Help and advice please on re-use of solar hot water panels

[RoyInFrance]

OK. Thanks for all the information, Now I need to do calculations e.g. how much electricity am I using each night to power my immersion heater vs how much to run AC pumps to use solar, how much to invest in PV solar to power pumps etc AND to find UK or French suppliers.

All this then I can calculate the investment and pay back time. Not much point in doing all this work if it will take years to get the cost of investment back.

Lastly, Where can I find instructions on how to use the flow meter Panel and Flow Meter.pdf

[LucMan]

Try this, all of the different type systems illustrated here for your info.

https://www.aetsolar.com/cfiles/dfiles/literature_docs/catalogs/CatalogAugust2015Optimized.pdf

https://www.aetsolar.com/literature-download

If you have a flow meter use it, it's not required but could help tp make fine adjustments to flow rate.
Happy reading

[RoyInFrance]

1- You can run off 12v PV with a solar panel and 12v dc pump = no control when the sun hits the panel the pump will start to run slowly reaching full speed when full sun hits the panel. This usually works for 1 small 32sq.ft serpentine panel or evacuated tube system. If you have flat plate standard header and tube panel or multiple panels it would be hard to find a dc pump to give you sufficient g.p.m flow rate to make this work.

2- This in my opinion is the most desirable option. If power is lost the panels may stagnate but that should not be a problem if the expansion tank is sized properly. The controller will just resume when the power comes back on, no reset required.
Or convert to a drain back system. This is the only type system that I install because of it's simplicity, no glycol, no expansion tank. Search for solar drain back system .

3- See #1

I have 4 usable water panels approx 53" x 33" (one I suspect was damaged .) All with 15mm pipework so probably 48 Sq ft Panel and Flow Meter.pdf
I have found DC pumps and panels but all are submersible pumps (3.2 GPM and 230 ft lift) - good for drainback systems but no good for closed loop glycol.

I have started to read up on drainback systems, with solutions from simple to very complex How could I transfer the heat from the drainback system to the hot water tank? can you point me towards a simple design..

Also Is the flow meter of use to me in either setup?

Thanks.
P.S. please advise if I am asking too many questions

[J.P.M.]

Because I already have most of the equipment panels, pressure gauges, expansion vessels, etc. I even have a couple of 220V pumps .
I only need to buy a new hot water tank and pipework, which would be needed whatever method I choose.
Possibly a solar hot water differential controller which I am discussing with LucMan
Here there are 3 choices
1. If I can keep it all 12V DC I need a PV solar panel, with pump and controller (Independent of mains interruptions)
2. Run it all off mains, use the pump I have and only need the Controller, (could there be problems when no mains?)
3. Just PV panel and pump and it runs when the sun shines. (would there be enough sun to run the pump but not heat the water?)

Which of these is the better option OR not possible OR to be avoided I need the advice from experienced people such as yourselves

P.S. I will however be looking at the bread box heater as a method to warm our above ground pool but that is another project for another time.

Thanks to you both for your advice and comments.

You're most welcome. As for pool heating, don't use a batch heater. Doing so is is an ineffective use of the technology.
The most technologically appropriate way to heat most any reasonably sized swimming pool in a mild, sunny climate is to use an effective pool cover. For added heat if the pool cover doesn't keep the water adequately warm, use flat plate pool heaters made for the purpose for the final boost, but start with an effective pool cover.

[LucMan]

1. If I can keep it all 12V DC I need a PV solar panel, with pump and controller (Independent of mains interruptions)
2. Run it all off mains, use the pump I have and only need the Controller, (could there be problems when no mains?)
3. Just PV panel and pump and it runs when the sun shines. (would there be enough sun to run the pump but not heat the water?)

Which of these is the better option OR not possible OR to be avoided I need the advice from experienced people such as yourselves

P.S. I will however be looking at the bread box heater as a method to warm our above ground pool but that is another project for another time.

Thanks to you both for your advice and comments.

1- You can run off 12v PV with a solar panel and 12v dc pump = no control when the sun hits the panel the pump will start to run slowly reaching full speed when full sun hits the panel. This usually works for 1 small 32sq.ft serpentine panel or evacuated tube system. If you have flat plate standard header and tube panel or multiple panels it would be hard to find a dc pump to give you sufficient g.p.m flow rate to make this work.

