One of the top electric energy consumers on a yacht is the fridge and freezer. The efficiency of the machines that take the heat out of the cooled space is heavily dependent on how efficiently the heat energy can be removed from the cooling liquid.
Most standard yachts use a cooling element with a fan, sitting inside the boat. This does not work well at all when you are in warm climates, and it is noisy. As an alternative you can cool the liquid using seawater, but the heat exchangers commercially available for this are always made of bronze, which is a big no-no on aluminum hulls.
But aluminum itself is a great heat conductor, so I decided to put the heat exchanger directly inside the hull itself instead. The hull plate is very efficiently cooled by the surrounding water. This way I get better cooling, lower power consumption and no noise. The two heat exchangers are also the last thing getting mounted before we start to paint the hull inside.