The Ultimate Refrigeration System?

[downunder]

Originally Posted by SURV69

I say if you can forget about needing a freezer and only need to keep things cool, go Peltier . . . simplicity in the making.

The unit takes virtually no space, is very small(the Peltier), and only a small fan to move air off the hot side.

You can take everything you need in a McDonalds bag to completely replace the system 2 or 3 times.

Granted things don't get icy cold, but unless you need icy cold.....

I run mine mainly at night, when the sun's down and my nicely insulated cooler keeps everything cold through the day. I like my milk cold and the Peltier delivers milk cold enough that I can't gulp it. In fact a few years ago I froze some 1% milk on a rather hot day in June because of the overnight running. It was rock hard(like a brick), and I had to throw it out.

About 4-5 amps an hour, but like I said, I only run it at night for about 5-6 hours and maybe during the day for an hour or two. On average it comes to about 1.5 amps per hour on a 24-hour basis . . . 36-40 amps a day when I need it.

Aside from some terracotta jars, sand and wet rags, the Peltier is absolutely simple.

Wait til your somewhere when you $1000 Engle goes on the blink. When mine goes on the blink, I have 1/2 hour work to replace about $10 worth of parts.

CAELESTIS was seeking advise on the ultimate system. Sounds as if he will be cruising/living long term in tropical areas.

Doubt a Peltier could be given a moments thought as a consideration of his ultimate system. Richard Kolemans book sounds a good starting point.

[Cheechako]

Originally Posted by Richard Kollmann

Cheechako, maybe you misunderstood the question “If you were to completely redesign your vessel's refrigeration system using 12v or 24v for power, what components would you choose? The goals would be efficiency, and durability for long term cruising.”

Long term cruising to me means possible cruising in warm tropical climates so equipment selected should be designed for worst case climate conditions 90 degrees seawater and 90 degrees ambient air temperatures while maintaining desired box temperatures. If your boat is not in tropical waters subtract 2% from energy estimate for each degree of cooler seawater. You can apply the same 2% per degree if you increase box temperatures above my desired ultimate box temperatures. A box refrigerated as a drink cooler off the North West coast of Washington may need only 3 amps per cu ft per day.

I understood the question, just wondering about the: "are you saying 10 amps an hour for one cubic foot..? (P=IV) Or 10 amps per day? "
In the carribean I estimated my daily refrig comsumption at roughtly 80-90 amps per day.... less than a 2 cu ft box with nothing special insualtion of maybe 3" or so. Just asking, are you sayiig a modern built box and unit will only require 10 amps perday per cu ft... or?

[s/v Jedi]

Instead of trying to guess the energy requirements, let's just list some key points about it;

I read that somebody came up with Glacier Bay?! Man, I still remember the day that I sold my system as one of the happiest days of my life.

- Danfoss compressor based

- Keel coolers unless not in living quarters where air cooled is an option, but never water cooled with a pump and hoses etc.

- Tropics rated box so 6" foam in case of a freezer or 4" in case of a fridge. When better materials are used this can go thinner to end with the same total R-value

- Electronic thermostat (Carel) so that a box can be changed from fridge to freezer by adjusting the thermostat instead of swapping it

- Good strong fiberglass finished and painted inner box for hygiene, easy cleaning etc.

- No drain, use Drydeck panels and sponge to get water out

that's what I can come up with now

[Delfin]

When I built mine, I used Nanopore vacuum panels that have 4 times the R value per inch of Aerogel. They aren't cheap, but a Danfoss BD50 freezes 8 cu ft to 0 degrees with minimal draw. I also added 1" of polystyrene just for laughs, but it probably isn't doing much.

One key that seems to be overlooked in many installations is locating the Danfos (if that is what you use) where it is kept cool. If they are not, you will see much higher energy draws.

Nanopore

[CarinaPDX]

I would have to agree with Jedi (OK, it happens sometimes!). I had a keel cooler made and it works very well. I also put a radiator in the system so it would work out of the water, but I don't think I would do that again. The Danfoss BD35F (or possibly the larger BD50F) is literally the only way to go; it is reliable and easy to find replacements worldwide.

Factory conversions typically come precharged with quick connectors for assembly. This is not always reliable as a small bit of dirt can interfere with the seal and allow the gas to escape slowly. There is a new, single use, connector I believe but I have no knowledge of it. If you want reliable then you want a properly soldered copper tubing. This means getting someone to start with parts and assemble in the best case.

The Danfoss compressors, evaporators, and tubing come in metric sizes in Europe but usually Imperial in the US. So pay attention to compatibility. There are several controllers available (for 12VDC, 120VAC/230VAC, or both) and they are usually included with the compressor. It is relatively easy to find these controllers as well. Some of the fancier aftermarket controllers plug in as a replacement.

