Solar Electric + Solar Water = Opportunity? (CoolPV)

[J.P.M.]

I disagree.

By the standards you've expressed on here, everything that we use today was once crap. 10% efficient panels, which browned when you exposed them to sun, Panels for $10/watt. Large stepped-waveform grid tie inverters that didn't meet interconnect (or EMI) standards. PWM controllers used on 10kW systems - which were often 12V, because that's what you could get inverters and controls for. If none of that had ever seen the light of day, we'd have no solar industry today.

These might be crap. I won't know until someone does some testing on them. If they turn out to be crap, then someone should take them and do a better job, as has been done thousands of times before in the solar industry. If testing shows they work, well - one test is worth a thousand Internet opinions.

I'd like - no - love - to see more information on any independent third party testing done on the products you wrote about (PVT or PV-Thermal products). That's one reason why I asked if you had more info.

After seeing scams like this for more years than I've practiced engineering, I'm quite sure testing would/will reveal the scant claims - more innuendo than claim actually - to be B.S. But, I've got enough confidence in my engineering experience and formal knowledge base to know that without more and better information to evaluate, solar energy products that use thermal solar energy equipment to recover waste heat from PV equipment will not work anywhere near either as claimed or implied unless they manage to violate the laws of Thermodynamics, heat transfer, fluid mechanics and a bunch of other engineering disciplines. They may work some, but nowhere near as claimed, nor be as efficient, nor as cost effective as claimed, or with anywhere near the reliability needed. They may not even be legal for sale in the U.S. For starters, I believe they'll need OG -100 or maybe OG - 300 testing and certification and depending on size and pressure rating perhaps A.S.M.E. certification and stamping as well. Butler has such an OG - 300 system cert. but it appears entirely PV without any solar thermal heating.

To your comment that by my standards everything we once used was crap: As to the everything part, I think I saw and owned and analyzed a lot of worthwhile products that were not crap: "RollBond" collector panels, embossed glazing - still in use and quite durable. I had some Solar King thermal panels at one time. Great product. I believe they are still in service with a friend back east, Solar storage tanks with multiple inlets/outlets. I've got a differential controller on my solar water heater that was made in 1985 on a '60's patent and still no failures on it. Everything was not crap. But a lot of bills of goods and hollow claims of the type still with us were crap.

I'll give you this : One thing that was and still is crap are the heat exchangers used on most residential and small commercial solar thermal systems. Reason: The people designing (if you can call it design) and selling them are clueless about HX design - just like the folks selling the products under discussion here. They're actually selling a type of heat exchanger and are clueless about it, and also clueless as to why it's not a viable product from an engineering standpoint the way they are going about it, or that its not likely to be practical or cost effective anytime soon with materials and methods currently available.

Point one is, everything is not crap. Point 2: There will always be people and outfits who don't have the knowledge to know the products they're pushing are not viable from an engineering or practical point. Or, they may know some but not much and certainly not enough, and have less integrity than engineering knowledge, or not much of either.

Jeff: You probably have engineering skills in areas I do not. You can probably, by virtue of experience, training and formal education, spot B.S. products in your field(s) just as I can in mine. Once such inadequate products are exposed, either by common sense, or analysis, or testing, or repeated failures, or whatever, by folks knowledgeable in their fields, the products will be gone, or at least more reliable information will be available and perhaps further analysis can be done, and possible improvements made.

So, I say, yea, lets see some reliable and independent third party testing. Yup ! I look forward it. Bring it on. PLEASE ! But, until we do see such information, and until I can review it using what I acquired from a P.E. career designing heat transfer and process equipment to satisfy my own skepticism, I say keep the products off the market. Until then, I'm calling B.S. on them just like I always have.

Respectfully,

[SunEagle]

I disagree.

