The Worst pleasure boat refrigeration.

[S/V Adeline]

Originally Posted by Dennis.G

Likely not really answering your question, but two observations:
1) The 12v solid-state thermoelectric coolers (truck driver coolers) are simple but pretty much useless for any long-term refrigeration. Just do not get down to correct temperatures for keeping food fresh and don't see any that freeze.
2) The old-style open compressor coupled with a DC motor (either direct shaft coupling or belt drive) seem very robust, but efficiency wise can not compete with modern hermetic DC compressor systems.

When I was driving OTR my 12v solid-state thermoelectric always froze my milk...trick is keep it full/less air = colder temps. I would not recommend them for anything beyond weekend sailing as they do enjoy eating batteries.

[Richard Kollmann]

[QUOTE=nilespf;3086994]

Originally Posted by waterman46

It really isn't all about duty cycle.....


Thanks for the reply Waterman,
If I understand your point we agree there are many relevant items that affect the running DC of our systems. My hope is to compare using as few figure of merits as possible. I understand that DC will wander all over the place for any number of reasons. My fear is I'm operating way out on the bell curve indicating any number of possible problems. You have brought up a good point that GPS location should be considered.

The eutectic system sounds great but I don't know if a properly designed evap system will yield the same energy usage. If they both are the same then I still can consider the flywheel cooling effect during the night and put a price on that. If I have enough batteries to withstand evening drainage then it may become an issue of do I want to tear the boat apart to insulate the box (assuming the box is the problem). Currently I can get through the night only because I have 230 Ah of capacity.

Pn

An important fact to remember is all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor. No other component of refrigeration system creates energy especially a thin plate or eutectic plate evaporator. This means all energy provided to refrigerator's compressor comes from an electrical power source. The most energy efficient place to store energy for 12 volt refrigeration is in batteries. Neither the batteries or a eutectic plate can create energy. The best way to create and store energy is from an alternator or battery charging from alternative energy Solar, Wind and others secures of electrical power.

The old days of blaming excessive energy use do to compressor cycling no longer is true with variable speed high COP compressors.

It seams like Fake News is now a way of life these days

[nilespf]

[QUOTE=Richard Kollmann;3087068][QUOTE=nilespf;3086994]

An important fact to remember is all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor.....


Richard, just trying to get some data to determine what direction to go. Thanks for the comments.
I'm inclined to think my refrigerant system may be able to be tweaked but not with significant improvements. Short of tearing the boat apart to add 8" of additional insulation, I see no easy solution for significant improvements. The boat is in the chesapeak and literally every one I have talked to around here either suspects DC of around 50% or have measured them. What I don't have is actual AH usage. Everybody is happy as larks with no energy budget in mind.



Hopefully more data is out there.
Pn

[Q Xopa]

[QUOTE=Richard Kollmann;3087055]

Originally Posted by nilespf

An important fact to remember is all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor. No other component of refrigeration system creates energy especially a thin plate or eutectic plate evaporator. This means all energy provided to refrigerator's compressor comes from an electrical power source. The most energy efficient place to store energy for 12 volt refrigeration is in batteries. Neither the batteries or a eutectic plate can create energy. The best way to create and store energy is from an alternator or battery charging from alternative energy Solar, Wind and others secures of electrical power.

The old days of blaming excessive energy use do to compressor cycling no longer is true with variable speed high COP compressors.

It seams like Fake News is now a way of life these days

Hmm,

Can you explain this- " all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor" further please? I don't understand.

My understanding is that a compressor uses, in this case electric Amp hours, to Convert to mechanical movement (elec motor part). Then the actual Compressor converts mechanical energy to liquid, and or gas flow. Pressure is created by restriction to that flow. No 'energy is created' anywhere in the compressor. I could be wrong.

Also your comment about Solar charging the batteries. To me it does some of the time, ie until the batts are accepting less charge than Solar is outputting.

While there is still sunlight, there is 'excess' solar than just battery charging.

This can be used to power other loads directly. Like say chilling down Hold over plates. This can be used after dark to keep the fridge cool instead of spinning up the compressor using batt AHs.

Ok duty cycle and Compressor COP are a factor, but not what I understand Hold over plates advantage. Ie using otherwise wasted Solar, or engine alternator power later when they aren't being produced.

There is no mention of 'energy creation'. Its simply storing energy like batteries to 'average' power use to average power production.

Duty cycle, yes less start up surges sure, maybe a bit. Compressor COP, hmm, I assume they should be optimized for either system so should be very little in this.

[nilespf]

[QUOTE=Q Xopa;3087121]

Originally Posted by Richard Kollmann

Hmm,

Can you explain this- " all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor" further please? I don't understand........."


understanding is that a compressor uses, in this case electric Amp hours, to Convert to mechanical movement (elec motor part). Then the actual Compressor converts mechanical energy to liquid, and or gas flow. Pressure is created by restriction to that flow. No 'energy is created' anywhere in the compressor. I could be wrong.

