Fridge Size

[Redbearded]

Just a note about the sawafuji compressors: by the nature that they are using a tuned resonance, lots of the power going into the system is being used for the compression of the gas, and some for friction losses.

[font=Verdana, Arial, sans-serif]A reciprocating motor (piston compressor) will always take more energy than a rotating motor (rotary compressor).  It takes more energy to accelerate the piston on each stroke than it does to keep a armature rotating.  This is also why a rotating compressor has a startup surge (it has to accelerate the armature to operating speed) and the piston compressor doesn't (it actually has a startup surge each stroke of the piston).[/font]

[font=Verdana, Arial, sans-serif]The piston traveling up and down is by design balanced by the springs on either side so all that needs be done is maintain the system in its natural frequency, which is how they are able to get such efficiencies out of the linear compressors.[/font]

[font=Verdana, Arial, sans-serif]It is fascinating to see what design choices were made and try to deduce the reasons![/font]

[font=Verdana, Arial, sans-serif]Plus it is good to have other knowledgeable people to figure it out with![/font]

 

[Trebor English]

All of this refrigeration via solar power is a bit like a pendulum swinging one way or the other:

On the one hand, you can build a more powerful solar array and then use a less efficient refrigerator,

Or,

You can conserve on a solar array and then spend the money you saved on a more efficient, and more expensive, refrigerator.

Either way, to keep a good quantity of food cold in the summer heat, it will ding your credit card pretty hard.

See my thread about my efficient refrigerator diy.  The 100 watt solar is not powerful.  The refrigerator was bought for $80.  The key is insulation.  

The compressor uses energy to compress the refrigerant gas.  That's where the work goes.  Pistons are all about the same.  The differences are minor compared to the work required to compress the gas.  A larger surface area condenser reduces the pressure differential.  That helps.  Better insulation and seals cause less heat pumping to be required.  That helps.

Bending a spring causes friction, a crankshaft with spinning bearings causes friction.  Pick one.  A 3 phase inverter will use more power than a single phase inverter.  A three phase motor will be more efficient than a single phase motor with a run capacitor.  Pick one.  A fan blowing on a condenser uses power but lowering the head pressure saves power.  Pick one.  Reducing compressor speed lowers the power requirement but has a longer run time.  Pick one.  It comes down to 1 percent more here and 2 percent less there.  There is no single bit of magic.  To refrigerate requires pumping heat from a cold place to a hot space.

 

[Weight]

I am happy with my Indel-B cooler. Set at 36 F. My bank is never under 94%. 300 w solar makes my breakfast and dinner and keeps the beer cold.

 

[Redbearded]

Well said Trebor!

I know there is only so much efficiency out there, I just don't want to try running a freezer with an inefficient compressor, a poorly sized evaporator, and too little insulation in the desert at 110F, lol. I figure if I do homework and know that I value capacity, efficiency, and cost more than using a specialty build expensive (limited market share) fridge that is too small for what I think I would like then I need to come up with a solution that works for my situation.

I think I have found that solution in the form of a freezer (I have almost no need for a tiny fridge as space should not be a big issue) running as a fridge with a custom controller. I do wonder if I couldn't eek another 5-8% efficency out of it by changing compressors and other tricks. The problem with going too custom is the cost. 

I think I can put together a system for under $300 (freezer, inverter, and controller) that will come close to what the expensive fridges are and get a ton of storage to boot! and as I said worst case if I waste a bit of money on selling the freezer for a loss and throw away the controller. I'm willing to take the risk

When I get started on this I'll let you know what I figure out, and if it was a good choice of not! If nothing else it will be fun to use my brains to solve a problem and not my wallet

 

[Almost There]

I just don't want to try running a freezer with an inefficient compressor, a poorly sized evaporator, and too little insulation in the desert at 110F, lol.

Us nomads move long before it gets to a 110F.

I move when the average daily temperature starts getting about 85F, like in March. Some like to move sooner and some later. We migrate with the seasons to the best of our ability.

Even if one never leaves Arizona, the choice to move to a higher altitude and cooler weather exists, all within about a 250 mile driving distance. The only reason to do more miles than that is *because we can* or in my case, cause I'm Canadian and have to come do my 6 months residency thing!

 

[Redbearded]

What you say it true! I guess there is a part of me that keeps forgetting I can just move... I keep thinking I have to endure and prepare for whatever nature throws at me. I must say I am really looking forward to this new way of thinking!

 

[lf6998]

Hello
I would like to have a 3 way fridge/freezer, small 3-4 cu feet, also run most as AC power not DC.

Maine comsuption is the fridge, charge pc, phone, led light strip.  I have solar lights and flashlights.

Was thinking 400 watt solar would be enough, but with a small freezer (needed for ice packs for medical reason) more than food.


Prefer one that runs on 120 house plug/LP instead of 12v DC due to price and sizes available.

Would 400 watt be enough?  Will need room on van top for 1-2 fantastic vent fans, I know I can get higher watt panels over 400 so less panels 
needed.

Another alternative is an ice machine however I tried one previously and did not work, I returned, used in my camper when on a permanent site. Not sure how much power it would use as well.  

I have tried to convert appliances vs use and power needed and not sure I did it correctly. 

Input and suggestions would be great.

 

[highdesertranger]

a refrigerator that runs off propane/120AC is an absorption refrigerator. they are very inefficient when run on electricity. if you plug into the grid you will not notice because electricity is cheap. if you try to run it off solar you will need a huge battery bank and a lot of solar panels. highdesertranger