Solar and realistic expectations and perhaps a referral

[ggunn]

At the present time, batteries are very expensive vs the grid being cheap.

In many locations you can essentially use the grid as a free battery, but this is very tariff dependent. IMHO this 'free battery ' isn't fair and the tariffs are changing to make things more fair.

Opinions regarding what is "fair" regarding distributed generation and grid storage vary widely, and it largely depends on who you ask and what AHJ's rules apply.

 

[winnie]

The batteries i am using will be Lithium Iron phosphate, witch are able to have a deep dischage and recharge to 80% at least 7000 times witch is about 15 years. They are warranty of 10 years,and can couple 64 together.

Interesting. If those batteries meet spec at that price, and you use them 1x per day at 80% DOD, then you are looking in the realm of 10 cents per kWh. Not bad.

(I did not attempt a detailed calculation including interest rate and effects cost of using partial capacity in order to have improved availability. The number could be 5 cents or 25 cents per kWh. Your money so you need the detailed calc.)

I'll claim I am sceptical, but this makes off grid EV charging more plausible.

Jon

 

[ggunn]

Interesting. If those batteries meet spec at that price, and you use them 1x per day at 80% DOD, then you are looking in the realm of 10 cents per kWh. Not bad.

(I did not attempt a detailed calculation including interest rate and effects cost of using partial capacity in order to have improved availability. The number could be 5 cents or 25 cents per kWh. Your money so you need the detailed calc.)

I'll claim I am sceptical, but this makes off grid EV charging more plausible.

Jon

In most circumstances it's still going to be a lot more expensive than charging the EV from the grid and adding a grid tied PV system to the service.

 

[jaggedben]

The batteries i am using will be Lithium Iron phosphate, witch are able to have a deep dischage and recharge to 80% at least 7000 times witch is about 15 years. They are warranty of 10 years,and can couple 64 together.

It says the warranty is only 5 years. So the cycles guarantee in your application is meaningless (as is usually the case with these battery warranties). You get about 20cents/kWh to store and use a kWh if the battery craps out right after the warranty ends, and it gets better if they last far beyond warranty.

That's actually not bad for a battery, mainly because the price is good. Still, from my point of view, they don't have the track record. At least they're UL listed.

If you're doing your own installation, the cost per kWh for residential solar should come in under $0.04/kWh depending on your solar resource and extra costs to connect to the barn. So if you get paid anything much better than that for exports that don't go directly to the car, then using grid-tied equipment is probably going to be a better deal than batteries.

 

[solarken]

Your friend can't install that Lithium battery in an unheated garage space in PA, it needs to be in conditioned space, out of the extreme winter cold. He should stick with grid-tie, and add battery backup is desired, but put the battery in a heated space. He needs to change his thought process so that he is taking advantage of net metering and grid export, and reducing utility usage in the home, not just charging his EV batteries, if he wants all the benefits of solar.

 

[Mag]

The garage is heated at 50 degrees,it's lithium iron phosphate not lythium ion,(upgrade from company 10 year warranty,it's for the whole house and the garage,grid tie adds contracts and extra cost for epuipment i don't want or need.

 

[electrofelon]

The garage is heated at 50 degrees,it's lithium iron phosphate not lythium ion,(upgrade from company 10 year warranty,it's for the whole house and the garage,grid tie adds contracts and extra cost for epuipment i don't want or need.

What "contracts" does grid tying involve where you are? There is usually an interconnection agreement, but its pretty simple, just a little paperwork. I get about $9400 for a grid tie system comparable to the link in the OP (just panels and inverter).

 

[jaggedben]

The garage is heated at 50 degrees,it's lithium iron phosphate not lythium ion,(upgrade from company 10 year warranty,it's for the whole house and the garage,grid tie adds contracts and extra cost for epuipment i don't want or need.

Grid tie without batteries is less equipment. What would you get credited for exports where you are, and is it export limited?

 

[ggunn]

The garage is heated at 50 degrees,it's lithium iron phosphate not lythium ion,(upgrade from company 10 year warranty,it's for the whole house and the garage,grid tie adds contracts and extra cost for epuipment i don't want or need.

