• Question: In winter the days are sometimes quite sunny and that generates heat indoors. I want to generate even more heat and so thought I would create a glass trumpet shaped object, put it on the window standing on its base. Then the sunlight would "super" heat the air in the trumpet. That would increase the amibent air temperature in the house. Possible or tooooo?

    Asked by Anon to Saiful, Piers, Petra, Olivia, Meggi, Jawwad, Chris, Bethan on 10 Jan 2017.
    • Photo: Mechthild Luebke

      Mechthild Luebke answered on 10 Jan 2017:


      Yes possible, but you might make things too complicated 🙂

      Your idea is very important and many researchers try to use it: How can we heat up the room in cold days just by using the sun lights and our windows?

      Future glass is supposed to be multifunktional. The glass needs to block the sun light in summer and heat up the room in winter. There are many attempts to reach this with electrochromic glass or liquid or air additives in the glass which circulates in the sun light and results in heat and even electric energy.

    • Photo: Piers Barnes

      Piers Barnes answered on 10 Jan 2017:


      This is an interesting idea. It is possible that the your trumpet structure could act as an indoor ‘green house’ to trap sunlight, heating the air inside it more than that in the rest of the room. However, I’m not sure that the structure would heat the overall air temperature more than without it. This is because the amount of power from direct sunlight available to heat the air in the house is limited by the amount of light that can pass through the window. The trumpet structure will not increase this quantity. A key factor which will determine how much the air in the house warms up due to the sunlight is how much energy radiates back out of the window. Some of this escaping energy could be visible light reflected from the light coloured objects and walls (or the glass trumpet), the rest of the radiating energy would be in the infrared part of the spectrum (emitted from anything that has a finite temperature). One of the keys to warming the house using sunlight (in addition to having good insulation) is to use windows that are not transparent to infrared radiation. It is now possible to get windows with glass coated with a layer that reflects infra-red light, so that the infra-red radiation emitted from the warm interior of your house can’t escape.

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