Fluxxlab of New York has a design to generate electricity for a building using the rotational energy when people pass through revolving doors.  The idea behind this  is similar to the principle behind turbines for hydroelectric power.  As people push through a revolving door the kinetic energy is converted to electricity.  The power generated from a device such as this could offset some of the electricity used to run the building.

 If the University of Notre Dame replaced the turnstiles in their football stadium with a similar device, perhaps they could shut down their coal-burning power plant for a day or two a year.