Advice on Dual-String Setup

[solar_cat]

Hello

I am looking for advice for a PV system that I recently had installed. It comprises of 8 panels, four orientated south and four orientated west. Our installer led me to believe that this would be configured as a two string system, one for each orientation.

However, what has been installed is a single string system with all eight panels connected in series. I have queried this with the installer who has said that it has been designed and installed correctly, despite this contradicting what was originally specified and every recommendation I can find on the Internet.

I am told that due to “Internal Blocking Diodes” of the panels the westward panels will not block the power production of the southward facing panels, however on sunny days I am seeing virtually no power generation until midday when the sun moves around to hit the west panels and production spikes. Cloudy days produce good generation in the morning.

Any advice anyone can provide will be gratefully received!

Many thanks

 

[binky]

Hello

I am looking for advice for a PV system that I recently had installed. It comprises of 8 panels, four orientated south and four orientated west. Our installer led me to believe that this would be configured as a two string system, one for each orientation.

However, what has been installed is a single string system with all eight panels connected in series. I have queried this with the installer who has said that it has been designed and installed correctly, despite this contradicting what was originally specified and every recommendation I can find on the Internet.

I am told that due to “Internal Blocking Diodes” of the panels the westward panels will not block the power production of the southward facing panels, however on sunny days I am seeing virtually no power generation until midday when the sun moves around to hit the west panels and production spikes. Cloudy days produce good generation in the morning.

Any advice anyone can provide will be gratefully received!

Many thanks

Dreadful design, should have been 2 strings or fitted with optimisers or similar system.

 

[solar_cat]

Thank you. Would optimisers on each panel be the same, better or worse than a dual string inverter (ignoring cost)?

Why would the internal blocking diodes not be sufficient in this configuration?

 

[binky]

Thank you. Would optimisers on each panel be the same, better or worse than a dual string inverter (ignoring cost)?

Why would the internal blocking diodes not be sufficient in this configuration?

Diodes don't block, they bypass. The way they work just isn't very clever, hence the tigo optimisers design. The diodes are also recognised as being the weakest link in a panel, ie the main point of failure, so constantly using them is a bad idea long term, although I've never seen any figures for reduced lifespan. Shading part of any string reduces performance in a very notable way. Google panel shading and you should find some information about that. The only issue with only 4panels per string is will they meet the start up voltage for the inverter? It might be a bit marginal.