Energy- abundant, versatile, reliable, portable, and affordable, fossil fuels provide over 80 percent of the worlds energy because they are superior to the current alternatives, Disadvantage of most of the renewable energy sources is its unreliable supply. But to renewable energy resources from wind, solar, and biomass, man can control access to and conversion of the energy held in fossil fuels. Any machine or person can't control when the wind blows or at what velocity. No one can control how much of the radiant heat of the sun will hit the earth on a given day or hour.