Types of energy

NON – RENEWABLE ENERGY

SOURCESNon – renewable resources are those resources which once used up cannot be replenished in a short period of time.

Non – renewable resources of energy are also called convectional sources of energy.

Since these energy resources get exhausted they are also known as exhaustible sources of energy.

Non –renewable Energy Sources

COAL PETROLEUM

NUCLEAR FUELS(URANIUM)NATURAL

GAS

NON – RENEWABLE ENERGY RESOURCES

COAL

PETROLEUM

NUCLEAR FUELS(URANIUM)

NATURAL GAS

RENEWABLE ENERGY SOURCESRenewable energy sources can be replenished in a short period of time and can be used again to generate energy.

These energy resources are also known as non –convectional, inexhaustible and alternative sources of energy.

Renewable Energy Sources

WOOD

GEOTHERMAL ENERGY

TIDAL ENERGY

WIND ENERGY

RENEWABLE ENERGY RESOURCES

WOOD

GEOTHERMAL ENERGY

TIDAL ENERGY

WIND ENERGY

What is a good source of energy?

We can find out whether a given source of energy is good or not by the following qualities of a good energy resource.

A good energy resource is one:

Which would do a large amount of work per

un it mass(or per unit volume).

Which is cheap and easily available.

Which is easy to store and transport.

CONVECTIONAL SOURCES OF ENERGY

• The traditional sources of energy which are familiar to most people are known as convectional sources of energy.

EXAMPLES-wood, coal , petroleum , natural gas, etc.

FOSSIL FUELS• A natural fuel formed deep under the earth

from the pre-historic remains of living organisms is called fossil fuels.

• Coal, petroleum and natural gas are fossil fuels.

• These are the main sources of energy for generating electricity in power plants.

COALCoal is a complex mixture of compounds of carbons, hydrogen and oxygen, and some free carbon.A lot of heat is produced during the burning of fuel which makes it a good fuel.

PETROLEUMThe crude oil petroleum is a complex

mixture of several solid, liquid and

gaseous hydrocarbons mixed with water,

salt and earth particles.

The fractional distillation of petroleum

gives us the fractions which can be used

as fuel: petroleum gas, petrol, diesel,

kerosene and fuel oil.

A petroleum refinery

NATURAL GAS

Natural gas mainly consists of methane, with small

quantities of ethane and propane.

Natural gas occurs deep under the crust of earth along

with petroleum deposits.

Natural gas is formed under the earth by the

decomposition of vegetable matter lying under the

water. This decomposition is carried out by anaerobic

bacteria.

A power plant in which fuel is burnt to produce heat energy which is converted into electrical energy is known as thermal power plant.Large amount of fossil fuels are burnt each day in power stations to heat up water to produce steam which further runs the turbines to generate electricity.

THERMAL POWER PLANT

HYDRO POWER PLANTS

A power plant that produces electricity by flowing water to rotate turbines is called hydro power plant.

Hydro power plants convert the potential energy of falling water into electricity.

Since there are few water falls which could be used as a source of potential energy, hydro power plants are associated with dams.

Working of Hydro Power Plants

In order to produce hydel electricity, high-rise dams are constructed on the river to obstruct the flow of water and thereby collect water in large reservoirs.

The water level rises and in this process the kinetic energy of flowing water gets transformed into potential energy.

The water from the high level in the dam is carried through pipes, to the turbine, at the bottom of the dam.

Since the water in the reservoir would be refilled each time it rains, hydro power is a renewable source of energy.

Schematic view of a Hydro Power Plant

Improvements in the Technology for Using Convectional Sources of Energy

BIO MASSBiomass includes wood, agricultural wastes and cow dung.Since the fuels like wood, agricultural wastes and cow dung are all plant and animal products , they are called biomass or biofuels.Biomass is a renewable source of energy.

The Case of Wood and Charcoal

Wood is a biomass. When wood is burnt, heat is produced. So, wood has been used as a fuel for a long time.Disadvantages of using wood as a fuel:

i. the burning of wood produces a lot of smoke which pollutes air.

ii. the calorific value of wood is low. This means that wood produces less heat per unit mass , on burning.

