Solar Thermal Install

[Roger440]

You will need some kind of mains power backup for summer to run all these pumps sensors etc. I have a large solar array (8m2) with these panels and a 1000L tank with multiple coils in it. In summer if you loose the power for 45 minutes in summer its enough to take the 1000L tank to boiling temperature and boil the fluid out the circulation circuit. We have a UPS capable of running the pumps for a hour, and after that its just a question of replacing failed components after the boil over (the safety valves we use dribble after they have released steam and need replacing each time), I've seen melted normal solder on joints too during this. Also be cautious where the valves point, the jet of steam will be impressive.
In winter it underperforms by far the predictions given to us by the solar design company. So it produces too much energy in summer when you don't need it, and in winter nowhere near enough. Also we're on the 3rd set of pumps in 12 years of operation, they wear and begin to stick occasionally at a certain age and that can be really bad. Also we had a commercial deltasol controller for the solar circuit control, and it has brain dead defaults. If its power cycled it forgets any bespoke settings and it defaults to disabling warming the panels in very cold temperature to avoid frost damage. So if it gets power cycled in winter, we have to go back in to the config and set it to enabled or risk frozen panels. I don't know if newer ones are any saner...
Another note on the tubes, they're fragile as someone already said. We lost the vacuum in quite a few due to hail stones and wind.

I would stump up the extra for the pv, solely on the basis that when it over-generates you don't have to get rid of the excess, and its not dangerous shooting boiling fluids or steam out if things fail. In fact we'll refresh this system by replacing the collector with pv shortly. And this is from having a similar set up running for 12 years. Right now its drained and the property vacant so I don't have to mess around trying to service it thankfully. If I sound bitter, that's because I am. We paid a lot of money to a professional company to spec and supply for our custom requirements, and I feel that it was a massive mistake.

Interesting stuff. Thanks for posting.

Like onoff, i keep pondering thermal solar, albeit primarily for a workshop.

PV is all fine and good, but with panels and batteries, its a chunk of money with no DIY option.

All the talk of IBC's i dont really understand. The amount of heat you can store, even if insulated isnt that great. Plus made of plastic.

I did find one website using a 20000 litre buried milk tanker. At 90 degrees C that 1850 KWH of energy. Which really isnt that much.

I want it to work, because i need to do it cheap. Will see how onoff gets on!

 

[Matchless]

Do you have good (read excellent) air tightness and an efficient, centralised, mechanical ventilation heat recovery system?

In the pool room or house?

 

[Onoff]

In the pool room or house?

Erm...the thermal envelope should be contiguous and "wrap" both. If you then separate the two because for say humidity control purposes en that's another thing.

There's a lad over on Buildhub who's pool isn't separate per se. Doesn't suffer from corrosion on any metal fittings etc. He does have MVHR.

 

[Onoff]

Will see how onoff gets on!

Don't wait up!

 

[Matchless]

It's only really any good as such if it is contained with the thermal envelope and that the envelope is super insulated. 300mm EPS under the floor will still lose 8% of heat (through the floor).

From memory the pool has 12" thick walls and floor so a large thermal mass plus the water, the walls have 2-300mm polystyrene to prevent clay heave and for insulation but the floor is I think onto the clay, can did out the plans, it looses 1 degree a day when we stop heating it or the pump fails.

I am in a sheltered location in a slight valley and a good way south, I can see London so generally we do not get much bad weather, I would like to use the pool but accept that sometimes it will be too hot.

I do not expect to store enough heat to last me for weeks on end, rather to supplement the gas boiler and provide "free" heat for the pool,

I am sure pictures will help, the solar that I have cost me nothing, it is all "new" and unused, I recon that say two panels would be overkill for house hot water, the other four overkill for the pool so there should be quite a bit to spare in spring and autumn to help the house out?

I do have data sheets for the panels somewhere, must try to find them!

 

[gaz1]

its a chunk of money with no DIY option.

