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

[inetdog]

Well, I think you're talking about two different things here.

One is a capacitive (leading) power factor, which is the converse of the inductive (lagging) power factor. That does indeed give inverters trouble; fortunately it is very rare, since no one puts large pure capacitive loads on AC power. About the only way I could see that happening is if an inductive load with power factor correction caps suddenly loses its inductive load due to a breaker tripping or something.

The other is nonlinear loads, or loads with high harmonic content. These are also harder for inverters to drive, and are generally caused by peak rectification in older power supplies and electronic ballasts. The result of this is that the current waveform is very "peaky" - it might only deliver current for a few milliseconds out of an 8 millisecond half-cycle. The reason this is such a problem is that to deliver (say) 10 amps to a load, you might have to deliver 40 amps at the peak of the waveform and almost nothing for the rest of the waveform. Thus the inverter has to deliver 40 amps instead of 10 for the same load, leading to problems that range from overheating and buzzing to blown output stages. It also leads to nasty problems like neutral currents that can be several times higher than any of the phase currents.

Fortunately modern large power supplies are required to incorporate power factor correction to reduce this problem.

True, and the difference between the two types of low power factor is usually categorized as displacement power factor (linear loads with capacitive or inductive components) and distortion power factor (non-linear loads in general.)
However, all other things being equal, a power supply which charges a capacitor from the peak of the AC waveform will exhibit both a displacement component and a distortion component to the low PF. The displacement portion will be capacitive in direction.

[billvon]

Although the inverter spec may indicate an allowed power factor only, be aware that not all circuits can handle a capacitive low power factor (rarely ever seen except with switching power supplies and some lighting loads) as well as they can handle an inductive low power factor.

Well, I think you're talking about two different things here.

One is a capacitive (leading) power factor, which is the converse of the inductive (lagging) power factor. That does indeed give inverters trouble; fortunately it is very rare, since no one puts large pure capacitive loads on AC power. About the only way I could see that happening is if an inductive load with power factor correction caps suddenly loses its inductive load due to a breaker tripping or something.

The other is nonlinear loads, or loads with high harmonic content. These are also harder for inverters to drive, and are generally caused by peak rectification in older power supplies and electronic ballasts. The result of this is that the current waveform is very "peaky" - it might only deliver current for a few milliseconds out of an 8 millisecond half-cycle. The reason this is such a problem is that to deliver (say) 10 amps to a load, you might have to deliver 40 amps at the peak of the waveform and almost nothing for the rest of the waveform. Thus the inverter has to deliver 40 amps instead of 10 for the same load, leading to problems that range from overheating and buzzing to blown output stages. It also leads to nasty problems like neutral currents that can be several times higher than any of the phase currents.

Fortunately modern large power supplies are required to incorporate power factor correction to reduce this problem.

[inetdog]

It does not directly affect the power your meter reports, which is what you pay for.

For reasonable power factors - no. If you make the load capacitive or inductive enough your inverter won't be able to handle it, of course. But 99% of the loads out there won't be a problem.

Although the inverter spec may indicate an allowed power factor only, be aware that not all circuits can handle a capacitive low power factor (rarely ever seen except with switching power supplies and some lighting loads) as well as they can handle an inductive low power factor.

[billvon]

So the bad power factor equipment does not affect the true electrical consumption?

It does not directly affect the power your meter reports, which is what you pay for.

I don't have to worry any bad power factor as long as my inverter can manage the load?

For reasonable power factors - no. If you make the load capacitive or inductive enough your inverter won't be able to handle it, of course. But 99% of the loads out there won't be a problem.

[inetdog]

So the bad power factor equipment does not affect the true electrical consumption? the amperage and the watts reported from the kill-a-watt meter or the clamp amp meters tell the true consumptions? I don't have to worry any bad power factor as long as my inverter can manage the load? That will be good news!
Thank you guys.

The low power factor equipment may require larger AC wiring, since the wiring is sized based on the current it carries. And all inverters will have a limit on the maximum VA they can deliver, which may be a little as 5% or as much as 30% higher than the wattage limit. The watts rather than the VA will determine the power drawn from the batteries though.

