Absolute Power


What Engineers Do In Their Spare Time

DH: On the drive into work I was stuck in traffic behind a slow-moving Toyota Matrix. As my blood pressure began to rise, my mind started wandering into the movie, “ The Matrix” and the benefits that a virtual existence would offer to my current situation.  That cascade of thoughts led to a follow-on to your question from the last blog:  “How much energy is actually produced by the human body and how much real work could be done with that energy if it were harnessed?”  Could I, for example, produce enough energy to lift a Toyota Matrix and place it neatly on the roof of a nearby apartment building?

CC: You apparently spend too much time stuck in traffic, thankfully nowhere near me.  Although it is an interesting question.  In “The Matrix”, all humans were enslaved in a virtual world and their bodies were used, effectively, as batteries to support a machine world, right?

DH: Yep, so the question is whether the human body would be an effective source of power.  So, let’s take a look at this in “Mythbuster” fashion.

CC: Okay,  but just remember:  If the answer is yes, whatever you do, don’t tell the government!  There’s certainly plenty of energy contained within the human body – just the excess body fat on an average individual is worth about 4kW hours per pound! 

DH: Wow, I guess that makes you a really powerful guy!

CC:  I prefer to think of myself as “above average”.  And at an average of 17 pounds overweight per American, multiplied by 300 million of us, a nationwide exercise program could yield 20 billion kW hours, or the total amount of energy used by 200,000 of us in a year!  

DH: Ugg – are you suggesting a  national network of interconnected treadmills tied to the electrical grid?

CC: Why not – we could even call it the TreadNet!

DH: I think DreadNet would be more appropriate.  This sounds like work!    What could we do to harness the energy of the average American couch potato?

CC: Ah, brilliant.  Capturing the energy naturally expended in *your* day to day activities, eh? I doubt that would be able to power an LED for more than a few seconds…

DH: I heard that the military and NASA are investigating methods to capture electrical energy that the body produces naturally through heat, motion, flexing and stretching, compression, urine and body heat.

CC:  OK OK – let’s look at this more seriously. What you’re describing is an extension of the concept used by my “perpetual” (self-winding) watch. But let’s keep the urine out of this flow for now .

DH: Yeah, that makes sense – it’s tough enough to make a watch water-proof.  

CC: Let’s see, an average 2400 calorie daily food intake provides a person about 2.8 kWh of energy, minus the human basal metabolic energy required to “power” your body (heart, lungs, cells, etc.) of about 2.4 kWh, which leaves about 400 Wh for additional activity every day.

DH: Right, so theoretically, if that energy could be used with 100% efficiency I would have enough power available to be able to light 40 compact fluorescent bulbs for about an hour.

CC: Yes – you’d be the modern equivalent of Uncle Fester.

DH: Or, putting it more into perspective, I could drive your laptop for about 20-30 hours.

CC: Interesting…a perpetually-couch-potato-powered laptop!  But, unfortunately, you’d have no energy left to type!

DH: Sounds like a normal day to me! That energy would be provided by additional snacks!  Where’s that jelly donut?? 

CC: Until next time…

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