2- This in my opinion is the most desirable option. If power is lost the panels may stagnate but that should not be a problem if the expansion tank is sized properly. The controller will just resume when the power comes back on, no reset required.
Or convert to a drain back system. This is the only type system that I install because of it's simplicity, no glycol, no expansion tank. Search for solar drain back system .

3- See #1

[RoyInFrance]

From what you've described of your situation and goals so far, you're going to be better off with some form of passive solar water heating system of which bread box heaters are one type.

Why all the complication ?

Because I already have most of the equipment panels, pressure gauges, expansion vessels, etc. I even have a couple of 220V pumps .
I only need to buy a new hot water tank and pipework, which would be needed whatever method I choose.
Possibly a solar hot water differential controller which I am discussing with LucMan
Here there are 3 choices
1. If I can keep it all 12V DC I need a PV solar panel, with pump and controller (Independent of mains interruptions)
2. Run it all off mains, use the pump I have and only need the Controller, (could there be problems when no mains?)
3. Just PV panel and pump and it runs when the sun shines. (would there be enough sun to run the pump but not heat the water?)

Which of these is the better option OR not possible OR to be avoided I need the advice from experienced people such as yourselves

P.S. I will however be looking at the bread box heater as a method to warm our above ground pool but that is another project for another time.

Thanks to you both for your advice and comments.

[J.P.M.]

Apologies Lucman, I did not mean to question the advice. I am trying to keep this solar installation off grid i.e. not connected to mains as there is often interruption to mains power.
If no one is at the property when the mains comes back on the circuit breaker has already been tripped so the power does not return.
I understand that a solar PV panel generates DC which can be converted to AC but this is an additional expense and complication for the DC-AC converter.
Can I just use the DC power directly, or am I being too simplistic?

Perhaps I am solving a problem of over heating, which may not occur.
When no one is at the property I do not need the hot water heated, but does the system NEED to circulate?
During these unattended period If there is high solar activity I am concerned that there is a danger of the glycol in the panels overheating causing damage to the system if it is not circulated removing the heat, Do I need the glycol to circulate whenever the panels get hot?

Thanks again

From what you've described of your situation and goals so far, you're going to be better off with some form of passive solar water heating system of which bread box heaters are one type.

Why all the complication ?

[RoyInFrance]

As I stated in a previous reply use a line voltage controller and pump, in France that would be 220v 50hz.

Apologies Lucman, I did not mean to question the advice. I am trying to keep this solar installation off grid i.e. not connected to mains as there is often interruption to mains power.
If no one is at the property when the mains comes back on the circuit breaker has already been tripped so the power does not return.
I understand that a solar PV panel generates DC which can be converted to AC but this is an additional expense and complication for the DC-AC converter.
Can I just use the DC power directly, or am I being too simplistic?

Perhaps I am solving a problem of over heating, which may not occur.
When no one is at the property I do not need the hot water heated, but does the system NEED to circulate?
During these unattended period If there is high solar activity I am concerned that there is a danger of the glycol in the panels overheating causing damage to the system if it is not circulated removing the heat, Do I need the glycol to circulate whenever the panels get hot?

Thanks again

[LucMan]

As I stated in a previous reply use a line voltage controller and pump, in France that would be 220v 50hz.

[RoyInFrance]

I can't help you with that , do a search for 220v solar hot water differential controller (Caleffi, Resol), & solar thermal pump. ( Grundfoss or Wilo)

220V ? Surely you mean 12V or am I being stupid. Thanks

[LucMan]

I can't help you with that , do a search for 220v solar hot water differential controller (Caleffi, Resol), & solar thermal pump. ( Grundfoss or Wilo)

[RoyInFrance]

Use a differential controller for the solar pump using line voltage. The differential controller will keep the pump off unless the panels are 10-15 degrees F warmer than the stored hot water, eliminating the possibility of the the pump cooling the storage tank.
Do not use PEX on this system use only copper or corrugated stainless steel. There is a high possibility of reaching stagnation temps and bursting the PEX at high temps with a pressurized system. Some PEX is acceptable if you convert to a drain back system but that would require a knowledgeable solar installer.

Any advice on where to get the differential controller, possibly with pump and solar panel to drive both.

[LucMan]

Use a differential controller for the solar pump using line voltage. The differential controller will keep the pump off unless the panels are 10-15 degrees F warmer than the stored hot water, eliminating the possibility of the the pump cooling the storage tank.
Do not use PEX on this system use only copper or corrugated stainless steel. There is a high possibility of reaching stagnation temps and bursting the PEX at high temps with a pressurized system. Some PEX is acceptable if you convert to a drain back system but that would require a knowledgeable solar installer.

