Solar Energy

Renewable energy sources Mass production of electricity from renewable energy flows requires technology that harnesses the power of natural phenomena such as sunlight, wind, tides and geothermal heat. Each of these sources has unique characteristics which influence how and where they are used.

The majority of renewable energy technologies are directly or indirectly powered by the Sun. The Earth-Atmosphere system is in equilibrium such that heat radiation into space is equal to incoming solar radiation, the resulting level of energy within the Earth-Atmosphere system can roughly be described as the Earth's "climate". The hydrosphere (water) absorbs a major fraction of the incoming radiation. Most radiation is absorbed at low latitudes around the equator, but this energy is dissipated around the globe in the form of winds and ocean currents. Wave motion may play a role in the process of transferring mechanical energy between the atmosphere and the ocean through wind stress (Sorensen, 2004). Solar energy is also responsible for the distribution of precipitation which is tapped by hydroelectric projects, and for the growth of plants used to create biofuels. In this context, "solar energy" refers to energy that is collected from sunlight. However, most fossil and renewable energy sources are ultimately derived from "solar energy," so some ascribe much broader meanings to the term.

Solar energy can be applied in many ways, including to : 1. Generate electricity using photovoltaic solar cells. 2. Generate electricity using concentrated solar power. 3. Generate electricity by heating trapped air which rotates turbines in a Solar updraft tower. 4. Heat buildings, directly. Careful positioning of windows and use of brises soleil can maximise inflow of light at the times it is most needed, heating the building while preventing overheating during midday and summer. 5. Heat foodstuffs, through solar ovens. 6. Heat water or air for domestic hot water and space heating needs using solar-thermal panels. 7. Heat and cool air through use of solar chimneys. 8. Generate electricity using Space Solar Power Satellite in geostationary orbit and beam it down via microwaves.

The sun does not provide constant energy to any spot on the Earth, so its uninterrupted use on Earth requires a means for energy storage. This is typically accomplished by battery storage. However, battery storage implies energy losses. Some homeowners use a grid-connected solar system that feeds energy to the grid during the day and draw energy from the grid at night; this way no energy is expended for storage. Batteries provide direct current (DC), whereas most household appliances run off alternating current (AC). Conversion from DC to AC leads to some energy loss.

Advantages from solar energy sources include the inexhaustible supply of energy and zero emissions of greenhouse gas and air pollutants. Shortcomings include, depending on application : 1. Economic competitiveness with conventional energy conversion 2. Intermittency; it is not available at night or during heavy cloud cover. 3. For photovoltaics (solar-electric), the current generated is only of DC type, and must be converted if transmission over the standard AC grid is needed. ( Original Source : Wikipedia Encyclopedia, Photo Source : Google Images )