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

[PhillyTitan]

I had an idea for my camper trailer build that May or may not work for it.
I saw a 12v air conditioner add on kit made for a truck that mounts under the dash. 7000 btu (I think).
Saws it on eBay. It would have to hang from a wall cabinet or something. I haven't found any info on weather someone has tried something like that in their home.
That would be cool if I could do that, but there would be many hurdles to overcome.

[PhillyTitan]

Preppers? I have been hearing that BS as long as I can remember - I am 69 so that goes back a ways.

Whatcha mean Russ? There are many prepers out there. You should know better than most because you lived through the Cuban missile crisis and whatnot.

[russ]

Whatcha mean Russ? There are many prepers out there. You should know better than most because you lived through the Cuban missile crisis and whatnot.

Yep, I remember that - all a bunch of hokum - tempest in a tea cup.

[billvon]

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.

Solar-PV will be one of the first casualties from any sort of EMP event. Long wire runs and large inductive loops.

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.

In general "building your own" solar panels and batteries isn't going to do much, will take forever, will cost you far more than buying commercial and won't teach you much about solar. It would be like trying to build your own car, and starting out by planting a rubber tree for the tires. Sure, you will learn a lot about rubber trees, but not much about modern cars.

If you really want to learn about solar there are plenty of components out there you can bolt together and play with. You can quite easily build a small system to (for example) run some yard lights at night. You'll learn about battery charging, hours of effective sun, the role panel azimuth and elevation play, battery temperature compensation etc. And if you burn through a pair of GC2's in your first month you're only out about $300.

[K7ABE]

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.

Try crunching those numbers with a $5 or $10 AGM battery. Cell towers keep their battery topped off and cycled them out every one or two years. The battery still may last five to eight years after that. This will drop your battery cost down to the penny or two per kilowatt.
Abe

[K7ABE]

I had an idea for my camper trailer build that May or may not work for it.
I saw a 12v air conditioner add on kit made for a truck that mounts under the dash. 7000 btu (I think).
Saws it on eBay. It would have to hang from a wall cabinet or something. I haven't found any info on weather someone has tried something like that in their home.
That would be cool if I could do that, but there would be many hurdles to overcome.

A refrigerator and freezer are available with 12 volt compressor that will run off of a solar panel with no batteries. The compressors are available by there self. Using them for AC units is an idea I have on the back burner.
Abe

[russ]

Try crunching those numbers with a $5 or $10 AGM battery. Cell towers keep their battery topped off and cycled them out every one or two years. The battery still may last five to eight years after that. This will drop your battery cost down to the penny or two per kilowatt.
Abe

Still being funny - you have no idea what you are posting - pure baloney!

This is not a duct tape site where one is encouraged to cobble stuff together.

[K7ABE]

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.

Compare the life cycle charge between Interstate golf cart batteries, Trojan batteries, And rolls-royce batteries. The ratings look close at first but the golf cart batteries are rated at 20% discharge, The Trojans are rated at 50 percent discharge, And the rolls-royce at 80% discharge. If you treat a better batteries like the cheap batteries they will last 15 or 20 years. If you treat the cheap batteries like the better batteries they only last 1 or 2 years. The manufacturers numbers are deceptive at first look.
Abe

[K7ABE]

Still being funny - you have no idea what you are posting - pure baloney!

This is not a duct tape site where one is encouraged to cobble stuff together.

The original poster stated he does not have a few thousand dollars to work with. A cheap high frequency inverter will not handle the inrush of an air conditioner. I have a 2500 5000 that went into default and has not worked since I try to it. The low-frequency heart 2k does handle the inrush of the air conditioner. There is a heart 2.5k on ebay for about $600. A new low frequency inverter that will handle his air conditioner will cost two or three thousand dollars. I hope this is not a site where you discourage people or run them off if they cannot buy your new products.
Abe

[K7ABE]

Solar-PV will be one of the first casualties from any sort of EMP event. Long wire runs and large inductive loops.



In general "building your own" solar panels and batteries isn't going to do much, will take forever, will cost you far more than buying commercial and won't teach you much about solar. It would be like trying to build your own car, and starting out by planting a rubber tree for the tires. Sure, you will learn a lot about rubber trees, but not much about modern cars.

If you really want to learn about solar there are plenty of components out there you can bolt together and play with. You can quite easily build a small system to (for example) run some yard lights at night. You'll learn about battery charging, hours of effective sun, the role panel azimuth and elevation play, battery temperature compensation etc. And if you burn through a pair of GC2's in your first month you're only out about $300.

Solar panels are semiconductors much like a diode, transistor, or IC chip. They start with a thin slice of quartz that is masked, then an etchant is used and they are built up in the same way any semiconductor is. They are very sensitive to EMP, even RF radiation. Solar panels stored inside metal buildings may work after a large EMP.
Abe

[Shockah]

Try crunching those numbers with a $5 or $10 AGM battery. Cell towers keep their battery topped off and cycled them out every one or two years. The battery still may last five to eight years after that. This will drop your battery cost down to the penny or two per kilowatt.
Abe

not only did you post this statement, you actually believe it is viable...

[inetdog]

Solar panels are semiconductors much like a diode, transistor, or IC chip. They start with a thin slice of quartz that is masked, then an etchant is used and they are built up in the same way any semiconductor is. They are very sensitive to EMP, even RF radiation. Solar panels stored inside metal buildings may work after a large EMP.

And here I thought that they used silicon (in a high purity crystal) rather then quartz (~silica).
For your own sake refrain from making too many careless or incorrect statements, as it will damage any credibility you are trying to build up.

PS: EMP will generally not affect small scale wiring like the internal tabs and wires of PV panels. Now any that are connected to long wires at the time of the EMP may be a different story. I would say that they are more sensitive to RF (at high power) than to EMP. Do not put solar cells into your microwave. They will behave just as interestingly as CDs.

[K7ABE]

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?

A few easy numbers; 10 amps at 120 volts is 100 amps at 12 volts, both are 1200 watts. If you used 1200 Watts from your batteries it takes more than 1200 watts to recharge them. There is also loss due to wiring, electronic inefficacy, and dust on the panels. Ad in about 20% loss from solar panel to AC output at the inverter if using MPPT charge controller. And up to 50% loss if using PMW charge controller. You will not get the full rating of your panels all the daylight hours. Where I live in Oregon it is 2.9 times my panel rating I get in one day. Where I live in Texas it is five times the panel rating I get in a day. Charts are easily found on internet to let you know how you rate in your area. I've found them more accurate than I first believed.
Abe

[K7ABE]

not only did you post this statement, you actually believe it is viable...

Yes I have proven a viable by using it for the last 6 years.

[K7ABE]

And here I thought that they used silicon (in a high purity crystal) rather then quartz (~silica).
For your own sake refrain from making too many careless or incorrect statements, as it will damage any credibility you are trying to build up.

PS: EMP will generally not affect small scale wiring like the internal tabs and wires of PV panels. Now any that are connected to long wires at the time of the EMP may be a different story. I would say that they are more sensitive to RF (at high power) than to EMP. Do not put solar cells into your microwave. They will behave just as interestingly as CDs.

A requirement for a course I took 2 or 3 years ago was to design a company that made solar panels. We had to know what the equipment was to grow the crystals, where to buy the equipment, The advantages of avoiding contamination by manufacturing our own quartz wafers (made from fused silica), the whole process from raw materials to finished solar panels. Has the industry changed that much in the last couple years?

The RF energy from my radio equipment does disrupt the charge controllers. So far I have not noticed any permanent damage. With me the whole system is about the radios. It is useless to me if i cannot use the radio.
Abe