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

[StuM]

Originally Posted by Dsanduril

Would you buy his fridge equipment if it draws 36A (because that's what he says)?

1 Watt = 1 Joule per second (don't take my word for it, look it up!)
There are 24 x 60 x 60 = 86 400 seconds in a day.
So 433 Watts for 1 day is 37 411 200 Joules.

It takes 4.18 Joules to raise 1 gram of water by 1°C (again, look it up)
So 433 Watts for 1 day is sufficient heat to raise 8 950 048 grams of water by 1°C.
Putting that into more realistic terms:
That's sufficent heat to raise 111 876 grams of water by 80°C (from 20°C to 100°C)
Or, it's sufficient heat to bring 111 litres (29 US gallons) of water from room temperature to boiling point.

[kas_1611]

Always amuses me that the only country to still use BTU (BRITISH Thermal Units), an archaic unit at its best, is America. Even we Brits gave up using it decades ago.

[more]

Originally Posted by Dsanduril

3

Watts are an instantaneous measure of power in use. Wh (or Ah with voltage appended) are a measure of energy used. You must have the time constant to talk about energy. And batteries (the initial point of the OP's post) are energy storage devices. You can extract power from them, but the entire metric of their storage is energy. Energy and power are not the same thing. The OP desires to talk about energy, but instead uses units of power. Would you buy his fridge equipment if it draws 36A (because that's what he says)? Probably not. But 10A, for 3.5 hours a day? Now we're talking. How about 1.5A but it runs all the time? That would be pretty easy to support.

Electricity is measured in Watts and kilowatts
Electricity is measured in units of power called Watts, . A Watt is the unit of electrical power equal to one columb/amper under the pressure of one volt.
ampere ampere-hour is old terms for Columb units by measuring the electromagnetic force between electrical conductors carrying electric current.
The ampere was then defined as one coulomb of charge per second
The coulomb (symbol: C) is the International System of Units (SI) unit of electric charge. Under the 2019 redefinition of the SI base units, which took effect on 20 May 2019,[2] the coulomb is exactly 1/(1.602176634×10−19) elementary charges.

when somebody tell me my light spend day 2 amps don't mean anything, what because in citation only thru is 1 day 24 hour. other is all xx.
most important in formula missing constant voltage and current Columb.

Do you understand how long is my boat if I tell you my boat is long 50 feet of my father's winter boots?

again if somebody tells me he on frige spent in day 1000 watts hour I understand how much need energy to recovery/calculates loose. not matter system is 12,24,220,1000 volts

[AndyEss]

Regardless of units (I agree getting units right is fundamental in applied arithmetic) the OP is proposing to use freezing water as a form of electrical energy storage, useful in a refrigerator application.
I’m not sure what Richard Kollman’s point was in asking his question.
The phase change energy lost or gained is exactly equal in either the melting or freezing direction. In that, eutectic change is more efficient in energy storage than any existing battery chemistry, though LFP is far more efficient in charge/discharge as compared to lead acid batteries.

[joelhemington]

As all we Luddites know (yes. I'm a Luddite and proud of it) To reduce energy consumption in your frig or freezer all you need to do is fill all unused space with plastic bottles full of water. Less dead air space will give you much better efficiency regardless of your understanding of electrical issues.

[sailorboy1]

That is completely wrong, unless you just don't believe physics and thermodynamics

[rslifkin]

Originally Posted by sailorboy1

That is completely wrong, unless you just don't believe physics and thermodynamics

Less air space does help efficiency (although not dramatically). In 2 ways: less heat gained during a short door opening (air exchanges quickly, but heat transfers in/out of the contents slower). And longer, less frequent compressor run cycles, which ends up being slightly more efficient.

[sailorboy1]

Post the heat transfer equation to prove your position.

[Dsanduril]

Originally Posted by more

Electricity is measured in Watts and kilowatts
Electricity is measured in units of power called Watts, ...

Flow of electricity is measured in Watts/kW. But the amount of electricity used is measured in Wh/kWh. When was the last time you got a bill from the electrical utility in W? For residential customers electricity is billed in kWh, not kW.

For commercial customers there is frequently a "demand" charge measured in kW - this is maximum flow of electricity that that customer requires, then there is an energy charge measured in kWh, this is the amount of energy used. There is a big business in load-leveling where the total energy usage may not change, but the maximum demand is reduced so that the demand charge is reduced.

Nevertheless, electricity used over time is measured in Wh, kWh, MWh or similar units that include a measure of the power used (W) and the period of time for which it was used.

