WestcountryWonderer Posted October 24, 2022 Share Posted October 24, 2022 I'm looking into fitting solar thermal when we build our extension. I already have PV which I am in the process of diverting to the immersion heater but also considering batteries so wondering if solar thermal as well would be a good boost to the hot water and allow the morning PV to put some charge back into the battery again. I remeber finding a supplier who was recomended for teh DIY world, good quality kit but happy to deal with you and me as well as trades which a lot of the big auppliers aren't so helpful if youre not trade. Does anyone recomend anywhere for supply but also for information about the set up etc? Looking to get an upderstanding for how the system is installed as well before I commit to a definate yes. I'm looking for in roof panels so presumably flat panels if that makes any difference to recomendations? Link to comment Share on other sites More sharing options...
Conor Posted October 24, 2022 Share Posted October 24, 2022 Would be much more cost effective to add more PV panels. How many do you have currently? Would the orientation of the new roof be suitable? Sorry, no real first hand knowledge of solar thermal, just that it's more expensive than PV and has longer term maintenance issues and higher failure rates. Link to comment Share on other sites More sharing options...
Gone West Posted October 24, 2022 Share Posted October 24, 2022 3 hours ago, WestcountryWonderer said: I'm looking into fitting solar thermal when we build our extension I moved into a bungalow last that had a 3.8kW PV array and a 1.4kW flat panel solar thermal system already fitted. The solar thermal heats our DHW and the PV heats the DHW through a Solar iBoost diverter. The solar thermal is a low maintenance system which I gather hasn't been touched for several years. I plan to replace the existing 140l vented hot tank with a larger UVC to make better use of the two systems. Link to comment Share on other sites More sharing options...
jack Posted October 24, 2022 Share Posted October 24, 2022 4 hours ago, WestcountryWonderer said: I already have PV which I am in the process of diverting to the immersion heater but also considering batteries so wondering if solar thermal as well would be a good boost to the hot water and allow the morning PV to put some charge back into the battery again. I think the general consensus is that solar thermal is at best marginal compared to PV. The latter has a much longer usable season, plus when the tank is completely hot, you can keep using surplus electricity for other things. If you're considering batteries, I think the maths is even more firmly in the PV camp. Perhaps the only potential issue is how much PV you have installed now, and whether your local network operator might object to you connecting more. 2 Link to comment Share on other sites More sharing options...
JohnMo Posted October 24, 2022 Share Posted October 24, 2022 I have a drain back solar thermal panel to install. It will be hooked up our buffer, which preheats DHW in the summer and is a buffer proper in the heating season. In the winter the buffer is at around 26 degs, so expect to get a decent yield from the thermal, as only a low temperature is needed in the panel to start producing usable output, amount sun shine needed isn't expected to be that great. Link to comment Share on other sites More sharing options...
Dillsue Posted October 24, 2022 Share Posted October 24, 2022 Weve got a 30 evac tube array that pre dates our PV. I beleive that evac tubes give a higher output per m2 compared to PV but obviously PV is more flexible. In terms of reliabilty, ours was installed in 2006 and not had any problems. Changed the heat transfer fluid after 10 years and have topped the pressure up twice from the mains water. If you want in roof panels and flat plate collectors its probably worth doing some research on the performance versus similar area of PV. If you want to see how systems can be connected up, google Resol Deltasol and have a look in the controller manual as theres lots of schematics of differing systems. Link to comment Share on other sites More sharing options...
WestcountryWonderer Posted October 25, 2022 Author Share Posted October 25, 2022 Thanks for the comments. Additional PV is the other option I have so that might be the better route. I have 6.5kWp (on a 3 phase supply so still within the 3.6kWp per phase) split 50:50 on east/west facing roofs. I can potentially get some more panels on a south facing roof when we do the extension. Just debating if the council planning will have anything to say if the PV (or ST) goes on at the same time as doing the extension works. I'll go and trawl through the PV part of the forum next then! 1 Link to comment Share on other sites More sharing options...
