Power calculation Need help choosing panel size.

[micah]

I have been reading alot about solar and wind energy for a year or so now. I decided it was time to do something practical. I would like to power afew important things in my house.

First I would like to have min. of 4-5 Lights that would run all night long. They dont have to be very bright. Just enough so my kids can see to go to the bathroom and have a little nightlight in there room. Right now we are using 13w compact florecent and the give more light that we could ever ask for.

Second are 2 cell phone chargers. We charge our phones probably once a week depending on use. Once the phones are charged we unplug the chargers. There both 5.2V 700ma.

Third is my EEE pc laptop which is 9.5V 2.315A. This is always pluged it but not always in us.

These are the 3 things that when the power goes out I need to still work. My electric bill is around $42 a month and I use around 11KWH per day. Other than refrigerator, washer, drier, and 2 tvs I dont have any other electric usage. Hot water is oil fired, and we heat with wood. I think if i can cut these 3 things out. My electric bill will be bare minimum.

My problem is im not sure what watt panel(s) i should be looking for. Also how many batterys i need. My house gets great amounts of sun even in the winter.

Micah

[ghurd]

Google 'solar worksheet', fill out a couple.  Some are better than others.

Look into LEDs for tiny amounts of light.

The 4-5 13W CFLs is a load too large for solar if you expect to save money.

G-

[thirteen]

your oil fired water heater maybe a place to look for a change. My daughter just put an ondemand water heater in her new house. It is Lp. It is lite by a small vane igniter (sp) inline. Unless you use used oil which is another option, this might be an idea. You can also get a tax break with a new ondemand water heater. Maybe you could plumb in line, just before your water heater, a preheater water jacket (another used water heater say 40g.) You could heat it with the wood heat as it's heat source. Put a switch that goes to the Tv's that operate the outlet that they are on. They still use electricity even tho they are off. If you have modern washer and dryer they may also use power while just sitting idle. Some of the new ones have extra timers and clocks that run all of the time. The same maybe for your laptop. I know it is not much but things ad up. Just some ideas.

[dnix71]

11 KWH a day for $42 is cheaper than where I live. Your refrigerator is the biggest consumer, but you would have to cover the roof with panels to run that. #2 is probably the dryer. Use a clothesline instead to save electric.

If you are going to run lights all night long then leds are the way to go. I have a 12v led spotlight that was intended to automobile use that works well. An led car shoplight will put out lots of light without using much power. There are also closet led lights that use 3 AAA nicads or NiMH cells. If you are going to charge a cell phone from a small inverter, you could do the same with AAA rechargeables for peel and stick closet lights.

[wdyasq]

Just a quick 'guesstimation', all amperages will be based on 12V.

2. X 6hr X 700ma phones - 4.2AH ~ 50W
   
5. x 30ma x 12hr x 7days ~ 12.6AH ~ 152.1W (this figure could easily be cut by 2/3 with proper driving of LEDs)
   
   

ASUS EEE 2.31A X 3 hr night X 7 ~ 48.51AH ~ 582W

Total of 784Wh in 7 days or 112Wh/day

If we figured 3 hours of sun in worst days a 40W net pannel woudl do. As wattage is measured at ~20V and we have 12V batteries we need to multiply this by 20/12 to get actual panel size ~66W.

If you do a proper job with the LEDs and lower the computer use to 2 hours a day.... ... your power requirements will just about be cut in half.

You will need good batteries, these figures are all guessing on using a 12V, non-inverter system. 2-225AH 'golf cart' batteries would allow a safe draw-down of ~1200Wh of power. This would be many days of dunning with such a small system.

Ron

[micah]

Putting the TV's on a switch is a good idea. I'm going to go out today and get a few surge protectors. I had thought about doing ondemand hot water, but the initial cost of the unit and I dont have LP hooked up to my house I cant afford it. My water heater now actaully does really well. I go through about 125 gallons in about 1 3/4 years.

Im going to start looking at LED lights today. Would you recommend a certain brand, size, wattage, amperage? My house is very small and like i said the 13w flourecents are over kill.

Thank you wdyasq that gives me some great starting information. I can shave even more off those numbers. The cell phones only take 3 hours to charge, and the lights would only run 8 hours.

Would a panel like this be a good choice

http://www.solarhome.org/index.asp?PageAction=VIEWPROD&ProdID=1718

Would i need any type of charge controler with this small setup? When buying batteries im looking for deep cycle marine/rv style correct? I need to look for 12V with the highest AH rating so the battery will discharge longer?

Sorry for all the questions but I would really like to do this and this stuff is expensive so I only want to buy it once!

Micah

[wdyasq]

My opinion - your bes 'bang for the buck' in batteries will be the golf cart batteries. You could use a single 12V battery 'deep cycle'. I honestly believe the FLA 'Flooded Lead Acid' batteries and the golf cart size will last longer and are lowest cost until one gets to a much larger, more sophisticated system.

As far as a charge controller, you can just do it manually if you can and will pay attention to the battery voltage.

No comment on LEDs.

Ron

[DamonHD]

On LEDs I think you'll have to see them.

1. Warm-white are less efficient and more expensive and hard to buy for now.  If you like cool/daylight white, no problem.
   
2. LEDs are rapidly getting more efficient.
   
   

From those points I suggest that you build up your LED searchlight slowly!  B^>

Rgds

Damon

[ghurd]

Be advised, LEDs are not going to be much more than a dim nightlight.  Not even as bright as a 3W regular night light bulb, unless you spend a lot of money.

