There are "solar aware" EV chargers out there.
One of them that I know of is popular in the UK: Zappy Charger
Zappi Elektrische Auto Lader - gebruik uw eigen energie om groener op te laden
www.zappi.info
This charger will take as much energy possible from solar, then the rest from the AC grid.
Thanks.
I’ve already got the capability to charge using all available solar power first and importing any insufficiency from the grid.
My goal is to find a way to avoid any import while also minimizing any export.
I think I can actually achieve that using y GTIL inverters and assuring that the EV charge power is always greater than available solar power. The remaining energy needed would be supplied from my LiFePO4 battery, so zero export and zero import.
It’s just very inefficient to do it that way so I’m hoping there is a better way.
But, I do have some doubts about your solution:
Even if you had an EV with an onboard AC inverter, it would be inefficient to hook it up to an AC-DC charger just to charge your batteries.
That's because an EV's high voltage battery is DC, then you go through the onboard DC-AC inverter, and then again back to DC from AC of the Lifepo4 charger.
Each "hop" has its inefficiencies, ranging anywhere from 5% to 25% loss.
For sure. The round-trip efficiency of what I am considering is lousy.
I figure that the AC-coupled solar power I’m exporting today charges an EV at ~85% efficiency.
Then when the EV inverters that power to AC, that another 90% efficiency “hop” getting to 76.5% net.
Then I’m using that energy to charge my 24V LiFePO4 battery with an AC charger, which is another 90% ‘hop’ bringing me down to 68.85% net.
Lastly, when my GTIL inverters such that battery energy out to offset consumption, that last ‘hip’ is at a p*ss-poor efficiency of 80%, meaning every 1kWh I did not export and instead used to offset consumption through this multi-hop path only offsets ~0.55kWh of consumption (55% efficiency).
That sounds pretty abysmal until you understand that California is on the verge of deciding to credit each 1kWh of solar export at only 0.2kWh of consumption.
So sending a kWh through that loop during the day to consume it offsetting loads at night values it at 275% of what I would get for it if I exported it to the grid…
There are other solutions to charge your Lifepo4's more efficiently from an EV, but they would require you to manually switch the car On and Off.
I’m interested to learn more, but I’m assuming the EV will always be on so that the V2L port is active.
Another option would be to connect the Ioniq 5's (or other EV with AC output) AC output to a "critical loads" panel in your house, which could either be manually disconnected from the grid or automatically with an ATS of sorts.
Yes, using the Ioniq to directly power loads is more efficient, but not worth the complexity. Now I’ve got an ‘island’ of house power that is not synced to the grid power powering other loads. Plus I’d need to wire in an ATS and critical loads panel.
Mixing true off-grid power with grid-tied power in the same house is a lot more complicated and expensive (and possibly dangerous) than just adding a bit more solar power to compensate for lost efficiency.
Using the Ioniq in the way you are describing during a power outage (switched-on manually) makes total sense and I might go that route rather than use the 3kW PSW inverter I have for that purpose, but I have no interest in rewiring my house to have an off-grid ‘island’ for everyday use (other than that extension chord powering a battery charger).
Solar panels and the solar power they generate are the least expensive variable in the equation.
The 5000KWh in annual power I generate now to cover my annual consumption may translate to a ‘gap’ of 2250KWh if I use that power in this way.
Today the utility forces me to purchase a minimum of 600KWh per year which is likely to increase to 1200kWh soon, so the ‘gap’ I’m facing is down to 1000 to 1600kWh.
I get about 1kW/W in annual production, so I’ll need another 1kW to 1.6kW of solar panels to close that gap at a cost of $400-640.
I can’t see any other option that gets me there for anywhere close to that budget (again, assuming the investment in a V2L-capable EV).