How many watts would it take and how many batteries

[ThePort]

Hi -

I've been reading this web site for the last few months and I think it's really awesome . I'm setting up a small wind and solar system ( starting with solar only ) at my house and i'd like to be able to generate 5KW per day. With the equipment I have I think i'll be generating around 1KW but i'm not sure till I get some real experience with it. My question is how many ( solar panel only ) watts would I have to have to generate 5KW and how many batteries would that take if I used 5 KW per day ? Also I guess I should ask how many watts can I realistically expect to generate with 300 watts in solar panels ? That's what i'll be starting with. The batteries are the only pieces to the puzzle I don't have. I plan on using the Sam's 6 volt "golf cart batteries" I think it was 115 Ah . I live in southern Texas near Houston i'm guessing i'll have 5 or 6 hours of useful sun per day. I have an idea but i'm not comfortable with my caculations especially on the batteries. I hope this is enough imformation.

Thanks

Mike -

[ignesandros]

Simple math will tell you the number of batteries required for to store 5 KW-Hrs of power would be 8 of the batteries you described. Of course, you'll want to have more than that so you don't overwork your batteries (not to mention losses in the actual storage capacity due to battery wear). You'd probly have to test the panels for actual power output. This can vary based on quite a few variables.

-Andrew

[commanda]

300 watts times 6 hours is 1.8 Kw-Hrs per day.

To generate 5 Kw-Hrs with 6 hours of sunshine would require 5000/6 = 833 watts of solar panels. Add 20% if you're going to store it in batteries & re-use later.

There are solar irradiation charts that will tell you how many hours of useful sunshine you can expect per day in your location. Houston being fairly south I'd have thought it would be more than 6 hours, but maybe allowing for cloudy days etc.

Amanda

[ghurd]

Those Sam's Club batteries are 210 AH.

A 300 watt solar array will make about 17.5 amps at 12 volts, or 212 watts.

The average is about 4.8 hours of sun.

That is 1016WH / day, or 85AH / day.

For 5KWH / day it would take about 1500W of solar.

You can use 70AH or 850WH a day on average and be fine.

Use a little less in strings of cloudy days, more in sunny...

With 300W of solar at 12V, 2 pairs of the Sam's Club batteries would be OK.

But 3 pairs would be better.

For 5KWH / day, a bigger battery type like L-16s or something,

would be a much better choice than the T-105 type batteries.

G-

[georgeodjungle]

just wondering why are you going with solar first?

and 5kw a day at what volts?

is that what your burning now ?"on the grid"

cuz 5kw @ 240 is like 100kw @ 12v

[ThePort]

I'm going with solar first because I have that ready to go. I have the wind generator but haven't worked out the mounting yet. Also I was thinking the solar is going to be more consistent. I know the sun will come up each day but i'm not sure about the wind. I live by the water and get some wind almost daily. This is a learning experience for me so I am very curious about the amount of energy the wind generator will produce but until I get it up it seems like a big unknown variable. I have a Mallard 800 wind generator.

and yes the 5 kw is what we are currently using in the winter for the 3 summer months it about doubles. and that is on the grid at 240. I don't really understand how that calculates to 12V I didn't know they were different. Does that mean I wouldn't be producing nearly as much energy as i thought ? Calculating Ah into useful energy is where I get really confused.

with around 1kw or more I was hoping to start small and just run lights and hopefully the fridge off my intitial setup and then when I get a grasp of the energy I'm producing I was hoping to tie into the grid at a future date. If I can produce enough for that to make sense. Like I said before the wind generator is a big unknown to me.

[RP]

Uhhh, George made a typo there.  5KW is 5 KW at any voltage.  I think George was thinking 5000 amps at 240 would be 100,000 amps at 12volts.  

[georgeodjungle]

NO typo.

i started with solar. a big mistake for me at least.

not a good return for the money.

other than that, you'll even make power under moon light and stromy days.not much but some.

and need less storage than wind.

NO, watts isn't watts,same name?yes.

to keep it simple.

you need like 20 times more than your thinking.

from 12v to 240v ya know 20 times 12.

cuz:

here's an experimant for you:a 50 watt 12v pv with 5 hours of light will almost run a 50 watt 120v light bulb for a 1/2 hour.then try a 12v 50 watt bulb for all most 5 hours.

you do lose a lil with charging the battery.

they sell-em by the watts.

so back theroy.

ohms, watts law and all.

p.i.r.e

realy cool ya got most every thing every thing!

just sitting there!

i'm not a grid tie fan either.i'm cheep.not a good return for the cash.no batteries though!

