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

[Mike90250]

A mini split (the variable speed models) have a poly-phase adjustable motor, so they can start slowly and do not have a "death spike" like a window shaker would. They can be set to low speed only and only consume a couple hundred watts instead of 1500 watts.

[K7ABE]

Hey Sunking, I really mean types of batteries not brands. I really have no knowledge at all about the subject, only that AGM is supposedly very good and low on maintenance.




Abe I've said this before, but I don't mind saying one more time. It's the individual components that I'd like to keep down in cost. For instance, a 24VDC 12,000 BTU air conditioner would be at least $1700.00 (<-- the only one I found with a price tag on it). Or a solar array professionally installed for $10k. A few batteries for a couple hundred each is not an extreme cost. The first question on this thread was is it viable to have a sustainable working system that won't break the bank when one of the individual components fail.

Google off grid air conditioner. About the third or fourth thing down was a Mother Earth News article that describes using an air conditioner that uses the water over the condenser for improved efficiency. Says pumps the water over the condenser but what I saw in mine was the fan splash the water up onto the condenser. And I believe the article said these little window units are about $100 each, 400W, & 5000BTU. Similar to the units I have.
Abe

[paulcheung]

To the OP, when is these 5 to 7 hours operation time? during the day when sun is shining or in the dark night when you go sleep?

[billvon]

Google off grid air conditioner. About the third or fourth thing down was a Mother Earth News article that describes using an air conditioner that uses the water over the condenser for improved efficiency. Says pumps the water over the condenser but what I saw in mine was the fan splash the water up onto the condenser.

Hmm. Every A/C I've seen in stores recently does this. It's pretty simple; just design the drip pan to drain towards the fan, then put the fan close to the surface of the drip pan.

[K7ABE]

Hmm. Every A/C I've seen in stores recently does this. It's pretty simple; just design the drip pan to drain towards the fan, then put the fan close to the surface of the drip pan.

Yes I replaced three of the old ACs with twists knobs with these units in the rentals. They use a couple hundred watts less, give you the same cooling, and run much quieter. Spending $100 for the new technology AC would save several hundred dollars in the solar panel and inverter needed to run the old technology,less efficient AC.
Abe

[billvon]

Yes I replaced three of the old ACs with twists knobs with these units in the rentals. They use a couple hundred watts less, give you the same cooling, and run much quieter. Spending $100 for the new technology AC would save several hundred dollars in the solar panel and inverter needed to run the old technology,less efficient AC.
Abe

I think the big difference between these A/C's and the inverter driven devices like the mini-split is:

1) Startup surge. With a typical induction motor you get a huge startup surge every time the compressor turns on, since induction motors try to come up to speed instantly. With an inverter drive you don't see a large surge since the motor is ramped up more slowly. This might mean that a 500 watt air conditioner needs a 1500 watt surge to start - and that all has to come from the house inverter. An inverter drive might only need 600 watts to come up to speed.

2) Cycling. A typical A/C, running under a moderate setting, might cycle on for 1 minute every 3 minutes to keep the room cool. So if your average power draw is 500 watts, it is taking 1500 watts while it is on and just a few watts when it is off to run its fan.

The above means that - even if the two A/C's are the same efficiency - the mini-split with the inverter drive will be a lot easier on the power system. In one you have to design for 1500 watt loads, in the other 600 watt loads.

An important note:
An inverter drive motor uses a _separate_ inverter to drive its own motor; this is not the house inverter. This is a detail of motor design, not a requirement. There is no reason that a window unit can't use an inverter drive, but none that I have seen do. Split systems, on the other hand, often do.

[russ]

Google off grid air conditioner. About the third or fourth thing down was a Mother Earth News article that describes using an air conditioner that uses the water over the condenser for improved efficiency. Says pumps the water over the condenser but what I saw in mine was the fan splash the water up onto the condenser. And I believe the article said these little window units are about $100 each, 400W, & 5000BTU. Similar to the units I have.
Abe

Mother Earth News? I was unaware it contains anything worth reading.

[K7ABE]

I think the big difference between these A/C's and the inverter driven devices like the mini-split is:

1) Startup surge. With a typical induction motor you get a huge startup surge every time the compressor turns on, since induction motors try to come up to speed instantly. With an inverter drive you don't see a large surge since the motor is ramped up more slowly. This might mean that a 500 watt air conditioner needs a 1500 watt surge to start - and that all has to come from the house inverter. An inverter drive might only need 600 watts to come up to speed.

2) Cycling. A typical A/C, running under a moderate setting, might cycle on for 1 minute every 3 minutes to keep the room cool. So if your average power draw is 500 watts, it is taking 1500 watts while it is on and just a few watts when it is off to run its fan.

The above means that - even if the two A/C's are the same efficiency - the mini-split with the inverter drive will be a lot easier on the power system. In one you have to design for 1500 watt loads, in the other 600 watt loads.

