Welcome to Lesson 6!

Welcome to the lesson on lighting. In this chapter, we are basically going to look at basic lighting principles and definitions. Light can be generated in several ways, and we are going to look at the ways in which we can generate light and discover which is the most efficient of all these methods. We will also learn a little bit about some of the definitions, like how light is measured and what the intensity is, and how to measure the efficacy or efficiency of lighting and so on and so forth.

We will also look at the different types of bulbs that are available around for us to use. The U.S. is currently in a transition to more efficient lightbulbs. 10 years ago, incandescent lightbulbs dominated the market, but now ~100 % of all lightbulb replacements are some form of energy efficient model. Some of you may be familiar with light emitting diode (LED) and compact florescent (CFL) bulbs, and we will be looking at how each of these types work and also how the light is generated. What is the efficiency with which we generate lighting?

As far as calculations are concerned, we will be doing the most important calculation in this chapter again, and that is life cycle analysis. Life cycle analysis is, as I mentioned in the last chapter, the total cost over the life cycle of a product. The life cycle begins the moment you buy and lasts until the moment the product dies or is put to retirement. Until then, what does it cost? In other words, the costs would be to buy it and to feed it the electricity or the energy, and then if there are any maintenance costs, they are also involved. So we have to calculate all of these aspects over the lifetime of a particular bulb, and then compare bulb A with bulb B. That life cycle analysis is what you will have to spend quite a bit of time with and make sure you understand it.

We'll also consider the way we measure the efficiency and the efficacy of lighting, and also improved lighting controls. If we have an existing home or existing system, what can we add; how can we improve the efficiency? How can we get more light for less energy? So this is a chapter where we can work to save a lot of energy. And we spend about, almost 40 billion dollars a year in this country on lighting, so easily we can save about 20 billion dollars and the associated energy that is involved and the impact. Think about it -- the impact that we can make on the environment by using more efficient light. So let’s get started.

Lighting

These are some statistics on lighting in the US. Information like this does not get updated often (The U.S. hasn't been spending money on these types of studies), so here is where we were as of 2015:

• Lighting accounts for 5 to 10 percent of all electricity consumed in the United States.
• An average household dedicates ~4 percent of its energy budget to lighting. Commercial establishments consume about ~20 percent of their total energy just for lighting.
• Technologies developed during the past 15 years can help us cut lighting costs 30 to 75 percent while enhancing lighting quality and reducing environmental impacts.

Variety of Lighting Use in the United States

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

Lesson 6 Objectives

Upon completing this lesson, students will be able to:

• explain basic lighting principles and definitions;
• list the various types of lighting and explain how each type works;
• describe energy efficient lighting options;
• calculate life cycle costs (LCC) for different types of lighting.

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

When most people buy a light bulb, they look for watts (W). Recall that watt is a unit of power, (i.e., the rate at which energy is consumed from the electricity supplier). It does not say anything about the light.

The most common measure of light output (or luminous flux) is the lumen. All lamps are rated in lumens, as shown in the figure below, and every bulb has 3 parameters listed on the package:

• Lamp lumen output or light output
• Power consumption in watts
• Life of the bulb in hours

Parameters listed on a light bulb.

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

Watch this video (1:44) below to find out more about lumens.

Footcandles

A footcandle (fc) is the Standard unit of measure for illumination on a surface. It is a lumen of light distributed over a 1-square-foot (0.09-square-meter) area.

Footcandle

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

The average footcandle level on a square surface is equal to the amount of lumens striking the surface, divided by the area of the surface.

Example

A 40 watt bulb produces about 505 lumens and has a life of about 1,000 hours. When this bulb is used to light a room of 10 x 10 feet, these 505 lumens are distributed over 100 square feet of floor area. What is the illumination?

505 lumens of light/100 ft²= 5.05 lumens per ft² or 5.05 fc

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

$$1Footcandle=1Lumen/f{t}^2 =1Lux\left( metric \right)$$

How much light is needed in a room depends on the task(s) being performed (contrast, requirements, space, size, etc.). There are three different types of task-oriented lighting: Ambient, Task, and Accent. The light requirement also depends on the ages of the occupants and the importance of speed and accuracy of the task.

