A candle is an ignitable wick embedded in wax, or another flammable solid substance such as tallow, that provides light, in some cases, a fragrance. A candle can provide heat, or be used as a method of keeping time; the candle can be used during the event of a power outage to provide light. A person who makes candles is traditionally known as a chandler. Various devices have been invented to hold candles, from simple tabletop candlesticks known as candle holders, to elaborate chandeliers. For a candle to burn, a heat source is used to light the candle's wick, which melts and vaporizes a small amount of fuel. Once vaporized, the fuel combines with oxygen in the atmosphere to form a constant flame; this flame provides sufficient heat to keep the candle burning via a self-sustaining chain of events: the heat of the flame melts the top of the mass of solid fuel. As the solid fuel is melted and burned, the candle becomes shorter. Portions of the wick that are not emitting vaporized fuel are consumed in the flame.
The incineration of the wick limits the exposed length of the wick, thus maintaining a constant burning temperature and rate of fuel consumption. Some wicks require regular trimming with scissors to about one-quarter inch, to promote slower, steady burning, to prevent smoking. Special candle-scissors called "snuffers" were produced for this purpose in the 20th century and were combined with an extinguisher. In modern candles, the wick is constructed; this ensures that the end of the wick gets oxygen and is consumed by fire—a self-trimming wick. The word candle comes from Middle English candel, from Old English and from Anglo-Norman candele, both from Latin candēla, from candēre, to shine. Prior to the candle, people used oil lamps. Liquid oil lamps had a tendency to spill, the wick had to be advanced by hand. Romans began making true dipped candles from tallow, beginning around 500 BC. European candles of antiquity were made from various forms of natural fat and wax. In Ancient Rome, candles were made of tallow due to the prohibitive cost of beeswax.
It is possible that they existed in Ancient Greece, but imprecise terminology makes it difficult to determine. The earliest surviving candles originated in Han China around 200 BC; these early Chinese candles were made from whale fat. During the Middle Ages, tallow candles were most used. By the 13th century, candle making had become a guild craft in France; the candle makers went from house to house making candles from the kitchen fats saved for that purpose, or made and sold their own candles from small candle shops. Beeswax, compared to animal-based tallow, burned cleanly, without smoky flame. Beeswax candles were expensive, few people could afford to burn them in their homes in medieval Europe. However, they were used for church ceremonies. In the 18th and 19th centuries, spermaceti, a waxy substance produced by the sperm whale, was used to produce a superior candle that burned longer and gave off no offensive smell. In the 18th century, colza oil and rapeseed oil came into use as much cheaper substitutes.
The manufacture of candles became an industrialized mass market in the mid 19th century. In 1834, Joseph Morgan, a pewterer from Manchester, patented a machine that revolutionised candle making, it allowed for continuous production of molded candles by using a cylinder with a moveable piston to eject candles as they solidified. This more efficient mechanized production produced about 1,500 candles per hour; this allowed candles to be an affordable commodity for the masses. Candlemakers began to fashion wicks out of braided strands of cotton; this technique makes wicks curl over as they burn, maintaining the height of the wick and therefore the flame. Because much of the excess wick is incinerated, these are referred to as "self-trimming" or "self-consuming" wicks. In the mid-1850s, James Young succeeded in distilling paraffin wax from coal and oil shales at Bathgate in West Lothian and developed a commercially viable method of production. Paraffin could be used to make inexpensive candles of high quality.
It was a bluish-white wax, which left no unpleasant odor, unlike tallow candles. By the end of the 19th century candles were made from stearic acid. By the late 19th century, Price's Candles, based in London, was the largest candle manufacturer in the world. Founded by William Wilson in 1830, the company pioneered the implementation of the technique of steam distillation, was thus able to manufacture candles from a wide range of raw materials, including skin fat, bone fat, fish oil and industrial greases. Despite advances in candle making, the candle industry declined upon the introduction of superior methods of lighting, including kerosene and lamps and the 1879 invention of the incandescent light bulb. From this point on, candles came to be marketed as more of a decorative item. Before the invention of electric lighting and oil lamps were used for illumination. In areas without electricity, they are still used routinely; until the 20th century, candles were more common in northern Europe. In southern Europe and the Mediterranean, oil lamps predominated.
