What is energy?

Energy is the capacity to do work.

Oil, wind water just to name a few that provide us the energy we need in our daily lives. For example, we use oil to produce gasoline

for our cars. We use natural gas, coal, solar and wind power to generate electricity that makes the computer you are using work!

Energy sources can be classified into two

an energy source that can be easily replenished

Solar Energy

Wind Energy

Geothermal Energy

Hydraulic Energy

an energy source that we are using up and cannot recreate

Chemical/Fuel Energy

Nuclear Energy

The sun has produced energy for billions of years.  Solar energy is the sun’s rays (solar radiation) that reach the Earth. This energy can be converted into other forms of energy, such as heat and electricity.

Solar energy are converted into electricity in two ways :

Solar Cells

Photovoltaic (PV devices) or “solar cells” change sunlight directly into electricity. Individual PV cells are grouped into panels and arrays of panels that can be used in a wide range of applications ranging from single small cells that charge calculator and watch batteries, to systems that power single homes, to large power plants covering many acres.

Sunlight is composed of photons, or particles of solar energy.  These photons contain various amounts of energy. When photons strike a photovoltaic cell, they may be reflected, pass right through, or be absorbed.  Only the absorbed photons provide energy to generate electricity.  When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material's atoms. 

Concentrating Solar Power Plants generate electricity by using the heat from solar thermal

collectors to heat a fluid which produces steam that is used to power the generator.

Concentrating solar power plants

Three main types of solar thermal power systems are

Parabolic Trough Solar Power Tower

Solar Dish

A parabolic trough collector has a long parabolic-shaped reflector that focuses the sun's rays on a receiver

pipe located at the focus of the parabola.  The collector tilts with the sun as the sun moves from east to

west during the day to ensure that the sun is continuously focused on the

receiver.

A solar dish/engine system uses concentrating solar collectors that track the sun, so they always point

straight at the sun and concentrate the solar energy at the focal point of the

dish.

The engine in a solar dish/engine system converts heat to mechanical power by compressing the working

fluid when it is cold, heating the compressed working fluid, and then expanding the fluid through a turbine or with a piston to produce work.  The

engine is coupled to an electric generator to convert the mechanical

power to electric power.

A solar power tower or central receiver generates electricity from sunlight by focusing concentrated

solar energy on a tower-mounted heat exchanger (receiver).  This system uses hundreds to thousands of flat

sun-tracking mirrors called heliostats to reflect and concentrate the sun's

energy onto a central receiver tower.

Wind energy means using wind to generate electricity.

A wind turbine is a machine made up of two or three propeller-like blades called the rotor. As the wind blows it spins the rotor. As the rotor

spins the energy of the movement of the propellers gives power to a generator. There are

some magnets and a lot of copper wire inside the generator that make electricity.

Wind Turbines use blades to collect the wind’s kinetic energy. The wind flows over the blades creating lift, like the effect on

airplane wings, which causes them to turn. The blades are connected

to a drive shaft that turns an electric generator to produce

electricity.

With the new wind machines,

Inexhaustible fuel sourceNo pollutionOften an excellent supplement to other renewable sources

Advantages

Very diffuse source means low energy production--large numbers of wind generators (and thus large land areas) are required to produce useful amounts of heat or electricityOnly areas of the world with lots of wind are suitable for wind power generationRelatively expensive to maintain

Disadvantages

\

The word geothermal comes from the Greek words geo (earth)

and therme (heat). So, geothermal energy is heat from within the Earth. We can recover this heat as steam or hot water and use it to heat buildings

or generate electricity.Geothermal energy is a renewable energy source because the heat is continuously produced inside the

Earth.

Geothermal energy is generated in the Earth's core. 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.

Where Geothermal Energy is Found

Naturally occurring large areas of hydrothermal resources are

called geothermal reservoirs. Most geothermal reservoirs are

deep underground with no visible clues showing above ground.

But geothermal energy sometimes finds its way to the surface in

the form of:

ó Volcanoes and fumaroles   (holes where volcanic gases are released)ó Hot springsó Geysers

Use of Geothermal Energy

The three main uses of geothermal energy are:

Direct use and district heating systems use hot

water from springs or reservoirs near the surface.

Electricity generation power plants require water or

steam at very high temperature (300° to 700°F). Geothermal

power plants are generally built where geothermal reservoirs are

located within a mile or two of the surface.

Geothermal heat pumps use stable ground or water

temperatures near the Earth's surface to control building

temperatures above ground.

Advantages

Theoretically inexhaustible energy source No pollution Often an excellent supplement to other

renewable sources Does not require structures such as solar

panels or windmills to collect the energy--can be directly used to heat or produce electricity (thus very cheap)

Disadvantages

Not available in many locations Not much power per vent

It is generated by running water. Dams are

built across a lake or river in a valley to trap water. The water flows

through tunnels and turns the turbines which

make electricity

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, while in a storage system, water is accumulated in reservoirs created by dams, then released as needed to generate electricity. 

Advantages

Inexhaustible fuel source Minimal environmental impact Viable source--relatively useful levels of energy

production Can be used throughout the world

Disadvantages

Smaller models depend on availability of fast flowing streams or rivers

Run-of-the-River plants can impact the mobility of fish and other riverlife. NOTE: Building a fish ladder can lessen this negative aspect of hydroelectric power

Fossil fuels are found within the rocks of the Earth's surface. They are called fossil fuels because they are thought to have been

formed many millions of years ago by geological processes acting on dead animals and plants, just like fossils. 

Coal, oil and natural gas are fossil fuels. Because they took millions of years to form, once they are used up they cannot be

replaced.