By the standards you've expressed on here, everything that we use today was once crap. 10% efficient panels, which browned when you exposed them to sun, Panels for $10/watt. Large stepped-waveform grid tie inverters that didn't meet interconnect (or EMI) standards. PWM controllers used on 10kW systems - which were often 12V, because that's what you could get inverters and controls for. If none of that had ever seen the light of day, we'd have no solar industry today.

These might be crap. I won't know until someone does some testing on them. If they turn out to be crap, then someone should take them and do a better job, as has been done thousands of times before in the solar industry. If testing shows they work, well - one test is worth a thousand Internet opinions.

While I agree that something should be tested before it gets a recommendation or a condemnation, I have found that some people are easily tricked into believing what an advertisement states way before they even determine if it is true or not.

Posting false claims about solar hardware or equipment can do serious damage to the credibility of this forum.

So while it may not be the right thing to condemn something outright I would urge caution before allowing it to be advertised and supported on this forum.

[jflorey2]

Crap like this should never see the light of day.

I disagree.

By the standards you've expressed on here, everything that we use today was once crap. 10% efficient panels, which browned when you exposed them to sun, Panels for $10/watt. Large stepped-waveform grid tie inverters that didn't meet interconnect (or EMI) standards. PWM controllers used on 10kW systems - which were often 12V, because that's what you could get inverters and controls for. If none of that had ever seen the light of day, we'd have no solar industry today.

These might be crap. I won't know until someone does some testing on them. If they turn out to be crap, then someone should take them and do a better job, as has been done thousands of times before in the solar industry. If testing shows they work, well - one test is worth a thousand Internet opinions.

[J.P.M.]

Are you the least bit surprised by what you found considering the source? You were wise to investigate.

I don't have any problems with Jeff, if that's what you mean. My large and ongoing 40+ yr. beef is with the con men who peddle this crap, and the industry which seems overpopulated with engineering wannabees who wouldn't make a wart on a real engineer's ass, and so, more than likely, couldn't make it in the real engineering world and don't know bad and unsafe engineering when they see it. That the industry can't or won't police itself and get rid of the obvious cons is one result of that lack of professional engineering depth.

No disrespect here, and not a knock, but different from you (I think), I see R.E. and solar energy in particular as having potential to make a viable and cost effective contribution. What's often holding it back is the assholes who do stuff like this, hurt credibility and do little more than glom off the ignorant.

I want solar to succeed. What's obvious to me after a career working with and luckily being mentored by some real world class engineers doing real engineering is the lack of depth of real engineering talent in alternate energy. Crap like this should never see the light of day.

[Sunking]

Thank you. I rooted around some more and found something on the SolLink system as well as the Sundrum stuff.

I'm not a fear monger and I'm not prone to histrionics, but if I'm looking at the same stuff you're referring to, I've got to say, as a retired P.E. who spent a long time designing heat transfer equipment for many and varied applications, all to national and international codes and standards, what I saw from and of both offerings is pretty scary.

Are you the least bit surprised by what you found considering the source? You were wise to investigate.

[J.P.M.]

SPI is where I saw both. I'll see if I can find the pictures I took.

The SoLink panels had a fairly small (as a guess 3/8") tube running around a backplate. Several were paralleled to increase flow, but it was still pretty clearly a low-flow system - perhaps adequate for a DHW system, but not a great design for thermal transfer. The rep said that was to reduce weight so that standard racking could be used. They also offered the panels with three different types of cells, each with a different surface prep in different colors so they could match colors better on the roof. (i.e. they had a slightly reddish module, a very blue module and a few other colors.)

The Harvest/HP Sundrum had a massive 'flooded' collector on the back of the module, with ~1" fittings to get water in and out. Rep didn't know how much it weighed when full, but he talked about how they also sold a custom racking system for it, so I suspect it's very heavy.

Thank you. I rooted around some more and found something on the SolLink system as well as the Sundrum stuff.

