Cold Plate / Thermoelectric?

[motion30]

Originally Posted by wolfenzee

Well for something like that to work I would have to get a very water tight box (probably fiberglass), weight it with lead (to compensate for the air space at least 100lbs of lead)....lead and fiberglass are not very green. Then instead of grabbing some food out of the fridge on a cold winter night I would have to go topside in the rain and/or snow, winch up the box, wipe off the slime, mud and assorted critters that had accumulated on it......it was bad enough just getting stuff out of a cooler in my cockpit covered by an awning.
As far as green.....the fridge I am getting uses very little power and am looking into wind and solar for my boat.

I have this exact setup you describe This uses much more power then you think, when running of my inverter the reaout from the inverter states the input is 9amps. You can do a search on the forum as it was covered in another thread several weeks ago, I am searching for a 12volt unit

[Jace]

Well, Wolfenzee, not to be too challenging, but if it's snowing out, obviously you don't need the ocean depths to keep stuff cold ... simply set it on deck.

As far as weighting it, 100 pounds of lead would be way too much. I was thinking more of liquids - sixpack of beer, gallon of milk, double liter bottles of coke, etc. Those are so dense that you could pack them down in a nylon bag with maybe ten or at the most, fifteen pounds of weight. You could even control the buoyancy, thus customizing the resistance of raising the load. And I wouldn't be leaving it down there for more than a few hours, most likely. I'd have a coke probably every few hours, or at least once a day. I'm not saying it's ideal, just workable. If it's cold at night, you could pull the pack up and leave it on deck till morning, then drop it back down again. I just don't know how deep you'd have to go to get what particular temperature, in what particular area.

However, LakeSuperior made a point I hadn't thought of - the pressure! Duh *slaps forehead* Well, I said I was green, forgot to mention that I was an idiot, sorry.

[LakeSuperior]

From a technical perspective...an "average" value can hide many sins. The specific summer I was referring to the surface water temperature across the open waters of Lake Superior was in the mid to upper 60's. Below the thermocline the water was still in the upper 40's. The bier we lost in the above mentioned incident was fine Canadian Labatt, best served well chilled in the summer.

[wolfenzee]

I am trying to make a very pleasant galley...I am not trying to see how I can inconvenience myself. One of the live aboards said "If I could have one thing from land I would have a freezer". I have space for a refrigerator/freezer and it is relatively inexpensive, I am building my galley in such a way so I can eventually replace the 110v fridge with a 12v system. I lived on this boat for 2 years with only a cooler in the cockpit which I barely every bought ice for. I am useually conected to shore power and when I am not I have enough power in my 8D to last awhile, the fridge I am looking at draws 1 amp AC, but not constantly....the loss from an inverter varies tremendously depending all sorts of variables (30%-70% load is the most effieciant and with electric motors pure sine waves are 20% more effiecient....too big an inverter wastes power, etc...)

[GordMay]

Originally Posted by LakeSuperior

From a technical perspective...an "average" value can hide many sins...

The links I previously provided were for Superior SURFACE Temperatures on Agust 20/09. I don’t recall ever seeing Superior surface temperatures in the upper 60's, except in “enclosed” rock-pools.
Notwithstanding, I take your point.
I too, have cooled beer (Labatt's "Crystal") in the lake; usually just below the surface, on the shady side of the boat.

[SURV69]

I presently live at 5-6 kwatts a day(summer/winter) . . . at home(not the boat).

When I bought my Coleman Pelzier cooler I never checked the wattage useage. Since the instructions said not to run it on a car battery for more than 4 hours without turning on the engine . . . and what the heck it seems to run almost nothing more than a small fan.

Given that a car battery is a "starting" battery, which is not made for or forgiving after a sustained power draw, I "assumed"(you know what they say about "assume"), that the power draw was indeed very low. Evidently I was wrong on three counts . . . the power draw, the lack of insulation and the need to manually control the operating hours in order to maintain a worthwhile temperature. I plead guilty to ignorance of all three.

To a fourth, I do not plead guilty. This being that the pelzier unit has been "reliable" for what it claims to deliver.

I have gone through a couple of small refrigerators(on the boat) through last year that have leaked their refrigerant or otherwise ceased working. There's nothing worse than carefully shopping for, buying, traveling a number of miles, placing it on the boat(after finding a suitable place), dogging it so one can still sail, placing frozen fun-stuff in it(like the icecream bars), watching it fail, watching the icecream soften(and the meat ripen), undogging and removing the unit, taking it back to the store(once on a motorcycle), signing return documents, getting another(putting it on my motorcyle) and repeating the entire process through the next return.

ADD to this the fact that I generally hate stores and hate shopping.

The pelzier unit has been a God-send, because it appears to operate consistently and keeps thing cool enough to satisfy me . . . abiet, it uses more energy(than I imagined) and needs to run more often because of the very poor insulation.

