let's talk about battery banks- I reckon the "they aren't worth it" thing is wrong

Status
Not open for further replies.
jaggedben said:
To each his own, but personally I have no problem conceiving of the battery's LCOE as being either positive or negative, depending on the effect on the overall LCOE. As I said earlier, that LCOE can only be negative if there's a significant difference between POCO charges and credits.
Click to expand...

The problem, as I see it, is that the whole notion of adding up two LCOE figures to get an actual LCOE leads to fuzzy thinking. There can be components of an LCOE, but the individual components are not LCOEs.
This may be part of why comparing the "battery LCOE" to the POCO price is so compelling to PVFarmer.
 
GoldDigger said:
OK, so you have an LCOE for directly used PV and an LCOE for PV generated and stored before use.
The difference between the two is what the batteries contribute to the LCOE of the latter option, even if you do not call it the LCOE of the batteries.
I think that is really a safer way to think of it since it removes the misguided temptation to compare the battery "LCOE" alone to the POCO rates.

And as long as there is no NET surplus at the end of the year, for most users it is perfectly reasonable to think of running the meter backwards as selling.
If there is a NET surplus at the end of the year, it would not have gone into the batteries and come back as useful energy either. :angel:
Click to expand...

And then there is the "value of solar" as Austin Energy figures it. AE doesn't have Time Of Use (TOU) charges or demand charges for residences, but they do have tiered pricing based on consumption. Instead of net metering, they meter the energy you consume from the grid as well the energy you produce from your PV system, and they charge you your tiered rate for all of it. Then they credit back to you for the energy you produced at the flat value of solar they establish for everyone. This is an effort to make solar worth the same per kWh for everyone irrespective of how much energy they consume. It also renders batteries irrelevant.
 
Last edited:
Batteries are the source of the power that you aren't "buying" from POCO at night.
The cost from POCO at night (and at all times, except for the future) is a given, the cost of the batteries is not, until you calculate it somehow.

Now that I've typed BATTERIES over a hundred times I get why people call them BESS instead!

So what do you call the cost of the power taken from the BESS?
You can't just say "the BESS cost $200/kWh installed"- that says nothing about >how much power it put out / for how many cycles<.

If you look at it that way, your PV LCOE withOUT BESS only tells you "it cost X and produced Y amount of power", nothing about what the POCO price happens to be.
And your LCOE with BESS (my way) is also mssing that same POCO price factor.

So if:
LCOE of BESS = cost of BESS components (in cents) divided by (kWh * cycles * %efficiency of BESS * %DOD).
then see: >>>

Side note: Still not sure about that DOD factor there...seems like it would just be 100%, or *1, and not matter, if you've already decided "the BESS will be discharged 22% a night".
Because you are getting your amount of cycles from the mfg.'s chart...Peukert cycle and all...the curve at 22% = x cycles? :blink:
No reason to multiply by 1 as a DOD factor then?


>>>
You call the cost of power from BESS...
LCOE of PV plus LCOE of BESS....and subtract the missing link....the POCO price!

Now I'm repeating myself and expecting a different result- call a psychologist! :happyyes:
 
PVfarmer said:
1 If the LCOE was more than the price you were getting for selling the energy it produced, there would be no reason to do it, so they are related. "How" is the question.
Click to expand...
That logic would apply to whether or not to install more solar panels. That wouldn't apply to whether or not to install batteries, given a fixed size installation of PV panels.

PVfarmer said:
3 Whoops! Your "daytime sell price" isn't just how much the POCO pays you- it costs you the LCOE/kWh to produce it.
Click to expand...
Once you've bought the solar panels, they are a sunk cost. You're never going to see that money again [ignoring the option to uninstall and sell the solar panels]. It has no bearing on the economically efficient way to use those solar panels going forward.

So the LCOE of the solar panels doesn't enter into it. From that point forward, you can treat the solar energy as have 0 marginal cost in deciding what to do with the energy produced. Of course, in the accounting for the whole project, you have to consider the solar panel cost and make sure not to install more solar panels than you need.

PVfarmer said:
5. I think what might be happening is we aren't defining who net metering and/or batteries are "good for", while trying to discuss both.
Let's focus here- do you agree with this: net metering is only good for the person/company not trying to "make money" directly from net metering, ie- a homeowner who wants no bill and a longer payback period OR a PPA company/developer/installer who is making their money off of something other than a zero bill?
Click to expand...
Yes, I'll agree with that. I would say 99% of the comments in the thread so far are in the context of someone who has sized their solar system to produce less energy over the course of a year than they use over the course of the year.

