As promised, I’m reporting back with an update on our new solar microgrid installation. The installation and initial testing were completed last week - we're proud new Powerwall owners!
Here are the project highlights with a few embedded photos:
- Our new residential microgrid includes thirty 320-watt Hanwha QCELL solar panels in two strings for roughly 10 kW of power generation, a single 10 kW SolarEdge HD inverter w/optimizers, Tesla energy gateway, new microgrid breaker panel, and an array of 3 Powerwalls providing over 40 kWh of energy storage with 21 kW of peak power capacity and up to 15 kW of continuous power capacity.
- The local power company does not support net-metering, only dual-metering. This limitation required a slightly different "zero-export" system configuration in order to achieve our objectives for a fully self-powered home that will also operate during utility grid outages. The zero-export featured works fine so far - we don't send any energy to the grid and we rarely expect to consume any energy from the grid.
- The project installation took a week. It was started and completed on-time by a competent local Tesla reseller in NC.
- The quality of the rooftop installation work was excellent. The mostly-black panels look great on the charcoal-black roof, which has a due-south orientation. The panel layouts were very well done, the wiring is invisible, and we expect the roof penetrations will be trouble-free.
- The interior installation of the Powerwall array, energy gateway, inverter, generation panel, and integration with our main electrical breaker panels was also very well done. Perhaps most impressive was the fact that the overall microgrid system worked correctly the first time it was activated for testing. The Tesla mobile app came online immediately, showing normal Powerwall operation without a hitch. A few pictures of the (unfinished) electrical room are shown here:
- Based on the first day of initial system testing and Powerwall charging it appears the solar generator will easily meet its 10 kW power specs. On a mid-December day, with the sun fairly low in the sky and high clouds partially obscuring the sunlight, we saw consistent generation in the 5-6kW range and peak generation in the 8-9 kW range during the middle of the day, with roughly 37 kWh of total daily generation. I expect these numbers will increase substantially on longer days with full sun in the spring/summer time frames.
- Based on data from the Tesla energy gateway during the first day of generation and Powerwall charging, all power flows were shown correctly. All solar energy was directed to the Powerwalls until they charged to 80-90% by late afternoon, during which time all energy consumed from the grid was directed to power the home. After charging the PWs, the home automatically switched to self-powered mode with the home drawing 100% of its energy from solar/PWs and zero energy from the grid. Perfect so far.
- Here are some Tesla mobile app screen shots of first-day operations. Note the times:
Initial system power-up in the morning. Low Powerwall charges out of the box, low solar generation. All solar generation routed to charge the Powerwall array, all home consumption from grid power:
Generation and PW charging improving by mid-morning.
Stronger generation and good charging progress by early afternoon, self-power mode in progress:
The critical zero-export functions of the system also seemed to work well as we saw inverter generation reduced to match the home consumption in real-time and did not see any energy from solar or PWs flowing back to the grid.
No more sun after 5pm - home is self-powered: