Energy, Entropy, and Everything

Honors 1500, Perspectives in the Physical Sciences

Third Project Assignment (due Friday, April 20, 4:00 p.m.)

(Preliminary data summary due Thursday, April 12.)

As announced in class, this project will be a "household energy audit". Pretend that you have been hired to assess the total energy use of one household, and to suggest ways in which this household could use less energy and save money.

The household that you audit can be your own, or that of a friend or family member. Ideally, you should have access to a complete set of utility bills (gas and electric) for the household for one year. You should also be able to go into the home to see how energy is being used at various times, and you should have a way of estimating how much gasoline is used for driving to various destinations. If your data is incomplete you can still do the project, but it will be easier if you can obtain fairly complete data.

After choosing a household, your first task is to determine the total annual use of electricity, natural gas, and gasoline. Gather the utility bills and records of gasoline purchase, or estimate the amounts in the best way you can. (For instance, you can estimate the amount of gasoline used from the number of miles driven and the miles per gallon of each vehicle. Past odometer readings may be written on registration or maintenance receipts, and you can measure the miles per gallon between the next two fill-ups by noting the odometer readings and number of gallons purchased.) Please turn in a one-page summary of total energy useage, in each of the three forms, on Thursday, April 12. Include a brief explanation of how you obtained each total. Show the amounts of energy both in billing units (decatherms, kilowatt-hours, and gallons) and in one common unit that you find convenient (you can choose any of these three or perhaps kilocalories or jelly donuts). Also show the amount of money spent, per year, on each form of energy.

Next, analyze the major ways in which each type of energy is used. For natural gas, the uses will probably be space heating, water heating, and perhaps cooking and clothes drying. For gasoline, try to divide trips according to purpose: commuting to work or school, shopping, recreation, etc. Significant uses of electricity may include air conditioner, swamp cooler, refrigerator, freezer, lights (indoor and outdoor), heating, cooking, laundry, television, computer, and perhaps others. (Don't worry about appliances that use very little power, such as clocks, or appliances that are used only rarely, such as power tools.)

Ideally, you should be able to calculate the annual energy consumption for each of these specific uses. In some cases, the calculation will probably be fairly easy, while in other cases, considerable ingenuity may be required. Seasonal variations in utility bills will provide useful clues. Power ratings of some appliances (like light bulbs) are written right on them, although in some cases (such as stereo equipment) the average useage is always much less than the number written. For newer appliances you may still have the yellow energy rating sticker. You may be able to determine the energy use of your refrigerator by reading your electric meter before and after a period of several hours when no other major appliances are used. Once you know this, you can estimate the use of an electric stove or dryer with further meter readings. Of course, the sum of all the specific uses of each major type of energy should add up to the total that you previously determined.

The main result of this project, then, will be an itemized list showing the amount of energy used for each purpose in one year (both in common units and in your standard unit), along with the amount of money spent for each use. In the text of your writeup, include a brief description of how you determined each numerical value. Also please include an introductory section describing the type of home (size, age, house or apartment), the number of adults and children living there, and any other basic information that may be important for context.

In the final section of your report, give some specific suggestions on how this household could save energy and money. Be as quantitative as you can--that is, for each of your suggestions, estimate the amount of energy and money that would be saved in one year. Again, some of these estimates will be fairly straightforward, while others might require considerable ingenuity. Concentrate on changes that could be made without too much inconvenience or extra expense. Here are a few of the measures that you might consider: changing the thermostat settings in various ways; closing off unused rooms; caulking and weatherstripping; improving windows in various ways; adding insulation; hanging laundry to dry; replacing lights, appliances, and/or cars with more efficient models; replacing a central air conditioner with a swamp cooler; controlling outdoor lights with a motion detector; eliminating pure waste such as an empty freezer or lights left on while away; taking the bus to work or school; walking, bicycling, or carpooling. For each measure that you recommend, include a brief explanation of how you estimated the amount it would save. Finally, add up the total savings (in energy units and in dollars) from all recommended conservation measures.

The exact format of your report is somewhat flexible, as long as it includes all the information described above. Your report should be readable to a typical adult who has not studied any science. Although a formal "abstract" would be out of place in such a report, you may wish to start with an informal summary, since most readers want to see the "bottom line" as soon as possible.

Please keep me informed of your progress on this assignment, and ask as many questions as you like. For some of the trickier estimates and calculations, I may be able to point you to some useful data.

Last modified on 5 April 2001.