7 comments on “Evaluating energy efficiency claims”

Evaluating energy efficiency claims

Artifact

This (or other) energy efficient light bulb package(s).

Energy Efficient Bulb 20-75 w

So many opportunities here, depending on how targeted you want to be. Or, if you prefer, what kind of problem you plan to facilitate. There’s a clear nod to systems of linear equations (when one compares the time of payoff). There’s also an opportunity for some simple, linear equation building: evaluate the truth behind the $44 claim.

I’m even thinking of a 101qs video in which a perplexed customer at a hardware store is comparing this light bulb, and, say, one of these, though, these existence of incandescent bulbs is probably not long for this world. And, being Easter, hardware stores are closed today (fun fact: also, retailers really don’t like it when you take photos and videos in their stores). But that brings up a whole other can of worms: how much energy will countries save by switching to energy efficient bulbs? Like I said, lets of ways to go about this, depending on whether you want to be targeted or more exploratory.

Suggested questions

  • Is that $44 claim reasonable or bogus when you compare it against a bulb that uses 75 watts?
  • How does this compare with other energy efficient bulbs at the old hardware store?
  • What would happen if you switched every bulb in your house/school/neighborhood to energy efficient ones?
  • How much does a kilowatt-hour cost in our town? And what exactly is a kilowatt-hour?

Potential Activities

  • Take some predictions: does $44 savings sound about right over 5 years? Is that too high? Too low?
  • Collect some data on how much your lights are actually on in your house.
  • Plot five years of bulb use and see what happens.
  • Go around your house and count the number of bulb outlets you have. That data may be nice to have on hand.
  • Tables, graphs, equations, the usual bit.

Potential Solutions

Not sure what electricity costs in your particular neck of the woods, but Planet Money suggests a US average of $0.12 per KW-hr. These 20 watt bulbs usually cost around $12 per bulb, give or take. So our function looks like:

cost=$12+(20 W)*(1 KW/1000 W)*($0.12/KW-hr)*hours

Incandescent bulbs go for about $2, and comparing with a 75 watt bulb, our graphs look like this.

I actually get a savings over 8000 hours of $42.8:

(2+75/1000×0.12x 8000)-($12+20/1000 x 0.12 x 8000). That doesn’t take into account replacing incandescent bulbs more often. You could potentially get all stepwise functions if you consider the, perhaps 1000-2000 hour lifespan of an incandescent bulb.

(note the slightly different guesstimations of numbers in the planning form)

Final Word. Pretty much anything involving energy efficiency is going to allow for some systems problems. It’s all about tradeoffs, with higher initial costs gradually replaced by energy savings. Water heaters, A/C Units, automobiles, window insulation, you get what you pay for.

1 comment on “‘Groundhog Day:’ How long has Bill Murray been in Punxsutawney? (Part 1)”

‘Groundhog Day:’ How long has Bill Murray been in Punxsutawney? (Part 1)

Happy Groundhog Day everyone! Brief synopsis of Groundhog Day in case you didn’t know: Bill Murray is trapped in the same, repeating day in perpetuity.

How long Murray has been trapped is a question that has plagued mankind since the early 1990’s. It’s never directly addressed in the movie, it’s just hinted that it’s a long, long time. Probably months, possibly years.

Artifact

Let’s take this scene, for example.

How many days do you think it took Bill Murray to adequately retrieve and retain enough information to convince Rita that he is, in fact, a god?

Guiding Questions

  • How many people did Bill Murray discuss?
  • How many people are in the restaurant?
  • How many times would it take to know all that stuff about them?
  • How many times through would it take to get the timing on that crash of the tray dropping?

Suggested Activities

Some of these questions can be observed from the video. Some of these questions probably have to be estimated. But then, some could be investigated by your students. Think of all those “getting to know you” activities you put at the start of the year. Couldn’t we recreate something like that with this scene? Couldn’t we investigate “how many conversations does it take before you know enough details to describe the person well?”

Or couldn’t we investigate how many times before we could know exactly when an event will occur (the tray dropping)? I mean, don’t we do that in rewatching movies all the time?