Eutectic Refrigeration, up to 45% less battery consumption. Here is why..
We all know that a drink with ice in it will stay cold and drinkable at a constant temperature while the ice remains, but will warm rapidly once the ice thaws.
The term ‘Eutectic System’ refers to a refrigeration system that uses the phase change of a liquid medium to absorb and dissipate large amounts of thermal energy while remaining at a constant pre-arranged temperature. Phase Change occurs when we freeze a solution solid by removing its heat or as it thaws into a liquid again while it absorbs heat. The phase change medium or eutectic solution is stored in the stainless steel eutectic plate and acts like a re-new able ice block, freezing solid during the refrigeration run cycle and thawing during off periods and all the time maintaining a constant cabinet temperature like the ice did for the cool drink!
Other products such as a thin aluminum evaporator plate can also absorb and dissipate thermal energy but when a relatively large volume of solution is used as in the eutectic plate and it is allowed to freeze solid on the refrigeration run cycle, then thaw during the off cycle, a massive amount of stored thermal energy is in play.
By comparison with a thin aluminum cold plate, the first and most obvious advantage the eutectic system has is its far greater mass and therefore thermal hold-over storage capacity. (A thin slice of ice will disappear much quicker than a 60mm thick block would)
But this thermal storage advantage pales into insignificance compared to the other unique benefit that the eutectic system’s phase change phenomenon delivers. This phenomenon called ‘Latent heat’, multiplies the eutectic’s thermal storage capacity many times providing huge hold-over periods where the unit stays off for many hours even days in cooler times.
As an example, using a quantity of water as a eutectic solution and knowing that water’s phase change occurs at approximately 0°c, this water will absorb and dissipate 80* (Yes eighty!) times as much thermal energy while freezing and thawing as it would for any other rise or fall of a degree centigrade.
A eutectic system will run for a long period while refrigerating the eutectic solution until frozen solid. It then stays off for relatively much longer periods while this thermal mass thaws completely before running again. All the time maintaining cabinet temperature.
Eutectic systems have many advantages including the following..
- Long ‘hold-over’ off periods due to the large thermal mass and more importantly because of the eutectic’s phase change.
- Refrigeration can be at a time that suits the power supply, or during cooler periods when refrigeration systems are more efficient.
- Much lower overall power consumption due to more efficient refrigerant evaporation in a saturated environment,
- With ECO2 the eutectic mass is automatically refrozen whenever sources of power are abundant, reducing demand on batteries.
- Virtually ‘cooling in advance’, use of abundant power supplies provides a day or so of refrigeration requirement in storage.
- A day or two of sailing without the need of additional cooling is possible if battery power supply is down. (i.e. solar but no sun!)
- Eutectic systems store energy at a third of the weight that would be required in batteries to provide the same refrigeration effect.
Ozefridge Sure-Thaw Controller: Its Importance.
The vast majority of so-called Eutectic systems do not and simply can not function properly as true eutectic systems.
We have found that either the eutectic solution mix is not appropriate for the cabinet temperature required therefore phase change is not occurring, and / or the system is controlled by a thermostat reading cabinet air temperature or worse still, also using an ancient mechanical type temperature controller!
If the eutectic solution doesn’t freeze on each run cycle and then thaw completely during off periods, then the system can not operate correctly. It is as simple as that!
The Ozefridge Sure-Thaw control system allows the user to digitally set the compressor cut-out below the eutectic freeze point and cut-in above the eutectic thaw temperature, with a controller that reads the actual eutectic temperature. This unique control method guarantees that each on / off cycle of the refrigeration system provides proper phase change and benefits of the eutectic principle.
Ozefridge Industries is a Mackay family company, refrigerating Australia since 1965
Above: The start of the system build process. Laser cut out stainless steel is processed and folded in this adjacent sheet metal-work area, then bought to the start of the build line, a clean, air conditioned and dedicated assembly area.
Above: On the far bench s/s cases have mounts, valves, captive nuts, and terminals fitted ready for component fitting before moving forward where compressor, condenser and electrical etc., are added.
Above: A batch of refrigeration units ready for overnight evacuation then testing with a digital vacustat, gauges and detectors. This facility can evacuate and digitally charge 24 units at one time. Each unit is data logged, results recorded.
Above: We carry over 250 DC compressors, motor drivers, condensers, 032 filter dryers, fans etc., in stock. No shortage of spares at Ozefridge and we can express post same day to most areas world wide. Customer support with spare parts available off the shelf, system selection and servicing advice 24/7, being priorities.
