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NON CONVENTIONAL ENERGY SOURCES

DEPARTMENT OF MECHANICAL ENGINEERING, SVCE

SRI

CHAPTER 1

Syllabus: Energy source, India‟s production and reserves of commercial

energy sources, need for non-conventional energy sources, energy alternatives,

solar, thermal, photovoltaic. Water power, wind, biomass, ocean temperature

difference, tidal and waves, geothermal, tar sands and oil shale, nuclear (Brief

descriptions); advantages and disadvantages, comparison (Qualitative and

Quantitative).

INTRODUCTION

The word energy is derived from the Greek word “en-ergon” which means

„in-work’ or work content. The work output depends on the energy input. Energy is

the most basic infra-structure input required for economic growth & development

of a country. Thus, with an increase in the living standard of human beings, the

energy consumption also accelerated.

A systemic study of various forms of energy & energy transformations is

called energy science. While fossil fuels will be the main fuel for thermal power,

there is a fear that they will get exhausted eventually in the next century. Therefore

other systems based on nonconventional & renewable sources are being tried by

many countries. These are solar, wind, sea, geothermal & bio-mass.

The need for alternatives:

1. The average rate of increase of oil production in the world is declining & a peak

in production may be reached around 2015. There after the production will decline

gradually & most of the oil reserves of the world are likely to be consumed by the

end of the present century. The serious nature of this observation is apparent when

one notes that oil provides about 30% of the world„s need for energy from

commercial sources & that oil is the fuel used in most of the world„s transportation

systems.

2. The production of natural gas is continuing to increase at a rate of about 4%

every year. Unlike oil, there has been no significant slowdown in the rate of

increase of production. Present indications are that a peak in gas production will

come around 2025, about 10 years after the peak in oil production.



3. As oil & natural gas becomes scarcer, a great burden will fall on coal. It is likely

that the production of coal will touch a maximum somewhere around 2050.

4. Finally, it should be noted that in addition to supplying energy, fossil fuels are

used extensively as feed stock material for the manufacture of organic chemicals.

As resources deplete, the need for using fossil fuels exclusively for such purposes

may become greater.

Importance of Non-conventional energy resources:

The concern for environmental due to the ever increasing use of fossil fuels &

rapid depletion of these resources has led to the development of alternative sources

of energy, which are renewable & environmental friendly. Following points may

be mentioned in this connection.

1) The demand of energy is increasing by leaps & bounds due to rapid

industrialization & population growth, the conventional sources of energy will not

be sufficient to meet the growing demand.

2) Conventional sources (fossil fuels, nuclear) also cause pollution; there by their

use degrade the environment.

3) Conventional sources (except hydro) are non-renewable & bound to finish one

day.

4) Large hydro-resources affect wild-life, cause deforestation & pose various social

problems, due to construction of big dams.

5) Fossil fuels are also used as raw materials in the chemical industry (for

chemicals, medicines, etc) & need to be conserved for future generations.

Due to these reasons it has become important to explore & develop non-

conventional energy resources to reduce too much dependence on conventional

resources. However, the present trend development of nces indicates that these will

serve as supplements rather than substitute for conventional sources for some more

time to time.

India’s production & reserves of commercial sources:

i) Coal

Coal is the end product of a natural process of decomposition of

vegetable matter buried in swamps & out of contact with oxygen for



thousands of years. The word coal denotes a wide variety of solid

fuels. The varieties in approximate order of their formation are peat,

lignite, bituminous & anthracite coal.

The rate of production of coal in India over the last 50 years is

shown in fig. It can be seen that there has been an eleven-fold

increase in production from 1951 to 2004 & that the average

annual growth rate has been about 4.5%. In 2000, India‘s

production was 300mt, which was about 6.7% of the world‘s

production. India has fairly large reserves of coal.

Fig.1. Annual production of coal in India [production rate (Mt/Year] v/s Year

ii) Oil and Natural gas:

Fig.2 represents data on the annual production and consumption of

petroleum products in India. Fig.3 represents the production and consumption of

natural gas in India.

Oil and natural gas were formed hundred years ago from the prehistoric

plant and animals. it is believed that hydrocarbon formed by the thermal

maturation of organic matter buried deep in earth. over the millions of years under

extreme pressure and high temperature these organic matter converted to

hydrocarbons consisting of oil and gas. Hydrocarbons are present in the variety of

forms: koregen, asphalt, crude oil, natural gas, condensates, and coal in solid form.

Oil and gas production includes exploration, drilling, extraction, stabilization. The

underground traps of oil and gas are called reservoir. Various types of traps are

structural traps, stratigraphic traps and combination traps.



Fig.2.Annual production & consumption Fig 3. Annual production & consumption

of oil in India of Natural gas in India

iii) Water –power:

Hydropower is a renewable energy resource because it uses the Earth's water

cycle to generate electricity. Water evaporates from the Earth's surface, forms

clouds, precipitates back to earth, and flows toward the ocean. The movement of

water as it flows downstream creates kinetic energy that can be converted into

electricity. It is one of the indirect ways in which solar energy is being used. It is

used almost exclusively for electric power generation. Fig.4 represents data on the

annual production of hydropower in India.

A hydroelectric power plant consists of a high dam that is built across a

large river to create a reservoir, and a station where the process of energy

conversion to electricity takes place. The first step in the generation of energy in a

hydropower plant is the collection of run-off of seasonal rain and snow in lakes,

streams and rivers, during the hydrological cycle. The run-off flows to dams

downstream. The water falls through a dam, into the hydropower plant and turns a

large wheel called a turbine. The turbine converts the energy of falling water into

mechanical energy to drive the generator After this process has taken place

electricity is transferred to the communities through transmission lines and the

water is released back into the lakes, streams or rivers. This is entirely not harmful,



because no pollutants are added to the water while it flows through the hydropower

plant.

Fig.4. Data on the annual production of hydropower in India.

iv) Nuclear power

It is the use of nuclear reactions that release nuclear energy to generate heat,

which most frequently is then used in steam turbines to produce electricity in

a nuclear power plant. The term includes nuclear fission, nuclear decay and nuclear

fusion. Data on the electricity production from nuclear power is plotted in below

https://en.wikipedia.org/wiki/Nuclear_reaction

https://en.wikipedia.org/wiki/Nuclear_binding_energy

https://en.wikipedia.org/wiki/Steam_turbine

https://en.wikipedia.org/wiki/Nuclear_power_plant

https://en.wikipedia.org/wiki/Nuclear_fission

https://en.wikipedia.org/wiki/Nuclear_decay

https://en.wikipedia.org/wiki/Nuclear_fusion

https://en.wikipedia.org/wiki/Nuclear_fusion



fig. It is seen that the electricity produced has been generally increasing over the

years, as more units are getting commissioned

Miscellaneous Sources:

In India, the miscellaneous sources are renewable source like wind energy, biomass, small hydro-power. Among them wind energy is the main

contributor. The growth in installed capacity for wind energy & along with data on the electricity produced from the wind is as shown in below fig.

Classification of energy resources:

1. Based on usability of energy:

a) Primary resources: Resources available in nature in raw form is called primary

energy resources. Ex: Fossil fuels (coal, oil & gas), uranium, hydro energy. These

are also known as raw energy resources.

b) Intermediate resources: This is obtained from primary energy resources by one

or more steps of transformation & is used as a vehicle of energy.

c) Secondary resources: The form of energy, which is finally supplied to consume

for utilization. Ex: electrical energy, thermal energy (in the form of steam or hot

water), chemical energy (in the form of hydrogen or fossil fuels).

