FOSSIL FUELS &
ALTERNATIVE ENERGY SOURCES
4TH YEAR CHEM MAJOR
► FOSSIL FUELS
► ALTERNATIVE ENERGY SOURCES
► Fossil fuels are basically any carbon based substance that is used by mankind as a
source of energy. They are formed by natural processes such as anaerobic
decomposition of buried dead organisms.
► Fossil fuels contain high percentages of carbon and include coal, petroleum,
and natural gas . They range from volatile materials with low carbon : hydrogen ratios
like methane, to liquid petroleum to nonvolatile materials composed of almost pure
carbon, like anthracite coal.
► Fossil fuels are of great importance because they can be burned (oxidized to carbon
dioxide and water), producing significant amounts of energy per unit weight.
► Fossil Fuels are a nonrenewable resource because they were formed from the remains
of plant and animal matter from over 65 million years ago. Once they are gone, they
are gone forever!
FOSSIL FUEL COMBUSTION
Burning fossil fuels is responsible for environmental issues that are high on the political agenda
these days. Examples are greenhouse gas accumulation, acidification, air pollution, water
pollution, damage to land surface and ground-level ozone.
The principal air pollutants resulting from fossil fuel combustion are the following:
(a) carbon monoxide
(b) the oxides of sulfur, SO2 and SO3 (represented as SOx)
(c) the oxides of nitrogen, NO and NO2 (NOx)
(d) ‘particulates’, consisting primarily of very fine soot and ash particles.
► Carbon monoxide (CO) is a product of incomplete combustion of any fuel. It is both a
highly poisonous gas and the principal constituent of photochemical smog.
► Sulfur oxides arise during combustion from oxidation of sulfur in sulfur containing fuels (some
coals and some petroleum-based products). The principal product is sulfur dioxide:
S (in fuel) + O2 --> SO2
When it is released to the atmosphere, it can react with oxygen in the air to form sulfur trioxide:
2 SO2 + O2 --> 2 SO3
Sulfur trioxide can absorb moisture from the atmosphere or readily dissolve in rain
water to form very fine droplets of sulfuric acid and fall to the earth as acid rain.
Inhalation of these droplets can harm the respiratory system. Chronic exposure leads to
a much greater likelihood of suffering from bronchitis.
► Nitrogen oxides have two sources : Fuel NOx is produced when nitrogen atoms
chemically combined with the molecules of the fuel are oxidized during the combustion
process to form nitric oxide:
2 N (in fuel) + O2 --> 2 NO
In addition, thermal NOx is produced in some combustion processes that operate at such
high temperatures that nitrogen molecules in the air are oxidized to nitric oxide:
N2 (in air) + O2 --> 2 NO
2 NO + O2 --> 2 NO2
Nitrogen oxides will react further with water and oxygen to form nitric acid:
4 NO2 + 2 H2O + O2 --> 4 HNO3
Like sulfuric acid, nitric acid is a very strong acid that easily corrodes or attacks many
materials. Nitric acid is also a component of acid rain.
► Particulate Matter emissions (soot and fly ash) are also a concern because they
can contribute to long-term respiratory problems. Many of these particles are
extremely small, of the order of 10 micrometer or less, and they are thus
suspended in the air we breathe. After inhaling them, they get trapped in the very
thin air passages inside the lungs. Over a period of years this reduces the air
capacity of the lungs. Reduced air capacity leads in turn to severe breathing and
respiratory problems. Chronic asthma or emphysema can result, as well as
increased general susceptibility to respiratory diseases.
► The total fossil fuel used in the year 1997 is the result of 422 years of all plant
matter that grew on the entire surface and in all the oceans of the ancient earth.
ALTERNATIVE ENERGY SOURCES
The nature of what constitutes an alternative energy source has changed considerably
over time, as have controversies regarding energy use.
“Energy fueled in ways that do not use up natural resources or harm the environment “
- Oxford Dictionary.
“Energy derived from sources that do not use up natural resources or harm the
environment “ - Princeton WordNet .
Energy generated from alternatives to fossil fuel. Need not be renewable.
► In a general sense, alternative energy as it is currently conceived, is that which is
produced or recovered without the undesirable consequences inherent in fossil fuel
use, particularly high carbon dioxide emissions, an important factor in global
“I’d put my money on the sun and solar
energy. What a source of power! I hope
we don’t have to wait ‘til oil and coal run
out before we tackle that.”
