
On this page, we will discuss 5 types of electric lighting: incandescent, halogen, fluorescent, LED, and compact fluorescent. But to start, let's watch this 1:46 minute overview about lighting from the U.S. Department of Energy.
We light up dark spaces with the flip of a switch and we have been doing so since Thomas Edison invented the incandescent light bulb about 140 years ago. The same type is still used but there are more light bulb options. These bulbs will give you the light you want while using less energy (thus lower emissions and cost associated with that energy production). Initially, we moved to an energy-saving compact fluorescent bulb that uses about 25% less energy. But now it is LED bulbs Ithat often light up our homes and offices. So, replace a traditional light bulb in your living room. Put an efficient LED bulb and you get the same light but with about 75% less energy and Energy Star bulbs last 10 to 25 times longer. Lighting your house used about 10% of your electricity use. So, when looking for a new bulb you'll find more energy-saving choices on store shelves giving you more options but save you money and that's a pretty bright idea.
In the “good old days,” when it was dark outside, people went to bed! Around the American civil war, there were other sources of light, obviously. Candles had been used for a while, and lamps burning sperm whale oil were available. Poor old Moby Dick was a popular choice for this oil and was becoming quite scarce when, fortunately for the Sperm Whale, crude oil was found in Pennsylvania. Originally the crude oil was sold as rheumatism medicine before it was found that kerosene could be produced (separated out of the crude). Kerosene was a clean-burning light source (more about this in another lesson). Town gas has also been used to light towns (town gas tended to be the vapors of heated coal synthesis gas) or in some cases natural gas. However, the naked flame was always a fire risk, and when the incandescent light bulb was perfected, you could have light 24 hours a day, whenever it was needed (providing you could afford it, and there was an electricity supply!)
Incandescent

bulb are two connections from
which a tungsten coil is
suspended. Shaking the bulb
produces a sound when the
filament finally breaks.
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How many bulbs are visible from where you are sitting? How many are in your home? My guess is that you might have 30+ light bulbs. A decade ago these would probably be incandescent bulbs and it's still a good idea to know how they work. For these bulbs, electricity is used to heat a tungsten filament. This thin metal strand (the filament) gets so hot it becomes white-hot, producing bright white light. The bulb itself is simply an envelope in which we can put inert gases so the filament does not burn. The problem with this bulb is that it produces a lot of heat. This is fine if you are using your light bulb in an easy bake oven, but when you are lighting your house at night in the summer — you are heating the room — which you are probably cooling with an air conditioner! Thus the use of an incandescent light bulb is inefficient. We measure efficiency as the amount of useful energy that we get out of a system divided by the energy we put into a system, multiplied by 100 to obtain the %. While this low-efficiency bulb was acceptable for a long time, it is being phased out through legislation reducing production and use to help aid emission reductions. While this occurred under the George W. Bush presidency and was expanded under the Obama presidency. Some of the changes were reduced or eliminated under the Trump administration (you will see this as a common theme). There is obviously friction between emission reduction and cost (more on this later).
Efficiency = Useful energy out / energy in x 100
At about 5% efficiency, you can see that we are wasting a great deal of energy by using an incandescent light bulb. This is one of the basics of all our energy systems (one of the three laws), we don’t get out what we put in; there is always a reduction or an “energy tax.” We measure how much light intensity comes off a light bulb by either candle-power or lumens. By putting more electricity into a light bulb, we can, to a point, get more light. We measure the “flow” of electricity by the term Watt (W). You might purchase a 60 W light bulb, for example, that will produce 890 lumens of light and should last 1,000 hours of use. If you need more light, a higher wattage bulb will provide more light (and use more energy). Due to this inefficiency, these bulbs are being phased out and replaced by LED or compact fluorescent bulbs.
Fluorescent

This is a much better method of producing light as it is far more efficient (x 4 incandescent). That means it is about 20 % efficient which is still not an impressive number. How does fluorescent lighting work? Much of the energy required to "light" a fluorescent light is needed as soon as the light switch is turned on. The electrodes at either end of the lamp are the starting point for the electron to “flow” through the tube (from one electrode to the other). As they pass through the tube they excite the mercury vapor inside the tube; the excited mercury gives off ultraviolet radiation. Unfortunately, that is not very useful for us, as we cannot “see” that wavelength of light. However, we can use this ultraviolet radiation to excite a phosphor coating on the inside of the bulb which, when excited, gives off visible light. The lower rate of energy use (wattage) will however still produce as much light as an incandescent light because of the efficiency increase over the incandescent lighting (look at lumens levels to compare). Offices, universities, malls, supermarkets, apartment complexes will all use this type of lighting, as the light is on for long time periods, often 24 hours a day in some locations. Many of these bulbs are being replaced by LEDs.
Compact Fluorescent Lighting

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As discussed above, an incandescent light bulb produces light by heating a tungsten wire to white-hot temperatures. No wonder it is not a very efficient form of lighting. Fluorescent is a lot better at about 20% efficient (converting electricity into light), but fluorescent lights were for a long time only long tubes. Now compact fluorescent light bulbs are available that simply screw into the same lamps that an incandescent light bulb did. The advantage is that your electricity bill will be less because for the same production of light (how many lumens), less electricity is used. The compact fluorescent bulbs also last much longer than the incandescent bulbs, so they don't need to be replaced as often. Yes, they will be more expensive to purchase but when you look at the lifecycle (how much money in total that you pay), compact fluorescent bulbs make a great deal of economic and environmental sense (electricity comes mostly from aging fossil fuel utilities that produce air pollution). An additional benefit is that less heat from the bulb provides less risk of fire or (they are safer). Now LED's are the better option.
Light Emitting Diode (LED)

LEDs are small light sources that become illuminated by the movement of electrons through a semiconductor material. LEDs have been around for a long time; the red, green, and blue lights were in various electronics such as my 1970s stereos (the things we used before iPods!) and now in cell phones and many other consumer electronics, from coffee machines to computers. Recently, they have become a lighting option for white light (often directional lighting for task lighting: reading lamps, countertops, etc.) Often there is an array of LEDs to provide enough light. They have a high efficiency (similar to fluorescent), don’t produce much heat, and can last a long time. They are increasingly common in general lighting and have a nicer color than compact fluorescent lighting. They are also being used in traffic lights, streetlights, Xmas tree lights, and other more common applications. They use less electricity, the light is closer to incandescent in color, and they last longer.
Lightbulbs and heat
We can "see" heat if we use an Infra-Red camera. In the image below, you can see two lamps, one with a Halogen lamp the other with a Compact Fluorescent lamp. The CFL has a higher efficiency because it does not produce as much heat. Replacing incandescent bulbs with compact fluorescent bulbs is a good way to lower your electricity bills. LEDs are however now the better choice commonly.