New Solar PV installations and removals of thermal solar PV’s

Sam W

I have the same scenario as the other lad - the house has 3 very new thermal solar PV’s for heating water. So I have to either take them down, or have the new panels work around them.

See the two plans below.

The first one is where we install new panels around the 3 existing ones.

The second one is to remove the 3 existing panels and put as many panels on the roof as possible.

Taking the existing panels down would cost an additional 4-digit number for me.

I wonder if this would actually make sense finance wise. The panels were installed in 2018. Still fairly new. I don’t know how much money they are saving me though, but it sounds like a lot of money to take 3 perfectly working panels away.

Would it make more sense to move these 3 panels to the north facing roof instead? They won’t generate as much solar but still better than having none? And does anyone have any idea about the cost of moving it rather than dismantling everything?

homer911

I'm really in a quandary about Solar PV.

I currently have a Solar Hot Water system which as far as I can remember was installed in 2010, so I've had it 14 years.

The system made complete sense when Solar PV was immature and I had three teenage kids in the house and the shower/bath was in regular use. We are now a household of primarily two adults and run an EV. The rear of my house faces more or less South.

I have a 300L hot water tank fed by the solar tubes which includes an immersion.

My current configuration would allow for 7 panels in addition to the Solar tubes. (6 side by side above the solar tubes and a single panel to the right. If I was to remove the solar tubes, I believe I could fit 12 panels on the roof instead.

Would it make sense to ditch the solar tubes at this stage?

10-10-20

Hi! If you have a working system there then I was be somewhat reluctant to replace it as it's serving a purpose and providing a return, except on the flip-side - it's now 14 years old and the availability of replacement parts is potentially questionable.

If the thermal system was replaced with 5 additional panels and an iBoost/Eddi then the gain from that system may provide you with sufficient energy in the Winter-time to exceed the gain from the thermal system, that in itself would be the margin upon which I base my decision on because Summer would be a given for sufficient excess to heat water.

conor_mc

5 panels at say 435w each is 2.175kWp, which would generate around 2,175 kWh per year on a south-facing roof in Ireland. Using 30c as a ball-park average between consumed daytime electricity and FiT export, your annual saving today would be about €650, maybe less as I'm guessing electricity prices will go down before they go back up again.

You also have to pay to remove the solar thermal (possibly offset by selling the parts), and to replace the "free" hot water on an ongoing basis.

I'm just an amateur and don't know how you'd plumb this but assuming the solar thermal is in decent working order, I'd be thinking of leaving it in place and seeing if I can divert any unneeded hot water towards heating my home. Heck, you could in theory do that by filling a bath and a sink or two with hot water in the evening!

slave1

Why ignore N facing aspect of house? any shed?

conor_mc

https://www.boards.ie/discussion/comment/122057572#Comment_122057572

Good point.

North-facing solar will generate about 50% of south-facing annually, at 35 degree pitch. Probably cost more to remove the tubes/plumbing than stick an incremental 5x panels up on the north roof, assuming you have the space.

slave1

and are great for early morning PV April-Sept i.e. to heat water via diverter

JayBee66

I agree with all the comments above. If you have solar thermal then keep it until irretrievably broken.

It's been on our house for as long as yours and creates hot water at this time of year through to the middle of September. Otherwise, it pre-heats water for the rest of the year so less electricity is required to top it up.

A gycol change every 10 years or so. Not when A8 tells us too. Only the one so far.

No need for an Eddi. The pump uses little electricity so the hot water is virtually free and doesn't eat into our FIT export.

When it does give up then we'll get some sort of heat pump hot water cylinder. However, as we have a panel heater then it's probably indestructible, unlike the tube ones.

Jonathan

https://www.boards.ie/discussion/comment/122069068#Comment_122069068

Agreed. Part of the bad rep that Solar Thermal got is the "annual service". If you don't have any leaks in the pipe work, and you avoid the system stagnation during the summer, the glycol will last 5 year at least.

Sam W

I am in the exact same situation at the moment. I have 3 solar panels for heating water at the exact centre of my south facing roof.

I’m looking to install solar PV’s but almost everyone I’ve talked to so far has been kinda reluctant to install them without taking the existing panels down, and that would cost an additional 1500 euro for me.

I wonder if this would actually make sense finance wise. The panels were installed in 2018. Still fairly new. I don’t know how much money they are saving me though, but it sounds like a lot of money to take 3 perfectly working panels away.

Would it make more sense to move these 3 panels to the north facing roof instead? They won’t generate as much solar but still better than having none? And does anyone have any idea about the cost of moving it rather than dismantling everything?

graememk

https://www.boards.ie/discussion/2058349633/new-solar-pv-installations-and-removals-of-thermal-solar-pv-s

Merged the threads as they are covering the same topic, Yours had the better title.

What sort of panels are they, are they thermodynamic or just plain Solar thermal?

solar thermal dont really work that well in the shade, but really well in full sun. I wouldnt say moving them to the north face would be the right option.

Id possibly consider a full array PV array on the north face..

could you squeeze any on the right hand side of the thermal panels?

Sam W

Thanks!

I have no idea what the types of panels they are. The house just came with these panels. I doubt if it would be anything more than the cheapest type of panels at the time though, considering the quality of everything else in the house.

Someone will do a site visit in the coming days and we’ll see whether it can actually fit anything to the left and right of the existing panels.

I don’t like the idea of moving anything to the north side either, and a couple of installers have suggested it would be a waste of money. I was just not sure if it’s better than taking them down completely if they cost the similar amount of money, and at least they could generate some hot water, even if it’s just a little bit. That’s better than no hot water at all I guess?

graememk

https://www.boards.ie/discussion/comment/122082430#Comment_122082430

Is there a pump station in the attic?

Sam W

https://www.boards.ie/discussion/comment/122082541#Comment_122082541

I don’t think so. There’s a heat recovery ventilation system in the attic. Don’t think I’ve seen anything else there.

TerraSolis

https://www.boards.ie/discussion/2058349633/new-solar-pv-installations-and-removals-of-thermal-solar-pv-s

Any rogue garden space for a tasteful ground mount? I'd be very reluctant to decommission a happily functioning ST install.

graememk

https://www.boards.ie/discussion/comment/122082644#Comment_122082644

A nice pergola in the back garden 😆

Solar thermal is works so well in the summer, especially 3 panels.

Mine is only one "panel" and if it's sunny out I don't have to boost the DHW in the evening

Sam W

A separate question would be - what is involved in moving the thermal panels? Is this a question for solar PV installers or for plumbers and electricians?

For some reason, based on my conversations with these solar PV installers, it sounds to me that most of them are not interested or not willing to move these panels around.

graememk

https://www.boards.ie/discussion/comment/122082947#Comment_122082947

Plumber job, solar heats glycol, and the glycol heats the DHW.