Solar Inverter/Charger

[lne937s]

I was looking around at solar inverters and was thinking that it would be great if you could order a integrated grid-tied inverter/car charger. Run the 220v line to one loaction that does both. It would be a great way to promote EVs in their cleanest application (using renewable energy). When ordering your car, you could get the solar capacity installed to power it. A small 1.5 kW system could easily provide enough electricity to offset the ~200kWh/month needed to power the car. With solar panels comming down to less than $2 per watt and all the incentives available, you could potentially generate your own zero emission energy to power your car for 20 years for the same cost as a couple of years worth of gasoline in a conventional car.

http://www.atensolar.com/m5_view_item.html?m5:item=150-141

For a larger home system, when the sun is shining, you could send more power to the car than from a typical 220v line-- potentially bypass to send ~12kW DC with no conversion losses (to charge the car from empty in less than 2 hours, like level 2.5 charging), switching to regular level II charging when the sun isn't shining. A system that size would also easily provide enough electricity to offset the energy needs of a large house-- basically eliminating all home energy bills.

http://www.atensolar.com/m5_view_item.html?m5:item=200-312

For an even bigger 48 kWh Level III system, you could relieve the burdon on the grid from charging during the day (when many people may quick-charge, but electricity demand is higher). It seems like much of the circuitry needed to make the quick-charger function (3-phase line, transformers, etc.) is already a part of the larger industrial inverters, so integrating the two may reduce cost/energy losses over having two seperate systems...

http://www.atensolar.com/m5_view_item.html?m5:item=200-355

(Btw- I have no connection to the website I linked to, it was just one site I was looking at)

 

[botsmaker]

The way to do it would be to make enough power during the day, sell it to the grid at the high rate. Then buy it back during the night when you charge. It would pay for itself. "Sell high, buy low". That is the way to go.

 

[Coffee_Slurry]

I've wondered if the wiring for my PV could be shared with an EVSE.
The inverter has its own disconnect box, and dedicated breakers on both phases (220v).
The EVSE could use the exact same wires, since the PV will never present a load anyway.

So if you have a 40A breaker for your PV, you could add a 40A EVSE to the same circuit, I would think. The inspector may disagree.

 

[johnr]

The way to do it would be to make enough power during the day, sell it to the grid at the high rate. Then buy it back during the night when you charge. It would pay for itself. "Sell high, buy low". That is the way to go.

+1
Couldn't have said it better myself. As logical as it sounds to recharge the car directly with the solar panels, it actually makes more sense to sell your solar power at peak pricing during the day and then buy it back at the off-peak rate at night to charge the car. As a bonus, doing it this way also helps balance the power grid and puts more renewable energy into the mix for your neighbors.

The exception would be if you're "off-grid"

 

[garygid]

It appears that SDG&E might not pay much for PV power, at any time. Perhaps just the electricity rate, and not the "distribution" tariff. But, maybe that has not been finalized yet?

 

[planet4ever]

I've wondered if the wiring for my PV could be shared with an EVSE.
The inverter has its own disconnect box, and dedicated breakers on both phases (220v).
The EVSE could use the exact same wires, since the PV will never present a load anyway.

You mean like this?

Actually, I added a new subpanel tied in between the PV breakers and the house circuits. At the moment I have only a single 20A breaker there feeding a 120V outlet I will use to charge the LEAF, but I've wired it for 240V with #8 wire and I could put in dual 40A breakers feeding a 240v EVSE.

Yes, my poor little LEAF is going to have to live outdoors in a tent.

 

[greenleaf]

I've wondered if the wiring for my PV could be shared with an EVSE.
The inverter has its own disconnect box, and dedicated breakers on both phases (220v).
The EVSE could use the exact same wires, since the PV will never present a load anyway.

So if you have a 40A breaker for your PV, you could add a 40A EVSE to the same circuit, I would think. The inspector may disagree.

The danger is that parts of the wiring could theoretically go beyond 40A without tripping the breaker, causing a fire hazard.

E.g. PV is running and supplying 35A. A fault in the EVSE causes it to draw 65A. This however does NOT trip the breaker because the net currrent drawn is only 30A. The load on the wiring to the EVSE would be exceeded.

I think one solution to the above is to have a subpanel, with breakers for the EVSE like what planet4ever described. Because PV is a source and EVSE is a load, it is important to evaluate each segment of the wiring to make sure that it does not exceed the current capacity spec.

 

[garygid]

Adding a new dual 40A breaker for the output to the EVSE solves any over-current condition, right?

 

[Gonewild]

Just adding a breaker does little to stop a fire in your panel. Over loading a breaker panel will risk melting the sub bar. So a 125 amp panel can not be made a 200 amp panel by adding more breakers.

 

[greenleaf]

Adding a new dual 40A breaker for the output to the EVSE solves any over-current condition, right?

The safest way would be to have a new sub-panel, which has breakers for the PV and EVSE. This sub-panel is connected to a dedicated circuit with 40A breakers in the main panel.

If the PV is rated at 40A, the sub-panel should have a rating of 80A to prevent the overloading case described earlier (the maximum possible current input into the panel is 40A from the main panel, and another 40A from the PV, giving a total of 80A).

 

[garygid]

If the main panel is OK with the 40-amp PV input through a 40A breaker, then putting both the PV and EV on 40A breakers in a sub-panel, which is connected to the main panel through the original 40A breaker that was used for the PV (before the PV was moved to the sub-panel), should be close to good, right?

 

[greenleaf]

If the main panel is OK with the 40-amp PV input through a 40A breaker, then putting both the PV and EV on 40A breakers in a sub-panel, which is connected to the main panel through the original 40A breaker that was used for the PV (before the PV was moved to the sub-panel), should be close to good, right?

