Solar Thermal Install

[Onoff]

Ref overboiling...erm, shutters?

 

[Onoff]

In fact we'll refresh this system by replacing the collector with pv shortly.

I read "free panels in France"!

 

[voipio]

The Worcester Bosch TDS 10 solar thermal controller (also known as the Steca TR 0301 manufactured in Germany) does seem to remember settings after a power cut. It has a quirk of going through phases when the temperature sensor readings of the tank and solar panel temperatures get quite noisy making the pump cut in and out at times, but seems to work quite well. 8m2 seems like a lot of solar thermal panel area for a domestic setup, especially in sunnier climates, and solar thermal panels are four to five times as efficient as solar PV panels.

 

[jmp49]

I read "free panels in France"!

They're pretty trashed, the vacuum seal and outer is broke on a good half the tubes after all these years and I'm also fed up with persistent weeps from the flashing as the tubes pass out the roofspace. When we get them down off the roof probably there will be more issues because they've been left dry for a few years after I gave up on keeping it going.
Yes you could protect the panels from the sun somehow, but shutters etc are going to have to live on a roof for years, being snowed on/getting hit by wind etc so I imagine they would bring their own issues. PV will just be passive when disconnected, no systems to fail when you need it to work most.

Voipio, it was supposed to be the sole source of heating to run the house's underfloor heating system, and spec'd for that. We didn't buy some panels and a tank, it was supposed to be a engineered solution based on records for the area and cost more than the pv panels that will be replacing it will. The tank will be kept as the on demand heat exchanger at the top of the tank servicing domestic hot water has been good and we ordered it with extra tappings and multiple immersions which we've since connected other energy sources up to, and used the immersions for frost protection only. But the solar water bit always badly underperformed when we needed it, and the design had zero consideration to what to do with the excess heat or what if that thing that went wrong at the worst possible moment went wrong. And go wrong it did, usually when I was away working and my mrs's was home alone, getting panicked phone calls that the house was boiling steam out the panels yet again and telling her to pour hot water down the well frantically.

Ymmv, just passing on my (very) negative experience.

 

[gaz1]

thanks for your input there jmp49

certainly reads as poorly engineered and certainly shouldnt have been specked for just heating the underfloor heating system

 

[Onoff]

I've a rather good (imho), now out of publication, book from CAT, the Centre for Alternative Technology in Wales. Shows two DIY panels, one from an old radiator and the other from copper pipe. It also details a DIY solar controller.

 

[Mikes]

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.

You've summed-up very clearly the problems from an end user experience. I've encountered several commercial installations where overheating has killed off all hope of reliability and energy saving. Fortunately, we just don't seem to have the solar thermal installations still being put forward. In the early days of PVs, there were problems with quality and particularly multiple panels being linked to one inverter but these have long been ironed-out.

 

[jmp49]

thanks for your input there jmp49

certainly reads as poorly engineered and certainly shouldnt have been specked for just heating the underfloor heating system

It was to 100% cover DHW also, the 1000L storage tank has a on demand instant heat hot water heat exchanger for this tapped into the very top of the tank with its own pump triggered when you turn the hot taps on to run bath/shower/etc. So the hydronic solar was on its own sealed circuit on a coil in the tank. That's why we could control it to a degree sometimes by pouring gallons of steaming hot water out the taps down into the well on hot days but as we were on metered mains water supply as the well wasn't human consumption safe, this was a total (expensive) loss and I ended up adding a energy dump loop into the well with its own pump. Which is yet another pump circuit to control, maintain, frost protect with antifreeze levels, source of heat loss in winter, repair when it stuck on a hot day, have ups capacity to serve etc. It was permanently like walking a tightrope of disaster in summer.

So the real takeaway I think should be to carefully pay attention to this aspect and design something robust to cope with the available energy when it over/under generates or the pumps get stuck/other failure/power outages. As Mikes has said, I think its actually cost more than operating a oil furnace would have over the period due to the unreliability, inability to cover demand in cold weather and issues.

 

[Matchless]

onoff has given permission for a hijack, similar problem and next to no idea how to do it.
I ended up with six flat plate solar panels, something like 6 feet by 4 feet each, Wolf, German, I also have some control gear and an expansion vessel but suspect that will be too small, had it for years, I have started converting the house to underfloor hot water heating, kitchen done, hall and study next, modern gas boiler, mains pressure hot water with a cylinder.

Original plan was to mount them on the back of the garage next to the house, now want to mount them as a car port behind the garage as a carport roof, less obtrusive and easier to maintain, south east facing, will get decent sun for a lot of the day.

I want to use the panels to heat our hot water and do a lot of the house heating............ I know, I know, but I do have a plan, I have an indoor swimming pool of a decent size that we (used) to heat from the gas boiler, too expensive to heat these days, so plan is to dump heat into the pool and draw it out when needed, the pool has a large mass of concrete around it and so only drops around 1 degree a day when we stop heating it.

As the solar panels will be low down I propose to install a wind out blind to shield the panels in the summer as a control method but as I said I know nothing...........

pictures to follow,

 

[Onoff]

One for the mods please. I've a publication here, Solar Water Heating A DIY Guide, that I purchased years ago from CAT, The Centre For Technology in Wales. It's out of print and no longer available as I understand. It has an ISBN number but no copyright I can see. A quick screengrab of part of it. Can I put further screenshots, extracts up from it?

Cheers

 

[Onoff]

I have an indoor swimming pool

You didn't say you was posh!

 

[Matchless]

You didn't say you was posh!

I built the house myself 35 years ago, sits on a decent plot, bought a tumbledown bungalow, lived in it for three years before building first the garage, then the house, then when I demolished the last of the old bungalow, the pool,

 

[dobbslc]

Garage first?

 

[Onoff]

I built the house myself 35 years ago, sits on a decent plot, bought a tumbledown bungalow, lived in it for three years before building first the garage, then the house, then when I demolished the last of the old bungalow, the pool,

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

 

[Gareth J]

onoff has given permission for a hijack, similar problem and next to no idea how to do it.
I ended up with six flat plate solar panels, something like 6 feet by 4 feet each, Wolf, German, I also have some control gear and an expansion vessel but suspect that will be too small, had it for years, I have started converting the house to underfloor hot water heating, kitchen done, hall and study next, modern gas boiler, mains pressure hot water with a cylinder.

Original plan was to mount them on the back of the garage next to the house, now want to mount them as a car port behind the garage as a carport roof, less obtrusive and easier to maintain, south east facing, will get decent sun for a lot of the day.

I want to use the panels to heat our hot water and do a lot of the house heating............ I know, I know, but I do have a plan, I have an indoor swimming pool of a decent size that we (used) to heat from the gas boiler, too expensive to heat these days, so plan is to dump heat into the pool and draw it out when needed, the pool has a large mass of concrete around it and so only drops around 1 degree a day when we stop heating it.

As the solar panels will be low down I propose to install a wind out blind to shield the panels in the summer as a control method but as I said I know nothing...........

pictures to follow,

Is the pool to be used as a pool again if it gets hot? Or is that not a priority? I guess a critical factor if it's just going to be a heat dump is how much energy it takes to maintain the heat each day. That'll give you a rough idea of how many kWh you've got to potentially limit panel production to with the blinds...?

However, if you never wanted to swim in it again it could become an inter seasonal heat store!

 

[Onoff]

However, if you never wanted to swim in it again it could become an inter seasonal heat store!

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).

 

[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!