Freezer "ballast" and eutectic solutions question

[SV THIRD DAY]

Originally Posted by Zanshin

d) According to the literature supplied by Danfoss and other compressor manufacturers, there is a significant energy loss on restarting the compressors and they recommended running for as long as possible at lower compressor speeds when it comes to total energy efficiency. Unfortunately the typical boat setup only has an analog on/off thermostat system which doesn't lend itself easily to controlling compressor speeds (although some smart speed control systems try to do a pretty good job)..

Ah...but the data and details matter, so it's really hard to leave that out and have this discussion. For starters, lets look at your items D.

These two data sets go to help understand the number of on/off cycles between a Holding Plate vs Evaporation Plate system.

By monitoring temperature, you can see that the holding plate system compressor turn On 4 times in the 24hr period to freeze down the holding plate. Where the evaporation plate unit turn on/off more than 150 times in the same period to maintain the temperature.

Holding plate temperature data with hold-over capacity.



Evaporation Plate Temp Data with no hold-over capacity

[SV THIRD DAY]

Originally Posted by Zanshin

Don stated

to which SV Third Day responded

I hate to have to disagree with him and his scientist, but I'm a firm believer in the first law of thermodynamics and Conservation of Energy. Entropy notwithstanding, I'll side with Don on this one.

Zanshin doesn't quite understand the proper role of a eutectic holding plate operating on 12v rather than a eutectic holding plate operating on an engine driven compressor where bulk BTUs are available. This lack of context and understanding gets people into trouble all the time....but that's ok, I wish him well. Good luck with your water bottles and microprocessors.

[senormechanico]

Trying to make this as short as possible.
In 1993, we met and befriended some chemistry PHD's turned cruisers who lived in Santa Barbara CA. They were not impressed with any of the holding plate "eutectic" solutions, as according to them none of the solutions actually phase changed over a tight temperature range. According to them, most just use proplyene glycol variations.
Water phase changes in a couple of degrees whereas antifreeze in a car changes over a wide range.
Their idea was to invent a solution for a freezer that changed like water, but at at zero f.
They did just that in their garage, and while going through all the patenting, licensing efforts etc. they had 55 gallon drums of the stuff taking up space.
Bottom line is, we purchased a holding tank's worth, used it on our Lord Nelson35 while in Mexico.
Every morning around ten AM I manually kick started our 6 cubic foot fridge / freezer which had a thermostat. It ran for around 3 1/2 hours drawing 17 amps and shut off automatically when the freezer got to -6f.
We had a top opening freezer of around 1.5 cu ft. and a front AND top opening fridge.
Even in the Mexico heat, it never ran until the next morning when I'd kick start it usually reading +3f in the freezer.
During the installation and construction of the water cooled Isotherm / holding plate system, I had to modify the electronic non programmable thermostat by changing resistor values which took forever. We made charts of time vs. temperature until our heads were spinning.
When we were done with it all though, we had a cold water loop with a dispenser on the counter top for instant cold drink, lots of available ice too.
470 watts of solar kept the whole boat in juice.

Just a few years ago, we checked in with them.
Their licensing never went through, and they said we could use it for our own if we wanted to.
Our current boat is too small for a holding plate system so we never took them up on the offer.
Currently, we have a Vitrifrigo BD35 / keel cooler which does nicely.

[Zanshin]

Rich - it would seem that you don't like people disagreeing with your opinions, plus you've now intentionally switched the subject to holding plate vs. 12VDC - something I never asked about.

Just for the record, could you tell me (and Don, perhaps) why you don't agree that the energy going into a phase-change isn't the same as that coming out? All of the literature I've seen asserts the opposite. So instead of merely stating that other's don't know what they are talking about, you could explain it to us; perhaps with a reference or two.

[SV THIRD DAY]

Originally Posted by Zanshin

Rich - it would seem that you don't like people disagreeing with your opinions, plus you've now intentionally switched the subject to holding plate vs. 12VDC - something I never asked about.

Just for the record, could you tell me (and Don, perhaps) why you don't agree that the energy going into a phase-change isn't the same as that coming out? All of the literature I've seen asserts the opposite. So instead of merely stating that other's don't know what they are talking about, you could explain it to us; perhaps with a reference or two.

I was always warning people of the myth that adding water bottles (or filled with a eutectic) saves you power. It doesn't work not because I think so....but because I have the lab data that shows it.

The conversation then morphed, since as you said you left out data, which is where we started talking about two different things.

[sailorboy1]

Originally Posted by MarkJ

On some cruising boat we have excess electricy generated during the day by solar. Many good setups are at 100% by midday.
So wouldn't using 'excess' power in the early afternoon make an overall benefit?

Mark

I would say yes, it could be a benefit. If you could lower the temperature in the afternoon with the excess power that the solar is putting out you may reduce the electrical loads over 24 hours a little. The thing is that once the solar isn't putting out the excess you need to turn the temperature back up. But no one probably wants to do this each day. I have considered using the aux relay on my solar controller to do this so that if the batteries go into absorption the frig (freezer in my spill over system) would run continuous till the sun goes down enough to where the system can not maintain in float.

But it occurred to me that it was a lot of trouble for nothing really. Because unless the house bank was getting down low at night what difference did it make. If I have excess power I excess power and why brother trying to "save" any?

