At first blush, Earth appears to have power to spare. The total power from sunlight striking the ground is a whopping 101,000 terawatts, and experts estimate that we could capture enough of that to exceed by a wide margin the 15 terawatts of power that the world9s population now consumes. But sunshine and other forms of renewable energy such as wind deliver energy in a far less dense form than coal, oil, or natural gas. Another issue: The sun doesn9t necessarily shine the brightest and the wind doesn9t blow the fiercest where most people live. And technologies have yet to emerge to store and transport vast amounts of energy generated from sunshine or wind. The energy problem is also a water problem. Electricity from solar thermal technologies uses 68% more water than electricity from coal. Use power from biomass crops and you9ll also use hundreds of liters of water to grow the fuel. Download the PDF