2. It is the capacity to do work.
It comes in different forms –
• heat (thermal)
• light (radiant)
• mechanical
• electrical
• chemical
• nuclear energy

3. Energy can be classified into 2 parts
• stored (potential) energy
• working (kinetic) energy.
For example,
the food you eat contains chemical
energy(potential), and your body stores
this energy until you release (kinetic) it
when you work or play.

4. All forms of energy are stored in different ways, in the energy sources
that we use every day. These sources are divided into two groups –
1. Renewable (an energy source that can be replenished in a short
period of time) and
2. Non renewable (an energy source that we are using up and cannot
recreate in a short period of time).
Renewable and non renewable energy sources can be used to produce
secondary
energy sources including electricity and hydrogen.

5. Renewable energy sources can be replenished in a short period
of time. The five renewable sources used most often are:
1. Biomass (including wood and wood waste ,municipal solid waste
,biogas ,ethanol and bio diesel.)
2. Water(hydropower)
3. Geothermal
4. Wind
5. Solar

6. Biomass is organic material made from plants and animals. Biomass contains stored
energy from the sun.
Production of biomass
1. Plants absorb the sun's energy in a process called photosynthesis.

7. 2. The chemical energy in plants gets passed on to animals and people that eat them.
*Biomass is a renewable energy source because we can always grow more trees and
crops, and waste will always exist. Some examples of biomass fuels are
wood, crops, manure, and some garbage.
When burned, the chemical energy in biomass is released as heat. If you have a
fireplace, the wood you burn in it is a biomass fuel. Wood waste or garbage can be
burned to produce steam for making electricity, or to provide heat to industries and
homes.

8. Burning biomass is not the only way to release its energy. Biomass can be
converted into other usable forms of energy such as
1. Methane gas
2. Bio diesel
3. Ethanol created by fermenting crops
4. Biogas
5. Burning wood
Biomass fuels provide about 3 percent of the energy used in the United States.
People in the USA are trying to develop ways to burn more biomass and less
fossil fuels. Using biomass for energy can cut back on waste and support
agricultural products grown in the United States.

9. Understanding the water cycle is important to understanding hydropower. In the water
cycle –
1.Solar energy heats water on the surface, causing it to evaporate.
2.This water vapour condenses into clouds and falls back onto the surface as precipitation.
3.The water flows through rivers back into the oceans, where it can evaporate and begin the
cycle over again.

10. • Mechanical energy in dams is derived by
directing, harnessing, or channelling moving
water.
• The amount of available energy in moving
water is determined by its flow or fall.
• The water flows through a pipe, or penstock ,
then pushes against and turns blades in a
turbine to spin a generator to produce
electricity.
• In a run-of-the-river system, the force of the
current applies the needed pressure.
• In a storage system, water is accumulated in
reservoirs created by dams, then released
when the demand for electricity is high.

11. Although hydroelectric power has led to economic progress around the world it has
also created serious ecological problems such as:
1. Large areas of forest and agricultural land is submerged.
2. Silting of reservoirs which reduces the life of hydropower installations.
3. Use of rivers for navigation and fisheries becomes difficult once the water is
dammed to generate electricity.
4. The resettlement of the displaced persons is a problem which has no ready
solution.
5. Large dams can induce seismic activity in seismically sensitive regions.

12. The word geothermal comes from the Greek words geo (earth) and therm (heat).
Geothermal = GEO(earth) + THERME(heat)
So, geothermal energy is heat from within the earth.
• We can use the steam and hot water produced inside the earth to heat
buildings or generate electricity.
• Geothermal energy is a renewable energy source because the water is
replenished by rainfall and the heat is continuously produced inside the earth.

13. Geothermal energy is generated in the earth's core, about 4,000 miles below the surface.
Temperatures hotter than the sun's surface are continuously produced inside the earth by
the slow decay of radioactive particles, a process that happens in all rocks.
The core itself has two layers:
•A solid iron core
•The magma an outer core made of very hot melted rock.
•The mantle
i. surrounds the core and is about
ii. 1,800 miles thick.
iii. Made of magma and rock.
•The crust is the outermost layer of the earth
i. forms the continents and ocean floors.
ii. It can be three to five miles thick under the oceans
iii. 15 to 35 miles thick on the continents.