[colemj]

Very few boats regularly have excess electricity by mid day.

Many, many boats, however, are regularly killing their batteries early by mistakenly believing they are fully charged by mid day...

Mark

[sailorboy1]

Originally Posted by colemj

Many, many boats, however, are regularly killing their batteries early by mistakenly believing they are fully charged by mid day...

Mark

I try to maintain my batteries, but far as I'm concerned if you get 4-5 years out them you didn't "kill them early", you just used them and that's just part of the costs of boating.

[SV THIRD DAY]

Originally Posted by sailorboy1

If you could lower the temperature in the afternoon with the excess power that the solar is putting out you may reduce the electrical loads over 24 hours a little. The thing is that once the solar isn't putting out the excess you need to turn the temperature back up. But no one probably wants to do this each day. I have considered using the aux relay on my solar controller to do this so that if the batteries go into absorption the frig (freezer in my spill over system) would run continuous till the sun goes down enough to where the system can not maintain in float.

But it occurred to me that it was a lot of trouble for nothing really. Because unless the house bank was getting down low at night what difference did it make. If I have excess power I excess power and why brother trying to "save" any?

Bingo...
They make smarter thermostats that will turn your system on when you you have "extra power" with a settable voltage and those can be of savings really only when you have some hold-over capacity. So they work well for holding plate systems but are really not worth it for evaporation systems. Trying to do it manually but dialing up the thermostat during the day and back down at night is just not realistic for someone living full time on a cruising boat and it will just lead to you having frozen lettuce in the morning rather than saving any real amounts of power.

Want to use less amps with the system you have:
1. Improve your box seals.
2. Keep your holding plate or evaporation plate as frost free as possible. Our tests have shown as much as a 30% decrease in efficiency by having a snow ball plate/evaporator.
3. Add insulation to the inside walls of your box.
4. Drink warm beer.....

Oh and ++ to what Mark said about undercharging batteries.
Way too many cruisers think their Wet Acid batteries are charged just because your solar controller is showing 14.1v....

[colemj]

Originally Posted by sailorboy1

I try to maintain my batteries, but far as I'm concerned if you get 4-5 years out them you didn't "kill them early", you just used them and that's just part of the costs of boating.

I'm seeing boats with large AGM banks bragging about how their solar has them fully charged by noon - and replacing those batteries within 18 months. And boats with FLA's claiming the same bragging rights and regularly waking up with the fridge having tripped its LVC point over night (and thinking this is normal).

Heck, you can HEAR these "my batteries are fully charged by noon" problem boats every morning on the ssb nets because theirs is the weak signal that is warbling and distorting and usually requiring a relay.

My point was that there are probably less than one percent of cruising boats who can truly claim regular full charge on their batteries at any time of day - and the number may even be as rare as a single percent of only those who make this claim.

I agree with you regarding batteries being a cost of playing the game, and 4-5 years isn't too bad. Pretty good, in fact, for a full-time cruising boat. However, many aren't lasting that long, and many are getting that life by definition only - scrimping and scraping the last two of those years fighting them to the end.

This is where LFP is a game changer. This whole thread is moot in that game.

Mark

[SV THIRD DAY]

Shhhhh....Mark.

The next heresy you will be spreading is that Cruisers don't sail from anchorage to anchorage but just motor around presumably in an attempt to save their sails from UV damage....

Lets not even start talking about pump outs.....

[RaymondR]

But it occurred to me that it was a lot of trouble for nothing really. Because unless the house bank was getting down low at night what difference did it make. If I have excess power I excess power and why brother trying to "save" any?


Comes down to battery life and the amount of electrical storage you need. "cold" is cheaper to store than electricity.


I am converting both a 12V fridge and a freezer to eutectic. They will be controlled through a 24 hour seven day timer to switch on only during the day when I have excess power from my solar panels. The eutectic will hold them over during the night and on overcast days.


I now have 900 amp hours of storage and 480 watts of solar panels and when sailing north still experience power shortages because of shading of the panels by the sails (I am in the southern hemisphere) the eutectic system may help with this problem.


In addition the eutectics will give me a hold over capacity in the event of fridge/freezer problems (I also carry a supply of Mason jars so that I can preserve food in the event of a fridge/freezer failure)


I hereby predict that many refrigeration systems will be run as eutectics as solar power penetrates the domestic fridge/freezer market and the manufacturers wake up to their potential.


Using bottles of eutectic in your marine fridge or freezer to provide hold over time or less draw down of batteries during the night is a good idea particularly if you have shore power available to do the freezing before you leave the dock and have a borderline solar battery charging system.

[colemj]

If you are having power issues now, when do you expect to have excess power?

I think you should re read your post and think about it. What you describe is batteries that are never well charged and attempting to save power by shutting down your fridge over night. However, that saved night power will be spent out of your solar refreezing the eutectic just when your batteries need it. It will be a downward spiral.

Your math and assumptions do not work.

Mark

[HappyMdRSailor]

Debate withstanding....

IF.... One were to subscribe to the eutectic solution theory... Wouldn't something actually useful be a better medium???

I'm talking say... something like martini olives...

[colemj]

And ribeyes for the freezer.

Mark