Solar powered AC air conditioning, a bummer or a challenge?

[PhillyTitan]

Inverter, panels, and controllers have nothing to do with battery weight and size. Battery capacity is totally dependent on daily watt hour usage. So if you use 4200 watt hours each day, you are going to need a 21,000 wh (21 Kwh) battery.

Holy smokes! So technically, this is just the case if I wanted the bank to last 5 years?

Did you calculate the fact that this will only be running 150-200 days/year? Could you say roughly 10 kWh supply would last 5 years if you only needed that much kWh would be running for half the days of the year or am I off base?

[Sunking]

Sorry sunking I had to reread each section of your post a couple times and still didn't get it all.
First, I was talking about 2x 200 ah agm batteries at 12v each. I don't have the knowledge what is proper. Whether to wire them in series to make 24volts or in parallel to stay at 12v. Advantages/disadvantages??
I know that the lower priced, all-inclusive 1Kw solar kits come with a 12v charge controller, so I was aiming at keeping the system at that.

I am totally flexible and purchase a higher rated controller and inverter if it means I can get down to under 1000 lbs of batteries.

Inverter, panels, and controllers have nothing to do with battery weight and size. Battery capacity is totally dependent on daily watt hour usage. So if you use 4200 watt hours each day, you are going to need a 21,000 wh (21 Kwh) battery.

For a system of 1000 watts o rmore will require a minimum of 24 volt battery. However 48 volt is more economical and more efficient. So for a 21 Kwh battery the required Amp Hours are:

875 AH @ 24 volts
475 AH @ 48 volts.

For a 24 volt system you are looking at using 4 Rolls 6 volt 820 AH batteries (6CS25PS) wired in series to make 24 volts.

[PhillyTitan]

Sorry sunking I had to reread each section of your post a couple times and still didn't get it all.
First, I was talking about 2x 200 ah agm batteries at 12v each. I don't have the knowledge what is proper. Whether to wire them in series to make 24volts or in parallel to stay at 12v. Advantages/disadvantages??
I know that the lower priced, all-inclusive 1Kw solar kits come with a 12v charge controller, so I was aiming at keeping the system at that.

I am totally flexible and purchase a higher rated controller and inverter if it means I can get down to under 1000 lbs of batteries.

[Sunking]

So can someone run the math and apply it to my situation?
I don't know the Ah rating of shockah's $300 battery, but let's say they're 200ah.

2x 200ah batteries, for $600
running 660 watts for 5-7 hours a day.
150 days/ year average.

200 AH is meaningless without a voltage. So I can only assume you are talking about 6 volt 200 AH golf cart batteries wired in series to make 12 volts. 12 volts x 200 AH = 2400 watt hours. For an off-grid battery system you size the battery to give you 5 days run time. In reality this only gives you 2.5 days as you never want to discharge the batteries more than 50%. Put another way you only discharge your batteries 20% each day.

Battery cycle life and Depth of Discharge is directly related. The deeper you discharge them, the fewer cycles you will get out of them. Here is a chart to display:



Discharge 20% each day and you get about 5 years, 50%just over a year, 100% just a couple of months. In your case using a 12 volt 200 AH is 2400 watt hours and you want to drain 600 watts x 7 hours = 4200 watt hours. Not going to work.

So your air conditioner uses 600 watts and you want to run it 7 hours per day. 600 watts x 7 hours = 4200 watt hours. That means you need a minimum of 4200 watt hours x 5 days = 21,000 watt hours or 21 Kwh. To find the battery AH capacity is easy Amp Hours = Watt Hours / Battery Voltage. So you get:

1750 AH @ 12 volts
875 AH @ 24 volts
438 AH @ 48 volts

To determine cost a good 5 year battery will cost you $220/Kwh and weighs roughly 55 pounds per Kwh. So for a 21 Kwh battery will cost around 21 x $220 = $4620 and weigh in around 21 x 55 pounds = 1155 pounds.

