Backup Power

[FlasherZ]

Unfortunately, string inverters are all Tesla Solar uses. If you order the HIS with solar from sunrun that is what they will use in home integration system as well. If it were not for that I might go with Tesla. I want something that will better deal with shadowing due to snow, low lying winter sun, etc. Their prices do beat everyone else though. Enphase has made it clear they are going to support Ford Lightning, Tesla I think has no intention to make Lightning a home backup success, you can't even use a generator with their system without shutting down the home grid. And the Lightning is a 9.6kW generator with a BIG electron fuel tank!

The Delta HIS anticipates solar PV strings if the homeowner wants them active during grid-offline situations. Theoretically, microinverters could be connected on the AC side (the backed-up loads panel) but it remains to be seen how well they can all adjust together to load requirements in an isolated system. I'm looking forward to seeing how well that will work to offer some options.

As I said upthread, it won't be a big deal here - 80%+ of solar installs here are done using string inverters because the inverter cost difference (not price, but cost) is about $3k for an 8-9 kW system, not counting wiring differences that inflate it even more. Where microinverters are used, it's because the homeowner had extra money and liked the idea of seeing how each individual panel is performing, or has unique shading issues due to building azimuth angles (e.g., one particular local homeowner has an east-facing garage roof, the attached 2-story home faces southeast at an angle. In summer, not a problem - in winter, the long shadow from the second story shades the left-most panels). Still, making up the 30 MWh cost difference with microinverters vs. string inverters will take a long, long time.

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[PiMatrix]

The Delta HIS anticipates solar PV strings if the homeowner wants them active during grid-offline situations. Theoretically, microinverters could be connected on the AC side (the backed-up loads panel) but it remains to be seen how well they can all adjust together to load requirements in an isolated system. I'm looking forward to seeing how well that will work to offer some options.

As I said upthread, it won't be a big deal here - 80%+ of solar installs here are done using string inverters because the inverter cost difference (not price, but cost) is about $3k for an 8-9 kW system, not counting wiring differences that inflate it even more. Where microinverters are used, it's because the homeowner had extra money and liked the idea of seeing how each individual panel is performing, or has unique shading issues due to building azimuth angles (e.g., one particular local homeowner has an east-facing garage roof, the attached 2-story home faces southeast at an angle. In summer, not a problem - in winter, the long shadow from the second story shades the left-most panels). Still, making up the 30 MWh cost difference with microinverters vs. string inverters will take a long, long time.

Yes, you are probably right about making up the cost difference although it is not as much as it once was. Some of us E. Eng types would be driven crazy by not knowing the wattage of each and every panel and how it is reacting to snow melt on the roof or shadow from a roof panel as you explain above...or how much it degraded over decades, or not knowing which one went bad without pulling them all off to test each panel. So I have to agree with you on that part! But one thing on Enphase, I have on good word that they consider EVs-as-backup a strategic part of their future strategy, so I'm hoping that with a few firmware upgrades we have a path to actually utilize the Lightning battery in a backup situation for whole home vs a critical load panel. Already a generator input to the Enphase system controller 2 allows you to have a gen run while both solar and battery are both running. And the generator charges the batteries and then shuts off. You can imagine how easy it might be to take the Lightning out put and feed it into a Enphase microinverter all locked into the microgrid! It's these possibilities that are making me lean Enphase. But Tesla Solar string is really attractive as you just can't beat the price but they are kind of hard to work with if you want to do anything different. They seem to be looking at the least common denominator. Well choice is a good thing!

 

[PiMatrix]

There is a more detailed integration document available. By default Sunrun is installing the 4kW version of Delta's inverter. Delta's documentation calls for a device called MID which acts as a transfer switch and requires critical loads to be moved to a separate panel. During on-grid operation, it permits solar feed-in using UL 1741 safety mechanisms. With grid interruption, it isolates from grid and runs the critical load panel only.

Thanks for this explanation. I'm dealing with this exact thing now with sunrun. They just sent me today this picture but I don't see a MID in the layout. The two panels on right are two 200A panels coming from a 320A meter/400A service on other side of garage wall. Trying to figure out what exactly they have planned. I assume E4 is the HIS that hooks to the DC output of the EVSE (Pro charger), and DSB is the dark start battery, and BULP is backup load panel. So where is the 200Amp MID switch? Didn't Ford advertise this as whole home backup? Does Sunrun always use a Backup Load panel or are they just avoiding connecting a MID between the utility box and one of the 200A panels. I realize that 2 panels presents its own issue but I can move all the AC units which are 120A 240V and 50A oven to one panel and it would make the other handle all else. I'd just shut breakers that are not critical or not turn those items on to keep draw less than 9.6kw, but I'd like the choice of deciding that. Sounds like you have seen HIS installs before? Appreciate your insight. Hard getting tech info from Sunrun so far so time to study the manual that has been posted on the forum. Not using the Sunrun string inverters in this setup.