- Thomas Edison
Solar energy is an energy source that involves tapping the radiant light energy that
is emitted by the sun and converting it into other forms of energy, such as heat and
Solar energy reaching the earth is incredible. By one calculation, 30 days of
sunshine striking the Earth have the energy equivalent of the total of all the planet’s
fossil fuels, both used and unused!
Solar technologies are broadly characterized as either Passive solar or Active solar
depending on the way they capture, convert and distribute solar energy.
PASSIVE SOLAR HEATING
Passive solar design uses sunshine to heat and light homes and other buildings without
mechanical or electrical devices . Heating the building through the use of solar energy involves
the absorption and storage of incoming solar radiation, which is then used to meet the heating
requirements of the space.
►The most common passive solar system is
called direct gain. Direct gain refers to the
sunlight that enters a building through
windows, warming the interior space . A direct
gain system includes south facing windows
and a large mass placed within the space to
receive the most direct sunlight in cold
weather and the least direct sunlight in hot
► If solar heat is to be used when the sun is
not shining, excess heat must be stored. In
indirect gain the solar energy is collected and
stored in one part of the house and use natural
heat transfer to distribute heat to the rest of the
house . Thermal mass ,materials with a high
capacity for absorbing and storing heat (e.g.,
brick, concrete masonry, concrete slab, tile,
adobe, water) are used for this purpose.
► It has been estimated that 40 to 90% of most homes’ heating requirements could be
supplied by passive-solar heating systems.
The generation of voltage across the PN junction in a semiconductor due to the absorption of light
radiation is called photovoltaic effect. The Devices based on this effect is called photovoltaic device.
Solar cell is a photovoltaic device that converts the light energy into electrical energy based on the
principles of photovoltaic effect . Solar cell (crystalline Silicon) consists of a n-type semiconductor
(emitter) layer and p-type semiconductor layer (base). The two layers are sandwiched and hence
there is formation of p-n junction and an electric field within the cell.
SOLAR CELL [PHOTOVOLTAIC CELL]
During the incident of light energy, in
n-type material, electrons can gain
energy and move into the p-type
region. Then they can no longer go
back to their original low energy
position and remain at a higher energy.
The process of moving a light-
generated carrier from p-type region
to n-type region is called collection.
These collections of carriers (electrons)
can be either extracted from the
device to give a current, or it can
remain in the device and gives rise to a
► The surface receives about 47% of the total solar energy that reaches the Earth.
Only this amount is usable. Still In principle, the amount of solar energy that
reaches the Earth’s surface could provide for all human energy needs forever .
A hydroelectric plant uses the flow of water from a higher to a lower elevation to
generate power. Hydroelectric plants provide about 20% of the world’s electricity.
The most common type of hydroelectric power plant is an
impoundment facility. An impoundment facility, typically a
large hydropower system, uses a dam to store river water in
a reservoir. Water released from the reservoir flows through
a turbine, spinning it, which in turn activates a generator to
produce electricity. The water may be released either to
meet changing electricity needs or to maintain a constant
There's another type of hydropower plant, called the pumped-storage plant. In a
conventional hydropower plant, the water from the reservoir flows through the
plant, exits and is carried down stream. A pumped-storage plant has two
Upper reservoir - Like a conventional hydropower plant, a dam creates a
reservoir. The water in this reservoir flows through the hydropower plant to
Lower reservoir - Water exiting the hydropower plant flows into a lower reservoir
rather than re-entering the river and flowing downstream.
Using a reversible turbine, the plant can pump water back to the upper reservoir.
This is done in off-peak hours. Essentially, the second reservoir refills the upper
reservoir. By pumping water back to the upper reservoir, the plant has more
water to generate electricity during periods of peak consumption.
PUMPED – STORAGE POWER PLANT
In times of high energy demand, the pumped-storage plant releases water from the upper
reservoir to the lower reservoir, turning the turbines along the way. When the energy demand
decreases, the plant pumps water from the lower reservoir back to the upper reservoir. Some of
the plant’s own power is used up during pumping. Droughts do not affect pumped-storage plants,
because water can continually be pumped into the upper reservoir to keep the electricity
A diversion plant, sometimes called
a run-of-river facility, in most cases
does not use a dam. The plant
diverts some of the river water
through a canal or penstock, where
the flow powers a turbine.
