Adding panels to 10 year old system

[GraemeG]

Hi
I've a 10-year-old grid tied system 3kW. (Inverter also 3kW) I also have a Solar Hot Water. The Solar Hot Water has failed in the pump, it's a 10 YO collector and the collectors are corroded so I'm currently, I am as I write, in fact, replacing the Hot Water Service and this will be powered only by the Grid Tied. I know that my power bill will go up rapidly from today on. (Winter in Australia)

It's a small roof but with the removal of the Water Solar, there will be space to add extra panels to the old system & a new Inverter. (2kW)

Options as I see it:-

-Scrap the current system and install a new 5kW
-Add extra Panels + new inverter.
-A new 2KW system run parallel with the current system.
-Other suggestions.

Regrettably, we've probably only got another 10 years in this house and no longer flush with funds.

I Do have a 1kW DIY Off Grid with failed Lead Acid Batteries. That's a question for another time,

Thanks

 

[Crowz]

That's a tough call.

Adding is simple since your cutting down on the amount of panels needed in theory.

The problem comes in with how far the old panels have degraded. If your going to use them in series then all the panels amp ratings will be at the lowest single panel in the series.

Lets say you have 5 37 volt panels and you want to add 5 37 volt panels all in series. Even if all of the panels are the same model and same brand the amp output on the old panels will be less than the new panels.

So if the new panels show 8 amps and the old panels aged down to 5 amps then new panels will be 5 amps too.

The new panels are rated at 296 watts by those made up figures I used.
The olds on the other hand will only be 185 watts.

So when you mix those old and new panels in series your making the new panels put out a max of 185 watts.

So we have 10 panels that should be making 2960 watts.

But with the degraded ones mixed in your only making 1850 watts

So 10 new panels = 2960 but mixing them = 1850 so your losing 1110 watts because of the age of the old panels.

Not so good. I'd find out how much life is left in the old panels before making a decision if it was me.

I bought a tester off amazon to do that and it works pretty good. I was surprised how bad off some of my old panels were.

 

[Shimmy]

2kW is a bit on the tricky side, but no sense throwing away anything that is working well enough if you don't have a long term plan for the place. Not sure what is available in Australia, but things like the Growatt or EG4 3kW inverters and a small battery pack might be worth the system.

What utility restrictions do you have?

 

[GraemeG]

But I do have an old Off Grid that I installed over time with 1000 w of panels and dead Lead Acid batteries. I used to runn my shed, Laundry & entertainment systems from it. I really made that for fun & education.

Anyway, I'll check out the status of the Panels.

 

[GraemeG]

Just a thought; maybe use Micro Inverters on any new installed panels and add Micro Inverters to the old ones as well? The current string inverter will have to be replaced, anyway. This would mean that I'd get the maximum from each panel & the new one's output won't be dragged down by the older? (No, I haven't checked out the status as crowz suggested as yet.)

 

[Shimmy]

Just a thought; maybe use Micro Inverters on any new installed panels and add Micro Inverters to the old ones as well? The current string inverter will have to be replaced, anyway. This would mean that I'd get the maximum from each panel & the new one's output won't be dragged down by the older? (No, I haven't checked out the status as crowz suggested as yet.)

FWIW, I'd say that micro inverters are only useful to the capacity you can reliably consume (or beneficially export to the utility) during the day-- generally not much. Beyond that a hybrid with batteries makes much better sense

 

[GraemeG]

Thanks Shimmy. I'll reconsider that. The capital cost, although recoverable over time, might not be feasible. Maybe only six years before we need to sell the house. (I was hoping for ten!)