IPE 301E: Fundamental of Mechanical Engineering

Dr. M. Muhshin Aziz KhanProfessor, Dept. of IPE, SUST

Sources of energy

Sources of Energy Energy Energy broadly means the capacity

of a physical system to do work and produce change.

Used in science to describe how much potential a physical system has to make change.

Energy exists in everybody whether they are human beings or animals or non living things.

Energy is intimately related to power.

Any form of energy can be converted into another form. However, the total energy will remain the same.

Energy is found in different forms, such as light, heat, sound and motion.

Forms of energy can all be put into two categories: kinetic and potential.

Characteristics of Good Sources It should have a high energy

output per unit mass or volume. It should be easily available. It should be easy to store and

transport. It should be economical.

Sources of energyThere are two main sources of energy: conventional or nonrenewable nonconventional or renewable

Conventional Source A natural source that cannot be

remade or regrown at a scale comparable to its consumption.

If exhausted, cannot be replenished in a short period of time (within a human life span) Fossilized fuels (as it takes

millions of year to form and cannot be replaced as fast as it is being consumed!)

Nuclear energy (as once uranium is used, it is gone!)

Sources of Energy

Conventional Sources Fossil Fuels

Coal, petroleum and natural gas are called fossil fuels.

Formed inside the earth from the remains of plants and animals after millions of years.

Fossil fuels are non renewable sources of energy. These should be used with care and

caution to let them last long.

Disadvantages of fossil fuels Burning of fossil fuels release gases and

harmful particles which causes air pollution.

Burning of fossil fuels release acidic oxides of sulphur and nitrogen which causes acid rain Harmful for living organisms, affects

soil and water, causes damage to buildings, corrosion of metals etc.

Burning of fossil fuels release a large amount of carbon dioxide gas which increases the temperature of the atmosphere and causes global warming (green house effect).

Advantages of fossil fuels Available in highly concentrated form Easy to store Reliable supply Lower cost per unit of energy

produced as the technology is matured

Fossil FuelsCoal: How is it made???

Before the dinosaurs, many giant plants died

in the swamp

Over millions of years, the plants were buried under water and dirt

Heat and pressure turned the dead plants

into coal.

Conventional Sources Oil and Gas: How are they made???

Tiny sea plants and animals died and were buried on

ocean floor. Over time, they were covered by layers of

slit and sand

Over millions of years, the remains were buried deeper

and deeper.

The enormous heat and pressure turned them into oil

and gas.

Nuclear Energy Energy released during nuclear reactions. During nuclear reactions,

some mass is converted into energy a very large amount of energy is

produced during nuclear reactions. Nuclear reactions are of two types:

Nuclear fission Nuclear fusion.

Nuclear fission The nucleus of a heavy atom like

uranium, plutonium, etc. splits into smaller nuclei and releases of a large amount of energy.

In a nuclear power plant the heat energy produced by a controlled nuclear fission chain reaction is used to produce steam which rotates the turbines of generators to produce electricity.

Nuclear fusion small nuclei fuse together to form a

heavier nucleus with the release of a very large amount of energy.

The energy of sun is produced by the fusion of hydrogen nuclei to form helium nucleus.

It is also used to make the hydrogen bomb.

Advantages of nuclear energy It produces a very large amount of

energy per unit mass than any other source of energy.

If safety measures are taken, it is more environment friendly than fossil fuels.

Disadvantages of nuclear energy The cost of a nuclear reactor is very

high. The availability of nuclear fuel is

limited.

Nonconventional or Renewable Sources Renewable Sources

Sources of energy which are being produced continuously in nature and inexhaustible. If consumed, these are naturally

replenished on a human timescale.

Renewable sources are those sources which are unlimited.

Solar, wind, hydropower, tidal and geothermal etc. are the renewable sources of energy.

About 16% of global final energy consumption comes from renewable,

10% coming from traditional biomass

3.4% from hydroelectricity New renewable (small hydro,

modern biomass, wind, solar, geothermal, and biofuels) accounted for another 3% and are growing very rapidly.

The share of renewable in electricity generation is around 19%, 16% of global electricity coming

from hydroelectricity 3% from new renewable

Renewable Sources Solar Energy

Energy obtained from the sun in the form of heat and light. The heat energy is used in solar

heating devices like solar cooker, solar water heater, solar furnaces etc.

The light energy is used in solar photovoltaic cells to generate electricity.

This energy comes from nuclear fusion reactions that take place deep inside the sun. Hydrogen nucleus fuse into helium

nucleus. Energy released from these reactions

flow out from the sun and escape into space.

It is cheaper to make electricity using solar energy rather than coal and other things.

Advantages Doesn’t produce Carbon dioxide. Have minimal impact on environment.

Disadvantages It is not constant, it depends on

weather conditions, time, and location.

Renewable Sources Wind Energy

Wind energy is believed to be five times total current global energy

production 40 times current electricity demand.

Energy obtained from the airflow. Kinetic energy of the wind is

converted into mechanical or electrical energy.

Windmill converts kinetic energy in to mechanical energy to do mechanical work like lifting water from the well, grinding grains in the flour mills etc.

Wind turbine converts kinetic energy to electrical energy by turning the generator.

A single wind turbine produces only a small amount of electricity.

Minimum wind speed requirement is 15 km/h. Areas where winds are stronger and

more constant are preferred locations for wind farms.

Offshore resources experience wind speeds of ~90% greater than that of land.

Wind power is growing at the rate of 30% annually, with a worldwide installed capacity

of 157,900 MW.

Renewable Sources Wind Energy

Advantages It is a renewable source of energy. It does not cause pollution.The recurring cost is less.Once the wind turbine is built,

wind power produces no green house gases during operation.

DisadvantagesWind is not available at all times.Wind turbines stop working if

there is no wind. A minimum wind speed of 15 km/h

is required.

Speed and direction of wind unreliable.

It requires a large area of land.

Renewable Sources Tidal Energy

Energy obtained by making use of the water movement from a high tide to a low tide. The periodic rise and fall of sea level

caused by gravitational pull of the sun and the moon.

They arise twice a day in Mid-Ocean. The vertical movement of water during

high tide and low tide is used to turn the turbines and generate electricity.

Water on high tide is first trapped in a artificial basin by constructing a tidal barrage and then allowed to escape on low tide.

Advantages An inexhaustible source of energy. Environment friendly source of energy

and doesn't produce greenhouse gases Disadvantages

Barrages across river mouths are expensive to build and disrupt shipping.

Very few ideal locations for construction of plant.

They are too localized to coastal regions only.

Renewable Sources Hydro Energy

It is the most widely used form of renewable energy.

Energy obtained from running water of the river using various methods. Potential energy i.e. water from the

river is first captured and stored by constructing dams.

Electrical power is produced by making use of the gravitational force of falling or flowing water.

Damless hydro systems derive kinetic energy from rivers and oceans without using a dam.

Advantages Flowing water is a renewable source of

energy.

The electricity produced does not cause pollution.

The water stored in dams can also be

used to control floods and for irrigation.

Once a dam is constructed, electricity can be produced at a constant-rate.

Often large dams become tourist attractions in their own right.

Disadvantages The initial cost is high. Large areas of land gets submerged

and the decomposition of vegetation produces methane gas which is a green house gas.

It causes displacement of people from large areas of land.