All the talk of IBC's i dont really understand. The amount of heat you can store, even if insulated isnt that great. Plus made of plastic.

whichever way its a chunk of money

hot tub reference

An average 4 seater hot tub holds about 1,250 litres of water, while a larger 7 seater hot tub will hold around 3,000 litres. For comparison, an average household bath tub holds around 80 litres of water – so that's up to 37 baths full of water, each time the hot tub is filled!

vs 250/300 litre

Gledhill StainlessLite Plus Direct 90L - Heater Shop

Gledhill StainlessLite Plus Direct 90L

www.heatershop.co.uk

vs ibc tank

1000 litres

1000 Litre Reconditioned Opaque White IBC - Plastic Pallet - Grade A

Our 1000 Litre White Reconditioned IBC with Plastic Pallet is the best value reconditioned IBC in the UK. White bottle IBC's are UV-resistant prolonging the freshness of its contents.

www.kingfisherdirect.co.uk

its maths vs water so if it takes x2/3 of f to heat the water 1f which will reduce as the water heats up therefore the more mass of water will take much longer to heat up

Yes, you can run a hot tub on solar! It all depends on the amount of sun you get. Solar-powered heaters can heat water up to 100 degrees with only six hours of sunshine.

[Pros & Cons] [How] Can You Run Hot Tub On Solar?

Can you run hot tub on solar? Find out the two options available and find out how to use solar power to heat your water up to 100 degrees!

hottubsreport.com

so a hot tub of 1000 litres takes 6 hours to heat then an ibc will also take the same the difference is in the cost

i suspect 2-3 years before it may fail but if buying at 30.00 thats 15.00 a year to dump hot water into it

it gives you time to save up to buy a second heat store at under a 1000.00 or build yourself a hot tub and use it as a heat dump on red hot days

ive given you the wood heat needed to heat the pool and the hrs and also the heat needed to heat the pool vs solar thermal
but you also have to remember the amount of thermal collectors you have 2 of them going into that pool will warm it up well

 

[DAPPH]

What I've always been told on the various solar thermal courses I've done over the years

It certainly applies to our SW orientated set up
The sun takes time to move through the angle of sunrise to be high enough in the sky to be of use in a PV panel . Usually around 11.00 hrs. by the time all the night air moisture is burnt off Or panels don't really start chucking power out till about 12.45 hrs. then they continues till sunset which is often 21 hrs or so in summer . Think we might also be lucky and get some reflected UV from next doors tiled roof as we paid for our set up in just over half the expected pay back time . Almost all our FIT readings are now having to be submitted with a photo of the reading . I've set you a " Woolworths " webcam with a ring light of LED's on an arm so all I have to do is plug the USB cable into an adaptor lead on my PC.

 

[DAPPH]

other option is to add a valve and dump hot water down the drain

This option is to be avoided - if you are on a metered water supply. That is another cost that simply increases, if water is dumped.

Heat the glass house & garage ?

 

[Gareth J]

It's only really any good as such if it is contained with the thermal envelope and that the envelope is super insulated. 300mm EPS under the floor will still lose 8% of heat (through the floor).

Not necessarily. I agree regarding the insulation but a big thermal store needs to be thermally isolated from the building and therefore can be physically separate (but practicably accessible). Needs to be separate because in summer, when the store is at its hottest, is when you least want heat in the house. There is some success using bore holes as ISTSs, a heat pump dumps heat down them in summer, on solar electric, and pulls it back out in winter.

Not really relevant here though as sounds like swimming is still on the cards!

 

[addjunkie]

Heat the glass house & garage ?

I know a farmer who does that to waste as much heat as he can, as hes on RHI from his pellets system

 

[Onoff]

So glad my kids have stopped using the electrically heated hot tub here a couple of years or so back. One of those inflatable Lazy-Spa things.

Must be pretty foul in there by now. I never wanted the thing so it was all SWMBO's doing and hers to test/add chemicals to, to clean and drain periodically. The year it fell out if use she just put the cover on and left it sat there. Didn't bother emptying it! Saying that we have had 3 parents die on us in that time so other things etc!

Even though uninsulated the cat will happily stretch out atop the black cover even on a cold winter's day.

(That's the hot tub being not insulated, not the cat...).

 

[Onoff]

Not necessarily. I agree regarding the insulation but a big thermal store needs to be thermally isolated from the building and therefore can be physically separate (but practicably accessible). Needs to be separate because in summer, when the store is at its hottest, is when you least want heat in the house. There is some success using bore holes as ISTSs, a heat pump dumps heat down them in summer, on solar electric, and pulls it back out in winter.

Not really relevant here though as sounds like swimming is still on the cards!

Fair enough, understood. Here to learn!

I was in part thinking of the lad I know who has the internal pool but doesn't use as a heat store.

Definitely don't want it too hot...like that scene in Dante's Peak!