[PhillyTitan]

Look to the old South, as to how people can live without Air Conditioning. It's nice to have, but seldom a "live or die" situation.

Wide porches, build to take advantage of local breeze, shaded windows, insulated, thermal mass.

We are going into our 3rd, 90+ day here, and passive design has our indoor temp at 72F, 4pm.

Mike you are correct. But the old movies where they are sitting on the porch fanning themselves in the 95* weather with >95% humidity, and sweating like pigs doesn't appeal to me. They looked really miserable. The only wind in central Alabama is in the city or on top of a mountain (other than our infamous tornados).

I'd be interested to read more on the setup for your "passive design". Care to share any more details?

[Mike90250]

Look to the old South, as to how people can live without Air Conditioning. It's nice to have, but seldom a "live or die" situation.

Wide porches, build to take advantage of local breeze, shaded windows, insulated, thermal mass.

We are going into our 3rd, 90+ day here, and passive design has our indoor temp at 72F, 4pm.

[PhillyTitan]

So can someone run the math and apply it to my situation?
I don't know the Ah rating of shockah's $300 battery, but let's say they're 200ah.

2x 200ah batteries, for $600
running 660 watts for 5-7 hours a day.
150 days/ year average.

Please show the math how you came up with the $ amount per KWh.

[PhillyTitan]

However with Off-Grid there is no way possible to save any money. It will cost you many times more than buying it. 10 years ago 20 times more, today with government money pouring into panel manufacturing down to 10 times more. So don't take anything off-grid unless you have no other alternative. There is no justification for doing so.

I would agree with you if the cost of doing so were the only factor. In my opinion there can be tremendous
Advantages of energy independence but that's a discussion for another thread.

I'm really talking about the feasibility of making a low cost solution for air conditioning that happens to also be off grid. (This isn't a true off grid house, you know. I'm only talking about the addition.)Then maybe when the time is right, or if the unthinkable happens, apply what I've learned to take it to the next step.

I'm not one of those geeky prepers who keeps a bug out vehicle, and a cabin in the woods with 1000 pounds of canned food. But if the US dollar ever collapsed, or I there is a super virus outbreak, or Iran takes us back to the Stone Age when they develop an EMP device, then I'd rather not be one of those who died immediately because I didn't have a plan B.

If a low cost solution IS viable, then maybe I'll start looking into ways to make it more viable.
EG building my own solar panels, and batteries, improving circuit designs and building the components myself, etc. I am trying to start small but I really have a grand vision if it works out.

[Sunking]

There is no need to insult me sunking.

Was not trying to Insult You, get your attention real fast before you make a huge mistake. By federal law, public utilities are required to off Grid Tie systems. What is not Law is that the utility must pay you retail for what you sell them. In my home state of TX you can connect to the Grid, but dpending on where you are located in TX you may only get 5-cents for what you sell, and buy at 13 cents. Where I was rates are 7.6-cents per Kwh for all you want up to 2000 Kwh then the price drops to 7.2-cents above 2000 Kwh. To grid tie rates go up to 13-cents for what you buy, and 5 cents for what you sell.

You will have to call you local utility to get details. You should be thankful to live in AL where there is no state requirement for Net Metering. That means you have very low rates and abundant supplies of energy. In states with Net Metering Laws electric rates are much higher to cover the cost at your neighbors expense.

However with Off-Grid there is no way possible to save any money. It will cost you many times more than buying it. 10 years ago 20 times more, today with government money pouring into panel manufacturing down to 10 times more. So don't take anything off-grid unless you have no other alternative. There is no justification for doing so.

[PhillyTitan]

Alabama Power doesn't have a statewide policy on net metering, and you have to talk directly to the utility, but they can (and have) approved solar grid tie installations.

That's going to be way more cost effective than a battery based system.

You mean going guerilla? If you have an older bidirectional mechanical meter - maybe. But you risk disconnection, fines etc.

