Solar PV powered reverse cycle AC

jimbo78

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I see solar PC powered AC units becoming more and more available.

Engineer775 talks about them in the US...

Seems they are now available here in Australia also...

This is a game changer, as it doesn't require storage, and uses the storage you already have, namely your houses insulation qualities.

During the summer it would provide the bulk of your cooling needs, while also providing some heat other times.

For off-grid scenarios you also eliminate some inverter losses (going DC-AC-DC), gaining all the efficienceis reverse cycele AC units bring, while also reducing your storage needs.

For an off-grid cabin this thing is a total game changer!

It looks like a win win win situation to me.

Has anyone played with one of these units?
 

gnubie

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I run a standard 230V Fujitsu reverse split entirely off solar. Overnight it runs from battery, if I actually run it during the day (so far that hasn't happened) it could easily run off excess solar production. It got down to 8c here a couple of nights ago, kept the bedroom nice and warm at about 320 watts, fibro house without insulation in the walls, so leaks heat like a sieve.
 
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gnubie

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If you are living with in a feed-in arrangement and have the roof space to spare, fair enough. I can't really think of a situation where you'd want to put up another 1000 watts of panels to have the aircon sip at that tossing away half the capacity (typically) when you could reasonably tack that same 1000 watts into an existing PV system, run any efficient split system you like and have the power left over either going into the battery or towards running other loads.

If you really really must run a DC aircon you still could but run it off your main DC buss, that way you'd gain the unused output of the 1000 watts of panels by having them tacked into your existing PV system.
 

jimbo78

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off your main DC buss

These things require between 100-300V so its not that easy. And using a DC-DC converter introduces similar losses to an inverter (maybe a little less) and are also expensive.

But yes I'm kinda torn, on one hand you can reduce the amount of charge controllers needed in your system, but the system is less flexible. On the other hand panels are cheep. So yeah, but if your totally off gid in a cabin, one of these things would be fantastic, nothing more required other than a wood stove for when the sun goes down!! But you will require way less wood, and you have a cooler cabin in the summer!

If I was installing an AC today, I would spend the little extra $ to have the DC option even if i decide not to use it. Having that flexibility in my mind is a no brainier. But I'm not going to rip out my current unit just for this.

Surly we will see DC heat pump hot water systems (if the don't already exist) soon, and that would also be very interesting!!

Then perhaps DC heat pump pool/spa heaters as well?! The advantages eventually will mount up! Use your pool for storage also?

And maybe you could run all these systems off the same PV array giving greater flexibility. If you know its going to be a cloudy day then turn off the pool heater and dump the extra power into the hot water unit etc.

And now, they really do look interesting don't they!
 
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gnubie

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Ah, I assumed it was the type of design that would run down to 48v. There are units out there that are classed as solar based and will run direct off panels but are equally adept at just being run off fixed DC.
 

jimbo78

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Heat Pump cloths dryers are also a thing now, so perhaps thats another application for DC in this way!!

You could have direct PV 100-300VDC running around your house and an AC-DC (or DC-DC) converter to supply power when the sun is down.

Holy crap, maybe Edison will have the last laugh after all!
 
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gnubie

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Not sure I like the idea of HVDC floating around the house. The propensity for sustained arcing with DC and the current limited nature of PV (ie things will tend to continue to arc rather than blow clear like they would with a high current supply) makes me nervous.
 
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