Dillsue Posted October 25, 2022 Share Posted October 25, 2022 11 hours ago, WestcountryWonderer said: Just debating if the council planning will have anything to say if the PV (or ST) goes on at the same time as doing the extension Unless youre in a conservation area or listed building, Im fairly sure pitched roof mounted panels are permitted development Link to comment Share on other sites More sharing options...
Alan Ambrose Posted October 25, 2022 Share Posted October 25, 2022 >>> I think the general consensus is that solar thermal is at best marginal compared to PV. Excuse my ignorance, but I don't quite understand how a fairly low tech sun->water/pump->copper loop->DHW system is not cost effective compared to a fairly high-tech sun->PV panel->inverter->immersion->DHW system? I'm not doubting that you're right - but just wanting to understand how 'loads-of-expensive-tech' works better than a 'low-tech-sun-heats-hot-water'. I know that our continental cousins use the latter and they have more sun but...? TIA, Alan Link to comment Share on other sites More sharing options...
WestcountryWonderer Posted October 25, 2022 Author Share Posted October 25, 2022 10 hours ago, Dillsue said: Unless youre in a conservation area or listed building, Im fairly sure pitched roof mounted panels are permitted development Yes That is my understanding. And again, I'd do an in roof install as we're re-roofing at the same time so the panels wouldn't protrude past the existing roofline. However we do have some listed buildings nearby (although ours isn't) And the planning officer I was speaking to did make a comment about adding them into updated drawings (as we're looking to make a non-material ammendment elsewhere) but I never managed to get him to clarify his comment as I don't really want to back myself into having them by putting them on the drawings when there are a lot of factors that could affect fitting them - money/DNO approval etc etc. Any way. A bit of a tangent there! Link to comment Share on other sites More sharing options...
WestcountryWonderer Posted October 25, 2022 Author Share Posted October 25, 2022 4 hours ago, Alan Ambrose said: >>> I think the general consensus is that solar thermal is at best marginal compared to PV. Excuse my ignorance, but I don't quite understand how a fairly low tech sun->water/pump->copper loop->DHW system is not cost effective compared to a fairly high-tech sun->PV panel->inverter->immersion->DHW system? I'm not doubting that you're right - but just wanting to understand how 'loads-of-expensive-tech' works better than a 'low-tech-sun-heats-hot-water'. I know that our continental cousins use the latter and they have more sun but...? TIA, Alan I would tend to agree with you (in my also limeted knowledge) in it's basic form, solar thermal is a pump and a valve and an expansion vessle and two heat exchangers - on the roof and the cyliner. aside from the pump and valve (which is no different than the central heating systems we all have), nothing else moves. Happy to be corrected here. My only thought is that PV has no moving parts at all, and the systems whilest containing complicated electronics, are failry well developed to be reliable. In my mind it comes down to which is more efficiant, and most cost effective. Link to comment Share on other sites More sharing options...
joe90 Posted October 25, 2022 Share Posted October 25, 2022 From my reading on the subject I believe the Achilles heal of solar thermal is the dumping of waste heat to avoid overheating, not a problem with PV. Link to comment Share on other sites More sharing options...
WestcountryWonderer Posted October 25, 2022 Author Share Posted October 25, 2022 5 minutes ago, joe90 said: From my reading on the subject I believe the Achilles heal of solar thermal is the dumping of waste heat to avoid overheating, not a problem with PV. Yes, I think this is correct. I think the systems have to have a bit of thought put into them to avoid this. On the other hand as you say, PV either gets used for other loads once the cylinder is hot, or worst case just goes back into the grid Link to comment Share on other sites More sharing options...
SteamyTea Posted October 26, 2022 Share Posted October 26, 2022 7 hours ago, WestcountryWonderer said: PV either gets used for other loads once the cylinder is hot, or worst case just goes back into the grid Or the system shuts down in a safe manner. It is easier to route cables than pipes. PV is not exactly new technology, been around 50 years in the domestic setting. The efficiency is a tricky question to answer. While, for any given amount of area and insolation, ST will absorb more energy over time. The trouble is, because of the crude on or off control, much of that absorbed energy is of little use e.g. too cold or too hot. PV while needing a minimum amount of photons to lift the electrons to a higher energy state, produces a more usable amount of energy because the electronics in the inverter converts and conditions the output to what is needed i.e. 230V 50Hz, and that can be added to the general mix of electrical power from other sources, so can be used to help drive a heat pump, boosting efficiency more. Link to comment Share on other sites More sharing options...
