dan’s blog

nothin but love from the interns

video: Nothin But Love

squid labs intern will bosworth lets it rip!

human power generation - no free lunch!

I’ve been seeing quite a lot of misconceptions recently about systems for capturing or generating power from humans. The primary misconception seems to be that you can somehow capture/generate a significant amount of power from some common action without otherwise affecting the person - in particular, that the person is somehow wasting a bunch of power, and a clever mechanism can capture it with no other ill effect. This is not the case! Extracting any significant power causes a correspondingly significant increase in the level of exertion required of the person. Evolution caused your body to optimize the amount of energy required to walk, run, etc - any body design which resulted in inefficient locomotion would have been selected against strongly. You also have an internal feedback system (your brain) that tells you how to optimize your motions by way of: “this feels more tiring than that”. Extracting energy mechanically from a person requires you to move your muscles, and only an insignificant amount of power would not be felt as a resistance to your muscle motion. For example, walking while generating a lot of power (via a hypethetical system that captured energy from a walking motion) would cause the motion to feel like walking in waist-deep water, or climbing a staircase. A typical diet-guide will tell you how much energy you are expending in normal activities. For example, walking burns around 200 Calories in an hour, or 233 watt-hours (0.23 kilo-watt-hours). If you wanted to extract an added 100 watt-hours to power your 100 watt lightbulb for that hour, your walking just got at least 50% harder (since the efficiency of the energy capture and conversion is well under 100%).

So, what can be done? One of two things: (a) a system that generates significant power, but requires similarly significant and obvious exertion by the person, or (b) a system that generates very small amounts of power, but requires no added exertion by the person. An example of (b) are fancy mechanical watches that wind their own spring through the random motion of the wearer’s arm while being worn. Both types are highly useful in many applications. What is not possible is: (c) a system that generates significant power, but requires no extra exertion by the person. Here I define “significant” as being of a magnitude comparable to the person’s nominal overall power output.

As a thought experiment, consider the hypothetical case of “The Matrix” where you are generating power solely from your heat output. Your temperature is 98 degrees, and you’re hooked to a heat engine (which generates power using the heat differential between you and a colder outdoors). What happens when you want to increase the power generated? it gets sucked out of you faster, and you get cold faster. if you’ve ever tried swimming for any period in cold water, you’re probably familiar with how hungry you are afterward - all your energy has been sucked out! So if you’re willing to tolerate being constantly cold and eating a lot, you can probably make a fair amount of power just sitting in the heat engine. unfortunately for efficiency reasons you’d probably need to be in a small enclosed compartment (like in The Matrix).  Have fun in there!

the snakecharmer

I found a beautiful 3-foot snake in the grass yesterday at berkeley marina!  it was quite docile despite the warm temperature and did not seem to have any complaint about my handling it.  after watching so many snake-handler tv shows on animal planet, it just seems so easy!  The interweb thinks this one is a Pacific Gophersnake.