Solar water heater

[s/v Jedi]

I have not yet read anything about modules to be stuck against the underside of solar panels that circulate coolant in a loop with the heat exchanger of the water heater?

Did anyone experiment with this? Cooling the solar panel should also increase it’s output for the win?

[Franziska]

Following.

Interesting thought.

We wanted to try it with a solar hose coiled flat in a window frame mounted flat on deck.

The idea to put them under the solar panels seems better.

Like catching two flies with one hit :-)

[Captain Bill]

Originally Posted by s/v Jedi

I have not yet read anything about modules to be stuck against the underside of solar panels that circulate coolant in a loop with the heat exchanger of the water heater?

Did anyone experiment with this? Cooling the solar panel should also increase it’s output for the win?

I can't remember where I read this but it was a study that tested this and while it worked to heat the water, the PV efficiency actually went down because the PV part of the panel at a certain point actually got hotter than it would have if it had normal air flow beneath it. Essentially once the water in the tank got hot it continued to increase in temp. on every pass through solar panel eventually exceeding the temp. a normal panel would have in ambient air. If they shut off the flow when the tank got hot enough the collector equipment on the back of the panel would interfere with cooling airflow and the panel would get extremely hot. To make this work well you would have to keep cold water flowing into the panel. Unfortunately in a boat sized water heater tank, you won't have cold water very long.

[Franziska]

Wouldn't a simple temperature controlled valve fix this? If the water is hot enough or to hot for the panels it would stop the circulation, or switch it over to a seawater cooling circuit.
Just thinking aloud, not sure at what temperature there is a kind of break even point reached.
Hot enough for the tank & cold enough for the panels.

Originally Posted by Captain Bill

I can't remember where I read this but it was a study that tested this and while it worked to heat the water, the PV efficiency actually went down because the PV part of the panel at a certain point actually got hotter than it would have if it had normal air flow beneath it. Essentially once the water in the tank got hot it continued to increase in temp. on every pass through solar panel eventually exceeding the temp. a normal panel would have in ambient air. If they shut off the flow when the tank got hot enough the collector equipment on the back of the panel would interfere with cooling airflow and the panel would get extremely hot. To make this work well you would have to keep cold water flowing into the panel. Unfortunately in a boat sized water heater tank, you won't have cold water very long.

[Captain Bill]

Originally Posted by Franziska

Wouldn't a simple temperature controlled valve fix this? If the water is hot enough or to hot for the panels it would stop the circulation, or switch it over to a seawater cooling circuit.
Just thinking aloud, not sure at what temperature there is a kind of break even point reached.
Hot enough for the tank & cold enough for the panels.

I would think that one would end up getting salt water in some parts that were not designed for salt water. I suspect it would make short work of the heat exchanger in the water heater. Having two separate water circuits might work but that's a lot of plumbing. I have personally been looking at a stand alone solar water heater from Heliatos. It's a 2x2 panel with it's own solar panel circulates water/coolant through the heat exchanger in the water heater. I now have so much solar I don't need to run the genset very often at anchor and don't have hot water after a day or two. Fortunately I have nice spot on my hard top to put it.

[PirateGuy]

https://dualsun.com/en/product/hybrid-panel-spring/

Here’s one outfit that makes combo electro/hydronic panels. I’ve seen at least one other in the past.

No affiliation/no experience in these, but also am curious about such a product.

[PirateGuy]

Here’s another one targeting marine applications as a complete kit:
https://www.custommarineproducts.com...for-boats.html

Again, no affiliation, just taking a break from working on my LFP house system

[Captain Bill]

Originally Posted by PirateGuy

Here’s another one targeting marine applications as a complete kit:
https://www.custommarineproducts.com...for-boats.html

Again, no affiliation, just taking a break from working on my LFP house system

Actually this looks like the one that I saw the tests results from or one very similar. I noticed this company is based in Michigan. I guess it might stay cool enough on the water in the great lakes or far enough north that one might not be able to get the water hot enough to make a difference. It would be an issue in the tropics. As for the previous post I noticed that the suggested those units to be used for hydronic heating. When use in that mode most heat is dumped into the heated location and cold or at least cool water is returned to the panel. In water heating in short order the water is hot and hot water is returned to the panel to get even hotter. That is the root of the problem. If one used some sort of heat pump to cool the water in the panel circuit and dump the aquied heat into the water tank then this would work, but my guess is that it would be pretty expensive.

