal power plants are major sources of electricity supply in India. The conventional

method of power generation and supply to the customer is wasteful in the sense that only

about a third of the primary energy fed into the power plant is actually made to available

to the user in the form of electricity (Figure 1). In conventional power plant, efficiency is only

33% and remaining 65% of energy is lost. The major loss in the conversion process is the

heat rejected to surrounding water or air due to the inherent constraints of the different

thermodynamic cycles employed in power generation. Also of further losses of around 10-

15% are associated with the transmission and distribution of electricity in the electrical grid.

Through the utilization of the heat, the efficiency of the co-generation plant can reach 90%

or more. In addition, the electricity generated by the co-generation plant is normally used

locally, and then transmission and distribution losses will be negligible. Co -generation

therefore offers energy savings ranging between 15-40% when compared against the

supply of electricity and heat from the power stations and boilers.


20/20

With a neat schematic diagram, explain the working of a solar power plant. What

is the importance of this plant in the present energy crises in the world?

Figure : Schematic diagram of solar plant

THERMAL POWER PLANT:

DEC 10, JUNE 08 10 M

Electrical Power Generation Notes

Documents

Transcript of Electrical Power Generation Notes