Solar install - advice needed

[Ian]

Hi everyone.

 

New to the board, but hope to have lots of positive interaction:)

 

I was wondering whether anyone on the board would like to engage in a conversation about my setup, and the choices I face.

 

Here's some background: we own a largish house & grounds in Noordhoek.  I've refitted with LED lighting, gas cooking and EVT water panels for the 2 geysers over the years, and we currently have daily consumption of 60kWh, or 1800kWh pm.  We have a prepaid three phase supply, although its just the borehole and irrigation pumps that are 3ph parts.

 

I had been eyeing a PV setup for some time, waiting for the pricing and admin setup to make sense. Earlier this year I was able to get 10 Renesola 300W panels @ R6/w and decided to pull the trigger. I have 42m^2 flat roof available for convenient panel installation, any more will be much trickier.  I decided to go the grid-tie route, as we have adjusted to the load shedding without too much disruption.  After looking at what was available locally, and the pricing, I imported a German Platinum 7000 R3-MDX 3phase GT inverter, for significantly less than the local pricing.  I chose a bigger unit than what was required as I saw myself adding extra PV at a later stage, as well as moving to the SSEG tariff.  I installed the panels on a self-made aly tube frame, with everything riveted together with SS rivets.  The easy part, and so far withstood several NW storms.

 

However, one of the 'features' of the inverter I had overlooked was that it requires 2 identical strings to operate (part of some switching circuitry before the MPPT for higher efficiency at low voltages). This gives the inverter 98% euro efficiency over the whole MPPT range.  But the MPPT voltage range is 350V to 720V, much higher than my 2x1.5kW of strings can produce. I have contacted the manufacturer, and confirmed that I'm stuck.

 

I now have 2 choices:

 

1) Keep the inverter and get more panels (essentially another 3kW), along with the mounting complications. Then arrange SSEG changeover, as the 6kW will definitely result in some feed-in and my meter complaining...  The inverter isn't on the COCT list, not sure what that implies, as it's supplied locally.

 

2) Get another inverter.  This is where I'm headed at the moment.  In the interim, we've also bought a smallholding near Tessellaarsdal, where we plan to build an off-grid retirement home, ready in ~3 years.  I'd like to migrate the installation there before we sell up here in Noordhoek, and foresee a 6kW capacity requirement.  So, option 2 now becomes:

 

2a) Get a Fronius 3ph 3.7kW GT inverter.  Approved by COCT, so SSEG no issue. Can't take it with me to the farm.

2b) Get a Infini 3kW+.  Batteries can help with load-shedding. But DB wiring will have to be modified. Can move to farm, but will have to be supplemented, which might be tricky.

2c) Get a Infini 10kW. will cover both bases, but pricey:(  Also overkill for farm.

2d) Get a hybrid, non GT inverter.  What would you guys recommend?

 

Sorry for the wall of text, but it helps to explain my dilemma. Any suggestions appreciated:)

 

Cheers

Ian

[superdiy]

Welcome to the forum.

 

I quickly scanned through the manual and could not find anything that indicates that you HAVE TO connect to strings of panels. They do however mention that the 2 strings must be identical in configuration, which makes sense since the unit has only 1 MPPT and not 2. I can understand that they maybe designed something which might work well with two similar strings, but in real life situations anything could happen to either one of the strings (e.g. partial shading etc.) which would put them out of balance and in such a case the inverter should still be able to perform.

 

Have you tested the inverter with 1 string only?

[Ian]

Hi Superdiy

 

Unfortunately I never picked it up either - and both the German and local agents were unaware of the issue when I raised it. However, when I got back to the manufacturer, they confirmed the requirement. Any yes, I tried single string - and even got 2 extra panels to up the voltage to >500V, no dice.  I'll probably pop the casing off, and have a look at the circuitry to try understand what they're doing.

Cheers

Ian

[superdiy]

Hi Superdiy

 

Unfortunately I never picked it up either - and both the German and local agents were unaware of the issue when I raised it. However, when I got back to the manufacturer, they confirmed the requirement. Any yes, I tried single string - and even got 2 extra panels to up the voltage to >500V, no dice.  I'll probably pop the casing off, and have a look at the circuitry to try understand what they're doing.

Cheers

Ian

 

What if you bridge the two string inputs, maybe not directly but through two schottky diodes to fool the inverter?

[Ian]

Worth a try...thanks for the suggestion!

Ian

[Wetkit]

Hi Ian,

 

Regarding the SSEG and your invertor, I have tried and failed miserably!!!

If your invertor is NOT on the City of Cape Town list, you are sunk

If you outside the CoC limits, then no problem Go figure?

 

Just to get my stuff strait, you looking to move the complete install over to the new house?

If I read the CoC documentation correct, you have to apply to the CoC once a SSEG is approved, to make any changes or to dismantle it afterwards.

 

By the way, you using a lot of power! Do you know which device is the culprit?

Perhaps just putting the 2 pumps on solar and running them at diffrent times could bring your initial install cost down?

[HyperCut]

Hi everyone.

 

New to the board, but hope to have lots of positive interaction:)

 

I was wondering whether anyone on the board would like to engage in a conversation about my setup, and the choices I face.