• Ambient lighting is general purpose lighting—an example is the lighting used in hallways for safety and security. An illumination of 30–50 fc is generally the maximum that one needs for this purpose.
• Task lighting is lighting that is designed for specific tasks. Reading and writing are the most light-intensive tasks and require about 50 fc at home. Tasks like cooking, sewing, or repairing a wrist watch require more -- about 200–300 fc. However, the area with this level of illumination will be small. Increasing the light everywhere is not required and is a waste of energy.
• Accent lighting is the lighting that is provided to highlight certain objects or areas, for example, the use of floodlights to highlight a painting or a statue. Accent lighting also illuminates walls, so they blend more closely with naturally bright areas like ceilings and windows. Accent lighting can be high intensity or subtle.

How Much Light is needed?

Now we are going to examine the question, "How much lighting we need?" The answer depends on what kind of task we are doing.

a. Task being performed; Ambient, Task, or Accent

Say if you are just walking in the hallway; you need a little bit of light to see each other and to recognize what is there. That lighting is called ambient lighting, or general purpose lighting. Here's an example where I am sitting here in this conference room and trying to take notes or reading a book, and this type of lighting, the type of lighting that I need here, is called task lighting. I am doing the specific task of reading a book. Or you can take another example of cooking. You know, you are cooking something, and you need to know exactly whether it is done or not; you need lighting there. That is again, task oriented lighting.

So, it depends on the task that you are doing. There are three types usually: first is the ambient, the second one is task lighting, and the third one is accent lighting. The idea there is you want to highlight certain aspects; maybe a painting, maybe a statue that you own or any other thing, a map. You know, whatever you want to highlight. Instead of highlighting entire room lighting, you can highlight that particular piece with some special lighting, and that type of lighting is called accent lighting.

b. Age of the occupants

How much light we need also depends on the age of the group, the age of the people that are in there, in the room. Usually, older people need higher amounts of light than younger people.

c. Importance of speed and accuracy

We also must consider the speed and accuracy with which we want to do certain things. Say, for example, a person is repairing a small wristwatch. Obviously they need more lighting, especially if they want to repair very fast. So speed and accuracy with which we want to do a job also dictate how much light we want.

Color Rendering Index

Lamps are assigned a color temperature (according to the Kelvin temperature scale) based on their "coolness" or "warmness." The human eye perceives colors as cool if they are at the blue-green end of the color spectrum, and warm if they are at the red end of the spectrum.

Instructions: Click "play" to see examples of the light sources that temperatures represent. (Note: The video has no audio.)

The ability to see colors properly is another aspect of lighting quality. Objects' colors appear to be different under different types of light. The color rendering index (CRI) scale is used to compare the effect of a light source on the color appearance of its surroundings. A scale of 0 to 100 defines the CRI. A higher CRI means better color rendering, or less color shift.

Instructions: Move the drag button in the center of the picture below to see the difference between low CRI and high CRI.

Factors Affecting the Number of Lamps Required

Instructions: Click on the hot spots below to determine the factors that affect the number of lamps required:

There are five basic types of lighting:

• Incandescent
• Fluorescent
• High-intensity discharge
• LED

Incandescent Bulbs

Thomas Alva Edison invented the incandescent light bulb with reasonable life. Lewis Latimer has perfected it with the use of carbon filament.

The incandescent bulb consists of a sealed glass bulb with a filament inside. When electricity is passed through the filament, the filament gets hot. Depending on the temperature of the filament, radiation is emitted from the filament.

The filament's temperature is very high, generally over 2,000º C, or 3,600º F. In a "standard" 60-, 75-, or 100-Watt bulb, the filament temperature is roughly 2,550º C, or roughly 4,600º F. At high temperatures like this, the thermal radiation from the filament includes a significant amount of visible light.

This principle of obtaining light from heat is called ‘incandescence.” At this high temperature of 2,000º C, about 5 percent of the electrical energy converts into visible light and the rest of it is emitted as heat or infrared radiation.

Instructions : Press play to see how an incandescent light bulb works. (Note: The animation has no audio.)

Let’s now look at several different types of incandescent bulbs.

Standard incandescent bulbs

Standard incandescent bulbs are most common and yet are the most inefficient. Larger wattage bulbs have a higher efficacy (more lumens per Watt) than smaller wattage bulbs.

Instructions: Click the “graph” button below to create a graph comparing Watts and efficiency, and then answer the question below.

Tungsten halogen bulbs

Tungsten halogen is an incandescent lamp with gases from the halogen family sealed inside the bulb and an inner coating that reflects heat back to the filament. It has similar light output to a regular incandescent bulb, but with less power. Halogens in the gas filling reduce the material losses of the filament caused by evaporation and increase the performance of the lamp.

