Inverter air conditioning and solar power

[Gitano439]

I want to know if you have an inverter Air Conditioner, and the things of been an inverter Air Conditioner is that it take AC electricity and converts to DC, so the motor on the compressor can be adjusted to the desire BTU. Why you don’t have a bank of batteries (solar rechargeable), and connects directly to the air conditioner omitting the AC electricity, and perhaps been more efficient in the process because you’re omitting the conversion of electricity.

[paul_h]

I doubt batteries can power a/cs, they run on high voltage, that's a lot of big batteries.
You can run mixed power (has to be mixed due to lack of batteries and when there's not enough solar power)
http://www.sanyoaircon.com/products/solar-powered/

[Imp]

Sanyo do this and Vaillant and others are exploring the technology. Early days though and this will be very expensive. the only validity in the product is not the energy efficiency but the need to "be seen to be green" by the manufacturer.

Life cycle costs of 10 years on current equipment COP's vastly outweigh the investment and running costs for Solar unless you already have the technology installed.

[Gitano439]

I read the brochure of the Sanyo system and Sanyo use an inverter to turn 12 volt Dc from the solar panels to 240 volt AC to move the air conditioner. But if the air conditioner had an inverter inside that changes 240 volt in to 12 volts dc to run the compressor, why you can took out the inverter and give direct current from a bank of batteries.

[The Viking]

But if the air conditioner had an inverter inside that changes 240 volt in to 12 volts dc to run the compressor, why you can took out the inverter and give direct current from a bank of batteries.

Right thought but wrong input...

The DC compressors in A/C systems runs on much higher voltage than that, sorry.

[paul_h]

I read the brochure of the Sanyo system and Sanyo use an inverter to turn 12 volt Dc from the solar panels to 240 volt AC to move the air conditioner. But if the air conditioner had an inverter inside that changes 240 volt in to 12 volts dc to run the compressor, why you can took out the inverter and give direct current from a bank of batteries.
12v won't run the compressor, the compressors run on 380V DC.
All brands are similar, because there's only a few makes and models of compressor, and they run on 380vDC. I donl;t even know if sanyo are in the compressor manufacturing business, if they're not, then they can't build a low voltage system anyway, they have to work with the 380v DC compressors they buy.
Sanyo do it their way because it would cost a lot of money to make a low voltage system even if they did design and make their own compressors, would it be worth it if no one buys it?
Their system means off the shelf units can be sold to people running solar, or people running 100% off mains.

Think about it, any one caring about the enviroment but running air conditioners, is merely paying lip service to the whole 'green' way of thinking. If they really cared about the enviroment, they would live without a/cs as human kind has for thousands of years previously, and design buildings that were 'eco friendly' and didn't need air conditioning because they were shaded and well insulated.

Edit: anyway, converting solar to electricity is still a technology in it's infancy, and is very expensive to do., let alone the cost of buying, maintaining and disposing of batteries For the purposes of air conditioning, very old technology using heat is a better way to go. Look up absorption refrigeration, using cheap solar panels like how water solar heater use, would power a small air conditioning plant.

[Gitano439]

Thanks paul

[ice_cool]

solar power technology for ac still nees quite a lot to be improved.

[erjoni]

Hi. The DC motor of inverter work with 230v dc

[Ration_Tea]

Would someone provide more information on inverter Air Conditioner?

I been read crazy material on solar energy air conditioner or inverter Air Conditioner.

[Ration_Tea]

I meant URL links! Thanks

[dextercath96]

I want to know if you have an inverter Air Conditioner, and the things of been an inverter Air Conditioner is that it take AC electricity and converts to DC, so the motor on the compressor can be adjusted to the desire BTU. Why you don’t have a bank of batteries (solar rechargeable), and connects directly to the air conditioner omitting the AC electricity, and perhaps been more efficient in the process because you’re omitting the conversion of electricity.

Yeah right. I think I can connect my solar power directly to my air conditioner. I think it is efficient. ;)

[picoranton]

Interesting subject!
Am an absolute novice on airconditioning since I never used such a system, but now living (retired) in Malaysia have no other choise than to get familar with this subject.
What by the way is the difference between a compressor for a fridge and an aircon?
picoranton

[Tayters]

A bit of an old thread but with some interesting comments.

An AC inverter compresser will work so:
Convert 240V AC to 340V DC through a rectifier (remember 240V is RMS voltage so peak is 340V (ish))
Put this DC voltage through inverter to give a 3 phase AC, controllable frequency output.
Adjust frequency to suit load.

Therefore you can't use a bank of batteries to power the compresser, but I suppose in theory at least you could use solar panels to provide the inital DC voltage.

What's with this DC inverter business then?

All in the terminology chaps. These are not DC motors as in Direct Current. More like Digitally Commutated or DC Brushless motors. These use a permanent magnet in the rotor and a 3 phase stator connected to the inverter.
The difference is the permanent magnet as opposed to the electromagnet found in an induction motor. Something about better performance over certain frequencies/load with the permanent magnet.

