Imagine a transparent vacuum flask that allows light to enter but restricts it from escaping the vessel. That is the basis of the Evacuated Tube technology in a nutshell. It’s a double layered glass vessel with a vacuum in the space between the two layers of glass. The core of this vessels can trap enough light on a cloudy day to cook a meal. Also, coupled with a ‘thermal battery’ – a material that collects and stores heat through the day and uniformly releases that heat at night – this technology can also be used for night-time cooking.