A tungsten halogen lamp

Credit: Tungsten halogen lamp © Penn State is licensed under CC BY-NC-SA 4.0

Tubular tungsten-halogen bulbs

Tubular tungsten-halogen bulbs are commonly used in “torchiere” floor lamps, which reflect light off of the ceiling, providing more diffused and suitable general lighting.

Although these provide better energy efficiency than the standard A-type bulb, these lamps consume significant amounts of energy (typically drawing 300 to 600 W) and become very hot (a 300-W tubular tungsten-halogen bulb reaches a temperature of about 2600° C compared to about 600° C for a compact fluorescent bulb). Because Tungsten-halogen lamps operate at very high temperatures (high enough to literally fry eggs), they should not be used in fixtures that have paper- or cellulose-lined sockets.

Tubular tungsten-halogen lamp.

Credit: Lawrence Berkeley Laboratory

Halogen bulbs

A halogen bulb is often 10 to 20 percent more efficient than an ordinary incandescent bulb of similar voltage, wattage, and life expectancy. Halogen bulbs may also have two to three times as long a lifetime as ordinary bulbs. How much the lifetime and efficiency are improved depends largely on whether a premium fill gas (usually krypton, sometimes xenon) or argon is used. The image below shows a picture taken with an Infrared camera comparing the heat produced by a halogen and a compact fluorescent light bulb. The red and white color zones are extremely hot, and the blue zones are cooler.

A comparison of heat generated by a Halogen and CFL light bulbs.

Credit: Lawrence Berkeley Laboratory

Reflector Lamps

Reflector Lamps - Light waves from a bulb spread in all directions. The light that goes toward the back is not useful when the light is most needed in the front. Reflector lamps (Type R) are designed to spread light over specific areas.

Reflector lamps have silver coating on the sides, like any mirror, and therefore all the light waves passing through the sides or the back are reflected to the front. Therefore, they are called reflector lamps and are also called floodlighting, spotlighting, and down lighting bulbs.

Instructions: Click the buttons below to see the difference between a regular and reflective lamp light bulb:
(Note: The animations have no audio.)

Parabolic aluminized reflector (PAR) lamps

Parabolic aluminized reflector (PAR) lamps (shown in the image below) are also available with halogen technology to operate at 120 volts. A standard 150-W incandescent spotlight can be replaced with a lower wattage halogen lamp, reducing electricity consumption by up to 40 percent.

A Reflector Lamp (Type R) light bulb.

Credit: A Reflector Lamp (Type R) light bulb © Penn State is licensed under CC BY-NC-SA 4.0

The fluorescent lamp is a major advancement and a commercial success in small-scale lighting since the original tungsten incandescent bulb. These bulbs are highly efficient compared to incandescent bulbs. Fluorescence is the phenomenon in which absorption of light of a given wavelength by a fluorescent molecule is followed by the emission of light at longer wavelengths. Please watch the following 2:19 presentation about fluorescent bulbs:

Types of Lighting, Fluorescent

These fluorescent bulbs that you are seeing, the long tubes, basically have two electrodes on the sides. And you pass electric current, and that creates an arc between the two electrodes, and that tube is filled with inert gasses. The inert gasses are argon or an argon plus krypton mixture. No air in there. Just an argon plus krypton mixture, and you spark it with a little bit of mercury in there. When you generate that arc between two electrodes, on the two sides of that tube, that arc excites these mercury atoms to a higher state. And then when they are coming back to the ground state, they have to release that excess energy that they absorbed, and they release it as non-visible UV light.

UV light is not visible. UV light is dangerous. Remember, UV light is what comes out when the mercury atoms are coming back to the ground state. But you know this tube is coated on the inside. The inside wall is coated with a different material, a special material called phosphorous. And those particles that are coated have a unique ability to absorb this UV light that is released when the mercury atoms are coming to the ground state. So that is absorbed, and that phosphorous coating will give out visible light. It absorbs UV light and gives out visible light. So without that phosphorous coating in there, a fluorescent bulb would not work. Fluorescence is absorbing UV light in the phosphorous and giving out visible light.

So, change of frequency, or change of energy status, is called fluorescence and a bulb that uses this principle is called a fluorescent bulb.

A fluorescent bulb consists of a glass tube with a phosphorus coating, a small amount of inert gas (usually argon or krypton), mercury, and a set of electrodes. Contact points on the outside of the tube carry electricity into the bulb.