Think about how a DC (back to Direct Current now) motor works. The alternating magnetic field is produced by swapping round current flow in the rotor via the brushes and the stator provides the constant magnetic field from the permanent magnet. All that happens in the brushless DC motor is the alternating magnetic field is swapped to the stator and permanent magnet to the rotor.

It's development went like this:

Q: How are we going to get a rotating magnetic field now if we can't 'mechanically' reverse current flow?
A: Reverse current flow in the stator.
Q: Can we do that with a DC supply?
A: Hey nonny no my friend because a DC current will never swap round.
Q: Well in that case the job's off.
A: Not so fast young shaver. Let's use an AC inverter to swap it round, tweak it a bit and just to confuse
everyone we'll call it a DC Inverter.
Q: You must be as smart as that bloke Andy from Southampton
A: As smart yes, but not as good looking.


Some BLDC motors are supplied with a DC voltage but they have the nessecary switching gear built in the motor casing but this isn't the case with compressers.

Infomation is a bit hard to find on HVACR inverters and DC inverters but here are a couple of links to help explain my point.

http://en.wikipedia.org/wiki/DC_motor
http://www.atmel.com/dyn/resources/prod_documents/doc8138.pdf
http://www.powertecmotors.com/pdf/fmaxa/Manual_PXA_041116.pdf Page 2-11 shows a brushless DC drive block diagram (just incase anyone doubts me!)

Enjoy!!
Andy.

[MikeHolm]

When we design up solar systems for off-grid houses, we never use the PV power for anything that produces heat or has a big current load. The exception to this might be a toaster oven or a microwave and we use a highly insulated DC fridge if possible.

Reasonably sized PV systems for houses (5kw capacity, for example) might provide 15kwh a day on average through the year and it won't take long to draw down batteries when any type of compressor driven cooling system is used so there won't be power left over for other things.

Best to think about solar thermal with adsorption, absorption, or desicant systems when looking at cooling technology.

[wilks]

A bit of an old thread but with some interesting comments.

An AC inverter compresser will work so:
Convert 240V AC to 340V DC through a rectifier (remember 240V is RMS voltage so peak is 340V (ish))
Put this DC voltage through inverter to give a 3 phase AC, controllable frequency output.
Adjust frequency to suit load.

Therefore you can't use a bank of batteries to power the compresser, but I suppose in theory at least you could use solar panels to provide the inital DC voltage.

What's with this DC inverter business then?

All in the terminology chaps. These are not DC motors as in Direct Current. More like Digitally Commutated or DC Brushless motors. These use a permanent magnet in the rotor and a 3 phase stator connected to the inverter.
The difference is the permanent magnet as opposed to the electromagnet found in an induction motor. Something about better performance over certain frequencies/load with the permanent magnet.

Think about how a DC (back to Direct Current now) motor works. The alternating magnetic field is produced by swapping round current flow in the rotor via the brushes and the stator provides the constant magnetic field from the permanent magnet. All that happens in the brushless DC motor is the alternating magnetic field is swapped to the stator and permanent magnet to the rotor.

It's development went like this:

Q: How are we going to get a rotating magnetic field now if we can't 'mechanically' reverse current flow?
A: Reverse current flow in the stator.
Q: Can we do that with a DC supply?
A: Hey nonny no my friend because a DC current will never swap round.
Q: Well in that case the job's off.
A: Not so fast young shaver. Let's use an AC inverter to swap it round, tweak it a bit and just to confuse
everyone we'll call it a DC Inverter.
Q: You must be as smart as that bloke Andy from Southampton
A: As smart yes, but not as good looking.


Some BLDC motors are supplied with a DC voltage but they have the nessecary switching gear built in the motor casing but this isn't the case with compressers.

Infomation is a bit hard to find on HVACR inverters and DC inverters but here are a couple of links to help explain my point.

http://en.wikipedia.org/wiki/DC_motor
http://www.atmel.com/dyn/resources/prod_documents/doc8138.pdf
http://www.powertecmotors.com/pdf/fmaxa/Manual_PXA_041116.pdf Page 2-11 shows a brushless DC drive block diagram (just incase anyone doubts me!)

Enjoy!!
Andy.
quality post

[cool_tech]

Hello Guys,
I have worked on one of the solar/wind and mains power ac units. they were developed after cyclone katrina in the us.The compressor is an variable speed compressor. running r134a. They are only 6 kw cooling approx and run off the green energy before the mains. worked well, hope to see more in Australia.

[MikeHolm]

Cool tech, solar power on the DC side before the inverter varies widely in both voltage and current (although mostly current). With North American voltages, we provide the central inverter with a voltage of 260-500VDC (depending on the installation design) and the power is changed to a steady 240VAC.

The option is also there to use a microinverter on each panel so that there is 240VAC coming from the roof. In this way you can add panels as the budget allows. It is still a choice of power sources for the AC unit. I suspect that all it sees is steady state power coming in and doesn't care how green the source is. I think there is some "greenwashing" going on. I see it all the time.

[kayakalp]

Cool Tech ...