18KW off grid system need help

[Allen Chen]

Hello,

I try to build a 15KW off grid system but don't have any experience, is there anyone out there able to provide your experience especially the following questions. Grid tied is no problem to me

1. Which battery should I use, deep cycle AGM battery ?
2. Which AH is most cost effective, 100 AH, 120AH or 200AH ? Why ?
3. Do I need individual Charge controller or off grid inverter come with function of charger controller ? Which one is better ?
4. Do I need battery management system ?
5. Do I need a diesel generator ? If generator is adapted, I can use less battery ?
6. Do you have any existing block diagram or electric diagram for layout, wiring diagram shows the connection of those equipment for my reference ?
7. Is li-ion battery worth for such system ?
8. Which equipment (brand) do you recommend which is reliable and cost effective in today's market ?

Thank you very much for your time

Allen:(

[Ben Colla]

wind or solar?

[Micheal lee]

1) AGM is OK
2) The battery bank depend on how much power you want to in stock, if the rated voltage is 240V and the 200AH, then the total power in store is 240*200/1000=48 kilowatt-hour. But we can't use all power in the battery, only about 70% of total. So you can only use about 32 kilowatt-hour power.

[Micheal lee]

3) You must need a control system to monitor the generator working data and control dump load if the battery is ful, off-grid invert is also need. You'd better choose a reliable company, I've use Hummer inverter and controller (www.hummerwindgenerator.cn), it's good and easily remote control by internet. Hummer inverter has battery manage system, it's pratical and useful.
4) you don't need li-ion battery, it's too high.
5) please contact with Hummer wind generator company, the website is www.hummerwindgenerator.cn and then ask them, you may get wiring diagram shows .

[Rob Beckers]

Allen, I'm hoping one of the off-grid guys/gals on the forum will jump in and help you out. Here's my take on your questions, but keep in mind that I don't live off-grid.

1) Depends on what you plan to do: Are those batteries going to be cycled every day? Or is this "backup power" for when the grid goes out? For cycling nothing beats regular deep-cycle batteries. AGM and gel (sealed) batteries work, but you can't replace the water lost during charging. Beyond battery type, there is a wide range of battery qualities in all those types; some will not last more than a few years, others regularly make it to 15 -20 years (very different no. of cycles that they are rated for too). Of course, the good stuff comes at a price.

2) Depends on the battery bank size and voltage. You want to minimize the number of parallel strings of batteries (2 if you can, no more than 3 if you have to). The battery capacity follows from that. The more parallel strings you have, the harder it gets to keep them all charging and wearing evenly, and the worst one in the batch will drag down the others.

3) Battery based inverters have charge controllers build into them if you have a source of grid-power to charge from (could be a generator). When you hook up wind or solar, they go straight to the batteries, with their own charge controller.

4) That's what a charge controller is (in essence). Or do you mean if you need a battery monitor? If the inverter doesn't have this, I would recommend having something that shows you state-of-charge, so you can adjust your life-style around that (no laundry if the batteries are nearly empty etc.).

5) If you're completely off-grid, most people will need a generator. It's a trade-off between cost vs. generator: Normally off-grid systems are sized for 3 days of autonomy in case the sun doesn't shine and the wind doesn't blow. There will be periods where 3 days is not enough, and you then either have to shut down all electricity use (to prevent destroying your batteries) or run a generator. Obviously you can size a system so 99.999% of the time there's juice left in the batteries, and you'll never need a generator. It just gets very expensive.

6) Get a decent book (from the library) that lays out off-grid systems. I don't really have a title readily in mind, but there are many. That should make things clearer.

7) They look promising (the Lithium-Iron-Phosphate type batteries), but are still very, very expensive.

8) For inverters, if you need it to work every day, I like Xantrex's XW series. Magnum looks promising too, but no personal experience with that. For batteries there are many brands and price ranges. Unless you are very organized, and have an engineering mindset, I would recommend starting with cheap(er) batteries. You'll likely destroy them prematurely while figuring out how to live within an energy budget, and how to pamper them (keeping them charged, they don't like standing around discharged for too long, watering, keeping depth-of-discharge within limits etc.)

The part you did not mention, but that is probably more important than any of the above, is proper system sizing. I don't know how you arrived at 18kW, but you have to get that part right or be doomed to lots of frustration. It starts with an honest list of all the loads you are planning to run, and for how long each day they will be used. From that follows the inverter size (power needed) and battery storage size (energy needed). Batteries are normally sized for 3 days of autonomy, and 50% DoD. From that follows what you will need to keep those batteries charged in terms of wind and solar.

-RoB-

[Allen Chen]

wind or solar?
Thanks for advice. It's solar system

[Allen Chen]

1) AGM is OK
2) The battery bank depend on how much power you want to in stock, if the rated voltage is 240V and the 200AH, then the total power in store is 240*200/1000=48 kilowatt-hour. But we can't use all power in the battery, only about 70% of total. So you can only use about 32 kilowatt-hour power.


Michael,

Thanks for the advice of AGM. Understand watt=VXI but is there anything to do with 48KW
to18KW ? Or just an example 18KW should have the capacity of 48KW but only 32KW can be used ?