If you want to discuss installing solar panels to be a net year round generator of electricity, as your username suggests you may wish to, then when is it economically feasible? My utility pays a very small amount for any net generation of energy over the course of year, on the order of $0.04/kWh as someone else suggested. Can the LCOE of your solar panels be lower than that?

Cheers, Wayne
 
ggunn said:
And then there is the "value of solar" as Austin Energy figures it. AE doesn't have Time Of Use (TOU) charges or demand charges for residences, but they do have tiered pricing based on consumption. Instead of net metering, they meter the energy you consume from the grid as well the energy you produce from your PV system, and they charge you your tiered rate for all of it.
Click to expand...
Wait, they separately meter your usage and your total PV production, charge you a tiered rate on the usage, and pay you a flat rate on your generation? So you are not allowed to use your PV generation locally to offset your usage? Unless the PV payout rate is higher than the highest usage tier, that seems out of whack.

Cheers, Wayne
 
ggunn said:
Instead of net metering, they meter the energy you consume from the grid as well the energy you produce from your PV system, and they charge you your tiered rate for all of it.
Click to expand...
They charge you for what you produce? :)
Sounds like a Power Purchase Agreement to me.
 
wwhitney said:
If you want to discuss installing solar panels to be a net year round generator of electricity, as your username suggests you may wish to, then when is it economically feasible?
Click to expand...
Suppose this is your situation, and you don't have net metering, so whenever you are instantaneously generating more electricity that you are using, you get a POCO refundable credit of, say $0.15/kWh, and whenever you are consuming electricity from the POCO it costs you, say, $0.25/kWh. Now suppose your LCOE for PV is less than $0.15/kWh, and so you want to be a PV farmer and install lots of PV and be a net generator. Should you install batteries?

In this case the answers you have been given still apply, and the answer depends on average cost/kWh of battery storage (I'll call that LCOS for levelized cost of storage). With your excess daytime generation you can either:

(A) sell your excess daytime generation at $0.15/kWh
(B) pay the LCOS to put the energy in batteries and use it to avoid $0.25/kWh in nighttime usage charges

So in this example, if your LCOS is less than $0.10/kWh, it is worthwhile to install batteries. The efficient size of the batteries is determined by your nighttime consumption, they are only economic to the extent you are displacing your nighttime consumption while using a reasonable DOD to keep your LCOS low.

Note that this is still an example of the formula many people have given you, that batteries are economically worthwhile when:

POCO sell < POCO buy - LCOS

Note that the PV LCOE doesn't enter into this.

Cheers, Wayne
 
wwhitney said:
Wait, they separately meter your usage and your total PV production, charge you a tiered rate on the usage, and pay you a flat rate on your generation? So you are not allowed to use your PV generation locally to offset your usage? Unless the PV payout rate is higher than the highest usage tier, that seems out of whack.

Cheers, Wayne
Click to expand...
That's the way it works, and presently the VOS is 10.7 cents per kWh. To their way of thinking, solar should not be worth more to you than to someone else just because you use more energy.
 
wwhitney said:
Yes, I'll agree with that. I would say 99% of the comments in the thread so far are in the context of someone who has sized their solar system to produce less energy over the course of a year than they use over the course of the year.
If you want to discuss installing solar panels to be a net year round generator of electricity, as your username suggests you may wish to, then when is it economically feasible? My utility pays a very small amount for any net generation of energy over the course of year, on the order of $0.04/kWh as someone else suggested. Can the LCOE of your solar panels be lower than that?
Click to expand...

Ok! Cool.
Now- don't you want to know if YOUR solar panels can be lower than .04? You didn't mean "your" as in mine, but did you mean "someone's" or your own PV there where you are?
Sorry, I've lost track- you are from Cali, correct?
I could answer "quite probably, IF" or "definitely, WHEN", but it even makes a difference if you mean Arcata or San Diego. (I've spent time out there, great state!)

Plus there are another undefined amount of factors which matter.
Latitude first of all. On the roof or on the ground? Average kWh usage a month? Is there a limit on the $.04 thing, as in can the PV output = twice your usage? I'd guess yes on that last one.