Some form of energies may be classified as both intermediate as well as secondary

sources. Ex: electricity, hydrogen.

2. Based on traditional use:



a) Conventional: Energy resources which have been traditionally used for many

decades. Ex: fossil fuels, nuclear & hydro resources

b) Non-conventional: Energy resources which are considered for large scale &

renewable. Ex : solar, wind & bio-mass

3. Based on term availability:

a) Non-renewable resources: resources which are finited, & do not get replenished

after their consumption. Ex : fossil fuels, uranium

b) Renewable resources: resources which are renewed by nature again & again &

their supply are not affected by the rate of their consumption. Ex : solar, wind, bio-

mass, ocean ( thermal, tidal & wave), geothermal, hydro

4. Based on commercial application:

a) Commercial energy resources: the secondary useable energy forms such as

electricity, petrol, and diesel are essential for commercial activities. The economy

of a country depends on its ability to convert natural raw energy into commercial

energy. Ex : coal, oil, gas, uranium, & hydro

b) Non-commercial energy resources: the energy derived from nature & used –

directly without passing through commercial outlet. Ex: wood, animal dung cake,

crop residue.

5. Based on origin:

a) Fossil fuels energy f) bio-mass energy

b) Nuclear energy g) geothermal energy

c) Hydro energy h) tidal energy

d) Solar energy i) ocean thermal energy

e) Wind energy j) ocean wave energy

Consumption trend of primary energy resources

The average % consumption trend of various primary energy resources of

the world is indicated in the above fig, though the trend differs from country to

country. Looking at figure the heavy dependence on fossil fuels stands out clearly.

About 88% of the world„s energy supply comes mainly from fossil fuels. The share

of fossil fuels is more than 90% in case of India.



Fig:-Percentage consumption of various primary energy resources

Salient features of Non-Conventional Energy Resources

Merits:

1. NCES are available in nature, free of cost.

2. They cause very little pollution. Thus, by and large, they are environmental

friendly.

3. They are inexhaustible.

4. They have low gestation period.

Demerits:

1) Though available freely in nature, the cost of harnessing energy

from NCES is high, as in general, these are available in dilute forms

of energy.

2) Uncertainty of availability: the energy flow depends on various

natural phenomena beyond human control.

3) Difficulty in transporting this form of energy.



Advantages & Disadvantages of Conventional Energy Resources:

ADVANTAGES:

1) Coal: as present is cheap.

2) Security: by storing certain quantity, the energy availability can be ensured for a

certain period.

3) Convenience: it is very convenient to use.

DISADVANTAGES:

1) Fossil fuels generate pollutants: CO, CO2, NOX, SOX. Particulate matter & heat.

The pollutants degrade the environment, pose health hazards & cause various other

problems.

2) Coal: it is also valuable petro-chemical & used as source of raw material for

chemical, pharmaceuticals & paints, industries, etc. From long term point of view,

it is desirable to conserve coal for future needs.

3) Safety of nuclear plants: it is a controversial subject.

4) Hydro electrical plants are cleanest but large hydro reservoirs cause the

following problems

a) As large land area submerges into water, which leads to deforestation

b) Causes ecological disturbances such as earthquakes

c) Causes dislocation of large population & consequently their rehabilitation

problems.

ENERGY ALTERNATIVES:

i) WATER POWER (HYDRO POWER)

Water power is developed by allowing water to fall under the force of

gravity. It is used almost exclusively for electric power generation, in fact, the

generation of water power on a large scale became possible around the beginning

of the twentieth century only with the development of electrical power plants or

Hydro electric plants were usually of small capacities usually less than 100 KW.

Potential energy of water is converted into Mechanical energy by using

prime moves known as hydraulic turbines. Water power is quite cheap where water

is available in abundance. Although capital cost of hydroelectric power plants is

higher as compared to other types of power plants but their operating Costs are



quite low, as no fuel is required in this case. The development rate of hydropower

is still low, due to the following problems:

In developing a project, it will take about 6-10 years‟ time for planning,

investigation and construction.

High capital investment is needed, and some parts of the investment have to

be designed from foreign sources.

There are growing problems on relocation of villages, involved,

compensation for damage, selecting the suitable resettlement area and

environmental impact.

Because of long transmission line to the villages with low load factor, the electric

power will be available to the people in rural areas may not be economical. This

leads to the development of Mini or Micro hydroelectric projects to supply the

electric power to remote areas. The Importance of Micro hydroelectric projects

have been observed

Advantages of water power

1) Water source is available in pleanty.no fuel is required to be burnt to generate

electricity. The downstream water from turbine can be used for irrigation and other

purposes.

2) Running costs of HEP is less than the thermal and nuclear power plants. No cost

of fuel and transportation cost of fuel is also nil.

3) No problem with regards to the disposal of ash in case of thermal power plants.

The problem of emission of polluting gases doesn‟t exist. Hydropower doesn‟t

produce in greenhouse effect, acid rain etc.

4) The plant can be run up and synchronized in few minutes. But in thermal or

nuclear power plants it takes about two days to start up and shut down the plant.

5) Plant is highly reliable and its maintainence and operation charges are very low.

6) Hydroelectric power plant has great life and can easily last 50 years or more.

The efficiency of plant doesn‟t change with age.

7) Load can be varied quickly and rapidly changing load demands can be met

without any difficulty.



Disadvantages of water power ;

1) The capital cost of plant is very high.

2) The gestation period of hydro projects is quite large. The gap between

foundation and completion of project may extend from 10-15years

3) Power generation is dependent on the quantity of water available, which may

vary from season to season and year to year.

4) Plants are often far away from the load canter and requires long transmission

lines to deliver power. Thus the cost of transmission increases.

5) Large hydroelectric power plants disturb the ecology of the area, by way of

deforestation, destroying vegetarian and uprooting people.

ii) NUCLEAR POWER:

According to modern theories of atomic structure, matter consists of

minute particles known as atoms. Heavier unstable atoms such as U235, Th239,

liberate large amount of heat energy. The energy released by the complete fission

of one Kg of Uranium (U235), is equal to the heat energy obtained by burning

4500 tonnes of coal (or) 220 tons of oil. The heat produced by nuclear fission of

the atoms of fissionable material is utilized in special heat exchangers for the

production of steam which is then used to drive turbo generators as in the

conventional power plants. However there are some limitations in the use of

nuclear energy namely high capital cost of nuclear power plants, limited

availability of raw materials, difficulties associated with disposal of radio active

waste and shortage of well trained personnel to handle the nuclear power plants.

The Uranium reserves in the world at present are small. These reserves are

recoverable but are expensive.

The presently working power plants are:

1. Tarapur atomic power station in Maharashtra

2. Ranapratap sagar atomic power station near Tota, Rajasthan

3. Kalpakkam atomic power station near Madras, Tamilnadu.

4. Narora atomic power station in U.P.



Nuclear reactions are of two types

1. Nuclear fission (splitting of heavy nucleus)

2. Nuclear fusion (The joining of lighter nuclei)

Fission: Fission may be defined as the process of splitting an atomic nucleus into

fission fragments. The fission fragments are generally in the form of smaller

atomic nuclei and neutrons. Large amounts of energy are produced by the fission

process.

Fusion: Fusion is a nuclear reaction whereby two light atomic nuclei fuse or

combine to form a single larger, heavier nucleus. The fusion process generates

tremendous amounts of energy. For fusion to occur, a large amount of energy is

needed to overcome the electrical charges of the nuclei and fuse them together.

