Fridge that uses little, if any, of your battery!

[Off Trail]

Originally Posted by Richard Kollmann

A current survey would be interesting of what wattage size solar panels are you using to support 50% of your refrigeration electrical power needs, per cubic foot (28 liters) box per day.

Yeah, speaking for myself that would be hard to answer since I haven't really measured our boxes, and the solar power is used for more than the fridge and freezer (watermaker is probably the next biggest load).

But thinking about it, maybe the point is independent of solar size. Lithium provides the ability to "time shift" energy from daytime to nighttime in a very similar way to a eutectic system. So maybe it doesn't matter whether the power comes from solar or alternator.

It's really the conversion efficiency that matters. And while LFP probably doesn't have the same heat transfer efficiency as the eutectic system, its superiority to traditional lead acid is probably moving the advantage away from the eutectic system.

Dan

[Richard Kollmann]

Originally Posted by Off Trail

Yeah, speaking for myself that would be hard to answer since I haven't really measured our boxes, and the solar power is used for more than the fridge and freezer (watermaker is probably the next biggest load).

But thinking about it, maybe the point is independent of solar size. Lithium provides the ability to "time shift" energy from daytime to nighttime in a very similar way to a eutectic system. So maybe it doesn't matter whether the power comes from solar or alternator.

It's really the conversion efficiency that matters. And while LFP probably doesn't have the same heat transfer efficiency as the eutectic system, its superiority to traditional lead acid is probably moving the advantage away from the eutectic system.

Dan

Dan, if your refrigerator compressor is 12 volts then the amp/hrs it consumes will define its daily power consumption. If you are satisfied with your boats power grid the way it is then eutectic plate's disadvantages would far out weigh their advantage. It is true that refrigeration supported by lead acid batteries and engine alternators limited battery life from 3 to 5 years. Alternative energy from wind and solar is the best friend to blue-water live aboard sailors has.

[Pete7]

Originally Posted by Richard Kollmann

A current survey would be interesting of what wattage size solar panels are you using to support 50% of your refrigeration electrical power needs, per cubic foot (28 liters) box per day.

Tricky one that. If you have a shunt it's probably measuring all the house demands and charging sources. You would have to install a dedicated shunt just for the fridge or freezer, which I might yet, it still in the box. Whilst the fridge is minimal, the similar sized freezer warrants watching and monitoring closely as a power hog.

Ultimately, I hope to have all energy demands met from solar under normal conditions.

Pete

[Pegu Club]

Engel refrigerator, 12 volt, and it is very easy on our batteries, highly recommend them.

Fair winds,

[Boatguy30]

Yes, the mighty Engel. They are extremely small therefore have a relatively low 24/hr consumption. It’s very easy to build a SYSTEM with a 2-3x box that will consume a comparable amount of energy as the 1.25” of insulation an Engel has is totally inadequate if actual efficiency is your goal.

[OzeLouie]

Richard:
My reason now for asking questions is why there is only two or companies offering eutectic plates for what may have been twelve in the US. Richard, this statement is incorrect!
Maybe the eutectic plate industry realized small DC compressors do not offer adequate surplus plate latent energy. Richard, this statement is incorrect, most marine refrigeration brands offer a eutectic option! There are seven brands available in Oz and no doubt more in the US! Our production has increased four fold since 2005, with the biggest increase being the past year, surprisingly!

Do you really believe Eutectic plates will reduce need created by refrigeration for large capacity batteries? Yes, read what is said in the OP. Eutectic systems also consume far less DC power to maintain cabinet temperature due to less daily start ups and operating at a far better COP rate. Batteries and engine alternators make up the basic power grid for most production boats. I am glad most boaters and Louie agrees alternative power generation is required to boost power grid, is a must with eutectic plates on refrigerated boxes over three cubic feet in warm climates. This thread is about providing and storing energy and energy stored in a eutectic tank has many advantages, including weight, superior ability to rapidly reduce the temperature warm product added, hold over and far more efficient use of power due to grossly superior COP and far less of those inefficient start ups per day [/QUOTE]

[Boatguy30]

Richard, wins this one. Only time a small compressor driving holding plates is when you have lots of solar and want to dink around with time delays or “smart” proprietary controls.

In the tropics the thing will still kick in for what 45 minutes or more at 2am and 5 am before the sun is up and you will be pumping BTU’s out thru that thermal insulating solution much slower than thru a thin plate. Probably need as much or more battery capacity in the tropics as my system that runs a Danfoss 35 @2000 rpm! approx 1/3 of the time in tropics.

Richard was of great help to me when I was introduced to him by the late Andy Wall in 2003. Glad is health is holding up so well!

