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 hot topic like the sun is best sparked off with a flurry of some obvious questions - Where does the sun's energy come from? What makes the sun's radiation an important source of energy? How can we harness this 'inexhaustible' energy and make it work for us? Let's explore some important characteristics of the sun's energy and figure out the answers to these.

The sun, which is the source of Solar Energy, is a massive fusion reactor - there is continuous nuclear fusion going on, wherein hydrogen atoms combine to form helium, accompanied by the release of great quantities of heat. This occurs because the sun is very hot; the reason for the high temperatures of the sun is in turn because of these exothermic reactions. The fusion is therefore a 'chain reaction'.

Solar Energy (SE) implies a potential for directly heating or generating electricity by harnessing the energy radiated from the sun. By popular understanding, solar energy comprises all the inexhaustible sources of energy that are continuously provided by the sun - wind, descending water, wave, fossil fuel and the energy stored biologically in trees, crop waste (biomass).

Sunfacts

More energy from the sun falls on the earth in 1 hour than that used by everyone in the world in 1 year.

The sun's nuclear fusion process converts 508 million tons of hydrogen into 504 million tons of helium every second. 

The remaining 4 million tons of matter are converted to energy, making the core temperature of the sun extremely hot.

One ounce of matter converted to energy by fusion could supply all the energy your home and car would need for a year - plus five-thousand other people's homes and cars as well

The use of solar energy, by man, is not new - early civilizations developed technologies to utilize the sun's radiation, the Greeks and Romans started using solar energy atleast 2000 years ago. The Greeks however went a step ahead and were the first to use solar architecture; their cities were built this way as early as 400 BC. Houses were so oriented as to make use of the sun during winter, while obscuring its rays during summer. The Romans further improvised; they developed window glass that allows sunlight to come in, but traps solar heat. They would bring home exotic fruits and vegetables from their conquests in the Middle East and Africa and would try to grow these in their colder climate, using glass covers for greenhouses.

Another interesting point in the history of solar energy's utility is that the first solar water heaters were developed as early as the 18th Century. A French-Swiss scientist began to experiment to see how much heat window glass could actually trap. He built a little box and put several glass tops on it. He found out that the temperature inside could exceed boiling point. This inspired the idea of putting tanks of water inside and painting them black to heat water. The first "solar water heater" was eventually developed, in Maryland, USA.

Renewable energy mine

Going by these facts, there is immense potential in the sun's radiation in providing an alternate source of energy to us - for it is abundant and will be for millions of years to come. As Albert Einstein found out, a very small amount of matter converts to a very large amount of energy. The energy the sun radiates is preferable to other sources of energy because it is abundant; it comes to us at no cost and is available on any clear day. What's more, the sun's radiation is non-polluting, and cannot be cut off or made dearer, unlike other energy sources. It is a clean, safe source of energy and only costs us in terms of the equipment used to harness it.

A disadvantage however, is that solar energy is not always available since it is unobtainable in very cloudy conditions or at night. This hurdle can be overcome by storing the energy. Solar radiation arrives at low intensity and must be concentrated for high temperature (over 250°F / 120°C) applications. Collectors that can concentrate solar radiation are comparatively costly.

Environmentally benign

Solar technologies can be used to provide heat, light, hot water, electricity, and even cooling, for homes, businesses, and industry. It can be harnessed using solar photovoltaic (PV) cells, which convert solar energy directly to electricity, or using solar thermal collectors that heat a working fluid or the interior of a building. Several small commercial solar power plants have been set up to serve some energy markets.

Using this alternate energy source will help conserve valuable natural resources and slow down environmental decay. Replacing the conventional electrical systems by solar technologies means using less electric power generated from fossil fuels that in turn means reduced greenhouse gas and acid rain emissions.

There is more good news for the solar energy market. Growing consumer demand for clean renewable energy, and deregulation of the utilities industry foretell a sunnier future for alternate energies viz. the solar, wind, geothermal, biomass, and small-scale hydroelectric sources.