Cooling the Cabin of a Sailboat

[DocBrown]

That unit takes the 220 and rectifies it to DC. That is why I said to run straight DC and skip the inverter and internal rectifier. It would mean messing with the internal circuit, but the power savings is worth it. I am not sure why they say it will run on 350 watts based on the SEER and then suggest 650 supply, except as over engineering the breakers and wiring.

I said several panels, or better yet buy 600+ 1.8 watt solar cells at 1$ each off ebay and build a kW+ solar power supply customized to fit your boat. Having the battery power to run the AC at night is the price of doing it that way, unless you want to run a generator.

I have been looking into Stirling engine generators for silent power generation. There are no commercially viable products available yet, but I think I could make one.

[Pete7]

Originally Posted by Dockhead

That's a really, really interesting question, which no one answered. Made me think. He means that the ocean some depth down is going to be cool, even when it is hot as h*ll and the water at the surface is bathtub warm. Instead of spending tons of energy on a compressor, why not drop a long hose down into the ocean into a cooler layer of water, and pump the water through a simple heat exchanger? Has anyone thought of or tried such a thing?

Occasionally as divers we do find thermoclines underwater and the difference in termperature will produce some interesting visual effects at the boundary layer, often shimmering like a layer of silver and blured vision as you pass through. The other very noticeable effect is a big change in temeraturre that would make you shudder as you pass though.

Sadly thermoclines rarely occur in tidal water as the tides mixes the water around too much. Instead they are normally found in lakes. Lake Bala in Wales has such a well defined thermocline at 40m that even the rib echo sounder couldn't penetrate the boundary to give us the actual depth, so we dived into a lake with the plan to go to the bottom only we didn't know how deep we would need to go.

So whilst there are layers of water with different temperatures, they aren't that common or are rarely noticeable to someone swimming through them so the variation in temperatures is only small or you would feel it immediately.

However the top 6" is often warmer and occasionally more salty so if you fitting an intake for AC then it should be down deep.

Pete

[Pete7]

Why has no one suggested a water bed plus and spare drinking water for ocean crossings

Pete

[hellosailor]

"Sadly thermoclines rarely occur in tidal water "
Ah, no. I've been skin and scuba diving in plenty of tidal waters, and when you hit the thermocline (often just ten feet down) you really feel it. They are there, even in tidal water where the sun may warm the surface layer--but nowhere near all the way to the bottom.
But between filters and pumps and plumbing and heat exchangers...still not a practical way to get BTUs off a small boat.

[DocBrown]

Here is a company that has converted a split system to run straight DC (48v) and switched to a 48 volt DC compressor. DC Air Conditioner: 12 Volt 24 volt 48 Volt DC Air Conditioners DC Solar Air Conditioning http://www.solarpanelsplus.com/image...tcoolDemo1.JPG In the demo picture you can see that this 18,000 BTU system is pulling 13.0 amps at 58.6 volts for 760.5 watts or 23.67 SEER. The compressor probably pulls more watts at lower voltages, but that is excellent efficiency for that size system. Use 1 or 2 March Model 893 pumps pulling 1 amp each at 12 volts to circulate seawater and that is probably less than what the condenser fan pulls. I have been thinking more about that battery issue and due to the number of cycles needed for a full time cruiser it would be more economical to switch to lithium batteries. 2 8 packs of 100 Ah Thunder Sky batteries costing $2000 is probably what is required to run a 9,000 BTU AC system plus everything else on a typical boat.

[Eyeback]

Poor man's refrigeration; In my younger days we used to keep our beer cool on deck by placing a wet rag over the top of the container. The pressure of air blowing over the top would evaporate the water by taking the heat from the container. It was surprising how cool the container kept. I often wondered about trying to do the same thing on a cabin top. The missus probably wouldn't consider it aesthetically pleasing though.

[senormechanico]

Sail to a higher latitude?

[MarkJ]

I haven't followed this thread as we don't have a problem at all. we have 13 opening hatches including 7 forward facing being 3 forward and 3 in the main saloon. So if it gets hot and we are in the salloon we have the benifit of 7 forward opening and 2 side opening. the side opening and one forward opening are over the kitchen (Thats the Galley to the salty folks with dorades ).

We have 1 dorade witch is useless and not necessary and I would throw it overboard if I could get the damn thing off.


So, to me, the main thing about keeping a cabin cool is the original design of the boat.


