This is a customer’s system, details posted with the permission of the customer.
The house loses sun early in the day due to hills blocking the late afternoon sun. The panels are DAH NTopCon 430w which do well in NZs often overcast days. The MultiPlus-II 48v 5000va was chosen as it suits the max power demand now, but can be paralleled later to get 10kw if required.
The panels are controlled by a SolarSmart MPPT 150/45 with the panels in 2s4p, with 2 runs of cable from the panels, so that there are effectively 2 sub arrays of 2s2p that are joined at the isolator to make 2s4p. The reason for this is to halve the current on the 4mm solar cable. It also gives an easier troubleshooting and commissioning situation.
Currently the power sources are primarily solar, with grid backup. Later this year there is a microhydro install planned which might add a few hundred watts of 24/7 production. The data collected by the Cerbo and VRM can be assessed after the first winter to determine if the grid can be dropped, or maybe how many extra panels might be required in order to drop the grid. With the addition of microhydro, even a few tens of watts can make a big difference when that power is trickling in 24 x 7.
We (designers) can model a home or system for hours when doing an energy audit, but at the end of the day our wattage info from appliances will always be very accurate, and our estimated number of hours for each appliance will always be wrong, at best a guess. This is where real data from the VRM is gold - it tells you exactly how much energy was required from the 2nd source (in this case grid, but in other cases generator). From there, we can accurately deduce how many extra panels or batteries it will take to make the backup source redundant. This is the way we recommend customers who are on-grid get to off-grid.
The VRM can also be a good judge of how well we designed the system, and whether we met the design goals.
The Cerbo S-GX is powered directly from battery, so that it isn’t dependent on the output from the inverter.
The MP has the ESS assistant loaded, and as you can see in this graph, the battery min over the ~2 week period is 58%, so battery size looks appropriate.
The system brought in zero grid power over this time, so the panel array looks appropriately speced so far, but remember its summer in NZ at the moment, and we are currently getting very nice weather.
The batteries are 2 x 5kwh Dyness DL5.0 in a rack format.
Did we size the inverter correctly?
Some designers might say that the inverter is over-spec - in this ~2week period the max was 1300w, however;
-
i think that some spikes have been missed on this graph
-
the difference in price is small
-
the running cost of the 5k is only 7w more than the 3k.
-
max battery charge current (from grid or gen) in the 5k is double the 3k (70A vs 35A)
I’ll update this when the hydro goes in!
