Roland Lehoucq reports that "If global consumption continues to increase at the present rate, the time will come when energy use will outstrip the capacity for renewal." The energy potential of renewable sources has an advantage over fossil energy resources: these resources can be renewed. Yet, depending on the energy sources, various projections of limits include 40, 120, 220, 850 years. Lehoucq also notes that "the Earth gets from the sun 13,000 times more power than humanity consumes .... from a human perspective, the sun is an inexhaustible source of energy." Yet, even the energy available from the sun has limits. Read on....