Solar Powered Air Con- possible?

[FunGas]

I built a PV/Peltier based cooler for the workshop.

If you're going to cool more than 50m³, forget it, use a generator.

My workshop is about 30m³, with a 150W panel, it cools about 10-15 degrees - not much when the ambient is over 40 degrees.

[dkpro1]

RV Gen.

yes, they do need a bit of work to quiet them down. Personally I'd rather hear the thump thump of a Listeroid than a quiet modern high rev engine. Listeroids aren't so portable tho

THEY MAKE ME WANT TO PUKE CANT STAND THEM......

[ChrisOlson]

Not intentionally it was painting all generators with a broad stroke which has now been done by the OP. In off grid application THD is pretty much meaningless because the generator feeds a battery charger which in most designs is very tolerant of THD.

That would only be the case with a generator just driving a charger. In systems (more typical) where the power passes thru to loads and the inverter can either charge batteries with excess or switch to invert mode to assist the generator with loads (Generator Support Mode), THD becomes a very real issue in keeping the generator qualified on the inverter. And sometimes in getting it to qualify at all.

We always figured that if we could get 5% THD at rated prime from a genset, that's about as good as it gets. But the point is that "thumpers" that deliver uneven torque do not make good prime movers for AC gensets. They're fine on DC.
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Chris

[Sunking]

I believe the Utility is only supposed to meet the IEEE Std 519-1992 of < 5% THD.

Winner Winner Chicken Dinner. Just about every residential whole house and commercial genny does that. Heck even some Gas portables like Honda "iAVR" system beets that. It comes down to design and matching components up that work with each other.

[SunEagle]

Yeah but so what? The generator is not causing the distortion which is meaningless, it is the load equipment causing it. Care to guess what the utility supplies?

I believe the Utility is only supposed to meet the IEEE Std 519-1992 of < 5% THD. And you are correct that most distortion is generated by PWM power supplies on the loads.

[Sunking]

You conveniently chose to leave "with a Lister 6/1 as the prime mover." out of your quote.

Not intentionally it was painting all generators with a broad stroke which has now been done by the OP. In off grid application THD is pretty much meaningless because the generator feeds a battery charger which in most designs is very tolerant of THD. None of that gets past the batteries. Fact is most medium quality generators and up are in the 5% range which is better than the utility can give you. That makes it a moot point.

[Sunking]

A random sample of three Cummins prime mover stationary diesel generators in the over 10kW range found the best one offering < 1.8 % THD with NO LOAD and up to 5% THD at full balanced linear (non motor) load.

Yeah but so what? The generator is not causing the distortion which is meaningless, it is the load equipment causing it. Care to guess what the utility supplies?

[ChrisOlson]

But when dealing with a generator head, not allowing the option of an inverter generator, I think that 0% (even generously interpreted as less than .5%) would not be very easy to reach.

It's actually almost impossible to achieve less than 5% with conventional wound field generators. I mostly worked on megawatt-class diesels at Cummins and I've never seen even one of those that was much better than 5%. Typical portable generator range for cheap box store generators will be 10-15%. The ones with electronic throttle regulation and CT sensing on the output will achieve 5%, but they are pretty expensive sets.

Inverters are usually 2% or less.

With a Lister 6/1 driving a gen head with a belt you're lucky to keep the freq +/-2Hz from nominal with no load on it. Put a load on it and it gets worse as the crank "snaps" back into shape after every power stroke, transmitting the torsional vibration to the flywheels and belt drive.
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Chris

[inetdog]

That is no where close to an accurate statement. While that may be true from a generator you buy at Northern Frieght, but even low end Honda, Briggs and Stratton, Generac are 2% or less. Move up a little and you get 0% THD.

You conveniently chose to leave "with a Lister 6/1 as the prime mover." out of your quote.
The straw man you conducted by doing that was easy to knock down.
But when dealing with a generator head, not allowing the option of an inverter generator, I think that 0% (even generously interpreted as less than .5%) would not be very easy to reach.

PS: Among portable generators (admittedly not going to produce the best possible power quality) Low THD is generally considered to be below 5%.

A random sample of three Cummins prime mover stationary diesel generators in the over 10kW range found the best one offering < 1.8 % THD with NO LOAD and up to 5% THD at full balanced linear (non motor) load.

PPS: One of the specifications even introduced the truly amazing concept of Total Harmonic Distortion at a single frequency, which got below 3% even when the Total Harmonic Distortion for all harmonics was greater than 5%.

[ChrisOlson]

That is no where close to an accurate statement. While that may be true from a generator you buy at Northern Frieght, but even low end Honda, Briggs and Stratton, Generac are 2% or less. Move up a little and you get 0% THD.

Not when being driven by a 6/1 Lister. The flywheels speed up and slow down with every power stroke due to severe torsional vibration in the crank. The uneven power delivery to the gen head causes really bad THD. Most Listers use belt driven gen heads because they run at 900 rpm and either a 4 pole or 2 pole generator will be used at the correct drive ratio. Ever seen the belt on a Lister driving a gen head? The belt amplifies the problem.

You have to run a gen head at constant speed with smooth input to get good clean power out of it. I've seen some Lister setups that are so bad that the inverter won't qualify it because it can't track it to sync with it.
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Chris

[Sunking]

Never seen a gen head yet that can put out power cleaner than about 15-20% THD

That is no where close to an accurate statement. While that may be true from a generator you buy at Northern Frieght, but even low end Honda, Briggs and Stratton, Generac are 2% or less. Move up a little and you get 0% THD.

[ChrisOlson]

Could this unit work? and if so how many panels/batteries would I need to power the unit overnight (say 10 hours).
I would think it would need quite a large syatem.

Kind of an old thread. But we installed central A/C for our home this year for the 4 weeks or so in summer when it gets humid and stays over 90F. The solar runs it fine when the sun is up. At night there's no way you can run A/C off battery power very economically. We use diesel power to run A/C at night. We have just a small 1.5 ton Trane unit.

Someone mentioned using a Lister or Listeroid clone. Don't even think about it for AC compressors. A Lister makes a big bang, then sits there and huffs and puffs and sucks and blows for two crankshaft revolutions before it hits the crank pin with another big bang. The torsional vibration on the crank is severe, despite the flywheels. 3,600 rpm engines don't have that problem.

Never seen a gen head yet that can put out power cleaner than about 15-20% THD with a Lister 6/1 as the prime mover. A/C compressors do not like power that "dirty" and it will run hot and lose a lot of electrical efficiency because of it - and that's assuming a Lister 6/1 can even deliver the surge power to start an A/C compressor, which they can't. A/C compressors typically draw 2.5-3x their running amps for starting and 5x running amps at locked rotor.

If you are off-grid and need to run A/C then buy a good diesel generator. If you have grid power don't even think about trying to run A/C with solar power
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Chris

[Sunking]

If you have some grid power, could you not use this to charge a battery bank when available?

Would save on some of the cost of solar panels and controller, at least.

That is what smart money would do. Green Wash money no way Jose.

[geebus]

If you have some grid power, could you not use this to charge a battery bank when available?

Would save on some of the cost of solar panels and controller, at least.

[SunEagle]

yes, they do need a bit of work to quiet them down. Personally I'd rather hear the thump thump of a Listeroid than a quiet modern high rev engine. Listeroids aren't so portable tho

I haven't seen a Listeroid Diesel generator in a real long time. They do have a distinctive sound which is less annoying than a new gas generator.

Of course you can go use one of them Honda's which have a dB rating in the mid 50's which is pretty quite.