A solar furnace is a structure that uses concentrated solar power to produce high temperatures, usually for industry.

Parabolic mirror A parabolic (or paraboloid or paraboloidal) reflector (or dish or mirror) is a Mirror, reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a circular paraboloid, that is, the surface ge ...

s or heliostats concentrate

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

( Insolation) onto a focal point. The temperature at the focal point may reach , and this heat can be used to generate

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describ ...

, melt steel, make

hydrogen fuel Hydrogen fuel refers to hydrogen which is burned as fuel with oxygen. It is zero-carbon, provided that it is created in a process that does not involve carbon. It can be used in fuel cells or internal combustion engines (see HICEV). Regarding hydr ...

nanomaterials * Nanomaterials describe, in principle, materials of which a single unit is sized (in at least one dimension) between 1 and 100 nm (the usual definition of nanoscale). Nanomaterials research takes a materials science-based approach to na ...

. The largest solar furnace is at Odeillo in the Pyrénées-Orientales in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

, opened in 1970. It employs an array of plane mirrors to gather sunlight, reflecting it onto a larger curved mirror.

History

The

ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

term ''heliocaminus'' literally means "solar furnace" and refers to a

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...

-enclosed

sunroom A sunroom, also frequently called a solarium (and sometimes a "Florida room", "garden conservatory", "garden room", " patio room", "sun parlor", "sun porch", "three season room" or "winter garden"), is a room that permits abundant daylight and ...

intentionally designed to become hotter than the outside air temperature. During the Second Punic War (218–202 BC), the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

scientist A scientist is a person who conducts scientific research to advance knowledge in an area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engaged in the philosoph ...

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. There have been several real-world tests to evaluate the validity of this myth over the centuries, including a test by Comte de Buffon (circa 1747), documented in the paper titled "Invention De Miroirs Ardens, Pour Brusler a Une Grande Distance", and an experiment by John Scott, which was documented in an 1867 paper.Greek scientist Dr. Ioannis Sakkas, curious about whether Archimedes could really have used a "burning glass" to destroy the Roman fleet in 212 BC, lined up nearly 60 Greek sailors, each holding an oblong mirror tipped to catch the sun’s rays and direct them at a wooden ship 160 feet away. The ship caught fire at once. Sakkas said after the experiment there was no doubt in his mind the great inventor could have used bronze mirrors to scuttle the Romans. However, accounting for battle conditions makes such a weapon impractical, with modern tests refuting such claims. An experiment was carried out by a group at the

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...

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. Similar experiments were conducted on the popular science-based TV show '' MythBusters'' in 2004, 2006, and 2010, arriving at similar results based on the premise of the controversial myth. However, an episode of '' Richard Hammond's Engineering Connections'' relating to the Keck Observatory (whose reflector glass is based on the Archimedes' Mirror) did successfully use a much smaller curved mirror to burn a wooden model, although the scaled-down model was not made of the same quality of materials as in the ''MythBusters'' effort. 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. 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.

Uses

The rays are focused onto an area the size of a cooking pot and can reach , depending on the process installed, for example: * about 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 * about to produce hydrogen by cracking methane molecules * up to to test materials for extreme environment such as nuclear reactors or space vehicle atmospheric reentry * up to to produce

by solar induced sublimation and controlled cooling, such as carbon nanotubes or zinc nanoparticles It has been suggested that solar furnaces could be used in

space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually cons ...

to provide energy for manufacturing purposes. Their reliance on sunny weather is a limiting factor as a source of renewable energy on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

but could be tied to

thermal energy storage Thermal energy storage (TES) is achieved with widely different technologies. Depending on the specific technology, it allows excess thermal energy to be stored and used hours, days, months later, at scales ranging from the individual process, ...

systems for energy production through these periods and into the night.

Smaller-scale devices

The solar furnace principle is being used to make inexpensive

solar cooker A solar cooker is a device which uses the energy of direct sunlight to heat, cook or pasteurize drink and other food materials. Many solar cookers currently in use are relatively inexpensive, low-tech devices, although some are as powerful or as ...

s and solar-powered barbecues, and for solar water pasteurization. A prototype Scheffler reflector is being constructed in

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

for use in a solar

crematorium A crematorium or crematory is a venue for the cremation of the dead. Modern crematoria contain at least one cremator (also known as a crematory, retort or cremation chamber), a purpose-built furnace. In some countries a crematorium can also b ...

. This 50 m² reflector will generate temperatures of and displace 200–300 kg of firewood used per cremation.

References

External links

Article about the Odeillo and Mont Louis solar furnacesHochflussdichte Sonnenofen des DLR, KölnBBC News article about the solar power station serving Seville, Spain
{{Solar energy Industrial furnaces Solar thermal energy Heaters

History

Uses

Smaller-scale devices

See also

References

External links