Solar vehicles

Development of a practical 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 km (1,877 mi) across central Australia from Darwin to Adelaide. In 1987, when it was founded, the winner's average speed was 67 km/h (42 mph)[76] 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 km/h (56.46 mph).

Helios UAV in flight

















Helios, named for the Greek sun god, was a prototype solar-powered unmanned aircraft. AeroVironment, Inc. developed the vehicle under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. On 13 August, 2001, it set an unofficial world record for sustained altitude by a winged aircraft. It sustained flight above 29,250 m (95,965 ft) for 40 minutes and reached 29,524 m (96,864 ft) altitude in the process.

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.

The first practical solar boat was constructed in 1975 in England.[78] By 1995, solar passenger boats began appearing and are now used extensively.[79] The first crossing of the Atlantic Ocean by a solar-powered boat was in the winter of 2006/2007 by the catamaran sun21.

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.