Fusion reactions do not occur naturally on our planet but are the principal type of

reaction found in stars. The large masses, densities, and high temperatures of stars

provide the initial energies needed to fuel fusion reactions. The sun fuses hydrogen

atoms to produce helium, subatomic particles, and vast amounts of energy.

Advantages of Nuclear power

1. Nuclear power plant is more economical compared with thermal in areas where

coal field is far away.

2. There is no problem of fuel transportation, storage and handling and ash

handling as in thermal power plants.

3. Man power required for the operation of nuclear power plant is less. Therefore

the cost of operation is reduced.

4. Nuclear plant occupies less space than thermal power plants, which reduces the

cost of civil construction.

5. The capital cost in structural materials, piping and storage are less than thermal

plants of the same capacity.

Disdvantages of Nuclear power

1. Danger of nuclear radiation.

2. Problem of disposing the radioactive waste materials.

3. It has to be operated at full load throughout for a good efficiency. So part load



operation becomes inefficient.

4. Capital cost of small size plants is very high.

iii) TAR SANDS:

Fig. Production of synthetic crude oil from tar sands

Fig: Tar Sand

Tar sand or oil sands is an expression used to describe porous sandstone deposits

impregnated with heavy viscous oils called bitumen or simply deposits of heavy

oils.

The above schematic diagram indicating the processes involved in producing

synthetic crude oil from tar sands made up of sand stone deposits containing

bitumen.

The sands obtained from surface mining are first passed through a conditioning

drum where water, steam & caustic soda are added & slurry is formed. The

slurry passes into a separation tank where the coarse sand settles at the bottom

& a froth of bitumen, water & fine mineral matter forms on the top.

The froth is diluted with naptha & subjected to centrifugal action. As a result,

fine mineral matter & water is removed. After this, the naptha is recovered &



recycled, & the bitumen obtained is subjected to hydro processing &

desulphurization to produce synthetic crude oil.

iv) Oil shale

Fig. Oil shale Fig. Production of crude oil from oil shale

Oil shale [a sedimentary rock] refers to a finely textured rock mixed with a

solid organic material called kerogen. When crushed, it can be burnt directly [like

coal] & has a heating value ranging from 2000 to 17,000 KJ/Kg. It is used in this

manner for generating electricity & supplying heat. Alternatively, the oil shale can

be converted to oil. This is done by heating crushed oil shale to about 500 ˚C in the

absence of air. Under the conditions, pyrolysis occurs & the kerogen is converted to

oil.

Demerits:

The use of oil shale is the environmental degradation associated with surface

mining & with the disposal of large amounts of sand & spent shale rock which

remains after the crude oil is obtained.

A large amount of energy is consumed in producing oil from these sources.



SOLAR ENERGY

Solar Radiation: Extra-Terrestrial radiation, spectral distribution of extra-

terrestrial radiation, solar constant, solar radiation at the earth‟s surface, beam,

diffuse and global radiation, solar radiation data.

Measurement of Solar Radiation: Pyrometer, shading ring pyrheliometer,

sunshine recorder, schematic diagrams and principle of working.

Solar Radiation Geometry: Flux on a plane surface, latitude, declination angle,

surface azimuth angle, hour angle, zenith angle and solar altitude angle, expression

for the angle between the incident beam and the normal to a plane surface (No

derivation) local apparent time. Apparent motion of sun, day length, numerical

examples.

Introduction

Energy from the sun is called solar energy. The Sun‟s energy comes from

nuclear fusion reaction that takes place deep in the sun. Hydrogen nucleus fuses

into helium nucleus. The energy from these reactions flow out from the sun and

escape into space. Solar energy is sometimes called radiant energy. These are

different kinds of radiant energy emitted by sun. The most important are light

infrared rays. Ultra violet rays, and X- Rays.

All life on the earth depends on solar energy. Green plants make food by

means of photosynthesis. Light is essential for this process to take place. This light

usually comes from sun. Animal get their food from plants or by eating other

animals that feed on plants. Plants and animals also need some heat to stay alive.

Thus plants are store houses of solar energy. The solar energy that falls on India in

one minute is enough to supply the energy needs of our country for one day. Man

has made very little use of this enormous amount of solar energy that reaches the

earth.

Solar Constant

The rate at which solar energy arrives at the top of the atmosphere is called

solar constant Isc. This is the amount of energy received in unit time on a unit area

perpendicular to the sun‟s direction at the mean distance of the earth from the sun.

The value of Solar constant is taken as 1367 W/m2.



The distance between the earth and the sun varies a little through the year.

Because of this variation, the extra – terrestrial flux also varies. The earth is closest

to the sun in the summer and farthest away in the winter. This variation in the

Intensity of solar radiation (I) can be approximated by the equation.

.

Where n is the day of the year.

Extraterrestrial radiation

Solar radiation incident outside the earth's atmosphere is called

extraterrestrial radiation. On average the extraterrestrial irradiance is 1367

Watts/meter2 (W/m2).

This value varies by ±3% as the earth orbits the sun. The earth's closest

approach to the sun occurs around January 4th and it is furthest from the sun

around July 5th.

Solar Radiation at the Earth’s Surface

The solar radiation that penetrates the earth‟s atmosphere and reaches the

surface differs in both amount and character from the radiation at the top of the

atmosphere.

http://wikieducator.org/File:Solar_Geometry.jpeg



Solar radiation received at the earth‟s surface is in the attenuated form

because it is subjected to the mechanisms of absorption and scattering as it passes

through the earth‟s atmosphere. Absorption occurs primarily because of the

presence of ozone and water vapour in the atmosphere and lesser extent due to

other gases( like CO2, NO2, CO,O2 and CH4) and particulate matter. It results in an

increase in the internal energy of the atmosphere. On the other hand, scattering

occurs due to all gaseous molecules as well as particulate matter in the atmosphere.

The scattered radiation is redistributed in all directions, some going back to the

space and some reaching the earth‟s surface.

Solar radiation received at the earth‟s surface without change of direction i.e, in

line with the sun is called direct radiation or beam radiation.

The radiation received at the earth‟s surface from all parts of sky‟s hemisphere

(after being subjected to scattering in the atmosphere) is called diffuse

radiation.

The sum of beam radiation and diffuse radiation is called as total or global

radiation.

Fig:- Direct, diffuse and total radiation



Fig:-Position of extraterrestrial and terrestrial regions

SPECTRAL DISTRIBUTION OF SOLAR RADIATION

The sun radiates energy in all the wave lengths (0 to ∞). Solar radiation

spectrum is close to that of a black body with a temperature of around 5800 K.

About half of that lies in the visible short wave part and other half mostly near

the infrared part; some also lies in the UV part of the spectrum.

Spectrum of electromagnetic radiation striking Earth‟s atmosphere (100 to 106

nm) is divided in to five regions.

Ultraviolet C : 100 to 280 nm:- Invisible to human eye, mostly absorbed by

lithosphere.

Ultraviolet B : 280 to 315 nm:- Mostly absorbed by atmosphere, responsible for

photochemical reaction leading to ozone layer.

Ultraviolet A : 315 to 400 nm:- Considered less damaging to DNA.

Visible range:- 400 to 700 nm

Visible range:- 700 to 106 nm:- An important part of the electromagnetic

radiation reaching earth. It is divided in to three parts

Infrared A : 700 to 1400 nm

Infrared B : 1400 to 3000 nm

Infrared C : 3000 to 1 Mm

Maximum value of Solar radiation Intensity = 2074 W/m2 occurs at 0.48 µm

wavelength.

