Energy Calculation Worksheet v4 · PDF fileEnergy Calculation Worksheet !! 1 The Quality Lighting Teaching Kit’s Energy Calculation Worksheet !!! Usethe$worksheet$with$thedouble"sided%“Energy%Calculation

Energy Calculation Worksheet

1

The Quality Lighting Teaching Kit’s


Use the worksheet with the four “Energy CalculationMat” posters or inplace of the “Energy Calculation Mat”. Start by looking over the “LightPollutionandEnergy”poster.ThendothecalculationsonSides1and2ofthemats.Thenreviewthedocument“TypesofLights”.ThatresourcewillhelpstudentswiththeselectionoflightstocarryoutcalculationsonSides3and4ofthemats.


2

You will use the information on this page and the results from counting the squares on the city grid to determine the energy, cost, and carbon footprint of the lights from this city.

For all bulbs: Cost of electricity per kilowatt-hour:

This will depend on how your region produces electricity. For Houston, the average is $0.08 per kWh.

All bulbs will be turned on for 11 hours per night.

There are 2,000,000 bulbs in this city.

The total number of squares on the grid is 1,344.

Note: In this document, a comma (,) is used for the thousands (or millions) place in large numbers and a period (.) is used for the decimal place. In many countries, this is reversed. Don’t let this confuse you!

$0.08

250

22,000

Wattage of the bulbs:

Lumens of light:

Number of squares:

Bulb Type 1: Metal Halide

250

24,000


Lumens of light:

Number of squares:

Bulb Type 2: High Pressure Sodium

150

16,000


Lumens of light:

Number of squares:

Bulb Type 3: High Pressure Sodium

NumberofsquaresofBulbType1


NumberofLitSquares


+


3

Use the numbers in the colors above to complete the next section of this worksheet. Repeat these steps for each type of bulb.

For this first set of calculations we will use Bulb Type #1. First we will find the efficacy of each bulb. The efficacy is the ratio of lumens to watts. The efficacy is related to the efficiency, but they are not the same thing. A larger efficacy means the bulb is more efficient. Which of the bulbs has the highest efficacy?

Step 1

LumensofType1

EfficacyofType1WattageofType1

÷ =

Step 4

WattageofType1

Energyusedinonenightbyone

bulbofType1

Hoursinonenight

=×11

We want to determine what percent of all lights are of Type 1. To do this, we’ll take the number of squares of Type 1 and divide it by the total number of lit squares.

In this next step, we will find the energy used in one night. Electric utility companies measure energy in a unit called watts. For example, if you have a 100-watt bulb and the light is on for 11 hours it uses 100W*11 hours or 1,100Wh). To calculate the amount of energy used, the wattage (in watts) of the bulbs is multiplied by the number of hours the light is on per night. Watts is the unit of power, which is the rate of energy over time. By multiplying power by time (e.g., 11 hours), you end up with energy.

Step 2

NumberofsquaresofType1

Totalnumberoflitsquares

Percentoflightsthatare

Type1

÷=

Step 3

PercentoflightsthatareType1

NumberofbulbsofType1inthe

city

Totalnumberoflightsinthe

city

×2,000,000=

Now we want to determine how many bulbs of Type 1 are in the city. To do this, we’ll take the percent of Type 1 and multiple it by the total number of lights in the city (2,000,000).


4

Now let’s take a closer look at energy, cost, and carbon footprint.

Because of how quickly watt-hours add up, the term kilowatt-hour is used to represent 1000 watt-hours. You can convert the number of watt-hours to kilowatt-hours by dividing the number of watt-hours (or energy) by 1000. This is the amount of energy used in one night.

An important part of light pollution is the enormous cost of that is required to keep the lights turned on. Electric utility companies charge for electricity by the kilowatt-hour (kWh). Next we will calculate how much it costs to light up one bulb of Type 1 for one night.

Electricity is most commonly produced from coal, natural gas, or nuclear power. When chemicals are burned, greenhouse gases are emitted that contribute to air pollution and climate change. The final important aspect of light pollution is the amount of greenhouse gases that are emitted during the production of electricity. Greenhouse gases are measured by the mass of the carbon dioxide gas. The amount of greenhouse gases produced depends on the type of fuel used to produce electricity. Because that’s hard to know exactly, we’re going to use an average of 0.84 kg per kilowatt-hour. To calculate how much greenhouse gas is produced, you need to multiply the kilowatt-hours used in one night by 0.84kg/kWh.

Step 5

÷1000=


bulbofType1

Kilowatt-hoursusedinonenightforone

bulbofType1

Step 6


bulbofType1

×=$0.08

Costperkilowatt-hour

AmountspentononebulbofType1inone

night

Step 7

×0.84 !"!"!

=Kilowatt-hoursused

inonenightforonebulbofType1

Amountofgreenhousegasproducedbyonebulbof

Type1inonenight


5

Now let’s determine how much energy, cost, and carbon footprint is used for the entire city in one night. To do this, we’ll multiply the results from the previous page for one bulb by the total number of bulbs we calculated in Step 3.

