Solar energy is the energy received by the earth from the sun that is converted into thermal or electrical energy.
Solar energy influences Earth’s climate and weather and sustains life. Although solar energy only provides 0.15% of the world’s power, experts believe that sunlight has the potential to supply 5000 time as much energy as the world currently consumes.
Broadly speaking, solar energy is a term for describing a range of methods for obtaining energy from the sun. For instance, wind, biomass and hydropower are all forms of solar energy.
Wind develops through lows and highs in temperature. Wind drives waves. Rainfall, created by sun-warmed evaporated water feeds the rivers that are sources of hydro power. Fossil fuels are also forms of stored solar energy. Coal, oil and gas formed hundreds of millions of years ago from decomposed plant matter. Plant matter that grew by aid of the sun.
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Important Applications of Solar Energy in Modern Days
Some of the important applications of solar energy are summarized below:
(i) Space cooling and heating through solar architecture,
(ii) Potable water via distillation and disinfection,
(iii) Solar cooking,
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(iv) Solar hot water,
(v) Day lighting,
(vi) High temperature process heat for industrial purposes,
(vii) Solar air-conditioning,
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(viii) Solar desalination,
(ix) Solar electricity – photovoltaic,
(x) Solar electricity – thermal,
(xi) Solar vehicles,
(xii) Solar chimney
Uses of Solar Energy
The use of solar energy for space heating of buildings :
The architecturial design of the buildings helps in their passive space heating using solar Energy. Following strategies are useful for passive space heating:
(a) Provide large south-facing windows
(b) Provide an entire wall of double-glazed windows.
(c) Provide a heavy dark-coloured south facing wall behind a layer of glass, with room air circulating by convection between the wall and the glass.
(d) Provide a flat roof covered by a pond of water. Provision should be there for an insulating screen cover for cooling requirement in summer.
Note that no mechanical equipment is needed for passive solar heating.
An active technology of solar space heating needs a collector to absorb and collect solar radiation. Subsequently fans or pumps are used to circulate the needed air or heat absorbing fluid (generally water). Water systems are more common than air systems as they offer better heat exchanger performance.
The use of solar energy for the generation of electricity-photovoltaics :
Photovoltaics (PVs) are arrays of cells containing a solar photovoltaic material that converts solar radiation into direct current electricity. Solar cells produce direct current (DC) electricity from sunlight, which can be used to power bulb/equipment or to recharge a battery, however, for grid connected power generation; an inverter is required to convert the DC to alternating current (AC)
A number of solar cells electrically connected to each other and mounted in a support structure or frame is called a photovoltaic module. Multiple modules can be wired together to form an array. In general, the larger the area of a module or array, the more electricity that will be produced
When the n-type and p-type semiconductors are sandwiched together, and irradiated with sunlight, the excess electrons in the n-type material flow to the -type, and the holes thereby
Vacated during this process flow to the n-type through this hole and electron flow, the two semiconductors act as a cell, creating an electric field at the surface where they meet (known as p-n junction). It is this field that causes the electrons to jump from the semiconductor out toward the surface and make them available for the electrical circuit
Advantages of solar Photovoltaics
(i) Easy installation and maintenance
(ii) Pollution free
(iii) Long life
(iv) Viable for remote and isolated areas, forest, hilly, desert regions.
Disadvantages of solar Photovoltaics:
The high initial cost especially of the silicon wafer is the major constraint in the widespread use of solar cells.
Applications of photovoltaic cells and solar panels :
Photovoltaic cells are used in watches, pocket calculators, toys. Solar panels are useful to light up a house, run an irrigation pump, operate traffic lights, etc.
Solar water heater :
Solar water heater consists of a flat-plate collector, with a black bottom, a glass top, and water tubes in between. The collector is placed at a suitable angle to catch sun’s energy. The black bottom of the collector gets hot by absorbing solar radiation. The heat warms up the water in the tubes. The insulated storage tank is placed above the collector, the cool water moves down into the tubes and the water moves into the tank by natural convection.
As the energy is coming from the sun, utility bills are much lower and within few years the installation cost is recovered.