Solar furnace
Encyclopedia
A solar furnace is a structure that captures sunlight
to produce high temperatures, usually for industry. This is done with 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 3500 °C (6,332 °F), and this heat can be used to generate electricity
, melt steel
, make hydrogen fuel
or nanomaterials
.
The term "solar furnace" has also evolved to refer to solar concentrator heating systems using parabolic mirrors or heliostat
s where 538 °C (1,000.4 °F) is now commonly achieved. 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. The rays are then focused onto an area the size of a cooking pot and can reach 3500 °C (6,332 °F), depending on the process installed, for example:
/ Latin
term heliocaminus literally means "solar furnace" and refers to a glass
-enclosed sunroom intentionally designed to become hotter than the outside air temperature.
During the Second Punic War
(218 - 202 BC), 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 now still in place at Mont Louis, near Odeillo. The Pyrenees were chosen as the site because the area experiences clear skies up to 300 days a year.
s and solar-powered barbecue
s, 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.
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
to produce high temperatures, usually for industry. This is done with a curved mirror
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
(or an array of mirrors) that acts as a parabolic reflector
Parabolic reflector
A parabolic reflector is a reflective device used to collect or project energy such as light, sound, or radio waves. Its shape is that of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis...
, concentrating light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
(Insolation
Insolation
Insolation is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter or kilowatt-hours per square meter per day...
) onto a focal point
Focus (optics)
In geometrical optics, a focus, also called an image point, is the point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by...
. The temperature at the focal point may reach 3500 °C (6,332 °F), and this heat can be used to generate electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...
, melt steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, make hydrogen fuel
Hydrogen fuel
An ecologically-friendly fuel which uses electrochemical cells or combusts in internal engines to power vehicles and electric devices. It is also used in the propulsion of spacecraft and can potentially be mass produced and commercialized for passenger vehicles and aircraft.In a flame of pure...
or nanomaterials
Nanomaterials
Nanomaterials is a field that takes a materials science-based approach to nanotechnology. It studies materials with morphological features on the nanoscale, and especially those that have special properties stemming from their nanoscale dimensions...
.
The term "solar furnace" has also evolved to refer to solar concentrator heating systems using parabolic mirrors or heliostat
Heliostat
A heliostat is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating for the sun's apparent motions in the sky. The target may be a physical object, distant from the heliostat, or a direction in space...
s where 538 °C (1,000.4 °F) is now commonly achieved. The largest solar furnace is at Odeillo in the Pyrénées-Orientales
Pyrénées-Orientales
Pyrénées-Orientales is a department of southern France adjacent to the northern Spanish frontier and the Mediterranean Sea. It also surrounds the tiny Spanish enclave of Llívia, and thus has two distinct borders with Spain.- History :...
in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, opened in 1970. It employs an array of plane mirrors to gather sunlight, reflecting it onto a larger curved mirror. The rays are then focused onto an area the size of a cooking pot and can reach 3500 °C (6,332 °F), depending on the process installed, for example:
- about 1000 °C (1,832 °F) for metallic receivers producing hot air for the next generation solar towers as it will be tested at the Themis plantThemis (solar power plant)The THEMIS solar power tower is a research and development centre focused on solar energy. It is located near the village of Targassonne, in the department of Pyrénées-Orientales, south of France, 3 kilometres from the world's largest solar furnace in Odeillo.-Siting of the plant:THEMIS Solar...
with the Pegase project - about 1400 °C (2,552 °F) to produce hydrogen by cracking methane molecules
- up to 2500 °C (4,532 °F) to test materials for extreme environment such as nuclear reactors or space vehicle atmospheric reentry
- up to 3500 °C (6,332 °F) to produce nanomaterialsNanomaterialsNanomaterials is a field that takes a materials science-based approach to nanotechnology. It studies materials with morphological features on the nanoscale, and especially those that have special properties stemming from their nanoscale dimensions...
by solar induced sublimation and controlled cooling, such as carbon nanotubeCarbon nanotubeCarbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material...
s or zinc nanoparticles
History
The ancient GreekAncient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
/ Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
term heliocaminus literally means "solar furnace" and refers to a glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
-enclosed sunroom intentionally designed to become hotter than the outside air temperature.
During the Second Punic War
Second Punic War
The Second Punic War, also referred to as The Hannibalic War and The War Against Hannibal, lasted from 218 to 201 BC and involved combatants in the western and eastern Mediterranean. This was the second major war between Carthage and the Roman Republic, with the participation of the Berbers on...
(218 - 202 BC), the Greek
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
scientist
Scientist
A scientist in a broad sense is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method. The person may be an expert in one or more areas of science. This article focuses on the more restricted use of the word...
Archimedes
Archimedes
Archimedes of Syracuse was a Greek mathematician, physicist, engineer, inventor, and astronomer. Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity. Among his advances in physics are the foundations of hydrostatics, statics and an...
is said to have repelled the attacking Roman
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
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
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
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 now still in place at Mont Louis, near Odeillo. The Pyrenees were chosen as the site because the area experiences clear skies up to 300 days a year.
Modern uses
The solar furnace principle is being used to make inexpensive solar cookerSolar cooker
A solar cooker, or solar oven, is a device which uses the energy of sunlight to heat food or drink to cook it or sterilize it. High-tech versions, for example electric ovens powered by solar cells, are possible, and have some advantages such as being able to work in diffuse light. However at...
s and solar-powered barbecue
Barbecue
Barbecue or barbeque , used chiefly in the United States, Canada, the United Kingdom, New Zealand and Australia is a method and apparatus for cooking meat, poultry and occasionally fish with the heat and hot smoke of a fire, smoking wood, or hot coals of...
s, and for solar water pasteurization
Pasteurization
Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food...
. A prototype Scheffler reflector is being constructed in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
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
Outer space
Outer space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....
to provide energy for manufacturing purposes.
Their reliance on sunny weather is a limiting factor as a source of renewable energy
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...
on Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
but could be tied to thermal energy storage
Thermal energy storage
Thermal energy storage comprises a number of technologies that store thermal energy in energy storage reservoirs for later use. They can be employed to balance energy demand between day time and night time. The thermal reservoir may be maintained at a temperature above or below that of the...
systems for energy production through these periods and into the night.