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

[PhillyTitan]

I hope I'm posting this thread in the right section. I'm a newbie and don't know any better.
I really want a low cost solution (low cost build and maintenance) for a completely off-grid addition that I'm planning for my house. I'm building a small bonus room/bathroom addition to my house (11x25').

Although heating is required by local building codes, it's not required to survive here. However air conditioning is an absolute must if I'm going to live with a family in such tight quarters. I'm in the deep south where 100% humidity is not uncommon in the summer. I've looked into 24 volt DC units like they would use in yachts, but it seems prohibitively expensive. I'm just too poor to have a system that costs 10-15 grand.

It seems I can run DC lights and small AC appliances with little solar power and a small inverter. But the real energy hog is the air conditioner. I spoke to others about this problem and everyone I speak to seem to think an 120 VAC air conditioner should not be attempted on solar power .

I figure if I have 1kW array, a 200ah battery or two, and some heavy duty insulation, and a inverter just the right wattage rating to start and run the A/C unit, then I could get away with running a high efficiency 6000 BTU window unit air conditioner for 5-7 hours a day. The lights and small appliances can be run on a separate, smaller system.

[PhillyTitan]

Let me sum this up this setup:

- a highly insulated, 11'x25' room
- 1kW solar array with homemade solar tracker
- 2x 200ah 12-volt batteries
- a 6000 BTU AC air conditioner (620 watts) running 5-7 hours/day on the sunniest/hottest days.
- an inverter running on the minimum power to start and run the AC.


Am I really that crazy to think that this setup is possible? Or is my math not even close? If I am close, then how much more would it take to be a safe bet?

[Sunking]

Am I really that crazy to think that this setup is possible? Or is my math not even close? If I am close, then how much more would it take to be a safe bet?

Here is how Crazy you are and what you are asking for.

You pay the mean ole electric company around 11-cents per Kwh. Anything you take off-grid will cost you 10 times more for the rest of your life. 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. You would be crazy to take an Air Conditioner off the grid. Heck you would be crazy to take anything off-grid.

[billvon]

Am I really that crazy to think that this setup is possible? Or is my math not even close? If I am close, then how much more would it take to be a safe bet?

Sure, it's possible. It will be more expensive than using utility power, but if you want to do it and can afford it, go for it. Keys:

1) Insulate as much as possible. I'd go with 6" walls minimum.
2) North facing windows only to reduce heat gain.
3) Use a mini-split AC and prioritize efficiency over everything else.
4) Do NOT use batteries; use a GT inverter. If you want backup get an SMA inverter with "secure power" option.

[PhillyTitan]

Here is how Crazy you are and what you are asking for.

You pay the mean ole electric company around 11-cents per Kwh. Anything you take off-grid will cost you 10 times more for the rest of your life. 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. You would be crazy to take an Air Conditioner off the grid. Heck you would be crazy to take anything off-grid.

I understand where you're coming from, but there are no guarantees that the power company will be there for me forever with low energy rates. I've seen some projections that the world's oil will run out in the next 100 years. I'm sure non-renewable energy costs will skyrocket long before that.

Where did you come up with those figures?

[PhillyTitan]

Sure, it's possible. It will be more expensive than using utility power, but if you want to do it and can afford it, go for it. Keys:

1) Insulate as much as possible. I'd go with 6" walls minimum.
2) North facing windows only to reduce heat gain.
3) Use a mini-split AC and prioritize efficiency over everything else.
4) Do NOT use batteries; use a GT inverter. If you want backup get an SMA inverter with "secure power" option.

Never heard of those things, but you got me interested.

[PhillyTitan]

4) Do NOT use batteries; use a GT inverter. If you want backup get an SMA inverter with "secure power" option.

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. The power company is only regulated by federal guidelines and Alabama has no legislative policy at all for incorporating solar power. My guess is that there is a good bit of overhead saved by the power company by not being required to market and operate grid tie systems.

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

[Shockah]

I understand where you're coming from, but there are no guarantees that the power company will be there for me forever with low energy rates. I've seen some projections that the world's oil will run out in the next 100 years. I'm sure non-renewable energy costs will skyrocket long before that.

Where did you come up with those figures?

Respectfully, ^^^ you've just proven you are crazy.

The "100 year" projection is myth vs Sunking's figures are fact...
yet you question FACT and believe MYTH.

[Shockah]

Ok, so GT is grid-tie?

Yes.

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

No.

[PhillyTitan]

Respectfully, ^^^ you've just proven you are crazy.

The "100 year" projection is myth vs Sunking's figures are fact...
yet you question FACT and believe MYTH.

I admit that there is no way to know for sure that "100 year" projection is true. Only that data is supporting supply has passed it's maximum output. A educated guess is not capable of being a myth.

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

[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.

[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.

[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.

[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.

[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.