Some day the nation’s energy needs might be entirely solved through the use of hot water, and the man to thank didn’t get his business started until he was 83. Bob Potter, now 88, started Potter Drilling five years ago to develop a novel way of drilling deep into the earth’s crust using hot water, instead of diamond-based drills, to tap into geothermal sources that could potentially operate power plants everywhere in the United States. Current geothermal power plants rely on underground aquifers of hot water that are relatively close to the surface, most of which are found in the western United States. But if Potter’s idea works, geothermal could become a nationwide source of carbon-free electricity and eliminate the need for burning coal to produce energy. Potter got his idea from his earlier work on the Manhattan Project, the 1940s secret government program that invented the atom bomb.