You'd most probably have to go by wholesale or at least single pallet prices for panels.
Paying cash up front? Borrowing half? Your neighbor happens to be a ME and owes you a favor?
The added cost of the building permits/contractor etc if roof mounted makes it tougher of course...unless it's a flat roof and you go with non-penetrating mounts....

The first three questions are enough to say for sure re:your scenario if you want me to- it'll take 10 minutes or so to run it through SAM.
 
PVfarmer said:
Now- don't you want to know if YOUR solar panels can be lower than .04?
Click to expand...
I'd settle for a typically sunny place in California. I'm on a 5000 square foot lot and already have my southern roof exposure covered with PV panels, so I don't really have any space for expansion.

PVfarmer said:
Plus there are another undefined amount of factors which matter.
Latitude first of all. On the roof or on the ground? Average kWh usage a month?
Click to expand...
Average kWh usage doesn't enter into LCOE.

Cheers, Wayne
 
ggunn said:
That's the way it works, and presently the VOS is 10.7 cents per kWh. To their way of thinking, solar should not be worth more to you than to someone else just because you use more energy.
Click to expand...
So what are the tiered rates for usage? Seems like this rate structure could create an incentive to go off grid during the day, using a transfer switch, an off grid inverter, and some batteries.

Cheers, Wayne
 
wwhitney said:
So what are the tiered rates for usage? Seems like this rate structure could create an incentive to go off grid during the day, using a transfer switch, an off grid inverter, and some batteries.

Cheers, Wayne
Click to expand...
Not really. If you have enough usage to drive you into a high tier, then building an off grid system that would keep you comfortable during the day in Central Texas would be hideously expensive.
 
jaggedben said:
No they are not. The PV is.
Click to expand...
More than that, a Sunny Island when it is charging its batteries takes the power from the AC bus which carries power from the PV inverter to the grid, so the electrons flowing into the batteries could come from either the PV or the grid. The SI doesn't know or care where it gets them.
 
ggunn said:
More than that, a Sunny Island when it is charging its batteries takes the power from the AC bus which carries power from the PV inverter to the grid, so the electrons flowing into the batteries could come from either the PV or the grid. The SI doesn't know or care where it gets them.
Click to expand...

Well, exactly. Whatever you 'aren't buying' from the grid, you are getting from the PV, and vice versa.
 
So! If you can do as much of the work yourself as possible...as in drive to a warehouse and get the panels wholesale, etc.
I didn't even use this preposterously low price. -> http://sunelec.com/solar-panels/hig...sun-395-watt-monocrystalline-solar-panel.html
I'll admit, I did use very low overhead costs.
This is with a 6,000kWh per year electric bill, net metered, .04 "payback" rate.
BUT! Check out the exact same everything, but with the system in ABQ, New Mexico...

Sacramento Airport weather:
Metric // Value
Annual energy 21,075 kWh
Capacity factor 18.6%
First year kWhAC/kWDC 1,628 kWh/kW
Performance ratio 0.80
Battery efficiency 0.00%
Levelized COE (nominal) 5.06 ¢/kWh
Levelized COE (real) 4.01 ¢/kWh
Electricity cost without system $780
Electricity cost with system $-463
Net savings with system $1,243
Net present value $10,087
Payback period 6.8 years
Net capital cost $12,683
Equity $0
Debt $12,683
---
ABQ airport

Metric // Value
Annual energy 23,629 kWh
Capacity factor 20.8%
First year kWhAC/kWDC 1,826 kWh/kW
Performance ratio 0.78
Battery efficiency 0.00%
Levelized COE (nominal) 4.52 ¢/kWh
Levelized COE (real) 3.57 ¢/kWh
Electricity cost without system $780
Electricity cost with system $-570
Net savings with system $1,349
Net present value $11,858
Payback period 6.1 years
Net capital cost $12,683
Equity $0
Debt $12,683
 
ggunn said:
Not really. If you have enough usage to drive you into a high tier, then building an off grid system that would keep you comfortable during the day in Central Texas would be hideously expensive.
Click to expand...
You wouldn't necessarily need to. You could use some batteries and toggle on and off grid as needed.

I was just wondering if this "everyone get the same credit for all PV production" rate regime also regulates going off grid via a transfer switch.

Not that it would be economical, I just looked up the Austin, TX rates and your highest tier is a total cost of $0.1684/kWh. That's cheap compared to California.

Cheers, Wayne
 
Status
Not open for further replies.
Top