How will we power the cities of the future? That is one of the Big Questions right now.
Huge gains can be made by focusing on efficiency. So much energy is wasted and doesn't do anything productive. There are also huge almost untapped sources in solar power, ocean power, geothermal, wind power, smart use of biomass (f.ex. algae, waste). How will it work out? We don't know, but as Alan Kay said: "The best way to predict the future is to invent it." Lets all do our part, either by working directly on solutions or spreading information and creating a cultural and political context that will accept change.