Using natural energy resources

Pollution-free energy from largely untapped sources is available in amounts exceeding our needs. Geothermal energy -- which makes use of heat from the earth's core -- is theoretically accessible using existing drilling technology in amounts thousands of times as great as the amount of energy contained in coal reserves. Tidal energy is also promising. Analysts who study solar power generally agree that technologies are ready to begin building a world energy system largely powered by solar resources.