Lesson Four - Introduction to Energy Efficiency and P2 in Lighting
After successfully completing this lesson, you should be able to:
1. Describe and summarize current energy efficiency situation and primary energy sources in the US.
2. Describe basic terminology in lighting such as lumens, lighting efficiency, CRI and color temperature.
3. Describe and summarize basic types of lighting and appropriate application for each type.
4. Analyze and prescribe appropriate P2 alternatives given a particular lighting environment.
5. Analyze and perform financial comparison of P2 alternatives in lighting.
Starting this lesson, we will learn various P2 opportunities in common industrial/commercial energy use. The goal for "P2 in Energy" part is to acquire knowledge and skills necessary to develop proposals for common energy efficiency projects. First, let's review what is the current energy efficiency situation and primary energy sources in the U.S., since most of you should have discussed this in HSC 156 - Environmental Health in the 21st Century, so....
From the above answers, we can see not only we rely on polluting primary energy sources such as coal to generate electricity, we are also doing a very poor job in terms of converting efficiency, only 30% efficient when converting coal to electricity! Do we use electricity efficiently? Not at all if we use the conventional incandescent light bulb at only 5% efficient!
We heavily reply on imported crude oil for our transportation, but unfortunately our gasoline engine is only 10% efficient! Certainly primary energy source is not only used for generating electricity or for transportation, they are also used for heating, cooling and a variety of other industrial uses, how efficient are those uses?
Let's look at a summary of U.S. Energy Sources and End Uses as illustrated in the chart below. On the left of the chart, it lists primary energy sources such as oil, natural gas, coal and nuclear, etc. Then end use consumption are listed including transportation, industrial, residential and electric power generation. On the right side of the chart, energy efficiency for each end use consumption is listed. For example, the energy efficiency in the transportation is about 15%, electric power generation is about 35% efficient. Across all the energy end use consumption, no single sector is over 50% efficient! Energy cost money, waste energy means wasted money. For example, Illinois State University monthly energy bill is about $1 million! Since energy efficiency is less than 50%, it means half a million dollar is wasted per month.
As you will learn in the next few modules, improving energy efficiency is very doable! There are major energy efficiency opportunities in common industrial/commercial energy use with great pay-back and significant impact on pollution reduction. Primary industrial/commercial energy use include:
2. Heating and cooling
4. Air compressors
We will discuss energy efficiency opportunities in 1 and 2 above areas. In this lesson, we will focus energy efficiency opportunities in lighting.
Because lighting consumes most energy in a building! The figure below illustrates the energy intensity (KWH/ft2) by end use according to the Energy Information Administration (EIA) report in 2011. EIA is a division of US Department of Energy.
Commercial Buildings Primary Energy End Use Splits (2011)
Source: DOE, 2011 Buildings Energy Data Book, Section 3.1.4, March 2012. http://buildingsdatabook.eren.doe.gov/ .
The commercial sector encompasses a variety of different building types, including schools, hospitals, restaurants, hotels, office buildings, banks, and stadiums. According to US Department of Energy, a t an estimated cost of $38 billion a year, lighting represents the largest source of electricity consumption in U.S. commercial buildings. Even in residential buildings, lighting consumes 10% of the total energy use as shown below.
Residential Buildings Primary Energy End Use Splits (2011)
Source: DOE, 2011 Buildings Energy Data Book, Section 2.1.5, March 2012. http://buildingsdatabook.eren.doe.gov/ .
What is the goal of lighting efficiency? Provide the amount of light needed at a minimum wattage. Before we get into how to achieve the goal of lighting efficiency, we need to familiarize ourselves with some basic terminology in lighting:
–The amount of light given off is measured in lumens, also referred as brightness.
–One lumen is the equivalent of the light given off by one candle in one square foot.
–The amount of power input to a light bulb to produce light is measured in watts
–is measured by KWh (kilowatts hour):
KWh = Watts × hours of operation/1000 ...................................................................equ (1)
Unit of lamp efficiency is lumen/watt.
Note the above equation can be re-arranged into:
Lumen output = Lamp efficiency X watts of power input ........................equ (3)
Now let's look at a couple of applications of the lighting efficiency concept.
The hallway of the Physics Department at Michigan State University has 20, 72-watts energy-saving halogen light bulbs whose lamp efficiency is 20.7 lumen/watt. The university is considering changing these light bulbs into compact fluorescent light (CFL) bulbs whose lamp efficiency is 60 lumen/watt.
1. What watts of the CFL bulbs should the university buy, assuming each energy-saving halogen light bulb is replaced with a CFL bulb?
2. Assuming these light bulbs are on 24 hours a day, 7 days a week for 50 week of a year, how much energy/electricity will be saved in a year by switching to CFLs?
1. Since each halogen lightbulb is replaced with a CFL bulb, the lumen output from a CFL bulb should be the same as that from a halogen lightbulb.
Based on equ (3);
For a halogen lightbulb, lumen output = 20.7 lumen/watts x 72 watts = 1490.4 lumens
Then based on equ (4);
So the university should buy 25-watts CFLs, these CFLs will produce the same amount of light (i.e. lumens) as compared to existing lightbulbs. One can see as we use lamps with higher efficiency, for the same amount of light produced, we can use a much lower watts lamps.
2. Let's first figure out electricity consumed for both bulbs in a year, the difference is the energy saving.
Based on equ (1);
When using halogen lightbulbs, electricity/energy consumption (kWh) = 20 (bulbs) x 72 watts x (24 hr/day x 7 days/week x 50 weeks/year) /1000 = 12,096 kWh
When using CFLs, electricity/energy consumption (kWh) = 20 (bulbs) x 25 watts x (24 hr/day x 7 days/week x 50 weeks/year) /1000 = 4200 kWh
Electricity saving = 12,096 kWh - 4200 kWh =7,896 kWh.
The dormitory supervisor of a major university is considering switching 60 watts energy-saving halogen lightbulbs with 9W Light Emitting Diode (LED) replacement bulbs. Halogen efficiency is 13 lumens/watt and LED efficiency is 90 lumens/watt. There are a total of 400 such lightbulbs in the dorm. Assume each lightbulb burns an average of 4 hours per day for 300 days/year. The university is paying 8 cents per kWh for electricity.
1. Is the light output from LED bulbs comparable to halogen bulbs?
2. How much electricity will be saved in a year by switching to LEDs?
3. How much ($) will university save in electricity bill in a year by switching to LEDs?
1. Let's calculate the lumen output for both bulbs.
For halogen bulbs, Lumen output = Lamp efficiency X watts of power input = 13 (lumens/watt) x 60 watt = 780 lumens
For LEDs, Lumen output = Lamp efficiency X watts of power input = 90 (lumens/watt) x 9 watt = 810 lumens
Yes, the light output from LED bulbs are comparable to (actually greater than) halogen bulbs.
2. Let's calculate electricity consumption for both bulbs in a year, the difference in the saving.
For halogen bulbs, electricity consumption (kWh) = 400 (bulbs) x 60 watt x (4 hr/day x 300 days/yr)/1000 = 28,800 kWh
For LEDs, electricity consumption (kWh) = 400 (bulbs) x 9 watt x (4 hr/day x 300 days/yr)/1000 = 4,320 kWh
Electricity saving = 28,800 kWh - 4,320 kWh = 24,480 kWh
3. Savings in electricity bill ($) $0.08 kWh x 24,480 kWh = $1,958.40
A good energy efficient light fixture not only needs to provide enough light, but also good quality of light! How do we measure light quality? Two terms that you will come across on light quality: Color Temperature and Color Rendition.
