Powering your home via PPO WHILE also using solar

[dmd3home]

I LOVE my PPO and have used it now many times to power my entire home. In fact, it is the primary reason I bought the Lightning vs a Cybertruck or Rivian. I utilize the PG&E supplied meter mounted auto transfer switch and cord to my PPO 240v outlet in the bed. It works perfectly. However, as a precaution, I always open my solar supply breakers prior to hooking up PPO. During the day, my solar is more than enough to power my entire house, but unfortunately, because my solar utilizes microinverters that require a constant power source, when the main power goes off, so does my solar....very irritating! But, the question is, if the main power goes off and I switch to PPO, can I then again close in the solar input breakers to power up the microinverters and thus my full solar power array? So now you essentially have two power sources in parallel. Because the microinverters are getting their power from the truck, the two sources will be in phase. Ideally, in theory anyway, the solar should dominate and back down the PPO which would only add power if necessary and then take over when the sun went down. The higher voltage should prevail which should be the solar. The only real issue I see is that if your loads were not adequate to use all your solar, there would be nowhere for the excess solar to go (which isn't a problem when you're connected to the grid). But, to ensure there is enough load, you could also now charge your truck at the same time! Then, the only caution would be to have enough space in your truck battery to accept the load required. Yes, it's certainly safer to just open my solar input breakers, but I just hate having 8 kW of solar just sitting there, unavailable, while I'm draining my truck battery. Has anyone tried this?

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[Maquis]

No. A conventional grid-tied solar arrangement requires a source that can absorb excess power. The PPO cannot do that.

 

[tearitupsports]

No this would be extremely dangerous without a hybrid inverter and batteries that is made to manage that and can phase shift your solar to a safe condition if necessary.

 

[dmd3home]

No. A conventional grid-tied solar arrangement requires a source that can absorb excess power. The PPO cannot do that.

Right, that's why I suggested charging the truck at the same time. Actually I believe it's Emporia that makes a variable charger that actually will skim off excess solar and feed it into the EV......of course you have to have room in the battery. But I think it could work!

 

[dmd3home]

No this would be extremely dangerous without a hybrid inverter and batteries that is made to manage that and can phase shift your solar to a safe condition if necessary.

Phase shift to a safe condition??? Both sources (truck and solar) are forced to be in phase as the solar microinverters are getting their power from the truck....no different than getting their power from the grid and powering the house and backfeeding the grid....all in phase.

 

[K6CCC]

The problem is that your solar inverters are designed to take whatever DC power is available and make the maximum amount of AC power from that. They have no provision to lower the power output to match your house load. For example, if you have 10KW of DC power from your solar panels, the inverters are going to make 10KW - inverter efficiency losses of AC power (let's say 9KW to keep the number simple). That power has to go somewhere. When hooked up to the utility grid, the grid accepts that power without any issue. If the grid is not there, your house MUST accept that much power. It likely can't and the result will most likely be a loss of frequency or voltage control. And I guarantee that the inverter in your truck is NOT designed to be paralleled with some other power source. Good way to blow stuff up.

DON'T TRY IT unless you like watching your inverters go up in smoke.

 

[tearitupsports]

Phase shift to a safe condition??? Both sources (truck and solar) are forced to be in phase as the solar microinverters are getting their power from the truck....no different than getting their power from the grid and powering the house and backfeeding the grid....all in phase.

I think I have my terminology wrong. I believe it is frequency shift.

Hybrid battery inverters are able to frequency shift their signal when offgrid and the battery is full. AC coupled Solar inverters, by code, see the frequency shift and lower their output accordingly. It is basically a way they communicate over the power line.

If you start your pro power and solar panels at the same time, you are going to start a fire somewhere.

To do what you want to do, you need a battery system that has a proper generator input and AC coupled solar capability.

There are several threads on here about doing that. I run my solar off-grid with the truck pro-power by using the Sigenergy system. Others have succesfully tested Franklin. Sol-Ark and EG4 also have this capability. EG4 also has a secondary option where the Pro-power hooks to a specialized 48V DC power supply to charge the battery directly instead of powering the home load panel. I believe this is called the chargeverter or something like that.
My Sigenergy system works awesome but the minimum to do what you want to do is about $5k in components. I think most others are going to be around the same (hybrid inverter, automatic transfer switch, and small battery). There is also some wire/conduit, disconnects. Labor will be needed if you aren't a DIY person or very comfortable with electrical.

