Knackered solar thermal replace with PV

[roys]

My turn to ask a solar question, more a question of is there such a product available.
Background info.
Rural property, current system is:
solar thermal 2 panel drain back system which feeds one of the coils in my 200L hot water cylinder. Was a good system as it means that in the summer it gave me all my hot water without having to put on log burner.
2nd coil is fed from wood burner when return temp reaches 55deg C rising pump switches on and heats 5 rads till return temp drops to 35deg falling then pump switches off.
Solar PV system 12 panels at 235W each, not much surplus but any surplus I do have goes via a diverter to an electric rad in a cold dark bit of the house.
Solar systems both about 12 years old and PV is on a FIT payment.
Been nursing the solar thermal system along for 3 or 4 years years now but the last good panel out of the two I think has finally died in the recent frost.
Was thinking of doing away with the two solar thermal panels which will give me room for probably 4 pv panels, got to keep this system totally separate from my grid connected fit pv system. My cylinder has a 3 kW immersion element in it so my question is
What “island” (not grid connected) type inverter can I fit that will take the output from my 4 proposed new panels and give me some energy into the 240V 3kW element, guessing at some form of mttp job, but I don’t know what to get, also presuming modern panels are up at the 300 W ish now?
Am I on the right track with my plan?
Cheers Gents

 

[bladerunnerpv]

Hi Roys, just thinking of bits I've see on my internet travels...

You would like this extra PV to be completely off-grid ?
The SMA Sunny Island sticks in my mind, might it be appropriate? Sadly I know as much about them as I see on their website, probably less ;-)
https://www.sma.de/en/products/battery-inverters/sunny-island-44m-60h-80h#c97

Sorry, I'm not familiar with the constraints an existing FiT imposes on additional PV capacity


Immersion:
Suggest you investigate Solar iBoost or an 'Eddi' perhaps, or possibly the SOLiC.

The sunamp heat storage system is intriguing, worth a look perhaps if you're revamping things


Panels: what sort of roof area do you have to play with?
400W is easily achievable per panel, e.g. 1879 x 1045 x 32mm for Qcells G10, many others out there

there are some ~600W panels by Canadian Solar (a chinese co. !) ,

or UKSOL do a 650W panel at 2384 x 1303 x 35mm, and smaller ones too
https://www.uksol.uk/uksol-solar-pv-modules

sometimes more smaller panels gives higher total kWp, depends on the efficiency and spatial arrangement.

going really small there are a couple of roof tile sized systems out there 'shingle' IIRC , so the PV panels are slate-sized, not seen prices tho.

or to throw a curve ball in, does it need to be on the roof, would ground mounting the panels work - probably less installation cost involved if doing so.


hope this helps

 

[binky]

If you want to keep it off grid Victron is the inverter you want. However, there's nothing stopping you using another small Grid tied inverter with export limitation. The various immersion controllers all work with 240V, where as off grid stuff works via battery stack , which is making things unnecessarily complicated.

Panel wise, don't worry about wattage, look at panel efficiency, and find panels that fit your space. Most start at 380W, and you can get 600W, but these panels are huge, difficult to work with, and not more efficient.

 

[BorisJ]

Solar thermal is much more efficient in heating water than solar PV for a given panel area. The reason solar PV is fitted is because it saves all the extra coil pump and plumbing. But you already have that so I would be looking at getting the thermal panels fixed.

 

[roys]

Thanks gents for the replies.
@bladerunnerpv If you look at the pic the two panels in the middle are the solar thermal panels that I am looking to replace with PV so the gap I have to play with will fit 4 standard panels. I do already use an Imerson solar diverter on my current PV system, diverter to an electric heater.
@binky didn't know I would be able to fit another grid tied inverter, that would certainly be the easiest option, so would I just set the export to zero (didn’t know inverters had this option) so that everything goes to a solar diverter and so to the immersion element?
@BorisJ yip I understand solar thermal is more efficient which is why I got it fitted all those years ago and to be fair it has gave me a lot of hot water, however there is a lot more maintenance involved with things like pump bearings leaks and frost issues, and now that the 2nd panel has died I think I will go down the almost fit and forget route.

 

[binky]

Thanks gents for the replies.
@bladerunnerpv If you look at the pic the two panels in the middle are the solar thermal panels that I am looking to replace with PV so the gap I have to play with will fit 4 standard panels. I do already use an Imerson solar diverter on my current PV system, diverter to an electric heater.
@binky didn't know I would be able to fit another grid tied inverter, that would certainly be the easiest option, so would I just set the export to zero (didn’t know inverters had this option) so that everything goes to a solar diverter and so to the immersion element?
@BorisJ yip I understand solar thermal is more efficient which is why I got it fitted all those years ago and to be fair it has gave me a lot of hot water, however there is a lot more maintenance involved with things like pump bearings leaks and frost issues, and know that the 2nd panel has died I think I will go down the almost fit and forget route.View attachment 14632

Got the space to rearrange the existing panels and create space for the new ones.

