A Hybrid system that can switch between using power from Solar panels and the Grid

[Mike90250]

1) batteries have a finite lifetime of 5-10 years, unless you destroy them earlier. They cost a few $$ too!

2) you are way overthinking this. Install PV. Charge batteries. Sell to grid. Use grid as prime power, inverter for only when grid is down. If grid is down too long and batteries go low, start the generator to charge them.

Do not try to daily cycle batteries selling to grid and using batteries at night, you will halve your PV harvest recharging batteries and the layers of inefficiency that involves. There is nothing cheaper than Grid power, then comes plain battery free Grid-Tie.

[SunEagle]

1) batteries have a finite lifetime of 5-10 years, unless you destroy them earlier. They cost a few $$ too!

2) you are way overthinking this. Install PV. Charge batteries. Sell to grid. Use grid as prime power, inverter for only when grid is down. If grid is down too long and batteries go low, start the generator to charge them.

Do not try to daily cycle batteries selling to grid and using batteries at night, you will halve your PV harvest recharging batteries and the layers of inefficiency that involves. There is nothing cheaper than Grid power, then comes plain battery free Grid-Tie.

I don't know how to say it any clearer. Why do these people still feel they will be able to generate power cheaper using batteries than purchasing from their Utility?

They are either very naive or for some reason they just don't trust their POCO and think they can do it better.

[tasman]

Let me see if I'm following this: they have a generator, plus grid-tied solar panels, plus batteries. During the day the solar power feeds AC to the grid, and the batteries are charged during the daytime using AC from the grid. At night the inverter runs off the batteries, or you switch to the generator when the grid goes down.

This seems terribly complicated to me, and I'm not clear what the benefit is. You don't say where this system is located, so I suppose if grid power is super-expensive it might make sense. But if grid power is that expensive and you've got batteries and a generator and solar panels, why not just go off-grid?

No you're not following it right. They charge their batteries during the day from the panels, as well as feed into the gird. At night they use the lifepo4 batteries for power. The generator is for when there is lots of cloudy days and no wind, or for their 3 phase workshop. When the generator is running, they are charging the batteries, 2000ah of lifepo4 and 7kw of solar is adequate for what they need, to pay back and make a profit from their system.

Don't know what you lot are using, but if haven't exoerienced good lifepo4 storage systems and the massive adivatages oif them, then you don't have a clue and using very primitive 19th century technology.

Let's say, down here, the avergage quarterly energy bill is about $400-500, that's $2000 a year, which is very conservative. A lifepo4 system of 2000ah and 7kw of solar, costs $6000 for panels and $5000 for lifepo4 cells, $1000 for a 6kw generator and required assecories. The life of the system is more than 20 years, yet you can recoupe your invest in less than 6 years. Make a loyt of sense to me , rather than denial of the reality.

[russ]

Tasman - You do love to blow smoke don't you!

[Mike90250]

..... $5000 for lifepo4 cells, $.......
The life of the system is more than 20 years, yet you can recoupe your invest in less than 6 years. Make a loyt of sense to me , rather than denial of the reality.

How many 20% - 85% cycles for lifepo4 ? about 2,000 ?
365 x 5 years 1,825 days/cycles.
365 x 20y = 7,300 days/cycles - which I find very hard to believe. What battery mfg is giving that number ?

$5000 for lifepo4 cells At what watt-hour size ? 2000ah at 12V or at 48V ?

I do understand the LFP cells are over 95% efficient, but I don't see the watt-hours or expected lifetime of the system spelled out. Panels I can see 20+ years, but the inverter, I think the better guess is 10 years, same with charge controller.
I_want_to_believe5.jpg

[russ]

The hard part of teaching a safety class is convincing the students that actions they have taken many times can be dangerous or deadly. "Getting away with it" is no big deal in the short term - what happens over time is.

[SunEagle]

No you're not following it right. They charge their batteries during the day from the panels, as well as feed into the gird. At night they use the lifepo4 batteries for power. The generator is for when there is lots of cloudy days and no wind, or for their 3 phase workshop. When the generator is running, they are charging the batteries, 2000ah of lifepo4 and 7kw of solar is adequate for what they need, to pay back and make a profit from their system.

Don't know what you lot are using, but if haven't exoerienced good lifepo4 storage systems and the massive adivatages oif them, then you don't have a clue and using very primitive 19th century technology.

