holy grail solar air conditioning unit that isnt powered by honda generators and is

Like Submarine Tom says, it's all about delta t.

A bit of math proves AC by pumping up seawater doesn't work, but some guys can be pretty stubborn.
I spent my honeymoon in a luxury seaside hotel in North Africa. A local mastermind had designed and built the ultimate AC system for areas with an unreliable power grid: the inverted central heating. Cast iron radiators and large diameter pipes were installed against the ceiling of the dining rooms, fed by a diesel powered pump in a separate little building on the beach. The original plans to pump up seawater were than already abandoned because the water temperature in summer was over 30 C., so they had an array of pipes as a heat exchanger on the seabed, but that also didn't work.

When I was there, almost half a century ago, they just had a new system installed: absorption of ammonia to cool the circulating water to increase delta t. Another separate building, but much larger because of the size of the heat exchanger, with lots of pumps, valves and pipes.

The dining room still was uncomfortably hot. They opened all windows to get the sea breeze in, but that of course was also 30 C.
Like I said, some guys can be pretty stubborn.

 

In My parts of the world (Norway is divided by the artic circle) a Water-hose system would probably be far more effective. Surface sea temp is rarely above 21-22 degrees C in sheltered fjords, and significantly lower temperatures exist just a few meters down. In the north of Norway seatemp doesent get much over 10 deg C at all.

This of course mens that the requirement of such a system is far easier and cheaper. Airtemp is high in the summer even in the North, but humidity is often low to moderate.

Since I do most of my boating in kayaks and canoes my watercooling is fully automated and to some degree subject to the moodswings of weathergods

regards,
Padilac

edit:typo

 

Not sure if this was aimed in my direction, and whether I'm the one being stubborn, or not.............

I'm not proposing that sea water cooling ON ITS OWN can do the job in extreme conditions, just that a staged system, that uses sea water to cool really hot surfaces down first, using pumped sea water, reduces the heat load that any subsequent cooling system to deal with. The idea of using pumped sea water is a simple one, that requires a minimum of equipment or added weight and should be pretty reliable if powered by a small solar panel and pump.

The next stage, getting the cabin air temperature down from 30 deg C + to maybe 25 deg C would need active cooling with a heat pump, but this could, perhaps, be an absorption unit, maybe directly solar powered, with just a fan to distribute cool air from the evaporator heat exchanger.

 

That makes sense. I do a similar thing when driving my car in the summer. I choose the windshield ventilation mode and orient all the grilles towards glasses, both frontal and lateral. In that way the air "washes away" the heat (mostly radiant) from the surfaces and the sensation is much better than having the cold airflow directed towards myself and the passengers.

I have applied the same strategy for some residential AC projects and the result, in terms of comfort, was very good. Walls and glasses exposed to the sun can get very warm, making it uncomfortable to sit near to them, even if the room air temperature is low. So I want to reduce the surface temperature, the air temperature in this scheme becomes of secondary importance. This concept is not new, it is widely used in HVAC engineering and is measured through Mean Radiant Temperaure (http://en.wikipedia.org/wiki/Mean_radiant_temperature), which is a far more important variable for human comfort than just the air temperature.

Cheers

 

Mount this on the bow but don't trip on it. Now your boat has become a water theme park!

http://www.google.com/products/cata...=X&ei=cxhfT-vhCuHv0gHk14S0Bw&ved=0CLsBEPMCMAM

 

Curiously we did this as an experiment back in the 1980's to reduce the IR signature of warships. We used atomising spray heads, as used for pesticide spraying, and pumped seawater through them. They were arranged to produce a very fine spray of water over the whole ship, cooling it down so that it was closer to sea temperature and less visible to IR seeking missiles or detection systems. Cooling was effective, as the fine spray evaporated quickly, taking a lot of heat with it.

It worked well, but the corrosion problems were significant, particularly with all the deck-mounted equipment and the antennas. Salt build up on the latter was a particular problem. AFAIK it never got taken up as a practical solution because of these problems.

 

Prophylactic coatings would help there.

 

That's very interesting. do you remember what was the necessary waterflow to cover the whole ship? Could the desalinizers be used to provide the fresh water for the spray heads, or was the water consumption too big?

 

Sounds like a classic case of dissimilar metals of fastenings etc, i.e. poor detailing. It is a boat, in the ocean, with sea spray, blown all over it all day long after all! I can't image the corrosion to be any worse than from normal sea spray..unless of course the fastenings were very poor and only highlighted by such an experiment...which again would seem odd.

 

Most GRP boats will be solid glass below the water line.

The huge area of bilge will do grand cooling , all you have to do is pull the warmer air out , and the hull will fill with the cooler bilge air.

Yes ,,,it will take a good scrub for many boats to get the bilge sweet enough to enjoy its cool air .

Sometimes simply setting ports will cause the heat to leave.

The cooling down to water temperature can sometimes be 10 or 15deg but you will ONLY notice it by shading the deck, a 100F- 130F deck will overcome the cool air.

FF

 

I can't recall exactly how much water it used; for the experiment we just hooked the spray system up to the ships seawater pump outlets on deck. It was a proof of concept thing, to see if it would significantly reduce the ship's IR signature. One problem it didn't fix was the hot plume emissions from the engines, which ended up being a bigger IR target than the ship, IIRC, so making the exercise of limited practical use. I don't believe is used much water. The spray heads were the spinning disc ones used on farm spray equipment, and produced a very fine mist.

 

Yes, but this was a warship, where weight savings meant that the topsides were aluminium alloy, on a steel hull and with a mix of metals on all the necessary deck fittings (guns, torpedo launchers, radar and radio antennas, etc). Although the dissimilar metal problems wre dealt with as best they could, there were inevitable compromises that relied on things like coating areas with grease or lanolin regularly (which also gave the sailors something to do, I guess!).

 

No it wasn't Jeremy! It was just anecdotal.

The idea to cool hot surfaces with seawater is a very good one, in midsummer I cannot walk on the deck without shoes.

I read about a project using residual heat for air conditioning, involving hydrocarbons with a low boiling point. The heat source can be solar, warm water or warm air, there is little or no electricity involved. As far as I know, it is only used in large plants, probably because the energy density is too low for small scale use.

 

How about reversing hydronic radiant flooring. Run sea water through tubing matrix imbedded in the structure to pull the heat and reduce to ambient water temperature.

 

Thanks!

The AC system you describe sounds like an absorption cycle cooler. These used to be quite common in silent and gas powered refrigerators, like those used in RVs. The working fluid used to be ammonia in the old ones I remember, but I'd guess there must be some better/safer fluids around now.

The principle is that you heat up the fluid, it turns into a vapour, the vapour condenses in the evaporator, taking heat out of the environment around it, then passes to a condenser mounted somewhere cool, where the extracted heat is given up and the fluid recycled (by absorption and thermo syphon action) back to the heating element. There's a reasonable description of the working cycle here: http://en.wikipedia.org/wiki/Absorption_refrigeration

As a cooling system it's not very efficient, which is why, in these energy-concious days we've largely switched to compressor driven cooling systems. It does have the big benefit of having no moving parts, plus it works on solar heating (with a concentrator of some sort) which makes it a viable option for a fairly simple cooling system, I believe.