Cool. I remember visiting the Alabama Power company website and it seemed to me like they purposefully left any information out on gt systems in their green energy section.

I do get that it will save money on the long and short run. But saving money is only part of the point. I'm really trying to get a feel on whether it could possibly be a cost effective off grid, which so far I'm only getting a resounding "NO"

Guerrilla? No, I'm just curious.

[billvon]

Ok, so GT is grid-tie? That's really what I'm talking about not wanting. Alabama Power has exactly zero benefits/breaks nor is it an option if you wanted to do it.

Alabama Power doesn't have a statewide policy on net metering, and you have to talk directly to the utility, but they can (and have) approved solar grid tie installations.

I haven't even considered it at this point, but if I can't get a solution, then I may look into a GT system.

That's going to be way more cost effective than a battery based system.

Is it even possible to benefit from a GT system without permission from the power company?

You mean going guerilla? If you have an older bidirectional mechanical meter - maybe. But you risk disconnection, fines etc.

[PhillyTitan]

Simple 5th grade math and 30 plus years as a Electrical Engineer who designs the stuff.

Run these numbers or have a 5th grader check the math.

For every Kwh you intend to use a day, the battery will cost you roughly $1100 to $1200. That battery will last you roughly 5 years. In 5 years will provide you with 1825 Kwh. That means the Kwh cost just in battery alone will cost you $1100/1825 Kwh = $.602 per Kwh. The POCO charges you around 10 to 11 cents.

You want to use roughly 4 Kwh per day. Are you ready to spend $4500 right now for the battery, and in 5 years replace it at even higher cost? That is what you are asking for.

In addition you are incorrect about incentive in Alabama. The info is extremely easy to find and anyone can find it in 5 seconds or less. Alabama Incentives.

There is no need to insult me sunking. I coming to you people for solutions and asking for your help. I can get condescension at the xbox forums.
I'll look closer later, but at first glance, there appears to be no state-provided or Alabama Power provided benefit for a grid tie setup. I did see one for TVA customers though.

[PhillyTitan]

Factual figures from one of my products.
$300 AGM Battery...
216WH daily use...
X 365 = 78840WH annually...
X 5years = 394200WH
/1000 = 394.2KWH of service life
$300 / 394.2 = 76¢ per KWH

^^^ and that doesn't include the cost of the panels, charge controllers, wiring and hardware.

Also, consider the battery may last only 3 years,,, raising the ¢ per kwh figure.

Thanks. That's the kind of figures I'm looking for.

[Sunking]

If Sunking's figures are fact, then I'm still interested in knowing where the figures came from. Anyone?

Simple 5th grade math and 30 plus years as a Electrical Engineer who designs the stuff.

Run these numbers or have a 5th grader check the math.

For every Kwh you intend to use a day, the battery will cost you roughly $1100 to $1200. That battery will last you roughly 5 years. In 5 years will provide you with 1825 Kwh. That means the Kwh cost just in battery alone will cost you $1100/1825 Kwh = $.602 per Kwh. The POCO charges you around 10 to 11 cents.

You want to use roughly 4 Kwh per day. Are you ready to spend $4500 right now for the battery, and in 5 years replace it at even higher cost? That is what you are asking for.

In addition you are incorrect about incentive in Alabama. The info is extremely easy to find and anyone can find it in 5 seconds or less. Alabama Incentives.

[Shockah]

Battery cost alone is about 60-cents per Kwh that you get to replace about every 5 years if you use a good high quality battery.

If Sunking's figures are fact, then I'm still interested in knowing where the figures came from. Anyone?

Factual figures from one of my products.
$300 AGM Battery...
216WH daily use...
X 365 = 78840WH annually...
X 5years = 394200WH
/1000 = 394.2KWH of service life
$300 / 394.2 = 76¢ per KWH

^^^ and that doesn't include the cost of the panels, charge controllers, wiring and hardware.

Also, consider the battery may last only 3 years,,, raising the ¢ per kwh figure.