Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Solar Back Up Power
How about setting a solar/wind/water system for use in emergencies, if the batteries are free then he can bank them for use when the power does die out so he can light the place with lv bulbs or leds

here in the uk those with solar generally patc it back in to feed the national grid so they get cheaper electric overall rather than going off the grid.

the only solar which does work regards self sufficiency is water heating. lots of projects where you can make your own water panels out of old central heating radiators and use a solar circulation pump.
If can keep your head while all around are losing theirs then its possible you may have seriously misjudged the situation.
Battery Update: Deep cycles batteries are designed for MANY slow discharges up to 80% without harm to the battery. Auto batteries are designed for a lot of current to be suddenly discharged but can't handle sustained drains of more than 5-10% with damage. Plates on auto batteries are thin which makes them less durable. Deep cycles plates are thicker and therefor able to withstand being drained. How thick they are depends on the brand and it's intended use. As a result, deep cycle batteries have about 70% of the "cold cranking amps" of a traditioanl auto battery but auto batteries have about 70% of the "Amp hours" of a deep cycle. My experience is that auto batteries have far less than that and are lucky to last 1/4 of the time. Just my experience. If a deep cycle battery has 100 AH's than an auto battery of comprable size will have 70 AH's. That would be a good number to calculate the MAX amp hours for an auto battery.

Now to see how that applies. Like I said we use Ohms Law. Watts = amps x volts, amps = watts/volts, volts = watts/amps. Now we need to figure your load 2 ways. #1 is your max watt requirements. Say you want to run a refrigerator (maybe 6 amp @ 120volts), a freezer (roughly the same), a furnace (5 amps @ 120volts) and 12 - 13watt fluorescent light bulbs (157 watts). The equipment numbers very so check the nameplates on your equipment. Using Ohms Law we have 720watts + 720 + 600 + 157 for a total of 2187watts if all your equipment runs at the same time which it can. If you were going to use a generator (or inverter if you are using batteries) you would want one that is sized at 2187 + 25% or 2733 watts (MINIMUM). Note I said generator but this could be wind or solar also but the start up cost for this much wattage is extreme.

But your equipment doesn't run all the time. Now we need to figure the average wattage used per hour in a day. Let's say your refrigerator runs 15 min out of every hour. Same for the freezer and the furnace. Your lights will run for maybe 6 hours a day.

Refer = 720 watts x 24hours x 25% (15 min per hour) = 4320 watts per day / 24 hours = 180watts per hour.

Freezer = same = 180 watts per hour.

Furnace = 600watts x 24 hours a day x 25%(15 min per hour) = 3600 watts per day/24 hours = 150 watts per hour.

Lights = 157watts x 6 hours = 942 watts per day / 24 hours = 39 watts per hour.

On average you'll use 549 watts per hour WITH THE EXAMPLE POWER LOAD.

A 100AH deep cycle battery has about 1200 watts (100amps x 12 volts = 1200watts), a auto battery 840 watts MAX. Now how long do you want to have back up power? Say you decide you want power for 24 hours: 549 watts x 24 hours = 13176 watts. To run your house for 24 hours you need 11 deep cycle batteries 13176/1200watts) or 16 auto batteries (MIN). Want to run 2 days? Double it, etc. Then you need an inverter sized like the generator above or 4 seperate inverters sized at at 25% over the load for each piece of equipment. Example: Refer @ 720watts x 125% = 900 watt inverter.

If you have a solar or wind power source you can decrease the load on your batteries by the amount of wattage it supplies. Example: 200 watt wind source. 549 wats per hour (see example above) - 200 watts = 349 watts per hour on your batteries as long as the wind blows. A 200 watt solar system will only supply a MAXIMUM of 100watts average per hour (sunshine = 12 hours). More than likely less than that due to location and less sunshine average. So you can remove 2 deep cycle batteries (100watts per hour x 24 hours = 2400 watts devided by 1200 watts (deep cycle battery wattage) = 2 batteries). It will take the solar system about 6 days to recharge the batteries once they are dead.

For me, I want a battery bank that will last me 24 hours AND a wind generator that will meet my MINIMUM load requirement. My system would run off the wind when the wind blows and from the batteries when it's still.

