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Like I wrote - whatever you say.
Usually and often, I agree with most of what you post. FWIW, it seems to me I'm discussing things quite pertinent to the subject matter as raised by others, but in a more global sense and based on some of what I think I may know with respect to improving efficiencies of power processes as raised by others. I don't believe discussions of means of improving combustion process efficiencies is something that belong in this thread anyway, and I wasn't the first to broach that subject, but I do believe I may know something about that end of mechanical engineering from both a practical and academic perspective.
My reference to wasting my time was in that I seem to be discussing such issues in a way you and perhaps others are not in a place to be able to see or understand. I forgot one of the cardinal rules I leaned as a peddler: Always play to the audience. My bad.
As usual, take what you want. Scrap the rest.Comment
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A> You haven't stated anything that contradicts my statement of how a turbo/supercharger adds to an engine.
B> Oxygen isn't a fuel, it's an oxidizer.
C> A supercharger does not increase the amount of oxygen in the air around the engine - just like a cooling spray of water doesn't increase the solar energy hitting solar modules. A supercharger *does* allow the engine system to output more, just like cooling solar modules allows the net system (solar modules + pump for cooling spray) to output more electricity.
There are a lot of parallels - like "Can I just go bigger instead of using this extra thing?" - which of course you can and that's probably a better choice a lot of the time.
Or "Isn't there more upfront cost?" - and yes, there are in both cases.
Or "Isn't there likely to be more maintenance?" - yes in both cases.
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From my perspective you appear to be discussing a different (but similar) system than what was being discussed.
For example, the term "thermal scavenging" to me implies that the energy is being collected for some use - which is different than the system being discussed which is using evaporative cooling.Comment
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Most of the systems that combine thermal and PV do so primarily for the purpose of recovering some of the ~ 70 - 80% of the solar energy that is rejected as heat by a PV system. The increased PV efficiency that is the result of lowering the array temp., while not to be ignored, is secondary in terms of economic benefit. Cooling PV panels, if done at all, is never done for that reason alone. The OP may think so. The smart money doesn't.
If panel cooling is done for that reason alone (increasing PV efficiency), and the (recovered) heat in the working fluid is simply dumped as the OP seems to be doing, the economics are a real stretch, which is why most all of the literature describing these things deals primarily with the heat recovery aspect.
I disagree that the two processes are different. In each case, heat recovered and used as process heat or some HVAC purpose, etc., or simply dumped, solar energy is transferred from a PV array to a working fluid. As long as the energy collected by the working fluid is then dumped or not considered to have economic value, the process is the same up to that point.
Whether it's called heat recovery or scavenging - Whether you know/like the term it or not, a common or at least well known term among those who do such things for a living BTW - or (plug in your favorite term here), in the end, both the practical and experiential/academic aspects of getting the most out of a process for the input presented is the goal.
In an academic sense, both the heat recovery and the increased PV efficiency will be important for the curious/academic. Lots of white collar welfare master's theses will attest to the veracity of that statement. As for the practical aspects, few of the types of systems that dump the recovered heat and rely only on increased PV efficiency as a figure of economic merit, as the OP seems to be doing, are in use by any outfit or individual that's concerned about the practical/economic aspects of the process. Great fun to play with - I do similar stuff all the time - but if it was economically viable or practical, and another buck could be wrung out of the large arrays by doing so, you can bet your butt there would be a lot of heat scavenging going on. There is little. Look around. It's mostly impractical and uneconomical, and an idea who's time has not yet arrived for systems that consider both thermal recovery and PV improvements, much less those that only consider the increase in PV efficiency, and dump the heat.Comment
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It's similar but different IMO.
With a heat recovery/scavenging system, the point is to take the heat and do something with it, which means significant additional equipment is required (which must be paid for by the benefits of the system.
With a cooling system the additional equipment needed is dramatically reduced - the heat doesn't need to be transported by the fluid to another location to be used - it is removed from the module by evaporative cooling.
In a heat recovery/scavenging system, as you point out the benefits provided by the heat captured is the bigger consideration - that is most of what would be used for determining the ROI.
In a cooling system it's only the electrical production increase that is the benefit. It's (assumably) a lower benefit - but significantly lower initial cost.
I completely agree it's not economically viable on a commercial scale.if it was economically viable or practical, and another buck could be wrung out of the large arrays by doing so, you can bet your butt there would be a lot of heat scavenging going on.
Even as a DIY scale where labor is zero and soft water is easily available, I think it's probably not a huge win.
But that's a quite different discussion than the claims made that the idea is a perpetual motion machine and a scam.