Now let’s determine how much light is being wasted by shining up into the sky. Roughly 30% of the light used is wasted. We’ll multiply the results from the above steps by 30% or 0.3 to determine the wasted light.

Step 8

×=


bulbofType1

Kilowatt-hoursusedinonenightforallbulbsofType1


city

Step 9

×=

Amountspentinonenightforonebulbof

Type1

AmountspentinonenightforallbulbsofType1


city

Step 10

×=

Amountofgreenhousegasproducedinonenightfor

onebulbofType1

Amountofgreenhousegasproduced

inonenightforallbulbsofType1


city

Step 11

×0.3== Kilowatt-hourswasted



Step 12

×0.3=

AmountwastedinonenightforallbulbsofType1

Amountspent


Step 13

×0.3=

Amountofgreenhousegaswastedinonenightforallbulbs

ofType1

Amountofgreenhousegasproducedinonenightforall

bulbsofType1


6

Now let’s repeat the steps for Bulb Type 2.

Step 1

LumensofType2


÷ =

Step 4

WattageofType2


bulbofType2

Hoursinonenight

=×11

Step 2




Type2

÷=

Step 3



city


city

×2,000,000=

Step 5

÷1000=


bulbofType2


bulbofType2

Step 6


bulbofType2

×=$0.08



night

Step 7

×0.84 !"!"!

=Kilowatt-hoursused



Type2inonenight


7

Step 8

×=


bulbofType2



city

Step 9

×=


Type2



city

Step 10

×=


onebulbofType2




city

Step 11




Step 12

×0.3=


Amountspent


Step 13

×0.3=


ofType2


bulbsofType2


8

Now let’s repeat the steps for Bulb Type 3.

Step 1

LumensofType3


÷ =

Step 4

WattageofType3


bulbofType3

Hoursinonenight

=×11

Step 2




Type3

÷=

Step 3



city


city

×2,000,000=

Step 5

÷1000=


bulbofType3


bulbofType3

Step 6


bulbofType3

×=$0.08



night

Step 7

×0.84 !"!"!

=Kilowatt-hoursused



Type3inonenight


9

Step 8

×=


bulbofType3



city

Step 9

×=


Type3



city

Step 10

×=


onebulbofType3




city

Step 11




Step 12

×0.3=


Amountspent


Step 13

×0.3=


ofType3


bulbsofType3


10

Next, let’s look at our city as a whole and calculate the total amount of energy, money, and greenhouse gases wasted each night.

Energy Wasted (kWh): Cost Wasted ($): Carbon Footprint Wasted (kg):

Bulb Type 1:

Bulb Type 2:

Bulb Type 3:

Grand Total:

+


11

Now the challenge is to minimize the energy consumed, the cost and the carbon footprint by using more energy efficient types of lights, lowering the number of bulbs of each type and there-fore the total number of bulbs, lowering the number of hours they are on and any other means you have found in your research (e.g., the “Light Pollution & Energy” poster and the “Types of Lights” document). After determining the numbers on this page, use them to recalculate the energy, cost and carbon footprint from pages 2 through 10 above. Then on the next page or Side 4 of the final section of Energy Calculation Mat, take the difference of the numbers from your first set of calculations and the second set of calculations. That will give you how much energy, cost and carbon footprint you have saved.

For all bulbs: Cost of electricity per kilowatt-hour does not change:

This will depend on how your region produces electricity. For Houston, the average is $0.08 per kWh.

Changes you can make, but justify your choices:

❏ Choose a number between 4 and 10 hours per night for the hours lights are turned on.

❏ For each bulb type, choose the number of squares to be more than half the number in the first set of calculations.

❏ You may choose 2 instead of 3 bulb types. ❏ Your total number of lit squares should

therefore be less than in the first set of calculations.

Note: In this document, a comma (,) is used for the thousands (or millions) place in large numbers and a period (.) is used for the decimal place. In many countries, this is reversed. Don’t let this confuse you!

$0.08 250


Lumens of light:

Number of squares:

Bulb Type 1: ________________________


Lumens of light:

Number of squares:

Bulb Type 2: ________________________


Lumens of light:

Number of squares:

Bulb Type 3: ________________________


+




12

Use this page to take the values you just calculated in minimizing the energy, cost and carbon footprint expended by the city lights and subtract them from your calculated values for energy, cost and carbon footprint from page 10 (or Side 2 of the Energy Calculation Mat). The difference in their values will allow you see how much energy, cost and carbon footprint you saved by the changes you made!

Congratulations on saving energy, cost and carbon footprint!

Documents

Energy Calculation Worksheet v4 · PDF fileEnergy Calculation Worksheet !! 1 The Quality Lighting Teaching Kit’s Energy Calculation Worksheet !!! Usethe$worksheet$with$thedouble"sided%“Energy%Calculation