Cooling with heat - is that even possible?

The idea is quite intriguing, let's see what we can find:  

Absorption cooling

Absorptive refrigeration uses a source of heat to provide the energy needed to drive the cooling process. This heat source can be solar, kerosene-fueled flame, waste heat from factories or district heating systems...etc. Absorption refrigerators are a popular alternative to regular compressor refrigerators where electricity is unreliable, costly, or unavailable, where noise from the compressor is problematic, or where surplus heat is available.

In a typical cooling system, a refrigerant with a very low boiling point is used. When this refrigerant evaporates (boils), it takes some heat away with it, providing the cooling effect. The main difference is the way the refrigerant is changed from a gas back into a liquid so that the cycle can repeat; an absorption refrigerator changes the gas back into a liquid using a different method that needs only heat, and has no moving parts. 

*In my head: Ok, still sounds too good to be true at this point... 


How does it work?
Simple salt and water system

A simple absorption refrigeration system common in large commercial plants uses a solution of lithium bromide salt and water. Water under low pressure is evaporated from the coils that are being chilled. The water is absorbed by a lithium bromide/water solution. The water is driven off the lithium bromide solution using heat.

Found a very simple diagram on wikipedia:

• Evaporation: A liquid refrigerant evaporates in a low partial pressure environment, thus extracting heat from its surroundings – the refrigerator.
• Absorption: The gaseous refrigerant is absorbed – dissolved into another liquid - reducing its partial pressure in the evaporator and allowing more liquid to evaporate.
• Regeneration: The refrigerant-laden liquid is heated, causing the refrigerant to evaporate out. It is then condensed through a heat exchanger to replenish the supply of liquid refrigerant in the evaporator.

*In my head: The idea sounds scarily simple... but I do have 2 questions..

- It's interesting that additional external heat is required to separate salt & water at the end of the process (but the system is giving off heat - can't you just use that?). 

- Also, your hot vapor is carried to where the salt is and being absorbed. But the heat carried over at the same time will also heat up that part of the system (and high temperature releases vapor from the salt). Doesn't the heat stop the salt absorb more water?

I think it has got something to do with the fact that you will need a salt that takes a lot more energy to dry (compare to the heat you generate).

 Here is another configuration: 

Water spray absorption refrigeration 

Another variant, uses air, water, and a salt water solution. The intake of warm, moist air is passed through a sprayed solution of salt water. The spray lowers the humidity (salt absorb water like the previous example) but does not significantly change the temperature. The less humid, warm air is then passed through an evaporative cooler, consisting of a spray of fresh water, which cools (taking heat away as it evaporates) and re-humidifies  the air (due to the evaporated water). Humidity is removed from the cooled air with another spray of salt solution, providing the outlet of cool, dry air.

The salt solution is regenerated by heating it under low pressure, causing water to evaporate. The water evaporated from the salt solution is re-condensed, and rerouted back to the evaporative cooler. 

*Ok, so it seems to be possible (without going into the physics). Now, in hot countries with a lot of sun, this might just be the brilliant cooling solution they need! Have I lost you yet?

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