Solar furnace

For the cooking apparatus, see Solar cooker. For electricity generation, see Solar power tower.

A solar furnace is a structure that uses concentrated solar power to produce high temperatures, usually for industry. Parabolic mirrors or heliostats concentrate light (Insolation) onto a focal point. The temperature at the focal point may reach 3,500 °C (6,330 °F), and this heat can be used to generate electricity, melt steel, make hydrogen fuel or nanomaterials.

The solar furnace at Odeillo in the Pyrénées-Orientales in France can reach temperatures of 3,500 °C (6,330 °F).

The largest solar furnace is at Odeillo in the Pyrénées-Orientales in France, opened in 1970. It employs an array of plane mirrors to gather sunlight, reflecting it onto a larger curved mirror.

History

The ancient Greek / Latin term heliocaminus means "solar furnace" and refers to a glass-enclosed sunroom intentionally designed to become hotter than the outside air temperature.^[1]

Legendary accounts of the Siege of Syracuse (213–212 BC) tell of Archimedes' heat ray, a set of burnished brass mirrors or burning glasses supposedly used to ignite attacking ships, though modern historians doubt its veracity.

On 24 September 1901, Knut C. Wideen was granted a patent for a "System for collecting and utilizing solar heat", which included a solar furnace.^[2]

The first modern solar furnace is believed to have been built in France in 1949 by Professor Félix Trombe. The device, the Mont-Louis Solar Furnace is still in place at Mont-Louis. The Pyrenees were chosen as the site because the area experiences clear skies up to 300 days a year.^[3]

The Odeillo Solar Furnace is a larger and more powerful solar furnace. It was built between 1962 and 1968, and started operating in 1969. It's currently the most powerful, based on an achievable temperature of 3500 °C.

The Solar Furnace of Uzbekistan was built in Uzbekistan and opened in 1981 as a part of a Soviet Union "Sun" Complex Research Facility, being the world largest concentrator.^[4]

Uses

The rays are focused onto an area the size of a cooking pot and can reach 4,000 °C (7,230 °F), depending on the process installed; for example:

• about 1,000 °C (1,830 °F) for metallic receivers producing hot air for the next-generation solar towers as it will be tested at the Themis plant with the Pegase project^[5]
• about 1,400 °C (2,550 °F) to produce hydrogen by cracking methane molecules^[6]
• up to 2,500 °C (4,530 °F) to test materials for extreme environment such as nuclear reactors or space vehicle atmospheric reentry
• up to 3,500 °C (6,330 °F) to produce nanomaterials by solar induced sublimation and controlled cooling, such as carbon nanotubes^[7] or zinc nanoparticles^[8]

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.

Smaller-scale devices

Paella being cooked with a solar cooker

The solar furnace principle is being used to make inexpensive solar cookers and solar-powered barbecues, and for solar water pasteurization.^[9][10] 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 save 200–300 kg of firewood used per cremation.^[11]

See also

• Solar power tower
• Solar thermal energy
• Solar thermal collector
• Solar furnace of Uzbekistan