These plants rely entirely on the
flow of the river to produce
electricity. There is no dam to
artificially raise the height of the
water. A diversion plant depends
solely on the landscape to create
Magma rising from the mantles brings unusually hot material near the surface. Heat from
the magma, in turn, heats any groundwater. This is the basis for generating geothermal
Direct uses of geothermal energy is appropriate for sources below 150C. It includes :
• Space heating
• Air conditioning
• Industrial processes
• Hot water
• Resorts and Pools
• Melting snow
Geothermal energy can be used in a direct or indirect way. The choice is
determined by the available temperature, the presence of a reservoir, the
intended purpose and the economic context.
► Worldwide, there are now about 40
geothermal power plants and most
of them are built along plate tectonic
Where temperatures are insufficient
to meet the space heating
requirements of residential or
commercial buildings, Geothermal
heat pumps can be used to boost
the temperature to desired levels.
Space heating is provided by means
of pumped wells or through the use
of down hole heat exchangers.
► In fact using geothermal
energy to heat is about 2-3
times as common as using it
to create electricity.
Space heating can also be
provided on a building by
building basis or increasingly
via a district heating network
that supplies the needs of
multiple consumers via an
underground piping network
connected to one or multiple
wells or downhole heat
The development of geothermal
district heating, led by the
Icelanders, has been one of the
fastest growing segments of the
geothermal space heating
industry and now accounts for
over 75% of all space heating
provided from geothermal
Given the proper circumstances, natural
hot water may be used to space cool,
Absorption refrigeration is a cooling
process that is efficiently employed to
cool areas of human occupancy.
Geothermal absorption refrigeration
units create "cold" by making use of a
well known physical phenomena: the
boiling temperature of a liquid depends
on pressure; and heat is "robbed" from
the environment when a liquid boils.
The use of geothermal space cooling
wiII depend upon the location,
temperature, production (flow) rates
and chemical quality of hot water in
prospective geothermal reservoirs.
INDIRECT USE : GENERATION OF ELECTRICITY
The indirect use of Geothermal energy includes the utilization of Super-heated
water or steam from earth's interior in running the turbines of a conventional power
plant to generate electricity. The water is then cooled and returned to the heat
source. Generation of Electricity is appropriate for sources >150oC .
There are three types of geothermal power plants: Dry Steam, Flash Steam, and
DRY STEAM POWER
Steam is used directly from the wells to drive
a turbine generator. Wastewater from the
condenser is injected back into the
subsurface to help extend the useful life of
the hydrothermal system.
Resource temperature range :
220°C to 320°C.
FLASH STEAM POWER
Flash plants take super heated water out of the
ground, allowing it to boil as it rises to the
surface, then separates the steam from the
water in a surface vessel (called a steam
separator) and uses the steam to turn a turbine
generator. The remaining water and steam are
then injected back into the source from which
they were taken.
Resource temperature range : 200°C to 300°C.
BINARY CYCLE POWER
In binary cycle geothermal power plants, pumps are
used to pump hot water from a geothermal well,
through a heat exchanger, and the cooled water is
returned to the underground reservoir. A second
"working" or "binary" fluid with a low boiling point,
typically a Butane or Pentane hydrocarbon , is
pumped at fairly high pressure through the heat
exchanger , where it is vaporized and then directed
through a turbine. The vapor exiting the turbine is
then condensed by cold air radiators or cold water
and cycled back through the heat exchanger.
1- Wellheads , 2 - Ground surface , 3 -Generator
4 - Turbine, 5 -Condenser, 6 - Heat exchanger , 7 - Pump
Resource temperature range : 120°C to 190°C.
Wind Power is the conversion of wind energy into a useful form of energy, such as using wind turbines to
make electrical power, windmills for mechanical power, wind pumps for water pumping or drainage,
or sails to propel ships. It is predicted that by 2030, wind energy will supply at least twice the electricity it
WIND MILL WIND PUMP
WIND POWER PLANT
A wind turbine or wind power plant is a device that converts kinetic energy from the
wind into electric current . Modern wind turbine generators are highly
sophisticated machines, taking full advantage of state-of-the-art technology, led by
improvements in aerodynamic and structural design, materials technology and
mechanical, electrical and control engineering and capable of producing several
megawatts of electricity.