 

[frautumn]

I utilize the PG&E supplied meter mounted auto transfer switch and cord to my PPO 240v outlet in the bed.

Is this the same as the PG&E BPTM (Backup Power Transfer Meter)? If so, my understanding is that it only works if the grid has no power (and your solar breaker is turned off)-- are you saying you can use it whenever you want, even with grid power?

 

[Maquis]

Right, that's why I suggested charging the truck at the same time. Actually I believe it's Emporia that makes a variable charger that actually will skim off excess solar and feed it into the EV......of course you have to have room in the battery. But I think it could work!

The algorithm used by Emporia is not precise and cannot react to load changes with zero time lag. There will still be some solar production with no place to go as your house loads change. I don’t think you’ll smoke your inverters - they will simply shut down.

 

[dmd3home]

Yeah, just hoping someone out there has figured this out....not sure I want to be the guinea pig. I know with my offgrid solar the solar controller just shuts down the production if there's no where for the solar to go. I'm just not sure on the grid tied with microinverters.
Of course,' if I was charging the truck at the same time and there was sufficient space in the battery, I could go a long time and could manually intervene if the truck battery got too full. Theoretically I could have a completely sustainable offgrid system with the truck as the backup battery.....just thinking.

 

[K6CCC]

Yeah, just hoping someone out there has figured this out....not sure I want to be the guinea pig. I know with my offgrid solar the solar controller just shuts down the production if there's no where for the solar to go. I'm just not sure on the grid tied with microinverters.

There is a massive difference in off-grid vs grid tied inverters. Off grid inverters are designed as stand alone devices that expect that they are the sole source of AC power and MUST regulate voltage and frequency as the loads change. Off-grid inverters normally can not be connected to any other inverter - some fancy ones can, but they have to be designed for it.

BTW, the reason that grid tied inverters shut down when the utility power is lost is that if they didn't your inverter would be trying to power power your neighborhood. It presumably does NOT have the capacity to power the neighborhood. The bigger problem is that if it somehow actually does not trip offline while powering the neighborhood, that 120 or 240 volts from your inverter will energize the utility transformer (backwards from normal operation - which does not bother it at all), and that would put distribution voltage (typically 4 - 16 KV) onto the distribution lines. That will easily kill a utility worker who is trying to work on the supposedly de-energized distribution line while he is trying to restore your service. It's illegal to backfeed the utility lines during an outage and highly dangerous. That is why grid tied inverters are designed to immediately shut down.

To get further on this, if you have a home battery system (Tesla PowerWall for example) that is connected to your solar system and all the parts are set up properly, the battery in the PowerWall will accept the excess generation from your solar. In that situation, the solar can happily generate all the power that it can, until such time as the PowerWall battery gets almost full. Then the controller that makes it all work together causes the inverter to shut down until there is enough capacity in the battery to start accepting power again. It's a big balancing act. Note, this was a very simply description of how this works.

 

[hajalie24]

It will work you just have to manage your loads as you're already aware. Charging the truck won't work though since you can only get 7.2kw out of the outlet, in fact if you can generate more than 7.2kw of solar it would get dangerous or trip your transfer switch. Maybe you can rig something up with power monitors to shut off some micro inverters as necessary.

I tested the opposite, I have a battery system that can island the solar so any excess gets soaked up by the battery (or frequency shifted to turn off) But at night ive tested using the truck with a grid tie inverter to supplement/charge the home batteries.

 

[dmd3home]

Is this the same as the PG&E BPTM (Backup Power Transfer Meter)? If so, my understanding is that it only works if the grid has no power (and your solar breaker is turned off)-- are you saying you can use it whenever you want, even with grid power?

I'm not sure I understand your question. Yes, this is the PG&E BPTM and yes, it's an automatic transfer switch so can only supply power to the house when the grid goes down. And yes, currently I first turn off my solar before powering the house from the truck. My real question here is can I then power on my solar? I assume the solar would dominate and back down the PPO. But the other issue is, if the solar produces more than my house loads, there's nowhere for the excess to go. So, I could first add a large load by charging the truck....plenty of load (actually charging the truck from the truck PPO) and then add in the solar.

 

[dmd3home]

There is a massive difference in off-grid vs grid tied inverters. Off grid inverters are designed as stand alone devices that expect that they are the sole source of AC power and MUST regulate voltage and frequency as the loads change. Off-grid inverters normally can not be connected to any other inverter - some fancy ones can, but they have to be designed for it.