Color Temperature – refers to the color of the light source. By convention, yellow-red colors (like the flames of a fire) are considered warm, and blue-green colors (like light from an overcast sky) are considered cool. Color temperature is measured in Kelvin (K) temperature. Confusingly, higher Kelvin temperatures (3600–5500 K) are what we consider cool and lower color temperatures (2700–3000 K) are considered warm. Cool light is preferred for visual tasks because it produces higher contrast than warm light. Warm light is preferred for living spaces because it is more flattering to skin tones and clothing. A color temperature of 2700–3600 K is generally recommended for most indoor general and task lighting applications.
Color Rendition - refers to how colors appear when illuminated by a light source. Color rendition is generally considered to be a more important lighting quality than color temperature. Most objects are not a single color, but a combination of many colors. Light sources that are deficient in certain colors may change the apparent color of an object. The Color Rendition Index (CRI) is a 1–100 scale that measures a light source's ability to render colors the same way sunlight does. The top value of the CRI scale (100) is based on illumination by a 100-watt incandescent light bulb. A light source with a CRI of 80 or higher is considered acceptable for most indoor residential applications.
As shown in the above imagine, the very low CRI of 40 makes this lady in the above photo looks like a dead person as opposed to how vibrant she looks under a CRI of 100.
Notice how vibrant and distinct colors of fruit and vegetables under CRI of 91 fade when CRI decreases to 70.
It depends! Each type of industry requires different quality of lighting. For example, Midwest Fiber - a local storage company doesn't require very good quality lighting. A CRI of 70 and above might be sufficient.
On the other hand, a printing facility - Bloomington Offset Printing Inc. where inspection of the quality of the finished product needs color to be rendered accurately. Higher CRI becomes essential in this facility. Note the person in yellow is checking to make sure that color from the printing press matches customers specification.
What do you think CRI requirements for jewelry stores and art museums?
High CRIs! In a jewelry store, sales depend on the looks! CRI has to be high to show the beautiful sparkly colors of jewelry. In a museum, high CRI is essential to show the beauty of arts. Even in a residential home, we can use high CRI light fixtures in parts of the room where you want to show the beauty of your treasures.
There are a number of types of lighting such as:
They vary in efficiency, operating hours, light quality, etc. We will briefly discuss each one in the following section.
Thomas Edison invented the incandescent light bulb nearly 120 years ago, and it still works pretty much as it did then. Inside a glass bulb (as shown below), electricity heats up a wire filament made of tungsten, causing it to glow and give off light. Of course, electrical heaters work in much the same way, and that's why about 95 percent of the energy produced by standard incandescent lights is heat, not light. As a result, standard incandescent bulbs are inefficient light sources that are only 5% efficient. The heat they produce can drive up your electricity bill in hot weather if your home or office is air-conditioned. While standard incandescent bulbs last usually between 750 to 1,000 hours before burning out, some long-life bulbs last up to 2,500 hours by using thicker filament. The trade off is that long-life bulbs are less energy efficient and produce less light per watt. One more thing, incandescent bulbs are excellent at rending color, CRI of incandescent is about 100.
There are two common types of incandescent lightbulbs:
Halogens give off a crisp, very bright, white light, CRI is 98-100. They maintain their light output over time without fading with age, as incandescent do. The small size of halogen lamps permits their use in compact optical systems for projectors and illumination.Halogens are a little more expensive than standard incandescent lightbulbs, but are less expensive to operate because of their higher efficacy and longer life expectancy (1000 to 3000 hours). They are commonly used in reflector lamps such as indoor and outdoor flood or spot lighting, indoor recessed and track fixtures, and floor and desk lamps. All halogen bulbs are dimmable, but at the cost of a shorter life. Below are some common types of halogen lightbulbs.
Fluorescent lamps use 25%–35% of the energy used by incandescent lamps to provide the same amount of illumination (lamp efficiency of 30–110 lumens per watt). They also last about 10 times longer (7,000–24,000 hours).
Two general types of fluorescent lamps include these:
The light produced by a fluorescent tube is caused by an electric current conducted through mercury and inert gases in the tube. The gas in the tube glows with ultraviolet light. This in turn excites a white phosphor coating on the inside of the tube, which emits visible light throughout the surface of the tube. It is important to note that much more mercury is saved from reduced electricity generation than is contained in fluorescent bulbs.
Fluorescent lamps require a ballast to regulate operating current and provide a high start-up voltage. Electronic ballasts outperform standard and improved electromagnetic ballasts by operating at a very high frequency that eliminates flicker and noise. Electronic ballasts also are more energy-efficient. Electronic ballasts do not contain PCBs (Poly-chlorinated Biphenols) as some of the magnetic ballast do. Special ballasts are needed to allow dimming of fluorescent lamps.
Improvements in technology have resulted in fluorescent lamps with color temperature and color rendition that are comparable to incandescent lamps.
The traditional/standard tube-type fluorescent lamps are usually identified as T12 (12/8 of an inch tube diameter). They are installed in a dedicated fixture with a built-in ballast. The two most common types are 40-watt, 4-foot (1.2-meter) lamps, and 75-watt, 8-foot (2.4-meter) lamps. Now, tubular fluorescent technology has improved. New products such as T8 and T5 are much more energy efficiency than T12 (T12 – 57 lumens/watt; T8 – 92 lumens/watt; T5 – 103 lumens/watt). Tubular fluorescent fixtures and lamps are preferred for ambient lighting in large indoor areas. In these areas, their low brightness creates less direct glare than incandescent bulbs.
Circular, tube-type fluorescent lamps are called circline lamps. They are commonly used for portable task lighting.
CFLs combine the energy efficiency of fluorescent lighting with the convenience and popularity of incandescent fixtures. CFLs fit most fixtures designed for incandescent bulbs and use about 75% less energy. Although CFLs cost a bit more than comparable incandescent bulbs , they last 6-15 times as long (6,000-15,000 hours).
CFLs work much like standard fluorescent lamps. They consist of two parts: a gas-filled tube, and a magnetic or electronic ballast. The gas in the tube glows with ultraviolet light when electricity from the ballast flows through it. This in turn excites a white phosphor coating on the inside of the tube, which emits visible light throughout the surface of the tube. Although CFLs are efficient and convenient to use, there are some challenges CFLs face and these include:
Premature CFL burnout: CFLs must last long enough for their energy efficiency to make up for their higher purchasing cost, what are the top three reasons for premature CFL burnout?
Disposal of CFLs: Like all fluorescent lamps, CFLs contain a tiny amount of mercury, which is needed to make the inert gasses conductive at all temperatures and to make the lamp work properly and efficiently. Mercury can be hazardous to the environment, so it is important to recycle your used CFLs rather than throw them away.
CFLs Full Brightness and Cold Temperature: CFLs can be used for outdoor applications. However, it is important to note that in cold weather, below 0°F, it will take 30 to 60 seconds for the bulb to reach full brightness. Optimum operating temperature is between 0°F and 100°F.