14. Some applications of geothermal energy use the earth's temperatures near the surface,
while others require drilling miles into the earth. The three main uses of geothermal
energy are:
1) Direct Use and District Heating Systems which use hot water from springs or
reservoirs near the surface.
2) Electricity generation in a power plant requires water or steam at very high
temperature (300 to 700 degrees Fahrenheit). Geothermal power plants are
generally built where geothermal reservoirs are located within a mile or two of the
surface.
3) Geothermal heat pumps use stable ground or water temperatures near the earth's
surface to control building temperatures above ground.

15. Wind is simple air in motion. It is caused by:-
1. The uneven heating of the earth’s surface by the sun.
2. Since the earth’s surface is made of very different types of land and water, it
absorbs the sun’s heat at different rates.
During the day,
During the night,
• The winds are reversed because the air cools more rapidly over land than over
water.
In the same way, the large atmospheric winds that circle the earth are created
because the land near the earth's equator is heated more by the sun than the land
near the North and South Poles.

16. Today, wind energy is mainly used to generate electricity. Wind is called a renewable
energy source because the wind will blow as long as the sun shines.

17. The sun has produced energy for billions of years. Solar energy is the sun’s rays
(solar radiation) that reach the earth.
Solar energy can be converted into other forms of energy, such as :-
 Thermal (or Heat)
1. Heat water – for use in homes, buildings, or swimming pools.
2. Heat spaces – inside greenhouses, homes, and other buildings.
 Electrical energy
1. Photovoltaic
 (PV devices) or “solar cells” – change sunlight directly into electricity.
 They are used in remote locations
 Used to power watches, calculators, and lighted road signs.
2. Solar Power Plants
 indirectly generate electricity when the heat from solar thermal collectors is
used to heat a fluid which produces steam that is used to power generator.
 Out of the 15 known solar electric generating units operating in the United
States at the end of 2006, 10 of these are in California, and 5 in Arizona.
 No statistics are being collected on solar plants that produce less than 1
megawatt of electricity, so there may be smaller solar plants in a number of
other states.

18. The major disadvantages of solar energy are:
1. The amount of sunlight that arrives at the earth's surface is not constant. It
depends on location, time of day, time of year, and weather conditions.
2. Because the sun doesn't deliver that much energy to any one place at any
one time, a large surface area is required to collect the energy at a useful
rate.

19. Non renewable energy sources come out of the ground as liquids, gases and solids
such as:-
crude oil (petroleum)
Natural gas and propane
Coal
Uranium ore
-Among the above energy resources Coal, petroleum, natural gas, and propane are all
considered fossil fuels because they are formed from the buried remains of plants and
animals that lived millions of years ago.
-Uranium is not a fossil fuel.
* These energy sources are considered non renewable because they can not be replenished
(made again) in a short period of time.

20. How was oil formed ?
Oil was formed from the remains of animals and plants that lived millions of years ago in a
marine (water) environment before the dinosaurs. Over the years, the remains were
covered by layers of mud. Heat and pressure from these layers helped the remains turn into
what we today call crude oil . The word "petroleum" means "rock oil" or "oil from the earth."

21. Where do we get our oil?
Crude oil is :-
a smelly, yellow-to-black liquid
usually found in underground areas called reservoirs.
 Scientists and engineers explore a chosen area by studying rock samples from the
earth. Measurements are taken, and, if the site seems promising, drilling begins.
 Above the hole, a structure called a 'derrick' is built to house the tools and pipes going
into the well. When finished, the drilled well will bring a steady flow of oil to the
surface
The world's top five crude oil-producing countries are:
1. Saudi Arabia
2. Russia
3. United States
4. Iran
5. China

22. How Does Oil Impact The Environment?
1) Exploring and drilling for oil may disturb land and ocean habitats. New technologies
have greatly reduced the number and size of areas disturbed by drilling, sometimes
called "footprints.“
2) If oil is spilled into rivers or oceans it can harm wildlife
3) A refinery is a factory where crude oil is processed into petroleum products. Because
many different pollutants can escape from refineries into the air, the government
monitors refineries and other factories to make sure that they meet environmental
standards.
4) Gasoline is used in cars, diesel fuel is used in trucks, and heating oil is used to heat our
homes. When petroleum products are burned as fuel, they give off carbon dioxide, a
greenhouse gas that is linked with global warming.

