Solar grid tie question

[Djbfinchmaster]

Disclaimer - To many threads to go through so if this a duplicate, I AM SORRY.

My friends setup: 8 X 315W connected to an ABB (dual MPTT) grid tie inverter. This was phase one and hence all the panels was connected on one MPTT (upon advice from electrician). Original plan was 2 strings of 4 panels on each of the 2 MPTTs. Phase 2 would have been another 8 panels on the other MPTT.


Without boring you with the details the calculations, depending on the weather, indicated it should generate somewhere between 250- 350kWh.

Currently is generates about 150kWh. (40% of theoretical max and 60% of what I expected a realistic value would be)

My question: Does the fact that the setup only use 1 of the 2 MPTT's have an effect on the efficiency of the inverter? If not, I am stumped unless one of the panels is a dud.

 

[itareanlnotani]

Any shading? Are the panels facing due north?
Remember, its winter, so output won't be optimal as there are less sun hours in the day

Whats the inverter model?

8 x 315W on 1 MPPT doesn't sound bad, likely 289V assuming you have the standard 36.2V / 8.7A panels
Your inverter won't likely run as well on 4 panels as it would on 8 as the voltage will be too low at times (will need to see your inverter specs to check though, it may have a lower start voltage than I'm guesstimating).

I'd expect an output of roughly 5-7KW a day at the moment in winter with that size setup.

Your inverter should be able to tell you basic facts like voltage and amps, so you can check output. Check at 1pm to see what the values are, as that will be your rough peak for the day at the moment.

 

[Djbfinchmaster]

Thanks for reply.

I initially also blamed the poor silver oak tree in front of the house and now the tree looks like it went to a cheap barber.

It is the std canadian solar 315W panels. Will check the inverter specs, but if I remember correctly the 8 panels on one MPPT was still within spec.

Roof face directly north with a 20degree pitch. Panels mounted flat on roof. (almost ideal setup with minimum installation costs)

Currently, (whether permitting) is generates about 5kW per day, which is ball park what you mentioned, so perhaps my expectation of the setup was a little high to start off with.

Hopefully the summer will ramp up the performance.

 

[thehuman]

wait till summer will improve

 

[Djbfinchmaster]

Spoke to another ABB installer and he advised me to check the minimum input V for inverter to switch on. It was still on default and I re-programmed it to it the lowest allowable value. This was about a month ago and this month the system seemed to generate 10kW more than the previous couple of months.

Now the question is was this due to the settings I changed or due to September being closer to summer and thus more sunlight hours?

 

[itareanlnotani]

Spoke to another ABB installer and he advised me to check the minimum input V for inverter to switch on. It was still on default and I re-programmed it to it the lowest allowable value. This was about a month ago and this month the system seemed to generate 10kW more than the previous couple of months.

Now the question is was this due to the settings I changed or due to September being closer to summer and thus more sunlight hours?

FYI - I did mention that a while ago - "Your inverter won't likely run as well on 4 panels as it would on 8 as the voltage will be too low at times (will need to see your inverter specs to check though, it may have a lower start voltage than I'm guesstimating)."


Probably a mixture of both.

 

[calypso]

Im quite surprised that Enphase's micro inverter solution has not caught on more. Sure costs abit more but you get all the modularity and individual performance of each panel.

 

[Geoff.D]

........
Roof face directly north with a 20degree pitch. Panels mounted flat on roof. (almost ideal setup with minimum installation costs)

What is the latitude at your location and how does that compare with the 20 degree pitch of the roof?

Not suggesting that changing anything here will make a difference, just interested.

 

[itareanlnotani]

Im quite surprised that Enphase's micro inverter solution has not caught on more. Sure costs abit more but you get all the modularity and individual performance of each panel.

Cost, limitations and Reliability are issues.

Enphase also isn't doing so well, not enough sales, as string inverters are far cheaper.
Even their cheaper Chinese competitors are not seeing enough sales.

Limitations - their current products are limited to 250W panels, when industry standard size is mostly 300W+- (305W / 315W / 300W...)
The S300 due in 2017 will *finally* allow for 300W panels. So "individual performance" doesn't really cut it when they don't support typical sizing..

Having several inverters in outdoor conditions that can fail vs one single (point of failure).
Longer term I don't see them being viable, as more people go towards battery storage. When that happens, you'll see more medium DC-DC applications vs DC -> AC -> DC (for storage).

 

[calypso]

Cost, limitations and Reliability are issues.

Enphase also isn't doing so well, not enough sales, as string inverters are far cheaper.
Even their cheaper Chinese competitors are not seeing enough sales.

Limitations - their current products are limited to 250W panels, when industry standard size is mostly 300W+- (305W / 315W / 300W...)
The S300 due in 2017 will *finally* allow for 300W panels. So "individual performance" doesn't really cut it when they don't support typical sizing..

Having several inverters in outdoor conditions that can fail vs one single (point of failure).
Longer term I don't see them being viable, as more people go towards battery storage. When that happens, you'll see more medium DC-DC applications vs DC -> AC -> DC (for storage).

Yeah I agree they not selling well. But with my limited knowledge, seems like a better technical solution. You seen their modular AC batteries?

 

[itareanlnotani]

Yeah I agree they not selling well. But with my limited knowledge, seems like a better technical solution. You seen their modular AC batteries?

Took a quick look, grid tied, AC coupled.

Not really useful for us here for a number of reasons;
Grid tied here is costly. Daily fee's, etc. We also don't have time of day billing yet, so doesn't really make sense from a customer (i.e. consumer perspective).

If we had a smart electricity provider, they would be jumping on stuff like this - its an ideal way to (re)move the evening peak usage, and reduce costs. If they were smart though, they wouldn't have cancelled the successful solar geyer rebates.

Grid tied is also not the future. Localised micro grids with self storage will probably be what eventually happens, as electricity fee's get ever more onerous, and self provision gets cheaper...

 

[Djbfinchmaster]

wait till summer will improve

Nov and Dec generation went up from about 125 KWh to about 225Kwh. I did not expect such a big variation between summer and winter generation. This is also now much closer to my calculations. Surprised and relieved at the same time.

 

[Djbfinchmaster]

Im quite surprised that Enphase's micro inverter solution has not caught on more. Sure costs abit more but you get all the modularity and individual performance of each panel.

I only stabled upon the whore micro inverter setup a month or two after my installation was completed. This would have been a better solution for me than my current setup.

 

[calypso]

I only stabled upon the whore micro inverter setup a month or two after my installation was completed. This would have been a better solution for me than my current setup.

Dunno if Enphase really services SA anyway. Their profitability is also at risk so maybe not a bad move to have avoided. Still seems like an interesting technology though. Some of the premier manufacturers are baking the inverters right into the panel as an option.