AC coupled batteries with enphase micro-inverters

[Mike90250]

so, now I'm on a research mission to see what can be done with 11kw of enphase inverters currently on the roof. My task is to find a way to keep a commercial kitchen powered in a bare bones 6 day long planned grid outage (Pac Gas & Elec infamous "public safety power shutdown") scenario. We were caught up in one last month, 5 days, tons of spoiled food, no heat....... and are told to expect 10 more years of them (here in sunny northern california)

So, what AC coupled options exist either now, or near future, for batteries and inverters that play with enphase ?

link attached for their older app note setup. Anything newer / better in the pipeline ?

https://enphase.com/sites/default/files/Enphase_Application-Note_AC-Coupled-Battery-Based-Systems.pdf

[bcroe]

Sounds like mission impossible, without a generator. 10 years is so everyone will have
either forgotten about reliable power, or died. Bruce Roe

[peatmoss]

Enphase is coming out with IQ8 and microgird. They currently have storage batteries but they are expensive https://enphase.com/en-us/homeowners-storage-solutions What version of inverters do you have?

[JSchnee21]

Assuming all of your cooking is natural gas or propane, main electrical usage should be primarily HVAC & Walk-ins, correct? On Sunny days what percentage of consumption is your 11kW array after to offset? Commercial HVAC and chillers / freezers use a lot of power. Is the climate such that you can operation without HVAC? Will customers be comfortable?

In general, though, I agree with @bcroe I would seriously consider a nice 1800 RPM liquid cooled natural gas generator instead. Likely much cheaper on the CapEx front. But, on the OpEx size, burning that much natural gas gets expensive after a day or two.

Like this one for $11K

https://www.electricgeneratorsdirect.com/Generac-Protector-RG02724GNAX-Standby-Generator/p15955.html

Fully installed (pad, gas line, meter, ATS, permits?) you're probably looking at $~$18K-$20K.

[Mike90250]

Thanks guys. Yes - the freezers and walk-ins take a huge amount of power and neophytes won't be able to manage the system, of what they can and cannot use. Additionally, there are 3 meter drops to the building, loads have been added over the last 90 years (coming up on the 100 year anniversary of the building.) All the cooking is gas, but needs power for the high speed circulating gas oven, gas fired tankless water heater (electric spark), and the 180F thermal booster for the dish sanitizer, exhaust fan in the kitchen and some lighting, figure about 9kw to power it up in a minimal configuration. That would suck any affordable battery dry in a couple hours. They don't want to hear the G word.

[SunEagle]

Thanks guys. Yes - the freezers and walk-ins take a huge amount of power and neophytes won't be able to manage the system, of what they can and cannot use. Additionally, there are 3 meter drops to the building, loads have been added over the last 90 years (coming up on the 100 year anniversary of the building.) All the cooking is gas, but needs power for the high speed circulating gas oven, gas fired tankless water heater (electric spark), and the 180F thermal booster for the dish sanitizer, exhaust fan in the kitchen and some lighting, figure about 9kw to power it up in a minimal configuration. That would suck any affordable battery dry in a couple hours. They don't want to hear the G word.

I agree that if you have a large load a propane generator will still provide enough power for much longer than a costly large battery system. Sure fuel may be hard to find but so will batteries of the Ah rating of a large system. Either way you may be SOL for a long duration power outage.

[JSchnee21]

Well, I don't think larger scale fuel cells are financially viable yet. And Bloom is a bit of a Unicorn. There seem to be a number of smaller fuel cell companies in Canada, but they are using bottled hydrogen rather than natural gas. And most seem to be < 5kW.

Unless you have a lot of space to scale up your PV field and a lot of money for high density energy storage, the only two options are to shutdown or invest in a genny, Of course, investing in a generator is only helpful IFF you can continue to process transactions (POS), take reservations (phone/online), get grocery deliveries, and have customers in the area who want to and think to come to a black out zone for dinner.

Actually, thanks to Fracking, running the genny is cheaper than ever. For the one I referenced:

197 ft³/hr @ 50% load (~12.5kW)

197 ft3 / 96.7 ft3/therm = therms 2.037 therms / hr (@ 50% load)

at $1.323 / therm

$2.694951 / hr

$64.68 / day -- that's a fantastic price actually -- seems too good to be true. That's probably less than your electric bill.

[nwdiver]

Have you looked into a large Magnum Energy system? You could probably get a 16kW AC coupled system for <$10k.

[dalek]

so, now I'm on a research mission to see what can be done with 11kw of enphase inverters currently on the roof.
So, what AC coupled options exist either now, or near future, for batteries and inverters that play with enphase ?

There will be more DC Solar trailers going up for auction, I just brought one home. https://www.cagp.com/past/ At the Vegas speedway, there looked like maybe 500 more to go, once they figure out ownership of them.

They have a pair of SMA SI6048 inverters that together can do 240v split phase, 12kW continuous of output, as well as accept up to 12kW from AC coupled inverters to charge battery. So the microinverters could go behind the inverters along with your loads.

The older enphase microinverters don't have a gentle throttle down with ac frequency, like the SMA Sunny Island will do with other SMA solar inverters. There are programmable relay outputs on the SunnyIsland based on SOC can shut off individual strings of the enphases, to prevent overcharging a full battery. Midnite solar has complete panels for the SunnyIsland inverters, and they (used to?) have a relay board to do this type of task. https://youtu.be/fl_OJyLvrAI?t=569

[Ampster]

Back to the original question you posed. What vintage are the Enphase micro inverters? That is important as dalek mentioned to see if it would be practical to even try to AC couple them. Depending on their response time will determine how much battery capacity you would need as a buffer. It would be nice to be able to utilize that solar on the roof during one of PG&E's public safety power shutoffs but the cost of hybrid inverters and batteries has to be compared to the cost of installing a generator or the cost of renting an emergency generator. My local market and the bakery across the street did just that in Glen Ellen in Sonoma County but they did not have the advantage of solar on the roof.

I think the public outrage from these power outages is going to cause PG&E to evaluate their grid shutdown strategy. They have to make some changes in their substation switching so that not so many people are affected. I recently attended a Sonoma Clean Power meeting and they talked about a study they did with PG&E to determine that a small expense in rearranging the grid topology would mean they would not have to shut down the power to a large senior retirement community during the next PSPS near Santa Rosa. Mendocino County participates in Sonoma Clean Power. The point about seniors was that there were a lot of people in that community that were on life support systems that needed power and that got some politicos attention.
My thought is that a multi prong approach might be the most productive and cost effective.