99% of solar radiation is obtained up to a wavelength of 4 µm.



SOLAR RADIATION DATA

Solar radiation data are available in several forms and should include the

following information‟s:-



Whether they are instantaneous measurement or values integrated over some

period of time (Usually hour or day).

The time or time period of measurements.

Whether the measurements are of direct, diffuse and total radiation, and the

instrument used.

Receiving surface orientation.

If averaged, the period over which they are averaged (e.g., monthly average of

daily radiation).

Most of the data on solar radiation received on the surface of the earth rare

measured by solarimeter which give readings for instantaneous measurements at

rate throughout the day for total radiation on a horizontal surface. Integrating the

plot of rate of energy received per unit area per unit time over a whole day gives

the langleys of radiation received on a horizontal surface. (Solar radiation flux is

reported in langleys per hour per day, 1 langley = 1cal/cm2).

MEASUREMENT OF SOLAR RADIATION

Two basic types of instruments are used in measurements of solar radiation. These

are:

i) Pyranometer: An instrument used to measure global (direct and diffuse) solar

radiation on a surface. This instrument can also be used to measure the diffuse

radiation by blocking out the direct radiation with a shadow band.

ii) Pyrheliometer: This instrument is used to measure only the direct solar

radiation on a surface normal to the incident beam. It is generally used with a

tracking mount to keep it aligned with the sun.

i) Pyranometer:

A pyranometer is an instrument which measure‟s either global or diffuse

radiation falling on a horizontal surface over a hemispherical field of view. A

sketch of one type of pyranometer as installed for measuring global radiation is

shown in the following figure.

Pyranometer consists of a black surface which heats up when exposed to

solar radiation. Its temperature increases until the rate of heat gain by solar

radiation equals the rate of heat loss by convection, conduction and radiation. The

hot junctions of thermopile are attached to the black surface, while the cold

junctions are located under a guard plate so that they do not receive the radiation



directly. As a result an emf is generated. This emf which is usually in the range of

0 t0 10mv can be read, recorded

,

Fig: - Pyranometer

Pyranometer can also be used for measurement of diffuse radiation. This is

done by mounting it at the center of a semicircular shading ring. The shading ring

is fixed in such a way that its plane is parallel to the plane of path of sun‟s daily

movement across the sky and it shades the thermopile element and two glass

domes of pyranometer at all the times from direct sun shine. Consequently the

pyranometer measures only the diffuse radiation received from the sky.

ii) Pyrheliometer

This is an instrument which measures beam radiation falling on a surface

normal to the sun‟s rays. In contrast to a pyranometer, the black absorber plate

(with hot junctions of a thermopile attached to it) is located at the base of a

collimating tube. The tube is aligned with the direction of the sun‟s rays with the

help of a two-axis tracking mechanism and alignment indicator. Thus the black

plate receives only beam radiation and a small amount of diffuse radiation falling

within the acceptance angle of the instrument.

1. Black Surface

2. Glass domes

3. Guard plate

4. Leveling screws

5. Mounting plate

6. Grouted bolts.

7. Platform



Fig:- Pyrheliometer

Sun Shine Recorder

The duration of bright sun shine in a day is measured by means of a sunshine

recorder. The sun‟s Rays are focused by a glass sphere to a point on a card strip

held in a groove in a spherical bowl mounted concentrically with the sphere.

Whenever there is bright sunshine, the image formed is intense enough to burn a

spot on the cord strip. Thoughout the day as the sun moves across the sky, the

1. Tube blackened on inside

surface

2. Baffle,

3. Alignment indicator

4. Black absorber plate

5. Thermopile junctions

6. Two-axis tracking mechanism



image moves along the strip. Thus, a burnt trace whose length is proportional to

the duration of sunshine is obtained on the strip.

SOLAR RADIATION GEOMETRY

1) Equator, latitude, Longitude, Meridian

The latitude of a point on the earth's surface is the angle between the

equatorial plane and a line that passes through that point and is normal to the

surface.

• Latitude angles can range up to +90 degrees (or 90 degrees north), and down

to -90 degrees (or 90 degrees south). Latitudes of +90 and -90 degrees

correspond to the north and south geographic poles on the earth.

• The 0° parallel of latitude is designated the equator, the fundamental plane of

all geographic coordinate systems.

The Longitude λ, of a point on the earth's surface is a geographic

coordinate that specifies the east-west position the angle east or west from a

reference meridian to another meridian that passes through that point.

• By convention the Prime Meridian, which passes through the Royal

Observatory, Greenwich, England, was allocated the position of zero degrees

https://en.wikipedia.org/wiki/Geographic_coordinate_system

https://en.wikipedia.org/wiki/Geographic_coordinate_system

https://en.wikipedia.org/wiki/Prime_Meridian

https://en.wikipedia.org/wiki/Royal_Observatory,_Greenwich

https://en.wikipedia.org/wiki/Royal_Observatory,_Greenwich



longitude. The longitude of other places is measured as the angle east or west

from the Prime Meridian, ranging from 0° at the Prime Meridian to +180°

eastward and −180° westward.

• Latitude and longitude specify the position of any location on the planet, but

do not account for altitude or depth.

Greenwich meridian, imaginary line used to indicate 0° longitude that

passes through Greenwich, a borough of London, and terminates at the North and

South poles.

Equator is a line notionally drawn on the earth equidistant from the poles,

dividing the earth into northern and southern hemispheres and constituting the

parallel of latitude 0°.

2) Solar Incident angle (θ):

It is the angle between an incident beam radiation (I) falling on the earth and

normal to the plane surface.

The equivalent flux or radiation intensity falling normal to the surface is

given by I cos θ.

3) Altitude (φl) of a point or location is the angle made by the radial ine joining

the location to the centre of the earth with the projection of the line on the

equatorial plane. (In the figure it is the angle between OP and the projection of OP

on the equatorial plane)

Fig:- Latitude, hour angle, decilnation

4) Declination (δ):

https://www.britannica.com/science/longitude

https://www.britannica.com/place/Greenwich-borough-London

https://www.britannica.com/place/London



It is the angle between a line extending from the centre of the Sun and center

of the earth and projection of this on earth„s equatorial plane.

Declination is the direct consequence of earth„s tilt and It would vary between

23.5o on June 22 to – 23.5

o on December 22. On equinoxes of March21 &

Sept22 declination is zero.

The declination is given by the formula.

δ = 23.45 Sin [

(284 + n) ]

Where n is the day of the year.

Fig:- Variation of suns decination

5) Hour angle (ω):

Hour angle is the angle through which the earth must turn to bring meridian

of the point directly in line with the sun„s rays. Hour angle is equal to 15o per hour.

(It is the angle measured in the earth‟s equatorial plane, between the projection OP

and the projection of a line from the centre of the sun to the centre of the earth)

6) Solar altitude angle (α):

Altitude Angle is the angle between the Sun„s rays and projection of the

Sun‟s rays on the horizontal plane.

7) Zenith angle (θz):



It is Complementary angle of Sun„s Altitude angle. It is a vertical angle

between Sun„s rays and line perpendicular to the horizontal plane through the point

i.e. angle between the beam and the vertical

θz=π/2-α

8) Solar Azimuth Angle (γs):

It is the solar angle in degrees along the horizon east or west of north

or

It is the horizontal angle measured from north to the horizontal projection of

sun„s rays.

9) Slope (β):

It is the angle made by the plane surface with the horizontal.

