Solar water thermal panels: The installation… (w pics)

following on from this thread

first of all a massive thanks to smudger666 for his offline help, edukator for his posts and especially globalti for directing me towards Peter at http://www.solarproject.co.uk/

A local specifier quoted for installing an 80 x 58mm tube system that was MCS certified (i.e. eligable for RHI payments) and came out at a number around £7,000. By my financial calcs, even with the gov RHI payments, Id not see payback for the best part of 17 or 18 years at that kind of capital cost.

Following globalti’s lead I got in touch with Peter at solar project and with some help from him and other sources have designed and acquired the parts to install a 60 x 58mm tube set up (that can be easily extended at £460 per 20 tubes) for just under £2,000. Even without the RHI payments I reckon my payback is going to be closer to 5-7yrs. It also reduces the amount of wood pellet fuel I need to lug about over the summer months.

The system is to augment this biomass boiler set up. Both the boiler and the Solar panels connect to this 700L thermal store where the energy is stored for use.

Over the last few days and the next few Im in the process of installing the system myself. If you’re interested, I’ll be posting pics and notes on the install in here when I come in for coffee breaks.

This is where the panels are going. On the ground in a special bed in the garden. I dont like water services in roof space. Being on the ground means I can clean, repair and service the panels more easily. The gravel bed can be sprayed for weed control.

the ducting you see there comes up back in the boiler room:

first problem was that the DN20mm insulated steel pipe would not pull through the 50mm conduit. My fault, I thought there’d be more clearance and since its been over 9 months since I laid the conduit its probable that the run isnt un-obstructed by compression of the conduit along its full length. So a lot of cursing, swearing and thinking later…

…I cut a new shallow trench in the veg garden gravel and across my nice new lawn within which to lay some more 50mm conduit, but this time through which Id already pulled the hose whilst above ground and dead straight. Of course, this also meant breaking into the boiler room wall again. Fortunately I still had a spare “Insuduct” lying around that was about to go on eBay. This makes for a nice breakthrough.
2x 17m runs of DN20 soalr hose:

Finished installing the conduit yesterday so could then crack on with the first frame/manifold assembly so that I could get the copper flow/return tails in the right spot. Just about to go back out and assemble the next two panels before getting on with the copper work in the boiler room.

Any questions Ill answer when I get back in in a few hours time. But take some time to have a look over Peter’s site for more info.

harrumph.
I thought there were more forumites interested in this stuff than that 🙁

ah well. for any lurkers then:

two more panel racks & manifolds assembled and all of them joined together

I like what you’re doing! I’m just about to remove an old Parkray boiler and replace it with a Stovax Stockton 8HB Boiler and reconnect it to our radiators!

I’ve had estimates from HETAS registered fitters and TBH they’ve not filled me with any confidence what so ever. In the I’ve gone with a local builder who isn’t registered, but by using him I am saving way over the cost of getting building regs in (although that may cause problems in itself) and I feel a lot more confident in what he has explained to me.

Little concerned about the depth of that trench, take it the conduit is reenforced?

That is one big system!

Parents have just one panel and it already produces too much hot water for the house!

Make sure they are insured, they had a few crack over winter and had to make a claim.

I’ll be interested to read when you’ve got some results to post. I’m 9° further south and my solar hot water heater works very well until about the end of October (which is when we fire up the wood burner for the first time) and from the end of March (which is when we last use the wood burner). The main problem in Winter is that I’ve got it a 30° from the horizontal (I could only get planning permission for integrating it into the roof), not great in the Winter but perfect in Summer.

You’re near Worcester IIRC which means that in December the sun will be 90 – 52 – 23 = 15° degrees above the horizon at midday. I therefore reckon you’ve got the angle too shallow for optimum efficiency from October to March.

That area of panels would provide all your domestic hot water for the sunniest half of the year and I reckon you could boil the primary circuit unless you cover some of them in summer. People around here have to cover their panels when they go on holiday to prevent boiling.

