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!