[russ]

So the bad power factor equipment does not affect the true electrical consumption? the amperage and the watts reported from the kill-a-watt meter or the clamp amp meters tell the true consumptions? I don't have to worry any bad power factor as long as my inverter can manage the load? That will be good news!
Thank you guys.

By US rules the power factor is a problem for the utilities - elsewhere may be different. Where I live now is like the US in that regard.

[paulcheung]

It is complete FRAUD. For starters there are not enough inductive loads to worry about in a residence. Industrail is different where the can be running multiple large horse power motors.

But the nail in the coffin, is utilities do not monitor, record. or bill for Vars. So those folks who claim it lowered their bills are brainwashed. Utilities only charge for True Power, not VARs

So the bad power factor equipment does not affect the true electrical consumption? the amperage and the watts reported from the kill-a-watt meter or the clamp amp meters tell the true consumptions? I don't have to worry any bad power factor as long as my inverter can manage the load? That will be good news!
Thank you guys.

[SunEagle]

Power factor correcting capacitors

Both Sunking and russ are correct about capacitors doing nothing to reduce a homeowners electric bill. They can reduce the cost at an industrial facility that has a power factor penalty and gets billed for it being below what the Utility decides it should be.

Of course you now have the problem that capacitors can increase costs due to the harmonic distortion they generate. This distortion will affect all types of equipment in the facility by reducing the "power quality" of the electrical distribution system and increasing losses (overheating motors and variable frequency drives) due to that distortion. To rectify that you will need to use a combination capacitor with harmonic mitigating hardware like an LC Filter or phase shifting a couple of transformers which cancels out some of the harmonics. There are lots of ways to improve power factor and reduce harmonic distortion which will save a facility a lot of money over a period of time.

[Mike90250]

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

I know very well what you are trying to talk about, and will now just let your words stand - by themselves in misconception corner.
In actuality, the inductance in your DC wires, swamps out most of the available capacitance. And AC motor caps (both Run & Start) have nothing to do with DC, which would instantly damage an AC motors windings. I tried to hint at the phase relationship in my earlier comment, but was apparently too obtuse.
About the only thing I can agree with you this week, is that some 12VDC gear will run directly from PV panels.

[russ]

Philly, You can find anything one wants on youtube - for, against and could care less on any topic. Maybe 95% of youtube posts are just some fool with a video camera that wants to act like an expert but knows nothing.

The capacitors for power factor improvement are an old and long running scam. I seriously doubt those are engineers trying to sell it and even if they are engineers they are still thieves. In the US, residential power costs would not really change - one is not billed in that manner.

Commercial is a different story and should not be confused with residential.

[billvon]

Can a Capacitor bank increase the power factor on the inverter or the motors? In Jamaica there is a new trend that some engineers is sell some capacitor bank to increase the efficiency on motors on the house hold circuit. They come to the house and measure the power factors on the refrigerators, water pumps and wash machines etc. If they find any item that has bad power factors they put a capacitor bank to increase the power factor close to 1. they charge from $150 to $500 US per capacitor bank. Some people say they do save a good amount electricity consumption.

That won't save any money. Electric meters measure real power, not reactive power.

If your power factor is very bad then correcting it will help with an inverter trying to drive that load. However the load has to be pretty bad (i.e. you are running large three phase ventilation fans or pumps) for it to make a big difference. For facilities like municipal water pumps utilities often use large capacitor banks to correct power factor because large pumps can be very reactive.

In the OP situation I wonder if he use most of the time on sunny time. Can he get 1200 watt PV panels and a 1500watts pure sine inverter with 3000watts surge capacity, and a 24 volts bank of AGM batteries with 200 amps hours. only use on sun hours and may be one hour after hour? would that work?

That would work for a while. But spend enough summer evenings with the A/C on and you'll kill the bank pretty quickly.

[PhillyTitan]

In conclusion

Well, I guess the answer to this thread's title is overwhelmingly BUMMER.

I found a YouTube channel called DIYWORLD where this guy did successfully run his 120VAC air conditioner overnight one time time in his off-grid camper trailer. But I believe he had several batteries, and at least 2kW worth of solar panels and his batteries saw significant drain (which I have learned here will lower your battery cycles significantly. So this is not a good idea and I shouldn't even try.