The sub-panel needs to be rated at 80A.

 

[garygid]

At least 80, but a "standard" 100A panel would also do the job.

Overloading the MAIN panel is actually the issue, which would trigger the panel and service upgrade, right?

In this configuration, provision for a 2nd "subtractive" EV-use meter, could easily be included in the EV charging circuit, if desired.

 

[greenleaf]

At least 80, but a "standard" 100A panel would also do the job.

Overloading the MAIN panel is actually the issue, which would trigger the panel and service upgrade, right?

In this configuration, provision for a 2nd "subtractive" EV-use meter, could easily be included in the EV charging circuit, if desired.

Yes, the sub-panel rating only addresses the safety issue related to the PV and EVSE circuits.

If you overload the main panel, you will get more breaker trips from the 100A breaker -- which should still be safe though (assuming the 100A breaker does not malfunction). It's just inconvenient not to be able to run the EVSE, the electric dryer, the electric oven, the AC and the spa all AT THE SAME TIME. ;-)

 

[garygid]

Adding the 40A PV breaker to my 150A main breaker box required downgrading the main input breaker from 150 to 110 (150 - 40 = 110). So, they were going to replace the 150A breaker with an easy-to-obtain 100A breaker.

Actually it should have been 150A + 20% (30A) - 40A => 140A for the PV downgrade, but the electrician did not know that.

Then, finding breakers in the 140A to 120A range seems "impossible", and even finding the 110A breaker took some searching.

 

[DaveEV]

If the main panel is OK with the 40-amp PV input through a 40A breaker, then putting both the PV and EV on 40A breakers in a sub-panel, which is connected to the main panel through the original 40A breaker that was used for the PV (before the PV was moved to the sub-panel), should be close to good, right?

The sub-panel needs to be rated at 80A.

Actually, not quite. The NEC lets you backfeed a little extra into a panel, up to 120% of the panel's rating.

So if you have a 100A panel fed with a 100A breaker, you can actually feed another 20A PV into the panel.

So if you are feeding your subpanel with a 40A breaker, you would actually only need a 67A rated panel to have a 40A EVSE and 40A PV plugged in to it. (67*120% ~= 80 - 40 = 40). Of course, no one makes a 67A panel. Looking at HomeDepot.com it appears that commonly available sizes are 60, 70, 100, 125. The 70 seems like a bit of an oddball, so using a 100A subpanel seems like the way to go.

Keep in mind that your main panel must also be rated at 200A to handle 40A of PV.

 

[planet4ever]

In my case the new EV circuit does not go through the main panel at all, so the term "subpanel" is probably a misnomer. I have a 125A main breaker adjacent to the meter, and the main panel is thirty feet away from there (in the furnace closet). The PV system, which was professionally installed with city inspection, tied in at the house side of the main breaker. Since the PV has a 30A breaker, that means my main panel could see 155A, which might be an overload for its main bus, but as I said, that was approved at the time (four years ago).

All I did was tie in my new panel on the house side of the PV breaker; which is effectively the house side of the 125A main breaker. Well, not exactly, because there is a PV disconnect knife switch between the PV breaker and the main breaker. That, plus the disconnects between PV panels and inverters, just made it easy and safe for me to do the new wiring without shutting house power down.

The bottom line is pretty much what GroundLoop suggested, though with an extra breaker: Power flows from the house side of the PV breaker to the house side of the main breaker during the day. It will flow (once I get my LEAF) the other direction through those same wires at night.

 

[greenleaf]

In my case the new EV circuit does not go through the main panel at all, so the term "subpanel" is probably a misnomer. I have a 125A main breaker adjacent to the meter, and the main panel is thirty feet away from there (in the furnace closet). The PV system, which was professionally installed with city inspection, tied in at the house side of the main breaker. Since the PV has a 30A breaker, that means my main panel could see 155A, which might be an overload for its main bus, but as I said, that was approved at the time (four years ago).

All I did was tie in my new panel on the house side of the PV breaker; which is effectively the house side of the 125A main breaker. Well, not exactly, because there is a PV disconnect knife switch between the PV breaker and the main breaker. That, plus the disconnects between PV panels and inverters, just made it easy and safe for me to do the new wiring without shutting house power down.

The bottom line is pretty much what GroundLoop suggested, though with an extra breaker: Power flows from the house side of the PV breaker to the house side of the main breaker during the day. It will flow (once I get my LEAF) the other direction through those same wires at night.

What is the rating of the new panel? It's hard to discern from the description but it sounds like the new panel could receive 30A from the grid and another 30A from the PV system?

 

[planet4ever]

What is the rating of the new panel? It's hard to discern from the description but it sounds like the new panel could receive 30A from the grid and another 30A from the PV system?

Oops! I didn't think of that. I guess it could theoretically receive 125A from the grid, which would melt the #8 wires between it and the main breaker. But the same thing is true of the box next to it which was installed with my PV system. Come to think of it, there are what look like big fat long fuses in the knife switch disconnect between the main breaker and the PV breakers. They may limit the current to 30 or 40A, but I'd better check.

The panel I got is rated at 70A.

 

[jstack6]

the possibility of a problem with the car and OV are almost zero.

I have GRID tied solar system since 2001, I have been charging my plugin vehilces off the same power box that feeds the house, PV , Air Cond etc. Each is on it's own circuit and fused for that use.

I help my utility with clean power all day, I charge off peak and use their excess with low load on the GRID and transformas at all times. They sell the extra powwr I made to my neighbors and we all win. It's good for everyone.

Putting solar panels on your car is not a good idea. It's never at the best angle to the Sun, it can help the GRID and if youy park for a few days you better have a charge controller that cuts out. The panels are also breakable and glass. On you home solar makes a lot of sense. It can run your home ,car and help the utility.