Energy and your EnvironmentNextBackPrint

 

Page 10: Energy: How Much Does It Take?

Additional Information about energy measurement conversions:
Just as there are multiple units for measuring distance (meters, yards, fathoms), there are multiple units for measuring energy. These different units arose out of practical needs to quantify amounts, such as the heat generated by a furnace, or the work that a horse could do in a given period of time. Because energy is the same thing, whether it's in a furnace or a horse, these quantities can all be converted to equivalent units. By multiplying a quantity in one measurement unit (e.g., calories) by a conversion factor, you get the quantity in another measurement unit (e.g., joules). Joules is the standard scientific unit of measurement for energy.

Answers to Brain vs. Car
1. 2500 food Calories/day x 20% x 100 days = 50,000 food Calories
Conversion to joules: 50,000 food Calories x 4184 joules/food Calorie = 209,200,000 joules
2. If the car gets 25 miles/gallon, then it takes 4 gallons of gasoline to go 100 miles. 4 gallons of gasoline x 1.5 gallons crude oil/gallon gasoline = 6 gallons crude oil.
Conversion to joules: 6 gallons x 146,000,000 joules/gallon of crude oil = 876,000,000 joules.

The 100-mile car trip takes a little more than 4 times the energy needed for a brain to work for 100 days.

Page 11: Youth Can Make a Difference

Research Tip:
Contact your local business organizations and community nonprofit associations to find out about sponsorship possibilities for youth activities in energy efficiency or environmental improvement.

Page 12: Investigate Your School's Energy Habits

Sample Calculation for a School Relighting Project
(Costs, hours, and number of lights will vary with location.)
1. Standard fluorescent tubes and ballasts are to be replaced with "T-8" fluorescent tubes and electronic ballasts. Old lighting used 75 watts for each 8-ft fluorescent. New lighting uses 50 watts for each 8-ft fluorescent. Electronic ballasts increase efficiency of the lighting system by 35%. Replacement costs = $12 per tube and $40 per fixture. Tubes last for approximately 20,000 hours of use.
2. School had 300 8-ft tubes and 150 ballasts.
3. Lights are on 1400 hours/year
4. 1400 hours/year x 300 tubes x 75 watts = 31,500,000 Watt-hours/year. (Old system). This is the same as 31,500 kWh/year. 1400 hours/year x 300 tubes x 50 watts = 21,000,000 Watt-hours/year. (New system) This is the same as 21,000 kWh/yr.
5. If electricity cost per kWh is 10ยข, then cost for each system is:
____a. Current system: 31,500 kWh/yr x $0.10/kWh = $3,150/yr
____b. New system: 21,000 kWh/yr x $0.10/kWh = $2,100/yr
____c. Savings from electronic ballast of 35%: $2,100 x 0.35 = $735
____d. Total Savings = kWh svgs + electronic ballast svgs = ($3,150/yr - $2,100/yr) + $735/yr = $1785/yr
6. New system cost = (300 x $12) + (150 x $40)= $3,600 + $6,000 = $9,600
____a. (Consider that old tubes and ballasts would need replacement anyway, so the additional cost of the new system ____will not be as high as this figure.) If 1/3 of tubes and ballasts needed replacing, then real cost would be $6,400. It ____would take about three and a half years for the energy savings to pay off the cost of the new equipment.
7. Other energy uses include gasoline used by people traveling to and from school, energy for heating and air conditioning, electricity for classroom, office and cafeteria equipment, etc.