I'm not a fear monger and I'm not prone to histrionics, but if I'm looking at the same stuff you're referring to, I've got to say, as a retired P.E. who spent a long time designing heat transfer equipment for many and varied applications, all to national and international codes and standards, what I saw from and of both offerings is pretty scary.

Seriously. Full stop.

Scary not only from the standpoint of what looks obvious to me like a general lack of understanding of heat transfer principles and engineering design common sense and so not incorporating those principals into a viable and safe design, but that such designs could even be considered marketable. I'd have been fired in short order if I ever came up with such garbage. And I'd have deserved it.

Briefly, for there is not enough space to do more than a surface scratch here:

For starters, the SolLink designers seem to lack any understanding of the critical importance of a good thermal bond across proposed heat transfer surfaces/boundaries and low thermal resistances (just like, and for reasons analogous to, good battery terminal connections with low resistances). I'm not sure how one gets a strong, reliable, and high conductance bond between a copper tube and the back of a PV panel, especially if the backsheet is not tightly and continuously bonded to the back of the panel. If it isn't, and I'm not sure how that would be pulled off on most all existing panels, the arrangement becomes more useless - if that's possible. Even if it could be made safe, the bond area is very small, and the panel fin efficiency is probably about an order of magnitude less than necessary to be considered an effective fin, which has a direct bearing on heat transfer effectiveness.

On the Harvest HP design, it appears the panel is being used as part of the pressure boundary. That won't work from any code standpoint. It's also dangerous. Even if it did work and could be made code compliant, and if all the little problems like venting, making allowances for trapped air, flow maldistribution, the inevitable heat exchanger fouling considerations, and other things too numerous to mention here could be addressed (which, it seems, the designers are also completely ignorant about), it's still a bad idea. If coolant is not flowing (as is likely in winter or other times), the heat exchanger strapped to the back of the panel will act as an insulator and the panel will operate at a higher temp. than if the device were not present. That would be counterproductive any time flow is interrupted or when the coolant is warmer or close to ambient with a wind vector present.

I also saw no consideration for freezing or complete drainage for either design.

All this makes no consideration for what PV mfgs. might think or have to say about it or what all this may do to warranties.

As I wrote, more of the same stuff that seems to have as its sole purpose to separate the solar ignorant from their assets.

Crap like this gives alternate energy a bad name and has done so as long as I've been around it and before.

[jflorey2]

Jeff: Can you point me in a direction where I might get a closer look at those designs ?

SPI is where I saw both. I'll see if I can find the pictures I took.

The SoLink panels had a fairly small (as a guess 3/8") tube running around a backplate. Several were paralleled to increase flow, but it was still pretty clearly a low-flow system - perhaps adequate for a DHW system, but not a great design for thermal transfer. The rep said that was to reduce weight so that standard racking could be used. They also offered the panels with three different types of cells, each with a different surface prep in different colors so they could match colors better on the roof. (i.e. they had a slightly reddish module, a very blue module and a few other colors.)

The Harvest/HP Sundrum had a massive 'flooded' collector on the back of the module, with ~1" fittings to get water in and out. Rep didn't know how much it weighed when full, but he talked about how they also sold a custom racking system for it, so I suspect it's very heavy.

[J.P.M.]

Nope. They make fairly conventional PV panels with backings that absorb heat. One intended for high flow applications (pool heating etc) one intended for low flow applications (DHW.)

Jeff: Can you point me in a direction where I might get a closer look at those designs ?

Thanx,

J.P.M.

[jflorey2]

There are two companies that make solar roof shingles. Completely useless.

Nope. They make fairly conventional PV panels with backings that absorb heat. One intended for high flow applications (pool heating etc) one intended for low flow applications (DHW.)

[Sunking]

Not Musk, but seems to me Musk and these folks learned their craft at con school, same as every shyster in every business endeavor. Musk is one of the biggest, but far from the only con man out there

Yes I know it is not Musk, but cut from the same cloth. At least PT Barnum gave you some entertainment value for your money.

