The engine driven cold-plate system is a great system, but it is just that - engine driven.
Most of the "real" offshore-cruisers use a cold-plate system. They are very efficient and the "old" theory was that you have to run your main or genny anyways to charge the batteries, might as well put an extra load on it and refridgerate at the same time.
However, it seems to me there has been a considerable decrease of those as of late to more of an Adler-Barbor air (or air & water cooled compressor). They are less efficient (although I understand the combo unit is an improvement). They will draw about 5 amps when running, and we run our about 8-10 hours a day in the tropical climates (with really good insulation, which is another topic). How long they run, depends of course, on the insulation, how often you open your box, and how the box opens (ie, does it have a front opening door that lets out all the cool air every time you open it).
My boat came with the air cooled, as did my other two previous boats. Short of sticking a ice pick through the coils (don't ask), they are dependable, and very modular for ease of installation. They are also relatively cheap. Mine has never failed.
In my opinion, I think you will see cold plates dissapear. This will of course be very debated, but let me tell you why: The technology for charging batteries (outside of an engine) has vastly improved. If you invest in good (the emphasis being GOOD) solar panels, wind generators, and an awesome charge controller, you should find that you have ALL of your power requirements taken care of - and more than enough to run your refridgeration. You can also increase your battery bank capacity (I reccomend Lifeline AGMS) to get you through cloudy, no wind days when they happen... which does not happen much where you are heading.
In essence, if you do not upgrade your boat to "off the grid" cruising power systems, you will be running your engine all the time anyway... why not spend the extra money where it can serve dual purposes?
Just my thoughts. If you want specifics on this, including make/models of what I use, just PM me or you can ask here.
- CD