Let's say, down here, the avergage quarterly energy bill is about $400-500, that's $2000 a year, which is very conservative. A lifepo4 system of 2000ah and 7kw of solar, costs $6000 for panels and $5000 for lifepo4 cells, $1000 for a 6kw generator and required assecories. The life of the system is more than 20 years, yet you can recoupe your invest in less than 6 years. Make a loyt of sense to me , rather than denial of the reality.

I see only half of the information to help me agree with you that your way is cheaper then purchasing from the Utility.

How about telling us roughly were you live and how much a kWh costs you. $400 to 500 a quarter doesn't mean anything to me because I do not know how many kWh you are using in that time period.

What is the make and model of the LiFePO4 batteries and how are they wired? We can calculate the kWh it can generate a year and estimate a range of life in years.

What is that 7kw array consist of. Panel make and model as well as the charge controller and inverter.

One top of that, where did you purchase those panels and batteries for that $11,000? Did you add in the shipping cost and possible tariffs? How about what it cost you to install that system. It all adds up to a big $$$ and when you do the math you can estimate what it costs to generate a kWh from your system.

You may think you are saving money by using batteries at night instead of the "grid" but I still think you are truly unaware of what the cost is to generate your own electricity.

[SunEagle]

The hard part of teaching a safety class is convincing the students that actions they have taken many times can be dangerous or deadly. "Getting away with it" is no big deal in the short term - what happens over time is.

I agree with you it is sometimes hard to convince someone of what is safe and what is dangerous. The learning point hopefully comes with just a little "damage" and a lot of OH S**T!!!!

At least with his way of thinking the bad part ends up being just the loss of money. With safety the end result usually ends up with much worse like dismemberment or death.

[donald]

You may think you are saving money by using batteries at night instead of the "grid" but I still think you are truly unaware of what the cost is to generate your own electricity.

The only place it may pay are businesses using battery at peak rate times. The ROI can be 10-20%.
But the potential for a positive return on investment will improve as battery prices drop. The first solar system I installed was off grid. It's very odd for me now that people are discovering that batteries can be added to solar. Anyone considering a good backup generator should consider batteries instead. Anyone looking at a new system today should consider they may want to add batteries in the future.

[russ]

The only place it may pay are businesses using battery at peak rate times. The ROI can be 10-20%.
But the potential for a positive return on investment will improve as battery prices drop. The first solar system I installed was off grid. It's very odd for me now that people are discovering that batteries can be added to solar. Anyone considering a good backup generator should consider batteries instead. Anyone looking at a new system today should consider they may want to add batteries in the future.

Pure and blatant BS - nothing more. You made a nice mess and now you are trying to convince yourself it was a good deal.

[donald]

Pure and blatant BS - nothing more. You made a nice mess and now you are trying to convince yourself it was a good deal.

What was a good deal? What mess ? The only lithium batteries I have are in the usual small electronics. The only solar I own is typical residential technology.

[SunEagle]

The only place it may pay are businesses using battery at peak rate times. The ROI can be 10-20%.
But the potential for a positive return on investment will improve as battery prices drop. The first solar system I installed was off grid. It's very odd for me now that people are discovering that batteries can be added to solar. Anyone considering a good backup generator should consider batteries instead. Anyone looking at a new system today should consider they may want to add batteries in the future.

I disagree with your logic. Mu logic is based on the existing cost of batteries that installing them NOW is less cost effective than using a generator. Hopefully sometime in the future "energy storage technology" will not only improve but be much lower in cost. Then you should look into (if the cost is justified) to add that storage system.

The generator is both the right choice for emergency backup as well as required if you have batteries. So that comes up front no matter what the cost of batteries.

[donald]

I've had generators for years, both running on gasoline and mains natural gas. I would gladly pay more for batteries and forget the generator. In fact I did this in my camper. But my idea of backup power at home doesn't include air conditioning.

[tasman]

How many 20% - 85% cycles for lifepo4 ? about 2,000 ?
365 x 5 years 1,825 days/cycles.
365 x 20y = 7,300 days/cycles - which I find very hard to believe. What battery mfg is giving that number ?

$5000 for lifepo4 cells At what watt-hour size ? 2000ah at 12V or at 48V ?