In the developed world today, candles are used for their aesthetic value and scent to set a soft, warm, or romantic ambiance, for emergency lighting during electrical power failures, and
Compact fluorescent lamp
A compact fluorescent lamp called compact fluorescent light, energy-saving light, compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb. The lamps use a tube, curved or folded to fit into the space of an incandescent bulb, a compact electronic ballast in the base of the lamp. Compared to general-service incandescent lamps giving the same amount of visible light, CFLs use one-fifth to one-third the electric power, last eight to fifteen times longer. A CFL has a higher purchase price than an incandescent lamp, but can save over five times its purchase price in electricity costs over the lamp's lifetime. Like all fluorescent lamps, CFLs contain toxic mercury. In many countries, governments have banned the disposal of CFLs together with regular garbage; these countries have established special collection systems for other hazardous waste. The principle of operation remains the same as in other fluorescent lighting: electrons that are bound to mercury atoms are excited to states where they will radiate ultraviolet light as they return to a lower energy level.
CFLs radiate a spectral power distribution, different from that of incandescent lamps. Improved phosphor formulations have improved the perceived color of the light emitted by CFLs, such that some sources rate the best "soft white" CFLs as subjectively similar in color to standard incandescent lamps. White LED lamps now compete with CFLs for high-efficiency lighting, General Electric is stopping production of domestic CFL lamps in favour of LEDs; the parent to the modern fluorescent lamp was invented in the late 1890s by Peter Cooper Hewitt. The Cooper Hewitt lamps were used for photographic industries. Edmund Germer, Friedrich Meyer, Hans Spanner patented a high-pressure vapor lamp in 1927. George Inman teamed with General Electric to create a practical fluorescent lamp, sold in 1938 and patented in 1941. Circular and U-shaped lamps were devised to reduce the length of fluorescent light fixtures; the first fluorescent light bulb and fixture were displayed to the general public at the 1939 New York World's Fair.
The spiral CFL was invented in 1976 by Edward E. Hammer, an engineer with General Electric, in response to the 1973 oil crisis. Although the design met its goals, it would have cost GE about $25 million to build new factories to produce the lamps, thus the invention was shelved; the design was copied by others. In 1980, Philips introduced its model SL, a screw-in or bayonet mount lamp with integral magnetic ballast; the lamp used a folded T4 tube, stable tri-color phosphors, a mercury amalgam. This was the first successful screw-in replacement for an incandescent lamp. In 1985, Osram started selling its model EL lamp, the first CFL to include an electronic ballast. Volume was an issue in CFL development, since the fluorescent lamps had to fit in the same volume as comparable incandescent lamps; this required the development of new, high-efficacy phosphors that could withstand more power per unit area than the phosphors used in older, larger fluorescent tubes. In 1995, helical CFLs, manufactured in China by Shanghai Xiangshan, became commercially available.
Since that time, sales increased. Although their popularity varied across countries, in China CFLs were the "dominant technology in the residential segment" in 2011; the rise of LED lighting, however affected CFL sales and production. As a result of decreasing cost and better features, customers migrated toward LEDs. In India, "nearly 60 per cent of the lighting market in India has been taken over by LEDs" by 2018. LED prices fell well below US$5 for a basic bulb in 2015. In the United States, CFLs were facing the possibility of proposed regulations for 2017 that would create difficulty qualifying for the Energy Star rating. In early 2016, General Electric announced the phase out of CFL production in the US. There are two types of CFLs: integrated and non-integrated lamps. Integrated lamps combine the ballast in a single unit; these lamps allow consumers to replace incandescent lamps with CFLs. Integrated CFLs work well in many standard incandescent light fixtures, reducing the cost of converting to fluorescent.