Fig:- Suns zenith, altitude and azimuth angles

10) Surface azimuth angle (γ):

Angle between the normal to the collector and south direction is called

surface azimuth angle (γ)



Fig:- Surface azimuth angle and slope defined

11) Relation between θ and other angles Cosθ = Sin φl (sinδ cosβ+Cosδ cosγ cos ω sin β)+

Cos φl (Cosδ cosω cos β - sinδ cosγ sin β)+

Cosδ sinγ sinω sin β ----- Eqn(1)

Where

φl =Latitude( north positive)

δ= Declination (north positive)

ω= Solar hour angle (Positive between midnight and solar noon)

Case1:- Vertical Surface: (β=900)

Eqn (1) becomes

Cosθ = Sin ф cosδ cosγ cos ω - Cos ф sinδ cosγ+ Cosδ sinγ Sinω ----Eqn(2)

Case2:- Horizantal surfaces (β=00)

Eqn(1) becomes

Cosθ=Sin ф sinδ + cosδ cos ф cosω = sinα = cos θz ---- Eqn(3)

Case3:- Surface facing south (γ =0)

cos θT =Sin ф (sinδ cosβ+ Cosδ cosω sinβ)

=Cos ф(cosδ cosω cosβ-s inδ sinβ) ---- Eqn(4)

(Incident angle θ is represented as θT, denoting the surface is tilted)



Case4:- Vertical surfaces facing south (β=900 , γ=0)

cos θz=Sin ф cosδ cos ω- Cos ф Sinδ ---- Eqn(5)

12) Day Length:

At the time of sunset or sunrise the zenith angle θz=900 , we obtain sunrise

hour angle as

cos ωs = -

= - tanф tan

ωs = cos-1

(- tanф tan

Since 150 of the hour angle are equivalent to 1 hour, the day length(hrs) is given by

td =

=

cos

-1 (- tanф tan

13) Local Solar Time (Local Apparent Time (LAT) :

Local Solar Time can be calculated from standard time by applying two

corrections. The first correction arises due to the difference in longitude of the

location and meridian on which standard time is based. The correction has a

magnitude of 4minutes for every degree difference in longitude. Second correction

called the equation of time correction is due to the fact that earth„s orbit and the

rate of rotation are subject to small perturbations. This is based on the experimental

observations. Thus,

Local Solar Time= Standard time± 4(Standard time Longitude-Longitude of

the location) +(Equation of time correction)

Example 1:

Determine the local solar time and declination at a location latitude 23015‟ N,

longitude 77030‟E at 12.30 IST on June 19. Equation of Time correction is =

-(1‟01‟‟).

Solution:

The Local solar time=IST- 4(standard time longitude-longitude of location)+

Equation of time correction.



=12 h 30‟- 4 (82

0 30‟-77

0 30‟)-1‟01‟‟

=12h 8‟ 59‟‟

Declination δ can be calculated Cooper„s Equation i.e,

δ = 23.45 Sin [

(284 + n) ]

δ = 23.45 Sin [

(284 + 170) ]

= 23.45 sin 860=23.43

0

Example 2: Calculate an angle made by beam radiation with normal to a flat plate

collector on December 1 at 9.00 A.M, Solar time for a location at 28035‟ N. The

collector is tilted at an angle of latitude plus 100, with the horizontal and is pointing

due south.

Solution:

Here γ=0 since collector is pointing due south. For this case we have equation.

cos 𝜃𝑇= Sinδ Sin(ф-β) +Cosδ cosω Cos(ф-β)

Declination δ can be calculated Cooper„s Equation on December 1st i.e, n=335

δ = 23.45 Sin [

(284 + n) ]

δ = 23.45 Sin [

(284 + 335) ]

= −22011‟‟

Hour angle ω corresponding to 9.00h r=450

Hence,

cos 𝜃𝑇 = cos (28.580 − 38.58

0) cos (−22.11

0) cos 45

0 +

sin (−22.110) sin (28.580 − 38.58

0)

=0.7104

𝜃𝑇 = 44.720



ENERGY FROM BIO MASS

SYLLABUS : Photosynthesis, photosynthetic oxygen production, energy

plantation, bio gas production from organic wastes by anaerobic fermentation,

description of bio-gas plants, transportation of bio-gas, problems involved with

bio-gas production, application of bio-gas, application of bio-gas in engines,

advantages.

INTRODUCTION

Bio gas is generated through a process of anaerobic digestion of Bio Mass.

Bio Mass is organic matter produced by plants, both terrestrial (those grown on

land) and aquatic (those grown in water) and their derivatives. It includes forest

crops and residues, crops grown especially for their energy content on “energy

farms” and animal manure. Unlike coal, oil and natural gas, which takes Millions

of years to form, bio mass can be considered as a renewable energy source because

plant life renews and adds to itself energy year. It can also be considered a form of

solar energy as the latter is used indirectly to grow these plants by photosynthesis.

Bio Mass means organic matter and Photo Chemical approach to harness

solar energy means harnessing of solar energy by photo synthesis. Solar energy is

stored in the form of chemical energy. Hence solar energy –> Photosynthesis –>

Bio Mass->energy generation.

PHOTOSYNTHESIS

Photosynthesis is the process by which plants, some bacteria, and some

protistans use the energy from sunlight to produce sugar, which cellular respiration

converts into ATP (Adenosine triphosphate), the "fuel" used by all living things.

The conversion of unusable sunlight energy into usable chemical energy is

associated with the actions of the green pigment chlorophyll. Most of the time, the

photosynthetic process use water and releases the oxygen that we absolutely must

have to stay alive.

We can write the overall reaction of this process as:

6H2O + 6CO2 ----------> C6H12O6+ 6O2

Six molecules of water plus six molecules of carbon dioxide produce one

molecule of sugar plus six molecules of oxygen.



Photosynthetic Oxygen production

Photosynthesis is a two stage process. The first process is the Light

Dependent Process (Light Reactions), requires the direct energy of light to make

energy carrier molecules that are used in the second process. The Light

Independent Process (or Dark Reactions) occurs when the products of the Light

Reaction are used to form C-C covalent bonds of carbohydrates. The Dark

Reactions can usually occur in the dark, if the energy carriers from the light

process are present. The Light Reactions occur in the grana and the Dark Reactions

take place in the stroma of the chloroplasts.

Reactions

In the Light Dependent Processes (Light Reactions) light strikes chlorophyll

a in such a way as to excite electrons to a higher energy state. In a series of

reactions the energy is converted (along an electron transport process) into ATP

(Adenosine triphosphate) and NADPH (Nicotinamide adenine dinucleotide

phosphate). Water is split in the process, releasing oxygen as a by-product of the

reaction. The ATP and NADPH are used to make C-C bonds in the Light

Independent Process (Dark Reactions).

ENERGY PLANTATION

Energy plantation means growing select species of trees and shrubs which

are harvestable in a comparably shorter time and are specifically meant for fuel.



The fuel wood may be used either directly in wood burning stoves and boilers or

processed into methanol, ethanol and producer gas.

Energy plantation is the practice of planting trees, purely for their use as

fuel. Terrestrial biomass i.e., the wood plants has been used since long time to

generate fire for cooking and other purposes. In recent years, to meet the demand

of energy, plantation of energy plants has been re-emphasized.

Advantages of energy plantations

1. Byproducts of energy plantations can be used for livestock such as cattle or

sheep, and honey bee farm that utilizes the flowers of energy crops.

2. Energy plantations absorb CO2 from the atmosphere (Carbon negative), hence

application of wood pellets is carbon neutral activity.

3. Uncultivated land or marginal land that the millions of hectares can be utilized

effectively.

4. Fertilize and improve soil conditions, including the prevention of erosion.

BIOMASS

It is the organic matter consisting of plant animal matter. Any matter which

is biodegradable is known as biomass or organic matter. Generation of energy from

biomass is referred to as Photo chemical harnessing of solar radiation since to

generate biomass; solar radiation is a must.

Energy from the biomass is generated in three different forms namely

i) Direct burning, ii) Liquefaction, iii) Gas generation.

Direct burning: When biomass is directly burnt, energy is generated as given by

the following expression,

CO2 +O2

CH2O+O2

Thus when photosynthesis reaction is reversed energy is liberated.

Liquefaction: Biomass is liquefied either by thermo-chemical method or

biochemical method to generate alcohols like methyl and ethyl alcohol. These are

mixed with petrol and used in IC Engines as fuels.

Bio gas: Biomass is converted to biogas by the process of digestion or

fermentation in the presence of micro-organisms. This biogas mainly contains

methane which is a good combustible gas. Biogas consists of 50-55% of methane,

http://biomassproject.blogspot.co.id/2014/01/carbon-positive-carbon-carbon-neutral.html



30-35% of CO2 and remaining waste gases like H2, N2, H2S etc. since it contains a

hydrocarbon gas it is a very good fuel and hence can be used in IC engines. It is a

slow burning gas with calorific value of 5000-5500 Kcal/kg. the raw material used

to generate this are algae, crop residue, garbage, kitchen waste, paper waste, waste

from sugar cane refinery, water hyacinth etc. apart from the above mentioned raw

materials excreta of cattle, piggery waste and poultry droppings are also used as

raw materials. Biogas is generated by fermentation or digestion of organic matter

in the presence of aerobic and anaerobic micro-organisms. Fermentation is the

process of breaking down the complex organic structure of the biomass to simple

structures by the action of micro-organisms either in the presence of O2 or in the

absence of O2. The container in which the digestion takes place is known as the

digester.

The digestion takes place in the following steps:-

i) Enzymatic hydrolysis ii) Acid formation iii) Methane formation.

i) Enzymatic hydrolysis: In this step the complex organic matter like

starch,protein, fat, carbohydrates etc are broken down to simple structures using

anaerobic micro-organisms.

ii) Acid formation: In this step the simple structures formed in the enzymatic

hydrolysis step are further reacted by anaerobic and facultative microorganisms

(which thrive in both the presence and absence of oxygen) to generate acids.

iii) Methane formation: In this step the organic acids formed are further

converted to methane and CO2 by anaerobic micro-organisms (anaerobes).

BIOGAS PRODUCTION BY ANAEROBIC FERMENTATION:

There are four key biological and chemical stages of anaerobic digestion:

i) Hydrolysis ii) Acidogenesis iii) Acetogenesis iv) Methanogenesis.

i) Hydrolysis

In most cases biomass is made up of large organic compounds. In order for

the microorganisms in anaerobic digesters to access the chemical energy potential

of the organic material, the organic matter macromolecular chains must first be

broken down in to their smaller constituent parts. These constituent parts or



monomers such as sugars are readily available to microorganisms for further

processing. The process of breaking these chains and dissolving the smaller

molecules in to solution is called hydrolysis.

Fig:-Anaerobic pathway of complex organic matter degradation

ii) Acido genesis

Acetates and hydrogen produced in the first stages can be used directly by

methanogens. Other molecules such as volatile fatty acids (VFA„s) with a chain

length that is greater than acetate must first be catabolized into compounds that can

be directly utilized by methanogens. The biological process of acidogenesis is

where there is further break down of the remaining components by acidogenic

(fermentative) bacteria. Here VFA„s are generated along with ammonia, carbon

dioxide and hydrogen sulphide as well as other by-products.



iii) Acetogenesis

The third stage anaerobic digestion is acetogenesis. Here simple molecules

created through the acidogenesis phase are further digested by acetogens to

produce largely acetic acid as well as carbon dioxide and hydrogen.

iv) Methanogenesis

The final stage of anaerobic digestion is the biological process of

Methanogenesis. Here methanogenic archaea utilize the intermediate products of

the preceding stages and convert them in to methane, carbon dioxide and water. It

is these components that makes up the majority of the biogas released from the

system.

CLASSIFICATION OF BIOGAS PLANTS:

A) CONTINOUS AND BATCH TYPE

i) Single stage continuous plant:

The entire process of conversion of complex organic compounds into biogas

in completed in a single chamber. This chamber is regularly fed with the raw

materials while the spent residue keeps moving out. The input slurry for this type

of plant is either self-buffered (which can get digested easily) or the biogas mixed

BIOGAS PLANTS

CONTINOUS AND BATCH TYPE

SINGLE STAGE

DOUBLE STAGE

DOME AND DRUM TYPE

Floating gas holder or

KVIC model

Fixed dome type or Chainese model or

Janatha model



with sufficient amount of digesting material. Serious problems are encountered

with agricultural residues when fermented in a single stage continuous process.

Fig:- Single stage continuous plant

ii) Double stage continuous plant:

Fig:- Double stage continuous plant



The acidogenic stage and methanogenic stage are physically separated into

two chambers. Thus the first stage of acid production is carried out in a separate

chamber and only the diluted acids are fed into the second chamber where bio-

methanation takes place and the biogas can be collected from the second chamber.

Considering the problems encountered in fermenting fibrous plant waste materials

the two stage process may offer higher potential of success.

The main features of continuous plant are that:

It will produce gas continuously.

It requires small digestion chambers.

It needs lesser period for digestion.

It has fewer problems compared to batch type and it is easier in operation.

B) DOME AND DRUM TYPE:

i) Indian Digester (Floating drum type/Khadi Villege Industries Commission

Plant (KVIC)):

Fig:- Indian Digester ( KVIC)

This mainly consists of a digester or pit for fermentation and a floating drum

for the collection of gas. Digester is 3.5-6.5 m in depth and 1.2 to 1.6 m in

diameter. There is a partition wall in the center, which divides the digester

vertically and submerges in the slurry when it is full. The digester is connected to



the inlet and outlet by two pipes. Through the inlet, the dung is mixed with water

(4:5) and loaded into the digester. The fermented material will flow out through

outlet pipe. The outlet is generally connected to a compost pit. The gas generation

takes place slowly and in two stages. In the first stage, the complex, organic

substances contained in the waste are acted upon by a certain kind of bacteria,

called acid formers and broken up into small-chain simple acids. In the second

stage, these acids are acted upon by another kind of bacteria, called methane

formers and produce methane and carbon dioxide.

Gas holder:

The gas holder is a drum constructed of mild steel sheets. This is cylindrical

in shape with concave top. The top is supported radially with angular iron stripes.

