Anonymous wrote:

On those days you could plug in a small (seven litre) peltier type cooler and have cooler (20C below ambient) bubbly.  These are the standard issue electric coolers that can be found in every size and almost for free used.  They are horribly inefficient, but should you find that on the hottest sunny days you have excess power, it could be plugged in once the batteries are fully charged in order to provide some cool bubbly at the end of the day.  

I did some experimenting with a couple of these in last summers camping trip. We did have power and I did not bring my watt/amp meter with me so I have nothing to say about the power draw. They do have enough cooling to freeze things but the 20C (40F) temperature difference is certainly fixed. This meant that it's use is not obvious or intuitive. It is best to have it turned off when it is warmest out and use it as a cooler at such times. Then when the air temperature is cool run it to a bit cooler than wanted and maybe use a water buffer close to the mechanism that can freeze without harm.

There are peltier units made for yacht use that pump sea water through to keep the waste heat parts cooler for use when the sun is shining but their automation is just the standard turn it on when the inside is hotter than a certain temperature. They do not shut it off if the outside temperature is too hot to get to that temperature anyway. So those are actually worse than the cheap portable ones as they use power for pumping as well as having sub-optimal automation. So simple and long lasting (aside from the the water pump and hose) but probably not a good idea.

Alternatively, Twinbird makes nice sterling motor powered cooler that others have reported uses close to half the power of the Danfoss-based units.

Cool, I like the idea of sterling based cooling and looking through their web site I see they also sell just the cooling units. It appears they are of the free piston type and quite compact. The cooler part is basically "thrown in" for free as the cooling device costs almost as much as the cooler. These chillers are made for cooler use than the compressor type and because startup it quick and easy, can be turned on and off for very short periods of time allowing for precise temperatures. They are therefore well suited for medical applications (where money is no object... to the practitioner anyway). I think I would not consider this for a portable unit, but I might for a built in unit. Still 1000USD (plus) is pretty steep.

Anonymous wrote:

I have absolutely no intention whatsoever of building a fridge into my boat.  As I have said before, the space taken up in the galley, to say nothing of the requirement for insulation, make it deeply unattractive for something that is a luxury and indeed, not that much use in the winter.

Absolutely! Me neither!

When we first crossed the Atlantic in 2006, we only had a 50W solar panel.
This was enough to supply our fridge with a temperature of 8 degrees, our electronics and navigation lights (LED) and the autopilot (on a trim tab).
The group is a danfoss 35, which offers the possibility of speed and cut-off/opening adjustments to an electronic module (low voltage safety).
The flat o-shaped evaporator is designed for a capacity of 130 litres, and we have manufactured an 85 litre box.
The insulation of this one is made up of :
( From inside to outside) 1 mm aluminium sheet, 50 mm polyurethane foam covered on each side with aluminium foil, 10 mm flexible insulation material consisting of 7 layers of alternatively bubble plastic and aluminium foil, and a 10 mm plywood box painted white on the inside. All that without thermic bridges.
The cover is on top with an elastomer seal and inclined edges.
We don't make ice cubes, but the beer is very cold! This allows us to keep fresh vegetables longer, leftovers from cooked dishes, and also the fish that kindly invited itself on board!
For 14 days we hadn't run the boat's engine.
The estimated consumption is about 25 amps/day based on the operating time of the compressor.
 This fridge is on board since 2004, we had to recharge with gas twice because of micro-leaks at the quick couplings. Since they have been tightened strongly there is no longer any problem.
It is not always easy to remove food cans when they are at the bottom because of the depth, and you have also to wipe the condensation water regularly because I still haven't made a drain!
We hope that this feedback will help!

Annie Hill wrote:

  10 litres, or even 5, is much more what I would want, but I doubt I could run even that with the 2 x 75 watt solar panels, which are all I want to fit and have to run my (otherwise minimal) needs as well.  I was vaguely hoping that someone had come across something that gave everything for nothing.  Like digital cameras!

Have you decided what to use on your wee cat, David?

Two 75 watt solar panels should run a good 12 volt compressor fridge of up to 18 litres and leave enough for the other power requirements. I should have mentioned that with the setup on our current boat where the fridge battery is fully charged by late morning, I then parallel the batteries and charge the other house battery with the surplus power.

Regarding my wee catamaran, and now that I have started on the bridge deck and cabin structure I realise it is indeed quite 'wee'. It is going to be a bit like moving into a tiny home. But I still fancy the idea of zipping nimbly around the coast and using the 200mm hull draft to anchor in all sorts of interesting inlets. So when setting the boat up for cruising I will use what has worked well for me in the past. If fitted, refrigeration will be a Waeco cf18 plug in chest fridge for which I am sure I can find space and I know from past experience that these units work well with minimal power usage. There will be enough cabin top space for two 60 or 75 watt solar panels. Solar panels, controller and AGM battery will come from AA Solar in Silverdale. They have good quality products at a reasonable price and I have had a very long life out of their batteries. I realise the galley is going to have minimal bench space so I will have a plumbed in sink with fresh water from a 50 liter bladder tank. This in preference to a fitted stove. I already have the hand operated fresh water pump left over from another boat project, and I have a foot pump for the salt water. Having done research on stoves I will use a single burner canister camp stove which I already have, although it has some kind of special infra-ray burner which heats very quickly. I think this is more practical than a plumbed in LPG stove installation, although I do not like the idea of generating a pile of empty canisters. Research is still ongoing re alcohol stoves. 

I have absolutely no intention whatsoever of building a fridge into my boat.  As I have said before, the space taken up in the galley, to say nothing of the requirement for insulation, make it deeply unattractive for something that is a luxury and indeed, not that much use in the winter.  The only thing I would consider would be a plug-in unit that requires very little in the way of electricty, so that I could cool my bubbles and perhaps keep some salad leaves and other little treats a bit longer, when I can buy them.  There is space in the lazarette for a small unit and if the price is right, I might consider it.  I know David Thatcher is thorough in his research, so am simply waiting to get the the benefits of it!  His example requiring 2 x 60 watt panels is way beyond my wishes and I probably won't bother in the end.  But technology is ever evolving and someone may come up with an inexpensive, small and economical unit that would suit someone like me.  I can cope with warm bubbly - and beer - if the alternative is to turn my boat into a generating station.

I hear what you are saying, Paul, but at present you aren't living on board full time, and therefore opening and shutting the fridge constantly and replacing cold items with warm.  10 litres, or even 5, is much more what I would want, but I doubt I could run even that with the 2 x 75 watt solar panels, which are all I want to fit and have to run my (otherwise minimal) needs as well.  I was vaguely hoping that someone had come across something that gave everything for nothing.  Like digital cameras!

Have you decided what to use on your wee cat, David?