Think of it this way - you have a 100W light bulb in your kitchen, you ran it for an hour this morning. Did it use the same amount of electricity as the 100W light bulb you left on in the basement and forgot about and it ran for a week? They're both using 100W, so they must have used the same amount of electricity? So the bill from the utility will be the same? So I don't ever need to turn off lights?

[Gary Matthesen]

This sounds like an episode of Big Bang Theory. Who gets to play Sheldon?

[Montanan]

Originally Posted by OzeLouie

It can be done and here is an example:

1. Sample cabinet is 90 litre capacity top opening with 75mm thick walls, 100mm base.
2. Heat load calculation for this cabinet including common use contingencies and maintaining +2C to +5C cabinet temperature in a maximum 30C ambient, indicates 433 watts per day. (By 3.41 for BTU’s)

First of all this refer is operating TOO COLD: FYI - Serve most premium lagers between 42 and 48 degrees Fahrenheit (6 to 9 degrees Celsius) and quality ales between 44 and 52 degrees Fahrenheit (7 to 11 degrees Celsius).
Serve authentic Stouts as warm as 55 degrees Fahrenheit (13 degrees Celsius), which is British cellar temperature.
3. Refrigeration using a 3.5cc condensing unit coupled to a 5.1 litre eutectic plate of 530 x 350 x 40mm overall.
4. Phase change capacity of 5.1 litres at 85 watts per litre, is approx. 433 watts.
5. Refrigeration would be required to run a minimum of 3.5 hours per day.
6. If *abundant power is available and the system has auto switching to consume this power during that period, then virtually no battery power is consumed for the 24 hour period. (*Abundant power is that which is available from any source like solar, gen set etc after batteries have been topped up and power in would otherwise be wasted!)
7. In this example abundant power would need to be available for at least 3.5 hours during the day otherwise some battery power would be consumed to finish the eutectic mass re-freeze.
(Heat load calculator pictured below with details, click on pic to expand).

Attachment 239313

Oh, for Joule's sake! What [or Watt] is the thermal load that is being required to be heat transferred with this exemplary refrigerator? If one does not have a measure of the heat one is trying to resolve one has no starting point for discussion. And watt is the coefficient of performance of this exemplary refrigerator?

Proposed framework for CruisersForum analysis and discussion:

Let's say we have four persons on board for drinks, each person drinks 6 beers during the day, that requires 24 openings of the refer during the heat of the day. What is the thermal load of cooling the warm air that entrains into the chilly box with each opening and how much heat has to be removed from each replacement beer when one replaces a warm beer for the cold one you took out of the refer. Too keep this simpler, we will not factor in the 99 bottles of beer on the wall and the effort to take them down and pass them around, be that measure of work or watt ever you wish to use, e.g., say a nautical seahorsepower. Note since the refrigerator is sized to have only 90 liters capacity [Note the correct spelling is liters in Yankeeland, not litres] that means the other 99 liter bottles are kept stored in the 30 C ambient shelf on the wall. Liters or liters, just don't get confused with what the cat leaves in its box.

Arghhhh! Okay, so can't we just stick with the standard unit of measure for cooling capacity of tons, [as in tons of ice].

With a measure of tons one knows how many bags of ice to place in the chilly box and how big of a dinghy one needs to transport said tons of ice to your yacht.

And be sure to factor in to the calculation whether you want your martini shaken or stirred, shaking a martini uses more ice and makes for a wet martini.

And let's not evolve to misusing the term of foot pound for torque when one is discussing the measure of pound foot.

Now with that said, I will go retrieve a cold one from my lake which surface temperature has now risen to a balmy 49 F / 9.8 C. so as to wash down a Newton.

And will leave this discussion to the expert champagne drinkers and their 6.1 to 8.1 US fl oz. coupes.

Cheers!

[BlackHeron]

We have an Ozefridge unit installed and I do have to say it is a pretty slick system. We see approximately the numbers the OP has posted and almost exactly what their system estimation survey quoted us after we measured our icebox volume and insulation thickness and they did their engineering calculations before we purchased. They came in under all the options we were considering.

The beauty of the system is that it can run mainly during daylight hours on power that the solar controller would be wasting anyhow when the system throttles back during the end or after the charging cycle is complete. I only wish our system had been sized so that the eutectic platenonly needed to be frozen only once in a 24 hour cycle. Instead it needs to run about 1.5 times a day. If the system runs from the low setpoint around 10-11AM when our batteries are nearly charged then it needs to be run again before the sun goes down or else it won't make it through the night.

The ECO2 "smart" controller isn't quite smart enough to understand daylight hours and the manual mode is just an on/off switch that not only requires a manual turn on but also a manual shut down again when the holding plate hits the Target temperature (-10c for us with a fridge setup.).

