14.4KWH !! What does it all mean?

[John Frum]

Have a look at something like this

Vue Energy Monitors - Emporia: Revolutionizing Home Energy

Turn insights into savings. Connect an Emporia Vue Energy Monitor directly to your circuits to automate, manage, and control your home’s energy.

www.emporiaenergy.com

or similar.

See my signature for a useful tool to help with the energy audit.
We can't do it for you.
Besides this is the DIY site .

 

[Catsassend]

Thank you. I have downloaded the file. I am going to do some figuring.
Once I figure out what my requirements are. Do I match my requirements to the solar panels or the batteries? Do I get my power from the batteries all the time?

 

[John Frum]

Do I match my requirements to the solar panels or the batteries?

Your batteries have to cover 1 day's use.
Your solar panels need to replenish that usage.
The batteries are like a bank account.
The solar panels are like income.
The loads are like bills.

Do I get my power from the batteries all the time?

See above.

 

[Hedges]

This is the system I am looking at purchasing next week. I have been told this is a 14.4KWH capacity. My daughter killed 1700 kwh in the 28 day month in January while we were away, but that is not the norm for us since we always heat with wood. Am I correct in saying that 60KWH/day?! and that that is what we would require under that load, and that the 14.4kwh that I was quoted for this solar system would not cut it?

Putting in PV to generate 60 kWh is not unreasonable, at least in summer. In winter and up north, takes more (like 30 kW of panels) but doable.
Batteries to provide 60 kWh, or 180 kWh for 3 days without sun, is getting a bit ridiculous.

Did this happen before you had an alternative energy system with PV panels and batteries?
If you have grid power, why are you considering batteries? They are OK to backup small critical loads, but not for heating.

Does your utility offer "net metering", where you can bank kWh during the summer and use them in winter?

 

[Catsassend]

Putting in PV to generate 60 kWh is not unreasonable, at least in summer. In winter and up north, takes more (like 30 kW of panels) but doable.
Batteries to provide 60 kWh, or 180 kWh for 3 days without sun, is getting a bit ridiculous.

Did this happen before you had an alternative energy system with PV panels and batteries?
If you have grid power, why are you considering batteries? They are OK to backup small critical loads, but not for heating.

Does your utility offer "net metering", where you can bank kWh during the summer and use them in winter?

The power company is planning to start charging for the use of the lines next year. We don't have any power to the property at all. So Instead of the expense of getting hooked up, we have decided to invest in our own power supply. Our home will be a km from the road. The Atlantic provinces have the highest rate of power in the country. It is about double the rate as it is in Ontario.

We heat with wood, so will only need power to circulate the heat.

So what you are saying is, that I purchase enough panels for the maximum daily required power required, and the batteries required should be sized by the amount of power required for the day multiplied by the amount of days that it might be without sun in Amp hours. Now I just need to understand how to get the right power for the charge controller. I think. ?

 

[Hedges]

So your daughter's usage was at a different house. This one, she can't use more than is in the battery or available from PV.

Traditionally for off-grid, battery sized for 3 days without sun.
If you have a generator you can get by with less battery. With PV way oversized, you may get enough power even on overcast days.

Lead-acid batteries have shorter life if deeply cycled, but forklift type or Rolls Surette FLA reported last 20 years with the shallow cycling of a bank sized for 3 days. Also OK in freezing weather.
Lithium can deep cycle nightly for a decade or more (according to cycle life claims). If sized for 3 days, you're paying for cycles you may never use; I think would be better sized for one night assuming backup source of power available. Can't be charged below freezing, so needs to be kept warm.

My system is grid-backup, so I have AGM sized for one night. My PV array is so large it could charge in 2 hours, but system configured for 0.2C. During the day if grid is down, the other 60% of PV is ether used immediately or curtailed.

AC coupled (mine is SMA), all-in-ones, Victron, Midnight all I think have ability to adjust PV harvested so battery gets charged at target rate, and additional loads are powered. It requires measurement of battery current and control of PV MPPT.

Controlling loads to utilize available PV is the thing to do. Fill water tank and heat water when there is surplus. Cycle HVAC on and off (or run variable speed) keeping battery near full. Enable freezers in the day, coast at night.

PV costs $0.025/kWh for all hardware, amortized over 20 years. Battery (only), name brand lithium and AGM cost $0.50/kWh over cycle life. FLA $0.25. DIY LiFePO4 $0.05 Bargain name lithium batteries may be fairly inexpensive.

But any battery is cheaper than 1 km of utility extension (would like to take service where it already is and just string 10 awg from tree to tree).

Got running surface water? (hydro)

 

[Catsassend]

Ha! Yes, we have running water close to where the house will be built. I don't think we have enough head pressure, it is a small stream and there is not much elevation. It will be something to play around with some day.

 

[John Frum]

We don't have any power to the property at all.

You may need want battery capacity to last additional days.
Either that or have a generator as backup for days when the sun won't cooperate.

 

[Don B. Cilly]

We heat with wood, so will only need power to circulate the heat.

And not much at that. Just wondering, have you had a look at the link in my signature?

Either that or have a generator as backup for days when the sun won't cooperate.

Depending on how much sun you (don't) get, and considering your panels will charge quite a bit even on cloudy (if not completely overcast) days, the second option might work out cheaper.
-

 

[Catsassend]

And not much at that. Just wondering, have you had a look at the link in my signature?

That's genius! Plus, it's a place to hang the guitar. ?

 

[Catsassend]

You may need want battery capacity to last additional days.
Either that or have a generator as backup for days when the sun won't cooperate.