Instructions: The animation below (1:04) shows a step-by-step depiction of how fluorescent lamps provide light. You may replay the video to review steps. (Note: The animation has no audio.)

Fluorescent lamps are about 2 to 4 times as efficient as incandescent lamps at producing light at the wavelengths that are useful to humans. Thus, they run cooler for the same effective light output. The bulbs themselves also last a lot longer—10,000 to 20,000 hours versus 1,000 hours for a typical incandescent.

Fluorescent lights need ballasts (devices that control the electricity used by the unit) for starting and for circuit protection. Ballasts require energy, and for some type of ballasts, efficiency is only achieved if the fluorescent lamp is left on for long periods of time without frequent on-off cycles.

The image below shows a picture of a full-size fluorescent lamp fixture. The energy savings for existing fluorescent lighting can be increased by:

• re-lamping (e.g., replacing an existing lamp with one of a lower wattage);
• replacing ballasts;
• replacing fixtures with more efficient models.

Full-size fluorescent lamp fixture

Credit: Full-size fluorescent lamp fixture © Penn State is licensed under CC BY-NC-SA 4.0

Full-size fluorescent lamps are available in several shapes, including straight, U-shaped, and circular configurations. Lamp diameters range from 1" to 2.5". The most common lamp type is the four-foot (F40), 1.5" diameter (also called T12) straight fluorescent lamp. More efficient fluorescent lamps are now available in smaller diameters, including the 1.25 " (also called T10) and 1" (also called T8).

Fluorescent lamps are available in color temperatures ranging from warm (2700 K) "incandescent-like" colors to very cool (6500 K) "daylight" colors.

Cool white (4100 K) is the most common fluorescent lamp color. Neutral white (3500 K) is becoming popular for office and retail use.

Compact Fluorescent Lamps

Compact Fluorescent Lamps are miniaturized fluorescent lamps that usually have premium phosphors, which often come packaged with integral or modular ballast, as shown in the image below.

Types of compact fluorescent bulbs available on the market

Compact fluorescent lamps (CFLs) come in a variety of sizes and shapes including (a) twin-tube integral, (b and c) triple-tube integral, (d) integral model with casing that reduces glare, (e) modular circline and ballast, and (f) modular quad-tube and ballast. CFLs can be installed in regular incandescent fixtures, and they consume less than one-third as much electricity as incandescent lamps.

Credit: United States Department of Energy

Compact Fluorescent Lamps have the following characteristics. They:

• Typically have a standard screw base that can be installed into nearly any table lamp or lighting fixture that accepts an incandescent lamp.
• Come in a variety of sizes and shapes and are being used as energy saving alternatives to incandescent lamps.
• Have a much longer life—6,000 to 20,000 hours (10 to 20 times longer), compared to 750 to 1000 hours for a standard incandescent.
• Can replace incandescent bulbs that are roughly 3 to 4 times their wattage, but can cost up to 10 times more than comparable incandescent bulbs.
• produce ~70 lumens per watt.
• Are an energy-efficiency investment. Although they cost more, they are very economical in the long run.

Compact Fluorescent Bulbs

Credit: Roach, John. "To fight climate change, don't mention it, study suggests." NBC News. April 29, 2013.

High-intensity discharge (HID) lamps are similar to fluorescents in that an arc is generated between two electrodes. The arc in an HID source is shorter, yet it generates much more light, heat, and pressure within the arc tube.

Below are HID sources, listed in increasing order of efficacy (lumens per watt):

• mercury vapor
• metal halide
• high-pressure sodium
• low-pressure sodium

Like fluorescent lights, HID also requires ballasts, and they take a few seconds to produce light when first turned on because the ballast needs time to establish the electric arc.

Originally developed for outdoor and industrial applications, HID lamps are now used in office, retail, and other indoor applications. Their color rendering characteristics have been improved, and lower wattage have recently become available (as low as 18 watts).

When HID lamps reach "restrike" time, the gasses inside the lamp are too hot to ionize, and time is needed for the gasses to cool and pressure to drop before the arc will restrike. This process of restriking takes between 5 and 15 minutes, depending on which HID source is being used. Therefore, good applications of HID lamps are areas where lamps are not switched on and off intermittently.

Types of High-Intensity Discharge Lamps

Mercury vapor lamps

Mercury vapor lamps are widely used to light both indoor and outdoor areas such as gymnasiums, factories, department stores, banks, highways, parks, and sports fields.

