Solar Energy

Solar energy is energy from the Sun in the form of heat and light. This energy resource drives the climate and weather and supports virtually all life on Earth. Heat and light from the Sun, along with secondary solar resources such as wind and wave power, hydroelectricity and biomass, account for over 99.9% of the available flow of renewable energy on Earth.

Solar energy technologies harness the Sun's heat and light for practical ends. These technologies date from the time of the early Greeks, Native Americans and Chinese, who oriented their buildings toward the Sun to provide light and warmth. Modern approaches to passive design and sustainable architecture use computer modeling to tie together solar lighting, heating, and ventilation systems within an integrated solar design package.

Sunlight can be used directly to improve agricultural yields, harvest salt, produce potable water, and cook food. Concentrating technologies can magnify the rays of the Sun for high temperature material testing, metal smelting, and lime production. Sunlight may also be converted into electricity, hydrogen and methanol, or stored in eutectic and molten salts.

Solar power is used synonymously with solar energy or more specifically to refer to the conversion of sunlight into electricity. This can be done with photovoltaics, concentrating solar thermal devices and various experimental technologies.

Solar vehicles
Development of a solar powered car has been an engineering goal since the 1980s. The center of this development is the World Solar Challenge, a biannual solar-powered car race in which teams from universities and enterprises compete over 3,021 kilometres (1,877 mi) across central Australia from Darwin to Adelaide. In 1987, when it was founded, the winner's average speed was 67 kilometres per hour (42 mph). The 2007 race included a new challenge class using cars with an upright seating position and which, with little modification, could be a practical proposition for sustainable transport. The winning car averaged 90.87 kilometres per hour (56.46 mph). The North American Solar Challenge (formerly Sunrayce USA) and the planned South African Solar Challenge are comparable competitions that reflect an international interest in the engineering and development of solar powered vehicles. In 1975, the first practical solar boat was constructed in England. By 1995, passenger boats incorporating PV panels began appearing and are now used extensively. In 1996, Kenichi Horie made the first solar powered crossing of the Pacific Ocean, and the sun21 catamaran made the first solar powered crossing of the Atlantic Ocean in the winter of 2006/2007. Plans to circumnavigate the globe in 2009 are indicative of the progress solar boats have made.

In 1974, the unmanned Sunrise II inaugurated the era of solar flight. In 1980, the Gossamer Penguin made the first piloted flights powered solely by photovoltaics. This was quickly followed by the Solar Challenger which demonstrated a more airworthy design with its crossing of the English Channel in July, 1981. Developments then turned back to unmanned aerial vehicles with the Pathfinder (1997), Pathfinder Plus (1998) and Centurion (1998) each building on one another. These designs culminated in the Helios which set the altitude record for a non-rocket-propelled aircraft of 29,524 metres (96,860 ft) in 2001. The Zephyr, developed by BAE Systems, is the latest in a line of record breaking solar aircraft. This aircraft made a record setting 54 hours duration flight in 2007, and month long duration flights are envisioned by 2010.

A solar balloon is a black balloon that is filled with ordinary air. As sunlight shines on the balloon, the air inside is heated and expands, causing an upward buoyancy force, much like an artificially-heated hot air balloon. Some solar balloons are large enough for human flight, but usage is limited to the toy market as the surface-area to payload-weight ratio is rather high.

Solar sails are a proposed form of spacecraft propulsion using large membrane mirrors. Radiation pressure is small and decreases by the square of the distance from the Sun, but unlike rockets, solar sails require no fuel. Although the thrust is small compared to rockets, it continues as long as the Sun shines and the sail is deployed and in the frictionless vacuum of space significant speeds can eventually be achieved.

Some contents courtesy of Wikipedia