There are several problems with this diagram.
- The Gateway disconnect is not shown.
- All AC (Wall connector, solar inverter, backup loads) should be shown connected to the Backup Panel.
- The sizing of the solar inverter is limiting the combined output of A) Solar B) Batteries C) Vehicle DC discharge
- The diagram only shows charging direction on AC to the Wall Connector.
The only vehicle that supports PowerShare delivers that power to the home with AC, not DC. I understand that you are proposing a new DC path from the vehicle, and that's in fact, the way that Ford does it. However, Ford is using a dedicated inverter, and a relatively small one at that. Also, in the DC domain, a simple MPPT or PWM "let through" power transistor only works when the DC source voltage is higher than the target (battery) voltage. If you want to go the other way or need the flexibility to charge and discharge regardless or DC voltage differences, you need a DC-DC converter which has higher losses.
As a form of "devil's advocate" let me explain the benefits of Tesla's existing scheme and the benefits of your scheme of adding DC.
Benefits of Tesla'a all AC system where Solar, Battery, and Powershare all have their own inverters and are AC coupled.
- Battery, Solar, and vehicle have dedicated output and each inverter is properly sized for its own purpose and they don't limit each other.
- Safety certification is easier for cables, inverters, EVSE that don't handle HVDC.
- Compatibility is better for incremental additions to a home. Powerwall Batteries can be added to an existing solar system. Powershare can be added to existing solar + Powerwall system.
Benefits of DC connected solar, battery and vehicle:
- Incrementally higher efficiency doing power conversion all in the DC domain. Maybe this is like 98% vs 96% each way, maybe 95% vs 90%, but it depends on relative voltages.
- Possibly tighter integration of each source in the DC domain to control power flows more effectively.
I would argue that AC coupling and having a defined way to communicate command and control signals for things like vehicle discharge rate has more benefits at the expense of slightly lower efficiency.