Gone West Posted October 26, 2022 Share Posted October 26, 2022 14 hours ago, Alan Ambrose said: Excuse my ignorance, but I don't quite understand how a fairly low tech sun->water/pump->copper loop->DHW system is not cost effective compared to a fairly high-tech sun->PV panel->inverter->immersion->DHW system? I don't understand why it seems it has to be one or the other. What is wrong with having both. If you have the G98? limit for PV already fitted why not fit ST, rather than increase your PV. 1 Link to comment Share on other sites More sharing options...
billt Posted October 26, 2022 Share Posted October 26, 2022 14 hours ago, Alan Ambrose said: >>> I think the general consensus is that solar thermal is at best marginal compared to PV. Excuse my ignorance, but I don't quite understand how a fairly low tech sun->water/pump->copper loop->DHW system is not cost effective compared to a fairly high-tech sun->PV panel->inverter->immersion->DHW system? Last time I looked commercial systems were very expensive compared to PV systems. Just before the PV FIT bandwagon started I installed a large evacuated tube solar thermal system. At the time PV was very expensive and solar thermal was a fair amount cheaper per unit of energy collected. Then FITs arrrived, PV boomed and PV prices dropped through the floor, while solar thermal prices increased slightly, then most of the solar thermal suppliers disappeared as there's virtually no market any more. PV panels are fairly simple mechanically and mass produced on a large scale; from a manufacturing POV evacuated tubes are more complex, use more materials and are smaller scale. A decent solar thermal system isn't particularly simple. You need a pump controller to ensure that the pump only runs when there is energy available, so it doesn't suck the heat out of your tank and to try to ensure that it doesn't freeze and damage the system and try and protect it from boiling and dumping all the solar fluid out of the OPV. Then there's the water temperature issue. It's quite easy to get a HW cylinder up to boiling with a solar thermal system. That means that you should have a mixing valve on the HW output to remove the scalding risk. Additional work and expense. Then there's the effectiveness issue. Solar thermal works quite well in bright sun but its effectiveness drops dramatically with low illuminance levels whereas PV produces linearly so will still harvest some energy in dull weather. And of course solar thermal is a one trick pony. It will heat water and nothing else. PV will do anything that can be done with electricity, including heating water. 1 Link to comment Share on other sites More sharing options...
Dillsue Posted October 26, 2022 Share Posted October 26, 2022 14 hours ago, Alan Ambrose said: but just wanting to understand how 'loads-of-expensive-tech' works better than a 'low-tech-sun-heats-hot-water'. I know that our continental cousins use the latter and they have more sun but...? Dont underestimate the potential complexity of ST. Youll almost certainly have an electronic solar controller that needs configuring in the same way as a PV controller/inverter does. Therell likely be at least 2 temperature sensors needing wiring back to the controller and wiring for a pump. If youve got a sealed system youll likely have a pressure releif valve, expansion vessel, auto air vent valve, non return valve, mains top up valve. Installation is more involved running insulated(special hi temp insulation) pipes from the roof through the house versus PV cable. Insulated roof penetrations are more involved than those for a couple of PV cables . You need to find space within the heated envelope for all the bits mentioned above whereas a PV inverter can go more or less anywhere. If youre strapped for roof space then evac tube ST may give more kwh than PV for the same area, but if youve got the space then PV is a more flexible option Link to comment Share on other sites More sharing options...
embra Posted January 28 Share Posted January 28 Hey, I'm selling a solar thermal kit on here / eBay. Give me a shout if you'd be interested! https://forum.buildhub.org.uk/topic/37090-solar-thermal-panel-kit-worcester-bosch-fk240-including-pump-station-controller-etc/ https://www.ebay.co.uk/itm/285674793513 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now