Simulations were done to calculate the theoretical length of operation given different weather conditions. SAM gave projected array generation of the existing solar array and the corresponding solar irradiance that yields this generation. With this data, we can estimate array output for a sunny day and an overcast day to analyze how these variations will affect the functionality of the Powerwall.
The “best case” simulation assumed a string of sunny days in which the panels could continue to charge the Powerwall when disconnected from the grid. The Powerwall could power the critical and additional optional loads indefinitely during a string of days with high solar irradiance.
The “worst case” simulation assumed a string of overcast days where the panels could still charge the powerwall, but the power output would be significantly lower than the “best case” situation.
The Powerwall could power the critical loads indefinitely with the available solar power density, or it could power the additional optional loads for approximately five days.
No Charge Case
The “no charge case” assumes the Powerwall cannot be charged at all by the solar panels when disconnected from the grid. The Powerwall’s charge at the time of the outage is the only available power.
The Powerwall could power the critical loads for a little over a full day or it could power the additional optional loads for just under one day.