How are you charging the batteries?

 

[tortuga]

What "contracts" does grid tying involve where you are? There is usually an interconnection agreement, but its pretty simple, just a little paperwork. I get about $9400 for a grid tie system comparable to the link in the OP (just panels and inverter).

Yeah it would be interesting to see what the OP's utility incentive or disincentives are. I have herd of utilities charging for very expensive transformer upgrades that would basically kill a project. But in that case he could do a zero export system.

 

[solarken]

The garage is heated at 50 degrees,it's lithium iron phosphate not lythium ion,(upgrade from company 10 year warranty,it's for the whole house and the garage,grid tie adds contracts and extra cost for epuipment i don't want or need.

Lithium batteries no matter the chemistry, can't be charged at cold temperatures. The OP stated the garage was not normally heated. I looked at this kit, and at the EG4 electronics website. I could be wrong, but it looks shady to me. Their standard inverter warranty is 5 yrs, prorated to reduce by 1/4 per year if replacement needed. Similar 5yr warranty on the battery with same proration. I don't see any evidence they meet any of the IEEE or other standards that most common inverters and ESS meet. More common manufacturers do not have this prorated warranty and generally it is common to have 10-12yrs on the inverter and 10yrs on the ESS. Also, a warranty is only as good as the company is strong, and if this outfit doesn't make it in the long term, you may have problems keeping it maintained and operational down the road.
Also, this kit you referenced comes with 11.4kW of PV, and 13kW of inverter capacity, and has 40kWh or battery capacity, or 32kWh or you keep to 80% DoD. The amount of PV is low for this inverter capacity, and for this amount of storage, in my opinion. This leads me to believe whoever put the kit together doesn't know much about off-grid design.
I would highly recommend you ask a lot of questions from the manufacturer before investing $40k on this equipment, and completely understand any limitations it may have. I would worry about inverter issues with phase imbalance, or with surge currents, etc. I don't see this system working out well for powering a whole house and garage, including EV charging and significant loads, without significant lifestyle changes needed during periods of low solar production due to weather and season.
A grid tie, net metered system would be far far less expensive and would not require lifestyle changes. Adding a backup battery for critical loads during outage would be a reasonably priced upgrade.
If you do go down this path, please provide updates here so we can learn from your experience. Good luck!

 

[jaggedben]

I mostly agree with your post, except for...

Lithium batteries no matter the chemistry, can't be charged at cold temperatures.

Well, you didn't define 'cold' but that's an exaggeration. LFP can be charged below freezing if done right. And chemistry definitely matters, LFP does better cooler, NMC does better warmer.

FWIW, the datasheet says they can't charge below freezing, but can discharge down to -4F.

. I don't see any evidence they meet any of the IEEE or other standards that most common inverters and ESS meet.

I did find the UL1741 listing.
Is there an IEEE standard for off-grid inverters? These are off-grid inverters only.

Still, like you, I'm not impressed. Warranty is almost worthless.

 

[winnie]

I've been thinking about this thread for a bit.

One thing that I think is relevant is that the OP really isn't asking about an 'off grid' system. Rather they want to use batteries to maximize self consumption in a grid connected zero export system.

It might not actually be grid connected; there might be a switch so that the EV charger uses the battery or the grid, but the important feature is that you don't need the PV/battery system to provide the near 100% availability of true off grid system. The PV system is used to charge the car, but if PV is not available then the car gets plugged in to the grid.

This changes the economics of the battery because it can be sized to be maximally used, eg. 80% discharge on a daily basis when the sun is shining, and simply not used when the sun doesn't shine.

For a true off grid system you need a battery sized to carry over the load over multiple days if sun is not available. This means a much larger battery. Perhaps 3x battery capacity to enable 20% more kWh from PV.

I'm still skeptical that batteries make sense, but if they do for anyone the OP is probably pretty close to the optimal target.

-Jon

 

[jaggedben]

I've been thinking about this thread for a bit.

One thing that I think is relevant is that the OP really isn't asking about an 'off grid' system. Rather they want to use batteries to maximize self consumption in a grid connected zero export system.

