augment solar (E & W), parts advice please. 20 July 2021 at 8:39PM in Green & ethical MoneySaving 15 replies 231 views

Heedtheadvice

This might be a big ask so links to any advisory websites would be most welcome as well as any detailed info.

Apologies for large text (if it ends up like I see it!), tablet seems to have a mind of it's own tonight!!

Currently have 4kWp south facing.

Can anyone (or everyone!) give any info on adding small(ish) East and West panels (maybe 300W to  600W each) plus additional  inverter(s) for the two new strings.

I could do with advice on system parts to configure together (such as panel and string configuration, suppliers costs (from mountings through to inverters)

Please note I can probably only mount 2 panels E&W each and it will only augment generation early and late in the day (seasonally) so no issue with over generation, it will be totally separate to the MCS certified system so needs to be as economical as possible.

Could be that switching between strings depending upon generation levels can be accommodated or an automated system used. That might need to be external to the inverter(s) owing to attempt to optimise where shading occurs.

Any ideas?

QrizB

Legally, it needs to be installed by a MCS-qualified person and notified to the DNO*. This does restrict your DIY options considerably.

With that out of the way, have a look at eg. https://www.bimblesolar.com/ (other retailers are available) who can sell you pretty much everything you'll need. Even if you don't buy from them, 30 minutes spent looking around their website will give you a good idea of what's available and example costs.

* You definitely won't find 1kWp of second-hand panels on a home-made ground mount in my back garden. And if you did it would be off-grid and connected to my shed.

Exiled_Tyke

I added two 300W panels to face East and catch some early morning sun when I also added my battery.  These feed into one 500W micro-inverter as being the most economical installation. 

Heedtheadvice

Thanks both. Will investigate.

However QrizB, are you not confusing MCS requirements for certification for FIT/Export and approval by the grid network controllers to install generation on their system? The DNO (the National grid Distributed Network Operator) requires that G83 approval is required for connection, part one for domestic low power up to 16Amps i.e up to 3.68kW for a single generator, part two for multiple generators (still 3.68 kW max) and part three for up to 50kW.

That MCS accredited installer normally employed for an installation deals with both MCS and DNO aspects. If you DIY then you ought to comply with the latters requirement for approval of the design, drawings, forms etc.

Nevertheless an "off grid shed" would not need that latter DNO approval! .......

QrizB

You're probably right re. MCS vs. G98 (G83 has been superseded). Part P is still an obstacle to legal DIY. (And I have to note that the forum rules state "Do not promote, encourage or glamorise any illegal activities", so I'm trying very hard not to appear to encourage you.)

You're also right, an off-grid shed avoids a lot of these issues.

Heedtheadvice

Yes I think I got the reference mixed up thanks.

That Bimble site is worth a look and prices seem good, thanks.

You are right to consider the forum rules. Many do not and advise illegal things especially where regulation apply, safety is critical and DIY work is involved!

For anybody else reading this: As far as I am currently aware part P of the Building regs only applies to England and Wales, Scottish regs similar but different, (not sure about NI or other areas!). Irrespective of that electrical work must be carried out by someone deemed competent -not just someone who thinks they are- for the work undertaken.

Solarchaser

So if you were in Scotland like I am, and have already 4kw mcs solar.
You may decide to put 6.6kw on your garage roof to power your garage...
And be able to do so for under £2.5k making your own brackets and rails.

You may also decide that since you live in a place with over a thousand houses within a mile squared and only half a dozen of those having solar, that there was no risk to the grid.
You may also set your inverters to trip off at a lower grid voltage and be safe in the knowledge that if the grid was in danger of overvoltage that all inverters on your property would shut down before the grid would.

If you wanted piece of mind you would perhaps ask a electrician to use his fancy meter to test the entire house (and garage) and be reassured that all is OK.

Though on the "competent" person, you may find that the Scottish wording is more wooly about competency than you might expect.

But you certainly wouldn't run this way for the last 2 plus years, as that could be illegal in theory.

Not that I've ever heard of anyone charged for supplying too much free solar energy back to the grid.

Heedtheadvice

Thanks for that further post Solarchaser. (I'll be further South than you with less dense housing but still a small percentage with PV gen....a big opportunity wasted!!)

"Wooly" is certainly a good description of Competency in the Building regs (last time I looked) but there are other requirements such as Wiring Regs etc that put some meat under the sheeps wool! Those apply UK wide and certainly the DNO requirements are quite specific as regards micro generation. [ EDIT: Not sure about applicability accross whole of UK, certainly NI has different standard for DNO connection requirements and possibly BRs too!]

Am I a bit out of date though? Could you  further info regarding

" But you certainly wouldn't run this way for the last 2 plus years, as that could be illegal in theory."

I have no wish to go into this ignorent of what is required!!

With regards to inverter grid connection I thought (danger warning!!) that all approved grid tie inverters had the under and over voltage safety switching built in to their design and type approved for connection. Certainly my current one does. Can you enlighten further?

Solarchaser

Most inverters do indeed have under and over voltage protection,  and usually you can modify it by searching model number and service manual to set limits that you want to set.

If I said I had friend who had run for over 2 years with no issues, including at times exporting 9kw would that clear your query?

You may ask yourself  how would the dno ever know I was exporting 2kw when they are supplying 2000kw...

Heedtheadvice

Thanks again.

We have diverged from what I was really asking by discussing export levels and DNO requirements. I have no problems in that area one can add on in an uncontrolled manner or keep the DNO in the loop.

My question really is about the equipment to do the generation and control it. Such as having several individual panels (or maybe pairs) each with the small inverters or, I believe, there is a system to switch panels to an inverter....though I forget what that type of system is called! Is it more economic to go for a bigger higher efficiency panel type or two lower output less efficient panels? What are the best types currently? Where can I buy the bits at best cost for small numbers, not being wholsale quantities and even then maybe only four panels so deliver cost could be a big consideration?? Are second hand panels worth it, a much reduced cost?, ...cable, connectors, inverters, switches etc.

Qrizb has given me one useful link and mentioned second hand panels. Exiled_Tyke has writ that a microinverter was most economical for him/her.

Just reall trying to find good data to put together a system in a money saving method ....and help with generation for any I do not use!

Solarchaser

I understand your question, but the answer is really for you to decide.

You need to work out your power requirements/ goals.

Then you need to work out how much space you have for panels.
Low space means you will need higher power panels.
Lots of space and perhaps older low wattage panels will have what you need.

When you have worked out your wattage, then you can look for inverters that meet your requirements. 

If its low power then microinverters will do between a couple of panels, but if its high power then microinverters will end up much more costly than a string inverter.

For my friend, ebay was the answer.
Cable, connectors,  isolators, panels all new, and second hand inverters