Solar Panel Collector type for Caribbean

[Papote]

I live in the Caribbean and am looking to get a solar water heater system. I’m looking into flat panel or evacuated tube system. I got an offer for an evacuated tube system with a stainless steel tank for a descent price. I have a 2 floor concrete house with a flat roof and no trees nearby. Given my location would the evacuated system be better? What should look for?


I got offered this ET system with installation for $1,300 plus tax
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[J.P.M.]

That's a batch heater. The concept works quite well in non freezing climates such as yours. I would offer an idea that you consider a flat plate collector system vs. the evacuated tubes. Less to go wrong. Usually, evacuated tube systems are more appropriate when higher temps, > 100 deg. C. for example, are required. Flat plate systems are usually less expensive as well. In general, and without getting into a lot of discussions of an engineering nature, flat plate (non evacuated ) systems are probably more appropriate technology for domestic water heating.

[Papote]

That's a batch heater. The concept works quite well in non freezing climates such as yours. I would offer an idea that you consider a flat plate collector system vs. the evacuated tubes. Less to go wrong. Usually, evacuated tube systems are more appropriate when higher temps, > 100 deg. C. for example, are required. Flat plate systems are usually less expensive as well. In general, and without getting into a lot of discussions of an engineering nature, flat plate (non evacuated ) systems are probably more appropriate technology for domestic water heating.

The seller said it was tempered glass tubes with stainless steel serpentine tubes so I assumed it was an evacuated system. It includes a 120 gallon stainless steel tank.
Flat panel systems with a regular 82 gallon tank (non stainless steel) run for the same price.

Thanks for the input!

[J.P.M.]

The seller said it was tempered glass tubes with stainless steel serpentine tubes so I assumed it was an evacuated system. It includes a 120 gallon stainless steel tank.
Flat panel systems with a regular 82 gallon tank (non stainless steel) run for the same price.

Thanks for the input!

You're welcome.

I'm very willing to accept that information on materials is true. I'm also very willing to say: "so what ?".

I'm also of the opinion that evacuated tube systems are, for most applications and particularly in non freezing climates, way more complicated than needed for the simple task of heating water to, say, 60 deg. C.

I also have a hard time buying off on the idea that a simple flat plate batch heater with a smaller tank costs as much as an evacuate tank system. I think that old dog is dancing with your leg.

But, not my money/life/situation and NOMB.

[sanramon]

Hi Papote - I assume you have bought a system by now, and am curious as to which system you went with.
I must disagree with JPM that the unit shown is a batch heater, and that it is too complicated. The mention of it having a stainless steel serpentine says it can deliver hot water via heat exchange in the serpentine for hours at a time.

The evacuated tube type mentioned there does not have heat tubes, nor U-tubes. They are simply known as "water-in-glass" evacuated tubes. No corrosion problems on the copper. No copper to glass joints to fail.

I use a similar system in Costa Rica, where they are quite common. I have never seen a flat plate collector system here in 7 years, but the supplier of my system says they installed 30 evacuated glass units in the past 2 years. I have had no problems with mine in 4 years.
The price you mentioned is exactly equal to the cost of my 20 tube, 200 litre unit, installed - so sounds fair to me.

Hope your choice, whichever type, is saving you money!

[Papote]

Well I ended up paying $150 (USD) more for the old tried and true flat panel system with an 80 gallon tank.
Really happy with it. Always have very hot water at all times. I'd like to find some insulation for the copper tubing from the hot side output, though. Any suggestions?

Save a ton on electricity given that it's over 20 cents a kilowatt and set to rise soon here.

Thanks to all for your valuable input!

[J.P.M.]

I must disagree with JPM that the unit shown is a batch heater, and that it is too complicated.

If the photo is not of a batch heater, what's that big, round, shiny thing above the collector tubes with all the tubing sticking out of it ? Some call that integral collector/storage. I suppose it's somewhat a matter of definition.

In any case, using evac. tubes capable of producing process heat temperatures to meet simple DHW demands in moderate climate or tropical conditions is technological overkill and a waste of resources and money.

Match the tool to the task. For the tropics, get a used water tank, paint it flat black. Put it in a wooden box with glass on two sides - top and one equator facing side, plumb it up and stick a fork in it.

[J.P.M.]

[QUOTE=Papote;n311511 I'd like to find some insulation for the copper tubing from the hot side output, though. Any suggestions? [/QUOTE]

FWIW: There is a product called Armaflex - closed cell foam. It comes in various shapes and forms, including specifically for tubing. I use 1" thickness on my H2O heater lines. Most who use it do the 1/2" thickness. Not a plug, but the stuff seems to perform as claimed by the mfg. and fit for purpose. The stuff is not cheap, so get ready for some sticker shock, but it is, IMO, worth it. If you use it and install it properly, you will not be sorry.
NOTE: If you use it, be sure to wrap it entirely in aluminum tape as sunlight will degrade the Armaflex. Note too: Do NOT use duct tape which will quickly deteriorate. I've had that pipe insulation system for 8 years, it takes very little maint. - ~ < 1hr./yr. to tighten down the tape at a few spots - and is still as fit for purpose as when installed.

[sanramon]

Hi J.P.M.. What is your definition of a batch heater? To me it is a container where the cold water comes in one end, gets heated in a 'batch', and you drain the heated water out of it - presumably while more cold water comes in the other end again. Pretty soon the heated water and the incoming cold water mix and you get tepid water. Right?

That "big round shiny thing" on that system and mine is a heat storage tank. The water circulates through the evacuated glass tubes, heating the tank full of water. Yes, it can heat to 100 deg Celsius, but that is an advantage. One does not use that water directly, as one would in a batch heater.

Through the centre of that heat storage tank runs a coil, called a serpentine by some, of copper or stainless tube - 25, 30 meters or more long. The cold mains water under pressure runs through the serpentine heat exchanger and comes out hot. By having that 200 litres of water at 100 deg C, you can run your cold mains water through that serpentine for hours picking up heat before the 200 litre mass of water cools down to being tepid. So that is not a batch heater, is it? And what is complicated about that?

Do you live in the tropics? Have you seen how mold and mildew can get under glass covers? It is impossible to seal them hermetically - so the mold and mildew will get in, necessitating removal and cleaning of the glass periodically.

And in a tropical developing country, where are you going to get a used water heater tank?

Just my humble, non-threatening opinion and experience.

[AquaticQuests]

I posted a related question on the sticky. Hope some of you could help: https://www.solarpaneltalk.com/forum...ted-tube/page8