Also your comment about Solar charging the batteries. To me it does some of the time, ie until the batts are accepting less charge than Solar is outputting.

While there is still sunlight, there is 'excess' solar than just battery charging.

This can be used to power other loads directly. Like say chilling down Hold over plates. This can be used after dark to keep the fridge cool instead of spinning up the compressor using batt AHs.

Ok duty cycle and Compressor COP are a factor, but not what I understand Hold over plates advantage. Ie using otherwise wasted Solar, or engine alternator power later when they aren't being produced.

There is no mention of 'energy creation'. Its simply storing energy like batteries to 'average' power use to average power production.

Duty cycle, yes less start up surges sure, maybe a bit. Compressor COP, hmm, I assume they should be optimized for either system so should be very little in this.

Q xopa Not sure if your comments were directed at me but I can comment on ..."all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor"
Since Work= Force X distance and the work performed is the act of compressing the refrigerant in preparation of a state change before entering the evap coil. I'm not aware of any scheme used in the recreational boating industry that can replace the compressor. If one desires to quantify the amount of work that has been accomplished by the compressor then we can then quantify the energy used by the compressor and actually determine the power consumed and amps used and so on and so on. I really do like the notion of using the flywheel effect of the eutectic systems to get me through the night but I have not been able to see any actual data for comparison. that's all I want, with the data I can determine if tearing up my boat is really worth it. I'm using 57 plus AH now and I'm really concerned if it is as good as it gets.


Pn

[Q Xopa]

[QUOTE=nilespf;3087194]

Originally Posted by Q Xopa

Q xopa Not sure if your comments were directed at me but I can comment on ..."all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor"
Since Work= Force X distance and the work performed is the act of compressing the refrigerant in preparation of a state change before entering the evap coil. I'm not aware of any scheme used in the recreational boating industry that can replace the compressor. If one desires to quantify the amount of work that has been accomplished by the compressor then we can then quantify the energy used by the compressor and actually determine the power consumed and amps used and so on and so on. I really do like the notion of using the flywheel effect of the eutectic systems to get me through the night but I have not been able to see any actual data for comparison. that's all I want, with the data I can determine if tearing up my boat is really worth it. I'm using 57 plus AH now and I'm really concerned if it is as good as it gets.


Pn

Nope not directed at you.

But seeing you mention 'work' I agree with your definition but didnt see anyone mention it?

Compressors 'Creating energy' was the comment I was responding to.

[GILow]

[QUOTE=nilespf;3087194]

Originally Posted by Q Xopa

I'm using 57 plus AH now and I'm really concerned if it is as good as it gets.
Pn

I suspect you may be close to as good as it gets now, depending on a few variables. If we accept that most currently available refrigeration systems are at least similar in performance, I can say that my just-built, 230 litre fridge/freezer at 4 degrees C/-5 degrees C is using 50 AH in 30 degrees C ambient temperature (though it has been colder in the cabin these last few days). So a pretty similar power consumption for a newly (and carefully) built fridge system that is performing pretty much as the spreadsheet model predicted.

Of course, if your fridge box is significantly smaller, or if you only have a fridge not a freezer, then it suggests there is room for improvement, maybe in the compressor and associated equipment or, more likely, in the insulation.

And maybe somebody will chime in with better power consumption figures than mine and I’ll be thinking of making improvements.

Incidentally, I don’t think my 630 AH FLA battery bank Is all that large by today’s standards, but I do think I am lucky in having been able to install 760 Watts of solar cheaply and easily. As you can imagine, 50 AH against that sort of capacity is a trivial concern.

[Richard Kollmann]

[QUOTE=Q Xopa;3087121]

Originally Posted by Richard Kollmann

Hmm,

Can you explain this- " all energy for 12 volt refrigeration, regardless of what many believe, comes from the compressor" further please? I don't understand.

My understanding is that a compressor uses, in this case electric Amp hours, to Convert to mechanical movement (elec motor part). Then the actual Compressor converts mechanical energy to liquid, and or gas flow. Pressure is created by restriction to that flow. No 'energy is created' anywhere in the compressor. I could be wrong.

Also your comment about Solar charging the batteries. To me it does some of the time, ie until the batts are accepting less charge than Solar is outputting.

While there is still sunlight, there is 'excess' solar than just battery charging.

This can be used to power other loads directly. Like say chilling down Hold over plates. This can be used after dark to keep the fridge cool instead of spinning up the compressor using batt AHs.

Ok duty cycle and Compressor COP are a factor, but not what I understand Hold over plates advantage. Ie using otherwise wasted Solar, or engine alternator power later when they aren't being produced.

There is no mention of 'energy creation'. Its simply storing energy like batteries to 'average' power use to average power production.

Duty cycle, yes less start up surges sure, maybe a bit. Compressor COP, hmm, I assume they should be optimized for either system so should be very little in this.

First the second rule of thermo dynamics is Energy can not be created or destroyed.