Maybe you're trying to be a little tongue-in-cheek, but that doesn't strike me as a fair description.

The equipment in the OP has no ability to interact with the grid, it's really not grid connected. But I think you know that. More to your point though, 'maximize self consumption' doesn't have much meaning, or at least not the same meaning, when you have a non-interconnected system. The problems the OP faces with the proposed equipment are:
- can't take advantage of solar production when the batteries are full and the EV is not present. That potential production is wasted.
- doesn't seem to have a good mechanism for switching between grid and solar. Can't set it and forget it. Will either miss out on chances to use solar energy or miss out on having a full charge in the EV. I imagine he could set up an ATS but that's added expense etc.

IOW, I don't see this approach as 'maximizing' self consumption, or maximizing anything really.

Of course, it's impossible to say anything definitively without knowing rate schedules and interconnection and metering policies.

 

[ggunn]

Of course, it's impossible to say anything definitively without knowing rate schedules and interconnection and metering policies.

Agreed. When considering any PV system that is connected to the grid, that stuff should be at the top of the list of things to think about. If, for example, there is true unlimited net metering, there is no economic reason to buy batteries. In that situation there is no difference between shoving kWh into a battery or onto the grid except for the cost and energy turnaround losses associated with batteries.

Of course, backup power during grid outages is a different discussion.

 

[winnie]

I absolutely agree that this is not a system that automatically interacts with the grid.

My point is that this is not a true off grid system where the battery needs to be sized to guarantee that power is available 99%+ of the time.

You get home. Due to season and storm the battery is flat. You (manually) run the charger of the grid.

You get home. The battery is at 90%. You (manually) run the charger from the battery.

My hunch remains that the battery is not really the best investment, my point in this post is just that if you only need the battery to have sufficient capacity say 80% of the time you can use a much smaller battery and therefore see a better levelized cost per kWh.

-Jon

 

[ggunn]

I absolutely agree that this is not a system that automatically interacts with the grid.

My point is that this is not a true off grid system where the battery needs to be sized to guarantee that power is available 99%+ of the time.

You get home. Due to season and storm the battery is flat. You (manually) run the charger of the grid.

You get home. The battery is at 90%. You (manually) run the charger from the battery.

My hunch remains that the battery is not really the best investment, my point in this post is just that if you only need the battery to have sufficient capacity say 80% of the time you can use a much smaller battery and therefore see a better levelized cost per kWh.

But for a net metered service, what would be the point? Whatever you spend on batteries is a net loss.

 

[winnie]

With pure net metering, the grid is a free battery. Any purchased battery costs more than free.

With the actual tariff structure we don't know how much it costs to use the grid as a battery.

Perhaps @dm9289 will chime in with the rate structure being dealt with.

-Jon

 

[wwhitney]

. . . true unlimited net metering, there is no economic reason to buy batteries.

With pure net metering, the grid is a free battery.

Not for a TOU plan. The surplus kWh you send to the grid at one time of day may be valued less than the kWh you draw back from the grid at another time of day. That makes it a non-free battery. And so depending on the details, a purchased battery could save money.

Cheers, Wayne

 

[jaggedben]

I absolutely agree that this is not a system that automatically interacts with the grid.

My point is that this is not a true off grid system where the battery needs to be sized to guarantee that power is available 99%+ of the time.

You get home. Due to season and storm the battery is flat. You (manually) run the charger of the grid.

You get home. The battery is at 90%. You (manually) run the charger from the battery.

My hunch remains that the battery is not really the best investment, my point in this post is just that if you only need the battery to have sufficient capacity say 80% of the time you can use a much smaller battery and therefore see a better levelized cost per kWh.

-Jon

Actually I think it's been unclear from the OP if there exists or is a plan to bring utility power to the garage or not. There was mention of going the other way, i.e. bringing the solar/battery output to the house as a backup. But unless I missed it there was no mention of bringing utility power to the garage. If the idea was to avoid the cost of trenching to the garage, then that changes the economic calculus. But of course the stand-alone system won't be as reliable on its own.