I will setup a solar panel system still, but I will have to revisit the drawing board to see how I'm going to do it.
I will now retire to my dark corner and silently weep.

[Sunking]

Can a Capacitor bank increase the power factor on the inverter or the motors? In Jamaica there is a new trend that some engineers is sell some capacitor bank to increase the efficiency on motors on the house hold circuit. They come to the house and measure the power factors on the refrigerators, water pumps and wash machines etc. If they find any item that has bad power factors they put a capacitor bank to increase the power factor close to 1. they charge from $150 to $500 US per capacitor bank. Some people say they do save a good amount electricity consumption

It is complete FRAUD. For starters there are not enough inductive loads to worry about in a residence. Industrail is different where the can be running multiple large horse power motors.

But the nail in the coffin, is utilities do not monitor, record. or bill for Vars. So those folks who claim it lowered their bills are brainwashed. Utilities only charge for True Power, not VARs

[paulcheung]

Will not do anything. A battery is a extremely large capacitor that does not leak and has magnitude of several hundred times more capacitance than a super capacitor. What you are wanting to believe is you can change the level of a lake by peeing in it. Good ole ABE is a crack pot who knows nothing of electronics or power.

The issue is not with the battery, it is the inverter itself that cannot supply high starting currents and low Power Factors. Inverters are rated in KVA at some power factor. The best of inverters can only handle a power factor of .7 That would mean a 1 Kw inverter can only supply up to 1.4 Kva starting power. If you had say a 600 watt motor with a 7 x FLA it would take an inverter of 4500 KVA @ .7PF or a 3200 watt inverter to run a 600 watt motor. No way around it.

This is exactly why off-gridder use DC powered refrigeration equipment, and do without Air Conditioning unless money is no object. You are going to have to accept that fact. YOu wanna stay cool, use AC power, or dump a lot of bucks needlessly. If you just have to take your Air Conditioner off-gir you are going to have to use a DC split Air Conditioner. They are very expensive but less expensive overall trying to power conventional Air Conditioning with AC power from solar.

If you are smart and wise with your money, forget trying to cool or take anything off-grid. Take that money and invest it. In 10 years you should catch a double or quadruple. Go solar and it is all gone.

Can a Capacitor bank increase the power factor on the inverter or the motors? In Jamaica there is a new trend that some engineers is sell some capacitor bank to increase the efficiency on motors on the house hold circuit. They come to the house and measure the power factors on the refrigerators, water pumps and wash machines etc. If they find any item that has bad power factors they put a capacitor bank to increase the power factor close to 1. they charge from $150 to $500 US per capacitor bank. Some people say they do save a good amount electricity consumption.

In the OP situation I wonder if he use most of the time on sunny time. Can he get 1200 watt PV panels and a 1500watts pure sine inverter with 3000watts surge capacity, and a 24 volts bank of AGM batteries with 200 amps hours. only use on sun hours and may be one hour after hour? would that work?

[Sunking]

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.

Will not do anything. A battery is a extremely large capacitor that does not leak and has magnitude of several hundred times more capacitance than a super capacitor. What you are wanting to believe is you can change the level of a lake by peeing in it. Good ole ABE is a crack pot who knows nothing of electronics or power.

The issue is not with the battery, it is the inverter itself that cannot supply high starting currents and low Power Factors. Inverters are rated in KVA at some power factor. The best of inverters can only handle a power factor of .7 That would mean a 1 Kw inverter can only supply up to 1.4 Kva starting power. If you had say a 600 watt motor with a 7 x FLA it would take an inverter of 4500 KVA @ .7PF or a 3200 watt inverter to run a 600 watt motor. No way around it.

This is exactly why off-gridder use DC powered refrigeration equipment, and do without Air Conditioning unless money is no object. You are going to have to accept that fact. YOu wanna stay cool, use AC power, or dump a lot of bucks needlessly. If you just have to take your Air Conditioner off-gir you are going to have to use a DC split Air Conditioner. They are very expensive but less expensive overall trying to power conventional Air Conditioning with AC power from solar.

If you are smart and wise with your money, forget trying to cool or take anything off-grid. Take that money and invest it. In 10 years you should catch a double or quadruple. Go solar and it is all gone.