Solar tubes best as I mainly want hot water?

sorry , wrono thread

Cut in point for PV is also much lower so you get more output in the winter. You can also easily expand your installed capacity without a major remodel of the system.

Not sure that's 100% true. Per square meter solar tubes capture more of the suns energy than PV and they do pretty well on cloudy days too.

That said, I'd be of the same opinion as you. Solar PV is just the way to go. It's far easier to have solar PV with simple wires than it is to be plumbing pipes, have gycol maintenance, pumps, etc. Depends on how much water you use, but 4 panels or so (1.2Kwp) would see you right for most days of the year.

Note: In winter you won't get much hot water from Solar (PV or thermal), but for 7-8 months of the year either will do well.

Hi,

I am switching to PV panels and will be removing my Joule solar tubes , new pump etc. Hot water from March until October, if you are interested let me know. PV are are a better option for me because of roof space.

Cheers

Stephen

Thanks, good idea! I'm new to boards so will have to find a good solar forum.....and nut out who is a good supplier.…thanks again for your reply ☺️ I'd be happy if the found a new home

I have both pv and tubes on my roof also, the tubes need to be serviced and that’s adds to the cost of ownership. I would consider them old tech at this stage but the pv system I have about 18 months now, is a much more general purpose solution.

I have thermodynamic flat panel for hot water, LVP fitted it…

I think it is far superior technology to the older tube system,

(think my ber cert guy said it was over 300% efficient,

Gives a full tank 280L all year round…..

Solar Pv being fitted next month, should be fairly sorted then.

Long term solar collector user here. South facing aspect.

I had 7m² of flat plate collectors on my roof for 10 years, and with the exception of November to February, the 204 litre buffer tank never needed a top up and had enough hot water for a family of four.

Fast forward to now, because of changes in roof structure I had to switch to solar tubes on a custom frame. Same location as old panels, just off-roof. Have 30 of them, and - in direct comparison - they're junk.

Barely ever get above 35°C on a clear sunny day. The flat plates were easily getting to >70°C, sometimes even going into thermal shutdown...

Here's a sample from this morning:

Solar thermal works (mostly) on infrared radiation, not direct/ambient heat.

The panel/tube may take a tiny bit longer to heat up on a cold day, but that's it. They can perform well even below zero, as I've seen many a time with my flat plates in winter.

Solar thermal works a lot better on a clear day, as more infrared hits the panel/tube directly. But tubes are also supposed to do better on cloudy days, as they're - so the theory - better at collecting scattered infrared.

My system is Joule tubes and a Resol, tube specific, controller with a Dunfoss PWM controlled pump and fully insulated pipes from solar to store. That's what was available.

But I do suspect that the tube to manifold thermal interface wasn't prepped properly on install, which shows another downside of tube collectors - they're a fuss to install well.

Yeah - it's hard to see beyond the advantages of solar PV. That's not to say that people haven't had successful solar thermal installs. 10 years ago, with the price of solar (pv) panels back then, really thermal was the only game in town if you wanted a resonable return on investment, and for many they've done well. But they are a bit like heat pumps today. Well proven technology, works a treat, but if you don't get a good installation, or it's not exactly a proper fit for your house……nahh move on Roy.

Nowadays with the prices of panels the way they are, it's just simplier/cheaper/less maintenance to go that route. I mean look at these….

https://midsummer.ie/buy/Clearance/REC365TP4BLK

Just over €50 for a panel. That's crazy cheap. Get 10 of those puppies, few microinverters and your hot water is sorted for (being generous) €2k? If you can get a solar thermal installed for that price……I'd be interested myself.

ohh 100% ptashek. 100% agree. Like unkel above, I wouldn't be slagging or disparaging solar thermal as a way to heat water. To me, any technology which captures energy from the wind, sun, etc and does something useful with it, well that's good for the environment and good for your pocket (mostly).

The problem here is more one of installation cost. If you have a working solar thermal unit, I'd be slow to get rid of it. If your starting from scratch, with the collapse in price of PV panels over the last 10 years and estimates that they have come down by 90% (no that's not an error!), it's hard to see thermal being a viable option now.

I've 6 panels on my shed. Cost me about €2500 when I put them in 2 years ago. It'd probably cost me €1800 now.

Days not over yet and already they've generated 10-11Kwh. My immersion is hot since 1pm (it took 4.5kwh) and I've exported 6-7 kwh at €0.24 from those panels. Granted not every day is like today, but the 2nd disadvantage of the thermal is once the water is hot, that's it done for the day in capturing energy…..while the pv panels are more flexible as you can cook dinner, watch telly, export it, etc.

Made my own VBus adapter and wrote the software for it, running on an Arduino RP2040. Data is reported via MQTT.

I like those ones Lar. You see them a lot on the continent. Odd that they never took off in Ireland the same way 10-15 years ago.

If you have a smart meter, using PV panels to heat your water is extremely expensive at about 20-25c / kWh as you could export instead and get FIT. More than twice as expensive as using an efficient gas boiler

you have gone from 7m2 of collectors down to 2.8 m2 of tubes so less than half the collector size so the extra efficiency rate of the tubes doesnt make up for loss of area having said that i have 30 tubes into 200 litre cylinder and with the good weather currently heating water to 67* which is what i have the temp max set at

Yup, this is the jist of what I have done, probably other ways of doing it also.

@DC999 That simple

@loyatemu The tank itself is lagged and I have all pipework lagged also. Hasn't frozen yet anyways.