A company in the Netherlands has developed a product using the rotation of a busy revolving door as an energy generator. The prototype is a heavily trafficked door at the Driebergen-Zeist train station in the Netherlands. About 8500 commuters use the train through this station every day. The motion of the revolving door is expected to generate 6400 kwh of energy per year, which could cover the needs of one average household.
As it turns out, others have thought of it before, including a company called Fluxlab which developed the Revolution Door. In this prototype, adding a generator to the resistance of the revolution may be more of a "drag" than most people care to encounter.
Do we have any revolving doors in Hawaii that have enough usage to generate a significant amount of energy? If the doors are there anyway, why not optimize their activity? Are there other revolving motions or actions that could also generate energy? Food for thought.