3-way lamps and dimmable models with standard bases are available. Non-integrated CFLs have the ballast permanently installed in the luminaire, only the fluorescent tube is changed at its end of life. Since the ballasts are placed in the light fixture, they are larger and last longer compared to the integrated ones, they don't need to be replaced when the tube reaches its end-of-life. Non-integrated CFL housings can be sophisticated, they have two types of tubes: a bi-pin tube designed for conventional ballast, e.g. with G23 or G24d plug-in base, a quad-pin tube designed for an electronic ballast or a conventional ballast with an external starter. A bi-pin tube contains an integrated starter, which obviates the need for external heating pins but causes incompatibility with electronic ballasts. Non-integrated CFLs can be installed to a conventional light fixture using an adapter containing a built-in magnetic ballast; the adapter consists of a regular bulb screw, the ballast itself and a clip for the lamp's connector.
CFLs have two main components: a gas-filled tube. Replacement of magnetic ballasts with electronic ballasts has removed most of the flickering and slow starting traditional
A light fixture, light fitting, or luminaire is an electrical device that contains an electric lamp that provides illumination. All light fixtures have one or more lamps; the lamps may be in sockets for easy replacement—or, in the case of some LED fixtures, hard-wired in place. Fixtures may have a switch to control the light, either attached to the lamp body or attached to the power cable. Permanent light fixtures, such as dining room chandeliers, may have no switch on the fixture itself, but rely on a wall switch. Fixtures require an electrical connection to a power source AC mains power, but some run on battery power for camping or emergency lights. Permanent lighting fixtures are directly wired. Movable lamps have a cord that plugs into a wall socket. Light fixtures may have other features, such as reflectors for directing the light, an aperture, an outer shell or housing for lamp alignment and protection, an electrical ballast or power supply, a shade to diffuse the light or direct it towards a workspace.
A wide variety of special light fixtures are created for use in the automotive lighting industry, aerospace and medicine sectors. Portable light fixtures are called lamps, as in table lamp or desk lamp. In technical terminology, the lamp is the light source, which, in casual terminology, is called the light bulb; the International Electrotechnical Commission recommends the term luminaire for technical use. Fixture manufacturing began soon after production of the incandescent light bulb; when practical uses of fluorescent lighting were realized after 1924, the three leading companies to produce various fixtures were Lightolier, Artcraft Fluorescent Lighting Corporation, Globe Lighting in the United States. Light fixtures are classified by how the fixture is installed, the light lamp type. Table lamp fixtures, standard lamp fixtures, office task light luminaires. Balanced-arm lamp is a spot light with an adjustable arm such as anglepoise or Luxo L1. Gooseneck lamp Nightlight Floor Lamp Torch lamp or torchières are floor lamps with an upward facing shade.
They provide general lighting to the rest of the room. Gooseneck lamp Bouillotte lamp: see Bouillotte Ceiling Dome – Also called the light source are hidden behind a translucent dome made of glass, with some combination of frosting and surface texturing to diffuse the light; these can be flush-mount fixtures mounted into the ceiling, or semi-flush fixtures separated by a small distance. Open ceiling dome – the translucent dome is suspended a short distance below the ceiling by a mechanism, hidden with the exception of a screw-knob or other device appearing on the outer dome face, pulling this knob releases the dome Enclosed ceiling dome The translucent dome mates with a ring, mounted flush with the ceiling Recessed light – the protective housing is concealed behind a ceiling or wall, leaving only the fixture itself exposed; the ceiling-mounted version is called a downlight. "Cans" with a variety of lamps – this term is jargon for inexpensive downlighting products that are recessed into the ceiling, or sometimes for uplights placed on the floor.