The holder fits into the digester like a stopper. It sinks into the slurry due to its own

weight and rests upon the ring constructed for this purpose. When gas is generated

the holder rises and floats freely on the surface of slurry. A central guide pipe is

provided to prevent the holder from tilting. The holder also acts as a seal for the

gas. The gas pressure varies between 7 and 9 cm of water column. Under shallow

water table conditions, the adopted diameter of digester is more and depth is

reduced. The cost of drum is about 40% of total cost of plant. It requires periodical

maintenance. The unit cost of KVIC model with a capacity of 2 m3/day costs

approximately Rs.14,000/-.

ii) Janata type biogas plant (Chinese):

The design of this plant is of Chinese origin but it has been introduced under

the name ―Janata biogas plant by Gobar Gas Research Station, Ajitmal in view of

its reduced cost. This is a plant where no steel is used, there is no moving part in it

and maintenance cost is low. The plant can be constructed by village mason taking

some pre-explained precautions and using all the indigenously available building

materials. Good quality of bricks and cement should be used to avoid the afterward

structural problems like cracking of the dome and leakage of gas. This model have

a higher capacity when compared with KVIC model, hence it can be used as a

community biogas plant. This design has longer life than KVIC models. Substrates

other than cattle dung such as municipal waste and plant residues can also be used

in janata type plants. The plant consists of an underground well sort of digester



made of bricks and cement having a dome shaped roof which remains below the

ground level is shown in figure. At almost middle of the digester, there are two

rectangular openings facing each other and coming up to a little above the ground

level, act as an inlet and outlet of the plant. Dome shaped roof is fitted with a pipe

at its top which is the gas outlet of the plant. The principle of gas production is

same as that of KVIC model. The biogas is collected in the restricted space of the

fixed dome; hence the pressure of gas is much higher, which is around 90 cm of

water column.

Fig:- Chinese design biogas plant

FACTORS AFFECTING BIOGAS GENERATION:

1) PH value 2) Temperature 3) Total solid content 4) Load rating 5) Seeding

6) Uniform feeding 7) Dia to depth ratio 8) Carbon to nitrogen ratio 9) Nutrient

10) Mixing 11) Retention time 12) Type of feedstock 13) Toxicity 14) Pressure

1) PH value: It is an index of hydrogen ion concentration in the mixture which

also predicts acidity or alkalinity of the mixture. For effective gas generation the

required PH value is 6.5 to 7.6. If this value decreases to 4-6, the mixture becomes

acidic and if the value becomes 9-10 then it becomes alkaline. Both for acidic and

alkaline conditions the methane forming bacteria becomes inactive and the gas

generation is reduced. Thus for effective gas generation the required PH value is

6.5-7.5.



2) Temperature: The effect of temp on gas generation is as shown in graph. The

two curves represent two types of bacteria which are sensitive to two different

temp levels. Mesophilic type of bacteria will effectively generate gas at a temp of

about 35º C. Thermophilic type of bacteria will generate gas effectively at a temp

of about 55º C. As the temperature decreases or increases from the above values

the period of gas generation will be increased. Since it is easy to maintain a temp

of 35º C, it is advisable to select mesophilic type of bacteria for digestion.

3) Total solid content: The raw material added to the digester contains both solid

and liquid in the ratio of 20:80 by weight. From the experience it is found that the

gas generation is improved by maintaining the solid content of the mixture at about

8 to 10% by weight. This is done by adding water to the mixture.

4) Loading rate: It is the addition of the raw material to the digester/day/unit

volume. The effective load rating is found to be 0.5 to 1.6 kg of solid

material/day/m3.

5) Seeding: During digestion the methane forming bacteria are consumed rapidly

and their number will decrease affecting the gas generation. In order to maintain

the quantity of methane forming bacteria, digested slurry from the previous batch

is added to the digester. The digested slurry is rich in methane forming bacteria and

the process is known as seeding.

6) Uniform feeding: this is one of the prerequisites of good digestion. The digester

must be fed at the same time every day with a balanced feed of the same quality

and quantity.

7) Dia to depth ratio: from the experiments it is seen that the gas generation is

improved by maintaining a dia to depth ratio of 0.66 to 1. This provides uniform

temp distribution throughout the digester resulting in increased gas generation.

8) Carbon to nitrogen ratio: The bacteria in the digester utilize carbon for energy

generation (as food) while nitrogen is used for cell building. Hence a carbon to

nitrogen ratio of 30:1 is maintained for effective gas generation. If the ratio is not

maintained, the availability of carbon and nitrogen will vary resulting in reduced

gas generation.



9) Nutrients: The nutrients required by the bacteria for food digestion are

hydrogen, nitrogen, oxygen, carbon, phosphorous and sulphur. of these nitrogen

and phosphorous have to be provided externally while the others are contained in

the raw material itself. Nitrogen is provided by adding leguminous plants (plants

with seeds enclosed in casings, eg: Maize) which are rich in nitrogen content.

Phosphorous is provided by adding night soil (soil mixed with excreta of animals

and humans) to the digester.

10) Mixing: Since bacteria in the digester have very limited reach to their food it

is necessary that the slurry is properly mixed and the bacteria gettheir food supply.

It is found that the slight mixing improves the digestion and a violent mixing

retards the digestion.

11) Retention time: It is the time period required for the gas generation. It

completely depends on the type of the raw materials used. Eg: Night soil requires

30 days, pig dump and poultry droppings require 20 days while cow dung and

other kitchen waste requires 50 days of retention time.

12) Type of feed stock: The usual feed stock used are cow dung, human excreta,

poultry dropping, pig dump, kitchen waste etc. To obtain an efficient digestion

these feed stocks are in some proportions, Predigested and finally chopping will be

helpful for fibrous type of raw materials.

13) Toxicity: If the digester is left with the digested slurry it results in toxicity

which in turn reduces the gas generation. Hence the digested slurry should be

removed after the gas is generated.

14) Pressure: It is found that the gas generation is increased with the decrease in

the pressure of the digester.

PROBLEMS RELATED TO BIO-GAS PLANTS:

1. Handling of effluent slurry is major problem if the person is not having

sufficient open space or compost pits to get the slurry dry. Use of press filters and

transportation is expensive and out of reach of poor farmers. For a domestic plant

up to 200 litres capacity oil drums can be used to carry this effluent to the fields



but this will require some human/animal labour or consumption of diesel if a

vehicle is used.

2. The gas forming-methanogenic bacteria are very sensitive towards the

temperature compared to those of non-methanogenic. During winter as the

temperature falls, there is decrease in the activity of methanogenic bacteria and

subsequently fall in gas production rate. Many methods have been suggested to

overcome this temperature problem as described earlier, e.g.,

a) Use of solar heated hot water to make a slurry of influent but the temperature of

water should not exceed 600C otherwise the mesophilic bacteria will die.

b) Circulation of hot water obtained either from solar heater or I.C. engine heat

exchanger, through pipes inside the digester.

c) Addition of various nutrients for bacteria.

d) Covering the biogas plant by straw bags during night hours.

3. Due to lack of proper training to the bio-gas plant owners for the operation of

plant, a lot of problems arises. It has been noticed that many persons increase the

loading rate and some also do not try to mix the cattle dung with water, keeping in

mind more gas production. Due to this, the flow of slurry from inlet towards outlet

is very slow or even stops. This may cause accumulation of volatile fatty acids and

drop in pH and then failure of digester. Also it is not possible to stir the digester

content of high solid concentration.

4. Addition of urea-fertilizer in large quantities leads to toxicity of ammonia

nitrogen may cause a decrease in gas production.

5. pH and volatile fatty acids play an important role in anaerobic digestion and

should remain under optimum range otherwise this may cause upsetting of digester

and even its failure. pH can be checked from time to time by the use of cheep and

easily available pH paper but volatile fatty acids can only be determined in a

laboratory having its testing facilities. For controlling pH in optimum range, it

tends to fall below 7.0, lime has been suggested, as it is easily available cheap

material and does not harm the activity of bacteria.

6. Leakage of gas from gas holder especially in case of Janta type biogas plants is a

major and very common problem. When there is quite enough gas in a gas holder,



the leakage should be checked by using water and the points marked and then get

repaired. During repairing there should be no gas inside the gas holder and the stop

cock remains open till repaired points get dry.

