Activity 3.1.3 Using Energy Efficiently

Introduction

Would you believe that 18% of the world’s population uses 56% of the world’s energy supply? Would you believe that the U.S. consumes almost 25% of the world’s energy, but has only 3% of the world’s population? All of the resources that we use everyday to meet our needs andwants are provided through the use of natural resources.Natural resources are either renewable or nonrenewable.Renewable resources are materials that can be replacedthrough natural and/or human processes. Exhaustible resources exist in fixed amounts within the earth.Once they’re used up, they are gone forever.Inexhaustible resources, like the sun and wind, cannot be used up.

Energy derived from natural resources, lights, heats, andcools our homes, schools, and factories. It powers themachines of industry and transportation. The clothing wewear, the food we eat, the buildings in which we live, and even the systems we use to communicate – allare dependent on energy.For generations, our society has been enjoying the benefitsof plentiful, inexpensive, and easily available energy – fossil fuels. But these fuels, such as coal, oil, and naturalgas, are finite. As supplies have decreased and becomemore expensive to extract, the search has intensified foralternative energy sources – sources of energy other thanfossil fuels.

The most obvious and virtually limitless energy source isthe sun. In terms of humankind’s residence onEarth, the sun will last forever, continuouslyradiating energy that makes life on our planet possible.Although Earth intercepts only a small fraction ofthe total energy emitted by the sun, the amount receivedis thousands of times the present energy requirement ofthe world’s human population.

Human activities over the past 100 years, particularly fossil fuel burning and deforestation, are releasing unnatural amounts of carbon dioxide (CO2) into the atmosphere. Today people are concerned about the rising CO2 concentration in the atmosphere due to the dangers of climate change. Many engineers are working to reduce CO2 emissions. For example, environmental engineers are studying carbon sequestration — a term used to describe processes that remove carbon from the atmosphere. Mechanical and electrical engineers are working to design buildings, homes, cars, and appliances that use less energy. They are also engineering devices like solar panels and wind turbines that generate electricity from natural sources and do not emit CO2 into the atmosphere.

The average American home spends about $1,000 on electricity alone every year. The average electricity cost in the U.S. is about 10 cents per kilowatt-hour (kWh), so using 1000 watts of electricity for an hour costs 10 cents. Energy you save in your home means no energy was lost producing it or transporting it to your home. In this activity you will explore ways that you can use energy sources more efficiently.

Equipment

  • PLTW Gateway notebook
  • Pencil
  • Computer with Internet access
  • Kill-A-Watt™ Power Meter
  • Calculator

Procedure

  1. If possible, find the answers to the following questions about the home you live in:
  • An estimate of the money spent on energy per year. ______
  • Cost per kWh of electricity – found on electric bill or contact utility ______
  • Cost per Therm of natural gas – found on gas bill or contact utility______
  1. Read about Energy Efficiency at this site:
  2. Explain seven ways that you could save your family money on their energy bills.
  1. Use the Light Switch and Appliance Calculators at the same site: . Now choose up to three energy-saving options that you can commit to performing.
  • List the changes:
  • Calculate the savings ______
  1. Research and then draw a graph by hand or using the computer that shows how energy sources are used in the United States.

Conclusion

  1. Discuss with your family some ways that you can save energy at home. Describe below what you discussed and highlight the ways your family will try to use energy more efficiently.
  1. Use the Kill-A-Watt™ Power Meter to determine how much energy is used for at least four items. List the items and calculate how much money you spend to use the appliance for 1 month. Give a suggestion as to what you could do to save money on your energy bill.

Example: A coffee maker uses 1 watt when NOT in use, which is about 9 cents per month. When brewing and keeping the coffee warm, the coffee maker uses 880 watts. If the coffee maker is on for 3 hours per day, it costs $10.30 per month. If you brew the coffee and put it into a coffee carafe, you can save up to $9.50 per month. If you unplug the coffee maker when not in use, you can save $.09 per month (assume power company charges $.13/kWh).

Energy User / Total wattage (Meter Reading)
(W) / Converted Wattage/ 1000
(kW) / Monthly hours used / Monthly kWh
(converted wattage x monthly hours used) / Approx. cost per month ($.13/kWh)
(monthly kWh x $.13/kWh)
Coffee Maker / 880 / .88 / 90 / .88kW x 90h = 79.2kWh / 79.2kWh x $.13 = $10.30
  1. Compact Fluorescent Light bulbs (CFLs) use ¼ of the electricity that incandescent lightbulbs use. If you changed 10 lightbulbs in your house to CFLs and those lights were on for 5 hours per day, calculate the energy and money saved (assume 60 watt incandescent lightbulbs at the cost of $.13/kWh) per day and then the savings for one year (365 days in a year).

Energy User / Total wattage (Meter Reading)
(W) / Converted Wattage/ 1000
(kW) / (kW) X hours used X ($.13/kWh) / X 10 bulbs? / X 365 days a year = cost per year
incandescent / 60 / .060 / .039 / .39 / 142.35
CFL
  1. Incandescent bulbs are $.75 each, CFL bulbs are $3.00 per bulb.If you change 10 light bulbs in your house how many days will it take before you start saving money by buying the more expensive CFL bulbs?
  1. Find the difference in the cost of 10 incandescent bulbs and 10 CFL bulbs.
  1. What was the difference in the electricity cost per year of the incandescent and CFL bulbs? Now divide this number by 365 days to find the cost per day.
  1. Divide a. (the difference in the cost of 10 incandescent bulbs and 10 CFL bulbs) by b. (cost per day) to find out what day the cost of the extra cost of the light bulbs will be paid off.
  1. On day ( ) the extra cost of the CFL light bulbs will be paid off.
  1. Typically a CFL bulb will last 10 times longer than an incandescent light bulb. Learn more at: .
  2. Compare the cost of 2 different game systems per year (at 6 p.m.).

Energy User / Total wattage (Meter Reading)
(W) / Converted Wattage/ 1000
(kW) / (kW) X hours used X ($.13/kWh) / X 365 days a year = cost per year

© 2011 Project Lead The Way, Inc.

PLTW Gateway – Energy and the Environment Activity 3.1.3 Using Energy Efficiently – Page 1