Due to the improvement in the technology for using the

convectional sources of energy, wood can be converted into a

much better fuel called charcoal.

When wood is burnt in a limited supply of oxygen, water and

volatile materials present in it get removed and charcoal is left

behind as the residue.

Charcoal burns without flames, is comparatively smokeless and

has a higher het generating ability.

Cow dung is biomass. Cow dung is the excreta of cattle animals such as cows and buffaloes. Disadvantages of using cow dung directly as a fuel:

i. Cow dung contains important nutrients which are needed by the sol. So, burning of cow dung in the form of cow dung cakes destroys the useful nutrients which can be otherwise used as a manure.

ii. Cow dung cakes produces a lot of smoke on burning which causes air pollution.

iii. Cow dung cakes do not burn completely, they produce a lot of ash as a residue.

iv. Cow dung cakes have low calorific value.

The Case of Cow Dung and Biogas

Since there are many disadvantages in using cow dung as a

fuel directly, it is better to prepare biogas from cow dung.

Only the organic matter of cow dung is decomposed and

converted into biogas.

When used in this way, cow dung

gives us a double advantage :

it gives us a clean fuel called biogas

the spent cow dung can be used as a manure because it

still contains elements like nitrogen and phosphorus.

BIOGAS PLANT

BIOGAS PLANT

A biogas plant has a dome shaped dome like structure built with bricks.

A slurry of cow dung and water is made in the mixing tank from where it is fed into the digester.

The digester is a sealed chamber in which there is no oxygen.

Anaerobic micro organisms break down complex compounds of the cow dung slurry.

It takes a few days for the decomposition process to complete and generate gases like methane, carbon dioxide, hydrogen and hydrogen sulphide.

The biogas is stored in the gas tank above the digester from which they are drawn through pipes for use.

Schematic diagram of a Bio Gas Plant

Advantages of Bio GasBio gas is an excellent fuel as it contains up to 75% methane.It burns without smoke, leaves no residue like ash in wood, charcoal and coal burning.Its heating capacity is high.Bio gas is also used for lighting.The slurry left behind is removed periodically and used as an excellent manure.The large scale utilization of bio waste and sewage material provides a safe and efficient method of waste disposal besides supplying energy and manure.

WIND ENERGY

The uneven heating of the landmass and water bodies by solar radiation generates air movement and causes wind to blow.The kinetic energy of the wind can be used to work.The energy of the wind is harnessed by using a windmill.

WIND GENERATORTo generate electricity, the rotary motion of the windmill is used to turn the turbine of the electric generator.The output of a single windmill is quite small and cannot be used for commercial purposes.Therefore a large number of windmills are erected over a large area, which is known as wind energy farm.The wind energy output of each windmill is coupled together to get electricity on a commercial unit.

WIND ENERGY FARM

Advantages of Wind Energy

An important advantage of using wind energy for generating

electricity is that its use does not cause any air pollution.

Wind energy is a renewable source of energy and it will never

get exhausted .

The increased use of wind energy will help us conserve fossil

fuels so that they last longer.

Limitations of Using Wind Energy

The wind energy farms can be established only where wind flows for most parts of the year.

The wind speed should be higher than 15 km/h to maintain the required speed of the turbine.

The wind energy farms require a large area of land.

The setting up wind energy farms is very expensive.

ALTERNATIVE SOURCES OF ENERGY(Non- convectional sources of energy)

SOLAR ENERGYThe energy obtained from the sun is called solar energy.The sun has been radiating an enormous amount of energy at the present rate for nearly 5 million years and will continue radiating energy at that rate for about 5 billion years more.Only a small part of solar energy reaches the outer layer of the earth’s atmosphere.Nearly half of it is absorbed while passing through the atmosphere and rest reaches the surface of the earth.

SOLAR COOKER

The solar cooker is a device which is used to cook food by utilizing the heat energy radiated by the sun.

A solar cooker consists of an insulated metal box which is painted all black from inside.

There is a thick glass sheet cover over the box and a plane mirror reflector is also painted black from outside.

