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  • russ
    replied
    On the other hand, Parabolic solar PV concentrators do work and provide both warm water plus electricity. They still require a special circumstance to make them economical.

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  • J.P.M.
    replied
    Originally posted by Sunny Solar View Post
    I let you all intO this secret. Where I work many engineers before me had tried to make water cooling cost effective.. They got close because 10 yrs ago panels were expensive.. I thought they just didnt try enough variations. So Ispent weeks trying to come up with something thEy had not tried or thought of.. Sadly for me ended up giving up.. now when Isee someone else trying I know they wont do better.. thats life..
    It's common sense to try to get as much out of a process as possible. Folks been doing it with machines and heat engines/pumps for as long as there has been a need for them, and that's even before Carnot and Clausius. To folks who work and make money finding new applications for such an old and common sense concept, the idea of combining solar thermal and solar PV is pretty much a no brainer.

    Sometimes it makes engineering sense, but as Sunny Solar implies, the economics probably aren't there for flat plate solar for most small scale applications. Practical difficulties most likely also get in the way at the smaller level. Some things just don't scale well.

    To my experience, the smart money doesn't put the cart before the horse and try to prove what may be an unsound concept before, and without, seeing what's already been done, and testing the idea against known scientific and engineering principles.

    Lots of fun maybe for its own sake and so needing no further, if any justification. But to expect to be taken seriously and not embarrassing yourself in the process seems to me like an exercise in futility, as was, IMO, most of this thread.

    Most of the time, the lower the entropy increase for a process before any energy scavenging is attempted, the harder the economics are to justify for grabbing extra energy that would otherwise go to waste. The scale of any such scheme often also plays a big part. A power plant operating on a thermodynamic cycle through a high temp. diff. will have more ways and opportunities, and have those ways easier to cost justify than most solar processes usually operating closer to the limits imposed by entropy.

    For example, a municipal power plant that provides district heating using once through condenser cooling water has an entirely different set of practical considerations and opportunities for energy scavenging than what is mostly a once through spray condenser/film cooler on a small solar array that:

    - Wastes most of the cooling water used
    - May well be bad for the equipment and the roof
    - May inhibit or decrease long term performance of the original array
    - May well take half as much energy to run as it saves -

    That's for starter's, but no way to tell any of the above because of the ignorance of what's involved or the possible/likely consequences. That's the sad part.

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  • Sunny Solar
    replied
    I let you all intO this secret. Where I work many engineers before me had tried to make water cooling cost effective.. They got close because 10 yrs ago panels were expensive.. I thought they just didnt try enough variations. So Ispent weeks trying to come up with something thEy had not tried or thought of.. Sadly for me ended up giving up.. now when Isee someone else trying I know they wont do better.. thats life..

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by pleppik View Post
    Whatever.

    Since I actually used to teach thermodynamics, this is a topic I happen to know a thing or two about. I'm happy to teach it again if you ever change your mind. I've learned not to take the insults personally, since you do that to everyone.
    So then you know the difference between the Carnot efficiency limit based on temp. and the Thermodynamic efficiency limit for various solar cell technologies having something to do with band gap energies, right ?

    I spent an engineering career completely separate from solar energy, using, among other things, the disciplines of heat transfer, Thermodynamics and fluid mechanics to analyze, engineer and design processes, devices and systems that wring as many BTU/Joules/calories/whatever as possible out of any number of processes and schemes. Some were workable. Others, not unlike that cluster function on u-tube presented with this thread, but all on an industrial scale. Cooling towers and spray condensers for power plants and other applications come to mind, as do any number of such things as economizers, preheaters, condensers and power boilers, etc.

    This thread would be a comedy if it weren't so sad.

    My point is, the u-tube video shows me yet another example that what can start out as a fun learning experience can turn into a waste of time and resources, which in the end winds up doing little more than backing into some preconceived notion of a point to prove if the learning opportunity is not backed up by some academic critical thinking and discipline, and some knowledge of the required subjects.

    Probably one of the more common failings of a lot of DIY endeavors. Lots of fun maybe as long as you don't take it too seriously without at least some smattering of disciplined technical support at some point.

    One brief example: Any evaporative cooling effect of the type discussed in this thread is a rather strong function of the atmospheric dew point - saturated air will get you zero evaporative cooling - something the OP and everyone else so far seems to have missed.

    As I suggested in a prior post to this thread, without instrumentation and the data that instrumentation provides, this exercise may be a lot of fun, but leads to nothing substantive in the way of new knowledge or how to make use of it. I'm also quite sure that such instrumentation would show the lack of economic viability for the process. Been there, done that many times. Usually the stuff of something called Process Economics. Make it work, then justify the cost.

    Take what you want of the above, if any of it. Scrap the rest.

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  • Sunking
    replied
    Originally posted by pleppik View Post
    Whatever. I've learned not to take the insults personally, since you do that to everyone.
    Well then you have done good, because I never mean them personally. That is just the military in me.

    All I'm trying to say is this idea is not new. Universities, scientist, and engineers have tried 9 times to Sunday for the last 20 years to make it work. That group are my superiors and peers, and when they tell me it cannot work economically or establish a positive EROI, I believe them.

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  • pleppik
    replied
    Originally posted by Sunking View Post
    I don't want to waste my time. I trust my peers who have tried for 20 years. I am not a kid who has to stick my hand in fire to see if my Dad told me the truth or not.
    Whatever.

    Since I actually used to teach thermodynamics, this is a topic I happen to know a thing or two about. I'm happy to teach it again if you ever change your mind. I've learned not to take the insults personally, since you do that to everyone.

