Researchers have developed a device that can store solar energy by inexpensively converting it to hydrogen —an important step toward making solar power available around the clock. The technology, which which was recently described in the journal Science , is a type of “water splitter,” a device that can efficiently divide water into its constituent parts: hydrogen and oxygen. The concept is important for solar energy storage because hydrogen gas can be used directly as fuel and is relatively easy to store, the researchers say. The device can convert 12.3 percent of the energy in sunlight to hydrogen, according to the report; conventional solar cells, in comparison, convert roughly 16 percent of energy from sunlight to electricity, but a significant portion of that energy is lost when converting it to a form that is easily stored. The design of this water splitter is an improvement over previous iterations, the researchers say, but the device’s longevity and reliability will need to improve before it becomes a practical, large-scale solar energy storage option.