Quote:
Originally Posted by Big Dave
Thermoelectric cooling is very inefficient. COP of 0.4 or so.Your Rankine cycle AC is very efficient. COP of 3.0 routinely.
I have batted around the idea of using an adsoption machine for car AC. It would run off the exhaust and/or jacket water heat. Adsorption is also very inefficient (COP of 0.8 vs COP of 3.0 for Rankine cooling) but it has the virtue of being able to work OK with a very low temp heat input. Solar adsorption machines work A-OK with only 200 degree input heat. My thermstat is 203 degrees and my EGT (post turbo is in the 300 degree range.
Problem is that it is worthless until the vehicle gets warmed up enough to put out the requisite temps. So you have to retain the Rankine cycle unit. Also we now need ANOTHER condenser and it needs to be four times the size of the Rankine cycle condenser.
Doable, but a engineering problem.
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Big Dave,in Israel,solar ponds are used to gather and store heat,and heat-exchangers are submerged in the ponds,which contain a working fluid like 134-A which goes superheat,is expanded through a turbo-generator,pumped to a raised pressure to allow condensation back to a liquid at ambient temperature,then returned to repeat the cycle.They skip the lithium bromide absorption cycle with low efficiency,opting for the mechanical cycle.----------- For long I've believed that such a system could be boot-strapped onto vehicles to take advantage of waste heat.The system could also generate electric power,be completely hermetically sealed like any refrigeration unit.Do you see any potential for such a device?Obviously,for short commutes,it would be worthless,but for extended travel,the 66% waste heat of the I.C. engine would provide enormous energy input.And if the refrigeration cooled only the "occupants" and not the entire cabin,their would be "scaling" advantages as far as Btu requirements.