Solar tubes best as I mainly want hot water?

_BAA_RAM_EWE

Im not a heavy elec user.

I just want hot water the easiest way possible.

Is their many installers? Is it difficult to install? How much to maintain?

steinbock123

sorry , wrono thread

PV is still a better option even if you only install the panels and a basic inverter and dedicated immersion heater.

The install and price of materials for a solar thermal system just don't make sense any longer.

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.

I think you will even struggle to find an installer at this stage for all these reasons.

bullit_dodger

https://www.boards.ie/discussion/comment/122013100#Comment_122013100

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.

unkel

https://www.boards.ie/discussion/comment/122019971#Comment_122019971

All he said is true. And that's from someone like me who is somewhat a fan of solar thermal still. Presuming what he means with cut in point is that on a bright but not very sunny day in winter, the delta between collector temp and bottom of cylinder temp is not enough to make the coolant flow in a solar thermal system. So zero output. Yet you could get quite a decent output with a solar PV system

usernamecharlie

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

con747

https://www.boards.ie/discussion/comment/122036564#Comment_122036564

Post in the For sale thread for more people to see it.

https://www.boards.ie/discussion/2058260098/renewable-stuff-for-sale-and-wanted

usernamecharlie

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

Grumpypants

I've the tubes and (when the probe on the roof hasn't been pulled out by crows 😂) it works pretty well. In Winter it doesn't do much, odd sunny blue sky day cold top you up from the 10 it comes in at to 16-22 degrees.

When we get a fine Sunny spell in the summer months I've seen it heat up to over 50 degrees fairly handy. But for most of the summer it's in the 30-40 range. Fine for me as I take cold showers but the missus still boosts it to a temp that strips the skin off.

They were here when I bought the house but if I had my choice I'd have PV. My neighbours got fine big pv systems giving them power all winter while my tubes are doing very little.

dumb_parade

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.

slave1

PV can earn you money too, tubes can't

concubar

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.

unkel

https://www.boards.ie/discussion/comment/122040936#Comment_122040936

Wouldn't call flat panels "superior technology". It's nicer looking and more robust. But less efficient. And more expensive. I think the sales person did a good job on you though 😁

graememk

https://www.boards.ie/discussion/comment/122040936#Comment_122040936

It's a heatpump at heart. Takes more electric to run than traditional tubes but works well in all weathers.

dathi

https://www.boards.ie/discussion/comment/122041033#Comment_122041033

its a heatpump at heart but with a built in emersion that the owner has no control over that turns on when the system cannot provide hot water fast enough with the panel

_ptashek_

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:

unkel

https://www.boards.ie/discussion/comment/122041939#Comment_122041939

Probably poor quality tubes / pump. Not a good install. I'll hazard a guess that it is not a Kingspan system?

Also solar thermal works on heat, the name says it. Even at 10AM on a very sunny day like today, it was only 6-7C. That doesn't do much. Whereas PV works better, the colder it is

_ptashek_

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.

unkel

And don't underestimate the maintenance. Even on a system that never gets hot by design, like the Kingspan Thermomax, you will need to change coolant every 5-10 years. Which if you can't do it yourself, will likely set you back €250 or so (I would be delighted if someone could point me to someone who does it cheaper), which is a significant part of a year's savings gone.

And then there is possible leaks…

bullit_dodger

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.

_ptashek_

Since today is an exceptionally sunny day here, I'm sure anyone with PV on the roof is a happy camper. But the solar thermal is doing its job too. Wouldn't entirely discount it as an option.

Some more data from my system, also showing how ambient temp has no impact, and even changing cloud cover isn't that huge of a factor.

Haven't yet crunched the numbers for the tubes, but the flat plates were saving on average €600/year in gas bills. Maintenance over 10 years came to €350 total. Cost of running the pump was minute.

bullit_dodger

https://www.boards.ie/discussion/comment/122042787#Comment_122042787

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.

Jonathan

Good day for the solar thermal indeed.

https://www.boards.ie/discussion/comment/122042787#Comment_122042787

How are you pulling the data from the Resol to Home Assistant? Are you using the vBus LAN adapter? Or did you build a converter circuit to convert the vBus to regular serial for a RPi/ESP?

_ptashek_

https://www.boards.ie/discussion/comment/122043130#Comment_122043130

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

Jonathan

https://www.boards.ie/discussion/comment/122043462#Comment_122043462

Nicely done. My setup is documented here.

slave1

Panels will do all the water you want April to Sept, a good bit in March/October and little to nothing Nov-Feb. Those panels will then export to pay for immersion usage and require zero maintenance

Big Lar

Can go wrong with one of these babies, just divert the feed into the cylinder through this and volaa!

Have it in nearly 9 years now I think and its the biz summer and winter, summer the water is close to boiling and winter it heats the water from the tank in the attic (5Deg) passing through to the cylinder to to around 20-30Deg. Course in the really dark foggy days it does noting but that's fine too as it takes no energy to run.

bullit_dodger

https://www.boards.ie/discussion/comment/122047215#Comment_122047215

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.

_BAA_RAM_EWE

https://www.boards.ie/discussion/comment/122047215#Comment_122047215

solar tubes on the ground is it?

unkel

https://www.boards.ie/discussion/comment/122046367#Comment_122046367

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

unkel

https://www.boards.ie/discussion/comment/122047215#Comment_122047215

Millions of houses around the Mediterranean have that setup. Cheap and cheerful, no need for any electrics / controllers / pumps.

dathi

https://www.boards.ie/discussion/comment/122041939#Comment_122041939

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

unkel

https://www.boards.ie/discussion/comment/122048307#Comment_122048307

Similar setup here. 40 tubes with 360l cylinder. On a day like yesterday it can easily heat all of that water from say 12C to my max of 63C. That would take 22kWh. Solar PV panels of the same size (m2) wouldn't even produce a third of that.

Efficiency of the tubes is about 70%. PV panels are about 20%. If you use lots of hot water and your roof space is limited, there is still a case to be made for solar thermal if you get the job done for a reasonable price (or DIY)

Big Lar

https://www.boards.ie/discussion/comment/122047362#Comment_122047362

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

DC999

https://www.boards.ie/discussion/comment/122050976#Comment_122050976

No way, it's that simple? Just the hot into tank and cold to replenish it? No pumps needed due to the hot water rising?

slave1

similar to a Willis external immersion, no pump just a "natural" syphon action that pulls cold water and pushes out hot

loyatemu

https://www.boards.ie/discussion/comment/122050976#Comment_122050976

is there not a risk it will freeze in winter?

Big Lar

@DC999 That simple

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

_ptashek_

https://www.boards.ie/discussion/comment/122048307#Comment_122048307

Of course, you're right. But my problem is not so much with the loss of collector area, but the overall performance of the tubes in my specific setup. Need someone who knows what they're doing have a look at the tube-to-manifold part.