Heated glass is a

resistance heater Electric heating is a process in which electrical energy is converted directly to heat energy at around 100% efficiency, using rather cheap devices. Common applications include space heating, cooking, water heating and industrial processes. An ...

created when a transparent, electrically conductive coating is applied to

float glass Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin, although lead and other various low- melting-point alloys were used in the past. This method gives the sheet uniform thickness and very flat sur ...

and then subjected to an

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...

. The

in the coating creates

heat energy In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...

, which warms the glass until the glass radiates heat.

Design

The manufacturing process begins with the application of a microscopic

Tin dioxide Tin(IV) oxide, also known as stannic oxide, is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin. With many other names, this oxide of tin is an important material in tin ...

coating to a pane of float glass. This coating is transparent and conducts electricity. Then, two

busbars In electric power distribution, a busbar (also bus bar) is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution. They are also used to connect high volt ...

are applied to the glass as follows: the busbars must be parallel and applied to opposing edges on the same side of the glass pane. The surface of the glass between the busbars must be flat. An electric current flows across the tin(II) oxide coating from one busbar to the other. The

electrical resistance The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels ...

of the coating produces heat energy, which radiates from the glass. The busbars are connected to a power control unit that regulates the flow of

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 described ...

and thus the

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

of the glass. In modern architectural projects the heated glass is completely translucent. This technology uses a special metallic coating on the surface of the glass invisible to the naked human eye. A pane of heated glass can achieve temperatures up to 350 degrees Fahrenheit (177 degrees Celsius). The standard desirable temperature range in buildings is between 104 and 113 degrees Fahrenheit (40 to 44 degrees Celsius). For industrial purposes higher temperatures may be warranted.

Use

The first heated glass was created in 1931 by Protes Glass Company, offered for cars. Their product was not a success. Heated glass was first used on a wide scale in

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

in Naval Ships and on to aircraft windshields from frosting over in cold weather It is still used in both for this purpose. Heated glass has been used in architectural applications for the past 30 years to prevent

condensation Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...

and provide radiant heat. Condensation in buildings can have serious consequences to health and property values. Heated or radiant glass is generally an enhanced standard two pane insulated glass window using various bus bar technologies to convey the electric current to heat the glass. Some technologies are patented and permit larger glass areas to be heated than others. In One university study shows that this heated glass technology is more efficient than other electric heating and can be more efficient than natural gas heating. Some environmentalists dispute the idea that this is an efficient heating system because even high e-value windows are poor insulators compared to insulated walls, and they believe heating window ejects much of the radiant heat outside. Another criticism is that this type of heating may encourage the use of larger windows in a house, making them less energy efficient. This technology has evolved since the late 1950s where it firstly evolved to be used for melting snow on glass roofs and was then effectively inverted and used as the heat source inside the building. A common commercial use of heated glass is to prevent frost from forming on the glass doors of supermarket freezers. In addition, display cases (such as in convenience stores and delis) use heated glass shelves to keep cooked food items from cooling.
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References

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External links

Heated Glass
Glass engineering and science Glass types Windows Glass applications Heating

Design

Use

See also

References

Further reading

External links