Cost Effectiveness and Illumination of CFL, LED, and Incandescent Bulbs through Inverse Square Law

Sigma Xi Federal Chapter and SECTA Award (View Award Page)

Effectiveness of CFL and LED Bulbs is a science project focused on proving whether CFL and LED bulbs are really as superior to incandescent bulbs as advertised. The hypothesis is, If CFL Bulbs are really as environmentally friendly, energy efficient and cost effective as they are advertised, then CFL bulbs will perform superior to traditional light bulbs and LED’s in a series of experiments focused on energy efficiency, environmentally friendliness, energy lost, illumination produced and cost effectiveness. In the experiment, the conductors measured illumination produced; energy lost and cost effectiveness of CFL bulbs, traditional bulbs and LED Bulbs. Side effects of using each type of bulb were also evaluated.

Three main experiments were performed.  The first experiment focused on brightness. Conductors used the inverse square law to compare the brightness of a CFL and LED bulb compared to the incandescent bulb. The second experiment focused on the amount of heat lost.  The third experiment focused on the cost effectiveness of incandescent, CFL and LED bulb. The initial cost and operating cost were considered to figure which bulb is most cost effective.

It was proved that the CFL bulb, as advertised, was the best. It produced more illumination than the incandescent and LED, lost the least amount of energy and was the most cost effective. The incandescent was proved to be the least energy efficient.            

Experiment 1

Hypothesis

The hypothesis of experiment one is: if a Jolly Photometer is used to compare the light intensity of a 40 Watt control bulb & 490 lumens with a 10 Watt CFL & 520 lumens and a 8 Watt LED bulb & 430 lumens, then the CFL bulb will produce more light than the control and the LED will produce less light than the control. This is because the CFL produces 520 lumens which is more than the control and the LED produces 430 Lumens which is less than the control.

The materials for the experiment:

• Box of paraffin blocks
• Aluminum foil
• Scissors
• Knife
• One 40 watt incandescent bulb
• One 8 Watt LED bulb
• One 10 Watt CFL bulb
• 2 Power source (Lamp)

Procedure:

1. Make a Jolly Photometer
2. Place the light control 39 centimeters away from aluminum foil.
3. Light one of other bulbs on other side of photometer (make sure there is no other light in room and that photometer is in straight line with bulbs).
4. Move either CFL or LED bulb until the light intensity of both bulbs are equal.
5. Use the Inverse Square Law to figure out light intensity of either CFL or LED bulb when compared to incandescent.

Variables

• Independent variable — Type of bulb
• Dependent variable — Distance from the photometer & light intensity.

Controls

• All bulbs were 40 watt (equivalents)
• Photometer, bulb 1 and bulb 2 were in a straight line and at same heights;
• All the bulbs used the same source of energy.

Data Analysis:

Bulb Type vs. Distance from Photometer (Experiment 1)

Second Experiment

Hypothesis

The hypothesis of the second experiment is:  if an incandescent, CFL and LED bulb is each tested for the amount of heat lost, then the CFL bulb will lose the least heat, because it is labeled to be the most efficient bulb in the market.

The materials used are:

• Power Source (lamp)
• Four Pillows
• Cardboard box
• Temperature measuring clock
• One 40 watt incandescent bulb
• One 8 watt LED bulb
• One 10 watt CFL bulb
• One 2500 mL container

Procedure:

• Put a bulb into lamp socket
• Put container around bulb
• Put a temperature measuring clock at end of container and record starting temperature.
• Put the cardboard box on top of the lamp.
• Put four pillows around the cardboard box.
• Turn on the lamp and wait 20 minutes.
• Note the ending temperature when time is up.
• Calculate temperature change and percent of change (Percent of heat lost).
• Find the increase in calories with equation (Heat change = Specific heat * Mass of container * Temperature change).

(Since specific heat and Mass of container are same, increase in calories is directly proportional to temperature change).

Variables:

• Independent variable : Type of bulb
• Dependent variable: Increase in temperature.

Controls:

• The temperature of each bulb was tested after exactly 20 minutes;
• All bulbs were supplied from the same energy source;
• All bulbs were in the same environment;
• All temperatures were measured with an electric Casio temperature clock

Data Analysis:

Bulb vs Amount of Heat Lost (Experiment 2)

Study: Cost Effectiveness:

In this analysis, the total cost (the running cost and the initial cost) was compared over 5 years, 10 years, 15 years, and 50 years. It was proved that incandescent bulb was always more expensive than the LED and CFL bulbs. The CFL bulbs were always the most cost effective.

Data Analysis

Sample Calculation–for 5 years–of Efficiency Data

Years vs. Total Cost

Results:

• Experiment one – 10 watt CFL bulb had 102.58% intensity of the 40 watt incandescent control, and the 8 watt LED had 42.75% intensity of the 40 watt incandescent light bulb.
• Experiment two – 40 watt incandescent light bulb lost 72.62% of its heat, the 10 watt CFL lost 5.22% or its heat, and that the 8 watt LED lost 10.29% of its heat.
• Cost effectiveness analysis – CFL bulb is most cost effective over 5, 10, 15 and 50 years of usage.

Conclusion:

It was proved that the CFL bulb, as advertised, is the most cost effective bulb in today’s market.  The LED was supposed to be less energy consuming than the other bulbs, but considering low illumination and high cost, the overall cost increases significantly.  In the first experiment, it was proved that the 10 watt CFL produced more light than the 40 watt control. It was also proved that the 8 watt LED produced less light than the control. In experiment two, it was proved that that the more heat is produced, overall energy consumption for same illumination will increase; the incandescent bulb lost the most heat and the CFL lost the least heat.  CFL bulbs, however, is not as environmental friendliness as the other two bulbs since it contains Mercury, a chemical dangerous to our environment. 

Sources of Error:

There are many things that may have gone wrong. In experiment one, the measured distance might have been wrong. Also, because the surface on which was photometer was not flat, the results may have been skewed. Finally as always, there may have been human error in calculation.  In experiment two, the temperature might not have been accurately measured, some heat lost might have not been measured by thermometer, and the measured time might not have been exactly 20 minutes.  Finally, there is always human error. 

Future uses:

In the future, this experiment will help reduce the amount of energy consumed. This will result in lesser waste in our landfills and will eventually make our planet greener. People will also save money because they will buy the CFL bulbs instead of incandescent.

The hypothesis,  If CFL Bulbs are really as environmentally friendly, energy efficient and cost effective as they are advertised, then CFL bulbs will perform superior to traditional light bulbs and LED’s in a series of experiments focused on energy efficiency, environmentally friendliness, energy lost, illumination produced and cost effectiveness was supported. The hypothesis for experiment one, If a Jolly Photometer is used to compare the light intensity of a 40 Watt control bulb & 490 lumens with a 10 Watt equivalent & 520 lumens and an 8 Watt LED bulb & 430 lumens, then the CFL bulb will produce more light than the control and the LED will produce less light than the control. This is because the CFL produces 520 lumens which is more than the control and the LED produces 430 Lumens which is less than the control, was supported. The hypothesis for experiment 2, If an incandescent, CFL and LED bulb is each tested for the amount of heat that is lost, then the CFL bulb will lose the least heat, because it is labeled to be the most efficient bulb in the market, was also supported.