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Thread: These are really cool. Literally.

  1. #1 These are really cool. Literally. 
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    Solar panels. What are the problems?

    One problem is the sun. If you don't have a tracking system you miss out on all but the best of the sunlight available.

    Another problem is the cost. Which is driven by the need to have the materials resistant to the heat generated by the sun exposure, overheating reduces the effectiveness of panels. (Which makes it less surprising that Germany can get such good results compared to a sunny but hot place like Australia.)

    How do you solve both these problems with one simple solution? The "panel" is in the form of a cone .... which spins.

    Check this out. Solar power cheaper than coal: One company says it’s cracked the code | Grist

    I have no idea whether they'll be as successful as they're predicting. But I'm pretty sure there'll always be a niche market for installing something like this in specialist applications. Outdoor lighting and signage / signalling systems would be strong candidates for having something not-flat for generating their own power.


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    I don't really understand why this is better. To capture direct sunlight the best of all is a flat plate kept perpendicular to the sunlight. By picking the right stationary angle one can capture about 70%--you don't miss the best sunlight...you miss the worse. They didn't talk about indirect light. I see they have a type of fresnal magnifier on the sides, but their vid doesn't really show how this helps.

    Skeptical.


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    Forum Radioactive Isotope cosmictraveler's Avatar
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    I don't think this is a good idea either. To much money spent on sides that will never generate energy.
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    I think they are cheaper because they use smaller cell, but the low surface area of the small cell is compensated by the magnifying glass that concentrate a larger amount of sunlight into this small cell. A small cell mean its cheaper than a large panel of cells, but this mean a larger amount of heat concentrate on the cells and causes overheat, so they spin them inside those funny looking cone which cycle over other cooler cells. The spin then generate electricity like a conventional generator.
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    Given the size of the rotating cone shaped structure with solar panels attached at an angle, I wonder if the panels (those select few facing the sun) that actually do capture the usable sunlight be producing enough electricity to power it's own rotation and still have enough to be harnessed for our consumption. Does anyone have an idea how much power is required to rotate the cone shaper structure that is of an average person's height in weight and speed of rotation? Furthermore, wouldn't it's shape mean that the solar panels not ideally facing the sun will not be capturing usable sunlight sufficiently or at all?
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    40 years ago, at the design school, one of my fellow students designed a solar hot water heater that tracked the sun by moving fluid from a tank located on one side of the collector to another located on the other side.

    I don't remember the exact layout of components, but the thing actually tracked the sun, then returned to it's east facing(at rest) position when the heat of the sun went away at dusk.

    If anyone has seen such a design,
    Please post drawings
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    Quote Originally Posted by msafwan View Post
    I think they are cheaper because they use smaller cell, but the low surface area of the small cell is compensated by the magnifying glass that concentrate a larger amount of sunlight into this small cell. A small cell mean its cheaper than a large panel of cells, but this mean a larger amount of heat concentrate on the cells and causes overheat, so they spin them inside those funny looking cone which cycle over other cooler cells. The spin then generate electricity like a conventional generator.
    Spin seems too slow to be used to generate electricity, it would need to use a big boost with large friction lose to power a conventional generator--I suppose it could be done by induction, but that's usually not very efficient.

    Spinning doesn't mean cooling--so I don't understand how they are making that claim either. And the whole green flash mention just adds an overall feeling of woo to the presentation.
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    Depending on which reference you consult, it appears that 8 cents per kw hour is roughly what burning coal costs, and possibly a titch more than burning gas.

    Frankly, I do not believe it. The last solar cell estimate was about double that. You do not halve generation costs by putting solar cells onto a spinning cone. I would tend to see that as actually increasing costs, since you have to spend a lot more money on structure to get the same area exposed to the sun.

    However, time will tell.
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    Quote Originally Posted by sculptor View Post
    40 years ago, at the design school, one of my fellow students designed a solar hot water heater that tracked the sun by moving fluid from a tank located on one side of the collector to another located on the other side.

    I don't remember the exact layout of components, but the thing actually tracked the sun, then returned to it's east facing(at rest) position when the heat of the sun went away at dusk.