Could CFLs Work on Dimmers? - Yes! Although standard CFLs are not suitable for use with dimmer switches or other lighting controls, many CFL models are dimmable, as indicated on the package, and are and compatible with other lighting controls .
The chart below compares various type of fluorescent lighting
|Fluorescent Lighting Type||Efficacy
|Color Rendition Index
|Straight tube||30–110||7000–24,000||50–90 (fair to good)||2700–6500 (warm to cold)||Indoors/outdoors|
|Compact fluorescent lamp (CFL)||50–70||10,000||65–88 (good)||2700–6500 (warm to cold)||Indoors/outdoors|
Traditionally fluorescent lamps dominate the market for lighting commercial, institutional, and industrial spaces with ceilings less than 15 feet high. In recent years, however, the emergence of more intense and efficient fluorescent lamps coupled with specially designed reflecting fixtures has enabled fluorescent systems to break through the ceiling-height barrier and compete directly with High Intensity Discharge (HID) lamps in indoor applications. Most of today's fluorescent high bay fixtures use linear fluorescent lamps, either T8s or high-output T5s, because they provide longer life, higher efficacy, and less lumen depreciation than compact fluorescent lamps (CFLs) and twin-tube lamps. Better reflector designs allow fluorescent high bay lamps to be applicable at any height where an HID lamp is used. Although fluorescent high bay fixtures are available in a number of shapes, most modern fluorescent high-bay fixtures are square or rectangular.
The two pictures below shows the difference in illumination by traditional HID lamps (left) and Fluorescent High Bay (Right) in a school gym.
The two pictures below shows the difference in illumination by traditional HID lamps (left) and Fluorescent High Bay (Right) in a printing facility. The meters show the amount of light (measured in lumens) in each setting. The wattage in each light fixture was decreased from 400 watts to 256 watts when HID was replaced with Fluorescent High Bay.
Gas-discharge lamps are a family of artificial light sources that generate light by sending an electrical discharge through an ionized gas. Typically, such lamps use a noble gas (argon, neon, krypton and xenon) or a mixture of these gases. Most lamps are filled with additional materials, like mercury, sodium, and/or metal halides. In operation the gas is ionized, and free electrons, accelerated by the electrical field in the tube, collide with gas and metal atoms. Some electrons in the atomic orbitals of these atoms are excited by these collisions to a higher energy state. When the excited atom falls back to a lower energy state, it emits a photon of a characteristic energy, resulting in infrared, visible light, or ultraviolet radiation.
Gas-discharge lamps offer long life and high efficiency, but are more complicated to manufacture, and they require electronics to provide the correct current flow through the gas.
There are three groups of gas discharge lamp, namely:
Low-pressure lamps have working pressure much less than atmospheric pressure. They include:
High-pressure lamps operate under slightly less to greater than atmospheric pressure. They include:
The above three lamps are also well known as High Intensity Discharge (HID) lamps. The definition of high intensity discharge is related to the special type of electrode used in the lamps. Compared to other lamp types, relatively high arc power exists for the arc length.
High-intensity discharge (HID) lamps in general are very energy efficient and tend to have the longest service life of any lighting type. They can save 75%–90% of lighting energy when they replace incandescent lamps.
HID lamps use an electric arc (relatively high arc power for the arc length as compared to other lamp types) to produce intense light. Like fluorescent lamps, they require ballasts. They also take up to ten minutes to produce light when first turned on, because the ballast needs time to establish the electric arc. Because of the intense light they produce at a high efficacy, HID lamps are commonly used for outdoor lighting and in large indoor arenas. Since the lamps take awhile to establish, they are most suitable for applications where they stay on for hours at a time. They are not suitable for use with motion detectors. These are the three most common types of HID lamps:
We will explain each one in detail in the next section.
High pressure mercury vapor lamps (often called as mercury vapor lamps)—the oldest types of high-intensity discharge lighting—are used primarily for street lighting. Mercury vapor lamps provide about 50 lumens per watt. They cast a very cool blue/green white light. Most indoor mercury vapor lamps in arenas and gymnasiums have been replaced by metal halide lamps. Metal halide lamps have better color rendering and a higher efficacy. However, like high-pressure sodium lamps, mercury vapor lamps have longer lifetimes (16,000–24,000 hours) than metal halide lamps.
Significant energy savings are also possible by replacing old mercury vapor lamps with newer high-pressure sodium lamps
Metal halide lamps produce a bright, white light with the best color rendition among high-intensity lighting types. They are used to light large indoor areas, such as gymnasiums and sports arenas, and outdoor areas, such as car lots.
Metal halide lamps are similar in construction and appearance to mercury vapor lamps. The addition of metal halide gases to mercury gas within the lamp results in higher light output, more lumens per watt, and better color rendition than from mercury gas alone.
Metal halide lamps have shorter lifetimes (5,000–20,000 hours) compared to both mercury vapor and high-pressure sodium lamps.
High-pressure sodium lighting—a type of high-intensity discharge lighting—is becoming the most common type of outdoor lighting. High-pressure sodium lamps have an efficacy of 50–140 lumens per watt—an efficiency exceeded only by low-pressure sodium lamps. They produce a warm white light. Like mercury vapor lamps, high-pressure sodium lamps have poorer color rendition than metal halide lamps but longer lifetimes (16,000–24,000 hours).
It is also important to note that all high intensity discharge (HID) lamps, which include high pressure mercury vapor bulbs, metal halide and high-pressure sodium bulbs, are mercury-containing lightbulbs and should be recycled.
The chart below compares various types of high-intensity discharge lamps.
|High-Intensity Discharge Lighting Type||Efficacy
|Color Rendition Index
|Mercury vapor||25–60||16,000–24,000||50 (poor to fair)||3200–7000 (warm to cold)||Outdoors|
|Metal halide||70–115||5000–20,000||70 (fair)||3700 (cold)||Indoors/outdoors|
|High-pressure sodium||50–140||16,000–24,000||25 (poor)||2100 (warm)||Outdoors|
Light emitting diodes, commonly called LEDs, are real unsung heroes in the electronics world. Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material.
LEDs offer the potential for cutting general lighting energy use nearly in half by 2030, saving energy dollars and carbon emissions in the process. Their unique characteristics listed below are beneficial in many lighting applications including traffic lights, night lights, store signs, holiday lights, exit signs, flashlights, desk lamps and cooler display (saves cooling costs due to reduced heat output!):
The following video by Lithonia Lighting covers the basics of LED lighting technology and also reviews some basic terminology of lighting we have discussed earlier such as lumens, lighting efficacy, color temperature, etc.
To learn more on how LED works, click on this.
LEDs offer a huge variety of benefits but at the same time they cannot be viewed as the optimum solution for every lighting-related application. Some challenges faced by these devices include:
High Price: LEDs are currently more expensive, on an initial capital cost basis, than most conventional lighting technologies. However, when considering the total cost of ownership (including energy and maintenance costs), LEDs far surpass incandescent or halogen sources and begin to threaten compact fluorescent lamps.
Temperature Dependence: LED performance largely depends on the ambient temperature of the operating environment. Over-driving the LED in high ambient temperatures may result in overheating of the LED package, eventually leading to device failure. This is especially important when considering automotive, medical and military applications, where the device must operate over a large range of temperatures, and is required to have low failure rate.
