Here is one way to look at a crowd: a group of people who gather together to look at something (think spectator sports or parades) or to participate in something (think state fair).

Here is the new way to think of crowds: as a power plant. This article talks about the possibilities:

Crowd farming: Power your building with human motion!

According to the article: “The Crowd Farm works by turning mechanical energy into electricity. In this proposal, the weight of a person is translated to tiled blocks which be slightly pressed down as people walk past them. A generator embedded inside them would take that small vertical movement and translate it into energy. To prove that their concept works, they created a small stool which when sat on, would power four small LED lights inside it.”

Here’s the same kind of idea: Human powered Gyms in Hong Kong. According to the article: “One person has the ability of producing 50 watts of electricity per hour when exercising at a moderate pace….If a person spends one hour per day running on the machine, he/she could generate 18.2 kilowatts of electricity and prevent 4,380 liters of CO2 released per year.” This article also contains a video on the idea.

In both of these cases, as in the case of solar energy, the overriding question might be, “that’s great, but how much money do you have to spend to capture the energy, so that you can calculate the cost per watt.” If it’s inexpensive, then projects like these move ahead at great speed.

See also: How solar cells work