Solar thermal for water heating

grudi79

Hi all, i know i can probably find all info in the forum but it might take long before i'll understand everything.

Just got my first gas bill after all price rise and started to thinking about getting tubes on my roof for water heating.

i don't really have much space to think about solar panels so only tubes, or thermal solar, not sure how they called properly.

I have to say that i know nothing about it so any chance if You could explain what needs to be done from A-Z?

Just to add that we have gas heating and we also use gas to heat water, not sure if makes any sense to use immersion as it's really old.

New gas boiler fitted three years ago. It's three bedroom end of terrace house with two, some days three people in it, 106m2.

It's timber framed house.

I don't think there is any other option to heat it so only asking about water.

thanks in advance for any suggestions!!!! :)

micks_address

people seem to be leaning towards pv panels rather than tubes.. ive no explanation why.. you can use a hot water divertor from solar pv to hear your water.. again not sure if thats more efficient than tubes.. but i suppose with tubes you can only use for water wheras with panels you can choose where you use the electricity. do you know which way your roof is faced? east/west/south etc..

greasepalm

I have had solar panels from Active 8 for well over a decade and in Summer are great for heating water when very sunny.

Winter is different with a low lying sun as it does not charge outside solar lights due to its angle .

Solar panels are not great as maybe to old and not heating emersion enough.

Yes i zap the element to boost the heat for the rain shower even if the gas is on.

I have a tap on side of tank than controls the flow of heat from gas boiler to hot press and if fully closed will heat rads only .

Opening the tap allows water into hot press and heat water in there , the more flow in there reduces heat from rads.

I remember at The Ideal Homes show and seen something like this that works night and day so can work even in the night.

https://www.lvprenewables.ie/thermodynamic-solar-panels/?gclid=CjwKCAiAheacBhB8EiwAItVO25tWVxKJnQ_M1tCRQes9fgGe4sjow7pO4IT4CczcORDAnr6875Jy5xoCWQ8QAvD_BwE

unkel

@greasepalm - "I have had solar panels from Active 8 for well over a decade"

Nice one. With the price Active8 charged you, they will be paid off in another 6 or 7 decades 😉

@micks_address - "people seem to be leaning towards pv panels rather than tubes.. ive no explanation why"

Because they are far more efficient. PV panel about 20%, solar thermal about 70-80%. And until a few years ago you got no subsidy for panels and a large subsidy for thermal and panels used to be a lot more expensive.

These days, if you have plenty of space, go for PV. But in case of the OP, with very little roof space and maybe a large use of hot water, thermal might work better. Although I would be inclined to just go PV myself, even with very little roof space.

graememk

https://www.boards.ie/discussion/comment/119995383#Comment_119995383

Generally pv is a lot simpler. And generally more useful, as it cuts your electric bill.

Tubes are much more efficient space wise but unless you have a lot of them, your still only going to be heating your domestic hot water, not your house.

Also the install usually requires a new cylinder too to store the hot water.

https://www.boards.ie/discussion/comment/119995469#Comment_119995469

They are basically heat pumps at heart. V good for heating water.

greasepalm

https://www.boards.ie/discussion/comment/119995907#Comment_119995907

Yes very tall insulated cylinder i received

bullit_dodger

https://www.boards.ie/discussion/comment/119995383#Comment_119995383

Just to echo what the lads have said above. it's not so much that tubes are "better" or "worse" than panels, but more that the price of solar panels has dropped (about 90% in the last decade!) meaning that previously 10 years ago or so your 5Kwp system would probably have cost north of €25k! Nowadays it's more more economical to just go the PV route.

If your stuck on space and have huge hot water requirements like some people on the forums, the tubes give you the most hot water for roof space. But for most people the PV with a Eddi can do a good enough job for 1/2 the cost. Hot water tubes requires pipes, pumps, some minor maintenance every couple of years for the gycol (?). PV on the other hand can sit there for 15-20 years.