Light Pollution: Light pollution occurs when too much artificial illumination enters the night sky and reflects off airborne water droplets and dust particles causing ' skyglow ', and consequently drastically limits the visibility of stars. The strong blue light emitted from cool-white LEDs scatters much more efficiently through Earth's atmosphere, compared to other colors . This means that cool-white LEDs can cause more light pollution than other light sources. It is therefore very important that cool-white LEDs are fully shielded when used outdoors. Compared to low-pressure sodium lamps, the blue light emission spike of cool-white and blue LEDs is scattered about 2.7 times more by the Earth's atmosphere. Cool-white LEDs should not be used for outdoor lighting near astronomical observatories. Evidence also shows that excessive artificial lighting disrupts the behavior patterns of nocturnal animals.
The following charts provide us with a summary of energy efficiency measured by lumens/watt of different types of lamps. Depending on the source of the information, lumens/watt reported for each type of lamps vary.
It is also very important to note that simply picking the most efficient lighting in terms of highest lumens per watt is not always the best choice. One has to always keep in mind the light quality and the applications, the video below provides a good example of factors to consider when making energy efficient lighting decisions!
As we learned from the video on last page, making an energy efficient lighting upgrade involves a number of considerations: lighting efficiency (lumens/watt), light output (lumens or footcandle), light quality (color temperature and CRI), frequency of use, and use of dimmers, etc. In addition, we have to do the math!
Yes, for businesses to make a change, they have to consider the capital investment (initial cost of purchasing the new bulbs or installation cost if any), the annual savings, the pay-back (how long it takes the annual savings to offset the capital investment) and return on investment (ROI). For business in general, they are not interested in any investment or proposal that has a payback of more than one year! In this section, we will discuss most common and widely applicable P2 opportunities in lighting and how to conduct a financial analysis of the P2 alternative!
Compact fluorescent light (CFL) bulbs are a great P2 alternative for halogen in places where lights are not frequently switched on and off! In a residential home, bathroom lights are frequently turned on and off, CFLs are therefore not suitable due to premature burn out. However, in hotels, most bathroom lights are on most of the time. In this case, replacing halogen with CFLs of warm color temperature (such as 2700 K or the choiced of the hotel people) presents a great P2 opportunity! In residential bathroom, we can replace with LED light bulbs that are not going to burnout despite frequent on and off.
Hotel Bathroom vs. Residential Bathroom
Some restaurants use halogen flood light that allows for illumination of bigger areas, these lights are usually on all the time when restaurants are open, therefore CFL flood lights with warm color temperature (such as 2700 K or the choice of the restaurant people) or LED flood lights are great P2 alternatives!
Many homeowners use outdoor lighting for decoration and/or security, such as shown below.
Many commerical buildings also use large amount of ourdoor lightings for security and/or decoration/attraction. Because outdoor lights are usually left on for a long period of time, using CFLs or LEDs in these fixtures will save a lot of energy. However, LEDs work better particularly for the following conditions:
1) In the cold climate where CFL bulbs take a long time to get to its full brightness.
2) Lights are on and off frequently, such as used with motion sensor for security reasons. LEDs will not have the premature burnout as CFLs will.
3) Lights are in places hard to reach, the extreme long life of LEDs will save significant labor cost in changing those bulbs in hard to reach places.
However, we need to be careful of light pollution concern of the cool-white LEDs. We need to make sure LEDs are fully shielded and not close to any astronomial observatories.
Before we get into financial analysis of lighting upgrade, let's clarify on a couple of terms: light fixture, bulbs or bulbs per fixture. A light fixture is an electrical device used to create artificial light and/or illumination, by use of one or more electric bulbs. For example, in the bathroom below, there are 2 light fixtures with 3 bulbs per fixture.
In the living room shown below, there is only one light fixture with 9 bulbs per fixture.
Now what is the financial implication of the energy efficient lighting upgrade (i.e. capital investment, annual savings, pay back)? How do we figure this out? Let's look at a couple of examples.
A large resort named "Wilderness Resort" (located not anywhere near astronomial observatories) has 280 light fixtures used with motion sensors for security reasons, each lighting fixtures has two bulbs as shown below.
These bulbs are 26 watts CFL flood light bulbs and are on an average of 8-hr/day, 365 days/year. The 26W bulb costs $10 each and lasts an average 3,000 hrs (Note the bulbs were rated as 8,000 hours, however, due to frequenty on and off, premature burnout results in an actual lifespan of 3000 hours). As a pollution prevention consultant, you are proposing to upgrade these bulbs to 13 watts LED that costs $13 each and lasts 40,000 hrs. Hotel pays 9 cents/kWh for electricity. CFL bulbs cost 0.75/bulb for proper disposal. You need to show the hotel manager the financial implication of the lighting upgrade. In another word, in your proposal, you need to answer:
1) What is the annual savings?
2) What is the capital cost? (Capital cost refers to initial cost of putting in a system)? Note a labor cost of $0.50 is assumed for each bulb changing.
3) What is the payback?
4) What is return on investment (ROI)?
1) First, we need to think through sources of annual savings? I will give you a minute....., then check the answer below:
There are a total of 4 sources of annual savings:
Now let's work on exact savings (or expense) occurred in a year (remember we are trying to figure out annual savings). Note some of the numbers shown below maybe a little off due to rounding effect.
a) Savings in electricity = cost of electricity for current CFL - cost of electricity for proposed LED
Cost of electricity = unit cost of electricity ($/kWh) x electricity consumption (kWh)
For current CFL:
Electricity consumption (kWh) = Watts × hours of operation/1000 = (26 watt x 2 bulbs/fixture x 280 fixtures)x 8 hr/day x 365 days/yr /1000 =42515.2 kWh
Cost of electricity = $.09/ kWh x 42515.2 kWh = $3,826
For proposed LED:
Electricity consumption (kWh) = Watts × hours of operation/1000 = (13 watt x 2 bulbs/fixture x 280 fixtures)x 8 hr/day x 365 days/yr /1000 =21257.6 kWh
Cost of electricity = $.09/ kWh x 21257.6 kWh = $1,913
Savings in electricity = $3,826 - $1,913 = $1,913
b) Savings (or expense) in purchasing replacement bulbs = cost of purchasing replacement bulbs for current CFL - cost of purchasing replacement bulbs for proposed LED
Note for every bulb in a fixture, number of replacement bulbs per year = Hours on per year /life of bulb.
For example, if a bulb needs to be on for 1000 hours a year, but the life of bulb is only 500 hours, then we need 2 (1000/500 = 2) bulbs in a year, right?
In this case, each fixture contains 2 bulbs, to factor this in, number of replacement bulbs per year per fixture = hours on per year/life of bulb x bulbs/fixture. So
For current CFL:
Number of replacement bulbs per year per fixture = [(8 hr/day x 365 days/year)/3000 hrs] x 2 bulbs/fixture = 1.947
Number of replacement bulbs = 1.947/fixture x 280 fixture = 545.07
For proposed LED:
Number of replacement bulbs per year per fixture = [(8 hr/day x 365 days/year)/40,000 hrs] x 2 bulbs/fixture = 0.146
Number of replacement bulbs = 0.146/fixture x 280 fixture = 40.88
One can easily tell, we will save lots of replacement bulbs if we use LEDs.
Some of you might wonder how can we replace part of a bulb in a fixture (notice the decimal in 1.947, for example)? good question! In reality, we don't, the replacement will actually happen one this year and another one early the following year, but we need to average or spread the cost of that replacement. So we will keep the decimal in our calculation.
