When advising a client this week I explained that unless you have a generator on board a yacht you do not have enough battery power to run a yachts refrigerator 24 hours a day when under sail or at anchor.

He commented 'surely you can run the yachts engine and charge up the batteries?' My answer to this was, 'yes of course you can do that, but you would need to run the engine for at least four hours a day to keep the batteries up to the required level of charge and do you really want to do that? when cruising along the Algarve there is almost always enough wind to sail and therefore you don't need the engine to propel the yacht, added to which in the summer heat running the yachts engine will only add to the ambient heat in the yacht's accommodation.'

During the first few days of a two week cruise in the Algarve from for instance Vilamoura, you might sail to Ria Formosa and anchor off Culatra for the night and from there to Quatro Aguas near Tavira where you would anchor, the next day you could sail to the Guadiana river and up to Alcoutim where you would anchor. After a night in the river you would have spent three nights at anchor and only needed to use your engine when anchoring and weighing anchor for perhaps thirty minutes a day, a total of ninety minutes in three days which will not have been enough to replenish what your navigational equipment, lights used in the evening on board and of course the electric anchor light will have taken out of the batteries, let alone running a fridge!

Ampair wind / water generator

It is true to say that most modern yachts are just not well suited for anchoring away from marinas and operating independently from shore power for days and weeks.

The right criterion for everything on a cruising boat is 'Keep It Simple'. But installing refrigeration on a sailing boat is not simple. Hardcore cruisers, like the well known Lin and Larry Pardey, do without it altogether. The rest of us want cold beers and the ability to keep food fresh. Many cruising boats have a wind generator and several solar panels, this helps but still does not supply sufficient power to run a fridge 24 hours a day in a hot climate. A wind generator works well when sailing to windward but sailing down wind when there is not a lot of wind blowing over the deck they are ineffective.

For down wind sailing the most effective way to generate electricity is to use an 'Aquair towed turbine' which involves turning a generator by towing a propeller at the end of a long rope, this device can also be used as a wind generator for when you are at anchor. The company that makes this device is in Britain and is called Ampair.

A top loading fridge

There are two different types of yacht fridge. One is just like the fridge that you have at home in that it has a front opening door, the disadvantage of this type is that every time you open the door you loose all the cold air. The other type is top opening and therefore when you open it you do not loose the cold air, the only small disadvantage is that if something that you need to get is in the bottom you have to get everything else out to get at it, but if you have baskets stacked on top of each other that is not too difficult.

Most boat fridges work on a 12v DC compressor and whilst these have become more economical on power in recent years, to be effective would need a minimum of 3 inches of insulation and the boat should be equipped with at least a 100 AMP alternator and a smart regulator.

The total battery capacity should be at least 500 AMP hour and as I explained at the beginning of this article you would need to run the yachts engine for a minimum of 4 hours a day.

There is another type of refrigeration system with a compressor mechanically driven from your engine. This system very quickly freezes a plate in the fridge and to do so you will only have to run your engine for about half an hour a day. But there have to be drawbacks to this choice or everyone would take it. The first problem is that the compressor has to be mounted directly on the engine, and this can be difficult or impossible if the access or space around your engine is limited. Next, a mechanical refrigeration system is likely to cost more (initially) than an electrical one, although if you add the costs of extra batteries, beefier alternator, wind / water generator, solar panels etc it is actually a much cheaper system.

Getting such systems right is essential for safe and happy long-term cruising. Ask lots of people and take the take the advice of experts. It is expensive and discouraging to repeat the mistakes of others.