an insulator. The central cooking tube is made from borosilicate glass, which is resistant to thermal shock, and has a vacuum beneath the surface to insulate the interior. The inside of the tube is lined with copper, stainless steel, and aluminum nitrile to better absorb and conduct heat from the Sun's rays. Solar cooking tube systems use a reflector to enhance the thermal energy capturing. There are models of tube cooking system in India which has energy storage devices installed at the bottom of the tube to store heat for cooking or heating food during night. These vacuum tube solar cookers can cook a meal in as little as 20 minutes. Advantages and disadvantages Advantages High-performance parabolic solar cookers and vacuum tube cookers can attain temperatures above 290 °C (550 °F). They can be used to grill meats, stir-fry vegetables, make soup, bake bread, and boil water in minutes. Vacuum tube type cookers can heat up even in the clouds and freezing cold. Conventional solar box cookers attain temperatures up to 165 °C (325 °F). They can sterilize water or prepare most foods that can be made in a conventional oven or stove, including bread, vegetables and meat over a period of hours. Solar cookers use no fuel. This saves cost as well as reducing environmental damage caused by fuel use. Since 2.5 billion people cook on open fires using biomass fuels, solar cookers could have large economic and environmental benefits by reducing deforestation. When solar cookers are used outside, they do not contribute inside heat, potentially saving fuel costs for cooling as well. Any type of cooking may evaporate grease, oil and other material into the air, hence there may be less cleanup. Reduces your carbon footprint by cooking without the use of carbon based fuels or grid electricity from traditional sources. Disadvantages Solar cookers are less useful in cloudy weather and near the poles, where the Sun appears low in the sky, so an alternative cooking source is still required in these conditions. Solar cooking advocates suggest three devices for an integrated cooking solution: a) a solar cooker; b) a fuel-efficient cookstove; c) an insulated storage container such as a basket filled with straw to store heated food. Very hot food may continue to cook for hours in a well-insulated container. With this three-part solution, fuel use is minimized while still providing hot meals at any hour, reliably.