Water-filled windows use sunlight to heat and cool buildings

British startup Water-Filled Glass has developed panes of glass filled with water that use sunlight to power a "crazy" energy-saving heating and cooling system.
Founded in 2020 by Loughborough University architecture lecturer Matyas Gutai, Water-Filled Glass (WFG) aims to use patented technology to make heavily glazed buildings significantly more sustainable.
Its windows contain a thin layer of water between glass panes, which absorbs heat from sunlight. The warmed water is then pumped