A Basic Guide to Modern Lighting Options For Home And Office
This article is not concerned with style or fashion, but with technologies, energy, and environmental issues. We will be discussing the different ways in which visible radiation is produced and the materials used. Also in discussion is the energy efficiency of each option, that is to say the number of watts of power required to produce a given number of lumens (more on that later). Lastly are the potential environmental and human issues each technology carries with it.
There are an ever-growing number of varieties of lighting available on the market. Remarkably, Thomas Edison’s vacuum bulb has remained almost unchanged since General Electric Company introduced Tungsten filaments in 1906 and is still by and large the most common household light source. Since then, the world has seen Arc Discharge bulbs, such as street lamps and projectors, phosphorescent (fluorescent) lighting, and the latest player: light emitting diode (LED) lamps derived from the wonders of quantum mechanics and semi-conducting materials.
Incandescent bulbs are a relatively simple device. The hundred years of invention that took place were not about making light, many people knew how to make light with electricity; it was about keeping the filament from burning out. Light is generated by forcing a large electric current to flow through a very small wire. Just like forcing a large crowd of people through a narrow alley, electricity doesn’t like to be forced into tight spaces either. As the people get cramped together they get hot and angry. The same thing happens when you try and push to much electricity through a wire. The wire gets hotter and hotter the more electricity that is forced through it. Eventually the wire starts to glow as some of the electricity is forced to leave the wire instead of flowing along it. It does this in the form of radiation. The spectrum of this radiation is very large, starting with low frequency “heat” radiation, visible light radiation, all the way up to invisible ultraviolet radiation. Unfortunately, the bulk of the radiation is the infrared range “heat” radiation. This means that for every unit of energy you put into an incandescent bulb you get not just light, but a lot of heat and other un-useful radiation.
So, as time went on people started to look for ways to get light from a bulb than could be had from a filament. They were also looking for ways to make better light for certain new applications like movie projectors. If you have ever burned ants with a magnifying glass, you know that when you put a light source through a lens it projects exactly on the other side. The same happens when you use a filament in a projector, you project a filament on the wall. One way to solve these issues is with an arc discharge lamp. They work by eliminating the filament inside the bulb and replacing the vacuum with a very specific vapor or gas to prevent the metal parts from oxidizing (burning). An electric current is made to pass through the gas between two metal terminals inside the bulb. The electric arc makes the electrons in the atoms of the vapor jump bands and this causes radiation to be emitted. This process is a little better than the hot-wire technique because you have more control of the type of radiation through choosing what vapor is inside the bulb. We also attain a more point-source light than we get with a filament so the projectionists are happy. There is still a great deal of infrared radiation emitted and typically more ultraviolet as well forcing manufacturers to put UV coatings on some bulbs to protect living beings exposed to the bulb.
The next major innovation was the use of fluorescence or phosphorescence. Fluorescence is the phenomena where materials glow when exposed to specific wavelengths of radiation. It happens the wavelengths are typically invisible to the human eye, but the resulting glow from the phosphors is visible. The advantage here is that the specific wavelengths needed to induce the phosphors are relatively easy to generate and can be done so without generating all the other wavelengths of the electromagnetic spectrum like incandescents and arc discharge lighting do. The result is a cooler running bulb because there is less energy wasted. Less energy wasted means a cheaper bulb to run. Originally, fluorescent bulbs were notorious for a green hue. Modern fluorescent bulbs are now available in a variety of color hues from cool whites to warm whites that replicate natural light very well.
A quick note on bulb colors: Bulb manufactures use a color scale called Kelvin or K to describe the color a bulb emits. This scale is based on the color of a hot block of carbon at a specific thermal temperature. The Kelvin scale is similar to the Celsius scale and is used by scientists and engineers. If you heat a block of carbon hot enough, like most materials, it starts to glow as energy starts leaping off in the form of radiation. The block starts to glow orange at low temperatures, like 2000 degrees K. As the temperature gets to about 4000 degrees K it looks to be white. As it gets even hotter, at about 7000 to 10,000 degrees K it looks more blue. So here is the irony: emotionally, we associate the color blue with cold and red with hot. So we say a blue tinted bulb has a cool color while a red tinted bulb has a warm color. It’s a little humorous to think that technically, a blue color is generated by a hotter temperature than that of a red color!
Back to bulb evolution… As scientists began to discover all the new ways semiconductors could be used in the early 1900’s they stumbled upon a peculiar trait of some materials. When you pass an electric current through these specially designed materials, the electrons to jump bands and emit visible radiation much like what happens in an arc discharge bulb, except we don’t have to generate an arc. Scientist have been able to custom design the materials such that a very small electric current causes electrons to jump bands and emit very specific wavelengths. These devices have almost zero waste as all the energy goes into making the very specific wavelength we are looking for. In the 1950’s, we saw the first common applications in infrared “lasers” that we now have in common television remote controls. As science progressed they were able to create materials that emit various frequency radiation. Today, red, blue, and green LEDs are common and now white LEDs are at the forefront of development. The first white LEDs were indeed blue-white to white but not very bright. Now we have extremely intense white LEDs available on the market in a variety of applications. The drawbacks to LEDs are cost and directionality. Cost will be addressed in volume with time, but as we will see later, this really isn’t that big a problem now. Directionality is an issue. LEDs emit light from a surface, typically a flat surface. This means light is emitted in a limited number of directions from an LED. This is improved with lenses, but you never get the same effect as an old fashioned light bulb from a singe LED. This is OK, and even preferred, for directional devices like flashlights and indicators. But the old incandescent light bulb has had a century to train us to use light bulbs in omni directional fixtures like table lamps and chandeliers. This presents a challenge for replacing incandescents serving in these fixtures with an LED. Manufacturers are dealing with this by creating arrays of many individual LED lamps inside what looks like a conventional light bulb. By pointing individual lamps in different directions inside the bulb an omni directional bulb is created using LEDs. This also leads to expense as it complicates manufacturing.
