A solar cell is the most well-known device for converting sunlight into electricity. By a complex series of molecular movements, photons of light are converted to electrons. Traditional solar panels were typically made of silicon, but these units were heavy, inefficient and expensive to manufacture.
As of 2010, inventors were studying new methods of manufacturing solar cells. Researchers at the California Institute of Technology have developed a new type of solar cell with reconfigured silicon molecules and lenses in front of the panels, resulting in greater efficiency. While researching ways to reduce the cost of manufacturing traditional solar cells, researchers at the University of Texas announced in 2009 the development of a conductive paint, allowing solar cells to be printed much like newspaper on high speed printing presses. The process offers the potential for cheap, mass-produced solar cells.
The sun not only puts out light but also radiation. This radiation takes the form of heat energy and electromagnetic radio waves. In the early years of the 20th century, inventor Nikola Tesla invented the radiation collector to collect the electromagnetic waves. This device does not convert light energy; it converts electromagnetic waves into electricity. The simple device uses a flat metal plate exposed to the sun. A wire connects the plate to one terminal of a capacitor, which stores the electrical charge. When the sun's electromagnetic waves hits the metal plate, electricity is produced. Electricity was then "drained off" from the capacitor terminals. Given the advances in capacitor technology since Tesla's era, researchers are taking another look at his invention. Tesla never specified exact sizes for the metal plate or the capacitor, so much research needs to be done.
Developed by Dr. Robert Stirling in 1816, the Stirling engine is a type of piston engine similar to a gasoline engine, but it uses heated and cooled air instead of gasoline. When air is heated, it expands. This expansion is used to drive a piston down a cylinder, and by a crank mechanism, turns a shaft. In April of 2010, a group of student researchers at Florida International university reported on a system that used solar collectors to heat the air to drive the engine. The engine is connected to a generator to produce electricity.