What is it?

Oil and gas are chemicals made from molecules containing just carbon and hydrogen. A simple molecule, called methane is the main component of natural gas.

How were they formed?

Gas and oil were formed from the remains of small sea creatures and plants that died and fell to the bottom of seas. Over many millions of years, layers of mud or other sediments built up on top of these dead animals and plants. The pressure from these layers and heat from below the Earth's crust gradually changed the once-living material into oil and natural gas. 

Over time, Gas and oil may move through porous rocks and may even come to the surface. In some places, pockets of oil and gas can be found, because non-porous rocks have trapped them.

AdvantagesThese sources of energy are relatively cheap and most are easy to get and can be used to generate electricity.

Disadvantages When these fuels are burned they produce the gas carbon dioxide, which is a greenhouse gas and is a major contributor to global warming. Transporting oil around the world can produce oil slicks, pollute beaches and harm wildlife.

OIL & GAS

What is it?

Coal mainly consists of carbon atoms that come from plant material from ancient swamp forests. It is a black solid that is soft.

How was it formed?

Millions of years ago, trees and other plants grew rapidly in a tropical climate, and when they died they fell into swamps. The water in the swamps prevented the plant material from decaying completely and peat was formed.

As time passed, layer upon layer of peat built up. The pressure from these layers and heat from below the Earth's crust gradually changed the material into coal.

Coal was formed from the remains of ancient plants.

AdvantagesCoal is relatively cheap, with large deposits left that are reasonably easy to obtain, some coal being close to the surface. It is relatively easy to transport because it is a solid.

DisadvantagesSome sources of coal are deep below the ground, as in the UK. They can be difficult, costly and dangerous to mine. 

Burning coal without first purifying it contributes to global warming, as well as to the production of smog (smoke and fog), which is harmful to health. It is a finite resource and will eventually run out.

 

COAL

What is it?

Nuclear fuel makes use of the radioactivity of some elements. The nucleus in the atom may spontaneously break down to release energy and produce fast-moving particles, atoms of other elements. The fast-moving particles that are ejected can also strike other atoms, causing them to break down. 

How is nuclear fuel made?

Nuclear fuel is made from naturally occurring radioactive materials, such as uranium, found in rocks. These materials are extracted and concentrated. They are formed into 'fuel rods'. 

When placed close together, the fuel rods set off nuclear reactions that generate heat. This heat is used to turn water into steam and generate electricity. 

This fuel is classed as non-renewable, although concentrating the fuel further can recycle some of the 'spent fuel'.

 

 

Radioactive materials are concentrated into fuel pellets and formed into fuel rods in a nuclear reactor. 

AdvantagesNuclear fuel does not produce greenhouse gases, so will not contribute to global warming. There is a relatively long-lasting supply of raw material.

DisadvantagesThe waste remains radioactive for a long time (100+ years). If the reaction is not contained and controlled well, then the nuclear reduction could go out of control, as at Chernobyl in 1986. Radioactive material could then escape into the environment.

NUCLEAR

Fusion means joining smaller nuclei (the plural of nucleus) to make a larger nucleus. The sun uses nuclear fusion of hydrogen atoms into helium atoms. This gives off heat and light and other radiation.

Nuclear energy involves a controlled reaction to split atoms of nuclear fuel,

typically uranium or plutonium, creating two new atoms. When

accomplished on a reasonable scale, this reaction releases an incredible

amount of heat, which can be used to heat water, producing steam and

powering steam turbines, which can then be used to produce electricity.

NUCLEAR FUSION

two types of hydrogen atoms, deuterium and tritium, combine to make a helium atom and an extra particle called a neutron.

Also given off in this fusion reaction is energy!

TWO FORMS OF NUCLEAR ENERGY

The word fission means to split apart.

An atom's nucleus can be split apart. When this is done, a tremendous amount of energy is released. The energy is both heat and light energy. This energy,

when let out slowly, can be harnessed to generate electricity. When it is let out all at once, it can make a tremendous explosion in an atomic bomb.

Below is a cross section of the inside of a typical nuclear power plant.

Inside the reactor of an atomic power plant, uranium atoms are split apart in a controlled chain reaction.

If the reaction is not controlled, you could have an atomic bomb. But in atomic bombs, almost pure pieces of the element Uranium-235 or Plutonium, of a precise mass and shape, must be brought

together and held together, with great force. These conditions are not present in a nuclear reactor.

The reaction also creates radioactive material. This material could hurt people if released, so it is kept in a solid form. The very strong concrete dome in the picture is designed to keep this material

inside if an accident happens.

NUCLEAR Fission

What are the Advantages of Nuclear Energy?

Nuclear reactions release a million times more energy, as compared to hydro or wind energy

no release of greenhouse gases (carbon dioxide, methane, ozone, chlorofluorocarbon) during nuclear reaction

The burning of fossil fuels result in emission of the poisonous carbon dioxide. It is a menace to the environment as well as human life. There is no release of carbon d-oxide at the time of nuclear reaction.

Nuclear reactors make use of uranium as fuel. Fission reaction of a small amount of uranium generates large amount of energy

High amount of energy can be generated from a single nuclear power plant. Also, nuclear fuel is inexpensive and easier to transport.

What are the Disadvantages of Nuclear Energy?

Nuclear energy can be used for production and proliferation of nuclear weapons. Nuclear weapons make use of fission, fusion or combination of both reactions for destructive purposes. They are a major threat to the world as they can cause a large-scale devastation.

The waste produced after fission reactions contains unstable elements and is highly radioactive. It is very dangerous to the environment as well as human health