Twelve volt electricity in watts of power is converted to Btu of energy in a compressor and at its highest Rpm there is a slight increase of energy Watts to Btu.energy. If compressor speed is reduced its volumetric efficiency of gas vapor is more efficient resulting a higher Coefficient Of Performance (COP). Reducing compressor speed achieve more efficient use of energy but will require compressor to run longer. There are some cases where compressor speed set to run at minimum speed can reduce daily energy consumption by 50%. You may have the correct matching energy capacity compressor, condenser and evaporator but efficiency is determined by compressor speed.

If the compressor at a preset speed is producing fixed Btu energy at a COP of 1.5 you would like to think each component of the complete Systems SCOP would match the compressor’s COP. It has been mentioned that eutectic plates improve the COP in a system but in fact they reduce SCOP because they are less efficient because they require more energy in the phase change of solution to ice. Again Eutectic plates used in conjunction with small 12/24 volt compressors are only of value if there is surplus energy from compressor to freeze them. Yes, on these small systems having energy stored in the box does help maintain box temperature when warm product is placed in box. Then the question is if you do not have surplus electrical energy is the loss of space taken by eutectic plate worth it.

Holding energy eutectic plates offer a good solution in off the grid applications that justify them. I have been asked to do a conceptual design for holding plates and refrigeration for 12 and 24 hours hold over time to be used for three walk in rooms. I am this week researching holdover plate companies for the refrigerated truck industry now.
There was a time the pleasure boat refrigeration industry Crosby, Grunert and many private boat owners with large cooling demands used these companies for manufacture ring their plates.

[GILow]

Originally Posted by Richard Kollmann

It has been mentioned that eutectic plates improve the COP in a system but in fact they reduce SCOP because they are less efficient because they require more energy in the phase change of solution to ice.

Yes, but you get that energy back in terms of thermal energy absorption when the phase changes goes back to liquid. So no net difference.

[Richard Kollmann]

Originally Posted by GILow

Yes, but you get that energy back in terms of thermal energy absorption when the phase changes goes back to liquid. So no net difference.

You may be correct if all you are looking for is a one temperature zone drink cooler box.

[GILow]

Originally Posted by Richard Kollmann

You may be correct if all you are looking for is a one temperature zone drink cooler box.

Why is that the case?

[Pete7]

Originally Posted by nilespf

The boat is in the chesapeak and literally every one I have talked to around here either suspects DC of around 50% or have measured them. What I don't have is actual AH usage. Everybody is happy as larks with no energy budget in mind. Hopefully more data is out there.

I had to google it, but you have a similar climate to us. I must measure our fridge sometime (Isotherm GE80 kit), but it's about 2cu ft, say 55 litres. During an average summers day I see the fridge using 3A when running for perhaps 2-3 mins every 10, less during the night. So the fridge uses about 20 - 25A a day.

The portable 20 litre freezer uses a similar amount (3A) but runs much longer 4 mins in every 6 mins, despite only being opened a couple of times a day and has a bath towel over it.

Pete

[nilespf]

[QUOTE=GILow;3087215]

Originally Posted by nilespf

I suspect you may be close to as good as it gets now, depending on a few variables. If we accept that most currently available refrigeration systems are at least similar in performance, I can say that my just-built, 230 litre fridge/freezer at 4 degrees C/-5 degrees C is using 50 AH in 30 degrees C ambient temperature (though it has been colder in the cabin these last few days). So a pretty similar power consumption for a newly (and carefully) built fridge system that is performing pretty much as the spreadsheet model predicted.

Of course, if your fridge box is significantly smaller, or if you only have a fridge not a freezer, then it suggests there is room for improvement, maybe in the compressor and associated equipment or, more likely, in the insulation.

And maybe somebody will chime in with better power consumption figures than mine and I’ll be thinking of making improvements.

Incidentally, I don’t think my 630 AH FLA battery bank Is all that large by today’s standards, but I do think I am lucky in having been able to install 760 Watts of solar cheaply and easily. As you can imagine, 50 AH against that sort of capacity is a trivial concern.

Just one more bit of info and that is the current draw when the reefer "system" is on from that I can compute the DC. ***********If I assume your DC is identical to mine that would put your draw at 5.5 A which is the same as my BD50 @ 3K RPM and the plate running @ 0 deg You may be correct, I'm inclined to think this data suggests it is about as good as it gets.


Pn

[Richard Kollmann]

Originally Posted by GILow

Why is that the case?

Sorry I thought you read my post 107.

[nilespf]

Originally Posted by Pete7

I had to google it, but you have a similar climate to us. I must measure our fridge sometime (Isotherm GE80 kit), but it's about 2cu ft, say 55 litres. During an average summers day I see the fridge using 3A when running for perhaps 2-3 mins every 10, less during the night. So the fridge uses about 20 - 25A a day.

The portable 20 litre freezer uses a similar amount (3A) but runs much longer 4 mins in every 6 mins, despite only being opened a couple of times a day and has a bath towel over it.

Pete

Got it, small but still less than mine. I suspect mine may jump to 60% if in the sunlight.