I'm installing a 400A service with two 200A subpanels for a client. He wants a propane generator, solar panels, a battery bank and will be connected to the local power utility but does not want the solar to be grid tied. I know how to install daisy-chained automatic transfer switches for the generator (Generac ATS's are set up for this) but I'm looking for the best options for connecting all 4 sources. So far I've found that many vendors are generator only, some solar/battery only and some are low amperage only.
Solar, Battery, Generator, Utility combination
- Thread starter bmaclaff
- Start date
The design depends on what the client means by not having the solar tied to the grid. If they want a non-export system that works in parallel with the grid that's one design, if they want a PV+Gen+BESS system that only works as a backup power source when the grid is down that's a different design.
Birken Vogt
Senior Member
- Location
- Grass Valley, Ca
If you do not already have experience in this arena and have a list of products and part numbers and an idea of how it is going to be done in your mind already, I would not want you to take on this project. There are a lot of pitfalls and a lot of products to choose from and they don't all play well together, or work as advertised. Either that or throw a big learning curve price at the project. I've seen a number of these projects end up where the installer walked away with the project incomplete or incompletable because foundational steps were missed.
pv_n00b, yes a non-export system that works in parallel with the grid. I think the client's hope is to have the following priority- solar, battery, utility, propane generator in that order.
Birken, certainly good point. I'm doing the wiring on the job, that's settled. I don't mind getting extra expertice as needed. I agree with the concern about products not playing well together. I'm hoping to get an idea from those of you who know far more than I do, a good direction to go. I'd love it if I could find an ATS that could handle all or most of the options so that the solar array/inverter/batteries could be added later.
Birken, certainly good point. I'm doing the wiring on the job, that's settled. I don't mind getting extra expertice as needed. I agree with the concern about products not playing well together. I'm hoping to get an idea from those of you who know far more than I do, a good direction to go. I'd love it if I could find an ATS that could handle all or most of the options so that the solar array/inverter/batteries could be added later.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Not wanting for the solar to be grid tied and a non-export system that works in parallel with the grid are two different things.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
What is the customer's goal:
- Offset their energy use but not have to deal with an interconnect agreement?
- Stick it to the man and not feed solar back to the grid, not matter what it costs them?
- Minimize costs relative to some particular tariff structure?
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
People who try to "stick it to the man" with cleverly designed renewable energy systems often end up sticking it to themselves.
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Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
- Occupation
- EC and GC
My 2 cents, which isn't worth even that much, is:
Any combination of 3 is easily accomplished, effective, and generally worth the cost.
Having a system with all 4 is a pretty useless endeavor in most, if not all, situations.
I'm going through this with a customer right now, and it's a bit of a disaster. I told them if they just want to offload money, it's a lot easier to take a big pile of it and light it on fire in their driveway. They have a partially installed solar system, an inverter, an MTS that needs to be changed to an ATS, no generator, and no BESS. I'm not sure why they want it all, for probably what will amount to 10 hours or less of utility outage a year, and yet here we are.
Solar with BESS and a generator to charge batteries when the sun is hiding is very common on off-grid sites, and there's a lot of them in my area.
Solar with battery and utility, whether you interconnect the solar or not, is very common, although non inter tied systems are pretty rare.
Like the others have said, it's important to find out what they are trying to accomplish before attempting to design the system.
Any combination of 3 is easily accomplished, effective, and generally worth the cost.
Having a system with all 4 is a pretty useless endeavor in most, if not all, situations.
I'm going through this with a customer right now, and it's a bit of a disaster. I told them if they just want to offload money, it's a lot easier to take a big pile of it and light it on fire in their driveway. They have a partially installed solar system, an inverter, an MTS that needs to be changed to an ATS, no generator, and no BESS. I'm not sure why they want it all, for probably what will amount to 10 hours or less of utility outage a year, and yet here we are.
Solar with BESS and a generator to charge batteries when the sun is hiding is very common on off-grid sites, and there's a lot of them in my area.
Solar with battery and utility, whether you interconnect the solar or not, is very common, although non inter tied systems are pretty rare.
Like the others have said, it's important to find out what they are trying to accomplish before attempting to design the system.
Sounds like a micro-grid setup. From what I’ve seen, it’s usually easier to keep the generator on standard service-rated ATSs and let solar + batteries run behind a hybrid/off-grid inverter, instead of trying to find one box that handles all four sources at 400A. A lot of people split it into two 200A sections, or put PV/battery on one panel with selected loads. Just make sure the inverter has proper anti-islanding, since the solar isn’t grid-tied.
By the way, have you ever installed BYD Blade batteries for anyone? I saw a link https://cmxbattery.com/product/48v-...m-solar-home-battery-for-home-energy-storage/ claiming 10,000+ cycles, which surprised me. I always thought those were mainly for EVs , are they actually practical for home energy storage? Just curious.
thanks to everyone for input. To clarify, the client wants his solar system to be independent of the local power utility. sorry for unclear language on my part. I agree with the potential inefficiency of having this much redundancy. the location is fairly remote, which helps make the case. The rest of the rationale is simply the client's wish and he is willing to invest in his interests. He simply likes solar, but wants to ensure that if utility power is off that he will have the comfort of the propane generator if needed.
I did find at least one option (Tigo 200A MCB Auto Transfer Switch | Backup/Grid/Generator) that appears to coordinate all 4 but it remains to be seen if two of them can work with one generator. Peter-Lei's comment about separate solutions still may be the way to go though.
I did find at least one option (Tigo 200A MCB Auto Transfer Switch | Backup/Grid/Generator) that appears to coordinate all 4 but it remains to be seen if two of them can work with one generator. Peter-Lei's comment about separate solutions still may be the way to go though.
Tigo 200A MCB Auto Transfer Switch | Backup/Grid/Generator
Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
- Occupation
- EC and GC
So what is the planned order of operation?
What will be the standard situation, house runs on utility power, solar does……? Keeps batteries topped off? What are the batteries doing? Are they configured like a UPS, and utility is running through them? Then what does solar do? Or are they unconnected until power failure and you need a ATS?
When does the generator come on, just to top off batteries? Will the battery bank be large enough to handle the entire load of the house, including peak demands, when utility is down, or will it need the generator also?
What will be the standard situation, house runs on utility power, solar does……? Keeps batteries topped off? What are the batteries doing? Are they configured like a UPS, and utility is running through them? Then what does solar do? Or are they unconnected until power failure and you need a ATS?
When does the generator come on, just to top off batteries? Will the battery bank be large enough to handle the entire load of the house, including peak demands, when utility is down, or will it need the generator also?
the hope is that the solar can power the house when possible, excess energy going into the batteries, switch to utility power when solar/battery not enough, switch to propane generator when all else fails. The client will want the largest solar array he can install. Battery bank size not decided yet. Yes it would be great if the propane generator topped off the batteries with excess when it is running.