 

[FlasherZ]

In person, I have not seen the specific hardware suite used by Sunrun, but good clues come from the AEE Express site from which you can order the HIS gear if Sunrun doesn't cover your state. It includes a BDI series bi-directional inverter, a 12v20AH battery pack, and a WHB-200 automatic grid isolation switch (a/k/a MID, or "microgrid integration device"). It appears that the MID device could easily fit with the backup load panel footprint (16"x21"x8") in your picture.

The system MUST have a MID device somewhere, because you need something that will disconnect the grid so you don't backfeed power when the grid is out.

Also note the "EVSE device" box in the diagram - this is the DC side only of the FCSP (black lines only). The AC side of the FCSP will also be connected appropriately, likely to a 100A breaker in the grid-only main load panel.

The easiest way to describe this is that anything connected to the "grid" side of the MID gets disconnected on grid failure. Anything connected to the backup side of the MID becomes part of a microgrid supplied by the bidirectional inverter. And code requires an outdoor external AC disconnect that will disconnect the inverter from the MID device.

 

[FlasherZ]

The earlier concern associated with the breaker rating isn't an issue with this design because the main load panel will have a 40A breaker for backfeed, and as long as it's a 200A panel, the code limit for 120% of rated panel capacity won't be exceeded. Even if microinverters are used, they will be moved to tie in on the microgrid-side of the MID, so you won't have grid + 2 separate feed-ins on the main load panel.

The only situation where panel capacity becomes an issue is where a microinverter system exists at more than 10 kW. These systems usually need special designs anyway, and are outside the scope of standard designs... most times they're tied in to the meter base with a completely separate service disconnect to avoid the bi-directional panel issues. But in this home integration system, that will not allow the solar PV system to be used for backup loads during grid failure. Special design work required for that case.

 

[F150LER]

Is it possible to buy a 10kw HIS? Sunrun is not in my area but going Solar.

 

[FlasherZ]

Is it possible to buy a 10kw HIS? Sunrun is not in my area but going Solar.

Delta makes several models of the inverter component, from 4K to 10K.

Note that all models are capable of doing 10 kW in microgrid mode (off-grid), and the difference is how much grid-online solar PV feed-in you might want.

Here's the default package - and it only includes the 4 kW BDI:
https://aeeexpress.com/crs/storeus/browse/productDetailSingleSku.jsp?productId=0000000664#

I haven't talked to anyone who has seen this specific gear already. I'm familiar with Delta equipment as I did a few solar PV installs using Delta inverters. You may be able to call AEE and get them to substitute the E10 instead of the E4.

 

[PiMatrix]

I've heard you cannot buy the HIS on AEEExpress.com that is above 4kW string solar. However it will still feed 9.6kW from the Truck DC to inverter to house. If you want higher solar capacity HIS you have to buy sunrun solar. But there might be other ways to couple AC vs DC as FlasherZ alluded to. Unfortunately getting any HIS now is earliest Nov 1 unless you get it with solar from Sunrun.

 

[PiMatrix]

Neither Ford or SunRun (after 8 calls) can answer the technical questions about how the Lighting can actually be used to power the house, questions like does it have a transfer switch (needed to isolate the backup power from the power company) (yes), does it generate a sine ware and can it be used with an existing PV system (both answers are not clear). Here is what I have found. Per the Ford spec sheet the Home Integration System they are advertising is actually made by Delta Electronics, Freemont CA, 877-440-5851, https://www.delta-americas.com/en-US/index. The truck is limited to supplying about 80 amps, or 9.6 KWH, assuming the E10_BDI is used. Ford's marketing information is based on using 30 KWH per day. The average home without air-conditioning, swimming pools or other major electrical appliances uses 15 to 25 KWH per day. If you have a 200 map main panel, legally the electrical codes will likely require that a sub panel be installed with just the lights and plugs that will match the inverter output capacity. You can't use an 80 amp power source to power a 200 amp rated panel. Given the cost involved of the inverter and installation (starting around $9,600), you might be better off getting a whole house generator that runs on natural gas (around $10,000 to $20,000 installed), then you can power your entire house and charge your truck regardless of weather conditions or the length of time the utility power is out.

