Solar thermal which collector technology ?

I have both.

Tech spec of the panel is not as important as the aspect and surface area and ultimately cost imo.

The rrp is rediculous and prevents this basic technology from being common.

Government wasted a huge opportunity not subsidising this over the summer

Good evacuated tubes are pricy it seems + the kingspan model is no longer made which is a shame.

Flat plates coming down in price it seems mainly I guess as it looks like PV so people don't see it as "ugly"

I like the steampunk look of the evacuated tube so doesn't bother me either way.

I need twice as much flat panels to make the same as the evacuated tubes though.

But your right this should be more common than it is.

Any rebates available to make it more affordable? And what's the functional life of either tech?

For PV solar, the big chat is "it costs 16k to install, but you can claim half of it back and it earns the rest back in 8 year", while the rather quieter observation is "and the functional life span is 15 years tops, so you're really not saving much over the life of the kit".

I made my own. I bought the biggest standard Velux window with clear non-filtering double glazing. I made the exchanger out of 18mm copper pipes on a copper backing. I then put lots of insulation behind it, an 27 layer foil thing, 8cm of recycled polyesther and R2.8 polyurethane, and double insulated all the pipe runs. Works great. It's easy to collect solar energy but much harder to not lose it before it gets to the tank IME.

But your right this should be more common than it is.

The problem is that it's a one-trick pony.... It makes hit water and that's it.
If you don't have a tank to store it in then it's not much help.
PV on the other hand will heat water, wash your clothes, charge your car, etc.

the rather quieter observation is “and the functional life span is 15 years tops

And where do you get that garbage information from?

@sharkbait we've heard the pv story on the other thread.

This is about solar thermal. If you know, you know 😂👍

For PV solar, the big chat is “it costs 16k to install, but you can claim half of it back and it earns the rest back in 8 year”

7.5kW cost me about £9k and should pay off in around 5-6 years (or less).

I’m also interested in solar water as I have a heat store (excess PV will get diverted into that too).

This is about solar thermal.

Absolutely. But it was said that it should be more common but there are reasons why it isn't (i.e. storage/combi systems and PV)

I'd have Solar Thermal if I could justify it.

We had evacuated tubes at the old house. They were pretty good, but fragile. I'm not sure how, but we had a couple crack in separate incidents over the 5 years we had the system. I never discovered if the damage was due to errant footballs, or something to do with system design with too hot water in the tank, heated from the woodburner, heating the glycol fluid in the system and then heating cold tubes.

The reason is ROI (cost), lack of. Gov support and gas being so cheap.

Now that gas is increasing, this simple hot water heating should be a good cheap solution.

I'm not saying that it is better than pv, but for me it was a no-brainer as I sourced everything cheap and fitted it myself. ROI = 18mths

I have pv fitted and a battery scheduled to fit next month.

Significant portions of the year I have excess PV but not enough to heat a tank....

I want an closed system that doesn't need external input nor control because I won't always be about to administer - which you handily forget when it comes to making a DIY system. - as well as that not meeting the relevent building standards here in the UK.

I have an area on the roof that's a different plane but still fully south facing where I want to fit solar thermal to heat the water mainly and my solic/excess PV

I want an closed system that doesn’t need external input nor control because I won’t always be about to administer – which you handily forget when it comes to making a DIY system. – as well as that not meeting the relevent building standards here in the UK.

What about the risk of boiling the tank and/or the heating circuit on those scorching Aberdeenshire summer days we get once or twice a decade?

My old system would fire up the radiator circuit once temps reached too high, to dump some of the heat.

What about the risk of boiling the tank and/or the heating circuit on those scorching Aberdeenshire summer days we get once or twice a decade?

I'm not the one at risk. Modern systems are as I describe. And should be due to the governing building standard.

Bleeding pressure out the system manually is not permitted

You cannot have a solar thermal that's uncontrolled, unless you're very brave 😂
Your getting a little muddled because people say they can make their own Panels, which are simple pipework arrangements catching the heat.

The heat loop has an digital differential temp controller and turns a pump on when the panel is hotter than the cylinder. Simple effective stuff that is designed to heat the full cylinder, not just the top to a high temp 😉

I see, by closed you mean all the safety features designed in - not that there aren't any controls to deal with excess heat?

I'm not muddled I under stand what a closed loop control system is.

OTS gets it

You cannot have a solar thermal that’s uncontrolled, unless you’re very brave

Mine is totally uncontrolled except human intervention. It thermo-syphons because the tank is above the panel. With 18mm pipework flow is adequate. If the panel is colder than the tank flow stops so there's no chance of heating the panel.

The human intervention is taking off a section of pipe lagging before going away in Summer so the primary circuit doesn't boil. I've noted some people round here cover their panels for the same reason. No amount of electronics will stop your primary circuit boiling when you don't draw water for a few hot days if your system is well-insulated enough to be worth having in cooler parts of the year. Edit: I suppose you could have a system that dumps hot water to the drain if the tanks gets over 80°C - but what a waste of water.

If you visit Greece and parts of Spain you'll find water tanks with a panel above on roofs with no electronics in sight (They're what inspired my system)

Edit: I suppose you could have a system that dumps hot water to the drain if the tanks gets over 80°C – but what a waste of water.

Not in the UK you can't

But as usual we digress.

Both building standards and my buildings/contents insurance require an approved system. And getting a tank of water above any panel I might fit is a feat of absolute impossibility.

Or an electronically controlled blind or an additional circuit with a heat exchnager to dump heat?

My aim was absolute simplicity, and it just works. Taking off and replacing some lagging over holidays takes a few minutes and is the obvious solution.

No, professionally designed and installed systems don't work like Edukators.

So:

Evacuated tubes = most efficient
Panels = Usually cheaper.

Like I said, whichever is the cheapest.