Using Seawater to cool Cabin

[DallasAB]

Hello, I'm *REALLY* new to sailing and have just been spending a lot of time learning the ropes and etc. I've read a lot about power consumption and Air Conditioning and have come to the conclusion that solar power with current technology would simply not be feasible. However, what about using cool seawater pumped through a radiator with a fan attachment? A small diaphram pump uses very little power and a fan doesn't use much either. Am I nuts??

[wildcard]

Sea water is just not that cool where you would need AC. Maybe anchored up with a draft tube 10-12 feet down where the water cools a little? Underway, I dont see it working real well. Fans and shade usualy suffice.

[ebs001]

There was a company that sold just such a unit. They used to advertise regularly in sailing mags and I had their website at one time, but they seem to have fallen off the map. From their statistics it seemed to work but I think it may have required water from 20ft or so which is a little deep for anchoring. I did a quick google search and I can't find anything about them. I unfortunately cannot remember their name.

[Valiente]

Your idea is more suitable for heat, as in piping water from the block into a car's heater core, which is blown from a fan and into the cabin. The water then proceeds back to the mixing elbow. That's a cheap way to capture otherwise wasted heat energy, and is the same idea as a heat exchanger plumbed into a hot water tank.

A marine air conditioner (I have a Marine Air 12,000 BTU condenser/heat pump unit) can take sea water of most temperatures and use electricity to either provide cool air or warm. I've used mine at dock with great success, but with a 10 amp draw on AC power, I wouldn't use it through an inverter unless someone was dying of heatstroke. If it wasn't already installed, I wouldn't have all that conduit through the boat either, but I'm OK for space and it is a blessing at dock. Offshore, we will use a diesel heater and dorades/windscoops for heating and cooling.

For smaller boats, it's either not feasible due to the space, or due to the fact it can't be easily run once off a dock. Books like "The Warm Dry Boat" go into this stuff extensively, and how critical airflow (both passive and active) is to a comfortable, mildew-free boat.

[Freesail99]

There is a unit invented by a New Jersey boater that uses a cooler filled with ice and fans to cool. I can not remember the name.

[Sailormann]

A small diaphram pump uses very little power and a fan doesn't use much either. Am I nuts??

You would need to have a VERY small boat..

[yotphix]

A chilled water loop a/c cools the water to about 35-45 degrees farenheit to keep your boat cool. When it is hot enough to need and a/c, water surface temps get up into the 70's,80's or more. You likely wouldn't get much from it unless, as suggested, you draw from deep water.

[wind_magic]

I think it might help, but I have no evidence to back it up. The water is cooler than the surrounding air even in the tropics where the water is pretty warm. I'm sure if it was easy to implement and really effective that there would be a system out there taking advantage of it.

My own experience in the tropics is that I am pretty much ok so long as I have a fan blowing on me when I am sleeping. That does use a lot of water. Most people think of sweat as something that cools them off, and blowing a fan across you when you are sleeping does that very thing, but sweat also keeps your skin at it's preferred level of humidity by making a thin layer of moist air next to your skin. Sleeping in front of a fan blows that moist air away and you wake up really thirsty because your body has gone into overdrive trying to replace that moist air all night long, so sleeping in front of a fan isn't that great of an idea if you are trying to save water. That is the big reason that desert people are wrapped in thin loose fitting white clothing in multiple layers instead of walking around in bikini's or shorts in the dry desert air, water conservation.

[USCGRET1990]

The rule of thumb in a/c, is you need a minimum of a 12-20 degree temp. difference to affect any cooling. ie, 70-78 degree cooling medium can maintain 90 deg. (depending on the heat load and several other factors).

[Hubec]

It won't work in tropical/gulf stream regions. Well it will work, it just won't make a difference. There just isn't enough of a temperature differential for it to make the cabin appreciably cooler. By the time you're pumping enough water up and blowing enough air through to feel you'd be consuming more energy than just using a standard AC unit.

HOWEVER one idea that would definitely work to efficiently cool the boat is a mister system. Just setup a small sprayer at the bow while at anchor and the whole boat should see a significant temperature drop. Of course the downsides are evident; the outside of the boat will be wet all day (maybe not a bad thing on a SCORCHING day), and most importantly the system would only work in fresh water. I have seen big power yachts with similar systems installed in their aft lounge/swim areas.