Nonetheless, I think you guys have made me realize the error of my ways and on my next boat upgrade, a more energy-efficient(and hopefully reliable) small fridge will be in order. BUT NOT ONE OF THOSE $1000 UNITS.

Now to ask an energy question.

Is 0.6 amp (per hour) draw at 120 volts(AC) EXACTLY the same as 6 amp draw at 12 volts(DC)? AND . . . coincidently are 12 volt appliances(DC) generally more energy efficient than similar 120 volt(AC) appliances?

[GordMay]

Yes - Peltier Coolers are highly reliable power hogs.

The Cooling Fan is only one component of a Peltier Coller’s power consumption. Peltier coolers consist of the Peltier element/junction (TEC) itself, and a powerful heatsink/fan combination to cool the TEC.

Peltier elements (Thermo-Electric Cooler, or TEC) have very low efficiency*, and consume more power than they transport. Actual Peltier elements may consume twice as much energy (in the form of electricity) as they transport (in the form of heat). Do not confuse the maximum amount of power a Peltier element can transport with the maximum amount of power usage of the Peltier element.

* TEC junctions are generally only around 5–10% as efficient as the ideal refrigerator (Carnot cycle), compared with 40–60% achieved by conventional compression cycle systems (reverse Rankine systems like a compressor).

Peltier Coolers allow cooling below ambient temperature, but unlike other cooling systems that allow this (vapour phase refrigeration), they are less expensive and more compact. Peltier elements are solid-state devices with no moving parts; they are extremely reliable and do not require any maintenance.

[motion30]

Originally Posted by SURV69

I presently live at 5-6 kwatts a day(summer/winter) . . . at home(not the boat).

When I bought my Coleman Pelzier cooler I never checked the wattage useage. Since the instructions said not to run it on a car battery for more than 4 hours without turning on the engine . . . and what the heck it seems to run almost nothing more than a small fan.

Given that a car battery is a "starting" battery, which is not made for or forgiving after a sustained power draw, I "assumed"(you know what they say about "assume"), that the power draw was indeed very low. Evidently I was wrong on three counts . . . the power draw, the lack of insulation and the need to manually control the operating hours in order to maintain a worthwhile temperature. I plead guilty to ignorance of all three.



To a fourth, I do not plead guilty. This being that the pelzier unit has been "reliable" for what it claims to deliver.

I have gone through a couple of small refrigerators(on the boat) through last year that have leaked their refrigerant or otherwise ceased working. There's nothing worse than carefully shopping for, buying, traveling a number of miles, placing it on the boat(after finding a suitable place), dogging it so one can still sail, placing frozen fun-stuff in it(like the icecream bars), watching it fail, watching the icecream soften(and the meat ripen), undogging and removing the unit, taking it back to the store(once on a motorcycle), signing return documents, getting another(putting it on my motorcyle) and repeating the entire process through the next return.

ADD to this the fact that I generally hate stores and hate shopping.

The pelzier unit has been a God-send, because it appears to operate consistently and keeps thing cool enough to satisfy me . . . abiet, it uses more energy(than I imagined) and needs to run more often because of the very poor insulation.

Nonetheless, I think you guys have made me realize the error of my ways and on my next boat upgrade, a more energy-efficient(and hopefully reliable) small fridge will be in order. BUT NOT ONE OF THOSE $1000 UNITS.

Now to ask an energy question.

Is 0.6 amp (per hour) draw at 120 volts(AC) EXACTLY the same as 6 amp draw at 12 volts(DC)? AND . . . coincidently are 12 volt appliances(DC) generally more energy efficient than similar 120 volt(AC) appliances?

You need to factor the loss tru the inverter, something on the order of 15% or so. I believe that is the difference between 12 v and 110v

[wolfenzee]

A neighboring live aboard used to have a 40quart Coleman 12v cooler, it used 4amp constantly, not on and off. He had two of them, wore out one and got another. Now he has a 12v compressor powered about 1.7 cf fridge with freezer (big enough for a couple of ice trays) and it uses less power overall.

[exranger]

wolfenzee, are you saying that you can run that 110v Walmart fridge for days on one 8D?? I don't think it qould last a day if you ran it totally down. It's gotta take 10-15 amps 12v an hour, converted to 110v, unless I am misisng something???

[marujo.sortudo]

Well, if you were REALLY cheap, and could find a shady, breezy place to put some ceramic pots on your boat (I know, I know) ... you could use a solution that's over 2000 years old:

Practical Action - How a zeer pot fridge makes food last longer

These work best in low humidity, require water (not sure if salt water is ok), and are easily broken. They like a breeze and benefit from a clear line of sight to the night sky. That said, in optimal conditions (the desert), they can get 90 degrees below ambient and even make a tiny bit of ice.

On the plus side, they draw zero amps. FYI, no I haven't tried this, but I read about it, so it must be true.