An important note:
An inverter drive motor uses a _separate_ inverter to drive its own motor; this is not the house inverter. This is a detail of motor design, not a requirement. There is no reason that a window unit can't use an inverter drive, but none that I have seen do. Split systems, on the other hand, often do.

A high Farad capacitor from the automotive stereo industry Would handle the inrush for a 12 volt DC system. I am not aware of any capacitors for a 120 volt AC system that will handle that load.

[Mike90250]

A high Farad capacitor from the automotive stereo industry Would handle the inrush for a 12 volt DC system.

Are you sure you are a ham ? calculate what useable power is in the cap from 13V to 12.5V

I am not aware of any AC capacitors for a 120 volt system that will handle that load.

oh boy - Capacitors can not store AC. They can phase shift AC signals. You are not a ham for sure, or else you had someone else take the test.


So at some point, this poppycock is going to stop, or we are going to either clean the thread, put a disclaimer on it of "this contains factual errors", or lock it down. Choice is yours.

[K7ABE]

I think the big difference between these A/C's and the inverter driven devices like the mini-split is:

1) Startup surge. With a typical induction motor you get a huge startup surge every time the compressor turns on, since induction motors try to come up to speed instantly. With an inverter drive you don't see a large surge since the motor is ramped up more slowly. This might mean that a 500 watt air conditioner needs a 1500 watt surge to start - and that all has to come from the house inverter. An inverter drive might only need 600 watts to come up to speed.

2) Cycling. A typical A/C, running under a moderate setting, might cycle on for 1 minute every 3 minutes to keep the room cool. So if your average power draw is 500 watts, it is taking 1500 watts while it is on and just a few watts when it is off to run its fan.

The above means that - even if the two A/C's are the same efficiency - the mini-split with the inverter drive will be a lot easier on the power system. In one you have to design for 1500 watt loads, in the other 600 watt loads.

An important note:
An inverter drive motor uses a _separate_ inverter to drive its own motor; this is not the house inverter. This is a detail of motor design, not a requirement. There is no reason that a window unit can't use an inverter drive, but none that I have seen do. Split systems, on the other hand, often do.

Spent a few hours researching inverter mini split AC units. One of the better ones I found is 650 Watts and 9000 BTU and about a thousand dollars with self install (Need a license HVAC for warranty to be valid). It still has a 15 amp fuse that allows for more than double for startup. However the operational efficacy numbers are impressive. Did my limited research miss some key points here?
Abe

[K7ABE]

Are you sure you are a ham ? calculate what useable power is in the cap from 13V to 12.5V



oh boy - Capacitors can not store AC. They can phase shift AC signals. You are not a ham for sure, or else you had someone else take the test.


So at some point, this poppycock is going to stop, or we are going to either clean the thread, put a disclaimer on it of "this contains factual errors", or lock it down. Choice is yours.

The capacitors I am talking about are 5F and 10F at 35V designed for use in 12 volt systems to handle the hi serge in stereo amps (I use one 'AT' my mobile HF amplifier to help with the peaks on side band). The 12 Volt compressors designed to run straight from the solar panel without any charge controller or inverter use panels rated at 12V with 22V peak.

The fan motor on all of the larger AC units I am aware of will not start without a capacitor. The capacitors give a DC Jolt to the AC motor to start it spinning, then it runs on AC. Capacitor start AC motors have been around for a long time it helps keep the size and expense down. And as I said I do not know of any capacitor that will start a 120 AC unit.

Many engineers seem unable to understand how things really come together to make things work.

When the reader is not able to understanding what the writer is writing about, it does not mean that the writer does not know what they're talking about.
Abe

[russ]

This poor fellow is off to research stuff in the woods of Oregon.

[Sunking]

The fan motor on all of the larger AC units I am aware of will not start without a capacitor. The capacitors give a DC Jolt to the AC motor to start it spinning, then it runs on AC. Capacitor start AC motors have been around for a long time it helps keep the size and expense down.

Stop it, you are embarrassing yourself. You have no clue what you are talking about and making ham radio operators look like fools and morons. Your credibility is completely gone here, you have proven many times you do not know a thing about electric power.

[PhillyTitan]

Hey gentlemen, I've been absent for a couple of days. One thing (probably the only) that Abe mentioned did make sense: I believe a high farad capacitor would be helpful for a startup surge in a DC situation. Could there possibly be anything that would do the same in a 120VAC arrangement? I would think someone would have mentioned that by now but it doesn't hurt to ask.

To the OP, when is these 5 to 7 hours operation time? during the day when sun is shining or in the dark night when you go sleep?

Daylight hours would be the bulk of when it's running. Maybe turn on for a couple minutes at a time during the other hours. Does that make a difference in getting the batteries charged?

[PhillyTitan]

2) Cycling. A typical A/C, running under a moderate setting, might cycle on for 1 minute every 3 minutes to keep the room cool. So if your average power draw is 500 watts, it is taking 1500 watts while it is on and just a few watts when it is off to run its fan.

Please chime in folks because this is important. I was under the impression that an air conditioner rated at "500 watts" was the power it's running while at full blast, not the average power running at different cycles.