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.
On a traditional solar photovoltaic panel, solar cells give off a flow of electrons when excited by sunlight, with an efficiency from about 9 percent to 20 percent depending on the solar cell material. Hotz said that making and storing hydrogen for a fuel cell is more efficient than using solar PV panels and storing the energy in batteries.
The research brings up the possibility of using hydrogen as a home fueling option, which could be very useful for places that are off the grid. Another company, SunCatalytix, is developing a system to make hydrogen from water using solar energy as well.
In practice, most household solar panels are grid tied and don't have battery storage so Hotz's cost and efficiency comparison is not a perfect comparison. Solar collectors can be used to make hot water instead of electricity, which many people consider the most economic use of distributed solar.