Above and below: Rear electrical fitting station. All electronics are loaded here, tested and conformal coated before fitting to refrigeration units and test run.
At Ozefridge our manufacturing standards are focused on their marine applications where users demand the best possible materials, build quality and performance.
Ozefridge ticks all the boxes and now with a 5 Year compressor Warranty..
An extended description of system components and features…
COMPRESSOR. ( In more detail….)
The compressor is literally the heart of a refrigeration system and likewise is a most important component. It must be adequately sized to cope with the job required and be protected from harm if it is to provide long term efficient service.
Many manufacturers choose to use compressors a fraction of the capacity of the Ozefridge BE90 which is fine for small cabinets and if the load matches.
But it is false economy to send a boy on a man’s job specially with cabinets getting larger, user expectations growing and a warming environment. It is nonsense to say that a smaller compressor is more power efficient. Certainly they use less power but they also do less work running longer to get the job done, if at all!
The correct compressor for the job is the best with a compressor too small being the most inefficient and often unable to perform when most needed, when it is the hottest!
With the development of our ECO2 power management system has come the need to get as much refrigeration (Thermal energy stored) happening whenever power is abundant. The additional capacity of the BE90 allows the system to best utilize that power when available, providing more refrigeration with less demand on batteries.
The Ozefridge BE90 uses a solid state Soft Start motor driver module…
More here: Soft Start compressor Motor Drive Modules
The BE90 is the best DC compressor we have ever seen/ used and as a result we now offer a unique FIVE year compressor warranty. Labour and re-gas included when returned to Ozefridge for repair.
CONDENSER. (Unique Ozefridge design)
The A480 uses a triple pass air only condenser while the AW480 model uses the unique Ozefridge engineered air and water cooled condenser and can operate as either air or water cooled. The condenser fan and water pump are thermostatically controlled to maintain correct condensing. On A480 and AW480 models, the condenser temperature can be read by pressing the lower left controller button. Condenser fan and pump are thermostatically controlled to cope with all environments.
AW480 with water cooling: Heat laden refrigerant gas flows through the ‘yellow & purple’ coil passes while water is sent separately through the ‘green’ coil passes to extract heat.
This condenser allows the system to be operated as ‘air cooled only’ with heat dissipated via the condensers massive 6550 square cm of fin surface area.
When water cooling is employed, water passes through the water coil cooling the condensers fins and this in turn cools the refrigerant gases.
This simple but practical method of water cooling eliminates electrolysis problems associated with other methods such as ‘keel coolers’ and ‘shell and tube’.
Unlike other water cooled condensers, the refrigerant is not in direct contact with the water galleries and therefore can’t be lost or contaminated due to ‘electrolysis’ or corrosion.
This condenser is best water cooled by re-cycling water from the vessel’s fresh water tank with the pump kit supplied. (Using raw water is not recommended and will cause harm eventually)
The Ozefridge condenser is conformal coated to resist air borne corrosives.
Water cooling is essential on twin plate freezer systems and highly recommended for all systems specially if used in the tropics or other hot climates.
Water is provided by using the Ozefridge P3 water pump kit supplied with AW480 units. This kit comprises a micro centrifugal pump, 10 Metres of food grade vinyl tubing and a check valve.
The P3 pump is to be wired to the pump terminals on the AW480 and then operates automatically when the compressor runs. (Temp. controlled) Passing through food grade materials, the fresh water is not harmed or consumed.
The ‘Air / Water’ switch allows the choice of condensing. (Switch off at night!)
Water cooling is said to increase power consumption. This may be true of other systems or methods, but is totaly wrong for the Ozefridge method.
The P3 water pump uses less than 4 watts/hour (1/3 amp!) yet reduces the compressor consumption by >18 watts/hour and decreases run cycle times by up to 34%. (At 40c)
The Ozefridge water cooling method greatly reduces overall power consumption without fear of ‘electrolysis’ corrosion damage.
The P3 water pump is the centrifugal type and therefore much quieter, easier running and use far less power than the diaphragm types.
All Ozefridge eutectic plates are fabricated not welded. Being fabricated they are not subject to stress fractures and possible leaking due to the constant expansion and contraction which occurs during each cooling / thaw cycle. The pressed 318 grade stainless housing is bolted to a rear mounting plate with stainless steel bolts and nuts and uses a flexible sealant.
The stainless steel rear mounting plate has an offset with a row of mounting holes for easy fixing to the cabinet’s interior with the stainless mounting screw provided.
There are six different eutectic plate models of differing dimensions so as to suit the various cabinet sizes and shapes. Each model can be supplied specifically for either landscape or portrait mounting. (Nominate). Each model can be supplied for either a single plate or twin plate application.
