Buoyancy device by phase change of water to ice

[sm0ky2]

I lost my lengthy reply.
Short version: look into temperatures and depths. I suspect close to freezing water will prove very hard to find.
It would be a cool experiment to make an ice cube near the surface and at the bottom of a lake, same water temperature, compare the energy needed. How much energy could be extracted needs to be realistically assesed.

I like tidal flows more. Only side effect might be that when we hamper ebb and flow, we're making the moon crash into Earth. It's only logical.

Here's an ancient Dutch concept for a tidal like in the North Sea.
My favourite thing about it is that this form of construction gets more efficient as it's built bigger.
Twice the length of surrounding structures...4x the water contained/drained per tide flow.

It inverts at some depth, a little backwards from the way logic wants us to look at it.
One might assume the higher pressure would increase the temperature
in some cases, this is true within a given depth range,
But at great depths, pressure greatly increases. Due to the PVT relationship, and the associated decrease in volume, temperature actually drops. (deep sea gets down to about 4 degrees above freezing)
Bottom of a lake should be better, because it is closer to the freezing point.
and the density under this pressure should tip the displacement equation in our favor.


a few criteria:

If your math is correct, you're looking at a maximum depth of around 10,000 ft

The refrigeration system should be designed to operate under pressure
and the heat exchange mechanisms will need to be as efficient/fast as possible.
aluminum has high thermal conductivity, however most refrigerator radiators are fragile
So maybe something from the computer/electronics industry, copper tubing, etc.
may consider replacing the paint on the compressor with a thermally conductive paint, if you use a compression based refrigerant system.
but to be honest; electronic or elastic systems can perform the same function
As can linear motors (sterling, acoustic, etc)
I would just keep in mind a fast transfer of heat to the lake when choosing materials in general.


for buoyancy energy generation (water, air, or any fluid)
the height of the column is the determining factor.


Filling a helium balloon high up in the air it doesnt have very far to rise
But fill it at the ground tied to a cable, you can compress more helium to than you used.


temperature difference also is important.
with helium in air (or a more dense gas) you want hot helium rising and cool it on the way down.


But for ice: you want just around or slightly below freezing.
Go too cold and it begins to contract again. Go too cold under very large pressures it will deuterate. (great heat and pressure can also but to a lesser degree)


you wont get that cold, and a lake probably isnt that deep
but there is a scale for ice (based on the purity) it will expand at the freezing point, then contract at a colder temperature.
hot water goes through this change at a temperature range also right around boiling, after it condenses and releases its trapped gasses.
It is this aspect of H2O that gives us this buoyancy condition.
(and subsequently why hot water floats)


your concept is very intriguing, i think with enough flushing this out, we may be able to create a working ice-buoyancy system.


sort of an after though:
If using a compression-based refrigerant system, there are two scenarios which stand out.
One is designing a system that makes use of the water pressure of the lake.


The other compresses the gas above water and expands it into an underwater chamber where the ice is made. (similar to the balloon system someone posted above, but using a static chamber to expand the gas and a heat exchanger to cool the water below freezing).


Also: need to think about part; as we don't want heat from the lake melting the ice on the way up via the heat exchange mechanisms.

[Willy]

                RETURNING TO THE
                     BUOYANCY BY
          WATER TO ICE PHASE CHANGE
                             SUBJECT

smoky2

Thanks for the observations and considerations given.

I expect,  I'll need to examine and then cogitate upon it for a spell.
Probably, I will have some questions / need of some clarifications.

[Willy]

partial quote

a few criteria:
If your math is correct, you're looking at a maximum depth of around 10,000 f

1 foot of height of water in a column exerts 0.4335 psi

29,007.5 PSI divided by 0.4335 = 66914.6 feet or 20395.57 meters of depth
in water before there is a significant change in the freezing temperature of water.

The density of liquid water is 1 g/mL.
The density of liquid water is 1 g/cm^3
The density of ice is 0.92 g/mL
The density of ice is 0.92 g/cm^3
The ice is 8% less dense than the water.

Therefore, for every 1 Kilogram of water frozen at depth we get 8%  of 1
Kilogram of buoyancy in water.

1 kg = 9.80665 Newtons
9.80665 Newtons * 0.08  kilograms = 0.784532
newtons of buoyancy force for each kilogram of ice.

0.7845  buoyancy joules per kilogram of ice at 1 meter of depth.

4.184 joules = 1 calorie.

It requires 4.184 joules to increase the temperature of 1 gram of water by 1 degree
centigrade.

It requires 4184 joules to raise 1 kilogram of water by 1 degree centigrade.

Below about 200 meters depth, ocean water has an average temperature of 4°C (39°F).

Given that we begin with water at a temperature of  1 degree centigrade.
Given that our refrigeration device is 100% efficient.


0.7845 buoyancy joules per kilogram of ice at 1 meter of depth.

4184 joules to raise 1 kilogram of water by 1 degree centigrade.

4184 / 0.7845 = 5333

5333 meters is the break even point.

[Willy]

smoky2

Is this the idea that was rolling around in your mind ?
Refrigeration system at the surface ?

Using an aspect of the idea from the post by  panyuming here @

https://overunity.com/19442/buoyancy-device-by-phase-change-of-water-to-ice/msg576918/#msg576918

His "figure 2.jpg"

We can get all the free refrigeration we want.

Surface air temperature can be much colder than any thing we need.

Exchange heat with, for example ambient arctic air.

We could pump a refrigerated cooling fluid from the surface, through an
insulated tubing to depth while not having to overcome pressure at depth,
as long as the output end of the tubing returns to the height of the
water surface / height we pump the fluid from.

The energy cost is basically, overcoming friction in the tube while pumping.

Thanks again panyuming

Brain pools can certainly rock it... some times.

[Willy]

Another observation.

Making sheet ice allows faster freezing, but also faster melting while
rising.

If the ice sheets are formed with lines of perforations,  their own buoyancy (as they rise)
can be used to break the sheets into smaller sheets and then stack those smaller sheets into
a cube form. This, before they enter into a cube shaped insulating jacket. All or nearly all,
accomplished by the energy of their own buoyancy  .

Decreasing the ice surface area to volume ratio slows down melting.

A neutral buoyancy, cubical insulating container for containing a large block of
ice, that's doable.

Splitting perforated ice sheets progressively down into smaller square sheets,
by use of their own rise due to buoyancy, that's doable.

Stacking the square ice sheets in to a cube, by use of their own rise due to
buoyancy, that's doable.

Placing them into a cubical insulating container, by use of their own rise due to
buoyancy, that's doable.

Closing and latching the sixth side of the containers, by use of their own rise due to
buoyancy, that's doable.

A neutral buoyancy rope or chain, that's doable.

Place the electric generator at the top of the rise

Reverse most of the process at the top of the rise.