I finally started working on a website version of the documentation and added a discussion list.
3,025 total views
Jolly Jill asked about making a "universally recognized unit of 'energy consumed'" rather than the Calorie — something like a battery or a gas-can or an apple. Here's my e-mail response:
I took a closer look a this and tried to make some kind of "energy currency." It is valuable to keep things at a human-level, so a 100-Calorie apple seems to be a good choice. A 2.75-inch apple has about 100 calories. Conveniently enough, a peck contains about 25 of these size apples and a bushel, about 100.
For a smaller unit, a grape has about 3.4 calories (about 4 watt-hours) so 30 grapes (or maybe 5 6-grape bunches) makes one apple. For purposes of LED's, though, we're talking about 0.05 Calories or about 1/66th grapes. Thus, an even smaller unit could be a drop of maple syrup. There's 200 calories in a 4-tablespoon serving (so that's 16 Calories per teaspoon) and I put a little more than 12 drops into a 1/4 teaspoon, so each drop is about 1/3 Calorie (0.4 watt-hours); 10 drops makes a grape.
A candy sprinkle is about 0.07 inches across so about 877 fit in a teaspoon making each of them (assuming they're made entirely from sugar) about 0.018 Calories each so there's 18 in a drop of syrup. Let's call it 20 sprinkles, so 960 would fit in a teaspoon and each is 1/60 Calories. So now we've got:
- 1 sprinkle = 1/60 Calories
- 20 sprinkles = 1 drop of maple syrup = 1/3 Calorie
- 10 drops maple syrup = 1 grape = 3.4 Calories
- 6 grapes = 1 bunch of grapes = 20 Calories
- 5 bunches of grapes = 1 apple = 100 Calories
- 25 apples = 1 peck of apples = 2500 Calories
- 100 apples = 1 bushel of apples = 10000 Calories
I'm afraid I'm going in the wrong direction with this. Although it's neat to see the conversions, I think it makes things _less_ intuitive — calorie numbers may be best because they're compact to represent. This may be a useful way to get people to think about calories, though … like an LED can run for an hour on the energy in 3 candy sprinkles, or that it takes 3 bushels of apples to match the energy in a gallon of gas.
3,203 total views
The initial e-mail was as follows:
To help people manage their energy choices, I'd like to make the radical suggestion that you look at everything you bring simply for its energy content. Well, let's say limited to the devices that generate or convert energy forms, fuel, and things to burn. Including the food for people.
The key is to examine the energy with some common unit (although the sources of energy would be put in separate tables.) I want it to be the Calorie (with a big "C"; kilocalorie, that is … the one we use for food.) Obviously, then, all your food will be broken down into a list of the total calories. Gasoline, for instance, at 36.5 kilowatt-hours per gallon works out to an equivalent of 31,400 Calories per gallon (that's almost 16 days at 2,000 Calories per day, in case you're curious.)
For devices that take energy as input (i.e. gasoline in a generator) and produce energy as output (i.e. electricity from a generator) then you'd note it on the "source" energy table as a thing that consumes (i.e. a loss) and a supply of energy (i.e. a gain) on the "destination" energy table. For something like a solar panel, it would simply produce energy without consuming any — although it is from sunlight, you don't carry the sunlight in with you (despite the neat metaphor.) Consumers of energy would just show up as negatives (i.e. light bulbs would consume electrical energy; people would consume food.)
So a really basic set of tables for a camp of 10 people for 6 days who want to bring a 5KW generator, 5 gallons of gas, and a 100-watt string of lights they intend to run for 6 hours each day, it would look like this:
+120,000 Amount of food to bring
-120,000 10 people consuming 2,000 Calories a day for 6 days consume 120,000 Calories.
+157,000 5 gallons of gas
- 52,000 Energy used by the generator to run the lights (see note below.)
-105,000 Take home 3.1 gallons of gas
+3,100 Energy produced by the generator to run the lights (see note below.)
-3,100 100 watts * 6 hours per day * 6 days
(A note about the generator efficiency: a not-too-unusual 5500 watt generator I found on the Internet consumes 0.63 gallons/hour at peak efficiency of 50% capacity (2750 watts). Simply scaling that linearly would mean that 100 watts would consume 0.023 gallons/hour or about 720 Calories-per-hour and produce 86 Calories-per-hour. However, a gasoline engine's efficiency falls sharply when it's not being run at ideal power, so I'm guessing the efficiency would be twice as bad, thus, for the same 100 watts, it's 0.046 gallons/hour or about 1440 Calories-per-hour. Multiplying that out for the 6 days at 6 hours a day and it's 51,840 Calories.)
[Anyway, this camp chose their generator quite poorly and they probably wouldn't have, but I'm just using it as an example. It took me a while to piece the numbers together, but all these conversions can be provided in a table.]
Now the trick is to make it less like doing U.S. Income Taxes and more like fun. I talked with my friend Sondra Carr about it and she suggested one of those slide-rule kind of wheels to do conversions because she finds them more fun that filling out forms. I had suggested units of "loaves of bread" or something and she liked that — especially if this could all be coupled with a camp where you'd make a solar-baked loaf of bread, and while it's baking, to learn about how to do this analysis and to get a slide-rule wheel with the pertinent information.
Anyway, what's the education about it? My goal is to make it like the "remove packaging before you leave so you don't have to carry so much trash home" kind of elegance. I like that statement because it makes perfect sense and if you follow it, you go "wow: why is there all this friggin' packaging?" as you look at the pile in your living room when you've gone through all your convenience foods. It doesn't judge or condemn or make more work to make you learn something.
This is what I like about this:
- I think it can be made into a useful tool to help analyze a camp's energy usage. It's one of those things that gets overlooked in the planning process. How many of us have heard, "I don't know … just grab a 1,000 watt generator and bring like 20 gallons of gas and we should be all set."
- I think Calories put it into a human perspective: I had never done the conversion, but to think that the energy in a gallon of gas is the same amount of energy the average person needs for two weeks … wow.
- I think it shows how inefficient generators are and helps to identify where your energy goes. There is probably more work to be done here — I had originally wanted to do one big table so I could show waste (i.e. 52,000 Calories of gas becomes 3,100 Calories of electricity so 95% of the energy in the gas is wasted) but it was too cumbersome to present.
- I think it gives people a tangible idea of what energy is and where it goes. There is probably more work to be done here … I mean making it more concrete — make apples the unit (so a gallon of gas would be equivalent to about 350 apples) or bread … I like bread because it's so rooted in cultural traditions.
4,430 total views