Mercury vapor lamps consist of an inner arc discharge tube constructed of quartz surrounded by an outer hard borosilicate glass envelope. Shortwave UV, a result of the decay of mercury atom electrons from an excited to a stable state, is readily transmitted through the inner quartz tube but is virtually blocked by the outer glass envelope during normal operation.

Mercury Vapor Lamp

Credit: Mercury Vapor Lamp © Penn State is licensed under CC BY-NC-SA 4.0

Metal Halide lamps

Metal Halide lamps are similar to mercury vapor lamps but use metal halide additives inside the arc tube along with the mercury and argon. These additives enable the lamp to produce more visible light per watt with improved color rendition.

Wattages range from 32 to 2,000, offering a wide range of indoor and outdoor applications. The efficacy of metal halide lamps ranges from 50 to 115 lumens per watt, typically about double that of mercury vapor.

Because of the good color rendition and high lumen output, these lamps are good for sports arenas and stadiums. Indoor uses include large auditoriums and convention halls. These lamps are sometimes used for general outdoor lighting, such as parking facilities, but a high-pressure sodium system is typically a better choice.

High-Pressure Sodium (HPS) Lamp

The high-pressure sodium (HPS) lamp is widely used for outdoor and industrial applications. Its higher efficacy makes it a better choice than metal halide for these applications, especially when good color rendering is not a priority.

HPS lamps differ from mercury and metal-halide lamps in that they do not contain starting electrodes; the ballast circuit includes a high-voltage electronic starter. The arc tube is made of a ceramic material which can withstand temperatures up to 2,372°F. It is filled with xenon to help start the arc, as well as a sodium-mercury gas mixture.

The efficacy of the HPS lamp is very high (as much as 140 lumens per watt.) For example, a 400-watt high pressure sodium lamp produces 50,000 initial lumens. The same wattage metal halide lamp produces 40,000 initial lumens, and the 400-watt mercury vapor lamp produces only 21,000 initially.

Sodium, the major element used, produces the "golden" color that is characteristic of HPS lamps. Although HPS lamps are not generally recommended for applications where color rendering is critical, HPS color rendering properties are being improved. Some HPS lamps are now available in "deluxe" and "white" colors that provide higher color temperature and improved color rendition. The efficacy of low-wattage "white" HPS lamps is lower than that of metal halide lamps (lumens per watt of low-wattage metal halide is 75-85, while white HPS is 50-60 LPW).

As we mentioned before, LED stands for light emitting diode. This type of lighting is completely different than the other types of lighting we have discussed so far. They do not need specific gases, filaments or moving parts because they are made from semiconducting materials, which makes and LED a semi-conducting device that produces light. The underlying principles of an LED light are the opposite function of a photovoltaic system. An LED semiconductor chip form an junction between and n-type and p-type semiconductor materials. N-type materials pass charge using electrons, and p-types pass charge using holes. See the figure below for a description of the circuit.

Basic LED circuit

Credit: "Semiconductor Device Fabrication." ScienceDirect. 2008.

LEDs do not directly produce white light. Due to this quirk, LEDs were originally used for colored light applications such as traffic lights and exit signs.

LED Traffic Light

Credit: Limer, Eric. "The Huge Advantages (and One Problem) of LED Traffic Lights." Popular Mechanics. May 15, 2018.

Because of their extremely high efficiencies (150 lumens per watt!!, and up to 90 % more efficient than incandescent light bulbs), researchers found ways to convert their outputs to white light. As such, they are one of the highest efficiency lighting options available.

Here are three examples:

• Phosphor conversion, in which a phosphor is used on or near the LED to convert the colored light to white light
• Color-mixed systems, in which light from multiple monochromatic LEDs (e.g., red, green, and blue) is mixed, resulting in white light
• A hybrid method, which uses both phosphor-converted (PC) and monochromatic LEDs.

These innovations have allowed these bulbs to be suitable for general lighting in residential applications. These bulbs last for 5-10 years depending on their usage. Now, you can find them in almost every store, and they look something like this.

General purpose whitelight LED lights.

Credit: Ahmed, Faisal. "LED Bulbs are about to be Disrupted." Medium. July 30, 2022.

Performing a life-cycle cost analysis (LCC) gives the total cost of a lighting system—including all expenses incurred over the life of the system. This analysis can be applied not only to lighting but for most of the appliances, automobiles, heating systems, and so on, when two systems are compared to determine the most cost effective options.

