Sun Plate Solar: Thoughts?

desert_sasquatch

http://www.sunplatesolar.com/sunplate-solar-collector-technology/

I found this, I wonder what folks here think. Supposedly these folks have come up with a new kind of solar thermal pane, which I gather involves coating the underside of an aluminum(?) plate with some kind of material that radiates infrared radiation. Since the material radiates infrared at a higher rate per unit temperature difference than aluminum does, I guess they figure that if they warm up the metal plate with this stuff on the underside, the underside will radiate the heat to whatever tubes need to collect the water.

Alleged benefits include:

-Avoids issues with differential thermal expansion of the glass vs metal
-Avoids issues with the shape of the metal (it could be made of two pieces of extruded aluminum, and the seal on those should hold better than the one on a typical flat plate. So there won't be corner joints that have to be sealed in a weird way. And the shape could be made to keep water out, better, though honestly I'm not sure if they care about that or if they should.)
-It won't heat up and cause polyurethane to degrade (some panels use mineral wool instead I think but they don't mention that).
-It won't overheat in general, as they could design it with just the right amount of insulation so that the temperature won't go above three hundred and...something...Fahrenheit. Some temperature at which certain materials started to degrade, I guess. I'm a bit confused about why this is.
-It would be more rugged--that is, there would be no glass to break.
-Cost: They say that, per unit surface area, it would be about 40% less than an "average" quality flat plate collector and about the same as a cheap chinese evacuated tube collector. Perhaps they have that backwards? Because I'm pretty sure it's the flat plate collectors that cost about 60% as much as the evacuated tube collectors and not the other way around.

Other than my slight confusion about the maximum temperature thing (does that work because the hot collection surface is exposed to the air? But then how are they saying it competes with flat plate collectors for temperate climates?) What they say makes sense. A design like they suggest does sound like it would be quite durable and I can see why it would be cheaper, if their product works how and costs what they say it does...

Jamie Hall

If their physics is right, no reason why it shouldn't work. I'd be interested in what they are using to reduce the infrared emissivity vs. visible light emissivity -- but I expect that is buried in the patent or is a trade secret.

It would have to be rather inexpensive to be worth the extra cost if any.

desert_sasquatch

They claim that the cost savings comes from not having glass and not requiring copper fins to absorb the heat. And possibly not requiting copper pipes on the inside? I'm not clear what they use instead, though. Maybe the entire inside--at least the front surface where there's no insulation--is just filled with fluid? Or maybe not, I'm honestly not clear. But if those two costs could be cut--copper and glass--that would certainly help reduce the price...

hot_rod

What exactly is the patented "opaque cover?

Seems like they are not far from FSEC where most all manufacturers send collectors to get an actual certified performance rating and listing. I wonder why there is no listings?

Once a collector is tested, listed and has performance data, then you can accurately compare different collectors under any operating condition.

The slope and intercept plots on graph paper to give you a performance curve.

the Idronics I suggested explain how to do the number crunching.

Here is an example of a listing.

desert_sasquatch

They claim that the cost savings comes from not having glass and not requiring copper fins to absorb the heat. And possibly not requiting copper pipes on the inside? I'm not clear what they use instead, though. Maybe the entire inside--at least the front surface where there's no insulation--is just filled with fluid? Or maybe not, I'm honestly not clear. But if those two costs could be cut--copper and glass--that would certainly help reduce the price...

That said, I called them and got an older latino woman who told me that I had the wrong number. So I think they've gone out of business.

Honestly my best guess is that their panel was not too different from an unglazed flat plate collector with insulation on the back side. Which was not an option covered in the idronics with the chart about delta T, energy output, and different kinds of collectors. But maybe that means the cold weather energy output would be a bit better than standard unglazed panels and a bit worse than standard glazed flat plate panels?

hot_rod

They mentioned getting them tested and rated on the SRCC list. As of today they do not show up? As a brand or company.
Not much market for solar thermal these day, regardless if how unique it is

desert_sasquatch

I was looking into the world of low-e coatings and I think I have at least figured out the special sauce in their design: The idea, presumably, was to put a low-e coating on the top side of the aluminum collector plate. Yes, it would still lose heat to the surface through convection--it would lose a lot more heat than a glazed collector would, as aluminum is of course much more conductive than glass and half an inch of air. However it would limit the amount of heat lost as infrared light. The low e coating would do that:

https://qph.cf2.quoracdn.net/main-qimg-bee9a9ae6735ded888668d13b9b7ce94

or also

https://glassed.vitroglazings.com/topics/how-low-e-glass-works



I think the above two images show that there are low e coatings that don't reflect much visible light but do reflect a lot of infrared light. Since a heated surface releases radiative heat as (predominantly?) infrared light, that would prevent a decent amount of heat loss as well. Right?

So if I'm understanding this correctly, I do see how this might work in theory. Whether these gains would be enough to make these panels worthwhile I don't know. I wish I knew what happened with the company.

hot_rod

The proof of viability would show if the collectors were sent to a lab for SRCC certification I don’t see that they ever got that far along
The lab at FSEC installs them outside under actual operating conditions for a period of time

A lab in Ontario puts them under lights and can better control variables like  wind, cloud cover etc. do a realtime output could be documented 

NREL in Colorado had been testing all solar thermal technologies for many years, they would have an opinion on low e glass, Im sure

Visit  their website, or see if you can get a tour of the facility