[J.P.M.]

I looked too. Not surprised, looks like another Musk con job like solar roof shingles. Fools and their money will soon part ways.

Not Musk, but seems to me Musk and these folks learned their craft at con school, same as every shyster in every business endeavor. Musk is one of the biggest, but far from the only con man out there.

Such cons are a part, but far from all of what killed solar thermal in the '70's - that and tax credits that allowed the cons to flourish. Today's tax credits have produced similar effects on product quality and peddler honesty.

[Sunking]

BTW, I checked those two sites you referenced. I wasn't impressed by either. Long on pretty pictures, short on information. More shyster cons IMO. Seen it all before. They come and they go.

I looked too. Not surprised, looks like another Musk con job like solar roof shingles. Fools and their money will soon part ways.

[Sunking]

There are now at least two commercially available lines of panels out there that combine water heating and PV in one assembly - SolLink and HarvestHP. Whether or not they will be commercially viable, of course, remains to be seen.

There are two companies that make solar roof shingles. Completely useless.

[J.P.M.]

There are now at least two commercially available lines of panels out there that combine water heating and PV in one assembly - SolLink and HarvestHP. Whether or not they will be commercially viable, of course, remains to be seen.

In my professional opinion, they will not be viable much less practical, or cost effective anytime soon. Nor are they likely to be fit for purpose. Water and electricity don't go well together. Air as a working fluid has very poor film coefficients requiring large surfaces and pumping costs. It'll cost more energy to pump the air around than the differential increase in panel efficiency even when combined with reuse of the recovered heat. So, that leaves water as a working fluid, probably, as you suggest for pool heating.

A couple of off the top of my head reasons why such systems - using water - are not viable at this time: The most common scheme of separation between the thermal circuit and a PV (or other surface as in double wall heat exchanger) is a barrier, or more than one barrier between them. That barrier is often air, either completely intentional, or occurring as unintentional and unwanted but also unavoidable gaps left by incomplete joining of the surfaces. That by itself reduced heat transfer efficiency, increases thermal resistance just like electrical resistance from poor bonding/joining, and increases other problems and price. Then, there's the added material cost. Forget copper due to cost. That leaves aluminum, not itself cheap, particularly in the quantities needed, but only if material compatibility with pool H2O can be addressed - a bit of a challeng. Other materials will have lower thermal conductivity below usable or practical levels. Regardless of material, cyclic thermal expansion is going to be a problem, and as the thermal and PV surfaces undergo that cycling due to (hopefully, but not likely small dimensional differentials due to poor bonding) temp. differences between the thermal and PV sides. the bonding/contact will break down, the surfaces will separate more, guaranteeing that, even in the very unlikely event that thermal contact is good, it won't stay that way for long, with no or very unlikely possibilities for inspection and none for remediation.

That's just a start and a surface scratch.

After speaking with more than a few folks that seem knowledgeable about solar and PV design, my observation is that while they might know a lot about PV and solar PV design, they seem to know next to nothing about heat transfer or thermal design, much less mechanical design. Equally, on the other side, the heat exchanger folks not only don't know, but don't much care about PV.

Note: I'm not saying PV-T systems are impossible. Just not possible/viable at this time. In my experience, based on a pretty good knowledge of solar energy and a much larger body of professional experience in mechanical and thermal engineering design, helps me form the opinion that such systems, up to now, by and large have been poorly designed junk that the solar ignorant latch onto.

BTW, I checked those two sites you referenced. I wasn't impressed by either. Long on pretty pictures, short on information. More shyster cons IMO. Seen it all before. They come and they go.

[jflorey2]

There are probably no thermally effective and simultaneously cost effective ways to combine water heating and PV in one assembly that is both practical and serviceable.

There are now at least two commercially available lines of panels out there that combine water heating and PV in one assembly - SolLink and HarvestHP. Whether or not they will be commercially viable, of course, remains to be seen.