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Solar Energy


 Solar energy has been exploited by man since ancient times, using a range of technologies. Solar radiation along with secondary solar resources such as wind and wave power, hydropower and biomass, are considered most available renewable energy on Earth.  



The Sun is the most abundant permanent source of energy for its planet Earth. Solar energy is available both directly as solar radiation and indirectly in the form of power from wind, biomass, hydro, and marine sources. The annual solar radiation reaching the earth is over 7 500 times the world’s annual primary energy consumption of 450 exajoules; it varies from place to place, with some parts of the earth receiving a much greater irradiance than the average annual level of 170 W/m2. However, there is a useable solar resource in virtually all parts of the world, and economically attractive applications are not confined to the sunniest regions.

Earth receives 174 petawati (PW) of solar radiation (heatstroke) entered in the upper atmosphere. About 30% is reflected back into space while the rest is absorbed by clouds, oceans and land masses. The spectrum of sunlight is most prevalent in the Earth's surface in visible and infrared ranges near, with a small part in the near ultraviolet.

The total value of solar energy absorbed by Earth's atmosphere, the oceans and land masses is approximately 3,850,000 exajouli (EJ) per year. In 2002, it was more energy in one hour than was used worldwide in a year. Photosynthesis captures approximately 3000 EJ per year in the biomass.

Applications of solar technology,

There are two basic types of device currently used to capture and utilise solar radiation:

  •  Solar thermal collectors, which are used to heat air, water or other liquids, depending on  

      the application;

· Solar water heater directed towards the sun to maximize the gain.

· Solar hot water systems use solar radiation to heat water. In low geographical latitudes (below 40 degrees) may be provided between 60 and 70% of hot water needed, with temperatures up to 60 ° C, solar water heating systems

· The most common types of solar water heaters are evacuated tube collectors (44%) andcollectors in the form of flat panel glass (34%) generally used for hot water, and collected nevitrate plastic (21%), used in primarily for heating water in swimming pools.

  •   Photovoltaic (PV) collectors, which convert sunlight directly into electricity

                 Sunlight can be

converted into electricity using Potovoltaic (PV), concentrating solar power (PSC), and various experimental technologies. A solar cell or photovoltaic (PV) is a device that converts light into power using the photoelectric effect . PV were used mainly for power supply of small and medium-sized applications, the computer powered by a single solar cell to provide a spectrum independent of photovoltaic-powered homes. For the generation of large scale, PSC as SEGS plants were the norm, but more recently the installation of PV's multi-megawatts is an increasingly common thing.

Solar energy technologies can provide electricity generation by heat engine or photovoltaic means, space heating and cooling of active or passive solar buildings, potable water via distillation and disinfection, lighting, hot water, heat for cooking, heat and process for high temperatures for industrial purposes.   

15 Things about Solar Energy


1. Solar cells provide cost effective solutions to energy problems in places where there is  no mains electricity.

 2. Solar energy is clean, renewable, and sustainable thus helping to protect our                  environment.  It does not pollute our air, does not contribute to global warming, and  decrease of harmful green house gas emissions.

 3. It is generated where it is needed.

4. By not using any fuel, solar energy does not contribute to the cost and problems of the recovery and transportation of fuel or the storage of radioactive waste.

5. Solar energy systems are virtually maintenance free and will last for decades. Once installed, there are no recurring costs. 

6. They operate silently, have no moving parts, do not release offensive smells and do notrequire you to add any fuel. 

7. More solar panels can easily be added in the future when our needs grow. 

8. Solar cells are long lasting sources of energy which can be used almost anywhere. 

9. Solar cells can be installed in a distributed fashion, i.e. they do not need large scale installations.

10. Solar cells can also easily be installed on roofs which means no new space is needed.


1. Most types of solar cell require large areas of land to achieve average efficiency

2. Air pollution and weather can also have a large effect on the efficiency of the cells.

3. The silicon used is also very expensive and the problem of nocturnal down times means solar cells can only ever generate during the daytime.

4. The initial cost is the main disadvantage of installing a solar energy system, largely because of the high cost of the semi-conducting materials used in building one.

5. The efficiency of the system also relies on the location of the sun, although this problem   

can be overcome with the installation of certain components.

Environmental Benefits of Solar    

  •  The Conservation of Fossil Fuels

The conservation of fossil fuels is a simple, but very important benefit that results from the use of photovoltaic (PV) solar power. As more and more businesses, homeowners and governments move to renewable energies such as solar, we conserve fossil fuels and other natural resources that are quickly diminishing. With the expansion of our global economy and rapid growth in highly populated countries, the demand for energy is increasing at an unprecedented rate. Conserving natural resources has never been more important.  

  • Reduction of Air Pollution  

The use of PV solar systems decreases the amount of local air pollution. Around the world, a decrease in the amount of kerosene used for lighting results in a corresponding reduction in the amount of local pollution produced. Globally, rural electrification using PV solar also decreases the amount of electricity needed from small diesel generators. 

There are major environmental impacts attributed to electricity generation from non-renewable fuels. Emissions of atmospheric pollutants (particulates, Sulfur Dioxide (SOx), Nitrogen Oxide (NOx), Carbon Dioxide (CO2), and others) have a serious impact on public health, our water and crops. Additionally, these pollutants negatively impact many delicate ecosystems including forests, fisheries and wetlands.

Offsetting Greenhouse Gases  

Photovoltaic systems produce electric power with no CO2 emissions. Carbon emission offset is calculated at approximately 6 tons of CO2 over twenty years of use for one PV system.

  • Conserving Energy  

Solar electricity for the Third World is an effective energy conservation program because it conserves costly conventional power for urban areas, town market centers, and industrial and commercial uses, leaving decentralized PV-generated power to provide the lighting and basic electrical needs of the majority of the developing world's rural populations.  

  • Reducing the Need for Dry-cell Battery Disposal  

Small dry-cell batteries for flashlights and radios are used throughout the unelectrified world. Most of these batteries are disposable lead-acid cells which are not recycled. Lead from disposed dry-cells leaches into the ground, contaminating the soil and water. Solar rural electrification dramatically decreases the need for disposable dry-cell batteries. Over 12 billion dry-cell batteries were sold worldwide in 1993.  

Solar Power- Energy Benefits/Applications  

Solar energy technologies utilize heat and light from the sun for practical ends. Technologies are being developed that also utilize secondary solar resources such as biomass, wind, hydro, waves, and ocean thermal gradients for our energy requirements. These applications span through the residential, commercial, industrial, agricultural and transportation sectors where solar energy is used to make clean water, produce food, heat and light buildings and generate electricity

  •  Generate electricity using photovoltaic solar cells.  
  • Generate electricity using concentrated solar power.
  •  Heat buildings, directly, through passive solar building design.
  •  Heat foodstuffs, through solar ovens. 
  •  Heat water or air for domestic hot water and space heating needs using solar thermal panels. 
  •  Solar detoxification of contaminated waters or solar distillation 
  •  Heat and cool air through use of solar chimneys 
  •  Solar air conditioning.
  •  Use of passive solar in conjunction with building integrated photovoltaics  

Greenhouse gas savings 

 Solar power is a zero-emission electricity source. One megawatt hour of solar-derived electricity avoids approximately one tonne of CO2.