The Stirling Engine Air Conditioner/Refrigerator Question

[ZippoLag]

Hi everyone!

What I wish to know is simply: "COULD a solar powered stirling engine be used to power another stirling that'd act as a heat pump for cooling a refrigerator or even as an air conditioning unit?".

Simple yes or no answer could suffice, but let's expand that with further considerations:

• What would be the power input requirements of a stirling heat pump to cool a "standar size" fridge?
• And for a small room?
• Even a few degrees drop at least?
• Are such power outputs achievable using a solar powered stirling? How about using several? Just about how many really?
• Are you considering home made (poor efficiency) engines or high quality engines with machined parts and pressurized Helium?
• How would such a setup fare against the efficency of usin solar panels to run a conventional electrically powered AC unit or regrigerator?
• How would they compete in economical terms? Would it be at least as good as to make a -small- portable solar powered stirling refrigerator plausible?

And some final clarifications:

• Yes, I'm a complete noob regarding Stirling engines, besides reading several posts and watching plenty of videos
• No, English is not my first language, so apologies if I have commited some horrible mistake in my writing
• Yes, I have been vague in my definitions and have not done any math to tackle the problem, I care more for your views on the matter
• I've seriously seen several variations of this idea posted around the web (some even on this forum) but the answer is never quite clear, so please, if you feel you could shed some light on this matter, please share your thoughts!
• Yes, I do know there used to exist a commercial brand of portable small refridgerator that used batteries to power a stirling heat pump for cooling, but the route I want us to examine is Sun->StirlingEngine->StirlingHeatPump->ClosedSpaceTemperatureDrop.

[fullofhotair]

Where do you live ? What are daytime high temp. and night time lows, during summer? What is the humidity for these times?

[ZippoLag]

Where do you live ? What are daytime high temp. and night time lows, during summer? What is the humidity for these times?

I live at latitudes 32.92S, 60.67W. Temperatures in the summer often vary between 25 and 35 degrees Celcius and humidty is rarely below 80%. But I'm not asking for my particular case, rather let's assume optimal conditions (living along the Equator) and derive from there!

[fullofhotair]

Zipolag,
The reason I ask specifics is it make a big difference in the type of cooling system you use,but you just have a general interest.From what Ive read, here and other places, is a stirling engine is capable of doing what you ask of it. Bad news is its going to be super expensive.A one of kind.If your still interested I can give you web sights where they are using reverse stirling engines as cyrogenic coolers etc.

[ZippoLag]

Zipolag,
The reason I ask specifics is it make a big difference in the type of cooling system you use,but you just have a general interest.From what Ive read, here and other places, is a stirling engine is capable of doing what you ask of it. Bad news is its going to be super expensive.A one of kind.If your still interested I can give you web sights where they are using reverse stirling engines as cyrogenic coolers etc.

By all means! Share whatever information you have!

The reason this intrigues me so much is because from my point of view the system should be quite possible. Except for one Achiles Tendon I see: the lack of efficiency. If one of this engines uses a -big- temperature -differential- caused from concentrated sunlight and converts it (with some loss) to mechanical energy and that mechanical energy is used to power a heat pump (wich itself is as innefficient as the first engine), the temperature drop caused by the pump would be the least efficient part of the system of course, but just how innefficient is that?

Of course, I haven't read enough, nor experimented at all, so I'm just blind guessing here. That's why I came to this forums: I thought "hey, this place is called THE stirling engine forum, people'll surely have an answer to this there!".

[fullofhotair]

Zippolog,
The first two videos are from the Phillips corp circa 1960’s by the look of the footage.
The last video is a home built unit that is barely able to keep an ice chest cool.
http://youtu.be/GqIapDKtvzc
http://youtu.be/GFfMruoRMGo
http://youtu.be/5ImmaKORSII

[ZippoLag]

Zippolog,
The first two videos are from the Phillips corp circa 1960’s by the look of the footage.
The last video is a home built unit that is barely able to keep an ice chest cool.
http://youtu.be/GqIapDKtvzc
http://youtu.be/GFfMruoRMGo
http://youtu.be/5ImmaKORSII

Thanks! I already knew the cooling box video, wich is pretty neat to me, it doesn't say what the wattage of the electric motor is, but keeping a small cooler at 2ºC with such a simple device is just amazing to me.

And those Phillips videos were great! They made me realize a few things I had thought wrong, including how mechanically complicated this things can turn out to be! Even still, I think my original question for wich I created this thread still stands unanswered, or perhaps it just makes me think it's even more plausible now!

[Bumpkin]

I love Stirlings for the fuel flexibility, but they're far from efficient. Of course a solar Stirling could directly power a heat pump, but a better solution might be a simple absorption refrigerator modified to heat from solar. Not that I've personally seen that done, but I think it would be more practical than any Stirling contraption.
Air conditioning - if the humidity allows, use evaporation. Or use thermal mass like I do with the entire back side of my house dug into a hill.
I've lived off-grid for over thirty years, but it's hard to beat electricity. If you're currently using any power at all it makes more sense to me to consolidate, assuming a secure level of redundancy. Efficient appliances and habits can save a lot. My own dream is to have enough home-made power to get away from propane appliances and the mess of a back-up gas generator. I already do a bit of welding with sunlight, (photovoltaic-battery-inverter) but it takes a lot of patience and advance planning in the winter. A few hundred watts from a woodstove would make a big difference. I guess we're all here for different reasons, but too many seem to be misled by bogus theoretical efficiency claims.
Just my own thoughts - for my own situation. Bumpkin

[allanmullaly]

Yes, your home heating system might interrupt the home cooling system. Check it out first..