The problem with this is we will often turn the unit on manual mode about and hour before getting into an anchorage and then forget to turn it back on. We've run the plate down to -20c or more by accident whixht is pretty hard on the fresh veggies in the fridge. If one forgets to turn it off I think it would run forever until it just couldn't make the holding plate any colder. Ouch.

Instead of an on/off switch, or in addition to it, it would be nice to just have a pushbutton that simply initiated the cooling cycle and then let it run until the cold setpoint is reached and then shut off automatically from there. A set of auxillary dry contacts that one could set a relay off of the solar panel controller when it goes into "dump mode" would be handy too.

But you can't have everything and all-around we really like our Ozefridge unit and would certainly buy again or recommend it to other cruisers who wanted to conserve maximum power and especially if they were a little short of Watt-Hours on their battery bank size and were worried about making it through the night and depth of discharge cycles -since the unit rarely needs to run outside of daylight hours if set up properly and maybe baby-sat at times.

[OzeLouie]

Originally Posted by BlackHeron

We have an Ozefridge unit installed and I do have to say it is a pretty slick system. We see approximately the numbers the OP has posted and almost exactly what their system estimation survey quoted us after we measured our icebox volume and insulation thickness and they did their engineering calculations before we purchased. They came in under all the options we were considering.

The beauty of the system is that it can run mainly during daylight hours on power that the solar controller would be wasting anyhow when the system throttles back during the end or after the charging cycle is complete. I only wish our system had been sized so that the eutectic platenonly needed to be frozen only once in a 24 hour cycle. Instead it needs to run about 1.5 times a day. If the system runs from the low setpoint around 10-11AM when our batteries are nearly charged then it needs to be run again before the sun goes down or else it won't make it through the night.

The ECO2 "smart" controller isn't quite smart enough to understand daylight hours and the manual mode is just an on/off switch that not only requires a manual turn on but also a manual shut down again when the holding plate hits the Target temperature (-10c for us with a fridge setup.).

The problem with this is we will often turn the unit on manual mode about and hour before getting into an anchorage and then forget to turn it back on. We've run the plate down to -20c or more by accident whixht is pretty hard on the fresh veggies in the fridge. If one forgets to turn it off I think it would run forever until it just couldn't make the holding plate any colder. Ouch.

Instead of an on/off switch, or in addition to it, it would be nice to just have a pushbutton that simply initiated the cooling cycle and then let it run until the cold setpoint is reached and then shut off automatically from there. A set of auxillary dry contacts that one could set a relay off of the solar panel controller when it goes into "dump mode" would be handy too.

But you can't have everything and all-around we really like our Ozefridge unit and would certainly buy again or recommend it to other cruisers who wanted to conserve maximum power and especially if they were a little short of Watt-Hours on their battery bank size and were worried about making it through the night and depth of discharge cycles -since the unit rarely needs to run outside of daylight hours if set up properly and maybe baby-sat at times.

Thanks for posting relative to the theme that was intended by this thread before it got high-jacked!
To automate your second start for the day and have it then function between cut in (SET) and cut out (SET + HYS) simply apply a 300k resistor across the external probe terminals with a push button switch in series. This momentary resistance will put the controller into 'run mode, simply press the button and forget.
Thanks for the idea, we will incorporate this with any future upgrade and BTW, did you have any difficulty understanding the 'heat load estimator I supplied and was there another better one available?

Louie

[Richard Kollmann]

Originally Posted by AndyEss

Regardless of units (I agree getting units right is fundamental in applied arithmetic) the OP is proposing to use freezing water as a form of electrical energy storage, useful in a refrigerator application.
I’m not sure what Richard Kollman’s point was in asking his question.
The phase change energy lost or gained is exactly equal in either the melting or freezing direction. In that, eutectic change is more efficient in energy storage than any existing battery chemistry, though LFP is far more efficient in charge/discharge as compared to lead acid batteries.

I am with you on batteries and charging current but I do not think the pleasure boat refrigeration companies will agree with your energy to freeze a eutectic plate producing equal energy when melting melting. I am still waiting to hear from those who believe energy is created inside eutectic plates.
The only good selling point for eutectic plates is if they get most of thiir energy from alternative energy Wind Solar or on board Generators.

[OzeLouie]

Originally Posted by Richard Kollmann

The question I have for others to answer is, Are the Btu's of melting eutectic ice equal to the amount of Btu energy required to create eutectic ice? If answer is Yes or No explain.

Yes theoretically the same, but in practical use the heat needed to re-freeze the eutectic mass has have the ongoing cabinet /product heat incurred during that refreeze run period, added .