Solar Thermal

[Wendelspanswick]

Anyone fitted solar thermal for water heating?
I've been offered a 10 year old 3m2 panel that's fairly cheap and as I'm going to fit a thermal store in the barn I thought it would be good for heating the water in the summer.
It's a flat panel type but it's just the panel. Would I be better off buying a kit with the controller and valves etc., do they wear out (corrosion/degradation) over time?

 

[julianf]

The panels are only a smallish part of the cost.

You would need a controller, probes & cableing, pump, fancy pipework (im not sure that you can use PEX - most pro installatons use stainless, with flared coupliings), the expansion tank, probably auto air vents at the high points, lead slates, antifreeze etc.etc.

What i mean is, dont just be tempted by some cheap panels, as, if you have to buy the rest at new price, then it will multiply the cost of your used panels.

 

[julianf]

ps. i have some brand new evac tubes here, still boxed... ive had them some time, and still not installed them : (

 

[Wendelspanswick]

Cheers for that, it's what I was beginning to suspect!
Think I'll go for a kit early next year.

 

[armalites]

I fitted two panels to my roof when I redid it. The tubes are not in place as I haven't completed the rest. As already said you need a twin coil tank, pump station,controller,dump radiator. You cannot solder any joints as there is potential for things to get hot enough to melt solder. I used a special flexible stainless steel pipe, it's not cheap but it's pre-insulated and has the sensor cable built in. Save a lot of effort and joints on an install.

I used a place in Upon On Severn who are more than happy to deal direct with the public.

Things I learnt,

You cannot put any tubes in until you have everything commisioned as they generate so much heat.
There is ratio of tubes/hot water cylinder size
You can't have too many.
If you use a blend valve you can run you tank at a higher temperature and hence maximise the value of your water ie 300L at 80c(blended to 60c) is more usable hot water then 300L at 60c. The other benefit doing this is the system is far less likey to be using the dump radiator. I chatted a buy who was on holiday during the summer and his system never got to the point it dumped heat even though they were there.
I spent a bit more and bought an ethernet interface for my controller so I can see what's going on whithout looking at the panel but the place I bought my panels from said keep everything as simple as possible.
You need to think about access and make sure everything is done 100% first time as you don't want to be climbing around on a roof fixing leaks.

 

[julianf]

The bit that's actually stopping me is the pipework. I have all the other kit, inc the lead slates, but the pipework (and flaring tool) costs a fortune.

Im not 100% sure you cant use PEX, but i know no commercial installer would use it.


We have a thermal store in use, with (unused) solar coil. If / when i eventually sort it, it will be nice, as the rayburn does the hot water in the winter in excess, but its a pain lighting it up in the summer.

 

[slim_boy_fat]

These are all over Greece, do they still need the same control functions as mentioned, above for set-ups here?

 

[julianf]

ps. im now wondering if anyone is reading this, and wants to buy some new / boxed (but been here a while - still unopened boxes though) solar panels.... (i have 2 x 20 tube sets - the navitron low profile ones)


: )

 

[julianf]

These are all over Greece, do they still need the same control functions as mentioned, above for set-ups here?

That set up wouldnt work here, as the thermal store is then outside (and not that large)

Also the small volume is fine when your input is there on long hot days, but in the uk, you would want to heat larger volume to even out supply (sunny days) and constant demand.

I suspect H&S would not match to having a cylinder of near boiling water hovering over your patio on some slightly dubious structure. I think that a lot (but not all) thermal stores here are usually of the volume where they are on the ground floor. Sure, a rupture would still be bad, but not as hideous as suddenly getting rained on by (near) boiling water. I guess the volume in the photo is low though - our store is about 300ltrs (and thats not even large)

 

[armalites]

The bit that's actually stopping me is the pipework. I have all the other kit, inc the lead slates, but the pipework (and flaring tool) costs a fortune.

Im not 100% sure you cant use PEX, but i know no commercial installer would use it.


We have a thermal store in use, with (unused) solar coil. If / when i eventually sort it, it will be nice, as the rayburn does the hot water in the winter in excess, but its a pain lighting it up in the summer.

I used Armaflex DUO stainless pipe. It has the flow and return side by side and the sensor wire. I think 10m(so 20m pipe)coil was £195. You don't need a special tool to use it.It's sounds a lot but the difference it makes to speed of install and risk of leaking joints is worth every penny.

 

[MCKDAVID]

@slim_boy_fat

stop kidding on that that's Greece, we all know that was taken at your place...

 

[dazza]

We have a twin coil tank, currently the heat transfer liquid is at 67º with the water in the tank around 60º (350L). There is no boiler connected at the moment don't have any cash so we may have to see if it also works in the winter . We had a power cut when we were away and it lost about 1/4 bar pressure through the valves on the top.

 

[garethp]

You can use standard copper pipe for the pipework but NO soft soldered joints - compression joints are ok.

At 6 bar the boiling point of water is around 150 deg c which is close enough the melting point of soft solder so the joints soften and creep before eventually failing, In normal use on a properly designed system the temperature wont get to 150 deg c but if you get a power cut during full sun the vacuum tubes will get you up there.

I used 10mm copper from a coil with compression joints and armaflex high temperature insulation (normal insulation can melt) and its fine.

 

[nickk]

As a side issue .Also check your roofs in good shape ,you don't want to have to dismantle it all couple of years after install.

 

[Wendelspanswick]

As a side issue .Also check your roofs in good shape ,you don't want to have to dismantle it all couple of years after install.

It's a brand new roof, a new build.

 

[slim_boy_fat]

@slim_boy_fat

stop kidding on that that's Greece, we all know that was taken at your place...

Ah, you know 'sunny Bonar' then.....

 

[mangocrazy]

I did some reading on this a while back, and there are 12v or 24v solar pumps available that operate off a solar panel. This removes the concern about power cuts and stagnation of heating fluid etc. It doesn't protect you in the event of pump failure, of course. It also means that you don't need any fancy programming to stop the pump at sundown or start it up at sunrise. The solar panel does all that for you.

 

[nickk]

It's a brand new roof, a new build.

Perfect opportunity.