It may be because of the differences in language, but IMHO there seems to be a lack of understanding of what a keel cooler is.
There are several technologies for getting rid of the heat from the compresor:
air cooling, where a motor has to spin a fan to blow air athrough the compresor. (not so good when ambient temperature is hot and needs the energy to power the fan)
Sea water cooling, where sea water comes in through a hull fitting and is pumped up to the compressor and used for cooling. (effective, but fouling can shut off the inlet, and extra power needed for pump)
Fresh water cooling, where fresh water goes through a heat exchanger of coils underneath the boat, and is pumped up to cool the compressor. (effective, and avoids the problem of fouled inlets, but does have risk of damage to the heat exchange coils, and the extra drag imposed by them)
Keel Cooler where the liquid used to cool the compressor is circulated through a sintered bronze block attached underneath the boat (similar to the ground used for SSB).
This is the most efficient type as it minimises the power consumption of the system. It is also the least vulnerable of any of the hull penetrating systems. Gets my vote.