    If anyone has seen such a design,
    Please post drawings
    I have never heard of a water tank doing that, but I have heard of a house doing that.

    The Heliotrope House Automatically Follows The Sun Like A Plant | Fast Company

    Heliotrope (building) - Wikipedia, the free encyclopedia
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  12. #11  
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    I've seen others that tracked the sun via motors
    .............
    the one I had in mind, had a dividing fin down the center, and a small tank on either side close into the center.
    The fluid(water with antifreeze) would move to the side in the sun, tilting the collector so that the collector faced squarely into the sun----------
    if memory serves, there was a small collector through which the fluid flowed from the tank on the cold side to the one on the hot side
    and
    that served to optomoze the collector which warmed water that then went to an insulated tank for domestic hot water
    (i'm guessing that the small collector(s?) within the collector that tilted the collector were for the opposing tanks)

    ............
    also
    if memory serves,
    the class was working on dampening methods to make the thing more stable, and less prone waggling about in the wind
    .............

    jeez
    (13 years, 5 universities, all that education, and my memories are like unto a precious fluid stored in a sieve)
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    I think the general idea is this. You save money on PV cells because you don't cover the whole surface with PV cells. Most of it would be a lens that focuses the sunlight on the fewer PV cells. Normally, that would fry the PV but if you keep it rotating, it cools during the time it rotates out of the direct rays. You wouldn't want it to track the sun. That would be fatal.

    One problem would be if the motor rotating it ever stops, you will end up with some fried cells. And, of course, they haven't solved the intermittency problem inherent with all solar.
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  14. #13  
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    Quote Originally Posted by Harold14370 View Post
    One problem would be if the motor rotating it ever stops, you will end up with some fried cells. And, of course, they haven't solved the intermittency problem inherent with all solar.
    And added some down time from the out of focus parts of the spinning. Thanks for the explanation though--it makes some sense--though the claims still seem widely exaggerated.

    I'd also worry about the stress on the chips from continuously cycling between heating and cooling.
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    Would the solar cells get fried or just be ineffective whilst too hot and work just fine when they cooled down again? The fundamental materials can be quite heat tolerant.

    I think this is a solution but not necessarily the best solution to high cost of solar cells and the loss of efficiency from the heat that arise from mirror or lens concentrators. The greatest gain here is through the use of a lot less cells but the means used to keep them cool adds mechanical complexity that is likely to make a very reliable technology less reliable and add to maintenance costs.

    I would point out that what suits a domestic rooftop is different to what suits a dedicated solar farm and other solutions including dedicated cooling systems for mirror or fresnel concentrators, on the face of it, make more sense. Meanwhile a variety of innovations continue the trend of PV getting cheaper - the fixed, no moving parts solution does make for simplicity and reliability.
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    The fundamental materials can be quite heat tolerant.
    Not really. One of the contributors to the costs of panels is the use of substances resistant to heat - because a panel's production of energy is severely affected by excessive temperature. One of the reasons why PV in hot sunny places doesn't have as much of an advantage over cooler cloudier places as an ordinary person might expect. And let's face it, the heat of an ordinary Australian roof at 3pm on a sunny 38C day is pretty high, let alone inside a glass sheet that's concentrating the energy it's subjected to from the sun.
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    Adelady I don't dispute that high temperatures reduce PV efficiency during use but do they permanently degrade or 'fry' the cells as Harold claims?
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    Well, I had a quick look at a few references. They only talk about output voltage being affected, not about the panel itself being damaged - though there were a couple of mentions of inverter damage when you've got your parameters for the array out of whack.
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    Here are some articles that mention possible cell damage due to heat and/or thermal cycling. You can imagine the problem would be much more severe if you are focusing sunlight on them with lenses.
    Solar PV and thermal
    Any failure of the coolant to circulate through blockage, leakage or other reason, could result in damage to the solar PV array through overheating.
    SolarWall PV/T (photovoltaic thermal) - SolarWall solar air heating technology merged with PV electricity generation, for a solar heater PV co-generation system with increased efficiency over typical PV
    The cooling effect allows the PV panels to operate at their rated electrical output and also prevents damage caused to PV modules caused by overheating.
    Repairing Broken Solar Panels | Otherpower
    Another common problem is loose solder connections--some connections are intermittent and cut in and out as the panels heat and cool.
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  20. #19  
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    Thanks Harold. The potential for a simple mechanical failure leading to cells being permanently damaged would need to be a serious consideration for design and materials selection - a long and reliable working life is important. I'm not convinced about this particular design. The combination of water heating and PV makes some sense to me; solar hot water systems that have the water storage above the collectors are very reliable and unlikely to result in loss of coolant over a 20 - 30 year working life. PV using fresnel concentrators would probably work quite well with them - but fixed flat PV panels are proving to be very reliable and increasingly affordable. Manufacturers of combined heat and electricity systems are entering a competitive market.
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  21. #20  
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    To Ken