[J.P.M.]

Thanks for the replies'
J.P.M. First I know nothing about batch heaters but will research those. The copper pipes in the panels does not have much scrap value (all the pipework that used to link everything together has been scrapped) So really the whole project was about recycling instead of throwing away/scrap, but I will look at batch heating if it is low cost.

.LucMan,
The solar system is intended to only heat the hot water, not the radiators and would be mostly effective in the summer when no additional heating is needed in the house, but hot water is. The radiator system would only be in effect in cold weather when the wood burner was working using "wasted" heat in the flue. The wood flue boiler would also heat the hot water on these cold days.
It is a greater concern that on cold days with a little sunshine the pump would remove heat from the hot water cylinder into the panels, but I am not sure if this is a real risk. If it is possible to also have the DC pump controlled by sensors that only allow the glycol to circulate when panels are hotter than cylinder I would like that (but I need the whole solar system to work off mains)
Thanks for the nod about solar rated glycol.
The whole radiator system I will design with the plumber, specifying the flue boiler for the appropriate BTU for hot water and radiators. this is not a problem as he has done this before. It is all the solar stuff that he has no knowledge of.

A question still remains. The radiator system will mostly (not directly next to the flue boiler) use PB or PEX pipe (like Hep2O) . Can I use the same for the glycol filled solar system?

Understood.

If you're into DIY/recycling, and as for simplicity for batch type heaters, for mostly non freezing climates, what's often called a breadbox water heater is about as simple as it gets.

Think of constructing an insulated, foil lined box maybe 1m X 1m X 2m (or whatever size you choose, depending on the chosen tank size).

Hinge 2 adjacent long sides of the box and put the hinges on opposite long edges.

Place the box horizontally on its long side with the long axis parallel to the equator so that the top long side and equator facing long side can be opened and act as reflectors (using the insulation foil as reflectors).

Place a (recycled (?) but pressure tested) domestic water tank that's been stripped of its insulation and painted with flat black paint inside the box. Put the outlet connection at a higher elevation than the inlet and plumb through the east and west ends of the box.

Glaze 2 adjacent long sides of the box (the equator facing and top sides) and hinge the wood on those sides so they can be opened during the day to collect more sun.

Keep the lines short and insulated, put a check valve on the inlet and see builditsolar.com for lots of other details, alternate designs and ideas. Just take some of the advice with a grain of caution. There's a lot of good info that the site contains but there's also a lot of redneck engineering that goes on and it's not too well vetted.

I've built a couple of these things and for a mostly non freezing climate they're about as easy to make and about as trouble free as it gets which is probably helpful for the semi isolated situation you seem to be describing. The performance can be surprisingly comparable to closed loop, indirect flat plate systems which are much more complicated, particularly if you're big on reusing materials and using appropriate technology of the kind that (analogously) doesn't use a howitzer to kill flies.

Heating water is a "dumb" application. For a lot of reasons, it doesn't need to be complicated.

[RoyInFrance]

Thanks for the replies'
J.P.M. First I know nothing about batch heaters but will research those. The copper pipes in the panels does not have much scrap value (all the pipework that used to link everything together has been scrapped) So really the whole project was about recycling instead of throwing away/scrap, but I will look at batch heating if it is low cost.

.LucMan,
The solar system is intended to only heat the hot water, not the radiators and would be mostly effective in the summer when no additional heating is needed in the house, but hot water is. The radiator system would only be in effect in cold weather when the wood burner was working using "wasted" heat in the flue. The wood flue boiler would also heat the hot water on these cold days.
It is a greater concern that on cold days with a little sunshine the pump would remove heat from the hot water cylinder into the panels, but I am not sure if this is a real risk. If it is possible to also have the DC pump controlled by sensors that only allow the glycol to circulate when panels are hotter than cylinder I would like that (but I need the whole solar system to work off mains)
Thanks for the nod about solar rated glycol.
The whole radiator system I will design with the plumber, specifying the flue boiler for the appropriate BTU for hot water and radiators. this is not a problem as he has done this before. It is all the solar stuff that he has no knowledge of.

A question still remains. The radiator system will mostly (not directly next to the flue boiler) use PB or PEX pipe (like Hep2O) . Can I use the same for the glycol filled solar system?