120% System installed

[ericstott]

I have a 120% system, a 14kw solar grid tied system.
So I NEVER have an electric bill (well, okay $11.50/mo for the service fees).
But I am producing TONS of extra power from my system. I bought a Fiat500e and power it DAILY. (24kwh battery)
I live in Phoenix AZ with APS power. Grandfathered payment system. 2008 it was installed.

Still, even at that, I NEVER go over and actually pay for electricity. (Well, except when the house gets struck by lightning and the fuse needs replacing - happened twice!)

I would like to add battery backup, but I don't want to have to buy TWO Tesla powerwalls to charge it.

I am NO ELECTRICIAN, but have been watching a bunch of the videos from Will Prowse.

Any ideas?

 

[svetz]

How big is the battery in the Fiat500e? That's what I'd like to do someday. V2H is the technology, but it's not readily available yet. Will does have a video on how to get emergency power from his Tesla.

I suspect the issue is marketing folks think people want their transport charged, not use their transport to power their house in emergencies ... so no one is rushing to do it.

 

[ericstott]

How big is the battery in the Fiat500e? That's what I'd like to do someday. V2H is the technology, but it's not readily available yet. Will does have a video on how to get emergency power from his Tesla.

I suspect the issue is marketing folks think people want their transport charged, not use their transport to power their house in emergencies ... so no one is rushing to do it.

It is a 2016 so it is a 24kwh battery. (ya, I know the 2020 model is a 42 kwh - which I am jealous)
I already have a 24v wall charger Juicebox 40 amp charger mounted in the garage.

 

[ericstott]

How big is the battery in the Fiat500e? That's what I'd like to do someday. V2H is the technology, but it's not readily available yet. Will does have a video on how to get emergency power from his Tesla.

I suspect the issue is marketing folks think people want their transport charged, not use their transport to power their house in emergencies ... so no one is rushing to do it.

I am not interested in V2H - geez, I produce more electricity from my solar system than I can use anyway.

 

[Hedges]

What grid-tie inverter do you have? Some are compatible with some battery inverters.

V2H - actually, a good idea. There is your battery backup.
Only question is, can you run V2H and still operate the PV inverters?

Some Power Wall or Sunny Boy Storage systems only work while the grid is up. They shift your power consumption around.
Needs to have a transfer switch to isolate utility grid and form a local grid.

Some battery inverters work like a UPS, so whatever part of the house you attach to them stays up.

My system is:
Utility grid <--> Sunny Island with battery <--> Sunny Boy Grid Tie inverter and house loads.

Because this is AC coupled, battery can be small. I have a 20 kWh AGM which cost $5000 but could be 5 kWh for $1250 if I didn't try to run four refrigerators all night.

 

[ericstott]

There are two Sunny Boy converters made by SMA.
It was installed in 2008 and I 'think' it only works while the grid is up. If more detail is necessary: please ask.

I would like to power things like my freezer, refrigerator, and lastly charging the car if the grid goes down.

Is there a way in which to do that?

 

[Hedges]

Which model Sunny Boy?

Many of them are supported by Sunny Island, which I have. That uses 48V lead-acid or lithium batteries.

https://files.sma.de/dl/7910/SB-OffGrid-TI-US-en-21.pdf

Discover the Sunny Island 4548-US / 6048-US! | SMA America

The efficient island manager Sunny Island 4548-US / 6048-US ► Now with 20 % more power! ► Efficient, simple, flexible and durable! ► Check out now!

www.sma-america.com

Some would work with the newer Sunny Boy Storage, which uses 400V lithium batteries. Also need "automatic backup unit", a transfer switch and transformer, to run off-grid. Otherwise, just for shifting when power comes from/goes to grid.

Sunny Boy Storage 3.8-US / 5.0-US / 6.0-US | SMA America

Discover the flexible Home Energy Solution: The SMA Sunny Boy Storage 3.8-US / 5.0-US / 6.0-US battery inverter! ► Find out more about its benefits!

www.sma-america.com

Newer Sunny Boy also have battery-less operation off-grid for 2000W max, manually enabled.

 

[ericstott]

For the West side I have the SB 5000US, for the East side I have the SB 7000US and I stand corrected, it was installed in 2010.

