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Hi Timshel,
This or related topics have been discussed before on this list, so you may find additional ideas by searching the list archives:
http://community.lsoft.com/scripts/WA-LSOFTDONATIONS.exe?A0=ISEN-ASTC-L
I usually chime in to these discussions with my favorite example of a practical and beautiful use of bicycle produced power (other than sane personal transportation, of course!) — the bike powered smoothie vendor’s contraption I saw in Hawaii years ago. It’s indescribable how wonderful a papaya coconut pineapple smoothie tastes after you have had to pedal hard for a couple of minutes to produce it. A sort of sweat equity is involved I guess. It didn’t use a generator, just a direct mechanical like to a gearbox that drove the blender at a very high speed.
Regarding generator exhibits, one way to make them interesting is to put two or more in parallel — a model of the electric power grid, where a the electric company brings its power plants online in various combinations to manage different diurnal and seasonal loads. To do this you need to use DC generators, and place a diode in series with each (like a one way valve for electric current). Now, if one person starts cranking a single generator, the power flows through its diode into the load. The person doing the cranking can feel mechanical resistance in direct proportion to the power generated. But when a second person begins cranking, they don’t feel any mechanical resistance (except for a little friction in the bearings) *until* the speed reaches the speed of the other generator. At that point the first person will feel the mechanical resistance fall, as current begins flow through both diodes and the generators “share the load”. The lowered mechanical resistance then makes it easier to crank faster to produce more power. But if one person doesn’t keep pace and starts to slack off, the other feels it immediately. This beautiful feedback loop allows the uses to quickly learn to work together as an efficient team.
One other suggestion, with applies to all generator exhibits: if at all possible, use a chart recorder to display the power output instead of just a wattmeter. (An old dusty computer can sometimes be pressed into service for this purpose.) This has the great advantage of showing the trend of power production — you can see the line slope steadily down, for example, as muscles grow tired. And it shows clearly why the electric company charges you for kilowatt-hours (which is a measure of energy) and not for kilowatts. Power times time is what counts!
all the best,
Tom Nielsen
www.TheExhibitguys.com
On Aug 31, 2011, at 9:28 AM, Timshel E. Purdum wrote:
> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related institutions.
> *****************************************************************************
>
> HI all
> I have been asked to come up with a "wow" energy demonstration for a festival my museum is hosting in March. This is a bit out of my realm of experience so I am asking for ideas and help. (My museum is a natural history museum and most of the demos and activities we do are biology/evolution/water related).
>
> The example I was given was "you know-like a bike to power something." My concern with that is it's very popular and everyone else has done it so I'm not sure how "wow" that is. Anyone ever tried some sort of electronic pad where people jump up and down to generate electricity? I was also wondering about "energy vampires". Our local power company (who would help fund this) has a large campaign on reducing energy vampires in the home. Does anyone know a good resource for how much energy different appliances that are plugged in use-and how much human powered energy would be equivalent?
>
> Any other ideas? I did look through the archives of this community and got a few.
> THANKS
>
>
>
> Ms. Timshel Purdum
> Senior Manager of Education
> The Academy of Natural Sciences
> 1900 Benjamin Franklin Pkwy
> Philadelphia, PA 19103
> 215-405-5071
> [log in to unmask]
>
>
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