Battery Storage Systems

[isurf]

Not sure if this is the right forum or not but here it goes..

Does anyone have a reference source for the latest and greatest battery storage systems? Im located in SoCal where our new code cycle this year will likely trigger battery storage systems for a lot of the projects I work on. I have done quite a few small residential designs (<10kWh) but would like to get info on the larger systems.

I have heard some of the larger systems are in 3R enclosures with HVAC within the enclosure so they can be located outdoors (seems great for not triggering as many fire department issues with having them inside) but I'm not familiar with what manufacturer's to be looking into.

Is AC coupled the preferred way to go with the larger battery storage on commercial projects or is DC coupled used at all?

Thanks for any input!

 

[ggunn]

There is no one "best" Energy Storage System (ESS) for every application. We sell a lot of Tesla Powerwalls, but they have all been for residential systems. We don't see many DC coupled systems; we have not installed any in the last 5 or 6 years.

 

[don_resqcapt19]

You might want to take a look at NFPA 855, Standard for the Installation of Stationary Energy Storage Systems. Even if not adopted for your area, it is a nationally recognized standard, and could be cited in a civil case when there is a problem with the ESS after you have installed it.

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[isurf]

You might want to take a look at NFPA 855, Standard for the Installation of Stationary Energy Storage Systems. Even if not adopted for your area, it is a nationally recognized standard, and could be cited in a civil case when there is a problem with the ESS after you have installed it.

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Thank you! I'll check it out.

 

[isurf]

There is no one "best" Energy Storage System (ESS) for every application. We sell a lot of Tesla Powerwalls, but they have all been for residential systems. We don't see many DC coupled systems; we have not installed any in the last 5 or 6 years.

Thank you! I like that the DC coupled has less conversion loses but it seems like your PV system would need to be substantially larger than what you use during daylight hours for it to make sense. I can see the AC coupled battery systems being used to offset time of use metering plans to discharge during peak demand rates.

 

[jaggedben]

Thank you! I like that the DC coupled has less conversion loses but it seems like your PV system would need to be substantially larger than what you use during daylight hours for it to make sense. I can see the AC coupled battery systems being used to offset time of use metering plans to discharge during peak demand rates.

Either configuration can be used for that purpose. And most PV systems are sized to produce more than is used during daylight hours.

 

[BandGap1.1eV]

DC coupled systems are great if you have an AC constraint at your Point of Interconnection, but you can physically fit lots of PV on site. It's becoming common to have a 5+MWdc system being a 1MWac inverter, with a boat load of DC coupled storage to soak up the extra.

AC coupling is easier, but you could inadvertently push yourself over some arbitrary AC limit from the utility since the BESS inverter and the PV inverter techncially add their nameplates together. One way around this is with an export limitation controller and a utility grade relay to satisfy the dolts at the utility that you wont ever export more than X amount.

For residential systems, I would prefer DC coupled.

 

[jaggedben]

I would prefer DC coupled for residential if the available products were of equal quality, but unfortunately, in my opinion, they're not.

 

[isurf]

Either configuration can be used for that purpose. And most PV systems are sized to produce more than is used during daylight hours.

Sorry what I meant to say was the AC coupled battery could be charged by the grid during off peak and discharge during on peak hours.

 

[isurf]

DC coupled systems are great if you have an AC constraint at your Point of Interconnection, but you can physically fit lots of PV on site. It's becoming common to have a 5+MWdc system being a 1MWac inverter, with a boat load of DC coupled storage to soak up the extra.

AC coupling is easier, but you could inadvertently push yourself over some arbitrary AC limit from the utility since the BESS inverter and the PV inverter techncially add their nameplates together. One way around this is with an export limitation controller and a utility grade relay to satisfy the dolts at the utility that you wont ever export more than X amount.

For residential systems, I would prefer DC coupled.

This was my thought as well. If you could seriously oversize the PV DC size it might make sense to store the excess directly (no conversion losses) to a battery and discharge when you aren't producing solar or during peak demand.

