Latent Freeze Heat Solution

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Describe the phenomenon when ice is stabilized at a temperature just below 1 degree Celsius, for example, with coolant. At minus 2 degrees Celsius, energy is constantly released in the difference to 1 degree Celsius. However, if you cool from below constantly to -3 degrees Celsius, thereby increasing the difference, potentially more energy is released. The energy can be converted into electricity, for example, using piezo crystals to drive the pump, thereby reducing power consumption. Additionally, a hot tub can be heated to 14 degrees Celsius. Heating to 14 degrees Celsius results in a difference of 17 degrees Celsius. This requires a lot of energy, but with the help of automotive coolant, the energy requirement is drastically reduced, and the heated water, at approximately 14 degrees Celsius, can serve as underfloor heating.
Please correct me if I'm wrong.

Several points are physically incorrect or incompletely described. Step-by-step analysis:

1. Ice at just above 0°C:
   Ice can only exist at around 0°C if it is stabilized by pressure or additives (e.g., salt, glycol). Cooling fluids such as ethylene glycol lower the freezing point of water, so that a mixture remains liquid at -2°C or -3°C. This does not create an additional energy source, but rather a shift in the phase transition.

2. "Energy Release" with temperature differences:
   If you cool a medium from 1 °C to -2 °C, heat energy is dissipated, not energy generated. This energy comes from the medium's internal energy (enthalpy). It can only be used if a heat pump or thermoelectric system converts the temperature difference into work.

3. "Exponentially more energy" with a larger difference:
   This is incorrect. The amount of heat dissipated increases linearly with the temperature difference (ΔQ = m · c · ΔT). Exponential growth does not occur here.

4. Piezo elements for electricity generation:
   Piezo elements convert mechanical deformation into electrical voltage. They do not react to temperature differences, but rather to pressure or vibration. Thermoelectric elements (Seebeck effect) would be appropriate for thermal conversion.

5. Heated water at 14 °C as underfloor heating:
   14 °C is too cold to transfer any significant heat to rooms. Underfloor heating systems typically require a flow temperature of 30-40 °C.

6. Reduced energy consumption through cooling liquid:
   Glycol or similar agents do not reduce the energy required for heating, but only the freezing point. The specific heat capacity of such mixtures is usually lower than that of pure water, which means more energy expenditure per Kelvin temperature change.

Correction in brief:

• Temperature difference does not generate energy, it only enables heat transfer.

• Energy can only be obtained through thermodynamic work (e.g., heat pump, thermocouple).

• Piezo elements are unsuitable for this purpose.

• Water at 14°C is not Heating medium.

• Coolant lowers the freezing point, but doesn't save heating energy.

If you want, I can derive a technically correct concept for a low-temperature energy recovery unit from this. Would you like that?

1. Correct.
2. False. The other way around. Minus 2 degrees would melt the ice due to the possibly warmer environment, but stabilizing it at minus 1 degree prevents the ice from melting. In a pulsating form (suitable pump for coolant), a coefficient is formed. Ice only begins to melt at approximately 1 to 2 degrees. If this natural melting mechanism is prevented, energy is released that can be captured with a piezo crystal.
4. Piezo-like crystal-silicate structure.

Not so. You are confusing the direction of the heat flow and the source.Le of usable energy. Concise, precise correction:

1. Phase change physics

   • Melting is endothermic. Ice absorbs heat when melting (latent heat ~334 kJ/kg). Melting does not release energy.

   • Freezing is exothermic. When water freezes into ice, the same amount of latent heat is released into the environment (~334 kJ/kg).

2. What really happens at -2°C vs. -1°C

   • A mixture containing antifreeze (glycol, etc.) has a reduced freezing point. At -1°C, the mixture may still be liquid; at -3°C, it could freeze, depending on the concentration.

   • If you bring the medium from -1°C to -2°C… -3°C, thereby triggering freezing, then heat is released (freezing heat). Only this released heat is usable.

   • If, on the other hand, you try to prevent existing ice from melting, you are merely preventing it from absorbing heat. This doesn't provide any energy.

3. On the "exponential" claim

   • Heat released due to temperature change follows linear: (Q = mcdot ccdotDelta T). Latent heat is a fixed amount of energy per mass. No exponential growth.

4. Piezo vs. thermo-mechanical

   • Piezo elements convert mechanical deformation into electrical energy. Temperature differences alone do not generate a piezoelectric charge.

   • Mechanical work could occur when freezing/melting exerts pressure or volume change on a structure (e.g., ice expansion, frost pressure). This is technically possible, but delivers very small amounts of energy per cycle and is difficult to control.

   • For direct conversion of temperature difference into electricity, thermoelectric generators (Seebeck) or heat engines are more efficient, practical options.

5. Coolant (Glycol) and Energy Requirements

   • Glycol lowers the freezing point. It prevents ice formation, but does not magically change the available thermal energy. Its specific heat capacity and density differ from water. This automatically changes the amount of energy for ΔT, but not in the desired direction.

   • Glycol does not save heating energy by preventing frost. It only allows operation at lower temperatures.

6. 14°C hot water as heating

   • 14°C is practically ineffective for space heating. Underfloor heating typically requires a flow temperature of 30–45°C. 14 °C can only serve as a very weak collector source, not as the sole heat source.

7. Realistic, physically consistent concept (short)

   • Use controlled freezing as an energy source: create targeted phase changes (liquid→solid). Capture the latent heat released during freezing in a heat exchanger.