Hope my math is right (getting fuzzy here!) and Hope this helps,

Thanks for that post CB.
[quote name='Roadracer' post='365830' date='May 12 2009, 10:56 AM']But worthless for minimal power backup?

I didn't want to run the house. I was thinking small items.[/quote]

What if you did want to power your house minimally?

Lights with flourescent bulbs, refrig., stove, some outlets for radios or charging batteries, hot water heater, ect....
"The sun has not risen on the day that I will face death graciously. I will kick, and claw, and bite, and scratch, and spit my last breath in it's face. Never give up!"

"Beware the beast man, for he is the Devil's pawn. Alone among God's primates, he kills for sport or lust or greed.

Yea, he will murder his brother to possess his brother's land. Let him not breed in great numbers, for he will make a desert of his home and yours.

Shun him; drive him back into his jungle lair, for he is the harbinger of death."
[quote name='alco141' post='365966' date='May 12 2009, 03:21 PM']problem with wind is that you need a constant 20 mph to make it work well, there are very few places in the usa that has this constant wind day in and day out. look at some of the wind maps of your area, you will be supprised at what you see as far as average wind velocity. the tower needs to be 30-50 ft tall to get over most trees and obstructions.

here is a map of average wind values for the didfferent states:



That's the problem here in Florida most of the time, no wind.
"The sun has not risen on the day that I will face death graciously. I will kick, and claw, and bite, and scratch, and spit my last breath in it's face. Never give up!"

"Beware the beast man, for he is the Devil's pawn. Alone among God's primates, he kills for sport or lust or greed.

Yea, he will murder his brother to possess his brother's land. Let him not breed in great numbers, for he will make a desert of his home and yours.

Shun him; drive him back into his jungle lair, for he is the harbinger of death."
Solar suck, think wind.


I think it's solar sucks wind Blows. Ha

I have both... I use 1000W turbines off EBay at the top of power poles. Not for the weak of heart to work on them : )

Invest in LED Christmas lights for lighting.

BTW I had the power go out with the heavy storm tues about 3hrs . and all the outside lights stayed on with my back up. But

the celler sump pump needed power and the water came in so I hadto hump all the stuff out of there so it wouldnt get wet. Note to self: run backup power to sump pump. Ha
(would take 6.66 days to recharge a 100% dead battery. Quote)

I knew the Devil was involved. Ha
math, we're doing math now. Way too involved for me. I have the generator and a hand pump for the well, if I'm without electricity for too long, all I'll miss is my air conditioning. Think canned foods and slit trenches!!!!!!!!!!!! Good luck.

Good better best, never let it rest 'til your good is better and your better is the best....HOOAH!!!!!

" I can't stand rude behaviour in a man, I won't tolerate it".....Woodrow F. Call
[quote name='TN RIDGE ROVER' post='367166' date='May 16 2009, 07:11 AM']I think people have a few wires crossed here. There's a big difference between emergency power and a full on off the grid system. I think RR is on the right track with the gell cells. I suggest 12 volt bulbs, fridges, etc and DC generators. Solar is a good back up if all else fails. At least you have some energy comming in.[/quote]

Good points.... Since this is in the Urban Survival section I'd say Wind Power would be out in many Urban areas...People get enuff grief trying to get a large SW antenna up in urban areas and it's doubtfull you'd get a permit for a 50' tower for a windmill..Solar for emergencies is probably the best bet in town..
The numbers are right but the premise is wrong.

In it's own way "wind blows", it takes at least 10-12 mph

avg. wind speed to produce any usable power.

Wind gen. power curves are very steep, 10-12 to work with

max output around 20-25mph.
"Pain Heals, Glory Lasts Forever" ( Falco )

There are 10 kinds of people in the world.

1. Those who understand binary,

2. And those who don't.
This is a great post guys...I have learned alot so far.

What about water generation with turbines........Are these attainable for a reasonable price????

I've read a few things on people using small ones for DC lighting.

here in Bama we have lots of running water, just wondering if it is worth it.
My wife and I use a small solar pannel (5 volt trickle charger) to keep a charge on our camper (30 ft) batteries (two 12 volt deep-cycle in parallel connection) purchased from This system allows us to keep the frige running (gotta keep the beer cold) 100% of the time (the hunting property is our get-away during the spring and summer and our bug-out destination if SHTF), and the furnace running in during the Nov. and Dec. Deer hunts (we turn it down to 50 degrees when not there). If I have heavy use on the batteries (like during the deer hunts when we are there a lot and the inside temp is kept at 65 degrees), occasionally need to run the generator as a supplliment charge. Also have to run the generator to run the AC, Microwave, and TV.
Regarding solar power....

