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

[sailorboy1]

Originally Posted by OzeLouie

[B]
Conclusion:
If abundant power is available then the eutectic system not only benefits as a system with a lower consumption rate to achieve the same cabinet temperature, but its daily consumption can be part or totally from the power source when power is abundant and not from the batteries!

Hard subject to describe so I hope this helps.

I don't feel your long drawn out post supports that at all! I feel it was nothing but marketing type of confusion.

No matter what you use to cool the system the energy out equals the energy in. If everything remains the same it matters nothing in the how between the systems boats use for providing the cool in. All it does is move it around at a given point of time in a 24 hour period. If there is enough energy available to freeze those plates there is enough energy to charge the batteries instead.

I am still waiting an explanation of how eutectic changes the UA*delta T of the energy loss across the walls of the system in order to save energy use.

[sailorboy1]

Let my ask this. Batteries are fully charged and I leave the boat for 2 days and it is very cloudy and solar produces 75Ah/day. My evaporative system uses 100Ah/day. I come back to batteries that are -50Ah.

With an eutectic system what are my batteries out?

[Dockhead]

Originally Posted by sailorboy1

I don't feel your long drawn out post supports that at all! I feel it was nothing but marketing type of confusion.

No matter what you use to cool the system the energy out equals the energy in. If everything remains the same it matters nothing in the how between the systems boats use for providing the cool in. All it does is move it around at a given point of time in a 24 hour period. If there is enough energy available to freeze those plates there is enough energy to charge the batteries instead.

I am still waiting an explanation of how eutectic changes the UA*delta T of the energy loss across the walls of the system in order to save energy use.

In fairness, I don't think anyone said that.

The point was that you can save up a bunch of cold in the euctetic plates when you have a surfeit of power which would other be wasted -- on shore power, motoring with batteries charged, good solar day after batteries are charged. What that means is that when you go from the surplus power condition to the using battery power condition, you've got cold saved up, and you will use less battery power. I think the theory is sound. Whether it works well in practice or not I can't say.

I have experience myself with euctetic systems. For years, I used to charter in the Med every summer. It was decades ago. The boats often had engine-driven compressors and euctetic freeze plates and used no electricity at all. It worked really well; it's a damn good system. These were boats without separate generators, so you were running the engine every day anyway. Freeze the plate and you're good for another day. And this was in the Aegean, often in scorching August days with a hot Meltemi wind blowing like a giant hair dryer.

[Richard Kollmann]

Originally Posted by sailorboy1

Let my ask this. Batteries are fully charged and I leave the boat for 2 days and it is very cloudy and solar produces 75Ah/day. My evaporative system uses 100Ah/day. I come back to batteries that are -50Ah.

With an eutectic system what are my batteries out?

The secret to this long thread is don't let the marketing smoke and mirrors get to you. Like Is the enthalpy of refrigeration making ice equal to enthalpy of melting ice or even a standard refrigerator evaporator.

I ask earlier in a simple way is the energy to freeze a eutectic plates solution equal to the energy transfer during ice melting the answer is no because of texture of ice forming over evaporator inside plate, compounded by most of these plates us Glycol based solutions and not true eutectic solutions. A true eutectic once changed to ice the plate will retain eutectic point set temperature as long as a partial ice formation in plate. The design inside of actual evaporator coil and its expanded surfaces will determine its ability to absorb heat from box area and at the same time phase change the solution to ice.

I looked for why Glycol based eutectic are less efficient even when they are cycled today like conventional evaporators. I found nothing to support they were as efficient as conventional evaporators except energy can be stores in plates with eutectic solution having the same Btu value per pound as plain water ice. There are two large eutectic web sites that shade more light on Eutectic Phase Change Storage and Dole Corning eutectic plate application and design. It also has performance figures that demonstrate small losses in true energy losses within plates as I recall.

[rgleason]

OziLouis

Thank you for taking the time to explain so clearly the results of your tests and measurements to us. It does help to understand these details. I look forward to your other posts, and will be bookmarking your explanation.

For those who have trouble understanding, I suggest re-reading several times, and considering the specific points made.

These points correspond with our experience with the system.

[RaymondR]

With a eutectic system you are time shifting your electrical power consumption from a 24 hour night and day time power consumption pattern into a day time only electrical power consumption mode.

Because the refrigeration systems on a boat are a major user of electrical power, which is stored in batteries, this significantly reduces the charge discharge cycling of the batteries which can extend their operating life and thereby reduce replacement costs.

This is achieved by the freezing (change of state) of the eutectic fluid in the eutectic tank thereby creating a heat sink in the insulated refrigerator enclosure.

This heat sink creation is made to occur when the solar panel farm produces it's power during the daylight hours.

The non electrical power consuming, passive heat sink then absorbs the heat flow into the refrigerator enclosure, and its contents, rather than this requiring the continuous electrical power consuming heat pumping of a condensing unit during the dark time hours of the night.

The entire purpose of a eutectic system driven by a small DC powered condensing system is the time shifting of the power consumption from the dark, night time, solar power deficient time period into the daylight profuse, high electrical power producing period by the solar farm so that the expensive storage batteries enjoy far less severe charge cycling thereby extending their life.

This is of far mire benefit to those who live on their vessels away from the marina provided power grid and thereby cycle their batteries to a high degree.

[rgleason]

Dockhead

I agree, but now using the efficient Danfoss compressor systems there is lower maintenance due to the fact that there is no leakage of refrigerant from the belt driven compressor.

