What is a Solar Furnace?

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A solar furnace is a structure that captures sunlight to produce very high temperatures, used for industrial purposes. This is done with a curved mirror (or an array of mirrors) that acts as a parabolic reflector (device used to collect or project energy such as light, sound, or radio waves), concentrating light 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, and make hydrogen fuel or nano materials. The term "solar furnace" has also expanded in its scope 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 is at Odeillo in France, opened in 1970. Concentrated solar powers (CSP) are systems that use lenses or mirrors to concentrate a large area of sunlight, or solar thermal energy, onto a small area.

What is the Historical Background of Solar Furnace?

During the Second Punic War (218 - 202 BC), which encompassed combatants in the western and eastern Mediterranean, the Greek scientist, Archimedes, is thought to have repelled the attacking Roman ships by setting them on fire with a "burning glass" that may have been an array of mirrors. A burning lens is a large convex lens that can concentrate the sun's rays onto a small area. An experiment to test this theory was performed by a group at the Massachusetts Institute of Technology (MIT), a private research university located in Cambridge, Massachusetts, 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 due to clear skies up to 300 days a year.

What is the Operation Principle of a Solar Furnace?

The operation principle of a solar furnace is quite simple entailing the use of two mirrors. The mirrors are angled at a focal point, which increases the intensity of sunlight to approximately threefold. The motive for this is the fact that the focal point is the concentrated light from the sun as well as the two mirrors. When the number of mirrors is increased to ten, then it is possible to achieve energy and heat levels where one can actually boil water and cook food. The amount of energy and efficiency of the solar furnace relay completely on how accurate the mirrors are focused on one point.

How does a home Solar Furnace Work?

The Solar Furnace system is a turn key solar heating, ventilation and domestic hot water solution. It can supply whole house heating, ventilation and hot water supply for a home from 0-3000 sq. ft. The mechanism of the system involves providing fresh solar air ventilation to an integrated HRV (energy efficient motor) inside the solar hydronics furnace with solar hot water and an on demand tank less hot water system. This efficient arrangement distributes effective solar heating and natural gas or propane whole home heating system. Radiant floor and swimming options can be added to the system as well.

What is the temperature ranges for various purposes?

The rays are focused onto an area the size of a cooking pot and can reach 3,500 °C (6,330 °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. THEMIS solar power tower is a research and development centre focused on solar energy.
• About 1,400 °C (2,550 °F) to produce hydrogen by cracking methane molecules.
• 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 nano materials by solar induced sublimation (transition of a substance from the solid phase to the gas phase) and controlled cooling, such as carbon nano tubes or zinc nano particles.

What are some modern uses of Solar Furnace?

• The solar furnace principle is being used to make inexpensive solar cookers and solar-powered barbecues, and for solar water 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.
• 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 proposed 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. Thermal energy storage comprises a number of technologies that store thermal energy in energy storage reservoirs for later use.
• The Solar Furnace system can reduce the heating and electricity bills. It can provide savings from 20% up to 60%.

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