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You can make the case that the economics, while not great in either case (I agree that it would be in wide use if it was) would actually be better for the open system. The materials costs and the relatively simplicity would be the reason why. If I add up all the components in the system, rounding everything up and adding on an extra $50 to cover all the small bits (hose clamps, 3D printed parts that I designed and used, etc.) it is around $360. $100 of that is the 12V 12L/min pump used to spray the array. This includes the $50 for the RPi controller, even though I already had that and used it for other home automation tasks. Over the life of the system, you'd still be better off having more modules, for certain, but in some cases it might not be possible, and you would still see net gains from this cooling system.
And for the record: I would discourage anyone from trying to build such a cooling system thinking you'll get massive gains from your system. If you want to tinker and see how things work in your hands, I'd be happy to provide what I've learned. With that, I'll sign-off from the thread unless questions are directed at me specifically. I've got too much going on in RL to keep replying! Perhaps I will come back in a year and give you an update, just to annoy Sunking
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I wouldn't make that case based on what I think I know. I believe that logic simplistically ignores the real and practical operational and construction considerations of what you call an open system. An evaporative system will have, as a practical matter, some, maybe a lot of liquid run off to be handled. Where will it go ? How will water damage to the structure from more/less constant moisture exposure be mitigated or designed for ? Odor/bacteria control ? Noise? Aesthetics ? Building codes/Permitting ? Cost? Not to mention the possible likely performance deterioration from the scaling (and for the rainwater argument, note the often cleanliness of the atmosphere after a rain - where do you think the dirt/suspended solids went ?) The list goes on. I'm betting it's not as simple as you seem to want to make it. Because they have not been considered or known does not allow not the myriad design considerations to be ignored. Such is the common logic of what I call the "you could just" way of looking at the "big picture" and ignoring the details where the devil resides - usually from tree huggers and academics who don't know squat about engineering design and are incapable of keeping a dozen or more design balls in the air and balancing them all to produce a safe, workable, serviceable and cost effective system or piece of equipment.
You can make the case that the economics, while not great in either case (I agree that it would be in wide use if it was) would actually be better for the open system. The materials costs and the relatively simplicity would be the reason why. If I add up all the components in the system, rounding everything up and adding on an extra $50 to cover all the small bits (hose clamps, 3D printed parts that I designed and used, etc.) it is around $360. $100 of that is the 12V 12L/min pump used to spray the array. This includes the $50 for the RPi controller, even though I already had that and used it for other home automation tasks. Over the life of the system, you'd still be better off having more modules, for certain, but in some cases it might not be possible, and you would still see net gains from this cooling system.
And for the record: I would discourage anyone from trying to build such a cooling system thinking you'll get massive gains from your system. If you want to tinker and see how things work in your hands, I'd be happy to provide what I've learned. With that, I'll sign-off from the thread unless questions are directed at me specifically. I've got too much going on in RL to keep replying! Perhaps I will come back in a year and give you an update, just to annoy Sunking.
A closed cooling system presents far fewer practical design and operational potential problems. I'll agree that initial costs might well be higher, but problems and operating expense of an open system, evaporative or not, will soon overcome any savings in initial costs. Just an opinion.
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Maybe we should get together and test it with a bifacial panel to really bother J.P.M.
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That might be a good way to show two things:
1.) How similar there performance is to one sided panels in most common situations homeowners would use.
2.) How little you actually know about solar energy applications.
One the other hand, both are probably obvious to anyone with one eye and one balloon knot, so another waste of time.
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I get the impression you think that you (or others that have studied as engineers) are the only ones that can come up with a list of considerations like you present. It fits in with your general condescending tone (which you always try to mitigate with: "take what you want, leave the rest"). Certainly there are some people who would jump into a project without going thinking it through, but I can assure you there are also intelligent people out there not trained as engineers. Every single thing on your list has been taken into consideration (if you look through the thread and comments you will see answers to many of them) and many others besides. That doesn't mean that everything can known in advance, and that is actually one of the things that is fun about tinkering: problem solving the details when something new arises. Would you not agree with that?Comment
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There is always a chance of reinventing something and finding a better mousetrap. The problem is not spending your money (or others) foolishly in trying to reinvent something like the wheel when IMO someone has done a pretty good job of doing it already.
Inventors and scientists have the need to fill a void that drives them. I was one back in the days when I worked in the research of solar cells at the University of Delaware. Imagine that. But I have also decided that at some point my time is better used to doing things that have been proven to make my life and others around me better.
If you have the time and money to research and invent then go for it. It can be fun and sometimes disappointing. Just don't let it bankrupt you.Last edited by SunEagle; 09-16-2016, 04:23 PM.Comment
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What Suneagle writes is true, and fair, but it doesn't get at the core of shocksofmighty's complaint: that J.P.M. comes down on people like a ton of bricks because he fears that unripe ideas will be taken seriously by the unwary.
I wonder if an 'Enthusiasts' subforum, specifically for the hotrodder and case-modder set, and explicitly labelled 'Don't try this at home', might address J.P.M.'s stated issue.
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