Cost of purchasing replacement bulbs for current CFL = unit cost of the bulb x number of replacement bulbs = $10/bulb x 545.07 = $5,451
Cost of purchasing replacement bulbs for proposed LED = unit cost of the bulb x number of replacement bulbs = $13/bulb x 40.88 =$531
Savings in purchasing replacement bulbs = $5,451 - $531 = $4,919
c) Savings in labor involved in changing bulbs = cost of labor in changing CFL bulbs - cost of labor in changing LED bulbs
Since we need to change a bulb every time a bulb burns out, the number of bulb changing should equal the number of replacement bulbs. We have calculated number of replacement CFL bulbs (i.e. 545.07) and replacement LED bulbs (i.e. 40.88), see calculation under b) above. Therefore,
Cost of labor in changing CFL bulbs = $0.5/bulb changing x 545.07 bulb changing = $273
Cost of labor in changing LED bulbs = $0.5/bulb changing x 40.88 bulb changing = $20
Savings in labor involved in changing bulbs =$273 - $20 = $252
d) Savings (or Expenses) in disposal = disposal cost for the current CFL- disposal cost for the proposed LED
You have learned from other business that on average the disposal cost of CFL is $0.75/bulb.
Disposal cost for the proposed CFLs = $0.75/bulb x 545.07 replacement bulbs = $409
Disposal cost for the proposed LED = $0
Savings in disposal = $409 - $0 = $409 (the negative sign in savings implies that it is actually an expense)
Total annual savings = Savings in electricity + Savings in purchasing replacement bulbs + Savings in labor involved in changing bulbs + Savings (or Expenses) in disposal
= $1,913 + $4,914 + $252 + $409 = $7,488
2) Capital cost in this case involves purchasing cost of LED bulbs as well as the labor cost of each bulb changing
Capital Cost = cost of purchasing bulbs + labor cost of switching bulbs
= 280 fixtures x 2 bulbs/fixture x $13/bulb + 280 fixtures x 2 bulb changing/fixture x $0.50/bulb changing
= 280 x 2 x $13 + 280 x 2 x $0.5 = $7,280 + $280 = $7,560
3) Now we need to figure out pay-back. Remember pay-back is the time it takes for the the annual savings to offset the capital investment, therefore we can figure out pay-back using the following formula
In this case, the capital investment is the cost of switching bulbs which has been found to be $ 7,560. Annual savings were found to be $7,488
So payback (yr) = $ 7,560/$7,488 = 1.01 year
4) To calculate Return on Investment (ROI), we need to use the following formula:
In this case, ROI = 1/1.01 = 99%
As one can see, there is a lot of calculation involved in doing a financial analysis for a P2 upgrade! It is very easy to make a mistake in any steps of the calculation even if you get the approach right but simply put the wrong numbers done in calculator. Is there a better way to do this?
The answer is YES!
We will use EXCEL spreadsheet formula functions and linking between sheets functions to conduct financial analysis! In this approach, we need to set formula up in EXCEL, enter specifications such as life span of a lamp or operating hours, then EXCEL will do all the calculations! Not only this will eliminate errors in calculation as long as we use the right approach, it also present our financial analysis in a professional way!
We will use the next section to learn how to conduct a financial analysis using EXCEL!
The following videos show you how to conduct financial analysis using EXCEL spreadsheet, we will use Example #1 explained in last page as the example. I have also included written instructions below for your reference.
Video #1 - Introduction to lighting worksheet and setting up 'Specification sheet"
In this video, I will introduce you to lighting worksheet and how to set up specification sheet. You can download lighting worksheet under "Learning Module 1".
Under the title "Operation", we need to enter case-specific information such as number of fixture, hours on per day, days on per year, electricity price in $/kWh, etc; Note not every cell needs to be filled with information. The worksheet is meant to be a general form and one can certainly modify it to case-specific conditions. In addition, it is important to enter only "numbers" in the last column, text on units should be entered in the column under heading "Units".
Under the title 'Electrical Devices", we need to enter case-specific information for existing devices (such as CFL bulbs) and proposed devices (such as LED bulbs) including: bulbs per fixture; watts per bulb, etc;
For the time being, ignore the information under 'Environmental Impact".
There are some calculations that may need to be done under the "Specification" sheet. For example, "hours on per year" because this information will be needed when we calculate electricity consumption. We can use the formula function in EXCEL to do this. We know that "hours on per year" = "hours on per day" x "days on per year", we want EXCEL to do the calculation for us using Formula function, to do this:
(a) Click on the cell where the number for "hours on per year" should locate, in this case, cell "D12",
(b) then type in "="sign, click on the cell where data for "hours on per day" locates, in this case, cell "D10", notice, you should see "=D10" under formula bar as shown below:
(c) Then type in " * " for multiplication and click on the cell where data on "days on per year" locates which is "D11". You should see "=D10*D11" under formular bar and cell D12, as shown below:
(d) Hit 'Enter" key! Number "2920" shows up in cell D12 because 8 x 365 = 2920. EXCEL did the calculation for us! If we click on cell D12 now, we will see "=D10*D11" in formula bar as shown below. This tells us we have successful entered a formula of "D12=D10*D11" (which means "Data in D12" is calculated from "data in D10" multiply by "data in D11"). It is very important to only enter numbers (no text, no units) in the cells where calculation might be performed! EXCEL will treat cells with any letters/text as text and calculation using formula function can't work with text.
Video #2 - 'Specification sheet" continued (Another example of using EXCEL formula function)
In this video, we will continue working on the specification sheet. Another example of using formula function in EXCEL will be illustrated here.
Another calculation needed under the "Specification" sheet is the "Replacement bulbs per year per fixture". We learned that "replacement bulbs per year per fixture" = "Hours on per year"/"life of bulb" x "bulbs/fixture". Again let EXCEL do the calculation for us using Formula! Using "replacement bulbs per year per fixture" of CFL as an example,
(a) First, click on the cell where the number for "replacement bulbs per year per fixture" should locate, in this case, cell "D24",
(b) Then type in "="sign, click on the cell where data for "hours on per year" locates, in this case, cell "D12",
(c) Then type in"/" sign for division, click on the cell where data for "life of bulb" locates, in this case, cell "D23",
(d) Then type in "*" sign for multiplication, click on the cell where data for "bulbs/fixture" locates, in this case, cell "D19",
(e) Hit "Enter" key! Number "1.95" shows up in cell D24 because 2920/3000 x 2 = 1.95. EXCEL did the calculation for you! If we click on "1.95/cell D24" now, under the formula, we will see the equation/formula used to derive the number of 1.95 in cell D24 as shown below. This tells us we have successful entered a formula of "D24=D12/D23*D19" (which means that "data in D24" is calculated from "data in D12" divided by "data in D23" multiply "data in D19").
An Important Note on "Specification Sheet"
As a general rule, every piece of information that is used in the financial comparison should be found or derived from the specification sheet. If certain information was not included in the original Lighting Worksheet provided, we need to make sure we add that piece of information in the specification sheet. For example, if we propose to switch from CFLs to LEDs, there is going to be additional disposal cost associated with CFLs, so we need to add disposal cost of CFLs under the specification sheet.