Hi Just a few corrections here on the numbers above. The HIS can supply 9,600 watts or 40A at 240V. (80A at 120v). SO that is about 24A coming from the 400A car battery. On the other hand the Pro charger can delivery 80A at 240v to the on-board Lightning AC to DC charger built-in the extended battery (1/2 that for SR battery). So that is 19,200 Watts is the max you can charge using a home charger. That 80A draw requires a 100A breaker in your panel. Of course you can de-rate your charger a bit to fit within your panel capacity. From FlasherZ comments and the online documentation it seems that sunrun wants to supply that 9.6KW to a backup panel with critical loads. Clearly the power to the charger does not come from the backup power, it comes from the main panel. Note, neglecting few percent efficiency losses in above.

One thing should comment here is this HIS does get rid of the issue with Bonded Neutral that one has with taking the 7.2kW from the bed of truck but it certainly is much more expensive way to go. I'm guessing one of the EV charging companies will find a way to do this much cheaper eventually taking the FOrd charger 400V DC out and directly inverting that to an AC microgrid unit without any solar needed. My guess is Enphase will be first to do this and I think it should be at least half the price but that is just a hypothesis. As usual early adopters will pay the price . That being said the HIS should integrate well with Enphase microgrid eventually (or just use the string solar input of the Sunrun/Delta/Ford inverter). But one will have to become the master and the other a slave. Can't have them both not in phase or different frequencies!

 

[F150LER]

I've heard you cannot buy the HIS on AEEExpress.com that is above 4kW string solar. However it will still feed 9.6kW from the Truck DC to inverter to house. If you want higher solar capacity HIS you have to buy sunrun solar. But there might be other ways to couple AC vs DC as FlasherZ alluded to. Unfortunately getting any HIS now is earliest Nov 1 unless you get it with solar from Sunrun.

Yea I’m hoping to save money by just the delta unit and not need another inverters.

 

[FlasherZ]

I'm guessing one of the EV charging companies will find a way to do this much cheaper eventually taking the FOrd charger 400V DC out and directly inverting that to an AC microgrid unit without any solar needed. My guess is Enphase will be first to do this and I think it should be at least half the price but that is just a hypothesis. As usual early adopters will pay the price . That being said the HIS should integrate well with Enphase microgrid eventually (or just use the string solar input of the Sunrun/Delta/Ford inverter). But one will have to become the master and the other a slave. Can't have them both not in phase or different frequencies!

it should be noted that the HIS can be installed without solar - you're not required to use the solar string inputs. Is the cost high? Perhaps slightly, but this is early adopter territory. 10kW string inverters typically run low-to-mid $2,000s for cost today (maybe a bit less expensive for the big big guys). Add the other components (battery & grid disconnect switch), profit, and early adopter tax and it seems about right.

Personally, I'd think Enphase has to do more development work than all the other string inverter manufacturers (Delta, SMA, SolarEdge, etc.) because their inverters are all 25-50V, ~250-350W and they'd be designing a new "big" inverter. The existing string inverter manufacturers just have to get the software right to create the microgrid (instead of just shutting down due to UL1741).

Here's what needs to happen to supply backup power from the system when failure is detected. It's more complex than the typical UL1741 grid-tie solar install:

* Something needs to become aware of the grid failure (MID, above)
* Grid must be immediately disconnected (but still monitored for return) (MID)
* Inverter uses its dark-start battery to establish the power baseline for a microgrid, keeping the system alive to continue all the rest of the steps to get the truck's power online (inverter using dark-start battery)
* Truck must be instructed to wake up, turn on the HV contactors, and supply the battery to the CCS DC terminals if no errors (EVSE)
* Inverter then begins using DC power available from the truck to supply loads from the home and adjusts to maintain proper voltage while monitoring for ground faults (truck must immediately disconnect DC terminals if DC ground fault detected, which is why EVSE plays a role here)
* When grid power return is detected, the grid can be reconnected to the system by the MID and the inverter can begin tapering its supply and disconnects the DC when no longer needed
* Truck recharges via EVSE

As you can see, it's not just as simple as a cheap 400 VDC inverter.

All the other solar PV that's connected (whether Enphase microgrid or some other external system) will use UL1741 to integrate and will work to match frequency and regulate voltage based on load.

 

[FlasherZ]

Yea I’m hoping to save money by just the delta unit and not need another inverters.

You'll probably have to find someone who can sell the units independently (perhaps even AEE) because AEE changed the package specs to supply only the 4k unit. But they will be available in different sizes.

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