Researchers in Abu Dhabi are testing a pilot device that can store solar energy in sand to improve the efficiency of power plants and provide energy at night.The technology, developed at the Masdar Institute of Science and Technology, uses gravity to drain sand from a higher basin into a lower one, heating up the sand grains with solar power during the transition. In the lower basin, the energy can be stored and withdrawn at low cost to provide extra energy if needed, for example during peak hours and at night-time."Two pilot models of the system have been tested in an effort to prove its efficiency and applicability on a large scale in big projects,” says Nicolas Calvet, an assistant professor at the Masdar institute’s department of mechanical engineering.