Hi!
I have a grid-tie system with a Fronius Symo 10.0-3M inverter and 20 times 400W solar panels connected to it in a 10S4P configuration installed on an east-west roof, with 20 panels in each direction.
I'd like to have at least some electricity even when there is a utility power outage. I would like to do this in a way so that i don't have to redesign the existing system to avoid the whole bureaucratic process that i would have to go trough with the utility. My idea is to buy an Axpert VM III 5kW inverter with some batteries, connect one of the four parallel strings to it whenever needed and call it a day. That would be well in the tolerance the manufacturer has given for this inverter, which is <500V on the solar input (actual nameplate Voc would be around 445V, which goes over the 500V limit only at negative 25 degrees Celsius panel temperature, but that does not happen where i live). Power would be 4kW, so that is also under the specified 5kW.
However, there are days when it is overcast and not even the 4 strings combined generate enough energy for my needs, so i figured i could connect in parallel at least a second string facing the other way. My experience is that the system caps at around 0.7 times it's peak nameplate power in the most favorable conditions, and even that lasts only for an hour a day, so i would be a little bit over the 5kW cap at 5.6kW for a short time. Would this damage the inverter or would it just "waste" the extra power operating outside of the maximum power point?
Even better, could in some way all four of the strings connected? Is there some kind of device that i could insert between the 4P array and the inverter that would effectively limit the solar input to safe levels?
Maybe a separate BMS / charging system that also monitors the load and always supplies the current needed to charge the battery at a safe current and serve the load, completely bypassing the Axpert inverter for handling the solar input?
Thanks!
(Ps. i'm a certified electrician, I'm somewhat convinced that i can do this without electrocuting myself or setting the house on fire.)
I have a grid-tie system with a Fronius Symo 10.0-3M inverter and 20 times 400W solar panels connected to it in a 10S4P configuration installed on an east-west roof, with 20 panels in each direction.
I'd like to have at least some electricity even when there is a utility power outage. I would like to do this in a way so that i don't have to redesign the existing system to avoid the whole bureaucratic process that i would have to go trough with the utility. My idea is to buy an Axpert VM III 5kW inverter with some batteries, connect one of the four parallel strings to it whenever needed and call it a day. That would be well in the tolerance the manufacturer has given for this inverter, which is <500V on the solar input (actual nameplate Voc would be around 445V, which goes over the 500V limit only at negative 25 degrees Celsius panel temperature, but that does not happen where i live). Power would be 4kW, so that is also under the specified 5kW.
However, there are days when it is overcast and not even the 4 strings combined generate enough energy for my needs, so i figured i could connect in parallel at least a second string facing the other way. My experience is that the system caps at around 0.7 times it's peak nameplate power in the most favorable conditions, and even that lasts only for an hour a day, so i would be a little bit over the 5kW cap at 5.6kW for a short time. Would this damage the inverter or would it just "waste" the extra power operating outside of the maximum power point?
Even better, could in some way all four of the strings connected? Is there some kind of device that i could insert between the 4P array and the inverter that would effectively limit the solar input to safe levels?
Maybe a separate BMS / charging system that also monitors the load and always supplies the current needed to charge the battery at a safe current and serve the load, completely bypassing the Axpert inverter for handling the solar input?
Thanks!
(Ps. i'm a certified electrician, I'm somewhat convinced that i can do this without electrocuting myself or setting the house on fire.)