Thank you

Allen

[Allen Chen]

3) You must need a control system to monitor the generator working data and control dump load if the battery is ful, off-grid invert is also need. You'd better choose a reliable company, I've use Hummer inverter and controller (www.hummerwindgenerator.cn), it's good and easily remote control by internet. Hummer inverter has battery manage system, it's pratical and useful.
4) you don't need li-ion battery, it's too high.
5) please contact with Hummer wind generator company, the website is www.hummerwindgenerator.cn and then ask them, you may get wiring diagram shows .

Michael,

Does this Hummer inverter only good for wind ? Do they have solar inverter as well ?
Another question, seems like you know wind a lots ? With this complete off grid 18KW system, price wide, which one, solar or wind, will be cost effective and compare with installation which one is difficult ?

Thanks

Allen

[Allen Chen]

Allen, I'm hoping one of the off-grid guys/gals on the forum will jump in and help you out. Here's my take on your questions, but keep in mind that I don't live off-grid.

1) Depends on what you plan to do: Are those batteries going to be cycled every day? Or is this "backup power" for when the grid goes out? For cycling nothing beats regular deep-cycle batteries. AGM and gel (sealed) batteries work, but you can't replace the water lost during charging. Beyond battery type, there is a wide range of battery qualities in all those types; some will not last more than a few years, others regularly make it to 15 -20 years (very different no. of cycles that they are rated for too). Of course, the good stuff comes at a price.

2) Depends on the battery bank size and voltage. You want to minimize the number of parallel strings of batteries (2 if you can, no more than 3 if you have to). The battery capacity follows from that. The more parallel strings you have, the harder it gets to keep them all charging and wearing evenly, and the worst one in the batch will drag down the others.

3) Battery based inverters have charge controllers build into them if you have a source of grid-power to charge from (could be a generator). When you hook up wind or solar, they go straight to the batteries, with their own charge controller.

4) That's what a charge controller is (in essence). Or do you mean if you need a battery monitor? If the inverter doesn't have this, I would recommend having something that shows you state-of-charge, so you can adjust your life-style around that (no laundry if the batteries are nearly empty etc.).

5) If you're completely off-grid, most people will need a generator. It's a trade-off between cost vs. generator: Normally off-grid systems are sized for 3 days of autonomy in case the sun doesn't shine and the wind doesn't blow. There will be periods where 3 days is not enough, and you then either have to shut down all electricity use (to prevent destroying your batteries) or run a generator. Obviously you can size a system so 99.999% of the time there's juice left in the batteries, and you'll never need a generator. It just gets very expensive.

6) Get a decent book (from the library) that lays out off-grid systems. I don't really have a title readily in mind, but there are many. That should make things clearer.

7) They look promising (the Lithium-Iron-Phosphate type batteries), but are still very, very expensive.

8) For inverters, if you need it to work every day, I like Xantrex's XW series. Magnum looks promising too, but no personal experience with that. For batteries there are many brands and price ranges. Unless you are very organized, and have an engineering mindset, I would recommend starting with cheap(er) batteries. You'll likely destroy them prematurely while figuring out how to live within an energy budget, and how to pamper them (keeping them charged, they don't like standing around discharged for too long, watering, keeping depth-of-discharge within limits etc.)

The part you did not mention, but that is probably more important than any of the above, is proper system sizing. I don't know how you arrived at 18kW, but you have to get that part right or be doomed to lots of frustration. It starts with an honest list of all the loads you are planning to run, and for how long each day they will be used. From that follows the inverter size (power needed) and battery storage size (energy needed). Batteries are normally sized for 3 days of autonomy, and 50% DoD. From that follows what you will need to keep those batteries charged in terms of wind and solar.

-RoB-


Hi Rob,

Yes, someone in this forum send me some advice which is very helpful to get me to start

1. Yes, it's complete off grid system and battery will keep cycle daily. I am helping a friend of mine set up this system overseas. Their electricity is unstable usually they use generator for back up but gasoline price is very expensive so they like to have solar system installed
2. To get start of this kind application which brand or type of battery will you recommend?
3. Exactly, this is why I am asking for battery management system, making sure we will have even charge and discharge of the battery if we have BMS without BMS, max 2 string in parallel, in another word, if we only have 100AH 12V battery available, in order to reach the sufficient size of 18kwhDC probably we will need at least 100KWhDC for battery capacity ? but if we only allow 2 strings in parallel (200AH) the system voltage will be real high ? 100000/200=500VDC ?
4. Yes, I heard lots about Xantrex, seems like real popular but my question is does this model comes with charge controller and limit charge/discharge current ? DC to AC distribution function ? How easy to connect ? Does thois have battery monitor function i.e. temp .... ?
5. For a system 18KW, how do you suggest the capacity of generator ? How to leverage
the capacity of battery need and generator size ? 3 days autonomy, noted, tks
6. Will xantrex inverter or controller have the function to set up charge rate ? Trickle charge and discharge rate (let's say 60% DOD ?)
7. Yes, I understand to specify the load hour is important but I don't have such number
usually what know people most assume 25% of 18KW ?????

I am in Taiwan airport transit to China, need to go now. Nice "talk" to you will talk to you soon

Allen

[Dale Sheler]

One important thing to find out is whether the hummer is UL approved, you can read lots of horror stories right on this forum of non existent customer support with Chinese products.
Caveat Emptor.