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

[LucMan]

Looking at your solar design it seems that you want to connect to your radiators for space heating. How many panels do you have?
If I remember correctly the south of France gets lots of sun in the winter and the temps are mild. If you have at least 128 square ft. of panels the system should work for spacing heating in your climate zone.
Your drawing indicates that the solar panels are connected to the center coil in the storage tank, that is incorrect. The solar panels need to be connected to the lowest coil, the center coil would be connected to your radiators. The radiators should be sized for 110 degrees F for your heat loss and constant circulation should be utilized.
No need to drain your glycol except if it starts to break down from overheating, so make sure solar rated glycol is used it is rated for higher temperatures.
Since you already have all the components have at it, it should be a fun project .
My cousin lives in Avignon.

[J.P.M.]

Given what you describe of your situation and location, for all the complexity and age of the current system, unless you're into solar domestic water heating as a hobby that will turn into a part time job for (re)install/upkeep/maint., I'd think about scrapping the current system for the value of the copper and replacing it with a batch heater - simpler, easier for DIY and so maybe making DIY more appropriate - or a purchased batch system for more money (but still simpler).

Solar water heating is not rocket science. While indirect flat plate systems of the type you describe are workable, in spite of what you may think, they're often more complicated than necessary for the task at hand. They're usually overkill in terms of design that, depending on the application, can easily violate the KISS principle.

lMO, indirect systems like you have are overkill for the task and situation you describe, and unless you know what you're doing, reinstalling it will wind up wasting more energy than it produces.

While not suitable for every application, if you drain a batch heater for times then you're not around like in the winter, it may well be pretty much fit for purpose and mostly maintenance free while being rather easy to construct.

The performance of batch heaters in terms of output m^2 of effective area is similar to more complicated systems for a whole lot less hassle and expense.

Determine your loads, look at a website called builditsolar.com for ideas and scope the net for papers/nomographs/books on solar batch heating. For DIY, I'd look at investigating the type of batch heater that's little more than a 150l to 300l tank painted flat black and placed inside an insulated and foil lined box with a moveable top and front with glazing on the equator facing side and top.

Skill level requires simple carpentry and plumbing skills. Read/learn the info as described above for education as to a few details.

Having designed and built both (and other) types, my educated guess is that for the application your describe, a direct type DIY batch type tank heater will be easier to construct, less costly in terms of toil and treasure and a whole lot easier to maintain than reinstalling an indirect flat plate system.

Welcome to the neighborhood.

[RoyInFrance]

Hello, Newbie here but I have some understanding of Solar PV, Solar hot water and Ground/Air source heat exchange and need advice about re-installing a solar Hot water installation at my holiday home in France (I live in the UK).
When the solar hot water system was removed from my Son's House I retained all the panels , Valves, pump and control unit with the hope of using them, instead of just having them thrown away.(No-one was interested in re-installing the system).
There are no local solar companies in France and all others I have spoken to only wish to sell me new systems and are not interested in advising how I can re-use/re-cycle the existing equipment, so I am looking for someone with knowledge to advise me if what I am planning will work and identify any errors in my plan.
The system was very simple, Glycol in the pipes pass through the black lined solar panels and feed into a coil inside the hot water cylinder. The system was sealed (no header tank) and pressurised with an expansion chamber. There were two temperature sensors and if the temperature in the panels was greater than in the hot water cylinder the pump started and the glycol moved through the system thereby transferring the heat into the hot water cylinder.
My house is in the south of France at 500 metres altitude and is very rural with only wood burning fires for heating. Currently, the hot water is heated by an electric immersion overnight to use cheaper rate electricity. In summer temperatures often reach 30C but in winter can go well below freezing.
We are mostly there in the good weather and rarely during the winter, I would not want to drain and refill the Solar Glycol system each visit so this system needs to be able to cope with both extremes unattended. We may visit more during winter when the Flue boiler and radiator system is added.
Attached is a brief diagram of the planned system.
Thank you