The best use of the sun's energy is to make hydrogen, according to a Duke University researcher. Engineer Nico Hotz earlier this week detailed results from his research around a rooftop solar panel that generates hydrogen from the sun's heat. The hydrogen gas--which is made by breaking off hydrogen atoms from a water solution--can be stored and used to make electricity in a fuel cell.  In his experiment, Hotz determined that his system creates more usable energy than solar photovoltaic panels which convert sunlight directly into electricity. He calculated the cost could be lower, too. There have been research efforts--and a commercial product from a company called Nanoptek--to make hydrogen from sunlight. Hotz's system, though, uses a new technique that relies on methanol, also known as wood alcohol, and a nano-engineered catalyst. Under the glass of Hotz's solar collector are copper tubes, coated with aluminum and aluminum oxide, which carry water and methanol. Once the liquid is heated to a sufficient temperature, a catalyst is added to cause hydrogen atoms to break off. That hydrogen gas is then piped and pressured for storage in a tank, where it can be drawn on to make electricity in a fuel cell.