Ignoring the blatant ethical issues associated with this question, I’m genuinely curious from a scientific standpoint how efficient the human body is at generating energy. I’m a chemical engineering major and after learning about combustion engines and steam generation, there’s a great deal of inefficiency. After taking an intro to biochemistry course it seems like the human body is incredibly efficient at energy efficiency, using food as the fuel. I was also made curious by that one black mirror episode where people rode those standing bikes as their job, I think it was for power generation but I can’t really remember. Would it actually be a good substitute in terms of equivalent power and clean energy? Again, a horrible hypothetical given the history and current use of people in such dehumanizing ways, and if this really isn’t something to be discussed, I apologize.
In: Engineering
Professional, Tour de France-type bicyclists generate about 400-500 watts of power per hour, which is equivalent to about 340-430 food calories. These bicyclists are going to vary in their calorie needs over that hour, but a good estimate is 1,000 calories per hour. That gives an efficiency of about 35-45%, which is not bad compared to a power plant that just burned the food they would have eaten and used it to drive a steam turbine. You might get even more efficiency if you directed the bicyclists to pedal at a more moderate pace.
However, there are a couple of big issues with using this as an actual means of power generation:
1. Scalability. Professional bicyclists are a rare breed, train a lot, need lots of recovery time, and frequently get injured (even aside from crashes). There’s no way this could be a work-a-day job that lots of people have.
2. Max scale. Half a kilowatt per hour is just not very much, even if its gotten with decent efficiency. The average US household uses 30 kilowatt hours of energy per day, so even if we somehow got *everyone* on a bike for a 16 hour shift, we’d produce less electricity than we currently use.
3. Economics. Food is expensive. Humans are even more expensive. Putting food into a power plant that also demands a wage is a ridiculous idea compared to just shoveling random biomass like wood or grass into a furnace. $1 per kilowatt hour is an extremely high price for electricity, but generating that electricity would cost you 2 hours of wages – well over $10 in any developed country (and less developed countries would have much lower electricity prices). That’s before you count any of the costs for buying/maintaining/storing the bikes and whatever you might have to contribute to the exceptional food and medical costs of your employees.
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