 

[Matchless]

The pool is about 30,000 litres, if I have the maths right, flat plate panels are 2mtr x 1mtr, 6 off, panels would probably go where they are stacked along with the old railings and sheets of ploy, to form a car port, not the best from the sun position but I don't want them on the house roof amd with dormers everywhere the best places are taken,

You didn't say you was posh!

we aint

 

[Matchless]

Hmmm, must mend the mower!

So maybe a phase1, install solar panels to heat the pool, see how that goes and then think about stealing some heat for the house and hot water system, I think a wind out blind over the top of the panels will be essential.

 

[Roger440]

whichever way its a chunk of money

Thermal, if you make your own collectors and install yourself thats going to cost WAY less than PV and batteries. Obviously you can make it more complex and hence cost more, but i need this to be proper budget.

Which is when i started to look at milk tankers. Not cheap. Going to be 5-7k. Then got to get the tank off the trailer, then dig a very big hole!

 

[gaz1]

mine would be mixed between solar thermal and rocket stove boiler

the rocket stove boiler been the winter extra input not forgetting one log can produce 4hrs worth of burn from it

 

[knighty]

if you add a thermal store, have a coil high up for direct hot water, a middle coil for your heating and a bottom coil for your pool you should be able to cover all your bases

with 30,000 litres in the pool you'll be able to dump heat into it all day long without a worry

if you are worried... add a couple of radiators and a 3 way valve on the solar thermal loop as a heat dump


the navitron forum was great for solar pv/thermal and a lot of very knowledgeable people, people living off grid etc. etc. but it closed down a while ago now

the people on there who'd been running solar thermal for years swore by a simple heat leak radiator - if you can get the radiators up above the panels (or level with them) you can plumb them in with a 3 way valve that defaults to the radiators... that way in a power cut the panels will dump heat into the radiator heat dump by thermosyphon


I don't think a wood burner is really worth it unless you get free wood, or you see running it as a hobby more than a chore to heat the house

 

[Roger440]

if you add a thermal store, have a coil high up for direct hot water, a middle coil for your heating and a bottom coil for your pool you should be able to cover all your bases

with 30,000 litres in the pool you'll be able to dump heat into it all day long without a worry

if you are worried... add a couple of radiators and a 3 way valve on the solar thermal loop as a heat dump


the navitron forum was great for solar pv/thermal and a lot of very knowledgeable people, people living off grid etc. etc. but it closed down a while ago now

the people on there who'd been running solar thermal for years swore by a simple heat leak radiator - if you can get the radiators up above the panels (or level with them) you can plumb them in with a 3 way valve that defaults to the radiators... that way in a power cut the panels will dump heat into the radiator heat dump by thermosyphon


I don't think a wood burner is really worth it unless you get free wood, or you see running it as a hobby more than a chore to heat the house

Im not really getting the pool thing. Much as you put huge amounts of energy into it, surely most of it just disappears. It just an open uninsulated pool. Well in winter anyway.

My theory with a milk tanker was to store hot water for use through the winter when solar input will drop away to near nothing most days.

 

[knighty]

it's not really financially worth it to try and store heat from one season to the next, you'll spend way more on the tank, getting it in position, plumbing it in and then super insulating it than you'll save on heating

you can super insulate your house for less cost and see more benefit

by my quick maths...

volume in litres x 4 x temperature rise in degrees centigrade / 3412 = kwh stored

20,000 litres, from 20'C to 90'C

20000x4x70/3412 = 1641kwh

at 4p/kwh (gas) = £65
at 16p/kwh (elec) = £262

even if prices double... it's a long pay back period... cash much better spent on insulation and solar power

 

[Gareth J]

The pioneering self-heating house

Andrew and Margretta's Grand Designs self-heating house is a UK first. Buried under the earth, the concrete build acts like a storage heater

www.granddesignsmagazine.com

I remember this episode. Was pretty interesting and made a lot of sense. Although did use a LOT of concrete.

Could see more potential with more lightweight homes and an earth store below an insulated tarmac carpark, with the tarmac pumping heat underground in summer and insulation stopping it escaping in the winter. Earth is a useful thermal buffer for low temperatures as, it's kind of self insulating (only need to insulate the top) and is free.

For real world people, the lesson I took from looking into it is that it'd probably pay to insulate a normal house very well to below the footings. Or extend insulation outwards around the perimeter.