The name comes from the shape of the housing. The term "pot lights" is used in Canada and parts of the US. Cove light – recessed into the ceiling in a long box against a wall. Troffer – recessed fluorescent light fixtures rectangular in shape to fit into a drop ceiling grid. Surface-mounted light – the finished housing is exposed, not flush with surface Chandelier Pendant light – suspended from the ceiling with a chain or pipe Sconce – provide up or down lights. Track lighting fixture – individual fixtures can be positioned anywhere along the track, which provides electric power. Under-cabinet light – mounted below kitchen wall cabinets Display Case or Showcase light – shows merchandise on display within an enclosed case such as jewelry, grocery stores, chain stores. Ceiling fan – May sometimes have a light referred to as a light kit mounted to it. Emergency lighting or exit sign – connected to a battery backup or to an electric circuit that has emergency power if the mains power fails High- and low-bay lighting – used for general lighting for industrial buildings and big-box stores Strip lights or Industrial lighting – long lines of fluorescent lamps used in a warehouse or factory Outdoor lighting and landscape lighting – used to illuminate walkways, parking lots, building exteriors and architectural details and parks.
Outdoor light fixtures can include forms similar to indoor lighting, such as pendants, flush or close-to-ceiling light fixtures, wall-mounted lanterns and dome lights. High-mast pole – or stanchion-mounted – for landscape and parking lots Bollard – A type of architectural outdoor lighting, a short, upright ground-mounted unit used to provide cutoff type illumination for egress lighting, to light walkways, steps, or other pathways. Solar lamp Street light Yard light Accent light – Any directional light that highlights an object or attracts attention to a particular area Background light – for use in video production Blacklight Christmas lights – called fairy lights or twinkle lights and are used at Christmas and other holidays for decoration. Emergency light – provides minimal light to a building during a power outage. Exit sign Flood light Safelight Safety lamp Searchlight Security lighting Step light Strobe ligh
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel and an oxidant atmospheric oxygen, that produces oxidized gaseous products, in a mixture termed as smoke. Combustion in a fire produces a flame, the heat produced can make combustion self-sustaining. Combustion is a complicated sequence of elementary radical reactions. Solid fuels, such as wood and coal, first undergo endothermic pyrolysis to produce gaseous fuels whose combustion supplies the heat required to produce more of them. Combustion is hot enough that incandescent light in the form of either glowing or a flame is produced. A simple example can be seen in the combustion of hydrogen and oxygen into water vapor, a reaction used to fuel rocket engines; this reaction releases 242 kJ/mol of heat and reduces the enthalpy accordingly: 2H2 + O2 → 2H2OCombustion of an organic fuel in air is always exothermic because the double bond in O2 is much weaker than other double bonds or pairs of single bonds, therefore the formation of the stronger bonds in the combustion products CO2 and H2O results in the release of energy.
The bond energies in the fuel play only a minor role, since they are similar to those in the combustion products. The heat of combustion is -418 kJ per mole of O2 used up in the combustion reaction, can be estimated from the elemental composition of the fuel. Uncatalyzed combustion in air requires high temperatures. Complete combustion is stoichiometric with respect to the fuel, where there is no remaining fuel, ideally, no remaining oxidant. Thermodynamically, the chemical equilibrium of combustion in air is overwhelmingly on the side of the products. However, complete combustion is impossible to achieve, since the chemical equilibrium is not reached, or may contain unburnt products such as carbon monoxide and carbon. Thus, the produced smoke is toxic and contains unburned or oxidized products. Any combustion at high temperatures in atmospheric air, 78 percent nitrogen, will create small amounts of several nitrogen oxides referred to as NO x, since the combustion of nitrogen is thermodynamically favored at high, but not low temperatures.
Since combustion is clean, flue gas cleaning or catalytic converters may be required by law. Fires occur ignited by lightning strikes or by volcanic products. Combustion was the first controlled chemical reaction discovered by humans, in the form of campfires and bonfires, continues to be the main method to produce energy for humanity; the fuel is carbon, hydrocarbons or more complicated mixtures such as wood that contains oxidized hydrocarbons. The thermal energy produced from combustion of either fossil fuels such as coal or oil, or from renewable fuels such as firewood, is harvested for diverse uses such as cooking, production of electricity or industrial or domestic heating. Combustion is currently the only reaction used to power rockets. Combustion is used to destroy waste, both nonhazardous and hazardous. Oxidants for combustion have high oxidation potential and include atmospheric or pure oxygen, fluorine, chlorine trifluoride, nitrous oxide and nitric acid. For instance, hydrogen burns in chlorine to form hydrogen chloride with the liberation of heat and light characteristic of combustion.