A wind turbine obtains its power input by converting the force of the wind into a torque
(turning force) acting on the rotor blades. The rotor is connected to the main shaft,
which spins a generator to create electricity. The amount of energy which the wind
transfers to the rotor depends on the density of the air, the rotor area, and the wind
The kinetic energy of a moving body is proportional to its mass (or weight). The kinetic
energy in the wind thus depends on the density of the air, i.e. its mass per unit of
volume. In other words, the "heavier" the air, the more energy is received by the
► One important factor is that with a doubling of wind speed, power output
increases by a factor of 8.
Ocean energy or ocean power refers to the energy carried by ocean waves, tides, salinity,
and ocean temperature differences. The movement of water in the world’s oceans creates
a vast store of kinetic energy, or energy in motion. This energy can be harnessed
to generate electricity to power homes, transport and industries.
Waves are caused by a number of forces,
i.e. wind, gravitational pull from the sun
and moon, changes in atmospheric
pressure, earthquakes etc. Waves
created by wind are the most common
waves. Unequal heating of the Earth’s
surface generates wind, and wind
blowing over water transfers energy and
thus generates waves.
The amount of energy transferred and the size of the resulting wave depend on the
• Speed of wind : The faster the wind is traveling, the bigger a wave will be.
• Time of wind : The wave will get larger the longer the length of time the wind is hitting it.
• Distance of wind : The farther the wind travels against the wave (known as fetch), the
bigger it will be.
In order to extract energy from this never ending motion of waves, two technologies are mainly
used They are : Tapered Channel Method and Floating Device Method.
Floating wave energy devices generate electricity
through the harmonic motion of the floating part of
the device. The object can be mounted to a floating
raft or to a device fixed on the ocean floor. In these
systems, the devices rise and fall according to the
motion of the wave and electricity is generated
through their motion.
• As a wave enters the collector,
the surface of the water column
rises and compresses the volume
of air above it.
• The compressed air is forced
into an aperture at the top of the
chamber, moving past a turbine.
• As the wave retreats, the air is
drawn back through the turbine
due to the reduced pressure in
Tidal power, also called tidal energy,
is a form of hydropower that converts
the energy of tides into useful forms
of power - mainly electricity.
Tides are the rise and fall of sea levels
caused by the combined effects of
the gravitational forces exerted by the
Moon and the Sun and the rotation of
Tidal power plants use the flowing
water between low and high tides to
generate electricity. When tides
comes into the shore, they can be
trapped in reservoirs behind dams.
Then when the tide drops, the water
behind the dam can be let out just
like in a regular hydroelectric power
plant. In order for this to work well,
you need large increases in tides.
An increase of at least 16 feet between low tide to high tide is needed.
Water speeds of nearly 1/10 the speed of wind can provide the same
energy output. A plant in France makes enough energy from tides to
power 240,000 homes.
Open-cycle OTEC uses warm surface water directly to make electricity. The water from the
surface is put into a near vacuum. A near vacuum is a container which has had most of the air
sucked out of it. This allows the water from the surface to turn into steam, because when
water is in a near vacuum its boiling temperature is lower.
The expanding steam then drives a
low-pressure turbine attached to
an electrical generator. The steam,
which has left its salt and other
contaminants in the low-pressure
container, is pure fresh water. It is
condensed into a liquid by exposure
to cold temperatures from deep-
ocean water. This method
fresh water, suitable for drinking
water, irrigation or aquaculture.
If both the open and closed
systems are combined together,
a hybrid system is created. This
improves the amount of electricity
and fresh water produced.
OCEAN THERMAL ENERGY
Ocean thermal energy
conversion (OTEC) uses the
temperature difference between
cooler deep and warmer shallow or
surface ocean waters to run a heat
engine and produce useful work,
usually in the form of electricity.
OTEC works best when the
temperature difference between
the warmer, top layer of the ocean
and the colder, deep ocean water is
about 20°C (36°F). These conditions
exist in tropical coastal areas,
roughly between the Tropic of
Capricorn (northern Argentina to
Madagascar to Australia) and the
Tropic of Cancer (Mexico, Middle
East, India, South of Taiwan).
CLOSED CYCLE OTEC
Biomass is organic material made from plants and animals. Biomass contains
stored energy from the sun.
• Most of the world still relies very heavily on fossil fuels, but slowly but surely,
attention is being diverted to alternative energy.
• The most important aspects of most alternative energy sources is that they
promise clean, pollution-free energy.
• Energy use in the future will not be dominated by a single source.
• Bertani R., 2005: World geothermal power generation in the period 2001–2005.