I do understand the LFP cells are over 95% efficient, but I don't see the watt-hours or expected lifetime of the system spelled out. Panels I can see 20+ years, but the inverter, I think the better guess is 10 years, same with charge controller.
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Their system is 2000ah at 24v, believe cycling in lifepo4 is very different to LA. With lead acid, you have approximately 30% of usable energy in a 2000ah battery bank. With lifepo4 you have 100% if you want to use it, which would definitely create cycling. By only using 80% and with proper computer control of your entire energy system, cycling becomes rare as most properly set up systems rarely reach their upper and lower voltage parameters to create a full cycle. With lifepo4, you never have to fully charge them, they are more than happy at 80%. Very different to LA which requires to be fully charged to get the best performance and longevity, so they cycle every time you use 15-30% of the supposed capacity.

It took me a long time to understand and see this in action and like most, doubted it possible, yet my 700ah lifepo4 house system in almost 2 years, has yet to reach it upper or lower limits and that is 80% of charge and 80% discharge. So have no idea whether or how many cycles it has been through, but could say none because it has never had to stop charging or stop supplying load. No LA system can say that ever.

From what I've learnt, seen in action and told by those who have been using lithium technology for at least 5 years, cycling only occurs when you reach upper or lower battery parameters. This comes from a company that designs, builds and installs lifepo4 off grid and grid connect systems and has a number of test packs of different lithium technologies. One lifepo4 has been running their office for more than 5 years they say and has yet to reach cut off voltages. Got my idea of fully computerising my home system with open source from them and can say it is a wonderful way to utilise and control energy.

I still have a couple of 80w panels operating from the 1980's which are now on my workshop and two inverters. One is a modified sine wave 12v x 300-600w I built which was used to construct our house, still use it for power tools running off a tractor or a vehicle. The other is a 12v x 1500-2500w pure sine wave I built in the late 1980's and still works in my workshop, since I bought a cheapo Chinese 3000w-6000w 12v inverter on an ebay auction a couple of years ago for the house.

The life span of any system relies upon it's management and with lifepo4 and computer control, you enter a totally different energy world. If you have a computerised system then you have even more control, so our house runs on 12v and 240v, with LED lighting and no need for heating or cooling, as our home sits 1.5m in the ground.

I'm working on a very old Compaq 256k ram laptop at the moment, to get it to the stage where it can run our MH (RV) lifepo4 system instead of doing it manually with BMS at the moment. Probably preferable to use a raspberry Pi, but got this dinosaur brick for $5 at a garage sale.

[tasman]

I see only half of the information to help me agree with you that your way is cheaper then purchasing from the Utility.

How about telling us roughly were you live and how much a kWh costs you. $400 to 500 a quarter doesn't mean anything to me because I do not know how many kWh you are using in that time period.

What is the make and model of the LiFePO4 batteries and how are they wired? We can calculate the kWh it can generate a year and estimate a range of life in years.

What is that 7kw array consist of. Panel make and model as well as the charge controller and inverter.

One top of that, where did you purchase those panels and batteries for that $11,000? Did you add in the shipping cost and possible tariffs? How about what it cost you to install that system. It all adds up to a big $$$ and when you do the math you can estimate what it costs to generate a kWh from your system.

You may think you are saving money by using batteries at night instead of the "grid" but I still think you are truly unaware of what the cost is to generate your own electricity.

Can't tell you any more about the 7KW system, as it's not mine, but got most of my stuff from the same suppliers. Ours is 700ah lifepo4 and 2kw solar. Built it all myself, the current 24v panels are 250w and cost $235 each delivered.

When doing any costing, you always include freight etc. never buy brand names, always buy what is recommended by people in the know and gives the best price. When we want to buy more, we do it as a group with others and get the best prices available. The capacities range from 40-60ah, never use large capacity cells. That way if a cell goes wrong, you can take it and a couple of others out and still have an almost full system, but with 100+ah cells, if one goes down, that's probably it for the entire system. I have spare cells, which are used as my test pack and always carry a 120/60 x 12/24v pack when we travel, yet to use it for anything but testing BMS and other parts of the system.

Our lifepo4 are sourced from manufacturers of industrial and military cells, which have overrun orders and badly branded cells, which means we seem to get them pretty cheaply. Our last set of 45ah x 3.2v cells, cost 59 cents an amp and totalled 83 cents an amp delivered, yet they are branded as 1400ma, 20v.