In the tropical wet seasons we have a small tarp we put over the forward 2 forward opening hatches so we get air but no rain


Mark

[hummingway]

Originally Posted by Eyeback

Poor man's refrigeration; In my younger days we used to keep our beer cool on deck by placing a wet rag over the top of the container. The pressure of air blowing over the top would evaporate the water by taking the heat from the container. It was surprising how cool the container kept. I often wondered about trying to do the same thing on a cabin top. The missus probably wouldn't consider it aesthetically pleasing though.

Swamp cooler! It's a classic but not very effective in humid locations. In arid locations though it makes a low cost air conditioner. Is it possible to be low humidity and afloat at the same time

[Southbound]

Originally Posted by avnbuff

Cooling any boat seems to require a lot of energy. Most of the 'big' boats are satisfied with the $2000 or $4000 units that keep a part of the cabin cool.

This involves pumping lots of water and running a compressor.

The first part of this, the water may hold a secret to getting a cabin cooler. Most of the better refrigeration units pump water around the newly compressed freon to provide a more efficient unit.

The water temperature at depth could be in the 70's even on a really hot Florida day. So, if you are not sailing, what about pulling some up to the cabin area to do a heat exchanger process and cool down the area?

I actually bought the biggest Heater core (from a vehicle) I could find, plumbed a small pump in line to a (strained) thru-hull to the inlet. the outlet to an above water thru-hull outlet. built a box out of plywood with a 3" hole for a blower fixture, placed the contraption in part of a locker that wasn't being used, cut a hole in the face of the locker for a register grill and presto... interior cooling. I think it cost maybe $150.00 after I weeded thru my scrap pile.

This set-up may not work down in the gulf, but up here in the Pac NW on a 95 deg day its probably 10 to 15 deg cooler. I know our water temps never get much above the low 60's.

[Wavewacker]

I feel negligent not saying thanks earlier, I lost the thread and found out how to search for posts...anyway....

That was my idea, to use a radiator and a hose to drop over. I was thinking that a small efficient pump with a closed system (no need for filters, etc.). The water or liquid in the tubes would be cooled by the lower water temps, come into the cabin to another radiator with a small fan behind it. I think the pump would need to operate at a volume so as not to allow the fluid to change temps on the way up. In many places, 20' can make a big difference.

I believe there are other liquids that hold temp changes better than water, like those oil filled radiator heaters, perhaps that would be a better conductor....I don't know.

[zeehag]

here in mazatlan, where the ambient temp of the water under the keel is essentially same as air temp, i believe one will find a cheapo window unit air conditioner will do the trick. if you are in a marina for a minuet, it does very nicely.
at anchor,i never had a problem with air flow, and i use tarping over the house so is a lot cooler than having sun beat the dickens out of my coach house roof...
.i went from interior temp oif 111F on a 85F degree day to an interior temp of 78-85F. also removed 20 percent humidity from my air inside, making the interior actually liveable in summer in pair a dice.
btw-- the measured temp of the water in the pacific ocean here was 31C, which is close to 88-90 degrees F

[hellosailor]

zeehag-
"where the ambient temp of the water under the keel is essentially same as air temp,"
Keel, maybe, but how deep is the thermocline? Often somewhere between 10-40' down with a good thermal drop. Not so by you?

[zeehag]

this is considered tropical waters. it doesnt get cooler by much at all. hurrycames form here. one can bathe comfortably in this stuff.
my keel is 6'6 deep and still hotter than mommas buttered rolls from the oven.
trust me on this-- the folks with water cooled boats even get window units for hatches.

[Rakuflames]

Originally Posted by Wavewacker

I feel negligent not saying thanks earlier, I lost the thread and found out how to search for posts...anyway....

That was my idea, to use a radiator and a hose to drop over. I was thinking that a small efficient pump with a closed system (no need for filters, etc.). The water or liquid in the tubes would be cooled by the lower water temps, come into the cabin to another radiator with a small fan behind it. I think the pump would need to operate at a volume so as not to allow the fluid to change temps on the way up. In many places, 20' can make a big difference.

I believe there are other liquids that hold temp changes better than water, like those oil filled radiator heaters, perhaps that would be a better conductor....I don't know.

That wouldn't work in Florida, where most of the day the water may be warmer than the air. I have a neighbor working on using Peltier technology to make a hatch cooling system that would not be an air conditioner per se and that could be solar powered.

This is the kind of coolant system used in those coolers you plug in. They can drop the temp to 40 degrees below the air around it.