ADVATAGES OF BIOGAS

Economical benefits of bio gas utilization

From the national economic point of view the bio gas yields following economic

benefits:

(1) Bio gas technology, which is based on recycling of readily available resources

in rural areas, gives comparatively cheaper and better fuel for cooking lighting and

power generation.

(2) An individual can reduce the consumption of commercial energy sources such

as fire wood, coal, kerosene, etc. by adopting waste recycling technology which

vigorously help in reducing the family fuel budget.

(3) The problem of uncertainly of availability of commercial energy can be

resolved by use of bio gas technology.

(4) The rural population of the country uses fire wood for meeting their cooking

requirements. This reduces the national forest wealth. Our forest area can be

conserved by using bio gas.

(5) The dependency on chemical fertilizer for better-agricultural production has

increased to a great extent after independence in India. Bio gas slurry can be

proved a best organic fertilizer which helps in improving soil fertility and crop

production.

(6) Presently country is facing the problem of foreign exchange and balance of

payment. Bio gas technology reduces the import of chemical fertilizers by using

homemade organic fertilizer and also petro products.

(7) Bio gas technology utilizes effectively, the man power and resources, resulting

in self-sufficiency and self-reliance in the society.

Social Benefits

Bio gas is one of the best options in rural areas, which provides self-

sufficiency in energy and helps in increasing standard of living of rural people.

The social benefits from bio gas utilization are as follows:

(1) Bio gas burns giving shoot less flame and smokeless cooking, as such it

provides cleanliness in the houses.



(2) The cooking on bio gas is faster and also women is not required to waste their

time to collect fuel from forest, as such it reduces the drudgery of women who can

use her free time for other developmental activities.

(3) The bio gas provides lighting in the rural areas, which are far away from

electrical supply lines. Thus it helps the children to use their time in study of

employment.

(4) It helps in generation of employment opportunities to village artisans. This also

stops the Migration of people from rural to urban areas in search of employment.

Environmental and Health Benefits

Bio gas system contributes to maintain clean and healthier environment by

processing human growth. Environmental benefits from bio gas are enormous.

Some of them are as under:

(1) Lungs and eye diseases are very common among village women and children

due to smoky kitchen. Bio gas utilization reduces the disease spread. Thus

reducing health problem rush in hospitals and waste of national wealth.

(2) Sanitation problems in villages through systematic collection and through roper

processing of animal dung and human excreta will be solved.

(3) It helps to prevent deforestation. consequently it controls soil erosion, and

floods.

APPLICATIONS OF BIOGAS

The simplest use is in a boiler to produce hot water or steam.

The most common use is where the biogas fuels an internal combustion engine

in a Combined Heat and Power (CHP) unit to produce electricity and heat. In

Sweden the compressed gas is used as a vehicle fuel and there are a number of

biogas filling stations for cars and buses. The gas can also be upgraded and used

in gas supply networks.

The use of biogas in solid oxide fuel cells is also being researched.

Biogas can be combusted directly to produce heat. In this case, there is no need

to scrub the hydrogen sulphide in the biogas

The most common method for utilization of biogas in developing countries is

for cooking and lighting. Conventional gas burners and gas lamps can easily be

adjusted to biogas by changing the air to gas ratio. Cooking: A biogas plant of



2 cubic meters is sufficient for providing cooking fuel needs of a family of

about five persons. A variety of biogas stoves are available for use.

In a number of industrial applications biogas is used for steam production.

TRANSPORTATION OF BIOGAS

Biogas is a low-grade, low-value fuel and therefore it is not economically

feasible to transport it for any distance. Likewise, biogas cannot be economically

trucked. In contrast, bio methane (Biogas is upgraded to bio methane by removing

the H2S, moisture, and CO2) can be distributed to its ultimate point of consumption

by one of several options, depending on its point of origin:

• Distribution via dedicated bio methane pipelines

• Distribution via the natural gas pipeline

• Over-the-Road Transportation of Compressed bio methane

Distribution via Dedicated bio methane Pipelines:-

If the point of consumption is relatively close to the point of production

(e.g., less than 1 mile), the bio methane would typically be distributed via

dedicated biogas pipelines (buried or aboveground).

Distribution via the Natural Gas Pipeline Network:-

The natural gas pipeline network offers a potentially unlimited storage and

distribution system for bio methane. If the bio methane meets the local gas

pipeline gas quality it can be directly injected into the natural gas pipeline network

and it can be used as a direct substitute for natural gas by any equipment connected

to the natural gas grid, including domestic gas appliances, commercial/industrial

gas equipment, and CNG refueling stations.

Over-the-Road Transportation of Compressed bio methane:- If distribution of bio methane via dedicated pipelines or the natural gas grid

is impractical or prohibitively expensive, over-the-road transportation of

compressed bio methane may be a distribution option.



APPLICATION OF BIO-GAS IN ENGINES:

Biogas in Diesel Engine applications:

Biogas generally has a high self-ignition temperature hence; it cannot be

directly used in a CI engine. So it is useful in dual fuel engines. The dual fuel

engine is a modified diesel engine in which usually a gaseous fuel called the

primary fuel is inducted with air into the engine cylinder. This fuel and air mixture

does not auto ignite due to high octane number. A small amount of diesel, usually

called pilot fuel is injected for promoting combustion. The primary fuel in dual

fuelling system is homogeneously mixed with air that leads to very low level of

smoke. Dual fuel engine can use a wide variety of primary and pilot fuels. The

pilot fuels are generally of high cetane fuel. Biogas can also be used in dual fuel

mode with vegetable oils as pilot fuels in diesel engines. Introduction of biogas

normally leads to deterioration in performance and emission characteristics. The

performance of engine depends on the amount of biogas and the pilot fuel used.

Measures like addition of hydrogen, LPG, removal of CO₂etc. have shown

significant improvements in the performance of biogas dual fuel engines. The

ignition delay of the pilot fuel generally increases with the introduction of biogas

and this will lead to advancing the injection timing. Injectors opening pressure and

rate of injection also are found to play important role in the case of biogas fuelled

engine, where vegetables oil is used as a pilot fuel. The CO₂ percentage in biogas

acts as diluents to slow down the combustion process in Homogenous charged

compression ignition (HCCI) engines. However, it also affects ignition. Thus a fuel

with low self-ignition temperature could be used along with biogas to help its

ignition. This kind of engine has shown a superior performance as compared to a

dual fuel mode of operation.

Biogas in Dual Fuel Engine applications:

In this case, the normal diesel fuel injection system still supplies a certain

amount of diesel fuel. The engine however sucks and compresses a mixture of air

and biogas fuel which has been prepared in external mixing device. The mixture is

then ignited by and together with the diesel fuel sprayed in. The amount of diesel

fuel needed for sufficient ignition is between 10% and 20% of the amount needed

for operation on diesel fuel alone. Operation of the engine at partial load requires



reduction of the biogas supply by means of a gas control valve. A simultaneous

reduction of airflow would reduce power and efficiency because of reduction of

compression pressure and main effective pressure. So, the air/fuel ratio is changed

by different amounts of injected biogas. All other parameters and elements of

diesel engine remain unchanged.

Limitations:

- The dual fuel engine cannot operate without the supply of diesel fuel for ignition.

- The fuel injection jets may overheat when the diesel fuel flow is reduced to 10% or

15% of its normal flow. Larger dual fuel engines circulate extra diesel fuel through

the injector for cooling. To what extent the fuel injection nozzle can be affected is

however a question of its specific design, material and the thermal load of the

engine, and hence differs from case to case.

- A check of the injector nozzle after 500 hours of operation in dual fuel is

recommended.

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