Heat Into Cold Via A Stirling Engine, And Could Just Save The Planet?

[s8548a]

I just read an article that a dutch startup converts heat into cold via a stirling engine.

https://www.forbes.com/sites/johnkoetsier/2019/01/18/this-dutch-startup-converts-heat-into-cold-via-a-stirling-engine-and-could-just-save-the-planet/

"The system itself does not consume electricity/energy,"

sounds cool?

[T3sl4co1l]

Nothing unusual, a heat source and sink is all you need to make something else hotter or cooler, at some efficiency less than Carnot or other theoretical limit (depending on the exact cycle used).
https://en.wikipedia.org/wiki/Absorption_refrigerator
Doing it acoustically (which, I guess from something that size, must be an awful low hum?) is a newer thing, and it's not obvious how that helps (or hurts).

Mind, the efficiency figure really means nothing, and was probably measured at zero temp drop or something like that.

Tim

[Zero999]

Yes, it's fairly easy to convert heat to cold. In away that's what's happening with standard air-conditioning powered by electricity generated by burning coal, except the heat is converted to electricity first, to drive a heat pump.

Thermodynamics limit the ultimate maximum efficiency of the system.The higher the temperature differential on the hot to ambient side and the lower the temperature differential on the cold to ambient side, the more efficient in terms of Watts of heat in, compared to Watts of cooling, it can be. For example, if the ambient temperature is 30°C and your heat source is 300°C, you'll get more cooling power, per Watt than a 100°C heat source and if you only need to cool to 20°C it will be more efficient, than cooling to -20°C.

The question is whether it's any more efficient compared to existing technologies such as absorption cooling?

[raptor1956]

It is rather un-intuitive that you can make things cold with heat but that is the way it is.  Anyone that has an RV knows about this as the refrigerators in RV's are mostly dual power units that either run on AC power like your home model or from propane.  In fact, Albert Einstein and Leo Sziliard designed just such a refrigerator.

https://en.wikipedia.org/wiki/Einstein_refrigerator


Brian

[soldar]

The question is whether it's any more efficient compared to existing technologies such as absorption cooling?

More economically efficient.

The way the article is written it raises many doubts in me. Stirling engines, Tesla and a few other "rediscovered" technologies raise my suspicions.

[Red Squirrel]

I remember seeing this cool project where they built dishes of mirrors that concentrate the sun to a Stirling engine.   These were maybe about twice as big as the old style TV dishes people use to have on their homes.   I wonder why we don't see those at all.  Is PV actually more efficient for the same surface area?  I would expect these dishes to be more efficient. I guess they do require more maintenance due to moving parts.

[raptor1956]

I remember seeing this cool project where they built dishes of mirrors that concentrate the sun to a Stirling engine.   These were maybe about twice as big as the old style TV dishes people use to have on their homes.   I wonder why we don't see those at all.  Is PV actually more efficient for the same surface area?  I would expect these dishes to be more efficient. I guess they do require more maintenance due to moving parts.

The Stirling solar is about 32% efficient as I recall and PV using low cost cells is about 15% so the Stirling would seem to be hugely superior except the cost for a Stirling solar system is way more per KWHr than PV.  The Stirling solar suffers two main problems: first, the cost to deploy; and second its almost useless when there's any clouds whereas PV works fairly well when its a bit cloudy.  Most PV systems are installed south facing and angled to match the average Sun angle or biased lower or higher as needed so they do not have and don't need a mount that tracks the Sun.  The 15% PV system will net closer to 10% because its fixed but the costs for a tracking mount are very high.  When it's even a bit cloudy a concentrating solar system like the Stirling decreases to near zero whereas a PV system doesn't lose much unless it's really cloudy.


Brian

[Red Squirrel]

Oh ok yeah that makes sense then.  Then add the extra complexity into the equation.  Well technically PV is way more complicated if you get down to the process of actually making the cells, but as someone just buying the parts off the shelf, PV is simpler to setup and install. 

My small 400w system has been able to keep my shed's battery topped up most of the time despite there not really being any sun here for most of the year. 

[MT]

Save the planet? Ok here we go again!

[raptor1956]

In about a billion years or so the Sun's output will have increased enough that no matter what we do life will no longer be possible -- any life.  A few billion years later when the Sun becomes a Red Giant it might engulf the Earth and then the planet will be gone for good.  But, between the time life ends and the Sun swallows the Earth the planet will get progressively more hostile as temps soar, the oceans evaporate, the magnetic field dies and the atmosphere disappears -- the Earth, even at this point will still be there.  The question is not will the Earth survive but will be be able to survive on it.  Putting aside the prompt killers like Global Thermonuclear War™, if we fail to curtail the poisoning of the planet we will find it hard to survive for much more than 100 more years give or take 50 years.  I wonder what Vegas odds makers would say about which end is more likely -- mushroom clouds or an Earth following in the footsteps of Venus...


Brian

[Circlotron]

It is rather un-intuitive that you can make things cold with heat but that is the way it is.

Makes me think of that Three Little Bops cartoon - "You gotta be hot to be real cool".