Although not catalyzed, combustion can be catalyzed by platinum or vanadium, as in the contact process. In complete combustion, the reactant burns in oxygen, produces a limited number of products; when a hydrocarbon burns in oxygen, the reaction will yield carbon dioxide and water. When elements are burned, the products are the most common oxides. Carbon will yield carbon dioxide, sulfur will yield sulfur dioxide, iron will yield iron oxide. Nitrogen is not considered to be a combustible substance when oxygen is the oxidant, but small amounts of various nitrogen oxides form when the air is the oxidant. Combustion is not favorable to the maximum degree of oxidation, it can be temperature-dependent. For example, sulfur trioxide is not produced quantitatively by the combustion of sulfur. NOx species appear in significant amounts above about 2,800 °F, more is produced at higher temperatures; the amount of NOx is a function of oxygen excess. In most industrial applications and in fires, air is the source of oxygen.
In the air, each mole of oxygen is mixed with 3.71 mol of nitrogen. Nitrogen does not take part in combustion, but at high temperatures some nitrogen will be converted to NOx. On the other hand, when there is insufficient oxygen to combust the fuel, some fuel carbon is converted to carbon monoxide and some of the hydrogen remains unreacted. A more complete set of equations for the combustion of a hydrocarbon in the air, requires an additional calculation for the distribution of oxygen between the carbon and hydrogen in the fuel; the amount of air required for complete combustion to take place is known as theoretical air. However, in practice, the air used is 2-3x. Incomplete combustion will occur when there is not enough oxygen to allow the fuel to react to produce carbon dioxide and water, it happens when the combustion is quenched by a heat sink, such as a solid surface or flame trap. Same as complete combustion, water is produced by incomplete combustion. However, carbon monoxide, and/or hydroxide are the products in
An electric light is a device that produces visible light from electric current. It is the most common form of artificial lighting and is essential to modern society, providing interior lighting for buildings and exterior light for evening and nighttime activities. In technical usage, a replaceable component that produces light from electricity is called a lamp. Lamps are called light bulbs. Lamps have a base made of ceramic, glass or plastic, which secures the lamp in the socket of a light fixture; the electrical connection to the socket may be made with a screw-thread base, two metal pins, two metal caps or a bayonet cap. The three main categories of electric lights are incandescent lamps, which produce light by a filament heated white-hot by electric current, gas-discharge lamps, which produce light by means of an electric arc through a gas, LED lamps, which produce light by a flow of electrons across a band gap in a semiconductor. Before electric lighting became common in the early 20th century, people used candles, gas lights, oil lamps, fires.
English chemist Humphry Davy developed the first incandescent light in 1802, followed by the first practical electric arc light in 1806. By the 1870s, Davy's arc lamp had been commercialized, was used to light many public spaces. Efforts by Swan and Edison led to commercial incandescent light bulbs becoming available in the 1880s, by the early twentieth century these had replaced arc lamps; the energy efficiency of electric lighting has increased radically since the first demonstration of arc lamps and the incandescent light bulb of the 19th century. Modern electric light sources come in a profusion of types and sizes adapted to many applications. Most modern electric lighting is powered by centrally generated electric power, but lighting may be powered by mobile or standby electric generators or battery systems. Battery-powered light is reserved for when and where stationary lights fail in the form of flashlights, electric lanterns, in vehicles. Types of electric lighting include: Incandescent light bulb, a heated filament inside a glass envelope Halogen lamps are incandescent lamps that use a fused quartz envelope filled with halogen gas LED lamp, a solid-state lamp that uses light-emitting diodes as the source of light Arc lamp Xenon arc lamp Mercury-xenon arc lamp Ultra-high-performance lamp, an ultra-high-pressure mercury-vapor arc lamp for use in movie projectors Metal-halide lamp Gas-discharge lamp, a light source that generates light by sending an electric discharge through an ionized gas Fluorescent lamp Compact fluorescent lamp, a fluorescent lamp designed to replace an incandescent lamp Neon lamp Mercury-vapor lamp Sodium-vapor lamp Sulfur lamp Electrodeless lamp, a gas discharge lamp in which the power is transferred from outside the bulb to inside via electromagnetic fieldsDifferent types of lights have vastly differing efficacies and color of light.
