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Can I measure the Solar Constant this way?

  1. Jan 13, 2010 #1
    I need a simple way to measure the Solar Constant in a cold environemt (Norther Hemisphere, this time of year ;) ).

    While its easy to think of ways in which the Sun can heat up something for you...putting for example a bottle filled with water colored black due to ink dosen't seem like a good way of going about it.

    How am I supposed to figure out how much energy from the sun per square meter the bottle absorbes? How many joules the bottle warmed up is trivial, but where do I get the surface? Do I just take the surface of the bottle or just the surface directly exposed to sunlight or something entirely different?

    Also any ideas on how to isolate whatever I'll be heating? Outside the ground is probably chilled already and will drain energy faster the warmer it will get... reducing the already laughable accuracy.

    Sure I think just buying a solar cell and measuring the amps from the thing would be the easiest way, but I think they are quite affordable esp since I'm unlikley to use them for anythign else. This is quite a fun project for a kid but I'm wondering how close you could actually get with improvised gear? Any ideas on how to make measurement easier, more accurate?

    Thanks for the responses. :)
  2. jcsd
  3. Jan 13, 2010 #2


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    Have you considered bag such as a hot water bottle or, if you must have it transparent, a sealed plastic bag with water in it? That way, the bag will lie flat and its area will be that of a rectangle, "width times length".
  4. Jan 13, 2010 #3
    I would suggest searching around for information on a "pyrheliometer". It uses a collimating tube with a black object/disc that it being monitored for temperature. I don't think making a crude one out of everyday objects would be too difficult. If you can't find any good info, let me know and I'll try to explain it a little better.
  5. Jan 13, 2010 #4
    Are you looking for global solar radiation on a horizontal surface in Joules/square meter? That information is generally available on the internet. Search for "Solar radiation data" for the country you are interested in. The US and Canada have solar radiation maps that can give you long term averages by month.
  6. Jan 13, 2010 #5
    He could also use equations to estimate incident radiation (Lui and Jordan, Hay and Davies, etc), but I assumed he wanted to determine things experimentally.
  7. Jan 14, 2010 #6

    Doug Huffman

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    The Solar Constant is defined outside the atmosphere. On the surface it may be called irradiance.
  8. Jan 14, 2010 #7
    Thanks for the replies guys. :) And yes I'm not searching for the data, I'm trying to figure out how to acquire it experimentally.
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