Footnotes for specification sheet generally are not required. We may choose to add footnotes for our own reference for certain numbers if we think later on we may forget how those numbers are derived.
Video #3 - "Financial Comparison" sheet (I)
In this video, we will work on financial comparison sheet.
After completing the specification sheet, we are ready to do the financial comparison between existing system (i.e., CFL bulbs) and proposed system (i.e. LED bulbs), listed under the row headings. In terms of COST CATEGORIES, it includes CAPITAL COSTS and OPERATING COST (annual). Let's work on capital cost as an example:
Notice, capital cost for "Existing system" is always "Zero" since existing system is already in place (remember capital cost is the initial cost of putting in a system)
Capital costs for a proposed system include "Equipment", "Delivery and Installation", and "Other". In the case of Lighting Example 1, to upgrade to proposed LEDs, cost of LED bulbs would be equipment cost. LED bulbs need to be installed, so that cost should be listed under "Delivery and installation". If there is any other cost associated, we should put it under "Other". In previous page, we have explained that cost of purchasing bulbs is "number of fixtures (280) x bulbs/fixture (2) x cost per bulb ($13). Again we would like to use the "Formula" function in EXCEL to do the calculation. How? just like we did before with the specification sheet!
(a) First, click on the cell where the number for "Equipment cost of proposed system" should locate, in this case, cell "D6",
(b) Then type in "="sign, click on the cell where data for "number of fixtures" locates, in this case, it is under "Specification Sheet", so we click on "specification sheet", it is in cell "D8", so we click on cell "D8"
(c) Then type in"*" sign, click on the cell where data for "bulbs per fixture" of proposed system locates, in this case, cell "D27",
(d) Then type in "*" sign, click on the cell where data for "cost per bulb" locates, in this case, cell "D31", You should see "=Specification!D8*Specification!D27*Specification!D30" under formula bar. Notice it tells us which sheet each of the cell belongs to.
(e) Hit "Enter" key! Number "$7,280" shows up in cell D6 of the "Financial comparison" sheet because 280 x 2 x $13 = $7,280. EXCEL did the calculation for us even when data are in different sheets! If we click on cell D6 now, we will see "=Specifications!D8*Specifications!D28*Specifications!D31" in formula bar as shown below. This tells us we have successful entered a formula of "D6=Specifications!D8*Specifications!D28*Specifications!D31" (which means that "Data in D6" on 'Financial Comparison" sheet is calculated from "data in specifications sheet D8" times "data in specifications sheet D28" times "data in specifications sheet D31").
(f) One great advantage of using EXCEL formula function for calculation is that when there are changes in the specifications sheet, as long as the formula entered still holds true, the numbers on the financial comparison sheet will automatically be updated. This is a great feature since many data on the specification sheet are subject to change including price for electricity (or energy in general), price for labor and equipment, etc.
Video #4 -"Financial Comparison" sheet (II): Adding footnotes, textbox, add/delete a row/column, increase/decrease decimal places"
In this video we will work on adding footnotes and discuss a few details on EXCEL (including adding textbox, adding/deleting a row/column, increasing/decreasing decimal places showing up)
To make our presentation professional and also serve as a note to ourselves, we need to add footnotes. In another word, we need to tell the reader how this "$7,280" came about. To do this, we just need to:
(i) type in a letter for example "a" next to the number;
(ii) under the text box entitled "Footnotes", type in how we calculated "7,280" such as "a - 280 fixtures x 2 bulbs/fixture x $13/bulbs = $7,280".
Then, we should use the same approach to complete rest of the capital cost calculation and annual operating cost calculation with footnotes included for each number.
Now, let's talk about a few more details on EXCEL that you may have questions about:
1) How do I change decimal places in EXCEL? In EXCEL, calculation using formula carries all decimal places at all time (so it is very accurate), but we can choose how many decimal places to show up. To do this, under "Home" tab, go to the number tab on the top of the screen, on the right side, click on ".00-->.0" to show fewer decimal places and click on ".0 -->.00" to show more decimal places".
2) How do I add textbox/footnotes in EXCEL? Under "Insert", click on "Textbox", the dropdown menu allows you to choose either "horizontal textbox" or "vertical textbox", click on the choice you desire, then draw on the screen with your mouse a rectangular shaped textbox, type inside the textbox. You can also move the textbox to where you want it to be by dragging and moving on the edge of the textbox.
3) How do I add/delete a row/column in EXCEL? To add/delete a row, move your mouse to where you want the additional row to be or where the row to be deleted is, click on the very left side of the row till you see the cursor becomes an little arrow pointing to right, left click on your mouse, this will highlight an entire row, right click to show the dropdown menu. Choose "insert" to add a row; choose "delete" to delete a row. To add/delete a column, move your mouse to where you want the additional column to be or where the row to be deleted is, click on the very top of the column till you see the cursor becomes an little arrow pointing down, left click on your mouse, this will highlight an entire column, right click to show the dropdown menu. Choose "insert" to add a column; or "delete" to delete a column. Note that adding/deleting a row or column in the above way will not affect the formula that connects data on the "Specifications" sheet with the "Financial Comparison" sheet. EXCEL automatically updates the new cell numbers in the formula (How Smart!)
4) How do I add a border to a cell/table in EXCEL? First highlight the cell or tables where you want the border to be around (and/or within), under "Home", under "font" tab, click on the little triangle next to a square, a dropdown menu will show up and you can pick the type of "border" you desire.
Completed Capital Costs and Operating Costs of Example #1 is shown below.
Video #5 -"Financial Comparison" (III): Payback and ROI
In this video, we will work on calculating payback and ROI.
The last two things we need to work on is "Payback period for proposed system (year)" and "Return on Investment (%)". To figure out payback and ROI, we need to know the total savings from the proposed system on operating costs. To calculate 'Total", we can take advantage of the "Auto Sum" function in EXCEL. To do this,
a) Click on the cell where data for "Total" will appear, such as cell "B20" for total operating cost of existing system.
b) Click on the "AutoSum" icon located on the upper right corner. Highlight all cells where data need to be added, in this case, B12 through B18. Note in the formula bar, we see "=SUM(B12:B18)", as shown below.
c) Press "Enter" key! Use the same approach, we can find "total of proposed system" on operating costs and "total of savings from proposed system" on operating cost.
d) To figure out payback, since we already figured out "total capital cost" (in cell D9) and "total savings from proposed system" (in cell F20"), we just need to enter the formula "=D9/F20".
e) To figure out ROI, since we already figured out payback (in cell D29), we just need to enter the formula "=1/D29". The completed financial comparison should look like below:
The above completed Excel worksheet for Example #1 can be found under Unit 3 learning resources by the name of "Lighting Example 1".
An interesting question to think about....
Is it possible to have a negative operational saving for a proposed P2 option? Yes, absolutely! It is important to remember not every P2 alternative will make financial sense, that is why we have to do a financial analysis for each P2 alternative! If we do come across with a P2 alternative that resulted in a negative operational saving, EXCEL will tell us we have a negative payback! (payback = capital cost (a positive number)/annual savings (a negative number)). A Friendly Note On EXCEL: When you get a negative number in EXCEL, it automatically puts the number in parentheses.
What does a negative payback in EXCEL mean? Let's go back to the basic...when we have a negative operational saving, it means after we spend some money up front as capital, we continue to lose money each year afterwards, are we ever going to offset the initial capital investment? ......give you 2 seconds..... NEVER!!!