There are two reasons to do an LCC analysis:

1. To compare different systems, or bulbs in this case.
2. To determine the most cost-effective system or a bulb.

For some lighting systems, one of two situations may exist:

1. The initial cost may be high, but the energy costs will be low over its lifetime.
2. The initial cost to buy a bulb or a system and the energy or the maintenance costs may be low, but the useful life of such a bulb or system may be short. (In this case, we may have to replace the appliance several times to get the same useful life as the other option.)

Therefore, a life-cycle cost (LCC) analysis can be helpful for comparing the total costs incurred over the lifetime of a lighting system. It is, in essence, calculating all the costs incurred to buy, maintain, and run the system over its lifetime.

In the formula above,

• Cost to buy is the purchase price of the bulb or the system.
• Cost to maintain is the cost incurred to maintain it in good operating condition. (For example in the case of a car, an engine oil change every 3,000 miles is part of maintenance costs.)
• Cost of energy is the energy or the fuel it takes to run the appliance or bulb for its lifetime.
• Replacement cost is the cost to replace the bulb. If bulb A has a life of 1000 hrs and bulb B has a life of 10,000 hours, then Bulb A needs to be replaced 10 times to get the same useful life period as that of bulb B. Therefore, 10 A bulbs need to be purchased for each B Bulb.

The table below shows a life cycle cost analysis in comparing an incandescent bulb and a CFL.

This analysis shows clearly that each incandescent bulb replaced with a CFL that would fit into a regular incandescent bulb fixture would save about $39.25 over 10,000 hours of operation. Imagine the number of bulbs that you have at home: living room, kitchen, bathrooms, bedrooms, table lights, floor lamps, ceiling lights, closets, garage, basement, and so on. There are energy saving options all over the home.

Although they save energy, there are some disadvantages with CFLs:

• They are often physically larger than the incandescent bulbs they replace, and simply may not fit the lamp.
• The light is generally cooler—less yellow—than incandescent light bulbs. This may result in less than pleasing contrast with ordinary lamps and ceiling fixtures. Newer models have been addressing this issue.
• Some types (usually iron ballasts) may produce an annoying flicker.
• Ordinary dimmers cannot be used with compact fluorescents.
• Like other fluorescents, operation at cold temperatures (under around 50–60 degrees F) may result in reduced light output.
• There may be an audible buzz from the ballast.

Efficacy is the ratio of light output from a lamp to the electric power it consumes, and is measured in lumens per watt (LPW).

The image is a horizontal bar graph comparing the approximate efficacy, measured in lumens per watt (lm/W), of various lighting technologies. The x-axis represents the efficacy scale ranging from 0 to 160 lm/W, while the y-axis lists different lighting types: Incandescent, Halogen, Compact Fluorescent (CFL), Linear Fluorescent, High-Intensity Discharge (HID) including High-Pressure Sodium (HPS) and Metal Halide, and LED.

Text description of the Approximate Efficacy image.

Below is a list of different types of light bulbs and the light output of each (measured in lumens per watt):

• Incandescent: 8 - 22
• Mercury: 22 - 58
• Fluorescent: 30 - 38
• Metal Halide: 74 - 132
• High Pressure Sodium: 74 - 132
• Low Pressure Sodium: 70 - 152
• LED: 10-200

Credit: Slide #35 "Led Basics." University of Coimbra. July 2017.

Conventional incandescent lamps in a single four-way traffic light consume roughly 85 kWh of electricity per day and cost about $1,600 per year to operate. LED lights use just 10 percent of the electricity that incandescent lamps use, so the opportunity for savings is enormous.

Lighting controls give you the flexibility to design a space for multiple use and easy access. They should be a part of the lighting plan for every room. Both manual and automatic controls can cut energy costs by making it easier to use lights only when and where they are needed.

Controls used with high-wattage incandescent bulbs are especially effective for saving energy, but they should be considered for use with any lights that might be left on when no one is using them.

Always choose controls that are compatible with the bulb and ballast. Try to obtain the best quality, so the controls will perform well over time.

Types of Lighting Controls

Switches

The simple on-off switch, whether mounted on a wall or on the light fixture, should always be obvious and convenient.