You can't power your fridge or xBox from hot water either, so I guess PV is more flexible - but yeah, there definitely are guys on this forum who have gotten good use of tubes, but it's hard to beat PV

Big Lar

Possible solution,

I have a thermosyphon installed with almost 9 years now, it takes the cold feed from the tank in the attic and feeds into the bottom of the cylinder, this time of year the water in the tank in the attic is around 4 Deg and just checked the water coming out of it at 22 Deg. So instead of the oil boiler heating water from 4 deg to 60 deg it now starts at 22 deg. In the summer time the water is about 80-90 Deg and if were pointed directly south the water would boil

About 6-7 years ago I had a load of sensors connected to it and a flow meter, using an Arduino all the data was sent to Thingspeak and I was able to calculate the savings to be about €100 a year on oil and considering it cost me €450 at the time to buy it and another €100 in fittings as I installed it myself it there was no install cost - Very worthwhile project.

bullit_dodger

https://www.boards.ie/discussion/comment/119996451#Comment_119996451

I like that a lot.

DC999

https://www.boards.ie/discussion/comment/119996451#Comment_119996451

Class, I didn't think it would get to 20C+ in this weather. Paid for itself many times over already!!

unkel

https://www.boards.ie/discussion/comment/119996893#Comment_119996893

It has brought in scorching hot water into my cylinder from when it was very cold outside in mid winter in my place. Obviously on a very sunny day

unkel

And @Big Lar doesn't mention it specifically, but a Mediterranean style system like he has when the whole system is placed above the hot water cylinder in the house, heats the water by natural convection - it works like magic, completely by itself. No pump needed.

DC999

https://www.boards.ie/discussion/comment/119996990#Comment_119996990

I was about to ask the Q as to why his had a tank. Clever setup. I've seen those in likes of Portugal but never here.

grudi79

https://www.boards.ie/discussion/comment/119995383#Comment_119995383

My roof is faced S/S-E but not much space on it anyway as You can see on screen shot below, i was only thinking about blue aera.

There is a bit above master bedroom which i wouldn't have much use from, not sure does it make any sense to think about other side facing north.

And that's a reason i only asked about tubes for water heating. With only gas heating i don't have many options there, we don't even have proper chimney where i could put proper stove.

Was just reading about hybrid heat pump where i could still use a gas if really cold but most of the time it work for itself but not easy to get in touch with any instalers, i think they are all so busy that i'll just wait and see next gas bill and will keep thinking about proper solution and hopefully i'll have something done before next winter ;)

Thank Guys for any reply!!!

grudi79

@greasepalm that thermodynamic stuff looks cool, do You know anybody who use that? wondering if it's expensive

greasepalm

https://www.boards.ie/discussion/comment/119998040#Comment_119998040

No afraid not but i thought i saw something on Facebook and sensor and house out west and they can check on temperatures logged 24/7 which was great

https://www.facebook.com/stoves4u.ie/photos/basw.Abp_xh_7yPmBD59o7__8ojZ59bw8_2yVt23RGPRQ4hlnxIqllyy_DtpKh6wynQcsxgTMtA36B_NU40Viu20c-660qjmFc_uIuTGZJu1wHNj05kTQsuMMJhWpK04qBEn-BShe99RWT29wwGGKoSvBWLCFUrCc1ilmAbVFbW-TnbLD-A/1812083665798692/?opaqueCursor=AbriSeEH_gtBiuyolFj73yXxS6iMF15wJvoUdDGtkGoXlepHWX4vkkWqyEWcl8HcnbZja36FeqIiwVbX5jZjT0Sk-C3nos5DzVKqKfJLq_tb-WGzwVF0_VFrYIXGYqvEoiqvXgW4DD-dOzQB8v82dIiu00VnzI33ywKXFhlhTK9N0RUv6o78xKjEZW2RwKsMHehLIo41GLXFoeSzT-lw4VuzDCgo_VfWXXNVOsHwB0ueZ8Hmm_Wjg3JkuqVAyx81hIyrg4769tIRjZdptW1mP7Db2TZDXDpUWhpUYDTEFRDtACwnZEryzUTRBIXRWLmcTLPB4SMBLOsQGpO1EJcncWOgikF582h6ijdT2KmuodUu4_vasui-VyiK_pHlGoBnoBZ6oV6ddjBsDmCNHV5jP5Mai-kFj3b-jAJDHoleKkIwYeOPea5dOFYeFqC88DgE4A5_4Iq5mE6QH50jeIlSSXnwMrmwCtLuN0JxSjIFk8J5g1CY-5OY-v-pl96SjrpSB1kxJdx8TclAvrTv6o7NyEA0UFkBbaBbDUI37tFeKZoavN8PAjdOlVwMCszp0lXX1fbSinBd9DMXs0oMwAbIMEOq8q2sOCq29Mq8hCBxmsNY1BqGqZDw4nYVBxke1QSuxUQPKJLs0ByrWakbhvGTzSTAAw7Ky5Z7hFT3lxdHtZlpfTHmvFfRcr8dq1fjytTU2CN2OAv7FWY5WDUu89x5rx1kGnfQ1KoS_XezIKBO21j9UdB5L3B6V71gOK3-d4e9_4ze9f20acEdSWYrvzOyTLxTDB6hR-UbtUNkg_g4dlD0if5TaWe2nYktpagTKPd9kFHtg6tmDlslyFJKPftNz--4z4HBMpwjGi8azbVKRL7p84MFNtLHnpM_wA6zkUnjomQ7duzTX6SZF6g-jnAa_1txTEtzPcv71iKB-WHe0bHQe9JeT8j0-nmn0mzalgDfRByHZW_ye_G6jG7pGjCUVEPi6YQrForyIqt6_r8Nc1ranmB7c9rRbtnnFKkdkWyCDC8

