DIY Install of Solar PV & Thermal panels?

Martyn1981

MFW_ASAP wrote: »

Hi Martyn, I've just noticed your signature. My panel orientation will be WSW and ENE. After discussions with the planners, I'll be allowed 2kw WSW, 1.0 kw ENE and 1.5kw on an almost flat roof (slight incline towards ENE).

I'm assuming that I will require 3x DC Isolator, Invertor, Generation meter, AC Isolator. Is this correct and is this the case with your panels?

Hi. My system is a little messy. The ESE came first, and at the time couldn't find a dual MPPT inverter that could cope with both the higher voltage from the 13 185Wp panels on the main roof, and the lower voltage from the 5 235Wp panels on the lower and shallower roof. So I ended up with 2 inverters, feeding one TGM. I have since found two inverters that tick all the boxes (a Samil and a SMA). So for now, that's two separate systems.

Then the WNW got added a year later [I'm just a tad passionate about PV (no, really I am) but wouldn't normally recommend this, unless done as part of a larger project] and that therefore needed it's own inverter too, and a second TGM for FiT purposes*.

If you're doing all 3 at the same time then I'd suggest MCS/FiT route and use SolarEdge to run everything through PO's (power optimisers) and a single inverter. That'll solve the multiple orientation/array size/pitch and even possibly panel types/sizes issues. Whilst also solving any shading issues, if there are any. Oh, and as you're looking at 4.5kWp of panels, running them all through a single 3.68kW inverter would solve any issues with the DNO, and wouldn't result in any capping (I think) as the orientations and pitches vary.

Otherwise, you'll need 3 MPPT's, and that's a tricky number - some solutions with Stecca inverters, 2kW master plus 2kW slave, both having 2MPPT's each. Or at least 2 inverters, one being a dual MPPT.

Happy to bounce ideas, but unfortunately this is probably where a really good installer's advice is needed.

[Edit - Sorry, quick re-cap, 3 arrays, 3 isolators, 3 inverters, and 2 TGM's.]

Mart.

* Not a requirement, but the tariff drop was very big, and sharing a TGM would have meant generation being apportioned by kWp, not orientation, so as the WNW would underperform the ESE, it would have meant high tariff units being apportioned as lower tariff units. With the tariffs now being similar, not so important.

MFW_ASAP

Martyn1981 wrote: »

Hi. My system is a little messy. The ESE came first, and at the time couldn't find a dual MPPT inverter that could cope with both the higher voltage from the 13 185Wp panels on the main roof, and the lower voltage from the 5 235Wp panels on the lower and shallower roof. So I ended up with 2 inverters, feeding one TGM. I have since found two inverters that tick all the boxes (a Samil and a SMA). So for now, that's two separate systems.

Then the WNW got added a year later [I'm just a tad passionate about PV (no, really I am) but wouldn't normally recommend this, unless done as part of a larger project] and that therefore needed it's own inverter too, and a second TGM for FiT purposes*.

If you're doing all 3 at the same time then I'd suggest MCS/FiT route and use SolarEdge to run everything through PO's (power optimisers) and a single inverter. That'll solve the multiple orientation/array size/pitch and even possibly panel types/sizes issues. Whilst also solving any shading issues, if there are any. Oh, and as you're looking at 4.5kWp of panels, running them all through a single 3.68kW inverter would solve any issues with the DNO, and wouldn't result in any capping (I think) as the orientations and pitches vary.

Otherwise, you'll need 3 MPPT's, and that's a tricky number - some solutions with Stecca inverters, 2kW master plus 2kW slave, both having 2MPPT's each. Or at least 2 inverters, one being a dual MPPT.

Happy to bounce ideas, but unfortunately this is probably where a really good installer's advice is needed.

[Edit - Sorry, quick re-cap, 3 arrays, 3 isolators, 3 inverters, and 2 TGM's.]

Mart.