• On fixtures with pull-cord switches, attach an object at the end that is easy to see and grasp.
• Install multiple wall switches in areas that have more than one entrance, such as hallways, staircases, and large rooms.
• Ensure that these switches should be easy to find as well by adding devices such as oversized toggles or switch plates that glow in the dark.
• A small indicator light near a switch can signal when lights that are out of sight—in the basement or outdoors, for example—have been left on.
• If a main switch in a room controls several lights, each fixture should have its own switch, so individual lights can be turned off if they are not needed.
• In rooms such as kitchens, where lights are used for different purposes, overhead ambient lights, counter, or island lights should be on separate switches.
• A three-level switch in lamps is a simple way to use one fixture for several lighting needs. When the higher levels are not necessary, switch it to the lowest level to save energy.

Photocells

A photosensor measures the light level in an area and turns on an electric light when that level drops below a set minimum. They are most effective with lights that stay on all night long, such as some outdoor fixtures or night lights. If a light does not need to remain on throughout the night, use a timer or motion detector.

Timers

Timers are an inexpensive way to control the amount of time a light stays on inside the home or outdoors. They can be located at a light switch, at a plug, or in a socket. Some models are turned on manually and set to turn off after a designated number of minutes or hours. Others can be programmed to turn on and off at specified times. Both mechanical and solid-state timers are available, and some offer the option of a manual override. Some screw-base compact fluorescent bulbs cannot be used with timers, so check the manufacturer's recommendations.

Be careful not to set timers so a light might turn off in an area when someone could be left in the dark. Or, install a glow-in-the-dark switch plate or a very low-wattage night-light with a photosensor near the switch, so it is easy to find.

Motion or Occupancy Sensors

Motion detectors, or occupancy sensors, have proven to be an excellent way to save energy, especially in bathrooms and bedrooms where lights are frequently left on. They are also popular outdoors for walkways, driveways, and as security lights.

Sensors can operate automatically to turn lights on when movement is detected, then off after a specified period of no motion, or they can have manual on or off switches. Some models feature dimmers that reduce light to a preset level rather than turn completely off when there is no movement; others come with photo sensors that turn lights on only when the light level is below a preset point and motion is detected.

Follow manufacturer's instructions for installing sensors to ensure the proper coverage area. Also, be sure the lights are compatible with the sensors. Some compact fluorescents should not be used with motion detectors, nor should high intensity discharge lights because of their inability to relight quickly.

Dimmers

Dimming fluorescent lamps is not all that easy to do. If you reduce power to the lamp, the filaments will not be as hot, and will not be able to thermionically emit electrons as easily. If the filaments get too cool by dimming the lamp greatly, usually the lamp will just go out. If you force current to continue flowing while the electrodes are at an improper temperature, then severe, rapid degradation of the thermionic material on the filaments is likely. To effectively, reliably, and safely dim fluorescent lamps below around half brightness or so, you need special equipment that may only work properly with a specific lamp. Such equipment typically gives some power to the filaments to keep them at a workable temperature, while the current flowing through the bulb is greatly reduced.

Manual dimming controls allow occupants of a space to adjust the light output or illumination. This can result in energy savings through reductions in input power, as well as reductions in peak power demand, and enhanced lighting flexibility.

Fluorescent lighting fixtures require special dimming ballasts and compatible control devices. Some dimming systems for high-intensity discharge lamps also require special dimming ballasts.

Incandescent
Bulb

Credit:
© Penn State
is licensed under
CC BY-NC-SA 4.0

Incandescent Bulbs:

• do not require a ballast
• have a warm color appearance with a low color temperature and excellent color rendering (CRI 100)
• are a compact light source
• require simple maintenance due to screw-in Edison base
• are a less efficacious light source
• have a shorter service life than other light sources in most cases
• have a filament that is sensitive to vibrations and jarring
• can get very hot during operation
• must be properly shielded because incandescent lamps can produce direct glare as a point source
• require proper line voltage, as line voltage variations can severely affect light output and service life

Fluorescent
Bulb

Credit:
© Penn State
is licensed under
CC BY-NC-SA 4.0

Fluorescent Bulbs:

• require a ballast
• have a range of color temperatures and color rendering capabilities
• have low surface brightness compared to point sources
• have a cooler operation
• are more efficacious compared to incandescent
• ambient temperatures and convection currents can affect light output and life
• all fixtures installed indoors must use a Class P ballast that disconnects the ballast in the event it begins to overheat; high ballast operating temperatures can shorten ballast life
• have options for starting methods and lamp current loadings
• require compatibility with ballast
• low temperatures can affect starting unless a "cold weather" ballast is specified