But hey, yep they sell great at boat shows!
So does all name of other **** with clever marketing.

[Richard Kollmann]

Originally Posted by Boatguy30

Richard, wins this one. Only time a small compressor driving holding plates is when you have lots of solar and want to dink around with time delays or “smart” proprietary controls.

In the tropics the thing will still kick in for what 45 minutes or more at 2am and 5 am before the sun is up and you will be pumping BTU’s out thru that thermal insulating solution much slower than thru a thin plate. Probably need as much or more battery capacity in the tropics as my system that runs a Danfoss 35 @2000 rpm! approx 1/3 of the time in tropics.

Richard was of great help to me when I was introduced to him by the late Andy Wall in 2003. Glad is health is holding up so well!

But hey, yep they sell great at boat shows!

So does all name of other **** with clever marketing.

Thanks Boatguy, I was beginning to think boaters are believing that small 3.5 cc 12 volt compressors could produce Perpetual Btu energy from an imaginary device reducing battery energy capacity to freeze eutectic plates. No one can ignore the fact, it is the compressor’s surplus capacity that freezes the eutectic plate. Without an alternative source of energy eutectic plates are difficult to justify.
PS Cleaver marketing like compressor cycling wastes energy does sell if uninformed.

[sailorboy1]

Originally Posted by OzeLouie

Do you really believe Eutectic plates will reduce need created by refrigeration for large capacity batteries? [B]Yes, read what is said in the OP. Eutectic systems also consume far less DC power to maintain cabinet temperature due to less daily start ups and operating at a far better COP rate.

When i read someone making claims that violate the basic laws of thermodynamics I know it is a waste of time. When they continue to hold to twisting very minor things I know, at least hope, they aren't an engineer or have had basic engineering training. My experience as both an engineer and sales guy that normally means they work in marketing and is looking to fit a product into marketing to fools who believe claims written by other fools.

[Dsanduril]

I’m still struggling to see either the energy or cost efficiency when a commercially available, cyclic unit like this one is available for < $1000. 155l of usable volume (nearly twice the OP’s usable volume of 85l) at an energy usage of 93kWh/year (22Ah/day@12V). Even if test conditions don’t quite match I still don’t see the proposed eutectic solution coming any better than par on energy per volume, and I suspect cost is a bit more.

[sailorboy1]

U*A*delta T

If don't understand, well ....

[Richard Kollmann]

Originally Posted by sailorboy1

When i read someone making claims that violate the basic laws of thermodynamics I know it is a waste of time. When they continue to hold to twisting very minor things I know, at least hope, they aren't an engineer or have had basic engineering training. My experience as both an engineer and sales guy that normally means they work in marketing and is looking to fit a product into marketing to fools who believe claims written by other fools.

Sailorboy, having been Directer of mechanical, electrical and operation engineering for a Fortune 500 company for several years before I retired I understand you. If it was not for the open ideas disused here we would not have the creature comforts on or boats we have today,Yes the manufactures are watching.

Twenty five years ago the theory of fixed speed compressor cycling wasted daily refrigeration energy consumption went out the entry hatch. The change by Danfoss/Secop to variable speed which provides no value to eutectic evaporators revolutionized energy consumption of other type evaporators as much as fifty present less energy on small heat removing boxes. These adjustable variable speed compressors improve energy efficiency by better gas flow at less than top speed. Benefits of slower speed efficiency would not be smart with a eutectic plate evaporator as they must run while alternative energy is available..

[JBP]

Aside from the bickering about units, I'm missing the point of the OP. It boils down to "If you have abundant power but only for a few hours a day, an eutectic fridge might be a good idea." Well, OK. Eutectic fridges have been around for a long time. They are great for the appropriate situations, although expensive compared to other solutions.

[Dockhead]

Originally Posted by Richard Kollmann

. . . Twenty five years ago the theory of fixed speed compressor cycling wasted daily refrigeration energy consumption went out the entry hatch. The change by Danfoss/Secop to variable speed which provides no value to eutectic evaporators revolutionized energy consumption of other type evaporators as much as fifty present less energy on small heat removing boxes. These adjustable variable speed compressors improve energy efficiency by better gas flow at less than top speed. Benefits of slower speed efficiency would not be smart with a eutectic plate evaporator as they must run while alternative energy is available..

Why couldn't both technologies work together?

Storing cold when energy is abundant, in a nearly 100% efficient battery, seems like a decent idea to me. Then if you need cooling when energy is not abundant, you can take advantage of what you describe.

What am I missing?

[sailorboy1]

Its that making use of excess energy does not equal using less energy.

In fact using excess energy and using it to lower frig/freezer temp increases the heat transfer (lost energy) by increasing the delta temperature across the walls