Theory On Zero Electricity Ice Maker (No Fertilizer)

This is very much a messy idea in my head, my background is computer science, not fluid dynamics.

I watched this video from Geoff Lawton about clean energy where he mentions Roman aqueducts being able to create ice. I have been unable to find any other information on this.



That reminded me of this video about a Tromp + Ram Pump combo:




So I wonder if given a reservoir of sufficient elevation with a tromp-hammer below it pumping water back up and compressing air could that water be dropped down through a venturi tube and have the compressed air injected into the stream freezing it? Like how compressed air cans get cold.

I think the freezing point of water drops to ~300 Kelvin around 1Gpa could Bernoulli's principle be used to increase pressure by taking advantage of the pressure differential? If enough functions are stacked, gravity flow of the water, compression of a venturi tube, injection of compressed air, diameter/insulation of the pipes could the water really freeze?

Obviously, there could be an experiment here and ram pumps require a careful balance of elevation and I'd imagine the Roman ice thing is a balancing act also. Imagine instead of ice coolers at gas stations there was a water tower and you go up and cycle a ram pump and an ice cube shoots out the other end. The cold equivalent of a RMH.

Am I on to something here or is Geoff just spreading woo-woo science? I'd like to see a video of this effect in practice.

Scientific American magazine ran an article about making ice in the desert underground.
It was done by the advanced civilisations of the Iran ' Iraq  and Saudi areas.
I cant remember all the details at the moment.
From [url=The secret here is a process known as "night-sky cooling." On dry, cloudless desert nights with the cold vastness of space laid bare above the surface of the Earth, heat can readily radiate from substances like water, escaping from the atmosphere to space itself, where temperatures are roughly 450 degrees below zero Fahrenheit. So much heat can radiate from water that ice can form at ambient temperatures as high as 41 degrees Fahrenheit.]Real Science[/url]
"The secret here is a process known as "night-sky cooling."
On dry, cloudless desert nights with the cold vastness of space laid bare above the surface of the Earth, heat can readily radiate from substances like water,
escaping from the atmosphere to space itself, where temperatures are roughly 450 degrees below zero Fahrenheit.
So much heat can radiate from water that ice can form at ambient temperatures as high as 41 degrees Fahrenheit."
From The culture trip
"It’s all about physics. Once water is stored inside the yakhchāl, it’s able to freeze into ice because of the extremely low temperatures that the structure creates.
The hole in the center of the ceiling allows cold air to enter and make its way all the way down to the subterranean bottom, where water is stored.
The cone-like structure is also designed to make any hot air present inside the yakhchāl make its way out.
The insulating materials used to build the structure – including sand, clay and even goat hair – ensure that the inside of the yakhchāl remains much cooler than the outside temperatures.
These materials also make the structure impermeable.
This brilliant invention is only one of the many ways in which ancient society handled the desert and made it a more inhabitable place to live long before modern technology.

It is an interesting idea in any case. I presume it is possible. First I would calculate the total potential energy of the volume and elevation of the water supply available. That will tell you the maximum amount of ice the system can make if it were perfect. I would guess a system like this might be around a few percent efficient, so take a few percent of that total. I would imagine using the water to turn a refrigerant-filled heat pump would be most efficient, and a Stirling pump next after that.

I've heard of those. The difference is a yakhchāl requires a 100ft hole. What I'm proposing would require a 100ft water tower that instead of removing heat via evaporative cooling would lower the freezing point, and flash-freeze the water using compressed air.

Why are you getting that complicated?  The ram pump will produce compressed air as part of its natural operation.  Back when the air chamber needed to be filled steadily before foam filled bladders and bladder tanks they used a hole in the pump chamber called a snifter valve.  During the high cycle it squirted water out the valve.  But when the pressure went low it inhaled a breath of air which then rose to the top of the pump where it was pushed thru the pressure check and into the air and water chamber.  At some point I went by and article on adding another swinging check that reduced the amount of water squirted out relative to the amount of air inhaled with each pump cycle so they could pull more air making a greater amount of compressed air at the cost of pump efficiency.  The valve mostly doesn't plug off because it is constantly sucked on and the blown out cyclically.

Now my wild and crazy dream here is to make lower grade compressed air and run it thru a combination of a compounder to raise the pressure of a tiny bit of the air fairly high while venting most of the air.  A compounder is just a large 2 way air cylinder driving a small 2 way cylinder acting as a compressor.  Good ones are multiple stages to help gather the vent air.  Now can we add vortex tubes in the vents to increase cooling a bit?

Now I was looking at another source of compressed air.  My dream was using a water wheel in canal at a check to drive a spiral pump.  Fairly high pressures should be achievable from the pump.  It makes alternating air and water at pressure.  Then compound that with the goal to make small quantities of several thousand PSI air cooled to my local ambient and then release thru small orifice producing cryogenic temps.  With roughly 5 feet of fall and normal flow in the canal I would typically have 15 to 20  hp.  Lets say I could get even 10% effiency.(think somewhat better should be possible as a backshot wheel can reach 80% to 90% efficiency and this pump is also very efficient if moving slowly)  That would give me 1.5 to 2 hp worst case and possibly 18 hp at best.  Now I know my 5 hp compressor at the shop does a bit over 9 cfm at 100 psi so I am probably looking at 3 cfm output minimum.  But by the time that goes thru a compounder my high pressure gas output will be less than 1 cubic foot per hour on the low end.  But remember the process of venting the compounder will produce cool air too.   So the thinking was cooling a root cellar to refrigeration temps with the vent air and chilling a freezer inside with high pressure vent air hopefully to cryogenic temps  

The spiral pump could be an option but you will always have a fixed amount of compressed air based on the size of the pump, with a trompe you have tank options and can choose where to inject the compressed air back into the stream.

With a ram pump and a trompe, you get 3 separate streams water, air, and wastewater.

Let's say you have a 100ft water tower that was piped downward through a venturi tube, according to Geoff that could create an ice slurry like the Romans did.

I think if the water is dropped first through to a ram pump where the air goes through a trompe and the water gets raised back to the 100ft mark THEN dropped straight down through a venturi tube THEN have the trompe inject compressed air into the stream (before or after the valve I'm not sure).

That way you could capture compressed air at multiple points instead of just at the top of the venturi tube increasing efficiency.