A solar furnace is a structure used to harness the rays of the sun in order to produce high temperatures, usually for industry. This is achieved using a curved mirror (or an array of mirrors) that acts as a parabolic reflector, concentrating light (Insolation) onto a focal point. The temperature at the focal point may reach 3,000 °C (5,430 °F), and this heat can be used to generate electricity, melt steel, or make hydrogen fuel.
The term "solar furnace" has also evolved to refer to solar concentrator heating systems using parabolic mirrors or heliostats where 538 °C (1,000 °F) is now commonly achieved. The largest solar furnace in the world is at Odeillo in the Pyrenees-Orientales in France, opened in 1970. It employs an array of plane mirrors to gather the rays of light from the sun, reflecting them on to a larger curved mirror. The rays are then focused onto an area the size of a cooking pot and can reach 3,000 °C (5,430 °F).
During the Second Punic War (218 - 202 BCE), the Greek scientist Archimedes is said to have repelled the attacking Roman ships by setting them on fire with a "burning glass" that may have been an array of mirrors. An experiment to test this theory was carried out by a group at the Massachusetts Institute of Technology in 2005. It concluded that although the theory was sound for stationary objects, the mirrors would not likely have been able to concentrate sufficient solar energy to set a ship on fire under battle conditions.
The first modern solar furnace is believed to have been built in France in 1949 by Professor Félix Trombe. It is still in place at Mont Louis, near Odeillo. The Pyrenees were chosen as the site for these furnaces due to sunny weather for up to 300 days a year. 
The solar furnace principle is being used to make inexpensive solar cookers and solar-powered barbecues, and for solar water pasteurization.   A prototype Scheffler reflector is being constructed in India for use in a solar crematorium. This 50 m² reflector will generate temperatures of 700 °C (1,292 °F) and displace 200-300 kg of firewood used per cremation.
It has been suggested that solar furnaces could be used in space to provide energy for manufacturing purposes.
Their reliance on sunny weather is a limiting factor as a source of renewable energy on Earth but could be tied to thermal energy storage systems for energy production through these periods and into the night.