OffGridForGood
Catch, make or grow everything you can.
I am looking for some input: Feel free to make suggestions or point out my errors.
I am planning a new barn for the property, this could also supply a suitable new area for some new PV to mount.
For now, I am looking at 16 more 440 CS panels (like the ones I already have), and combined would supply another 7kW of collection.
My current set up uses MPP 6048 Inverters x2, a 53kWh LiFePO4 ESS (16S), and I have 22 PV panels on tilting racks.
The 22 PV are in four arrays of 2S-2P x1, and 2S-3P x3; and run to the four MPP inputs on the two MPP6048 inverters, with no spares left for a new PV array.
I do not back-feed to the utility, and don't want to/can't without changing my complete set up due to regulations.
The ESS is being expanded by 28kWh per year for the next two years, and by the time the Barn is built and new PV added on it, my ESS will be about 110kWh.
The ideal location for the Barn is 75 meters (250-feet) from the current shop solar set up, adding for the cable length needed to reach the roof area and up into the shop, let's call the total cable length 85m/280 feet. This is pretty far, and makes me think about cable sizes/cost/line-losses. Keep in mind, in my area -30C/-22F is our low winter temp and the barn will not have any heated space planned. (ie I am not thinking about an inverter in the Barn, at least not yet thinking about an inverter in the Barn).
One option would be to buy a third MPP 6048, and run parallel cables to the two additional MPP inputs, each using 2S-4P , some clipping would be expected at peak solar, and each cable would need to be sized for 40A/ 100vdc (likely requires 1AWG-1/0 cable x2 runs). The third MPP can parallel to the first two, increasing AC-output capacity, maintain comms, become a possible back up inverter to one of the first two if tragedy occured. Higher standby loss is one down-side, although this additional inverter could be set solely as a SCC and not output AC generally.
Another option is use a dedicated SCC capable of high voltage DC, connected to the battery bank separate from the existing inverters, using 8S-2P this would result in about 360-400vdc/ 17-20A range, a single cable would be possible, (likely requires 8AWG x1 run). ESS monitoring could become an issue, require additional equipment.
I have no experience with micro inverters, however I understand they would convert the DC to AC at the Barn, allowing the transmission to the shop via AC instead of DC I suspect this power then could feed the AC input on the inverters as an alternate to the grid/generator input. I am not sure if this is correct or not. If I imagine the Barn PV converted to 240vAC the resulting peak output is 240vAC / 30A requiring a cable 6AWG. If this power passes through the inverters to the ESS the current system will keep track of battery SOC as it does now.
120/240 AC available at the Barn will be required, and if this could be done locally rather than running DC to the shop, and AC back again x 280 feet would save some expense and add efficiency.
Maybe there are other options I have not considered?
I would be interested in your thoughts/experience/input.
I am planning a new barn for the property, this could also supply a suitable new area for some new PV to mount.
For now, I am looking at 16 more 440 CS panels (like the ones I already have), and combined would supply another 7kW of collection.
My current set up uses MPP 6048 Inverters x2, a 53kWh LiFePO4 ESS (16S), and I have 22 PV panels on tilting racks.
The 22 PV are in four arrays of 2S-2P x1, and 2S-3P x3; and run to the four MPP inputs on the two MPP6048 inverters, with no spares left for a new PV array.
I do not back-feed to the utility, and don't want to/can't without changing my complete set up due to regulations.
The ESS is being expanded by 28kWh per year for the next two years, and by the time the Barn is built and new PV added on it, my ESS will be about 110kWh.
The ideal location for the Barn is 75 meters (250-feet) from the current shop solar set up, adding for the cable length needed to reach the roof area and up into the shop, let's call the total cable length 85m/280 feet. This is pretty far, and makes me think about cable sizes/cost/line-losses. Keep in mind, in my area -30C/-22F is our low winter temp and the barn will not have any heated space planned. (ie I am not thinking about an inverter in the Barn, at least not yet thinking about an inverter in the Barn).
One option would be to buy a third MPP 6048, and run parallel cables to the two additional MPP inputs, each using 2S-4P , some clipping would be expected at peak solar, and each cable would need to be sized for 40A/ 100vdc (likely requires 1AWG-1/0 cable x2 runs). The third MPP can parallel to the first two, increasing AC-output capacity, maintain comms, become a possible back up inverter to one of the first two if tragedy occured. Higher standby loss is one down-side, although this additional inverter could be set solely as a SCC and not output AC generally.
Another option is use a dedicated SCC capable of high voltage DC, connected to the battery bank separate from the existing inverters, using 8S-2P this would result in about 360-400vdc/ 17-20A range, a single cable would be possible, (likely requires 8AWG x1 run). ESS monitoring could become an issue, require additional equipment.
I have no experience with micro inverters, however I understand they would convert the DC to AC at the Barn, allowing the transmission to the shop via AC instead of DC I suspect this power then could feed the AC input on the inverters as an alternate to the grid/generator input. I am not sure if this is correct or not. If I imagine the Barn PV converted to 240vAC the resulting peak output is 240vAC / 30A requiring a cable 6AWG. If this power passes through the inverters to the ESS the current system will keep track of battery SOC as it does now.
120/240 AC available at the Barn will be required, and if this could be done locally rather than running DC to the shop, and AC back again x 280 feet would save some expense and add efficiency.
Maybe there are other options I have not considered?
I would be interested in your thoughts/experience/input.