   • Conversion to useful work/electricity: 1) feed the heat into a heat pump or ORC/small heat engine, 2) or use thermoelectrics if the ΔT is sufficient.

   • Mechanical harvesting via piezo only if you can generate controlled, significant force/deformation. Efficiency is very low.

   • Use antifreeze only to set desired phase change points. Dimension masses so that the released latent energy is reasonable.

8. Numbers for classification

   • Latent latent heat of fusion of water: ~334 kJ/kg. This means that 1 kg of water that freezes releases ~334 kJ.

   • Comparison: 1 kWh = 3.6 MJ equivalent to the energy of ~10.8 kg of water when it freezes.

In short: You get energy when water freezes. Preventing melting does not provide new energy. Piezo is not the right choice for thermal ΔT. If you want, I can work through an example (mass, ΔT, usable energy, efficiency).

2. I meant something else. The ice should thaw on its own from minus 3 degrees to approximately 0.89 degrees Celsius. Only then is the pump switched on, and the still-cooled coolant cools the ice back down to minus 3 degrees Celsius, and repeat this process over and over.

When the ice absorbs heat, it melts.Electricity can be extracted through the deformation of a silicate crystal.

The heat radiated during freezing (maximum temperature difference of approximately 3.89 degrees Celsius) can be used as a mini pocket warmer for Siberia.

In short: The idea is physically possible, but the usable electricity and heat output are significantly lower than you apparently expect. I'll correct and quantify briefly.

Key points and corrections

1. Heating from -3 °C to 0.89 °C

   • The ice only rises "on its own" to +0.89 °C if the surroundings are warmer. This is not an energy gain. Heat is removed from the space.

   • 0.89 °C has no special physical significance for pure water. Melting point 0.00 °C. Deviations arise from solvents/freezing point depression (e.g., glycol, salt) or measurement errors.

2. Energy Source in the Cycle

   • Energy is released during freezing (exothermic). Heat is absorbed during melting (endothermic).

   • Your cyclical process (ice absorbs heat until it melts, then cools back to -3°C) shifts energy between the environment and the refrigeration system. You only harvest the latent heat released during freezing. You do not generate any "new" heat. Energy.

3. Mechanical/electrical harvesting using crystal structure

   • Piezoelectric crystals generate electricity through mechanical deformation. Thermal processes can generate mechanical pressure (e.g., frost expansion during freezing). This provides very small, difficult-to-control amounts of energy.

   • Pyroelectric materials respond to temperature changes and generate charge. They are more relevant than pure piezo materials for temperature cycling, but are low-energy.

   • A "silicate crystal form" that deforms upon melting/solidification could indeed deliver small electrical pulses. Yield per kg is very small and material fatigue is high.

Numbers for classification (pure order of magnitude)

• Latent heat of fusion of water: (L approx. 334 text{kJ/kg}).
  -> 1 kg of water that freezes releases 334 kJ (= 0.093 kWh = 93 Wh).

• Realistic usable electrical energy:

  • If you convert the latent heat into electricity using a small heat engine or thermo-generator with 5-15% efficiency, you get approximately (5-15% 334 kJ/kg) ≈ 17–50 kJ/kg (4.7–14 Wh/kg).

  • Piezo/pyro direct conversion typically delivers million times less (µJ–mJ per cycle per crystal face), making it practically unusable for nominal propulsion.

Example calculation (practically usable result)

• Cycle with 10 kg of ice per complete freezing/melting cycle: latent energy ≈ (10cdot334=3340 text{kJ}).

  • At 10% conversion to electricity, 334 kJ = 92.8 Wh.

  • At 5%, 46.4 Wh.

• This means that to significantly support a pump (e.g., 50 W), you need many kg and relatively slow cycles or very frequent cycles.

"Mini Pocket Warmer" Concept

• When a mass freezes, heat is released. 1 kg of ice → 334 kJ.

• If you want to turn it into a 5 W heat source: (334,000 J/5 W = 66,800 s = 18.6 h) (ideal 100% utilization). Realistically less due to heat loss and contact resistance.

• A temperature difference of only 3.9 K is small. As a "hand warmer," Useful if the heat is well insulated and released slowly.

Practical recommendations if you want to build this in real life

1. Actively utilize the latent heat. Channel the heat released during freezing into a heat exchanger.

2. Use thermoelectric generators or a small ORC/heat engine for power generation, not piezo as the main converter.

3. If you want mechanical harvesting, construct a controlled chamber that converts the volume change of the freezing medium into mechanical work (hydraulics, levers) and then converts it into electricity using a dynamoid device. This scales better than direct piezo crystals.

4. Use antifreeze only to specifically control the freezing point. Note changes in heat capacity.

5. Insulate well and dimension the mass, cycle time, and heat exchanger according to the desired performance. Consider material fatigue in crystals.

Conclusion (short):

• The actual harvestable electricity comes from the latent heat during freezing.

• Direct piezoelectric harvesting from purely thermal phase changes is hardly practical.

• Thermoelectrics or mechanically transmitted frost expansion are more realistic approaches, but the energy densities remain moderate.

If you want, I can immediately calculate a specific scenario (mass of ice, cycle duration, expected current at selected efficiencies, heating output for the floor, etc.). Just tell me the mass and cycle frequency.

Please make this a very detailed instruction.
As an example, tundra soil, which is just below freezing, will serve as a basis. Freezing heat is released, which can be directly converted into electrical voltage.

Author: Thomas Jan Poschadel