*Color temperature is defined as the temperature of a black body emitting a similar spectrum. The most efficient source of electric light is the low-pressure sodium lamp, it produces, for all practical purposes, a monochromatic orange-yellow light, which gives a monochromatic perception of any illuminated scene. For this reason, it is reserved for outdoor public lighting applications. Low-pressure sodium lights are favoured for public lighting by astronomers, since the light pollution that they generate can be filtered, contrary to broadband or continuous spectra; the modern incandescent light bulb, with a coiled filament of tungsten, commercialized in the 1920s, developed from the carbon filament lamp introduced about 1880. As well as bulbs for normal illumination, there is a wide range, including low voltage, low-power types used as components in equipment, but now displaced by LEDs Incandescent bulbs are being phased out in many countries due to their low energy efficiency. Less than 3% of the input energy is converted into usable light.
Nearly all of the input energy ends up as heat that, in warm climates, must be removed from the building by ventilation or air conditioning resulting in more energy consumption. In colder climates where heating and lighting is required during the cold and dark winter months, the heat byproduct has at least some value. Halogen lamps are much smaller than standard incandescent lamps, because for successful operation a bulb temperature over 200 °C is necessary. For this reason, most have a bulb of fused aluminosilicate glass; this is sealed inside an additional layer of glass. The outer glass is a safety precaution, to reduce ultraviolet emission and to contain hot glass shards should the inner envelope explode during operation. Oily residue from fingerprints may cause a hot quartz envelope to shatter due to excessive heat buildup at the contamination site; the risk of burns or fire is greater with bare bulbs, leading to their prohibition in some places, unless enclosed by the luminaire. Those designed for 12- or 24-volt operation have compact filaments, useful for good optical control.
They have higher efficacies and better lives than non-halogen types. The light output remains constant throughout their life. Fluorescent lamps consist of a glass tube that contains argon under low pressure. Electricity flowing through the tube causes the gases to give off ultraviolet energy; the inside of the tubes are coated with phosphors that give off visible light when struck by ultraviolet photons. They have much higher efficiency than incandescent lamps. For the same amount of light generated, they typic
An LED lamp or LED light bulb is an electric light for use in light fixtures that produces light using one or more light-emitting diodes. LED lamps have a lifespan many times longer than equivalent incandescent lamps, are more efficient than most fluorescent lamps, with some LED chips able to emit up to 303 lumens per watt. However, LED lamps require an electronic LED driver circuit when operated from mains power lines, losses from this circuit mean the efficiency of the lamp is lower than the efficiency of the LED chips it uses; the most efficient commercially available LED lamps have efficiencies of 200 lumens per watt. Commercially available LED chips have efficiencies of over 220 Lm/W; the LED lamp market is projected to grow by more than twelve-fold over the next decade, from $2 billion in the beginning of 2014 to $25 billion in 2023, a compound annual growth rate of 25%. As of 2016, LEDs use only about 10% of the energy an incandescent lamp requires. Similar to incandescent lamps, LEDs come to full brightness with no warm-up delay.
Frequent switching on and off does not reduce life expectancy as with fluorescent lighting. Light output decreases over the lifetime of the LED; some LED lamps are made to be a directly compatible drop-in replacement for incandescent or fluorescent lamps. LED lamp packaging may show the light outpur in lumens, the power consumption in watts, the color temperature in Kelvin or a colour description such as "warm white", "cool white" or "daylight", the operating temperature range, sometimes the equivalent wattage of an incandescent lamp delivering the same output in lumens; the directional emission characteristics of LEDs affect the design of lamps. While a single power LED may produce as much light output as an incandescent lamp using several times as much power, in most general lighting applications multiple LEDs are used; this can form a lamp with improved cost, light distribution, heat dissipation and also color-rendering characteristics. LEDs run on direct current, whereas mains current is alternating current and at much higher voltage than the LED can accept.