The Carel thermostat is an amazing piece of gear. It comes in many models, and with the right one it can use two temperature probes (freezer, refrigerator) and control the compressor (for freezing) and the fan (for cooling the fridge section). It can be found in 12VDC, but do note: it does draw some electricity full time. The old passive thermostat works pretty well...

It is quite possible to buy the parts from rparts.com and make your own system if you are handy and do the necessary research for the design. The gas, gauges, and vacuum pump are inexpensive at Harbor Freight. But I would recommend paying for a pro...

Greg

[SURV69]

I use a coleman peltier cooler.

In Ohio we get mostly high 70's and into 90's.

When the temps are n the 90's drinks(Gatoraid and milk), are cold . . . not quite icy cold.

In the upper 70's everything is cold. The milk through to about noon is as cold as I can drink it and 3 or 4 pm is still cold.

I generally open the unit most often during the night, cause I'm working on projects during the day . . . I generally forget to eat and spend time snacking on Oranges, Apples and drinking water or Gatoraid from the cooler. The cooler never gets opened to get "some" water or "some" Gatoraid. When I get he water Gatoraid or pop, I get a one or 2 liter out and drink the whole thing.

I'm thinking of making a super insulated box with a peltier, a small fan and a water drip to disperse the heat from the hot side. The water will come from the lake and is about 70-75 degrees n the summer.

I'm not sure how a peltier would work in subtropic or tropic where evening temperatures don't fall much or where water temperatures are generally higher, but for northern Ohio in the heat of the summer, this unit works great and in a 24 hour period doesn't use very much energy at all . . . on average, about 1.5 amps per hour on 24 hours . . . 36 amps, 450 watts or about 630 watts off the solar panel(amps time 17 volts).

With LED everything, alcohol stove, kerosene lamps, a small highly energy efficient radio/mp3 player, a 3"(now being upgraded to 1 7" TV, which I seldom watch), and my VHF, I really don't think that 600 watts a day is a big issue and won't be a big issue when I add 200-300 watt in panels. Gee . . . even the LED's only get used from about 9pm to about 10:30 or so.

I might even add a wind generator, but if I do, I'll make it myself and it will be one with rotates on the vertical.

Whatever the case might be, for me the peltier works, I'll never spend an arm & leg to get it fixed and I'll never spend a week waiting for parts.

[Boatguy30]

I'd say Richard is right on with the 10 amp hrs per cubic foot of refrigerated space. Double that for freezing. Actually both systems I've built used a bit less than this. Use the blue foam insulation 4-6" more in the bottom if you have space.

[Delfin]

Originally Posted by Boatguy30

I'd say Richard is right on with the 10 amp hrs per cubic foot of refrigerated space. Double that for freezing. Actually both systems I've built used a bit less than this. Use the blue foam insulation 4-6" more in the bottom if you have space.

The amount of energy required to keep something cold is a function of the insulation that prevents heat loss. Prevent heat loss and you can keep things frozen with 1 watt per month, or no watts per month. Asking how much energy is "required on average" is like asking how long a piece of string is. Increase the insulation and decrease the heat loss as well as the energy consumption. If space is not a problem, then by all means, line the box with 6", 12", 24" of insulation board. If it is, then use something designed for refrigeration. Like vacuum panels which have a R value THIRTEEN times blue board per inch.

[s/v Jedi]

Originally Posted by Delfin

The amount of energy required to keep something cold is a function of the insulation that prevents heat loss. Prevent heat loss and you can keep things frozen with 1 watt per month, or no watts per month. Asking how much energy is "required on average" is like asking how long a piece of string is. Increase the insulation and decrease the heat loss as well as the energy consumption. If space is not a problem, then by all means, line the box with 6", 12", 24" of insulation board. If it is, then use something designed for refrigeration. Like vacuum panels which have a R value THIRTEEN times blue board per inch.

Hey, Delfin is using science and logic Always nice to find that I'm not the only geek engineer left, although most of all this is plain high-school material...

[Cheechako]

I installed the metal vacuum panels on the small box in my Passport . Engine run time to keep up with the fridge didnt change any discernable amount... huh? Yeah , I dont get it either.
I know Richard is the expert and knows a helluva lot more than me, but if you guys are saying 240 amps a day.... I'll stick with the old rusty cold machine and 2-3" of bad foam insulation at less than a 100 amps per day in the tropics......

[Cotemar]

Originally Posted by Cheechako

I installed the metal vacuum panels on the small box in my Passport . Engine run time to keep up with the fridge didnt change any discernable amount... huh? Yeah , I dont get it either.
I know Richard is the expert and knows a helluva lot more than me, but if you guys are saying 240 amps a day.... I'll stick with the old rusty cold machine and 2-3" of bad foam insulation at less than a 100 amps per day in the tropics......

That's the problem with the vacuum panels. They leak over time loosing their insulation abilities.

Polyisocyanurate foam or Aerogel insulation is the way to go.