    Leave a comment:


  • russ
    replied
    Originally posted by bouncintigger View Post
    Irrefutable anecdotal evidence... The best kind.

    sigh...

    Thanks pleppik for saving me some typing!
    You mean for using the big words you don't know about nor understand?

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  • bouncintigger
    replied
    Originally posted by Sunking View Post
    I don't want to waste my time. I trust my peers who have tried for 20 years. I am not a kid who has to stick my hand in fire to see if my Dad told me the truth or not.
    Irrefutable anecdotal evidence... The best kind.

    sigh...

    Thanks pleppik for saving me some typing!

    Leave a comment:


  • silversaver
    replied
    That reminds me of Vapochill from 20+ yrs ago when I use refrigerated cooling for my pc..... Just trying to make it runs a little faster. (which it did....)

    More efficient and heat resistance panels will be out way before an economical cooling system..... just look at CPU cooling device.

    Leave a comment:


  • russ
    replied
    Originally posted by Sunking View Post
    I don't want to waste my time. I trust my peers who have tried for 20 years. I am not a kid who has to stick my hand in fire to see if my Dad told me the truth or not.
    You got it Sunking!

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  • Sunking
    replied
    Originally posted by pleppik View Post
    This is true only if the efficiency is already close to the Carnot limit. For example, in a heat pump or a gasoline engine.

    But the efficiency if a PV system is so far from the Carnot limit that there's a lot of room to improve the efficiency without running afoul of the second law. Go ahead and do the calculation if you don't believe me.
    I don't want to waste my time. I trust my peers who have tried for 20 years. I am not a kid who has to stick my hand in fire to see if my Dad told me the truth or not.

    Leave a comment:


  • pleppik
    replied
    Originally posted by Sunking View Post
    Not money but the Law does answer the [/COLOR][COLOR=#3e3e3e]entropic question. You will spend more energy in cooling than you will get back in higher production aka EROI is negative.
    This is true only if the efficiency is already close to the Carnot limit. For example, in a heat pump or a gasoline engine.

    But the efficiency if a PV system is so far from the Carnot limit that there's a lot of room to improve the efficiency without running afoul of the second law. Go ahead and do the calculation if you don't believe me.

    Leave a comment:


  • Sunking
    replied
    Originally posted by pleppik View Post
    Before you go for the extra-bold text,
    The bod text I could not turn off for some reason. I tried using smaller text, different font, you name it. It just got stuck.

    [COLOR=#3E3E3E]The question is whether the extra cost and complexity of the cooling systems are worth it financially, and last I checked there was no second law of thermodynamics for money.
    Not money but the Law does answer the [/COLOR][COLOR=#3e3e3e]entropic question. You will spend more energy in cooling than you will get back in higher production aka EROI is negative. To be of any use would have to be positive of a factor of 6 to 8 just to pay for itself. Exact same reason Hydrogen is only 5% efficient from cradle to grave. It has already been tried thousands of times already. If it worked there would already be a workable system out on the market.

    [/COLOR][COLOR=#3E3E3E]If you think it will work I wil sell you a working HHO system for your car. I am the only one who has figured out how to make it work..... NOT!

    [/COLOR]

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  • pleppik
    replied
    Originally posted by Sunking View Post
    [h=1][SIZE=4]bouncintigger [COLOR=#000000]as I sated in my first replay you are only the 10,000 person to go down this road. Th eones before you are much smarter and informed like engineers and scientist. You are fighting the Law of Physics and cannot change those Laws no matter what. It is the same reason you cannot use a trampoline to get into orbit, or pull a train with a motor cycle. You will never recover the energy you put into cooling. You are wasting energy, not making it. [/COLOR][/SIZE][/h][SIZE=4]
    However if you can do it, prove it, and patent it, I will pay you $1 million USD to license the system and pay you a royalty for every system I sell. We will both be able to buy our own countries. You can be the CZAR of Down Under, and I will own the rest of the world. You will be able to afford to have Bill Gates as your Butler or Slave. [/SIZE]
    Before you go for the extra-bold text, you might want to crack open your old thermodynamics textbook and refresh your memory about what the first and second laws actually say. Nobody's claiming that by cooling solar panels to increase the efficiency you're creating energy or getting more useful energy from the sunlight than should be physically possible.

    By cooling the PV array you are reducing some of the inefficiency of the semiconductors caused by heat. So your normally 15% efficient panel goes up to 16% efficient because it's cooler. But both 15% and 16% are absurdly far below the theoretical entropic limit for solar efficiency (remember that the energy source is at 6,000C, and the sink is around room temperature--that leaves a lot of room for extracting useful work).

    The question is not whether you can net more energy from PV by cooling the panels. You can, and this is very well established. The question is whether the extra cost and complexity of the cooling systems are worth it financially, and last I checked there was no second law of thermodynamics for money.

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  • Sunking
    replied
    [h=1][SIZE=4]bouncintigger [COLOR=#000000]as I sated in my first replay you are only the 10,000 person to go down this road. Th eones before you are much smarter and informed like engineers and scientist. You are fighting the Law of Physics and cannot change those Laws no matter what. It is the same reason you cannot use a trampoline to get into orbit, or pull a train with a motor cycle. You will never recover the energy you put into cooling. You are wasting energy, not making it. [/COLOR][/SIZE][/h][SIZE=4]
    However if you can do it, prove it, and patent it, I will pay you $1 million USD to license the system and pay you a royalty for every system I sell. We will both be able to buy our own countries. You can be the CZAR of Down Under, and I will own the rest of the world. You will be able to afford to have Bill Gates as your Butler or Slave. [/SIZE]

    Leave a comment:

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