High
Intensity
Discharge
(HID)
Bulb

Credit:
© Penn State
is licensed under
CC BY-NC-SA 4.0

High Intensity Discharge (HID) Bulbs:

• require a ballast
• ambient temperature does not affect light output, although low ambient temperatures can affect starting, requiring a special ballast
• are a compact light source
• are high lumen packages
• are a point light source
• have a range of color temperatures and color rendering abilities depending on the lamp type
• have a long service life
• are highly efficacious in many cases
• have line voltage variations, possible line voltage drops, and circuits sized for high starting current requirements which must be considered

EGEE 102 Lesson 6 Review

For task lighting a specific task, specific task meaning either reading or writing or cooking or repairing something, that requires generally about 40 to 50 foot candles. Sometimes, if you're working on small objects, you may need even a little more light. Accent lighting is the lighting that is used to highlight certain things at home, for example, a painting or a statue or something you want to highlight.

And you should be able to design lighting for certain areas. That's something that you may want to look at. Let's say you're designing for a general purpose hallway. You have 10 square feet, and each square foot requires about 10 lumens, which means 100 square feet requires 1,000 lumens. So you should be able to figure that out.

Color rendering index - different lighting produces different abilities to look at true colors. And you need to know the color rendering index. It is measured on a scale from zero to 100, and 100 being perfect colors or absolutely no color shift. And that is generally possible in natural light.

And when you have a room, how many lamps are required? That depends on how many lumens. You need total area and lumens, and each bulb gives out a certain number of lumens, and how many bulbs you require is based on that.

For example, if you have a room of 100 square feet, you need, let's say, 20 foot candles, which means 20 lumens per square foot. So every square foot requires 20 lumens. So in this case, 20 times 100 would be 2,000 lumens needed for that room.

And let's say if a 60-watt bulb gives you 1,000 lumens, you need two of these bulbs to get that 2,000 lumens. Of course, there are other factors like reflections off the walls and also the light fixture efficiency and so on and so forth. So you need to know the factors that affect, particularly the number of lamps required.

Types of lighting - you need to know the differences between incandescence, fluorescence, and high-intensity discharge lamps - how you produce the light, the process, and the hardware that is involved. And you should be able to perform life-cycle analysis. In other words, if you have two different types of light, for example an incandescent light and a CFL bulb - you are able to perform a life-cycle analysis using these two bulbs.

Life cycle analysis is cost to own and operate for the entire lifetime of the bulb. And remember, you have to compare for the same life period. These are not different lifetimes. If one bulb lasts 1,000 hours, and the other one last 8,000 hours, you have to use eight of these 1,000-hour bulbs to compare, actually. And cost to own, cost to supply the energy, energy cost, and maintenance costs together will be the lifetime cost.

Test Yourself

The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!

1. How is light measured?
2. What factors determine the amount of light that is needed in a room?
3. What are the three main methods of producing light?
4. Explain the difference between incandescence, fluorescence, and high intensity discharge.
5. What are the common ways in which we can improve energy efficiency?
6. A 60-watt light bulb produces 3 watts of radiant energy and 57 watts of heat energy. What is its efficiency?
7. A 100-watt light bulb is left on all day (24 hours). How much did it cost to operate the light bulb if electricity costs 5 cents per kWh?
8. A 100 watt incandescent light bulb is operated for 12 hours, and a 15 watt fluorescent light bulb is operated for the same period of time. At 10 cents per kWh, what are the cost savings of the fluorescent bulb?
9. Jackie Smith, who is very conscious about the environment, would like to know how much energy she can save by switching to fluorescent bulbs. Estimate the total energy savings for Jackie, who uses a light bulb fixture, by comparing the total costs to own and operate a 23-Watt CFL bulb instead of the 100 Watt incandescent bulb that she has been using. The expected life of incandescent and CFL bulbs is 1000 h and, 8000 hours. The purchase price of an incandescent bulb is \$0.50 and the CFL is \$7.50. If Jackie Smith replaces 24 bulbs at home with CFLs, what would her savings be if the electricity cost is \$0.085 per kWh?

Extra Resources

For more information on topics discussed in Lesson 6, see these selected references:

1. Energy.gov Office of Energy Efficiency and Renewable Energy
2. GE Consumer Lighting
3. Don Klipstein's Lighting
4. Energy.gov Building Technologies Office