 

[Hedges]

Those models should play with with Sunny Island. If you got a pair of SI6048, Sunny Boy could backfeed through Sunny Island relays. Any loads you put on the output of Sunny Island could be powered by PV, battery, and grid. Limit of 56A 120/240V can come from grid.

You have to rewire some (or all) loads if you want automatic backup. Alternatively, only put Sunny Boys on output of Sunny Island and add a breaker interlock to your panel, as you would for manual transfer to a generator backfeeding the panel.

This seller apparently got several of these units from DC Solar auction. Other, including bare inverters and complete trailers, are on the market too.

2x SMA Sunny Island Inverters, Charge Controller, Load Centers pre-installed | eBay

Complete inverter system pre-wired, ready to install. You will not find a system easier to install. It is as simple as plugging a solar array into the existing plugs, a battery bank into the existing Anderson connector, an AC power source (grid/generator) into the twist lock connector and...

www.ebay.com

That unit plus a battery would pretty much do it.
One more thing you should add is a 2-pole relay with 48V coil. If battery DoD gets to 70%, Sunny Island lets go of the relay and your house goes dark, but it keeps AC going to Sunny Boy so batteries get charged again. House reconnects at 50% DoD.
One other way to automatically recover: That unit comes with DC charge controllers. Add PV panels for them, and those will recharge battery. Just a lot slower compared to your 12kW of AC coupled PV.

Sunny Boy Storage + Automatic Backup Unit might also work, but I haven't looked into what non-current Sunny Boy work with it.

I think the bargain Sunny Island which came from DC Solar bankruptcy, together with a 100 Ah 48V AGM battery and a load-shed relay, would be cheaper and better than the Sunny Boy Storage. It is limited to 6 kW from battery and doesn't have the massive surge capability to start motors.

One parameter you have to change is battery charging current. SMA says to have 100 Ah per 1 kW of PV, which would be 1200 Ah. With a much smaller battery, you need to set charge current to 10A or 20A (0.1C or 0.2C for 100 Ah), because their default configuration sets it to 0.55C.

 

[Hedges]

Yes, there are much cheaper ways to go and I did that in the past.
Where I am (Silicon Valley) it is easy come, easy go.
When property tax man takes $1000/month and water bills for my 1 acre hit $500/month in the summer, "A grand here and a grand there" on some toys like a system to run the air conditioner and everything else during scheduled power failures isn't such a big deal.

I'm quite happy now with my over priced, under sized house on the hill bought 20 years ago. My garage is bigger than my house. My pool is bigger than my house. A 1 bedroom apartment in the area now costs as much as my PITI (principal, interest, taxes, insurance)

There are half a dozen tech companies here where the median salary is > $200k. Median, half the employees make more.
But I do well enough having my expenses below average for the area. And sometimes I splurge on something I don't really need.

 

[Hedges]

"Overclocking" or over paneling - my approach is to parallel two arrays oriented 90 degrees apart. Peak output according to geometry (ignoring how light reflects off angled glass), is 70% as much as all oriented the same. So staying within your 5 kW limit you can export about 50% more kWh during the day. Passive "tracking".

One could also bank excess production in a battery and backfeed it later (typically done here if rate schedule triples price in the evening), but to me the cost of a battery per kWh cycled through it in its lifetime is too high. I figure a kWh through my battery costs $0.50 or $1.00, but a kWh from PV costs me $0.05, so I only use batteries as a convenience/luxury. Some lithium batteries, especially DIY, are getting to where one can win playing arbitrage between $0.15 and $0.45/kWh rates. I just don't see it as worth my time and money. Instead, give them three kWh that cost me $0.05 each in the morning, get one kWh back in the evening.

 

[Hedges]

Sure, I'd be a lot richer if I took my dollars to your neighborhood and spent them there. Each in our own neighborhood, we're doing equally well. It is just on "imported" goods like PV panels and inverters where I have the advantage. But I have to pay for the over-promised pensions of local government employees. I once thought I would retire elsewhere, cheaper. But I think I'll be able to stay here.

Previous employer once told me that just two of us engineers cost the company as much as their entire staff of 30 in Bangalore. 10 of those were interns, but the rest were regular employees. So an engineer there was 1/10th the cost of here. That's one of the reasons I spent my own money on my own lab equipment - making sure I was delivering results they couldn't get elsewhere.