If you encounter such a situation on your job, make sure you write a note next to the negative payback calculated from EXCEL that "There will never be a pay-back moment for this P2 alternative!". EXCEL will also tell us that we have a negative ROI implying we are losing money with this investment and unfortunately it is TRUE!
Tubular fluorescent lamps are widely used for indoor lighting in commercial, institutional, industrial and even residential spaces with ceilings less than 15 feet high.
Depending on the diameter of the lamp, tube fluorescent lamps are usually identified as T12, T8 and T5 (12/8, 8/8 and 5/8 of an inch tube diameter).
As interest in energy saving technologies has grown and become popularized, these codes have come to designate levels of energy efficiency, instead of merely indicating lamp tube diameter. In general,
Retrofitting T12 with T8 or T5 not only result in significant energy saving (typically greater than 40%) but also improves the quality of lighting! T5 is the most efficient lamps among the three, however, it is important to look at the application and determine the cost benefit of T5 over T8 in order to determine if the increased efficiency of T5 justifies the substantial increase in initial and long term maintenance costs. The standard 32 watt T8 and an electronic ballast with a low temperature rating, are proven performers in a wide array of extreme applications. The systems are tried, tested and true in parking garages, factories, extreme cold environments and the list goes on. T5's don't have the track record in extreme applications. It is believed that the manufacturers are still "working out the bugs" as the largest portion of our warranty work involves defective T5 lamps and ballasts.
Furthermore, T8 lamps and ballasts are now commodity items and can be purchased at low costs. T5 is still a premium product, whose research and development costs haven't even been fully realized, let alone the process to produce low cost, highly reliable, replacement parts.
High bay fluorescent is a great P2 alternative for metal halide! In recent years, both HID and high bay fluorescent technologies have improved, but high bay fluorescent technology has retained a performance edge in most applications, and it continues to gain market share. The improvements in fluorescent lamps and the emergence of new high bay fluorescent fixtures have made fluorescent lighting the most cost-effective choice for lighting high indoor spaces. These high bay fluorescent systems are more energy-efficient than HID solutions and feature lower lumen depreciation rates, better dimming options, virtually instant start-up and restrike, better color rendition, and reduced glare.
In this section, we will discuss some interesting developments in lighting and other miscellaneous information about lighting.
Induction lamps are basically fluorescent lamps without electrodes. Current is induced through electromagnetic field. The induction lamps are slightly more efficient than fluorescent lamps but with much longer bulb life of 65,000 to 100,000 hours. These benefits offer a considerable cost savings of between 35% and 55% in energy and maintenance costs for induction lamps compared to other types of commercial and industrial lamps such as high pressure sodium (HPS) lamps or metal halide lamps which they replace.
The following video explains the technology behind induction lighting.
Below are some induction lighting case studies that shows the before and after effect when HPS lamps are switched to induction lamps in tunnels, gyms, warehouses and industrial settings.
So far we have discussed saving energy for lighting by using more efficient lamps. But there is another strategy that can be just as effective at saving energy and money: turn lights off when they aren't needed. Remembering to do that, however, is often easier said than done. Fortunately there are a number of simple, inexpensive lighting controls - both automatic and manual - that will turn lights on and off, helping you to reduce your energy costs. We will discuss here:
A simple automatic timer can control when and how long a light stays on. It can be located at a light switch (as shown below), at the wall plug or in a light socket. A timer will turn lights on and off on at prearranged times. This can prevent inadvertently leaving lights on all night, for example, and a timer can turn on a light before you get home in the evening. By automatically turning lights on and off for you, timers can give your home the appearance of being occupied - a valuable safety precaution when you're away.
Photosensors measure light levels and turn on lights when it gets dark. These are particularly effective with lights that stay on all night - outdoor security lights or even small night-lights inside.
If your primary need for outdoor lighting has to do with security, or for a few minutes of light now and then when you're putting out the trash or letting the dog in, motion detector controls might be a good investment. Motion detectors sense the motion of somebody walking up or driving within range of the detector and activate a switch to turn on the lights. Most can be set to keep the lights on for a specific period of time, such as three, five or ten minutes. The better products also include manual override features. The savings possible by installing motion-detector controls depends on how long the lights would be left on unnecessarily without these devices.
Occupancy sensors sense occupancy of a space. These sensors replace a standard light switch and automatically turn lights on or off depending on the occupancy/vacancy of the space. Occupancy sensors save energy during periods when a space is unoccupied. There are three mechanisms for these sensors to detect occupancy:
To apply occupancy sensor properly, we need to consider a number of factors including:
The video below shows how UC, Davis improves its lighting efficiency by application of lighting control and LEDs.
A warehouse is considering installing motion sensors in each aisle. They estimate that any one aisle is accessed, on average, 3 times over a 24 hour period. It takes about 15 minutes to complete each access activity. Each aisle is served by 10, T5 high bay fixtures (4 bulbs per fixture), each bulb uses 70 watts and lasts 10,000 hours. Lights are on 24/7 all year around. There are a total of 20 aisles. The passive IR sensors cost $60 plus $40 installation. What is the expected payback? Electricity costs 8c/kwh. Replacement bulbs cost $4 and changing a burned out bulb costs $2 in labor. Recycling bulbs will cost $0.50/bulb.
General Approach: The savings will come from reduced hours of operation for these lights. What would reduced hours of operation save, exactly?
Hours of operation is a key number, it allows calculation for # of replacement bulbs per year per fixture, and consequently savings in purchasing replacement bulbs, labor involved in changing bulbs and disposal cost of burned out bulbs.
Now can you figure out hours of operation (hours on per year, remember we are trying to figure out annual savings) for the existing and proposed system?