23. How Was Natural Gas Formed?
1. Millions of years ago, the remains of plants and animals decayed and built up in thick
layers. This decayed matter from plants and animals is called organic material -- it
was once alive.
2. Over time, the mud and soil changed to rock, covered the organic material and
trapped it beneath the rock. Pressure and heat changed some of this organic
material into:-
Coal
oil (petroleum)
natural gas (tiny bubbles of odourless gas)
The main ingredient in natural gas is methane, a gas (or compound) composed of one
carbon atom and four hydrogen atoms.
CH4

24. Uses of natural gas:-
•LPG (Liquefied Petroleum Gas) i.e. Butane for cooking.
•CNG (Compressed Natural Gas) for vehicles.
Impact of natural gas on environment:-
1. Natural gas burns more cleanly than other fossil fuels. It has fewer emissions of
sulfur, carbon, and nitrogen than coal or oil, and when it is burned, it leaves almost no
ash particles.
2. Being a clean fuel is one reason that the use of natural gas, especially for electricity
generation, has grown so much and is expected to grow even more in the future.
3. As with other fossil fuels, burning natural gas produces carbon dioxide which is a very
important greenhouse gas.

25. Coal is :
a combustible black or brownish-black sedimentary rock
composed mostly of carbon and hydrocarbons
It is the most abundant fossil fuel
How was coal formed?
Coal is a non renewable energy source because it takes millions of years to create. The
energy in coal comes from the energy stored by plants that lived hundreds of millions
of years ago, when the earth was partly covered with swampy forests.

26. Types of coal?
 Lignite
 Sub bituminous
 Bituminous coal
 Anthracite
Coal and the environment
1. When coal is burned as fuel, it gives off carbon dioxide, the main greenhouse gas that
is linked with global warming.
2. Burning coal also produces emissions, such as sulphur, nitrogen oxide (NOx), and
mercury, that can pollute the air and water.
3. Sulphur mixes with oxygen to form sulphur dioxide (SO2), a chemical that can affect
trees and water when it combines with moisture to produce acid rain.
4. Emissions of nitrogen oxide help create smog, and also contribute to acid rain.

27. Nuclear energy is from atoms?
Nuclear energy is energy in the nucleus (core) of an atom. Atoms are tiny
particles that make up every object in the universe. There is enormous energy in
the bonds that hold atoms together.
Nuclear energy can be used to make electricity. But first the energy must be
released. It can be released from atoms in two ways:
In nuclear fusion, energy is released when atoms are combined or fused
together to form a larger atom. This is how the sun produces energy.
In nuclear fission, atoms are split apart to form smaller atoms, releasing
energy. Nuclear power plants use nuclear fission to produce electricity.
Nuclear fuel URANIUM
The fuel most widely used by nuclear plants for nuclear fission is uranium.
Uranium is non renewable, though it is a common metal found in rocks all over
the world.
Nuclear plants use a certain kind of uranium, U-235, as fuel because its atoms
are easily split apart . Though uranium is quite common, about 100 times more
common than silver, U-235 is relatively rare.

28. NUCLEAR FISSION
During nuclear fission, a small particle called a neutron hits the uranium atom and
splits it, releasing a great amount of energy as heat and radiation.
More neutrons are also released. These neutrons go on to bombard other uranium
atoms, and the process repeats itself over and over again. This is called a chain
reaction.
Use of nuclear energy
Most power plants, including nuclear plants, use heat to produce electricity. They rely on
steam from heated water to spin large turbines, which generate electricity. Instead of
burning fossil fuels to produce the steam, nuclear plants use heat given off during
fission. In nuclear fission, atoms are split apart to form smaller atoms, releasing energy.

29. Nuclear power and environment
Compared to electricity generated by burning fossil fuels, nuclear energy is clean.
Nuclear power plants produce no air pollution or carbon dioxide but a small amount of
emissions result from processing the uranium that is used in nuclear reactors.
Like all industrial processes, nuclear power generation has by-product wastes:
 spent (used) fuels
 other radioactive waste
 heat
Spent fuels and other radioactive wastes are the principal environmental concern for
nuclear power. Most nuclear waste is low-level radioactive waste. It consists of ordinary
tools, protective clothing, wiping cloths and disposable items that have been
contaminated with small amounts of radioactive dust or particles.
These materials are subject to special regulation that govern their disposal so they will not
come in contact with the outside environment.