Thanks for the advice. We do have generators, so we're used to being set up for emergencies.
I am now thinking it might be better to spend the extra $3700 that the lithium batteries would cost (over and above the cost of the lead acid) and get double the amount of lead acid. Would I need another Midnight controller to charge a second series?

 

[Hedges]

You can price out different battery options, consider the DoD you expect and cycle life.
Lead-acid wants a particular charge rate, and to always get full bulk + absorption charge.
Lithium is happy partially full.

Multiple lead-acid strings can be used, but all need to be identical size, model, condition. Then you need enough charge controller, whether multiple or just big enough.

Midnight Classic with Cerbo (I think) and battery shunt can adjust output so battery charge current is held steady, and additional power delivered when used by inverter. Good for lead-acid, less important for lithium but maybe handy with way oversize PV or cold temperatures.

LiFePO4 is really what people want these days. But some circumstances may make lead-acid better or easier to use.
Your generator can recharge lithium in 2 hours, where lead-acid could take 7 hours (less if PV can do the lower current absorption cycle.)

It is more PV I would prefer over more batteries, if it meets the need. Quality PV essentially never wears out and costs 1/10th or 1/20th of many battery choices.

 

[John Frum]

Thanks for the advice. We do have generators, so we're used to being set up for emergencies.
I am now thinking it might be better to spend the extra $3700 that the lithium batteries would cost (over and above the cost of the lead acid) and get double the amount of lead acid. Would I need another Midnight controller to charge a second series?

Suggest to hold off on the hardware until you have the audit data.

 

[Don B. Cilly]

I am now thinking it might be better to spend the extra $3700 that the lithium batteries would cost (over and above the cost of the lead acid) and get double the amount of lead acid.

Personally, I disagree. I would go LFP, and 48V, and be done with worrying once and for all.
Otherwise... one just sees it coming, believe me, going to yoga classes to learn to kick yourself properly from behind ;·)
Try with... not so much storage. Talk to your daughter. I mean, mine, even at the height of teenage silliness, I told her (sensible) things, she didn't listen... except, she did. She just had to pretend not to, but as soon as it was face-saving enough, she actually thought about it ;·)

You already use wood for heating. Excellent starting point. See how well you (all) can make do. Increase storage (batteries) as needed.
It might not be as much as expected.
I mean, planning on theory is all well and good, but there's no beating actual practice, is there?
Also, having not-quite-enough storage, at least for a while, is an excellent learning (to save energy) experience. I talk from experience ;·)

LiFePO4 is really what people want these days.

Yeah... one wonders why that is
-

 

[Catsassend]

Personally, I disagree. I would go LFP, and 48V, and be done with worrying once and for all.

You already use wood for heating. Excellent starting point. See how well you (all) can make do. Increase storage (batteries) as needed.
It might not be as much as expected.

Is it okay to add LFP batteries. I read somewhere that once you get the batteries, you can't add more or change any out because the batteries would perform at the level of your worst batteries. ? Or maybe I misunderstood.

 

[Catsassend]

LiFePO4 is really what people want these days. But some circumstances may make lead-acid better or easier to use.
Your generator can recharge lithium in 2 hours, where lead-acid could take 7 hours (less if PV can do the lower current absorption cycle.)

Ah. I had no idea there were different charge times. That's good to know.

It is more PV I would prefer over more batteries, if it meets the need. Quality PV essentially never wears out and costs 1/10th or 1/20th of many battery choices.

Thanks for your opinion, I think I will double the PV. That will save me an extra $0.05/ watt at $0.70 /watt Canadian, and who doesn't like a deal? ?
Now, does that mean that I will probably have to upgrade all the in between (the PV and Battery) components?

 

[Don B. Cilly]

Yes, it's fine. And while it may be true that, in parallel, you can have some imbalance, it's not something I would worry about.
It's one of the advantages of LFP, your "worst" battery will likely be very good.

I mean, of course, if you have one (or more) bad cell(s), it will be a problem. But
a) it's unlikely
b) it can happen even if you have a single battery
-

 

[Rennit]

Yes.

If you use CLOSE to 60kWh/day...

A 14kWh array isn't going to provide...
Now, if it is a 14.4kW array, then you will be producing that times the number of hours of sunlight hitting it.
Average is 5 hours in the US... or 73kWh of daily production...

I have a 12kw array and it will produce 80kwh a day currently on perfectly sunny days. I know location and time of year etc will change that but it is producing way over any estimate I've ever got. It's also clipping my inverter during the day for about 2-3 hours after my batteries are charged so there is even more potential there, just don't have the inverter power to use it.

 

[Catsassend]

I have a 12kw array and it will produce 80kwh a day currently on perfectly sunny days. I know location and time of year etc will change that but it is producing way over any estimate I've ever got. It's also clipping my inverter during the day for about 2-3 hours after my batteries are charged so there is even more potential there, just don't have the inverter power to use it.

So, it's starting to sound like the 14.4 kwh system with the LiFePo4 batteries should run our whole household needs once we build our log home, (heating with wood) no problem. ? So at $20,000 CAD, that's looking like a mighty fine future, that I won't have to continually through money at until it comes time to replace a component hear and there, or batteries.

 

[Catsassend]

Thank you everyone! This forum rocks!! I think I am finally understanding what this all means. Yeah!

One other thing - What kind of service to my household panel do I get? What I mean by that is that in my current home I have 200 amp service from the power company, in an older house I lived in I only had 60 amp service and I couldn't run a toaster and a vacuum at the same time without blowing a breaker. Is there an amp service number that I need to know that the PV system will connect to my house?