:

if you run the mallard and have batteries, convert the genny to 24 volt. to charge at 12v.and dump when full.lower start up is good.

it's o.k. some are aven running 36v and a lot more.

HOOK-EM UP !!!

hook-em all up.

it's all there?just sitting!

do experiments.

you will see you need a lot more than you think.

as long as you hook-em correctly,can't hurt.

:

any way to cut back on the juice? 5 kw @ 240v a day that's like 21 amps.

oh,, but it's all so sold but the watts.

man-o-man that's a lot.

:ya must have a big family.

the sooner you hook-em up, the more of the grid, the more money in the pocket.

i realy hope this helps you.

[pyrocasto]

"NO, watts isn't watts,same name?yes.

to keep it simple.

you need like 20 times more than your thinking.

from 12v to 240v ya know 20 times 12.

cuz:

here's an experimant for you:a 50 watt 12v pv with 5 hours of light will almost run a 50 watt 120v light bulb for a 1/2 hour.then try a 12v 50 watt bulb for all most 5 hours.

you do lose a lil with charging the battery.

they sell-em by the watts."

No George, you would only need 20 times the power if you were running the same amperage at 240 as you were at 12. 50 watts = 50 watts regaurdless of the voltage.

That 50 watt 120v light would run almost 5 hours, just like the 12 volt lamp.

[TomW]

Mister jungle;

May I suggest you investigate this thing called "Ohms Law".Here is a good place to start!

It will help you not look like you have no idea about power as it relates to electrical energy.

T

[commanda]

any way to cut back on the juice? 5 kw @ 240v a day that's like 21 amps.

He means Kw-hrs.

Thats 5000/24 = 208 watts continuously for 24 hours.

Amanda

[Norm]

  George:Aren't you getting amps...watts...and volts mixed up?

volts x amps = watts

240. x 20.83 = 4999.20
     
12. x 466.66 = 4999.92
    
    

             ( :>) Norm.

[finnsawyer]

It's possible that he actually tried running a 120 volt bulb using power generated by the pv cells and got only 1/2 hour of use.  Of course, he would have had to store the output of the pvs and then convert from 12 volts to 120 volts, which introduces more losses.  On second thought, I doubt that he did it.  Even with the conversion 1/2 hour seems too low balanced against 5 hours of charging at 12 volts and 4 amps.  THe 120 volt bulb only draws .4 amps for gosh sakes.

[georgeodjungle]

no i don't think so.

when ya-buy a genny of any kind or PVs ya buy-em-by the watts.

batteries by the amp hour.

 i haven't even started about the batteries yet."more is better"

:

but he needs make a lot more juice..to get 5kw a day @ 240v

like 20.83 goes in to 4999.2 like 20 times or 1/20th

and 12v is 1/20th of 240v "thanks Amanda and Norm."

that's all i ment.

so your 200w PVs should make about 1000w + a day @ 12volt on good days.

"pending how old"

not including the wind mill.

:hook-em up!!!

i'd love to hear on how it's working for ya.

mike is this making it better or worse for you?

[ghurd]

Watts is watts.

Watt-hours is watt-hours.

The whole point of watts is to take into account the real power, regardless of the volts or amps.

If you still don't believe it, get an AC device that lists watts amps and volts.

Run it from an inverter, and test the amps from the battery, deduct 20% for inverter losses.

Then do the amps x volts = watts math.

Watts is watts.

[Drives]

Tom:

Thank You, Thank You, Thank You!  

Last time I checked...a watt was a watt.  Kind of like what's heavier...a pound of feathers or a pound of lead.

[georgeodjungle]

yep i believe it.

that's another great expariment.

 "for them 50w bulbs"

form the 12v side = aBout 5 AMPS before the inverter.

and the 120v side = is a little less than 1/2 amp. your milage my vary.

cuz 12v is a 10th of 120v.or 120 is 10 times 12 what ever.

another good one is get 2 batteries "the same" say 12v.

hook a 12v bulb to one and the 120 bulb to the other.

the 12v will be lit about 10 times longer.

or just watch the volts, ya realy shouldn'd drain batteries.thay don't like it.

so come december with 11 years of the grid:

all i know is:

you need more.

hook-em up!

ya. ya. ya. then do the math.