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Aircon or fridge compressor to solar? Answered

Sometimes I get weird ideas that I can't shake off :)
When I was looking into options for a 12 compressor fridge freezer combo I was stunned.
You a get a fullsized frrezer for far less!
A further check revealed that it is mainly the linear compressor that makes the price plus the usual mark ups.
Efficiency and especially start up is far better with thes compressors than out standard rotary and piston drive models.
But why would it be so impossible to replace the motor from a standard compressor with a brushless DC one?

I focussed on three things for the start:
Lubrication, cooling and sealing.
There is no such thing like a simple compressor with a piston system that does have some leaking.
So apart from the noise the enclosure really needs to be welded and sealed again.
Everything moving inside is lubricated by the drive shaft - it acts like a little pump.
Same for the cooling of these vital parts.
The oil flow exchanges heat through the big metal housing.

A replacement motor would need to be suited to run in such a messy enviroment.
Of course something to provide a proper oil flow needs to be created too if the drive shaft is replaced.
With some basic enineering this might be possible, same for the motor mount and wiring to the outside.
But what to do about the full load starting conditions that can happen?
Even with no load from the cooling system the motor needs massive torque to get the piston moving.
A bypass valve that closes once the motor is at proper speeds might work but hard to implement in a tight space.

Any ideas?
Did you ever try something that stupid?
Could you make it work?

What about a rotary compressor with external drive?
We use ice blenders that have a magnetic base and the actual connection is made through the magnetic forces alone.
A scroll compressor has lots of space without the original motor inside.
Plus, a round pipe is easier to work with when it comes to adding or removing things.
Small scroll compressors from an airconditioner or small industrial freezer wouldn't have to do much work in a small setup.
Best thing is that with a variable speed the cooling power can be adjusted.
How feasable would it be to use some polycarbonate end plate and a magnetically coupled drive ?
Modern BLDC motors offer great performance and suitable gear systems are readily available.
N52 neodymium magnets of the block type provide several kg of force if close enough to each other - should be enough to make a compressor spin...

In return it could mean to have a nice freezer or even airconditioner that runs directly on solar power.
No massive losses from inverters, no need for huge battery banks either.
As long as the sun is out you have free power, once down you can still switch to a power supply for the motor or use battery power.
Just imagine you come home after long day of work and the house is already cool.
And you did not have to pay a cent to get it cool or wait for hours for it to reach this temperature!
We love to add solar panels to our houses in the hope to get a few cents back from our energy providers.
The sad reality often is that you might be able to power all your needs during the day but the excess that goes back to the grid often pays next to nothing.
But if you could power a lot more things like a compressor directly with the electricity from your panels....
Then these kWh would not appear on your usage bill either.
Means you neither use what the power provider compensates you for nor is it "wasted" thorugh this bogus compensation.
The normal solar setup can then provide you with this little extra money while an additional set powers the motors for your big freezer or little airconditioner - little being relative to what you make of the idea ;)
If you really dare than you could even use your bike and legs to power your fridge directly ;)

Use your imagination :)

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