So, now that we have an overview of the basic types of lighting we can delve into the decision making process when evaluating what bulb we want to use. More and more we are concerning ourselves with the cost of energy as fossil fuels become scarce and the consequences of liberating eons of stored carbon back into the environment become apparent. There are also other environmental issues surrounding lighting in regards to the materials used. What chemicals are we exposing ourselves to when bulbs are broken or disposed of? We mentioned earlier that fluorescents use phosphorus compounds to generate light. They also use a mercury vapor inside the tubes to generate the necessary radiation. This is a concern not to be taken lightly as both of these materials are very harmful to living beings. Fluorescent bulbs must always be recycled in the appropriate manner. Local transfer stations and recycling centers can help you with this. When a fluorescent bulb, or other mercury vapor bulb, is broken you need to take special precautions and steps. We have borrowed the following from the Environmental Protection Agency’s (EPA) website:
Before Clean-up: Air Out the Room
If we are responsible and take care in handling CFL and other fluorescent bulbs, these dangers are mitigated and we can take advantage of the tremendous energy savings they have to offer. Typically, a CFL bulb will generate the same amount of light while consuming 10 to 15% of the energy of an incandescent bulb. You can visit the Intelligent Heat and Power, LLC lighting guide and calculator to see comparisons of bulbs and calculate the cost of running each type. We use a metric we call cost per 1,000 hours to compare bulbs. My calculating the total cost over the life of a bulb including the bulb cost and the power cost to light it and then dividing by 1000 hours we have a level playing field to measure lighting costs.
For example, lets compare a 60W incandescent to a comparable 15W CFL. Starting with the price, the 60W bulb costs less than $0.50 per bulb typically. On the other hand, and 15W CFL cost about $6 per bulb. That seems expensive at first glance compared to the old standard. But lets look further. The rated life for incandescents varies dramatically and have improved significantly over the years. Typically, they are rated at about 5,000 hours. A CFL is often 10,000 to 15,000 hours rated life. So they last two to three times longer than an incandescent and they use 1/7th the energy. So what does the energy cost? Electric rates vary dramatically from community to community so we recommend you do use our calculator to generate your own number, but for example we will use $0.15 per kWh. To calculate the power used in the life of the bulb, multiply the actual watts (W) by the rated life. This gives us watt-hours. (the little k stand for 1,000) Now the electric companies charge us by the kWh, or thousand-watt-hours, so we have to divide our watt-hour number by 1000 to get kWh. So for the 60W bulb at 5,000 hours and $0.15/kWh we get:
60*5000/1000*0.15 = $45
So the incandescent uses $45 worth of electricity over it’s life. For the CFL:
15*10,000/1000*0.15 = $22.5
So even though the CFL runs for twice as long, it uses half the electricity in its life. But, we need to add the cost of the bulbs to the equation because the CFL cost 12X as much as the incandescent. So:
$45+$0.50 = $45.50 and $22.50+$6 = $28.50
So this already look appealing doesn’t it? But it gets better. Because you would have to buy two incandescents in the same period that the CFL was running, we have to double the cost of the CFL to be apples to apples. So for 10,000 hours of lighting, the CFL costs $28.50 and the incandescent costs an amazing $91.00! So that $0.50 bulb actually costs over three times as much as a $6 CFL bulb. Suddenly, our world has changed for the brighter.
As a famous TV chef says, “Let’s kick it up a notch!”. We already mentioned that LEDs use even less energy than CFLS and last even longer. So, what does that look like? Let’s compare the LED to the CFL.
An LED sounds ridiculously expensive at $80 for one bulb. I have to admit, it still catches me off guard. But lets see what it costs over its entire life. It uses 8W of power lasts an amazing 50,000 hours. So:
8*50,000/1000*0.15 = $60
$60 + $80 = $140
So the total cost of the LED is $140 over it’s entire life. But again, it takes 5 CFL bulbs to equal the life of the LED! So:
5*$28.50 = $142.5 vs $140 for the CFL
or
$450 for the Incandescent
We see that the LED makes even a little more savings than the CFL. Not much you say? Well, yes, for this case the difference is small because larger LED bulbs have many, many small LEDs inside and that makes them more expensive as they get bigger. So at the moment, you will find that lower wattage LED’s will often make more sense than larger ones until sales volumes drive the price down. Let’s also not forget the potential hazards and environmental impacts of fluorescent bulbs. LEDs do not present these hazards and if the total cost is similar or better, why not go for the more environmentally friendly product?
To make comparing bulbs simpler, we have built our calculator using the cost per 1000 hour or CP1k metric. We break down the costs to 1000 hours of use so you don’t have to divide the life of the longer life bulb by the life of the shorter etc. The calculator does all that for you and gives you an index number to compare bulbs.
I hope you found this article useful and if you have feedback let us know by email.
Intelligent Heat and Power, LLC
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