Absorption coolers use heat to regenerate their refrigerant. Two common types are a water vapour-LiBr chiller, and an ammonia-water chiller (in fact Einstein patented a mini bar chiller design still used today that has no moving parts, using just helium or hydrogen and gas absorption/evaporation to move refrigerating gasses around)
Single effect chillers have a low Coefficient of Performance (CoP) roughly around 0.4-0.6, meaning for every watt of heat you apply to a single effect chillers, you move 0.4-0.6W of heat, but they only need a minimum of 90⁰C in heat to power them.
Double effect chillers can reach 0.9-1.2 CoP.
Flue gasses are typically hotter than 90⁰C, so you’ll often see absorbers part of combined heat and power systems. Cooling in the summer, heating in the winter. All using waste heat from power generation.
What I find the most fascinating about them is they work using heat. The only power you need to apply is for a few pumps to move fluids around at low pressures, otherwise the primary refrigeration energy comes from heat regenerating the refrigerant.
I’ve often wondered what a district cooling system using these would get for efficiency if you colocated it with something energy hungry like a cement kiln or glass kiln.
Video of how a double effect chillers works
Edit: these are used already for district cooling, just usually for a campus like a university or government complex. The big benefit is you can run them on marginal heat sources, even off of low grade geothermal.
I had an ammonia type fridge in my trailer I lived in, that ran off propane that was pretty great. I had 2 30lb bottles for my trailer and they would get me a month each of refrigeration and stove use for most meals. Filling a bottle cost around 30 dollars. So maybe there was more energy used compared to a compressor type fridge, but the dollar cost to run as well as convince was well worth it since our solar system was able to sustain us year round without a fridge drawing on it.
Yeah that’s the big thing. Absorption chillers can work on marginal heat that isn’t useful for much else except maybe boiler economization. They run at low temperatures but aren’t efficient.
If you have a neighboring cement kiln that exhausts at 300⁰C, that’s perfect for use in district heating or cooling?
It’s basically a heat recycler for trash heat you might throw out anyways.