Just thought I would add a couple of calcultations which might be usefull for planning solar power configurations.

The amount of solar radiation output from the sun is nearly constant, but the distance between Sun and Earth changes with several million kilometers through the year.

On average we receive 1369 watts pr square metre, but this is a calculated value for a 1 metre square at 149,596,000 km distance from the centre of the sun. A small amount of radiation is absorbed by the atmosphere of the earth, but this number is rather small and difficult to calcultate exactly. Furthermore the radiation varies as the distance between the sun and earth changes, but this number is also pretty small.

Further, the radiation from the sun normally hits the earths surface at an angle, thereby enlarging the area on which a solar ray of 1 square metre would hit. This affects the amount of received energy by a large amount.

Therefore we have to calculate the amount of radiation which is practically reaching the surface of the Earth, and which can be converted into photovoltaic energy by the solar panel.

To do this calculation we need to know the angle between the sun and the horison. Where I live this is about 57 degrees in the summer and some 10 degrees in the winther.

The area which a one square metre solar ray would cover can be calculated by the formula a= 1/sin(h), where "h" is the suns angle above the horizon.

To convert this to a usable number (given in watts pr square metre) one would divide the solar constant by the area reduction calculated above.

An example for the summer:

Solar constant is 1369 watts pr square metre,

Suns height over the horizon measured in degrees (elevation) is 57,5 degrees

1369 / ( 1 / sin 57,5) = 1154,6 watts pr square metre

Similar example for the winther:

Solar constant is 1369 watts pr square metre,

Suns height over the horizon measured in degrees (elevation) is 10 degrees

1369 / ( 1 / sin 10) = 237,7 watts pr square metre

These numbers give a realistic approximation to how much solar radiation reaches the solar panels.

However, the solar panels cannot convert the energy totally efficient, instead the efficiency for good solar panels is about 20%.

This means that - in the wintertime - a one square metre solar panel might produce 47,5 watts at my location.

In the summertime it would produce 230 watts at my location.

Further one need to calculate the amount of hours that we receive usefull sunlight pr day. For the winter - at my location - this is about 5 hours a day.

This means that the one square metre solar panel would produce 5 hours of 47,5 watts, equalling 237,5 watt-hours or 0,237 kilowatt-hours. To put into perspective, this amount of power would be enough to power a small laptop for about three hours, but not for running any larger household appliances for any amount of time. It would not even be enough to supply the needed power for the circulation pump in the wood-burning central heating system.

For the summertime the numbers are all different. We would get more than 12 hours of usefull sunlight - meaning 230 watts * 12 hours = 2760 watt-hours or 2,760 kilowatt-hours. This is a respectable amount of power.

So, the conclusion for this rather long-winded (and probably terribly boring) ramble is that one need to calculate the solar power system before commiting to any purchase. For the lower lattiudes solar power is terrific - for the higher lattitudes it is seldom a viable power generating scheme for the wintertime.

Btw, english is not my native language (I am from Denmark) - so please excuse me if I have made some terrible grammatical blunder!

//Kim Horsevad
Just trowing my $0.03 in....

don't think of your "normal" wind turbine, think vertical turbine....easier to use in an urban setting.
"Everyone's a pacifist between wars. It's like being a vegetarian between meals."

"If you want to test wisdom, offer it up to fools and watch how they tear it up."

"America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves." --Abraham Lincoln
You can build a small solar back up system using a marine battery,converter, 5 watt solar panel from Harbor Freight ,and a battery box. Have it set up on a dolly with solar panel attached to dolly and roll it out on sunny weekends to charge.This small system will run small lights,radio, charge cell phone ect. This is only ment for small short blackout periods not to run tv's,frig,freezer..I through together a few yrs ago a expediant system using a marine battery,converter and a auto florecent light so the spooks wouldnt come get my son who at the time was peranoid of Budda of all people lol.

Forum Jump:

Users browsing this thread: 1 Guest(s)