Solar sizing

[windme]

New to solar.
Have a 12 foot homebrew turbine on a 93 foot tower, which is working beyond expectations
Charging a 48 volt battery bank, with an outback gvfx3648 inverter.
Want to hybrid my system with solar  to just keep the bank full most of the time.
My Questions are what would any of you recommend as far as the number of (cells) panels would I need?
Where would you recommend I buy or get the panels from?
What would your biggest concern with adding solar to the system be?

[TomW]

how many Amp Hours is your battery bank. This helps in offering a sizing recommendation.

Tom

[windme]

sorry forgot about that,
Have 8, 6volt lp16's 420 amp hours each

[Rover]

Hi,

The answer to the following question would also help

What is your current and expected future drawdown on the bank (how much do you use, and when (time of day))? Either in Amp/hrs or Watt/hrs?

Rover

[richhagen]

I know that DanF has run an off grid hybrid system like that for years.  The wind turbine and the solar compliment each other in that often when it is cold and dark in December or January it tends to be windy, and often when it is calm it is sunny, which of course means more usable power more of the time for an off grid system.

I don't have the experience of DanF as my smaller system is mostly solar, but I've never heard anyone complain of having too much solar power.  I suppose you would not want your production to exceed the maximum charge rate of your batteries though, and the rule of diminishing returns would apply after a bit too.  I would probably size it at a minimum to try and get me through periods of calm winds reducing the depth of discharge to my batteries, thereby extending their life. Otherwise it is the economics of it or the space available that would determine how much I added.  Right now, solar is as cheap as I have ever seen it.  As long as you have a decent charge control scheme to prevent overcharge to your system and the charge rate of your batteries is not exceeded, there I do not see the harm in having more.  Sunelec has been selling panels for about a U.S. buck a Watt and I actually purchased some for 78 cents U.S. per Watt recently.  Again though I don't actually recall every reading a post about anyone having too much power generation.  Rich

[windme]

Thank you all for the info so far.
in Fact Dan F is the one who put my balance of the system together. He and Dan B, George and Scott were out at my place
last year when we put the turbine I had built with them.  I could just ask Dan F and I am sure he would tell me but I BUG HIM ENOUGH so I thought to ask the rest of you solar type of guys. I use this system purely as a backup to a few items in my house via a transfer switch, like the refrig, some lights and a freezer. To be used if and when the grid goes down.

 It also is used to run some stuff in my shop but only when I am in the shop and I never have much running at any one time.  My wind has been pretty good, but there are times when two or three days go by without enough to disallow the normal battery discharge to get down around 75 or 80%. Because I am not very good with the math part of all this renewable stuff, I Just don't know what would be to much.
I believe I can run a set of panels through a second controller and let my outback system control when it gets to full, I can feed back to the grid but of course only when the bank is very full. My goal is to simply keep it full with the solar when the wind is not around.
So Is 1kw too much? Or not enough.
thanks again guys.
 

[richhagen]

If all you are doing is maintaining a 48V 420 Amp hour bank without drawing power out, then 1000 Watts should be easily of what you need.  Rich

[ghurd]

It also is used to run some stuff in my shop but only when I am in the shop and I never have much running at any one time.  My wind has been pretty good, but there are times when two or three days go by without enough to disallow the normal battery discharge to get down around 75 or 80%.

I don't think I follow what that means.

Wind seems to run in a cycle.  2~3~4 days of wind, then 2~3~4 days without much or any.

Solar is quite predictable.
It may have a couple days without much power, but it is predicted in the predictions.

Below, I am ignoring MPPT solar tracking controllers.

Myself, I am NOT very worried if the battery reaches 75%, and regularly.
Keep in mind, batteries will fail from age even if no usable power was removed from them.  May as well use it while you got it!

My WAG is even 500W of solar would keep the battery SOG in the region you are looking for.

And with the combined power, there will be a high percentage of time it is an excercise in dumping excess power.
Might think about taking a couple small circuits off-grid?  The laptop(s) is something obvious, because they have an internal battery, and give enough warning to move the plug from RE to grid.  Maybe the UPS for the desktop computer?  Both are small in comparison to the extra power you will have available, IMHO.

At a certain point with solar power, bigger does not cost a whole lot more.
The battery already exists, and most of the 'etcs' will still work fine.
Decent 48V solar controllers would cost about the same for 100W or 1000W.
Wiring cost difference is not much.
Hardware difference is not much.
Etc.

With a little bigger solar array, there will be more power to use on a daily basis, for very little extra cost.

Back to the original question, 'How many cells?'
In a 48V sytem, I believe 132 would be fine (33x4), because there is only one 'diode drop' to contend with.
Most common (AKA: inexpensive) PVs will come in 36 or 72 cell configurations, and that means 144 cells.

If a portion of any of the PV string could be subject to shading, 144 cells would be my choice.

Watch out for the S&H charges for larger PVs.  Anything over about 80W per panel can come back to bite you in the butt when you get the freight bill.
G-

[Revolutionary]

I personlly think that sizing is all about what you will be able to make at a MINIMUM in midwinter. If your panels & windmill, (like I have) make too much power in summer, that's OK, because you can always bleed it off, use it, etc. I think that it's much better to have too much than too little, so the issue for me would be to first drive down whatever consuimption you have (use a killawatt) & then get as many panels & wind power as you can, UNLESS you have a real small home where your power draw is already small.
 Most people have to adjust to off-grid living form the perspective that power has, for them as well as the majority of the rest of us, came out of a plug in the wall. The power company is VERY efficient at delivering power, I sure took it for granted until we got off grid in August, this last year.

I have a lot of fun with it, though....