[s/v Jedi]

Originally Posted by Captain Bill

Actually this looks like the one that I saw the tests results from or one very similar. I noticed this company is based in Michigan. I guess it might stay cool enough on the water in the great lakes or far enough north that one might not be able to get the water hot enough to make a difference. It would be an issue in the tropics. As for the previous post I noticed that the suggested those units to be used for hydronic heating. When use in that mode most heat is dumped into the heated location and cold or at least cool water is returned to the panel. In water heating in short order the water is hot and hot water is returned to the panel to get even hotter. That is the root of the problem. If one used some sort of heat pump to cool the water in the panel circuit and dump the aquied heat into the water tank then this would work, but my guess is that it would be pretty expensive.

But you could simply stop circulating the coolant based on temperature of the water. The stagnant coolant under the panel would then transfer heat from the panel to the surrounding air?

[davil]

interesting question
I sail alone so the amount of hot water for one person is small and manage with the solar plastic water bags however I remember visiting Israel in the late '80 and been in awe that al the hot water used by residential was solar heat provided,out of curiosity by your postings google the use of solar water heaters and found that Spain is also a high user as well as Hawaii been encouraged,
not sure how feasible will be to adapt to our solar panels here some links found





Solar Energy Manufacturers in Israel


https://chromagen.com/products/collectors/


Intrigued now,plan to research this topic


thanks for posting

[Captain Bill]

Originally Posted by s/v Jedi

But you could simply stop circulating the coolant based on temperature of the water. The stagnant coolant under the panel would then transfer heat from the panel to the surrounding air?

The problem is that these kits tend to put insulation between the absorber and the air. This results in the coolant getting super hot when it's not circulating. Also nothing is a perfect conductor of heat. The panel gets hotter than the absorber which gets hotter than the coolant and then has to pass thru the insulation to get to the cooling air versus straight from the panel to the air. Eventually it will reach equilibrium but at a much higher panel temperature than if it didn't have the absorber at all.

[RaymondR]

I pondered on doing what you suggest on my previous boat but never got around to trying it. I was going to solder copper tube to thin copper sheet and bond it onto the glass. I changed boats before it worked it's way up the project list so did not get around to it.

Since heat flows from hot to cold the water being circulated will always cool the panels unless you turn the heaters on or run the engine and put heat in via the calorifier.

Since copper has a much higher thermal conductivity than glass and you are increasing the surface area of copper exposed to the atmosphere it appears that the solar heater should keep the panels cooler even if cooler water is not circulating.

19% of all Australian homes have solar hat water systems in Australia. The heater panels consist of black copper panels with water tubes under a glass cover. They also have electric heaters in the hot water storage tanks.

[coopec43]

Originally Posted by davil

interesting question
I sail alone so the amount of hot water for one person is small and manage with the solar plastic water bags however I remember visiting Israel in the late '80 and been in awe that al the hot water used by residential was solar heat provided,out of curiosity by your postings google the use of solar water heaters and found that Spain is also a high user as well as Hawaii been encouraged,
not sure how feasible will be to adapt to our solar panels here some links found

Solar Energy Manufacturers in Israel

https://chromagen.com/products/collectors/

Intrigued now,plan to research this topic

thanks for posting

Solar water heating is very big in Australia.

https://www.solarquotes.com.au/img/p...I_solahart.png

We’ve also installed over one million systems in over 70 countries around the world. We’re at Everest Base Camp and Antarctica. Even Nelson Mandela’s South African home had a Solahart system installed on the roof.


Dealership Opportunities - Solahart

www.solahart.com.au › why-solahart › dealership-oppo...

... Indonesia, Iran (Islamic Republic of), Iraq, Ireland, Israel, Italy, Ivory Coast, Jamaica, Japan, Jordan, Kazakhstan, Kenya, Kiribati, Korea, Democratic People's ...

[coopec43]

I've noticed how hot the water is in the garden hose when I first turn the tap on.

QUESTION

If I have a black hose attached to (say) the stanchions and recirculate water through the hose/storage tank with a very small solar powered pump (2L/min) how hot would the water get?

[coopec43]

Originally Posted by shannonvue

i need about solar water heater how to work?

https://www.youtube.com/watch?v=xbDWrC9YyH0