 

Here's some background: we own a largish house & grounds in Noordhoek.  I've refitted with LED lighting, gas cooking and EVT water panels for the 2 geysers over the years, and we currently have daily consumption of 60kWh, or 1800kWh pm.  We have a prepaid three phase supply, although its just the borehole and irrigation pumps that are 3ph parts.

 

I had been eyeing a PV setup for some time, waiting for the pricing and admin setup to make sense. Earlier this year I was able to get 10 Renesola 300W panels @ R6/w and decided to pull the trigger. I have 42m^2 flat roof available for convenient panel installation, any more will be much trickier.  I decided to go the grid-tie route, as we have adjusted to the load shedding without too much disruption.  After looking at what was available locally, and the pricing, I imported a German Platinum 7000 R3-MDX 3phase GT inverter, for significantly less than the local pricing.  I chose a bigger unit than what was required as I saw myself adding extra PV at a later stage, as well as moving to the SSEG tariff.  I installed the panels on a self-made aly tube frame, with everything riveted together with SS rivets.  The easy part, and so far withstood several NW storms.

 

However, one of the 'features' of the inverter I had overlooked was that it requires 2 identical strings to operate (part of some switching circuitry before the MPPT for higher efficiency at low voltages). This gives the inverter 98% euro efficiency over the whole MPPT range.  But the MPPT voltage range is 350V to 720V, much higher than my 2x1.5kW of strings can produce. I have contacted the manufacturer, and confirmed that I'm stuck.

 

I now have 2 choices:

 

1) Keep the inverter and get more panels (essentially another 3kW), along with the mounting complications. Then arrange SSEG changeover, as the 6kW will definitely result in some feed-in and my meter complaining...  The inverter isn't on the COCT list, not sure what that implies, as it's supplied locally.

 

2) Get another inverter.  This is where I'm headed at the moment.  In the interim, we've also bought a smallholding near Tessellaarsdal, where we plan to build an off-grid retirement home, ready in ~3 years.  I'd like to migrate the installation there before we sell up here in Noordhoek, and foresee a 6kW capacity requirement.  So, option 2 now becomes:

 

2a) Get a Fronius 3ph 3.7kW GT inverter.  Approved by COCT, so SSEG no issue. Can't take it with me to the farm.

2b) Get a Infini 3kW+.  Batteries can help with load-shedding. But DB wiring will have to be modified. Can move to farm, but will have to be supplemented, which might be tricky.

2c) Get a Infini 10kW. will cover both bases, but pricey:(  Also overkill for farm.

2d) Get a hybrid, non GT inverter.  What would you guys recommend?

 

Sorry for the wall of text, but it helps to explain my dilemma. Any suggestions appreciated:)

 

Cheers

Ian

Could you source more of those panels @ that price ?

Looking for 10 or 12 of them.

[Igubu]

@Ian,

 

Welcome!

 

How about getting a "limiter" so that you can avoid feeding back? I haven't looked at the model manual yet, so not sure if it's possible to disable feedback to grid? (For the excess)

 

From the bit of investigation I've done SSEG in Cape Town is a headache. So any workaround to avoid it, especially if you are planning to move in a year or three will be easier than to go through all that paperwork.

 

With regards to the options listed - why not try and get rid of the German Platinum 7000 and go for something like the Infinisolar 10Kv - 3-phase? (Last I looked on the internet around R45K) - if is fully programmable and you can disable feedback to grid, so your problem will be solved with regards to SSEG. You also have 2x MPPT inputs so if you want to add more panels to the 2nd MPPTtracker?

 

Just as a thought on "overkill for the farm"  on the Inifi 10kWh -  perhaps it might assist to "future proof"  a little? I see you mention an off-grid retirement house  - and from experience unless you are going to invest in new LifeP04 battery banks (at this point pricey - but who knows in 2 years time) - you will struggle to run off batteries (AGM/Gel type) and be able to charge them fully AND cycle/use them - with only 3kWh of panels. You will need at least the 6kWh of PV to be able to run/cycle off say a 500ah bank (I'm using 2x banks of say 4x 250Ah - Total = 8 batteries) and being able to charge them up again during sunshine.

 

One of the mayor advantages I see in going LifePO4 in future is that you can charge them up very quickly compared to AGM/Gel type - regardless of all the other advantages - so on a day when the sun in not perfect, but you might have 2 hours of great sunshine with lots of excess you will be able to recharge fully - which simply isn't possible with agm/gel type batteries.. but that is looking into the future

 

There are some local guys already with the new tech - think it was mentioned before on the forum - but google around for " freedomwon" = still early days I think and nobody here has reviewed them yet - but might be worth a look in future.

 

I'm sure you know them already - but here the link: http://www.voltronicpower.com/oCart2/index.php?route=product/product&path=24&product_id=141

 

There are number of local re-sellers.

 

With regards to the 60kWh per day - I would imagine that was over the winter months with some underfloor heating? (A colleague ran 120kWh/day with his floors on!) - in summer that might come down  to around 40? - it does affect the sizing of PV a lot - I also installed in winter - but over a full year the it all levels out

 

Hope it helps!

 

Butha