Without the sensor, hours of operation = 24 hr/day x 365 days/year = 8760 hours on per year
With the sensor, the lights will only be on when there is an access activity. On average, 3 access activities over a 24 hours and each take 15 minutes, i.e. 3 x15 minutes/24hr or 0.75hr/24hr (i.e. 0.75/24 of the existing hours of operation, note we need to convert unit for time)
Therefore, with the sensor, hours of operation = 0.75/24 x existing hours of operation = 0.75/24 x 8760 hours on per year = 273.8 hours on per year
Now let's work on exact savings or expense (i.e. disposal cost) occurred in a year (remember we are trying to figure out annual savings)
a) Savings in electricity = cost of electricity for existing - cost of electricity for proposed
Cost of electricity = unit cost of electricity ($/kWh) x electricity consumption (kWh)
For existing T5:
Electricity consumption (kWh) = Watts × hours of operation/1000 = (70 watts/bulb x 4 bulbs/fixture x 200 fixtures) x 8760 hrs/yr/1000 =490560 kWh
Cost of electricity = $.08/ kWh x 490560 kWh = $39,244.80
For proposed "T5 with motion sensor":
Electricity consumption (kWh) = Watts × hours of operation/1000 = (70 watts/bulb x 4 bulbs/fixture x 200 fixtures) x 273.8/yr/1000 =15330 kWh
Cost of electricity = $.08/ kWh x 15330 kWh = $1226.40
Savings in electricity = $39244.80 - $1226.40 = $38018.40
b) Savings (or expense) in purchasing replacement bulbs = cost of purchasing replacement bulbs for existing - cost of purchasing replacement bulbs for proposed
Note the number of replacement bulbs per year per fixture = hours on per year/life of bulb x bulbs/fixture. So
Number of replacement bulbs per year per fixture = [(8760 hrs/year)/10000 hrs] x 4 bulbs/fixture = 3.5
Cost of purchasing replacement bulbs = unit cost of the bulb x number of replacement bulbs = $4.00/bulb x 3.5 replacement bulbs per year per fixture x 200 fixtures = $2803.20
For proposed (with motion sensor):
Number of replacement bulbs per year per fixture = [(273.8 hrs/year)/10,000 hrs] x 4 bulbs/fixture = 0.11
Cost of purchasing replacement bulbs = unit cost of the bulb x number of replacement bulbs = $4.00/bulb x 0.11 replacement bulbs per year per fixture x 200 fixtures = $87.60
Savings in purchasing replacement bulbs = $2803.20 - $87.60= $2715.60
c) Savings in labor involved in changing bulbs = cost of labor in changing bulbs for the existing - cost of labor in changing bulbs for the proposed
Since we need to change a bulb every time a bulb burns out, the number of bulb changing should equal the number of replacement bulbs. Therefore,
Cost of labor in changing bulbs for existing = $2.00/bulb changing x 3.50 bulb changing per year per fixture x 200 fixtures = $1401.60
Cost of labor in changing bulbs for proposed = $2.00/bulb changing x 0.11 bulb changing per year per fixture x 200 fixtures = $43.80
Savings in labor involved in changing bulbs =$1401.60 - $43.80 = $1357.80
d) Savings (or Expenses) in disposal = disposal cost for the existing - disposal cost for the proposed
Disposal cost for the existing = $0.50/bulb x 3.50 replacement bulbs/yr/fixture x 200 fixtures = $350.40
Disposal cost for the proposed = $0.50/bulb x 0.11 replacement bulbs/yr/fixture x 200 fixtures = $10.95
Savings in disposal = $350.40 - $10.95 = $339.45
Total annual savings = Savings in electricity + Savings in purchasing replacement bulbs + Savings in labor involved in changing bulbs + Savings (or Expenses) in disposal
= $38018.40+ $2715.60 + $1357.80 + $339.45 = $42,431.25
e) Capital cost in this case involves purchasing and installation cost of the motion sensors.
Capital Cost = cost of purchasing motion sensor + installation cost
= 20 aisles x 1 sensor/aisle x $60/sensor + 20 aisles x 1 sensor/aisle x $45 installation cost/sensor = 20 x 1 x $60 + 20 x 1 x $45 = $1200 + $900 = $2100
f) Now we need to figure out pay-back. Remember pay-back is the time it takes for the the annual savings to offset the capital investment, therefore we can figure out pay-back using the following formula
In this case, the capital investment is the cost of switching bulbs which has been found to be $ 2100. Annual savings were found to be $42,431.25
So payback (yr) = $2100/$42,431.25= 0.049 year = 0.049 year x 12 months/year = 0.59 months
g) To calculate Return on Investment (ROI), we need to use the following formula:
In this case, ROI = 1/0.049 = 2021%
The completed Excel worksheet for above example can be found under Unit 3 learning resources by the name of "Lighting Control Application 1".
In a small office building, the photocopy room is used about 10 minutes out of each hour. Lights (two T8 fixtures each using 150 watts) are on during normal business hours (8 hrs a day for 5 days a week and 52 weeks a year). The company is considering buying and installing a motion sensor through Actonenergy.com. It will cost about $10 to install. What is the expected payback?
The savings will come from reduced hours of operation for these lights. What would reduced hours of operation save, exactly?
Hours of operation is a key number, it allows calculation for # of replacement bulbs per year per fixture, and consequently savings in purchasing replacement bulbs, labor involved in changing bulbs and disposal cost of burned out bulbs.
Now can you figure out hours of operation (hours on per year) for the existing and proposed system?
Without the sensor, hours of operation = 8 hr/day x 5 days/week x 52 weeks/year = 2080 hours on per year
With the sensor, the lights will only be on when the photocopy room is being used, i.e. 10 minutes/hr or 10 minutes/60 minutes (i.e. 1/6 of the existing hours of operation, note we need to convert unit for time)
Therefore, with the sensor, hours of operation = 1/6 x 8 hr/day x 5 days/week x 52 weeks/year = 346.7 hours on per year
You should be able to figure out the rest, similar to Lightig Control Application #1, right?
Daylight is the ideal light source, both in terms of quality and energy use. A single skylight provides as much light as a dozen or more light bulbs, and the light quality is unsurpassed. Many people feel that exposure to natural daylight is conducive to good health. But one also must adjust electric lighting based on solar input and control heat loss/gain.
The above picture shows you an application of skylights in Wal-Mart. As a matter of fact, Wal-Mart is doing quite a bit with skylight/dimming system:
Skylights and windows have to be designed carefully so they don't contribute to overheating. The potential for overheating from skylights will vary, depending on the orientation of your house and direction your window is facing. In northern hemisphere, south-facing windows with large overhang (as shown below) allows daylight come through but minimizes overheat in the summer. In the winter, these overhang will not block sunlight due to more slanted angle of sunlight so that the building could still harvest passive solar energy for space heating. In Sunridge Middle School at Pendleton Oregon (as shown below), the entire south-facing wall is practically all windows with green-colored overhang! South-facing skylights on relatively steep roofs will generally not lead to overheating because the sun never shines directly down onto them. Skylights placed elsewhere may need some exterior shading placed over them in the summer. Greenhouse shading material is commonly used for this purpose.
A solar tube is a small clear dome on the roof that allows sunlight to enter a highly reflective tube that guides sunshine to ceiling. A translucent diffuser lens gently disperses natural light throughout a room. Compared to a skylight, a solar tube results in less heat loss/gain, less roof penetration and construction work to install.
The following video shows the amount of energy savings from solar tubes, typical applications in a residential home and how to install a solar tube!
The following video explains how hybrid fiber optic lighting works and the typical amount of energy it uses.
As you see in the above video, fiber optic wire connects solar collector to in-room light fixture. Combined with existing electric lighting, hybrid solar lighting delivers the benefits of the natural lighting with the convenience and reliability of artificial light!
If we compare a lighting fixture to a shower head, then the lumen output is the rate of flow of water and illuminance is the amount of water collected in a bucket at a given time. The key point is that the same total flux can give different amounts of water in the bucket, simply by moving the bucket, or by changing the spray pattern or by changing any physical obstructions between the source and the bucket. Total flux doesn't specify how much illuminance will be provided where it's needed. This is true, in part, because the luminaire, reflectors, lenses and other optical media can greatly affect the flow of light from the source to the surface of interest. Failure to remember this is a frequent cause of poor lighting design, especially in retrofit applications.
For example, the picture on the left shows an incandescent lamp on the left being replaced by a compact fluorescent lamp on the right. Here, a wide adapter ballast is used. The ballast blocks out most of the direct light from the lamp to the work surface. The distributions of light are completely different in the two cases. The result is significantly less illumination on the work surface than what one might expect from comparisons of total lumen output. Thus, lighting distribution is an important parameter for the performance of lighting systems.
The picture below is an example of efficient light distribution to the workstation. Notice the design of the fixture/reflector allows most of light be focused on the mailboxes as opposed to distributed to the ceiling.