* Not a requirement, but the tariff drop was very big, and sharing a TGM would have meant generation being apportioned by kWp, not orientation, so as the WNW would underperform the ESE, it would have meant high tariff units being apportioned as lower tariff units. With the tariffs now being similar, not so important.

Cheers for the info Martyn, it's good to have this sort of knowledge even if I go down the MCS route (which I probably will) so that I can cross-question the installer and see if he knows his stuff.

I will be installing the 2kw/1kw panels at the same time (these are on a garage roof that essentially faces East/West). The third set of panels on the separate flattish roof will probably wait because I'm just not sure about fitting PV on there or whether to go with solar thermal (I have a heatbank attached to my woodburner and gas stove that has an unused solar coil).

Martyn1981

MFW_ASAP wrote: »

Cheers for the info Martyn, it's good to have this sort of knowledge even if I go down the MCS route (which I probably will) so that I can cross-question the installer and see if he knows his stuff.

I will be installing the 2kw/1kw panels at the same time (these are on a garage roof that essentially faces East/West). The third set of panels on the separate flattish roof will probably wait because I'm just not sure about fitting PV on there or whether to go with solar thermal (I have a heatbank attached to my woodburner and gas stove that has an unused solar coil).

Morning, been having a thunk!

[Just my ponderings, and I may have gone off on a tangent, so please just take this as my opinion, and a decent installer will know 10 times more.]

Problem, your orientations, if you go down the SolarEdge (SE) route might necessitate working backwards from a possible final decision, rather than two stages. The 2kWp WSW + 1kWp ENE would appear to lend themselves perfectly to the SE 2.2kW inverter **unless the pitches are very shallow, and both systems could be near max around summer midday when the sun is highest.**

But, you couldn't then add anymore panels to that inverter, without serious capping and waste.

If you did all three orientations at the start, then the SE 3.5kW or 3.68kW inverters would be perfect. But if you installed one of these with only the first two orientations, 'just in case' you decided on the 1.5kWp ENE later, then it would underperform if you later opted for solar thermal.

Obviously you have lots of other options, if you just go for the 2 arrays, but given the problems of adding a third array, I think you need to decide 2 or 3 at the start.

The smaller ENE may be an issue as that suggests 4 panels, and that may be a low voltage (on that string) for some dual MPPT inverters, but shop around and see. You could solve this by deliberately choosing panels with higher voltages, say nearer to 50V than 30V, to ensure that smaller string meets both the minimum voltage of the chosen inverter, and the MPPT minimum voltage too.

Last thought, and I don't know much about solar thermal, but is flattish ok for ST? Presumably it would then be a summer specialist, possibly with excess production. But with very little output in the other months, or am I completely misunderstanding it.

What are the pitches on the ENE and WSW rooves? Would it be worth sacrificing some WSW space for the ST instead? These aren't suggestive questions, I genuinely have no idea how ST is best positioned, or your particular needs.

Mart.

rogerblack

mac2008 wrote: »

Short answer, it is probably worth paying the extra for MCS to get the FiT, especially if you can get the higher FiT.

My understanding, after reading all of the relevant legislation I can find, is that while it is legal to connect a small PV generation system without MCS (there are merely safety regs you need to meet) there is no legal basis for them to pay you the export fee if you do not.
I would be very gratified to find out I'm wrong.

Also - local offsetting can be important.
Especially in the case you have a large local baseload of electricity.

mac2008

rogerblack wrote: »

My understanding, after reading all of the relevant legislation I can find, is that while it is legal to connect a small PV generation system without MCS (there are merely safety regs you need to meet) there is no legal basis for them to pay you the export fee if you do not.
I would be very gratified to find out I'm wrong.

Also - local offsetting can be important.
Especially in the case you have a large local baseload of electricity.

hmm - yes, good point. I suppose at the moment the export payment is lumped in withthe FiT, so legal basis or not, it might be logistically very hard!