I assume that all ball games are now banned in your garden!

harrumph.
I thought there were more forumites interested in this stuff than that

I’m interested.

Wow. Impressed. My M&E colleagues have just specced a solar pre-heating system to accompany the air source heat pumps and under floor heating system, rainwater harvesting system and self contained packet sewage farm system for a project im running.

Whilst I don’t have a clue how it all works, it sure sounds impressive, although having just opened the tender returns and found its £400k over the original budget estimate, the client suddenly thinks that BREEAM isnt so important afterall 😆

I’m interested. Keep on posting!

I assume that all ball games are now banned in your garden!

I would imagine that the water tube panels are pretty robust 🙂 Might be a different story with PV.

Looks like a great project!

You’re near Worcester IIRC which means that in December the sun will be 90 – 52 – 23 = 15° degrees above the horizon at midday. I therefore reckon you’ve got the angle too shallow for optimum efficiency from October to March

If this ^^ is the case, how hard would it be to have the tubes on an adjustable 2-position frame that can be moved in the winter months to a more efficient position?

replacement tubes are only about £25 each, so not that worried about them nor about getting them insured separately.

its very unlikely that the system will boil the primary as there is over 900 litres of water to heat up first. That’s over 100kwH of energy.

There’s also a suppression system in the secondary circuit which kicks in at 95 degrees cooling down the thermal store.

Finally since Im using an unpressurised system, if the primary circuit were to overheat, it would simply boil out through the header tank. not the end of the world.

the trench is shallow but its located in a safe area. The conduit is twin wall poly, and robust enough to keep the insulated steel hose safe.

Strictly no cricket in the garden 😉

Edukator – the angle is interesting. Mine are somewhere between 35 and 40 and thats the frame setting. Im happy with them there for now. but will keep it under review.

I’m interested to see how well the insulation copes with keeping the water hot back to the boiler. 17M sounds a long way to me, not that I have any experience of building something like this – I’d just assumed the roof was the best place to avoid transmission losses and save a bit of space (not an issue for you it looks!)

stump – I was thinking about that, but since I have rigid connections between the panels and they weigh a fair bit, theres no way you could tilt all three of them simultaneously and not break something.

More use of flexible hose might solve the problem but I concluded that was probably too much faff.

Brassneck: Ill be able to check losses as I can simply measure the temp at the hot side of the indirect coil as it goes in to the thermal store and compare that with the return temp from the panel (there’s a temperature probe port on the manifold)

as I said there’s 13mm of insulation around the steel hose, then the twin wall poly conduit. And it’s in the ground, nto the air. I think it’ll hold up OK.

Pah! Computer controlled sun tracking array would have been the way to go 🙂

I was wondering if I could rig something up with old chainrings and bike chains….proper heath robinson 🙂

EDIT: righto, off to do some copperwork.

Pah! Computer controlled sun tracking array would have been the way to go

Looking at the set up you have, is the a way of jacking up the wood base at one side to change the angle? It could pivot around the front edge and the connections would stay in place.

Tracking mechanisms are not financially worthwhile for solar PV, so trying to move around that size of kit would be mad. However, a few wooden wedges at the back of the wooden base would shift the angles nicely for optimal winter sun.

*What headset for slackening solar thermal panel angles?*

Interesting stuff.

jeez Ive got to practice my soldering! 😉
Like a silver bukkake flick….!

Anyway, manifolds all plumbed in. Some joints more passable than others. Wont know just how crap my soldering is until I fill it. Fortunately the system will never run above atmospheric pressure, so it may be sympathetic to my awful copperwork 🙄

Two kinds of insulation: El cheapo stuff on the cold side, uber-expensive armourflex stuff on the hot side.

Tomorrow it’s into the boiler room to do a load of soldering and connect up all the gubbins. First a trip to Bradfords for a bit more 22mm though.

Auto air vent at the highest point of the circuit. Will also need to use a couple of manual vents in the boiler room for some local high points that will be unavoidably built into the loop.

my best* joint!