Mr. Kollmann,
I have referred to your refrigeration manual and it was helpful when I started to learn, but you should open your mind to the fact that all boats and situations are not the same.
Eutectic was absolutely the answer for our boat and it has served very well for many years without having to change our battery system significantly.

Perhaps you should create your own thread and post there rather than creating another situation where the moderators have to step in, which is where you are headed.

I am going to suggest to the moderators that perhaps this thread should be frozen now so that the information is not lost.

[Off Trail]

OK I know this has been tried by better men than I. But my head hurts. I'm only a befuddled retired engineer. Since when are watts a unit of energy?

Can you please provide a link for where you came up with the numbers you posted?

Knowing I'll regret this....

Dan

[rgleason]

Try lookup of kilowatt hour.

[OzeLouie]

Originally Posted by Off Trail

OK I know this has been tried by better men than I. But my head hurts. I'm only a befuddled retired engineer. Since when are watts a unit of energy?

Can you please provide a link for where you came up with the numbers you posted?

Knowing I'll regret this....

Dan

Hi Dan, Yes it can be confusing but down under and in most of the world (except the USA and two other lesser countries) the metric system has been used for decades. Confusion is common specially when both Imperial and Metric are mixed together. Watts of heat (metric) replaces BTU's and is much simpler to work with as are most factors involved in metric calculation.

My factors quoted are common to the refrigeration industry and as I was taught during my apprenticeship and time at the RMIT. I only quote from my own hands on experiences and training but a search should provide you with confirmation of the factors I used.

[AKA-None]

Originally Posted by Dockhead

The answer to your question can be found in Noether's Theorem, which is the basis for the Law of Conservation of Energy.


Of course energy which goes to change temperature and make a phase change in one direction, is the same as the energy coming out from the same temperature change and phase change in the other direction.



Whether it all comes out as heat is a different question, but the answer to that is almost perfectly yes.

Hmmm so there is no energy lost in transition?
I thought the entropy tax would be there somewhere.

[StuM]

Originally Posted by OzeLouie

The metric measure of heat as in cabinet heat load calculations, compressor output, COP etc is in watts (was BTU’s in the Imperial system)
Approx. one watt of heat has to be removed to lower the temperature of one litre of water by one degree centigrade. (Sensible heat)

You are still demonstrating that you don't understand the basic difference between power and energy.

Watts are a measure of power i.e. the RATE of energy flow. There is no such thing as a "watt of heat". The phrase is meaningless. Are you talking about 1 Watt for 1 second or 1 Watt for 1 hour?

Watt hours (or Watt seconds or Joules or Calories) are the SI measures of heat. One Watt hour is the energy transferred in one hour by a power of one Watt which is 3600 Joules or 3600 Watt seconds.

To lower/raise the temperature of 1l of water by 1°C requires 4,200 Joules of energy. 4200 Joules is approximately 1.17 Watt hours (or 4,200 Watt seconds) So assuming you are talking about Watt hours, you are underestimating energy requirements by nearly 20%.

Approx. 93 watts of heat has to be removed to lower (through phase change) one litre of water from a liquid to a solid frozen mass (Latent heat)

To freeze one litre of water at 0°C requires 334,000 Joules which is 334,000 Watt seconds or 93 Watt hours.

My factors quoted are common to the refrigeration industry and as I was taught during my apprenticeship and time at the RMIT. I only quote from my own hands on experiences and training but a search should provide you with confirmation of the factors I used.

Can you provide a reference from RMIT that says the Watt is a unit of energy (or of "heat")?

[RaymondR]

Originally Posted by rgleason

I am going to suggest to the moderators that perhaps this thread should be frozen now so that the information is not lost.

Please don't, it's oft times the case that matters need to be presented in a number of ways for folks to achieve a proper perception.

The system used to censor the forum deletes posts and recycles the post number which tends to offend those firmly in the free speech camp and causes confusion if the deleted post has been quoted. The down side of offending folks who get a bit passionate on a subject is that they sometimes abandon the forum and they often have a lot to contribute.

A better system would be to have a "sin bin" to transfer the offending post into for say 7 days and then delete and not recycle the post number so one knows it was transferred.

[triibutu]

Originally Posted by StuM

You are still demonstrating that you don't understand the basic difference between power and energy.[/B]

I think it is deliberate to keep the thread hot

[AndyEss]

Originally Posted by Richard Kollmann

The secret to this long thread is don't let the marketing smoke and mirrors get to you. Like Is the enthalpy of refrigeration making ice equal to enthalpy of melting ice or even a standard refrigerator evaporator.

I ask earlier in a simple way is the energy to freeze a eutectic plates solution equal to the energy transfer during ice melting the answer is no because of texture of ice forming over evaporator inside plate, compounded by most of these plates us Glycol based solutions and not true eutectic solutions....It also has performance figures that demonstrate small losses in true energy losses within plates as I recall.

Small losses.

Let not the perfect be the enemy of the good.

As pointed out by previous posters, what OzeLouis is trying to communicate (as I understand it) is to usefully “store” excess electrical power generation in a mode outside of chemical batteries. Storage of ice in a fridge seems to be a perfect application of getting something useful from solar panel output after a battery bank has been charged. I suppose heating and storing hot water (for showers and dishwashing) is another place to “store” excess electrical power, though with no eutectic phase change, hot water storage isn’t particularly energy dense.
RaymondR’s post defined the situation OzeLouis was trying to optimize.
Batteries are far more expensive than containers of frozen water, and even lessening cycling of chemical batteries has positive cost benefits.
Maybe we might cut OzeLouis a bit of slack over mis-use of units and focus on the underlying process he believes has promise.