BTW, the reason that grid tied inverters shut down when the utility power is lost is that if they didn't your inverter would be trying to power power your neighborhood. It presumably does NOT have the capacity to power the neighborhood. The bigger problem is that if it somehow actually does not trip offline while powering the neighborhood, that 120 or 240 volts from your inverter will energize the utility transformer (backwards from normal operation - which does not bother it at all), and that would put distribution voltage (typically 4 - 16 KV) onto the distribution lines. That will easily kill a utility worker who is trying to work on the supposedly de-energized distribution line while he is trying to restore your service. It's illegal to backfeed the utility lines during an outage and highly dangerous. That is why grid tied inverters are designed to immediately shut down.

To get further on this, if you have a home battery system (Tesla PowerWall for example) that is connected to your solar system and all the parts are set up properly, the battery in the PowerWall will accept the excess generation from your solar. In that situation, the solar can happily generate all the power that it can, until such time as the PowerWall battery gets almost full. Then the controller that makes it all work together causes the inverter to shut down until there is enough capacity in the battery to start accepting power again. It's a big balancing act. Note, this was a very simply description of how this works.

Yes, I actually have two solar systems. I have a grid tied system that puts out a max of 5.7kW (after 10 years, now closer to 4.5) that utilizes panels with individual microinverters and I also just put in a 2kW offgrid system with battery and inverter to use for charging my truck (and other stuff). So yes, I understand both systems.
Your concerns about "powering the neighborhood" are well understood...and, in fact, that's why I do have an automatic transfer switch that isolates my grid-tied system from the grid on grid loss. So, that is not a concern. Since I don't have a home battery system I'm trying to use my truck as the battery. Since I then don't have a "normal" inverter/solar controller as I do on my offgrid system, I'd have to control my loads and power sources manually. If the solar is producing more than the house loads, in theory it would back down the PPO power source but any excess still has to go somewhere. So, if first I start charging the truck or other EV(a sufficient load.... it's essentially charging the truck FROM the truck or charging another EV from the truck...which I do now) before cutting in the solar, now there is a place for any excess solar to go. The trick is to always have a place for the solar to go. As long as my loads stay higher than the solar output (house loads, charging the truck, artificial loads etc.) with the truck making up any deficiency as needed there should be no problem. As the sun fades you could drop the truck charging and then run strictly off the truck battery through PPO.
This is all theoretical at this point and I'm just looking for flaws in my thinking and was hoping there was someone who's tried this already. Thanks for listening.

 

[tearitupsports]

Yes, I actually have two solar systems. I have a grid tied system that puts out a max of 5.7kW (after 10 years, now closer to 4.5) that utilizes panels with individual microinverters and I also just put in a 2kW offgrid system with battery and inverter to use for charging my truck (and other stuff). So yes, I understand both systems.
Your concerns about "powering the neighborhood" are well understood...and, in fact, that's why I do have an automatic transfer switch that isolates my grid-tied system from the grid on grid loss. So, that is not a concern. Since I don't have a home battery system I'm trying to use my truck as the battery. Since I then don't have a "normal" inverter/solar controller as I do on my offgrid system, I'd have to control my loads and power sources manually. If the solar is producing more than the house loads, in theory it would back down the PPO power source but any excess still has to go somewhere. So, if first I start charging the truck or other EV(a sufficient load.... it's essentially charging the truck FROM the truck or charging another EV from the truck...which I do now) before cutting in the solar, now there is a place for any excess solar to go. The trick is to always have a place for the solar to go. As long as my loads stay higher than the solar output (house loads, charging the truck, artificial loads etc.) with the truck making up any deficiency as needed there should be no problem. As the sun fades you could drop the truck charging and then run strictly off the truck battery through PPO.
This is all theoretical at this point and I'm just looking for flaws in my thinking and was hoping there was someone who's tried this already. Thanks for listening.

Do NOT do this! The Pro-power is a one way transfer. It cannot absorb power.

Your other idea of trying to have a charger on the truck is terrible as well. It is going to try and pull a steady amount of power no matter what the rest of your system is doing. The moment you hit your charge limit or have a charger fault, you are going to burn your house down.

You just need to buy the correct equipment if you want to do this. It is available from many brands. Even the Ford HIS system can safely do exactly what you are wanting to do.

Stop trying to justify doing something incredibly dangerous and most likely illegal.

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