<DrumBeat: August 13, 2006The Oil DrumSaudi oil production revisited>

254 comments on Due Diligence: A reader's response to Khosla

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LJR on August 13, 2006 - 3:04pm Permalink | Subthread | Parent | Comments top
I get it.  My box fan motor is using energy for an hour at a rate of 260 watts/hour whereas the car is using the same energy in 2 minutes for an overall rate of 7800 watts per hour.

Thanks.

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Engineer-Poet on August 13, 2006 - 3:52pm Permalink | Subthread | Parent | Comments top
Um, no.  "Watts per hour" is as meaningless as "horsepower per hour" (outside some esoteric things mostly suitable for physics education).  There's watts and watt-hours; if the sentence wouldn't make sense if you substituted "horsepower" for "watts", you're almost certainly mis-using the term.
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LJR on August 13, 2006 - 8:44pm Permalink | Subthread | Parent | Comments top
All right, already.  884 BTU per mile.  Watts suck.
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wimbi on August 16, 2006 - 7:56am Permalink | Subthread | Parent | Comments top
EP.  Many thanks for all your good work, not just this piece but all the great things you have on your ergosphere.  

I think a lot of people get self-confused when they get into the habit of abbreviating kilowatt-hrs to kilowatts, as in "My electric bill showed only 213 kilowatts last month". From there  to kilowatts per hour is a swift slide down the steep slippery slope.

BTW, I have finally got a thin stream of  vital fluids flowing again toward completion of my 1kW home power stirling engine and shall give a full report asap.  The military industrial vampire had sucked it dry for an entire year (goddamit).

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Engineer-Poet on August 16, 2006 - 9:38am Permalink | Subthread | Parent | Comments top
I'm looking forward to reading about it.
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Squalish on August 13, 2006 - 5:31pm Permalink | Subthread | Parent | Comments top
POWER:
Horsepower
Watts

ENERGY:
Joules
BTU
watt*hours

Power is energy divided by time.  Energy is power * time.

If charging a perfectly efficient battery for 10 hours takes 1 watt, then you have 10 watt hours in that battery.  That battery can't release all the energy at once after you're finished though, it maxes out at say, 5 watts.  So you can power a 5 watt lightbulb for two hours (until the batteries dead) on the amount of energy you charged it with.  

Alternately, you could power a 2.5 watt lightbulb for 4 hours, and so on and so forth.

We say that the battery has a capacity of 10 "watt hours," which is a distinct unit.

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