The Matrix and Body Heat

“The Matrix” , while a somewhat entertaining film, was based on a premise that made no sense thermodynamically. In the film, the machines use humans confined to pods as an energy source. In an attempt to salvage a modicum of self-consistency, the confined humans were fed using a source derived from deceased humans. Unfortunately, this can never work. A person weighing say 70Kg requires about 2000 Kcal of food energy per day, a little less if they’re inactive. A gram of tissue has about 5 Kcal of combustible energy. If a person is converted entirely into a food source, this would yield about 350,000 KCal, enough to sustain a person for only 175 days. Thus, the human generator could never achieve a chain-reacion necessary for a self-sustaining energy source.

However, we as humans do produce plenty of body heat, about 100 watts when we’re still and a lot more when we’re exercising. This is enough to power many of our devices. It is reported in this week’s Nature Materials, that a group from the University of Toronto has devised a polymer based photovoltaic cell that is sensitive to infrared radiation. This paves the wave for making clothing someday that can use sunlight, ambient light, and body heat to power the toys of the modern road warrior.

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5 thoughts on “The Matrix and Body Heat

  1. Is there actually sunlight in Toronto? Seriously, there is an incredible amount light emitted by “ambient sources” at all times on the planet (for example, think of how well illuminated the eastern US coastline is when you fly over it at night). It seems obvious that if this could be collected, it represents a massive energy source. The problem, I imagine, is that this energy dissipates rapidly with distance from the source, so it’s not clear how to collect it to re-use. Did the Nature article mention using the cells in clothing? Seems like you’d want to have a cell directly in each device of interest. I suppose that if you charged up your clothing, then you’d have a regular energy supply at your disposal, to use for whatever device you desired. On the other hand, it might be more convenient (albeit less sci-fi cool) to charge up something mundane like a portable battery rather than a SuperSuit.

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  2. Hi Jon,The article itself did not mention clothing, just that it was a polymer so it could potentially be woven. The key thing is that it is sensitive to heat so if you wore it you could best utilize body heat. Getting that power to your laptop would be a different technological (or sartorial) challenge.Carson

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  3. Hi Carson,I thought there were hints that even the machine world wasn’t real – just another level of the matrix. In that case, it would not need to obey ordinary physical laws.The humans-as-heat-engines issue was the only thing I didn’t like about Matrix I. The sequels weren’t nearly as good, and I thought they missed a huge chance to show that the humans like Morpheus and Neo were programs themselves (dreaming of their own humanity).BTW, are you sure about your solar energy estimates? I thought we were using an even smaller fraction of the total energy hitting the earth. The eventual limit to your reasoning (assuming no faster than light travel), is probably humans living on a huge Dyson sphere encircling the sun, or modifying themselves genetically to live in space using solar power. (Imagine a big gas bag named Steve with solar panels :-)

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  4. Hi Steve,I was hoping for another level of virtual reality in the matrix but they didn’t follow through.The 1.4 KW/m^2 seems to be the accepted value. I think it assumes a bright sunny day at the equator so I probably have overestimated how much sunlight we exploit. I also included the surface area of the oceans. It was sobering that even with such optimistic projections we are using a boatload of energy. Most of it is in the form of fossil fuels which has accumulated over hundreds of millions of years. There is a lot of coal out there but it is finite and we’re using it up pretty quickly.

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