    Those are sensible comments.

    Thermal solar is still too expensive and likely to remain that way. Photovoltaic cells have dropped in price considerably, and continue to do so. They should become an important part of the total generation package in time.
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    The combination of water heating and PV makes some sense to me; solar hot water systems that have the water storage above the collectors are very reliable
    And cheap!! We had a PV large storage water heater at our previous house. Hadn't paid more than a handful of dollars per year for hot water - we had the power backup turned off for all but the shortest days/ coldest weather weeks of the year. Now? We've installed PV at this house. We look to be getting a credit for spring and autumn, how much the power bill will be for summers and winters will depend on severity of weather. (We had no air conditioning for our high ceilinged, large rooms at the old (very old) house, and we heated mainly with firewood.

    So despite getting PV for the whole house, the lack of solar water heating means that we're not as much better off as I'd expect to be given our previous experience with a house 3 times the size and accommodating 4/5 people rather than 2. (I think this comes directly out of the catalogue of 'first world problems'.)

    Though there's one technology that might be very attractive to a lot of people if it pays off. Water Heater Energy Storage: “Inefficient” Electric Heaters May Have Role in Smart Grid « Climate Denial Crock of the Week Using existing electric heaters and seeing value in larger storage heaters appeals to me. Partly I think there's an element of perverse glee for me in seeing a lot of (rather facile to my way of thinking) public advice that large hot water storage is inefficient or uneconomic. If it's solar hot water that is simply rubbish!

    We were able to run our household of 4 people who showered daily, sometimes more, as well as using a dishwasher and regularly doing laundry in hot water without ever needing a single electron from the grid to heat the water. If I wanted to do a lot of hot water washing, I'd simply do it early in the morning. The PV operating through the middle of that day was enough to get the water hot enough for ordinary use until the next day of maximum sun.

    If that conversion thingie works out to be economic, it might make recharging EVs a lot easier, certainly cheaper. Use PV to heat a largish volume of water, use the converter for x hours of recharging your car. Even if it's not very wonderful to start with, being able to charge your car for free for an additional hour or two each day, even if you have to use grid to top up to full charge, makes the whole idea a lot more doable. And for cars that are only used 2 or 3 times a week, you'd probably be able to keep it fully charged with no grid supply at all.
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    Always admired the gravity feed solar water heaters..nothing could be simpler in places where freezing isn't a problem. Proven tech that's been adopted on a large scale in some places (unfortunately not the Southern US).

    With PV continuing to slide in price though--direct resistance heating is starting to look even better, especially in cold places. I plan to take a good look at direct solar electrical preheating the next time I move. PV to DC resister preheater tank to conventional hot water tank. Should be very simple and reliable.
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    Whilst I'm not impressed with the rotating solar module, I have come across an interesting way to make PV concentrators that avoid the overheating problem by concentrating specific bands of light. Holographic film that is low cost is used both to focus the light and filter it.

    In contrast to other concentrator modules the distance between optic and solar cell is only a few millimeters and filters only the desirable wavelengths of the light. The sunlight is then concentrated on the solar cells. “Thanks to this specific wavelength selection, we avoid overheating issues usually generated by concentrated technologies which are today the source of significant efficiency losses,”
    They are claiming 28% efficiency - higher than most commercial panels - which also translates to reduced per Watt installation costs.

    The well of innovation is a long way from drying up.
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