The metal containers are then placed inside the solar cooker box and covered with the glass sheet.

SOLAR CELLSSolar cell is a device which converts solar energy directly into electricity.

A solar cell develops a voltage of 0.5-1 V and can produce about 0.7 W of electricity when exposed to the sun.

A large number of solar cells are combined in an arrangement called solar cell panel that can deliver enough electricity for practical use.

SOLAR CELL PANEL

Advantages of Solar Cells

The main advantage is that they do not have any moving parts, require almost no maintenance and work quite satisfactorily without the use of any light focusing device.

Another advantage is that they can be set up in remote, inaccessible and very sparsely inhabited areas where the laying of usual power transmission lines is difficult and expensive.

Disadvantages of Solar Cells

The main disadvantage of solar cells is that they are expensive.

The special grade silicon needed for making solar cells is expensive.

Silver wire used to interconnect solar cells for making solar cell panels is very expensive.

The entire process of making solar cell is also very expensive.

ENERGY FROM THE SEA

• The energy from the sea is obtained in mainly three forms:

i. TIDAL ENERGY

ii. WAVE ENERGY

iii. OCEAN THERMAL ENERGY

TIDAL ENERGYThe rise of water due to gravitational pull of the moon is called “high tide” whereas the fall of sea water is called “low tide”.

The enormous movement of water between high tides and low tides provides a very large source of energy in the coastal areas of the world.

The tidal energy can be harnessed by constructing a tidal barrage or tidal dam across a narrow opening to the sea.

A turbine fixed at the opening of the dam converts tidal energy to electricity.

The tidal energy is not likely to be a source of potential energy because there are only a few sites around the world which are suitable for building tidal dams.

Due to the blowing of wind on the surface of sea, very fast sea-waves move un its surface.Due to their high speed, sea waves have a lot of kinetic energy in them.The energy of moving sea waves can be used to generate electricity.A wide variety of devices have been developed to trap sea wave energy to turn turbines and drive generators for the production of electricity.

OCEAN THERMAL ENERGY The water at the surface of the sea or ocean is heated by the sun

while the water in deeper sections is relatively cold.

This difference in temperature is exploited to obtain energy in

thermal energy conservation plants.

These plants can operate if the temperature difference between the

water at the surface and water at depths up to 2 km is 20° C.

The warm surface water is used to boil a volatile liquid like

ammonia.

The vapours of the liquid are then used to run the turbine of the

generator.

The cold water from the depth of the ocean is pumped up to cool

the used up vapours and convert them again to liquid.

OCEAN THERMAL ENERGY conservation plant

GEOTHERMAL ENERGY

Geothermal energy is the heat energy from the rocks present inside the earth.

Due to geological changes, molten rocks formed in the deeper hot regions of earth’s crust are pushed upward trapped in certain regions called hot spots.

When underground water comes in contact with the hot spot, steam is generated.

The steam trapped in rocks is routed through a pipe to a turbine and used to generate electricity.

GEOTHERMAL ENERGY PLANT

NUCLEAR ENERGYNuclear energy is generated by the process of nuclear fission.

The nucleus of a heavy atom(such as uranium, plutonium or thorium) , when bombarded with low – energy neutrons , can be split apart into lighter nuclei.

When this is done a tremendous amount of energy is released if the mass of the original nucleus is just a little more than the sum of the masses of the individual products.

Nuclear Power Plant

ENVIRONMENTAL CONSEQUENCES

Some environmental consequences of the increasing demand of energy are the following:

i. The combustion of fossil fuels is producing acid rain.ii. The burning of fossil fuels is increasing the amount of greenhouse gas carbon

dioxide in the atmosphere. iii. The cutting down of trees for firewood is causing soil erosion and destroying

wild life.iv. The construction of hydro power plants is disturbing ecological balance.v. Nuclear power plants are increasing radioactivity in the environment.

How Long Will Energy Resources Last

It has been estimated that the world’s known estimated coal reserves are expected to last for another 200 years compared to around 40 years for the known petroleum oil resources and around 60 years for the known reserves of natural gas.We can assure a constant supply of energy by replacing the trees we cut by using bio mass.