LED lamps can contain a circuit for converting the mains AC into DC at the correct voltage. These circuits contain rectifiers and may have other active electronic components, which may permit the lamp to be dimmed. In an LED filament lamp, the driving circuit is simplified because many LED junctions in series have the same operating voltage as the AC supply. Before the introduction of LED lamps, three types of lamps were used for the bulk of general lighting: Incandescent lights, which produce light with a glowing filament heated by electric current; these are inefficient, having a luminous efficacy of 10-17 lumens/W, have a short lifetime of 1000 hours. They are being phased out of general lighting applications. Incandescent lamps produce a continuous black body spectrum of light similar to sunlight, so produce high Color rendering index. Fluorescent lamps, which produce ultraviolet light by a glow discharge between two electrodes in a low pressure tube of mercury vapor, converted to visible light by a fluorescent coating on the inside of the tube.
These are more efficient than incandescent lights, having a luminous efficacy of around 60 lumens/W, have a longer lifetime 6,000-15,000 hours, are used for residential and office lighting. However, their mercury content makes them a hazard to the environment, they have to be disposed of as hazardous waste. Metal-halide lamps, which produce light by an arc between two electrodes in an atmosphere of argon and other metals, iodine or bromine; these were the most efficient white electric lights before LEDs, having a luminous efficacy of 75–100 lumens/W and have a long bulb lifetime of 6,000-15,000 hours, but because they require a 5 - 7 minute warmup period before turning on, are not used for residential lighting, but for commercial and industrial wide area lighting, outdoor security lights and streetlights. Like fluorescents, they contain hazardous mercury. Considered as electric energy converters, all these existing lamps are inefficient, emitting more of their input energy as waste heat than as visible light.
Global electric lighting in 1997 consumed 2016 terawatthours of energy. Lighting consumes 12% of electrical energy produced by industrialized countries; the increasing scarcity of energy resources, the environmental costs of producing energy the discovery of global warming due to carbon dioxide emitted by the burning of fossil fuels, which are the largest source of energy for electric power generation, created an increased incentive to develop more energy-efficient electric lights. The first low-powered LEDs were developed in the early 1960s, only produced light in the low, red frequencies of the spectrum; the first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation in 1994. The existence of blue LEDs and high-efficiency LEDs led to the development of the first'white LED', which employed a phosphor coating to convert the emitted blue light to red and green frequencies creating a light that appears white. Isamu Akasaki, Hiroshi Amano and Nakamura were awarded the 2014 Nobel Prize in Physics for the invention of the blue LED.
China further boosted LED research and development in 1995 and demonstrated its first LED Christmas tree in 1998. The new LED technology application became prevalent at the start of the 21st century by US and Japan and starting 2004 by Korea and China (S
Carbide lamps, or acetylene gas lamps, are simple lamps that produce and burn acetylene, created by the reaction of calcium carbide with water. Acetylene gas lamps were used to illuminate buildings, as lighthouse beacons, as headlights on motor-cars and bicycles. Portable acetylene gas lamps, worn on the hat or carried by hand, were used in mining in the early twentieth century, they are still employed by cavers and cataphiles. Small carbide lamps called "carbide candles" or "smokers" are used for blackening rifle sights to reduce glare, they are used because of the sooty flame produced by acetylene. A mining or caving lamp has calcium carbide placed in the generator; the upper reservoir is filled with water. A threaded valve or other mechanism is used to control the rate at which the water is allowed to drip into the chamber containing the calcium carbide. By controlling the rate of water flow, the production of acetylene gas is controlled. This, in turn, controls the flow rate of the gas and the size of the flame at the burner, thus the amount of light it produces.