* only one that doesnt look like gash…

Might be talking to total pap but I think using standard pipe insulation for the return pipe is a mistake as you will loose excessive heat and the panel will be fed with cooler water resulting in a lower temp of hot water leaving the panels.

I might be talking total rubbish. Love the project, you are very well setup.

Losses are greater at higher temperature.

I think the losses on the cold side of the panels will be minimal. If the return temp is high (and therefore making greater losses), however, then I will already have to have masses of hot water in the thermal store.

(i.e. in order for, say 50deg water to be returning to the panel, the water at the bottom of the 700L thermal store must be nearly 50degs which means there’s loads of 50deg + water in the tank, so to lose further energy is not really a worry)

a friend was recently in Cameroon building a slap-dash version of what you’ve got going.

a large blue plastic drum for the tank, a load of pipes welded up like yours that sit beneath glass in a wooden tray. the whole lot then got painted black and the drum insulated. the drum was refilled by a stopcock type vavle.

think it cost about US$ 60 and it provided enough hot water for the church kitchen where lots of villagers go to eat.

BTW, this is the approx layout.

A tip I was given was having the fill loop come up from below so as to prevent thermal syphoning of hot water into the un-insulated header tank.

The other tip was to add an expansion feed. Im guessing because it wont have the head of water on it making a quieter expansion route. Also apparently a small pin hole in the last 90deg of the expansion feed above the header is recommended, again to stop “glugging” and “bubbling” of expansion flows.

Your costs sound similar to my folks collectors. They have 5 in the conservatory roof.

Looks good. Do you think that 5-7 years is an acceptable payback period (for the average man) for this type of project?

I plan on staying in the barn for at least 15-20 yrs. The installation without substantial rework could last for 15-20yrs.

Payback for me is the replacement energy for biomass fuel (at about 5p/kWh)

If I was using a less bunny-cuddly fuel, Id be morally even more incentivised by the system even though, oil, say is about the same price per kWh as my pellets.

If you decided to sell, how much of a selling point do you think it would be?

tricky to say.

You could put a figure on it based on savings compared to an oil system.

In theory I could generate around 100kWh per annum per tube (i.e say, 6,000 kWh from those three panels).

In biomass fuel terms, that’s around £300 in today’s prices.

in perpetuity at, say 5% (multiple 20) then that’s worth say 6k.

Its not something that I think will be explicit in a house price, more that it might attract a particular kind of buyer.

More attractive still is my SAP/environmental impact rating of the barn. oodles of insulation keeps the running costs down.

Stoner, that’s looking fabulous. I wish I had the energy (sic) to do something as ambitious. So when we’re riding in the Malverns do we come round to your place for a long hot shower?

for you, moses, there’d even be a bed.

😀
Thanks but no need- I’ll be in the van.
I owe you a tour of that anyway.

then invite yourself up for a stopover/beers and ride.

A CH pump circulates water so fast that you’ll have trouble measuring differences around the primary circuit. On a German friend’s system about a degree and it’s no guide to how much heat you are losing or where from. I’ve insulated pipes with a normal pipe wrap like in your photos with a sewage pipe diametre insulator over the top.

Excellent – did you need planning permission for the array?

I, as you know, am an idiot, and don’t understand this at all. Can someone explain how it is work please, in very simple terms? Thankz.

Looks good though. Can I get a smaller version stick on my balcony annoy my neighbour?

My tomatoes are better than his, as my balcony gets more sun than his. This infuriates him, but pleases me immensely. 🙂

The sun heats up water in the tubes in that rack thing. That warm water is then pumped through to heat a big tank inside Castle Stoner, which in turn is used to heat the water and the radiators – if he so chooses.
The big tank inside is also heated using a big **** off wood pellet boiler – quite handy in winter when there aint enough sunshine, sunshine.

My dissertation was on the thermal performance characteristics of solar collecting water heaters. Looks like a decent system for the money you’ve paid.

Fred – you get systems that have water running through them and you also get systems that have some other fluids that contain corrosion inhibitors and antifreeze which use heat exchangers to move that heat to the water.