Hi Guys, 

So the time is getting closer. 

I have a 8kw Sunsynk. Currently running a single string with 12 330w old style panels. So 3900w. 

47V - 18.76 - No Clipping, not massively efficient either being old panels. But will keep them for now.

These are setup for summer at 11 degrees currently north facing.

On the 2nd string I am looking to try and maximise what the system can produce on that string. 

I presume that means with the 22a limit I will probably be clipping a bit during peak. 

Essentially, to maximise that 5kw available Mppt. 

So not sure yet ongoing series or parallel based on panels. 

I have been leaning towards Bifacials. I have a unique area available that is elevated with roughly 1m\2m below the panels and enough space to allow extra light in to try and maximise light for earlier mornings, later afternoons and cloudy \ rainy days.

Yes, I have enough space for the larger panels.

These will be setup for a 30degree tilt north facing.

I know 370v is the ideal sort of range to be in on the panels. Not sure though what happens when it's lower like say 200v ? Not as efficient in lower light ?

The two panels I was looking at were.

Longi 545w Bifacial - 49.65 Voc 13.85amps

Series would be x7 panels would be 347v 13.85amps = Max 3 815W

Parallel x8 panels 198.6v amps 27.7 = 4 360W - Essentially i could loose 20%efficiency from clipping at peak. So may only see 3488 in perfect conditions Max ? 

But should do well in non-optimal times if I have this all correct.... ?

 

JA640W Deep Blue 4.0 BiFacial.

These aren't here yet but sounds like they are coming in 3/4months time.

52.87V - 15.31A

Series Max  - 7Panels = 370.09V --- The sweet spot apparently ? 4480W 

Parallel 30.62Amps - 8Panels - I could loose 28% efficiency from clipping so Max 3 686W ?

 

I was wondering with the efficiency and clipping. If you lose say 20 / 28% at peak. Is that how much you could expect to gain at off peak. E.g it would do more with less light due to the larger "oversizing" 

So on a normal day instead of a rough peak of call it 4400w at 12:00-13:00 say. Roughly 14kw as well from 10:30-14:30 overall.

With clipping you may get 3600w at say 10:30-14:30 (14.4kw estimate potential) but then have max for that time.

 

1. Objectives of the panel expansion. Be off Grid as much has possible to lower the bill further. Currently using call it 5/10kw daily still from the grid.

2. Cater for poorer weather. Although do have panels in parallel already for that. 

3. Possibly help with the future of charging a small Electric car during the day additionally. (Like a Mini that only has a 28kw usable battery)

4. With the Ja Panels not being in country yet... is it worth the wait. I can wait the 3/4months. they are more efficient panels with the latest tech. Logi will probably be cheaper as they are available currently. Deep Blue 4.0 do claim to get up to 26% efficiency.....

I also know that charging the Lithium battery's of which I have 4x currently exceeding 60amps is not recommended so as to keep their lifespan running well. But the car could accept the quick charge... 

 

 

 

 

 

 

Maybe I need to simplify the question. 

8kva Sunsynk. Single string Max panels ?

Looking at 640 / 650w Bi Facials if available. 

Basically. Any recommendations between 7 panels in series giving 

4480 w in Series

or 

5120w for 8 in parallel. With parallel do you get the true 8x640w ?  - Or only half the power but better at handling poor conditions ?  (2 560w ? )

What do you actually get out of parallel panels ? 

 

On 2024/09/17 at 1:55 PM, Dry_Reef said:

I presume that means with the 22a limit I will probably be clipping a bit during peak. 

Ok, people time to address this nonsense, clipping is something that occurs on a power output device, like an audio amplifier, when it is being driven beyond its power specifications, the voltage required for the setting is more than the amplifier has available to it and thus you get clipping, where the voltage is hard limited and distortion with lots of horrible higher frequency harmonics come out of the amp. This is likely to heat up the voice coil of your high frequency drivers (tweeters) and if you're lucky, smelt the voice coil open circuit, if you're unlucky, deform the voice coil for permanent reminder of your misdeed.

As for current limiting, which is what is being referred to here, this is what the DC input of the MPPT will do, when its power/design limits are being met, it should/will not allow more current to flow, than what is designed for, this may be less than the power specified, if the Voltage from the panels is lower than a certain amount, since the MPPT has no control over the Voltage, it can only allow or limit the current flowing into the system.

As for you 8kW inverter, price performance wise, I'd say, consider some Jinko 555W/560W/575W panels at around R 1600 to R 1750 each, last I checked best W/ZAR ratio, do your own homework, though and maybe consider 10 panels, 5Series to ENE in parallel with 5Series to WNW, this should give you early morning some juice and late afternoon to augment your north facing panels.

I have found series connected perform better in poor weather but if you having shading problems then you will benefit from parallel setup but with parallel mean  high amps so PV cable must not be to long or to thin or losses going to be big .  

Thanks for the responses guys. 

So final question then. 

So presumably 7 panels in series although potential very good.

Simply being that if I had to go for 2x sets of 5panels eg 10 in total. As there are 10 panels they would operate best to achieve best low light (cloudy). Simply more surface area... 

Is it better to be aiming for 52v x 7 panels = 367v (Close to 370v being ideal)

or 

5x 52v = 260v (not close too 370v) not ideal but due to more panels better in low light anyway ? 

 

 

 

3 hours ago, Dry_Reef said:

So presumably 7 panels in series although potential very good.

Yes, although, I'd say, stick with 6, lets not push the Voltage limits too much. The idea with the 5 + 5 would be the Voltage is in a reasonable range and you'd be overpanelling to a degree to allow more power on cloudy days, the Voltage is likely to be reached even on cloudy days, but the current will be severely limited due to the limited energy coming through the clouds...

See Voltage and Current graphs for yesterday and today for here... Voltage there with loads of clouds, but current not so much... as for today so far, not much clouds...