You fit an amp clamp on your meter tails to control export. That way you can fit as many panels as you can afford. If you want to think longer term, fit a hybrid inverter with a view to installing batteries.

 

[roys]

@binky I’m getting confused so please bear with me. Are you saying my present 12 panel grid tied system just stays as is, which is good as that doesn’t interfere with my FIT payment. I then add my new 4 panels over the old thermal panels in the middle of roof or say 6 panels if I shift my present panels together again over the thermal panels to create room at one side for a new 6 panel array.
Now the bit I’m a bit confused on, I fit a new grid tied inverter and let my present diverter do its stuff and divert to the immersion first and use the diverter 2nd Channel to divert to the room heater. Just concerns me that if the water gets up to temp and the room heater gets up to temp ( which would be rare) that I might exceed my export limit as I would have two separate inverters and that might get messy.

 

[binky]

@binky I’m getting confused so please bear with me. Are you saying my present 12 panel grid tied system just stays as is, which is good as that doesn’t interfere with my FIT payment. I then add my new 4 panels over the old thermal panels in the middle of roof or say 6 panels if I shift my present panels together again over the thermal panels to create room at one side for a new 6 panel array.
Now the bit I’m a bit confused on, I fit a new grid tied inverter and let my present diverter do its stuff and divert to the immersion first and use the diverter 2nd Channel to divert to the room heater. Just concerns me that if the water gets up to temp and the room heater gets up to temp ( which would be rare) that I might exceed my export limit as I would have two separate inverters and that might get messy.

You are allowed to move your existing panels without risking the FIT. That will give you more space for new panels. The extra energy will divert as per your current setup, and if do reach a point whereby you exceed their demands (could always fit Aircon for the summer), the export limitation will reduce the output from the new array, and if necessary shut it down completely, so that you never exceed the DNO limitation.

 

[roys]

Thanks binky but if my water immersion and room heater was up to temp, what is to stop my inverter exporting say 3kW and the new inverter exporting its 4 or 6 panel worth so maybe 1.5kW and so exceeding the limit, I am not seeing how one inverter knows what the other is doing.

 

[binky]

Thanks binky but if my water immersion and room heater was up to temp, what is to stop my inverter exporting say 3kW and the new inverter exporting its 4 or 6 panel worth so maybe 1.5kW and so exceeding the limit, I am not seeing how one inverter knows what the other is doing.

They don't have a clue

Your new inverter can have an amp clamp, same as the immersion control, so you control that one alone, otherwise you would lose some fit money

 

[roys]

Think it might be starting to sink in so:
Get 4 or 6 new panels, rails, clamps, and a grid tied inverter and a ct.
Add my immersion into the diverter making the immersion the primary load?
So this leads onto the next set of questions sorry binky.
Do all inverters have this ct facility to add on?
How would you tie it into the house, fit another small consumer unit and into the Henley’s?
Fit new ct beside existing ct for diverter.
Obviously no meter required.

 

[binky]

Think it might be starting to sink in so:
Get 4 or 6 new panels, rails, clamps, and a grid tied inverter and a ct.

Yep

Add my immersion into the diverter making the immersion the primary load?

Sounds good.

Do all inverters have this ct facility to add on?

I believe so, usually sold as an additional part.

How would you tie it into the house, fit another small consumer unit and into the Henley’s?

I prefer a separate mini board

Fit new ct beside existing ct for diverter.
Obviously no meter required.

Yep, some use a small meter type gadget rather than a ct , which wire into the meter tails. Bit of a pita those, but easy enough to install.

 

[roys]

Cheers Binky
Looks like I will be keeping an eye on my kinda near-by solar wholesaler in the New Year to see what they have going.

 

[binky]

Cheers Binky
Looks like I will be keeping an eye on my kinda near-by solar wholesaler in the New Year to see what they have going.

Most of the electrical wholesalers also supply solar if that's easier for you.

 

[stuboy]

How about sticking the panels directly into a 110v immersion, 4 panels will be around that voltage then you have near zero losses. OK max power point wont be perfect...lol but super cheap and efficient system.

Somin like this:-

https://www.aliexpress.com/item/322...bf!16188270322!sea&curPageLogUid=iBP06aBnd5kn
Stu

 

[binky]

How about sticking the panels directly into a 110v immersion, 4 panels will be around that voltage then you have near zero losses. OK max power point wont be perfect...lol but super cheap and efficient system

If you do that, it can only power the immersion, and not be utilised elsewhere, so lacks any flexibility.

 

[stuboy]

If you do that, it can only power the immersion, and not be utilised elsewhere, so lacks any flexibility.

Its a cheap dirty solution, not necessarily the best ;-) but can be upgraded in the future

 

[johnb2713]

How about sticking the panels directly into a 110v immersion, 4 panels will be around that voltage then you have near zero losses. OK max power point wont be perfect...lol but super cheap and efficient system.



Stu

That is until the tank is up to temperature and then you've got 100% total losses.

 

[binky]

Its a cheap dirty solution, not necessarily the best ;-) but can be upgraded in the future

Not convinced