This type of lamp has a reflector behind the flame to help project the light forward. An acetylene gas powered lamp produces a broad light. Many cavers prefer this type of unfocused light as it improves peripheral vision in the complete dark; the reaction of carbide with water is exothermic and produces a fair amount of heat independent of the flame. In cold caves, carbide lamp users can use this heat to help stave off hypothermia. Acetylene is produced by the reaction: CaC2 + 2H2O → C2H2 + Ca2The acetylene combusts in the atmosphere: 2C2H2 + 5O2 → 4CO2 + 2H2O + ΔH = −1300 kJ/molWhen all of the carbide in a lamp has been reacted, the carbide chamber contains a wet paste of slaked lime which can be used to make a cement; this is emptied into a waste bag and the chamber can be refilled. In 1892, Thomas Willson discovered an economically efficient process for creating calcium carbide in an electric arc furnace from a mixture of lime and coke; the arc furnace provides the high temperature required to drive the reaction.
Manufacture of calcium carbide was an important part of the industrial revolution in chemistry, was made possible in the US as a result of massive amounts of inexpensive hydroelectric power produced at Niagara Falls before the turn of the twentieth century. In 1895, Willson sold his patent to Union Carbide. Domestic lighting with acetylene gas was introduced circa 1894 and bicycle lamps from 1896. In France, Gustave Trouvé, a Parisian electrical engineer made domestic acetylene lamps and gasometers; the first carbide bicycle lamp developed in the United States was patented in New York on August 28, 1900 by Frederick Baldwin. Another early lamp design is shown in a patent from Duluth, Minnesota on October 21, 1902. In the early 1900s, Gustaf Dalén invented the Dalén light; this combined two of Dalén's previous inventions: the substrate Agamassan and the Sun valve. Inventions and improvements to carbide lamps continued for decades. After carbide lamp open flames were implicated in an Illinois coal-seam methane gas explosion that killed 54 miners, the 1932 Moweaqua Coal Mine disaster, carbide lamp use declined in United States coal mines.
They continued to be used in the coal pits of other countries, notably USSR. In the birth of the cinema of Iquitos, a carbide lamp was used as light support to project the first film in the Casa de Fierro, in 1900. Carbide lighting was used in rural and urban areas of the United States which were not served by electrification, its use began shortly after 1900 and continued past 1950. Calcium carbide pellets were placed in a container outside the home, with water piped to the container and allowed to drip on the pellets releasing acetylene; this gas was piped to lighting fixtures inside the house, where it was burned, creating a bright flame. Carbide lighting was prone to gas leaks and explosions. Early models of the Ford Model T automobile used carbide lamps as headlamps. Acetylene lamps were used on riverboats for night navigation; the National Museum of Australia has a lamp made in about 1910, used on board PS Enterprise, a paddle steamer, restored to working order and in the museum's collection.
They are used for night hunting. Early caving enthusiasts, not yet having the advantage of light-weight electrical illumination, introduced the carbide lamp to their hobby. While replaced by more modern choices, a substantial percentage of cavers still use this method. In cave surveys, carbide lamps are favoured for the lead or "point" surveyor, who must identify suitable points in the cave to designate as survey stations; the sooty carbide flame may be used to mark cave walls with a station label. Favoured for this purpose are all-brass lamps or lamps made with no ferromagnetic metals, as these lamps do not deflect the needles of a magnetic compass, read while brightly illuminated from above using the caver's lamp. Apart from their use as cave surveying tools, many cavers favour carbide lamps for their durability and quality of illumination, they were once favoured for their relative illumination per mass of fuel compared to battery powered devices, but this advantage was negated with the advent of high-intensity LED illumination.
The acetylene producing reaction is exothermic, which means that the lamp's reactor vessel will become quite warm to the touch. The heat from the flame can be used to warm the body by allowing the exhaust gases to flow under a shirt or poncho pulled out from the body, a technique discovered immediately by cold miners, nicknamed by cavers the "Palmer fu