Roof Shade - Would you Change from EG4 6.5kW Off-Grid Inverters to Growatt 5kW Stackable Off-Grid Inverters + Power Optimizers?

[nedkelly]

Hi all:

After tree trimming I'm still getting some shade across my only roof location for installing my solar modules. Amount of shade comes and goes as the sun moves but always some amount.

I thought I could install modules with power optimizers to limit issues with shade on one or multiple modules so as not to limit the whole module series but I was told by Signature Solar that optimizers can't be used with the EG4 6.5kW 6500EX-48 (which I have pre-orderd 2 units already).

Would you change inverters to the Growatt stackable inverters and use power optimizers which will likely add another $2500+ to my cost.

Both roof areas already point East & West and with varying shade I want to maximize my available output but just didn't realize not all inverters will work with power optimizers.

Appreciate any advice and input.

Attached is my planned roof module layout.

Regards, Scott

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[tomy2]

I did not know that about the EG4 inverters? I assume there is no place to put a ground mount facing south. I am trimming a mulberry tree today that is partially shading my panels in the afternoon. Mulberry's and a lot of trees can be cut down to 8 feet, and they grow back fast. you might consider removing a tree to the south. I took out a big one that was too close to my house anyway. where are you located?

 

[x98myers7]

first off.... from a compliance perspective, I cannot recommend any all-in-one (aio) component that does not have AFCI built in for any roof install. residential roof installations in the USA require AFCI which cannot be solved for as a standalone-solution. if you aren't sure what that means, I suggest you start with the FAQs in my signature. EG4 and Growatt AiOs do not have AFCI built in.

aside from that... the real solution to your problem is to cut the trees down. seriously. or at the very least trim them back significantly.

 

[JCSchwarb]

first off.... from a compliance perspective, I cannot recommend any all-in-one (aio) component that does not have AFCI built in for any roof install. residential roof installations in the USA require AFCI which cannot be solved for as a standalone-solution. if you aren't sure what that means, I suggest you start with the FAQs in my signature. EG4 and Growatt AiOs do not have AFCI built in.

aside from that... the real solution to your problem is to cut the trees down. seriously. or at the very least trim them back significantly.

Agreed! We did hard pruning on our oaks and went from 80-90% shade to near 100% unobstructed. We now have full battery recharging by late morning while before our batteries would never fully charge. If you have a lot of shade combining two strings into parallel will boost production by up to 3-4x over individual strings. I kept inverter no. 5 with two strings of 7 330w panels and they routinely outperform single strings input to inverter 6, particularly when light levels are low or marginal. I would not recommend adding additional equipment to the AIO or PV array.

 

[RCinFLA]

You will likely be disappointed by DC optimizers. They work best with a coordinated central inverter linked together for interactive control like SolarEdge system.

On uncoordinated systems, the main MPPT controller and DC optimizers can interact causing neither to achieve optimum MPPT point. They just interfere with each other's MPPT search. Usually, the DC optimizers are purposely slowed down in their MPPT search to minimize their negative effect on main MPPT controller. If shading is caused by tree limbs with leaves blowing in the breeze it can cause the system to bounce around, never finding a stable MPPT point.

DC optimizers just try to maximize DC current from a shade compromised panel so it better matches current of unshaded panels. Voltage contribution to the series stack of panels will drop to accomplish similar panel current contribution. This only works when shading is not severe enough to cause bypass diodes in panel to conduct. Once any bypass diode in panel conducts due to severe shading, the DC optimizer does no good.

You need to be sure you have enough panel voltage overhead to MPPT controller to afford the array voltage drop during the partial shading.

 

[nedkelly]

Agreed! We did hard pruning on our oaks and went from 80-90% shade to near 100% unobstructed. We now have full battery recharging by late morning while before our batteries would never fully charge. If you have a lot of shade combining two strings into parallel will boost production by up to 3-4x over individual strings. I kept inverter no. 5 with two strings of 7 330w panels and they routinely outperform single strings input to inverter 6, particularly when light levels are low or marginal. I would not recommend adding additional equipment to the AIO or PV array.

Thanks for the input. I've got 28 modules over 4 strings so a hard pruning is my likely route.

 

[nedkelly]

You will likely be disappointed by DC optimizers. They work best with a coordinated central inverter linked together for interactive control like SolarEdge system.

On uncoordinated systems, the main MPPT controller and DC optimizers can interact causing neither to achieve optimum MPPT point. They just interfere with each other's MPPT search. Usually, the DC optimizers are purposely slowed down in their MPPT search to minimize their negative effect on main MPPT controller. If shading is caused by tree limbs with leaves blowing in the breeze it can cause the system to bounce around, never finding a stable MPPT point.

DC optimizers just try to maximize DC current from a shade compromised panel so it better matches current of unshaded panels. Voltage contribution to the series stack of panels will drop to accomplish similar panel current contribution. This only works when shading is not severe enough to cause bypass diodes in panel to conduct. Once any bypass diode in panel conducts due to severe shading, the DC optimizer does no good.

You need to be sure you have enough panel voltage overhead to MPPT controller to afford the array voltage drop during the partial shading.

Thanks. Appreciate the feedback. Helps me feel better about my situation.

 

[JCSchwarb]

Thanks for the input. I've got 28 modules over 4 strings so a hard pruning is my likely route.

This shows the light levels right now at 9:50am. Before the array was mostly in shadows all day.

 

[Calsun]

Modern panels have bypass diodes so at most a third of the panel's output is lost with partial shading. If the entire roof where the panels are planned to be is in shade for hours at a time then I would consider ground mount racks for the panels. Many grid tie inverters have two to four MPPT controllers and so one can divide up the panels to minimize loss overall from the shading of one section of panels.

With multiple MPPT controllers one can have panels on different roof areas where sun exposure can vary a good deal and have the inverter able to manage the different voltage levels from each group of panels.