Are there any big names out there that produce BESS systems that you could recommend I look into?

 

[jaggedben]

Sorry what I meant to say was the AC coupled battery could be charged by the grid during off peak and discharge during on peak hours.

So could a DC coupled battery. Although, generally, you're not supposed to do this with either configuration. You're supposed to charge from solar normally.

 

[isurf]

So could a DC coupled battery. Although, generally, you're not supposed to do this with either configuration. You're supposed to charge from solar normally.

Do you know of a manufacturer where this is possible? I remember seeing the SolarEdge StorEdge system a few years ago that was a DC coupled battery but I thought that battery could only be charged via the solar PV array and not via the grid.

 

[jaggedben]

Do you know of a manufacturer where this is possible? I remember seeing the SolarEdge StorEdge system a few years ago that was a DC coupled battery but I thought that battery could only be charged via the solar PV array and not via the grid.

Definitely SolarEdge. Also Outback and I'm pretty sure Sunny Island. I'm not familiar with Generac (formerly Pika) but I imagine they could too. It is apparently not that hard to run an inverter 'backwards' as a charge controller to charge a battery.

 

[pv_n00b]

If you can charge the battery from the utility many utilities add complexity to the system, or maybe require it to be non-export. They will usually not allow the battery to be charged off-peak and then discharge for export during peak using NEM.

 

[isurf]

If you can charge the battery from the utility many utilities add complexity to the system, or maybe require it to be non-export. They will usually not allow the battery to be charged off-peak and then discharge for export during peak using NEM.

Im talking about charging off the grid during off peak hours and discharging to house loads during on peak hours.

 

[jaggedben]

Im talking about charging off the grid during off peak hours and discharging to house loads during on peak hours.

That doesn't change what pv_noob is saying. It's still an interconnected system and there are rules for that. Could you get away with what you're talking about? I'm sure. Is it strictly legal? Probably not.

 

[GoldDigger]

Either configuration can be used for that purpose. And most PV systems are sized to produce more than is used during daylight hours.

In fact many are designed to produce, averaged over the year, the entire building demand.
And time shifting is exactly what a Tesla Powerwall without PV is used for (in addition to backup). If there is no export, there is little a utility tariff can do to prevent it.

 

[isurf]

That doesn't change what pv_noob is saying. It's still an interconnected system and there are rules for that. Could you get away with what you're talking about? I'm sure. Is it strictly legal? Probably not.

Do you know where to find out if this is legal or not? Is there a state/local law that would dictate this? I would think contacting the utility would be the best route but its hard to get ahold of someone on the phone that would know whenever I call SCE, LADWP or SDGE.

 

[isurf]

In fact many are designed to produce, averaged over the year, the entire building demand.
And time shifting is exactly what a Tesla Powerwall without PV is used for (in addition to backup). If there is no export, there is little a utility tariff can do to prevent it.

This makes more sense to me. With NEM3.0 rolling out in April for certain utilities I think some people will be rethinking how they design renewables systems. It makes sense to me (as long as it's not illegal) to charge up your battery from grid power during the off peak hours and discharge to your house loads at peak hours. I feel like this would possibly even be a good thing for the utility companies; they would be taking stress off the grid by not consuming power during peak hours.

 

[GoldDigger]

This makes more sense to me. With NEM3.0 rolling out in April for certain utilities I think some people will be rethinking how they design renewables systems. It makes sense to me (as long as it's not illegal) to charge up your battery from grid power during the off peak hours and discharge to your house loads at peak hours. I feel like this would possibly even be a good thing for the utility companies; they would be taking stress off the grid by not consuming power during peak hours.

Exactly. In fact in some areas (like Hawaii) the rules for interconnected PV systems include what is essentially a provision for POCO to remotely control export to the grid, making it more desireable to include storage in the design.
With storage systems it can also be possible for POCO to remotely control use of the storage for peak shaving, with export to the grid on command as well as assumption of local loads.