Solar energy is radiant light and heat from the Sun. It is harnessed using a range of ever evolving technologies such as solar heating and solar thermal energy. Solar architecture and molten salt power plants along with artificial photosynthesis are some other upcoming areas of harnessing solar energy in which research is being done. Solar energy is an essential source of renewable energy. Its technologies are broadly characterized as either passive solar or active solar depending on how they capture and distribute solar energy or convert it into solar power. Active solar techniques include the use of photovoltaic systems and solar water heating to harness the energy. Passive solar techniques include orienting a building to the Sun selecting materials with favourable thermal mass or light dispersing properties and designing spaces that naturally circulate air. The large magnitude of solar energy available makes it a highly appealing source of electricity. Few years later the International Energy Agency said that the development of affordable and inexhaustible plus clean solar energy technologies will have huge, longer term benefits. It will increase energy security of countries through reliance on an indigenous and inexhaustible as well as mostly import independent resource. It will enhance sustainability which will reduce pollution and lower the costs of mitigating global warming. Furthermore, it will keep fossil fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments. They must be wisely spent and need to be widely shared. Approximately a third of the radiation from sun is reflected back to space while the rest is absorbed by clouds and oceans or land masses. The spectrum of solar light at the surface of the earth is mostly spread across the visible and near infrared ranges with a small part in the near ultraviolet. Warm air containing evaporated water from the oceans rises above causing atmospheric circulation or convection. When the air reaches a high altitude where the temperature is low water vapor condenses into clouds. These clouds then blown by wind currents rain onto the surface of the earth completing the water cycle. The latent heat of water condensation amplifies convection producing atmospheric phenomena such as wind and cyclones or anticyclones. Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of fourteen degree Celsius. By the process of photosynthesis green plants convert solar energy into chemically stored energy which produces food and wood. It also produces the biomass from which fossil fuels are derived. The total solar energy absorbed by earth atmosphere and surface including oceans and land masses is approximately three million exajoules per year. This was more energy in one hour than the world used in one year. Photosynthesis captures approximately three thousand exajoules per year in biomass. The amount of solar energy reaching the surface of the planet is so vast that in one year it is about twice as much as will ever be obtained from all of the non renewable resources of the earth. Such as coal and petroleum or natural gas and mined uranium combined. The potential of solar energy that could be used by humans differs from the amount of solar energy present near the surface of the planet due to various other factors.