For a budget system, and really for most systems, there isn't a compelling reason to use AC coupling at all. Much simpler and more efficient to go the classic DC route: panels to charge controller to battery bank to inverter.
gww1 wrote: »
If you had really heavy daytime loads that stressed your inverter to start and run, would ac coupling be more efficiant and possibly remove stresses from your current systems?
You know like as an add on without adding batteries and such to a system already there.
Yes; it all costs money. You can't drive a Ferrari for the price of a Fiat.
NorthGuy wrote: »
May not be that inefficient. Sunny Boys claim to be 98% efficient, compare to MPPT+Inverter at 85%, so you get much better utilizaton of solar when used directly. When going to batteries, you get (Sunny Boy + Sunny Island) efficuiency at 90%, compared to MPPT at 95%. Depending on the usage pattern, SMA system may turn out to be more efficient.
maskani wrote: »
Hello all, I'm reading all of your post here, they are so useful and I thanks to all. I think Dr. Strenglov said true about sunny webbox, sunny webbox is necessary for programming inverters but after that it can be removed.
So, I have a question, is it possible to replace Sunny Island with a Ups and V/f Controller? I want to setup a not expensive system, with a 350w microinverter, and 200 or 300 watt UPS, maybe I can design a V/f controller, too. SMA is so good, but it's so expensive. we can't find customer with this prices. we must build a system with lower power and not expensive. if we can build this system, we can sell more and more pv system, and expanding usage of renewable energy in the world.
stephendv wrote: »
Yes, the AC coupling is more efficient for direct loads, but for a "budget" system based on year-round use, you'd be looking for the best efficiencies in winter, not summer. Also, a GTI is considerable more expensive than a top of the line MPPT controller.
I threw some numbers together to compare the efficiencies of the two systems.