Should be able to find you way to the bathroom with a small LED bulb.

I am not a fan of that type of solar panel.

MorningStar SG-4 will handle that size and below.  Cheap.

Ron's numbers confused me when I thought it was for CFLs. 30ma and 12V is LED, instead of 12V CFL.

An 11W 12V CFL takes 920ma.

So 0.92 x 8 hours x 4.5 lights = 33AH per night.  416Wh/Day just for the 4-5 lights.

That is with 8 hours instead of 12 hours.

For clarity, just pointing out the difference in math with dim LEDs, and CFLs as bright as the existing lights.

G-

[DamonHD]

G,

I work in the evenings by a single (cool) white 3W LED as an uplighter off my 12V system.

So, it can be done.

Rgds

Damon

[ghurd]

Me too (same idea), but if a 13W CFL is being used instead of a 59-cent 5W nightlight, I get the feeling they won't be happy with LEDs.

G-

[micah]

Maybe i should clarify things alittle. The main reason im using the cfl instead of night lights is because there are no easily avalible outlets to plug them in to. I have had the small night lights in my kids room before and the do give off enough light. Since the outlet is close to the floor and over in the corner most of the light gets blocked. This is the same with the other 4 locations. My goal was going to be to have 2 lights. One that runs completely off solar/battery for when everyone is sleeping or kinda winding down. Then use the 13w cfl which is connected to the normal house electric for when everyone is still up and about or needs the extra light for reading or something.

[ghurd]

OK!  That's better!

LEDs will do it.

G-

[micah]

What brand panel would you recommend? Would this Harbor Freight 45w kit be a good starting point?

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90599

[ghurd]

Also, look into automotive bulbs.

Maybe #168 or #194 with 3 or 6 LEDs, and 20ma or 40ma.

Maybe LED dome light bulbs.

GREAT bang for the buck... for a dim nightlight.

No, they won't light a 24x24' room enough to read.

Be cautious of 19~ish LED #1156/1157 bulbs for direct replacement that brag too much and claim "just as bright or brighter", or 99 cent sales.

Be cautious if the ma is not listed.

"If it's too good to be true..."

G-

[ghurd]

"Starting Point", yes.

Good/Great solar panels, no.

But it is a pretty good deal, for a starting point.  Comes with two 5W 12V CFLs, brackets, wire.

Can get the kit for $153, when it is on sale and you have a coupon for the retail store.  Hard to argue with $153!

Google Search the board (top right) for

HF PV

HF panel

HF kit

and

HF controller (it needs thrown away before it ruins the batteries).  Replace it with a SG-4 unless you plan to expand, then get a SS-6, SS-10, or whatever.

Brand?  A name brand that you have heard of...

GE, BP, Sharp, Shell (now 'Solar World' so I'm not sure, but so far so good for me), etc.

ICP is not a brand name IMHO.  ICProblems.

Type?

I don't like amorphous / thin-film, from any brand.  They tend to have a short life.  Maybe 2 to 10 years?  5 to 10?

HF would be my first choice for a cheap thin-film to play with.

US is the only thin-film brand I would buy, but I wouldn't sell you one, because you'd expect me to deal with getting it exchanged.

Mono or poly crystalline tend to last a lot longer.

The cost is about the same as US-64 thin-film, sometimes cheaper.

It pays to shop around.

http://www.solar-electric.com/Solar_Panels/solar_electric_panels.htm

Tons of info on that site.

You asked!

G-

[zeusmorg]

 I'm still not convinced that LED's provide equal light to a same wattage CFL, and CFL's can be found as low as 2 watts. LED's do use less wattage, however their light is directional, so if you need a spot light they will be a better application, but I'm still sold on CFL's for room lighting.

 Night lights do a good enough job to keep you from tripping over the dog...

[DamonHD]

But I don't have a dog: will a nightlight still work for me?  B^>

Rgds

Damon

[zeusmorg]

 No, if you don't have a dog, or kids, why would you even need light?

 You already know where you put everything so ya wouldn't trip over it!

[ghurd]

Nobody said they did.

Maybe I misunderstood, but it sounds to me like everyone said they did Not.

However, if a few lumens is all that is required, then LEDs win.

Do you know of a supplier of 12V 2W CFLs?  That has good reviews.

How many ma does it draw from a 12.6V battery?

I bet I can make more LED lumens with 12VDC 30ma (with on-hand junk in my basement),

than any "same wattage" CFL.

"however their light is directional, so if you need a spot light they will be a better application"

That is not at all true.

Either you looked at comsumer grade (ebay?) LED bulbs, or surplus LEDs.

Just because cheap Chinese LED bulbs and consumer marketed LEDs...

Maybe it is true?

My desk lamp shines 0 light out the back of it's reflector, and 0 light out behind the socket.

It dosen't matter if the bulb is regular, CFL, or LED.

How many watts of CFL is needed "for when everyone is sleeping"?

That's all we said.

Except Ron, who knew better than to get involved.

[micah]

While searching for LED lights I came across these.

http://www.ccrane.com/lights/led-light-bulbs/geobulb-wedge-base-led-light-bulb.aspx

I read a few reviews and the seem to be a very good product. They look very promising but I dont see and watt or amps ratings only voltage?!