Running an AC evaporative air conditioner on solar without batteries

[M7amad]

Thanks alot guys for ur responses...much appreciated

[AzRoute66]

If you end up doing this, or even experimenting a little, please update us. I would be very interested.

[AzRoute66]

Just FYI, I measured my existing AC cooler yesterday. With 1/2 horsepower motor I got 400W for fan on high, 200W for fan on low, and 70W for my single pump. The pump surprised me, they state 0.9A on the label, measured 1.0A with a PF of 0.56.

[msra20]

I am glad you pointed out that the hottest part of a day is in the late afternoon which is usually after the pv panels are no longer producing anything close to nameplate wattage.

Somehow we need to convince people that powering their AC loads directly from the panels is a complete waste of time and money. Batteries as you know are not the nicest thing to have but are the critical component as the buffer between pv panels and AC loads.

Nowadays we use solar to power AC 3-Phase pumps directly from panels without battery using VFD solar pump inverters, is it not then also possible to run 3-Phase compressors (like the ones in airconditioners) in a similar fashion? This would of course only run when there is enough sun out and only during the day.

[bcroe]

There are mini split heat pump units capable of running directly from adequate solar panels and sun. Do
not expect much under clouds. They use DC input inverter technology to run the compressor, can also
run off the line. Bruce Roe

[SunEagle]

Nowadays we use solar to power AC 3-Phase pumps directly from panels without battery using VFD solar pump inverters, is it not then also possible to run 3-Phase compressors (like the ones in airconditioners) in a similar fashion? This would of course only run when there is enough sun out and only during the day.

Running any DC load directly from solar panels would require that "load" to be able to run at different speeds and not create an issue. That works for pumps and fans but compressors have to be built to run with variable input voltages.

As bcroe mentions above some mini split HVAC equipment are design to run directly from solar panels but you have to make sure that the "load" and solar panels are compatible.

[jflorey2]

As bcroe mentions above some mini split HVAC equipment are design to run directly from solar panels but you have to make sure that the "load" and solar panels are compatible.

I spoke to one such manufacturer at SPI this year. (Chinese company, has sold ~100K of these things in China.) They use an MPPT controller that accepts between 50 and 150 volts, and the system throttles the compressor power back to match the power output of the panels. In other words, it gives you as much cooling as it can. Also has a 220V backup, and you can set the max power you want drawn from the AC line.

[SunEagle]

I spoke to one such manufacturer at SPI this year. (Chinese company, has sold ~100K of these things in China.) They use an MPPT controller that accepts between 50 and 150 volts, and the system throttles the compressor power back to match the power output of the panels. In other words, it gives you as much cooling as it can. Also has a 220V backup, and you can set the max power you want drawn from the AC line.

I wonder if that product will work in the US.

Remember our frequency is 60hz and most 3 phase power services is 208Y/120V. There are still 240/120V 3 phase services but it will depend on the POCO and customer usage.

Electrical service outside the US can be 50hz 220V single phase or 400V 3 phase. Again it depends on the Country and POCO.

[bcroe]

I have no details, but some direct panel operated Mini Splits like 3 series panels. Sounds something like
100VDC. One model also had an optional 120VAC input. That in theory could connect to a rectifier of
similar voltage, wonder if it means the the panels would be connected to line voltage? The rectifier DC
output supplies the variable frequency drive to the compressor.

Going to 240VAC is really stretching the same voltage range idea, at some point voltage conversion will
be needed. I doubt the line frequency or even 3 phase are of much importance to a rectifier, they actually
reduce DC ripple compared to 50HZ.

First question in my mind, are there directly panel powered AC units with a 240VAC input option?

Given the 3 panel supply, I would be inclined to use 2 or 3 strings of 3 paralleled to keep capacity up
under the varying clouds here. The peak voltage would be the same, it would run a little higher MPPT.

Bruce Roe

[jflorey2]

I wonder if that product will work in the US.

It probably would, on a 240V circuit. (Inverter based compressors that can run on DC have internal inverters; they don't rely on powerline frequency to drive induction motors.)

However I was more interested in the product as an example of a demand being met. If there is a demonstrated demand and a working technological solution, it's almost certain that other manufacturers/other markets will follow. In most places in the US this wouldn't make much sense since it will always be cheaper to go with a net metered solar installation. But as markets that don't allow net metering grow (i.e. other foreign markets, Hawaii) I think we will see more of these sorts of devices.

[bcroe]

However I was more interested in the product as an example of a demand being met. If there is a demonstrated demand and a working technological solution, it's almost certain that other manufacturers/other markets will follow. In most places in the US this wouldn't make much sense since it will always be cheaper to go with a net metered solar installation. But as markets that don't allow net metering grow (i.e. other foreign markets, Hawaii) I think we will see more of these sorts of devices.

Hawaii ought to be a prime market, with both the power conditions, and year around sun. I see
it in my extremely distant future as an (very poor) option to net metering. But then they might
have some basis for accusing me of being a prepper. Bruce Roe

[SunEagle]

It probably would, on a 240V circuit. (Inverter based compressors that can run on DC have internal inverters; they don't rely on powerline frequency to drive induction motors.)

However I was more interested in the product as an example of a demand being met. If there is a demonstrated demand and a working technological solution, it's almost certain that other manufacturers/other markets will follow. In most places in the US this wouldn't make much sense since it will always be cheaper to go with a net metered solar installation. But as markets that don't allow net metering grow (i.e. other foreign markets, Hawaii) I think we will see more of these sorts of devices.

I agree. "Build it and they will come".

I just hope that the technology is not made of low quality hardware or has a short life span.

But as bcroe stated, HI might be a good starting place to increase the market for DC powered HVAC equipment. Time will tell.

[msra20]

I spoke to one such manufacturer at SPI this year. (Chinese company, has sold ~100K of these things in China.) They use an MPPT controller that accepts between 50 and 150 volts, and the system throttles the compressor power back to match the power output of the panels. In other words, it gives you as much cooling as it can. Also has a 220V backup, and you can set the max power you want drawn from the AC line.

This sounds like exactly the thing I am going for with my hack , what was the manufacturer?

[jflorey2]

This sounds like exactly the thing I am going for with my hack , what was the manufacturer?

I didn't take a picture of that one (I did for most of the other booths I stopped at) but I _think_ the manufacturer was YMGI.

[Jnj6370]

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