5 SOLAR ENERGY

 SOLAR ENERGY

Renewable energy is generally defined as energy that comes from resources which are naturally replenished on a human timescale such as sunlight, wind, rain, tides, waves and geothermal heat.

Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor fuels, and rural (off-grid) energy services. 

Renewable energy is derived from natural processes that are replenished constantly. 

In its various forms, it derives directly from the sun, or from heat generated deep within the earth. 

Included in the definition is electricity and heat generated from solar, wind, ocean, hydropower, biomass, geothermal resources, and bio fuels and hydrogen derived from renewable resources.

How Solar Power Plant work? 

The sun is the source of energy that drives the cycle of life and death on earth. 

It is also the energy source that gives us warmth and evaporates water and melts snow. 

The sun is about 150,000,000

km away from the Earth. 

Due to its immense, but finite size, it has an angular diameter of 0.5 degree (32 minutes), as viewed from Earth.

Sun burns continuously via thermonuclear reactions (fusion). 

Inside the sun, radioactive processes releases energy and convection transfers solar energy to its exterior surface. 

Despite the extremely high temperatures needed at the core of the sun, to sustain its thermonuclear reactions, the sun has a black body temperature of 5770 K. 

Consequently, we receive a relatively constant flux density of energy, defined as the Solar Constant. 

Its mean value is 1366 W m-2.

The earth receives 1.6 × 1018 units of energy from the Sun annually, which is 20,000 times the requirement of mankind on the earth. 

Some of the solar energy causes evaporation of water, leading to rains and creation of rivers etc.

Some of itis utilized in photosynthesis which is essential for sustenance of life on earth. 

Man has tried, from time immemorial, to harness this infinite source of energy, but has been able to tap only a negligibly small fraction of this energy.

When light travels from outer space to earth, solar energy is lost because of following reasons:

Scattering

The rays collide with particles present in atmosphere

Absorption 

Because of water vapor there is absorption

Cloud cover

The light rays are diffused because of clouds.

Reflection

When the light rays hit the mountains present on the earth surface there is reflection.

Climate

Latitude of the location, day (time in the year) also affects the amount of solar energy received by the place.

Solar Energy Storage and Applications

Permit solar energy to be captured when insolation is high to be used when the need arises.

Deliver electric load power demand during times when insolation is below normal or nonexistent. Also caters to delivering short power-peaks

Be located closed to the load 

Improve the reliability of solar thermal and solar PV systems

Permit a better match between energy input and load demand output

Some of the important storage methods

Mechanical Energy Storage – pumped storage, compressed air storage, flywheel storage

Chemical Energy Storage – Batteries storage, Hydrogen storage and reversible chemical reactions storage

Electromagnetic energy storage

Electrostatic energy storage

Thermal (heat) energy storage – Sensible heat storage and Latent heat storage

Biological Storage

Thermal (heat) energy storage

Energy storage may be in the form of sensible heat of solids or liquid medium, as heat of fusion in chemical systems or as chemical energy of products in the reversible chemical reaction.

Mechanical energy could be converted to P.E. and stored in elevated fluids Energy can be stored by virtueof latent heat of change of phase of the storage medium. 

Phase-change materials like Glauber's salt have considerably higher thermal energy storage densities

Applications of Solar Energy

The heating and cooling of residential and commercial buildings.

The chemical and biological conversion of organic material to liquid, solid and gaseous fuels

Conversion solar energy to electricity.

Solar distillation, pumping, solar cooking etc

The use of solar energy for generation of electricity is costly as compared to conventional methods. 

However, due to scarcity of fuel, solar energy will certainly find a place in planning the national energy resources.