redmagic68

Tubes can be wall mounted with pipe work going through the gable wall to your tank through the attic. You may need a new tank depending on your current situation. A coil for tubes, one for immersion and one for gas if this feeds to the tank also.

I have Kingspan tubes in 11 years now. They supply nearly all the hot water for 8 months of the year and today take the hot water in the tank to 22C. Meaning your only using your heating source to add another 30 degrees. We didn’t have a lot of sun here today in the morning which is the best time for our tubes.

I don’t have knowledge on current costings so can’t argue to which system is most cost effective and there would be a cost for re plumbing etc but you can put the tubes on the wall and panels on your roof if you so choose. Mine are on an east facing roof which isn’t ideal a south facing wall would be much better year round but they have paid for themselves many times over and are still working just as efficiently. If you do decide to go the for tubes initially ensure you discuss how to avoid stagnation in the system as this will kill the tubes quite quickly.

dathi

30 cheap Chinese tubes installed 14 years bottom of cylinder at 29 today

DC999

https://www.boards.ie/discussion/comment/120000020#Comment_120000020

Man, that's class. It's a teen and still rocking. 29C and it's Baltic outside. 37C starts to feel hot on our skin, so you've only to heat it 10C for showers. I may well stick them down on the DIY list in time if I feel brave enough

MicktheMan

https://www.boards.ie/discussion/2058275742/solar-thermal-for-water-heating

OP, when asked this question by clients, my first response is to ask them what they currently spend on hot water. This is often met with a "havent a clue" type of answer. So this is the first thing that needs answering. For most families the cost is between 300 & 500 euros. (This has obviously increased lately with the spike in energy costs worldwide.)

But my point is that most people would be surprised by how little their hot water costs compared to their heating costs (typically a sixth of your gas bill is used to heat your water). Therefore, for example, halving your space heating needs would be a much better bang for buck than chasing half of your hot water usage.

If for example 5 grand gets you a solar system for half your hot water needs, using this 5 grand instead to seriously tackle the easy low hanging opportunities to reduce your space heating needs might be a much better use of funds available.

unkel

Good points @MicktheMan. I wouldn't even bother guessing how much hot water you use unless you are in a large household with lots of females. Like me. Between myself and 4 adult and teenage women, we use lots and lots of hot water and I am delighted a lot of it is coming from solar thermal, which for my situation is the cheapest and most efficient way.

For the vast majority of families who use a lot less hot water than we do, solar thermal is not the best way

windowcills

A few of ye mentioned very low temps in this thread, I thought the tank has to over 65oC

graememk

https://www.boards.ie/discussion/comment/120006379#Comment_120006379

A very good video about it on heat geek https://youtu.be/oJeyc_cGIMU

Solar thermal is usually setup to heat the bottom (coldest) of the tank so it might not get it to 65 unless it's a really sunny day, but it might lift it from 10c to 30c so you only have to rise it a little bit more via other means