A research team at Sweden's Chalmers University has developed a window film capable of absorbing solar energy during the day and releasing the energy as heat into building interiors at night. A few years ago, the same research team introduced the Molecular Solar Thermal (MOST) system, in which solar energy is stored in a liquid medium, then later released as heat. Now, the technology has been applied to a clear film that could be applied to the inside of windows in buildings.