RENEWABLE ENERGY – TYPES, BENEFITS AND ROLE FOR HEALTHY WORLD

Growing population, increasing energy demands and depleting energy resources along with emission of pollutants associated with conventional energy sources have necessitated search for a novel healthier and reusable energy resource that can meet increasing energy requirements as well as conserve environment. Renewable energy is a solution to these problems.

Renewable energy has gained a lot of importance especially in the current climatic conditions as it can address the issues associated with fossil fuel burning such as greenhouse effect and can solve energy scarcity due to diminishing energy sources.

DEFINITION – The International Energy Agency defines renewable energy as ”energy derived from natural processes that are replenished at a faster rate than they are consumed”.

The term renewable energy has been used interchangably with ”green energy” although both are not entirely same. All green energy sources are renewable but not all renewable energy sources are always green.

Green energy is a type of energy that can be generated by a process and from a source that does not cause any harm to the natural environment. An energy source should fulfill criteria of being both renewable as well as environment friendly to be called as green. For example, a large hydro power plant is renewable but not always green as the infrastructure construction involved in it leads to environmental disruption.

TYPES

• SOLAR ENERGY
• WIND ENERGY
• HYDRO POWER
• GEOTHERMAL ENERGY
• BIOMASS ENERGY

BENEFITS

• Generates little / no greenhouse gases.
• Causes little / no air pollution.
• These are derived from sources that replenish naturally.
• Reduced carbon emission rates so minimizes risk of global warming.
• Decreases dependence on fossil fuel.
• Augments energy security by providing alternative energy sources.
• Conserves natural resources.
• Decreases long term energy expenses.

USES OF RENEWABLE ENERGY

• Source of clean energy for household, businesses and public infrastructure.
• Providing efficient and less polluting transportation such as electric vehicles.
• Aiding in agricultural procedures like solar energy powered irrigation.
• Generating power to run industries.

SOLAR ENERGY

Solar energy uses sun’s light energy to generate electricity.

Light energy is trapped using solar panels made up of small units called solar cells. A solar cell is made of Silicon. In a solar cell, the lower layer is a conducting metal plate which acts as positive electrode. Above it is the silicon layer which is covered by anti reflective coating. On the top of it is the negative electrode.

How does a solar cell work

Silicon in a solar cell is arranged in two layers :

Above is the thin N type silicon layer (facing sunlight).

Below is thick P type silicon layer.

Silicon is a semi conductor. Silicon atoms are surrounded by four electrons that are bound to the four electrons of another silicon atom such that there is no free electron, so no flow of electrons hence no electric current.

N type silicon layer is made by doping phosphorus atoms to silicon. Phosphorus has five electrons, four of which bind with four electrons of silicon and one electron remains free in N layer.

P type silicon layer is made by doping boron atoms to silicon. Boron has three electrons which bind with three electrons of silicon and one hole is created for the one unpaired electron of silicon.

When N and P layer are joined, P-N junction is formed. Some electrons at the N side of P-N junction move to P side to fill some holes. The site where this phenomenon occurs, there is formation of a depletion region.

Within the depletion region, the N side silicon (above) gains positive charge as it loses electrons while the P side (below) becomes negatively charged as it gains electrons. There is formation of an electric field between these charges.

When photons from sunlight strike P-N junction, electrons and holes within depletion region start drifting away. Electrons move to N and holes to P layer because of electric field within the depletion region. As concentration of electrons in N and holes in P region increases, a potential difference develops between them.

When connected to an external circuit, the mobile electrons are collected by thin metal fingers of the negative electrode, flow through external circuit and then get attracted to P side, fill holes and return to metal plate at the back. The flow of electrons creates electric current providing continuous direct current.

A single solar cell produces only 0.5 volt power but when many cells are connected together, power output can be increased.

WIND ENERGY

Turbines mounted on a rotor are used to convert wind energy into electrical energy.

How does wind energy work

A series of blades attached to a rotor converts the kinetic energy of wind into rotational energy. When wind hits over it, the rotational energy is used to turn a generator which creates electricity.

The speed of wind increases higher into the atmosphere so most turbines nowadays are tall enough (over a 100 meter tall).

Wind is capable of generating enormous energy. Wind energy if harnessed well, can yield so much kinetic energy that it can produce 35 times more electricity than what humanity uses everyday.

A wind farm with 200 turbines could meet energy needs of around 150,000 houses for one year!

HYDRO ENERGY

In order to harness the energy of water, dams are constructed.

How is hydropower produced

In a dam, water falls from higher to lower level through a penstock then flows through a turbine. When the blades of turbine rotate, they in turn spin a generator. Generator is composed of many small magnets which on spinning rapidly shed electrons. The electrons then move through wires to generate electricity. The electricity thus produced is fed to transformers and then to powerlines.

Amongst all renewable sources of energy, hydropower accounts for greatest electricity production worldwide.

GEOTHERMAL ENERGY

The heat generated from earth’s crust is used for creating electrical energy.

How does geothermal energy work

The underground water seeping underneath the surface of earth gets heated up by the high temperature inside. This heated water can gush out to the surface at weak points. The steam coming out can be used to spin a turbine which will then turn a generator to produce electricity.

BIOMASS ENERGY

Energy obtained by burning biomass is called biomass energy. Biomass is nothing but organic materials acquired from plants and animals. For example, wood, animal manure, crop.

How does biomass energy work

Plants make glucose by utilizing sunlight in a process called photosynthesis. Plants thus contain chemical energy. On burning, the chemical energy contained in biomass gets converted into heat energy.

Energy can be obtained from biomass by two ways :

• Direct combustion
• Fermentation

In direct combustion, heat generated by burning biomass is fed to a boiler to form steam which can run steam turbines to produce electrical energy.

In fermentation, biomass undergoes fermentation process to produce ethanol which serves as biofuel.

Renewable energy is of immense importance as it is our hope to build a world powered by clean, inexhaustible energy resources. Cutting down use of fossil fuel will not only reduce dependence on diminishing resources but also fight against global warming creating a healthy planet with sustainable future.