1. Subscribersonhouse
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    02 Oct '14 15:10
    http://phys.org/news/2014-10-solar-farm-uk-life-berkshire.html
  2. Joined
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    02 Oct '14 17:2215 edits
    I read this link. But, although it is an interesting idea, I was rather surprised that it offers significant advantages putting them on water. I would have naturally have assumed that there would be less advantage putting solar panels on open water when, for less cost I would assume, you could have the same total area of solar panels split up so that you have lots of separate panels on the sunniest south-slopping sides of the roofs of many houses. I would think that would be more cost effective than floating them on flat water because

    1, you haven't got the cost of floats that stop them from sinking -all you have to do is bolt them firmly to the roof. Surely that cost less?

    2, putting them on a south-sloping part of the roof would mean, in the Northern hemisphere, they would get more sun on average than if they are positioned horizontally. Therefore, with all else being equal, you get more average power out of them for the same costs.

    For these reasons, I would have naturally thought it would be better to first fill up all the current wasted flat area on south-slopping roofs before considering floating some on water.

    however, it says:

    ""Thanks to the cooling effect of water on PV panels, our systems produce more energy than land-based systems of a similar size,""

    but why would lowering the temperature help make it produce more energy?
    Perhaps when they get very hot, they become less energy efficient? But I assumed that they are built to be very heat resistant so it would surprise me if it really made that much of a difference.

    but it does make an interesting point with:

    "By lowering the water temperature and reducing the size of the water area exposed to air, floating solar panels can reduce water evaporation by up to 33 percent on natural lakes and ponds, and by up to 50 percent on man-made facilities..."

    -not sure if that makes it generally better putting them there than putting them on south-sloping roofs. I cannot help but wonder, is water wasted by evaporation from these lakes really economically significant? I suppose that just depends. It may not be generally so for wet climates such as in the UK while I assume it is nearly always be significant for drier climates so it could be really great for dry climates!
    Here in the UK, in resent years I have noticed we seem to more often get too much rain and flooding than we get too little rain and drought. So I wonder, couldn't reducing evaporation from lakes sometimes increase the flood risk? Could this be counterproductive for the UK?

    But I have noticed that, taking account basic physics, the link appears to logically contradict itself!
    Because it first says

    "Thanks to the cooling effect of water on PV panels..."

    but then it says:

    ""By lowering the water temperature..."

    But if the water cools the panels, that means heat is being transferred from the panels to the water and therefore, surely, it would be heating the water, not cooling it!?

    In addition, wouldn't the reduced evaporation mean less heat can escape via evaporation?
    Am I missing something here?
  3. Subscribersonhouse
    Fast and Curious
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    02 Oct '14 19:241 edit
    Originally posted by humy
    I read this link. But, although it is an interesting idea, I was rather surprised that it offers significant advantages putting them on water. I would have naturally have assumed that there would be less advantage putting solar panels on open water when, for less cost I would assume, you could have the same total area of solar panels split up so that you have l ...[text shortened]... he reduced evaporation mean less heat can escape via evaporation?
    Am I missing something here?
    Don't forget, the panels are extracting some 20% of the incoming solar energy so it would be in effect like putting a reflective mylar sheet over the water which should cool it off by reducing the heat input. It is making use of previously wasted space, that is space that is available for these kind of projects.

    I have an above ground pool, not very large, about 20 feet, 7 odd meters diameter but I see evaporation take down the water level in summer fairly quickly, and that with no leaks. There was one solution for that problem, not that I found it appealing, fill the surface with ping pong (table tennis) balls which cover the water and lower the evaporation rate. Don't think I would like diving into a pool filled with ping pong balls๐Ÿ™‚
  4. Cape Town
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    03 Oct '14 08:26
    Originally posted by humy
    but why would lowering the temperature help make it produce more energy?
    http://homeguides.sfgate.com/effects-temperature-solar-panel-power-production-79764.html
    A field experiment in the United Kingdom revealed a drop of 1.1% of peak output for every increase in degrees Celsius of a home photovoltaic solar panel once the panel reached 42 degrees Celsius


    Some advances in solar panel efficiency consist of finding ways to get rid of excess heat to improve efficiency.

    But I have noticed that, taking account basic physics, the link appears to logically contradict itself!

    Am I missing something here?

    Yes, you are missing the fact that the heat is coming from the sun.
    No solar panels: All heat from the sun strikes the water and heats it up.
    Solar panels: some heat from the sun is reflected. Some heat is used by the solar panels to create electricity. Some heat from the sun is absorbed by the solar panels and passed on to the water - cooling the the solar panels and heating the water, but crucially, heating it less than it would have been if the solar panels were not there.
  5. Joined
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    03 Oct '14 10:077 edits
    well, that explains it ๐Ÿ™‚ Thanks guys.

    Just a thought:
    this could be used to great advantage to stop environmental disasters in several parts of the would caused by large bodies of water trying up. For example:

    http://en.wikipedia.org/wiki/Aral_Sea
    "...The shrinking of the Aral Sea has been called "one of the planet's worst environmental disasters"..."

    and also:

    http://www.smithsonianmag.com/science-nature/the-dying-of-the-dead-sea-70079351/?no-ist
    "...The Dying of the Dead Sea
    The ancient salt sea is the site of a looming environmental catastrophe..."

    -and sustainably generate electricity the process.
    Although I think transmitting the electricity long distances to where it can be used would be a major issue, I think this is still definitely worth considering!
    Seriously, I think someone should seriously look into this!

    And, even where and when transmitting the electricity long distances to where it can be used is just too problematic, instead of covering much of the lake with solar panels, why not with much less cost float over the top a very thin (to minimize costs ) brilliant while reflective layer to maximize the albedo of the lake? This would not only protect the lake from drying up but contribute in a small way to increasing the albedo of the whole Earth this slightly counteract global warming and thus may even pay for itself economically by cutting the economic costs (slightly ) of global warming!?

    Seriously, I think someone should seriously look into both of these options!
  6. Cape Town
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    03 Oct '14 10:12
    An example of improving efficiency by cooling.

    http://engineering.stanford.edu/news/stanford-led-team-develops-self-cooling-solar-cells-last-longer-have-more-power
  7. Subscribersonhouse
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    03 Oct '14 15:04
    Originally posted by twhitehead
    An example of improving efficiency by cooling.

    http://engineering.stanford.edu/news/stanford-led-team-develops-self-cooling-solar-cells-last-longer-have-more-power
    Looks like a rather expensive process.
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