[dreameez]

Clean all the dust off, get a knob for it, and it wouldn't look half bad

[fullofhotair]

I agree the best way to use solar to cool is absorption chiller using amonia ,water and hydrogen. In those magazine articles by Vamoose ,at the top of the page is one on using a free piston stirling engine and a vapor compressor fixed to the top of it .Pretty neat setup.

[ZacharyYoung]

Hi everyone!

What I wish to know is simply: "COULD a solar powered stirling engine be used to power another stirling that'd act as a heat pump for cooling a refrigerator or even as an air conditioning unit?".

Simple yes or no answer could suffice, but let's expand that with further considerations:

• What would be the power input requirements of a stirling heat pump to cool a "standar size" fridge?
• And for a small room?
• Even a few degrees drop at least?
• Are such power outputs achievable using a solar powered stirling? How about using several? Just about how many really?
• Are you considering home made (poor efficiency) engines or high quality engines with machined parts and pressurized Helium?
• How would such a setup fare against the efficency of usin solar panels to run a conventional electrically powered AC unit or regrigerator?
• How would they compete in economical terms? Would it be at least as good as to make a -small- portable solar powered stirling refrigerator plausible?

And some final clarifications:

• Yes, I'm a complete noob regarding Stirling engines, besides reading several posts and watching plenty of videos
• No, English is not my first language, so apologies if I have commited some horrible mistake in my writing
• Yes, I have been vague in my definitions and have not done any math to tackle the problem, I care more for your views on the matter
• I've seriously seen several variations of this idea posted around the web (some even on this forum) but the answer is never quite clear, so please, if you feel you could shed some light on this matter, please share your thoughts!
• Yes, I do know there used to exist a commercial brand of portable small refridgerator that used batteries to power a stirling heat pump for cooling, but the route I want us to examine is Sun->StirlingEngine->StirlingHeatPump->ClosedSpaceTemperatureDrop.

[/u]

Awesome post.. Even I am trying to have similar set up of stirling engines and solar panels and most of my queries are resolved.

[Ian S C]

Yes it could be done, but not efficiently, a standard domestic refrigerator has a motor of about 1/6th HP, or 125Watts 230Volts just to give some indication of the power required, but even the most efficient Sterling Engine would only have about half the efficiency of an electric motor. Stirling Engines only really come into their own when used at very low temperatures, as Cryocoolers, these are used for freezing, or liquifing gasses. I have driven one of my engines, with another one, and got the end of the hot cap down to minus 20*C, the ambient temperature at the time was plus 20*C, time taken 20 miniutes. Ian S C

[StevenRoy]

Hi everyone!

What I wish to know is simply: "COULD a solar panel powered stirling engine be used to power another stirling that'd act as a heat pump for cooling a refrigerator or even as an air conditioning unit?".

Simple yes or no answer could suffice, but let's expand that with further considerations:

• What would be the power input requirements of a stirling heat pump to cool a "standar size" fridge?
• And for a small room?
• Even a few degrees drop at least?
• Are such power outputs achievable using a solar powered stirling? How about using several? Just about how many really?
• Are you considering home made (poor efficiency) engines or high quality engines with machined parts and pressurized Helium?
• How would such a setup fare against the efficency of usin solar panels to run a conventional electrically powered AC unit or regrigerator?
• How would they compete in economical terms? Would it be at least as good as to make a -small- portable solar powered stirling refrigerator plausible?

And some final clarifications:

• Yes, I'm a complete noob regarding Stirling engines, besides reading several posts and watching plenty of videos
• No, English is not my first language, so apologies if I have commited some horrible mistake in my writing
• Yes, I have been vague in my definitions and have not done any math to tackle the problem, I care more for your views on the matter
• I've seriously seen several variations of this idea posted around the web (some even on this forum) but the answer is never quite clear, so please, if you feel you could shed some light on this matter, please share your thoughts!
[/u]
• Yes, I do know there used to exist a commercial brand of portable small refridgerator that used batteries to power a stirling heat pump for cooling, but the route I want us to examine is Sun->StirlingEngine->StirlingHeatPump->ClosedSpaceTemperatureDrop.

In my region solar power is not much effective.. We don't have plenty of sunshine available but in favorable conditions the engine is really a nice option.

[Ian S C]

I think it could be done, but working on the power required for a domestic refrigerator, an engine might need to be around 500Watts to give adequate power to drive the cryocooler motor, specially if your sunshine is not too reliable. If in that case there was extra power, a generator could be run as well at peak power times(middle of the day, when the sun is at it's brightest), to charge some batteries to cover cloudy days with an electric motor.
Sorry I can't help with the solar collector/reflector, but I think there is something on google about this, ie., area etc. Ian S C