SunMaxx vs SunEarth vs Other Flate Plate Solar Thermal

desert_sasquatch

Why are SunMaxx flat panels nearly half the price of SunEarth?

I'm trying to understand the pricing and longevity of solar thermal panels. This thread was quite helpful. From it, I have the impression that flat plate solar thermal panels will last maybe 10-20 years depending on design (drainback?), care, glycol use, and the thickness of copper that's used for the pipes in the collector.

Someone mentioned SunEarth as a good company that had been around for a while so I got some quotes from them. SunMaxx's website provides their prices. I was surprised to find that SunMaxx's panels are half the price per square foot as SunEarth's while providing similar thermal output. Does anyone know why this is? Should I expect to "get what I pay for" with SunMaxx, or do folks think they're worth a go? Are there other reputable companies that folks would suggest I look into?

Thanks!

PS For folks who are wondering "why don't you just use a heat pump" the short answer is that I have some reasons that I address in another thread and understanding the cost of solar thermal panels is part of how I intend to do the cost-benefit analysis for my particular situation.

Larry Weingarten

Hi, Without knowing how these panels are built, a few things to check come to mind. How much does each weigh for the same size collector? Do they both have the same type of glazing? Glass or plastic? Glass holds up better and weighs more. How thick are the collector fins, and what metal are they made of? Copper fin, soldered to the tube is probably the best conductor, particularly if the fin is thick. Aluminum or steel fins don't conduct nearly as well and have corrosion problems. What is the surface of the collector... black paint or black chrome? The chrome if good if you need higher temperatures. How well insulated and air-sealed is the box? Have you compared the SRCC ratings on the collectors?

Rounding up all that info should help give a feel for which panel to go with. Of course, warranty and availability of product and service all matter too.

Yours, Larry

ps. Going for the most efficient collector isn't necessarily the best choice. Black chrome is quite efficient, but can also get quite hot, ruining glycols, which turn acidic and eat up the collectors. The lower the operating temperature you can use, the less efficient collector you can make work. Lower temps will likely translate to longer equipment life.

desert_sasquatch

Thanks again Larry.

SunMaxx TitanPower does use aluminum fins. I assume the pipes are copper and am waiting to hear back on what the thickness is. They warranty the panels for 10 years, allow an extension of that warranty to 20 years but only for some commercial applications, and claim the panels should last 30 years (I assume that's "if taken care of properly"). The covering is "low iron tempered mistlite glass." It weighs just under a third of a pound per square foot. They use mineral wool insulation, which will not deform or lose the ability to insulate if it gets wet (it has to dry out before it can insulate again but these are solar panels so if it's not drying out I figure there's probably a leak).

SunEarth Empire panels use a copper plate for absorption, although it also has an "aluminum copper absorber" (what does that do?). They use copper tubes (Type M). SunEarth warranties their collectors for 10 years to be free from manufacturing defects. A basic 10 year limited warranty. The covering is "low iron prismatic/matt tempered glass". It weighs just under a third of a pound per square foot. It uses fiberglass insulation which does concern me slightly as I'm told that fiberglass will deform when wet and will never regain it's former insulative potential. But hey, this is an old company that's been doing this for a while so maybe they just haven't found that this is an issue.

SunEarth has slightly better SRCC performance ratings, but we're talking +10% and only on good days--on bad days they're about the same, or SunMaxx is slightly better.

So if I just went by the SRCC ratings, warranties, and prices...at the end of the day SunMaxx is still half the price of SunEarth for what looks to be about the same product.

But obviously looks can be deceiving so...I thought I'd ask for some expert opinions

desert_sasquatch

PS RE the low temp systems thing: My thoughts thus far have certainly been along those lines (though obviously I'm still learning). But my impression thus far (and obviously folks should correct me if I'm wrong) is that it seems like if I can keep the temperatures low enough then the flat plate collectors will be about as useful as the evacuated tubes on the whole while costing less, lasting longer, being easier on the system and probably requiring less maintenance.

Larry Weingarten

Hi, Just my opinion, but the less expensive panel is probably fine as long as it stays dry inside. The aluminum to copper connection must stay dry to prevent corrosion between the metals. Another thing to consider is whether the glass is in one or two pieces. I like two as it's easier to handle, particularly if there is any breeze. You want fairly easy access to the inside of the box in case there is ever freeze damage.

Yours, Larry

desert_sasquatch

Thanks @Larry Weingarten that's quite helpful. I'll ask them about those things.

solradman

Hi, I'm a big fan of the Sunearth Thermoray Series and drainback systems. Looking at the numbers the TR series is up to 20% more efficient than the Sunmaxx and I know they will last 40 years as I have them out there. Sunearth has a beefier bronze anodized alum frame vs a lighter powder coated frame for the Sunmaxx. Not a big fan of their o-ring connections either. Solradman

hot_rod

Country of origin is another factor in the cost.

The thickness of the copper tube, copper absorbers, aluminum frame, low iron content glass, size of the collector.

The SRCC has the performance numbers at their site.

So only a few places to take cost out, materials, and labor cost

desert_sasquatch

Thanks you guys. I admit that a 40+ year lifespan does sound nicer than 20-30 years. Though I also wonder if those older panels were using Type L or K copper pipes when the current SunEarth panels use Type M (I asked them about upgrading to Type L--they say they'll get back to me).

Interesting about the powder coated vs anodized frame thing. And the O Rings. @solradman were you talking about the flat plate panels specifically? I ask because I've read things (on this site) about their evacuated tube collectors having a few issues, but I was kind of hoping that the flat plate collectors might be less problem-prone.

hot_rod

Yes the absorber gauge and the copper tube wall thickness has gotten thinner over the years. I have some 1970. Intake absorber plates and they are twice the thickness of the current offerings.
I believe AET,Sun Earth, and Heliodyne, all US manufactured collectors, use a tube that has the absorber welded or soldered onto the tube. AET calls it a forge weld connection, done with heat and pressure. You will rip the tube apart trying to pull it apart.

Be interesting to see how an aluminum absorber is attached. Look at any AC coil or hot water coils and aluminum fins are crimped on.

As a manufacturer you send your collector to an independent lab for performance testing. The Florida labs do outdoor tests, others you powerful lights in a booth. ASHRAE developed the standard that you test to.