One month I got a power bill for $2000. Looking at the details, it said I drew an average of 400A all month long during peak times (Noon to 6:00 PM), then returned almost all the power off peak. PG&E tested the meter and said it was working correctly. I pointed out it wasn't possible to pull 400A through 200A service without overheating the cable. Obviously just a bit-flip somewhere. There had been solar storms. PG&E adjusted the bill. (total consumption was similar to previous month, only how much when had changed.)

A single 5 kW inverter would keep you within the limit, but under by whatever you consume. A system that measures export and adjusts production to hit a target would let you make 100% of your consumption plus export the limit. Not sure which would give you the simplest, cheapest way to do it. The "AC Battery" inverters support zero export and time shifting applications, might also support targeted export. But those are newer and not on the surplus/closeout market yet.

Oh, and health insurance (which is mandatory now) costs about $12k/year for a policy which covers you. Or, $6k/year for a policy which doesn't cover anything until you've spent $6k out of pocket. Fortunately this is paid partially/fully for people with employers (and free for people without money), but the self-employed and under-employed are required to pay for it.

 

[ericstott]

The number of panels are different, which is why I have a bigger inverter for the east facing (right side of the pic) versus the west.

 

[ericstott]

I take it 120% means 20% more panel output than inverter capacity?
Here all new systems are 33% overclocked to get the most out of the inverters. You are only allowed 5Kw backfeed in the majority of areas on single phase and the overclocking is to account for inefficiency and some use by the home.

I have done my own systems and run around 150%. My goal is to get full capacity out of the inverters in winter. Summer I make stupid amounts of power. Had a meter read in early September, 1 Month on and I was 1000Kwh in reserve. Shut down all my solar and still trying to burn it off. When summer proper comes that will be OK as we will be running the big ducted ac but now we are only using about 30 Kwh a day so it's taking a while to come down. Have another meter read early December so should get there by then and the weather will have warmed up in between.
I have a spare hot water heater I use to boil water with. I use that to kill the weeds around the garden without using any chemicals and it's obviously a LOT cheaper as well. Burns off good amounts of power as a Bonus.

Batteries are a total waste of money for a grid tied system for a cost saving POV as well as a Backup POV.
How often you get blackouts and for how long? You would be far better off using the right tool for the job which is a generator. Cheaper, will provide power for a day, week or month and never run out and you could charge your car from it if you wanted although I'm sure you have an IC as well.

Also -IF- you do it right, and many whom are not aware and just parrot what they read will incorrectly tell you you can't, you CAN use a generator to Power up your solar. There are ways you have to do it in sequence and follow certain parameters BUT, it is perfectly doable and I have done it myself . This enables you to get more power than using one alone although you can have the solar doing the bulk of the grunt work and the generator with the light end of the load just providing reference frequency basically which saves fuel and wear and tear.

Start of the year when all the unfounded BS about the China pox was scaring everyone, as it did me, I set up a couple of little dinky systems with spare panels, inverters and batteries to power the fridges. I have a generator that would power everything in my house and the neighbors either side and then there is the smaller one but powering fridges is a pain.
I hooked the panels to a charge controller on a car battery and was going to use that to run the fridges. Matter of fact the test rig I set up for the outside fridge ran for about 4 Months till the mrs wanted it off the back patio. The other one is still sitting outside the kitchen but hasn't been needed.

A backup system like that would be a lot smarter than something to power the house. You don't need a big battery, if you put plenty of panels on plenty of charge controllers that will meet the inverter demands, the battery mainly acts like Ballast and you can run whatever up to what the input from the panels is at the time.

If one were merely running a fridge off solar, the idea would be to fill any free space with water or better still Ice bottles so the thermal mass was greater. Freeze the water through the day when the sun is powering the fridge and put them in the fridge in the evening. that will keep it plenty cold though the night when the genny is shut down.

Batterys are a VERY expensive way of achieving blackout protection especially if it's infrequent and for short periods.

120% means, when they evaluated my system, they (the PV installers) recommended getting an 80% system. I told them 'no, I want to buy a system that will power 120% of what I currently use.'

 

[Pyrofx]

Hedge actually has some of the cheaper rates for the area. My buddy in Saratoga " right next door " is double to triple. Paid for the 40k$ well in 2.5 years.
The bay area is great to live in , but tech has priced it out of touch for newcomers.