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Teachers' Guide: Getting Started

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Team Number/Name: _______________ Weather City: _______________ Zip Code: _______________
Student Name(s): __________________________________________________ Date: _______________


Part I: Analyzing raw data on a home's energy use.
1. From the Energized Learning home page, go to the Home Energy Saver web site (or link directly to http://HomeEnergySaver.lbl.gov).


2. Enter the zip code provided by the instructor and select "Go". (Half of the students/teams will evaluate houses in Anchorage, Alaska and the other half will evaluate houses in Dallas, Texas.)


3. At the initial results screen:
  1. Each team should enter house-size ("Conditioned floor area") and number of occupants provided by the instructor (classify all occupants as in the 14-64 age category).
  2. Those with houses in Dallas should also select "Central air conditioner", which is more realistic than the "No Cooling Equipment" option that will appear as the default value. No other values should be changed (we'll do that later).

  3. Click on the "Save Answers" button below the bar chart.
4. Click the "Calculate" button and wait for the revised results to appear.


5. Record the annual energy bill value from above the left-hand bar labeled "Your House" _______________ $/year.


6. Click on the "See greenhouse gas emissions and energy consumption" button and print the page. Record the following information (as applicable, not all forms of energy will show).

_______________ kWh/year
_______________ therms natural gas/year
_______________ gallons oil/year
_______________ gallons LPG/year
_______________ pounds CO2/year

7. Locate the resulting carbon dioxide emissions from the table printed in Step 6. Calculate the annual energy cost per occupant and energy cost per square foot.

_______________ $/occupant
_______________ $/square foot

8. Provide the results from Questions 5 and 7 to the instructor, who will draw some charts for discussion. How are "standard deviations" useful to the analysis?

Teacher Tools: Use "GS_Spreadsheets.xls", downloadable from the Teachers Resources page. Values in blue-bold are the results expected from the exercise. They can be erased so that student values can be entered in "real-time" during class. The spreadsheet is set up to calculate the standard deviations. A separate lesson can be provided to give students background in the derivation of standard deviations.


9. As a group, discuss the meaning and usefulness of the charts prepared by the instructor.

Teacher Tools: Create and share bar chart.

Averages are not always meaningful (e.g. average home has 2.6 occupants); none of the houses have average energy use or cost.

Importance of thinking about cohorts or subsets (the two climate locations, in this case).

Why might these results not agree with actual bills? Actual values represent a given year; simulations a long-term average.

Teacher Tools: Create and share scatter plots.

Proper normalization is key.

Standard Deviations (calculated on the spreadsheet).

The y-intercept of each data cluster represents the weather-independent part of energy use. Notice that it is similar for each location.


Part II: Exploring ways to reduce energy use and analyze environmental benefits.
1. Find the pull-down menu that allows you to view and change assumptions about the house description. It is the horizontal set of words about the bar chart, beginning with "General Info".


2. Selecting the "House Shape and Size" link within the "Heating & Cooling" category, increase the length and width of the house each by 5%.


3. Click the red "Save Answers" button and record the new energy bill from the left-hand bar on the results page. _______________ $/year.


4. From pull-down menus, make improvements to the house that you expect will reduce the energy use. Make as many improvements as time allows. Do not change the size of the house, the number of occupants, or other things that would reduce the quality of life. Try to reduce the bill to below the initial one (i.e. before you made the house larger). List the improvements you made, and the energy bill savings from each measure (you'll have to recalculate after each change):


5. Record the revised energy bill for each individual measure tested. Which measures yielded the largest savings?


6. Record the resulting new energy bill from the left-hand bar in the graph, with all measures combined. _______ $/year.


7. Click on the "greenhouse gas emissions and energy consumption" button and print the page. Record the following information from the column, entitled "Base Case" (as applicable, not all forms of energy will show).

_______________ kWh/year
_______________ therms natural gas/year
_______________ gallons oil/year
_______________ gallons lpg/year
_______________ pounds CO2/year

8. Provide the two new energy bills and carbon dioxide results to the instructor.


9. Instructor lists the energy savings measures on the board. Discuss.

Teacher Tools: Pre-/post- and 100% "Index" bar charts

Meaning and value of "Data normalization".

Reasons for differences from student to student (group to group).

Energy services (e.g. heating a larger house) can increase without energy use increasing.

Saving energy doesn't mean compromise.


Part III. Evaluating the costs and benefits of saving energy.
1. Assume it costs $500 to make the improvements that you implemented in Part II, how long will it take to earn back this money based on the energy savings? Show your work.

Teacher Tools: Payback time (in years) = Cost/savings per year, e.g. $500/$100 = 5 year payback time.


2. Using graph paper, draw a graph of the cumulative annual energy costs from Part I of this house over a 5-year period. Plot one value per year, with the x-axis being years and the y-axis being dollars spent on energy.


3. Add another line where the y-intercept is the up-front investment cost of saving energy ($500), and extend the curve from that point over the same 5 years, adding the annual energy cost from Part II.


4. Find the equations for these curves using the form y=ax+b.


5. Do the curves cross (Yes/No)? If so, what is the meaning of the point where they cross?

Teacher Tools: Yes. Crossing point equals the payback time (read off the x axis).


6. What factors could make the curves cross earlier in time?


7. How would the chart look if you paid for the improvements in equal monthly payments over 48 months (4 years)? Show on the graph paper provided.

Teacher Tools: Lower y-intercept, equal to the upgrade cost/4 years. Effective payback time would be sooner. Depending on energy savings level, payback time could be instantaneous (i.e. annual savings exceeding annual payment).


8. In what year will the cumulative energy bill be $15,000 for the house in Part I? How about the house in Part II (after energy savings improvements)? Show your work using simple algebraic equations.

Teacher Tools: Payback Graph

The example payback graph provided in the Excel Workbook can be shown and discussed. The slope of the curves represents the "rate" of spending. Slope is shallower for efficient house.

Can set Y(0) = Y(1) and solve for x to get payback time.


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