Each eutectic plate or pair of plates, has a single 25mm diameter x two metre insulated hose that carries the refrigeration pipes, temperature sensor cable and a spare twin cable.
These are fixed to the top of the plate and usually exit left as seen here. Exit right and longer lines can be ordered.
Each plate has a brass filler cap for adding the eutectic solution when fitted in the cabinet.
Note: The following are standard on A480 and AW480 systems, optional on the A450. The digital controller has an LED temperature read-out and twenty programmable functions including eutectic mass and condenser temperature control cut-offs and hysteresis . Apart from temperature control, other parameters are pre-set and locked.
The eutectic control section uses the Ozefridge ‘Sure-Thaw’ principle where the core temperature of the eutectic mass is monitored and the system cycles on after the mass has thawed and off when the system has re-frozen the eutectic mass again. This ensures that the benefits of the eutectic system are delivered with each cycle. (Latent heat at each phase change) This temperature is displayed on the LED constantly along with function indicator LED’s
Right: The control panel is located on the front of the A480 & AW480 condensing unit. (AW480 pictured, can be made remote.)
ECO2 Power Management System. (Standard now on both models)
This has been our most worthwhile development in recent years as it has addressed the never ending concern about power supplies. We have received a lot of assistance and ideas from many users in its development and thank them for their input. Now standard on all A480 and AW480 units.
Firstly, an explanation:
Refrigeration systems consume electrical energy (power supply) converting it into thermal energy (to make your cabinet cold)
There are two distinct groups of electrical power available to supply your fridge system:
A) Abundant power (Mode A) is whenever the optional 110 or 240 volt AC mains or generated supply is available OR when the 12V DC power supply is fed from an alternator, solar, etc. and the voltage exceeds 13.7V. (Excess power after the batteries are topped up, energy that would otherwise be wasted.)
B) Limited power (Mode L) is when power supply is from a battery source only.
ECO2 is a power management unit that reduces battery demand by operating as follows:
- Whenever power supply is abundant (Mode A), the ECO2 automatically triggers the system’s controller into run mode starting the Ozefridge system, forcing it to consume, convert and store the abundant electrical energy into the eutectic plate(s) as thermal energy for future use. (Unless additional refrigeration is unwanted)
- When engaged ECO2 also operates the Ozefridge system at maximum compressor speed to convert the most refrigeration into eutectic storage while the power supply is abundant.
- When ECO2 takes control the eutectic mass is maintained in a frozen state within the colder half of the pre-set temperature operating range. This maintains the most eutectic thermal mass into storage while the power supply is abundant.
- During normal operations the ECO2 checks constantly for the availability of abundant power. This ensures that any abundant power is always detected.
- Whenever only limited power (Mode L) is available, the frozen eutectic mass will hold-over the cabinet temperature for up to a day or so and if no further opportunity to use abundant power occurs in the meantime, the system automatically reverts to using the limited battery supply as further refrigeration is required.
Two examples of how this exclusive Ozefridge feature can spare your batteries:
Example 1: Bill sails his yacht mostly at weekends and when at sea battery power is at a premium. During the week, Bill’s yacht is in the pen connected to 240 volts mains power so he leaves everything in the fridge and it runs automatically on the mains ready for the next outing. While at sea Bill runs a small gen-set at night for an hour or so and on occasions he is also under motor.
Outcomes with a basic air cooled aluminum cold plate system:
If Bill installs an air-cooled cyclic cold plate system, his fridge will run on average say 10 minutes on and 20 minutes off, hour after hour! But without the backup of water cooling, the run times will increase and efficiency will decrease as temperature rises during the hotter months. (Just when I needed you most!). This type of cyclic refrigeration requires power on demand throughout the 24-hour day relying mostly on the batteries limited power supply and using little of any abundant power when available. (While costing less initially, this is the most inefficient system with the greatest demand on batteries).
Outcomes using an Ozefridge Eutectic System with ECO2:
If Bill installs an Ozefridge AW480 eutectic system with air and water cooling, 12 Volt & 240 AC operation and ECO2 , he will enjoy all the benefits of eutectic refrigeration and have the most comprehensive power management, control, and fail-safe system available.
When Bill unplugs the 240 volt shore-power and sails out from the pen, his eutectic tank will be frozen solid with no further refrigeration needed until the eutectic mass is consumed. Now later at sea, the solar panel has topped up the battery yet there is still plenty of sun and therefore abundant energy.
As the battery volts exceeds 13.7 volts, the ECO2 will cause the Ozefridge to run and store more energy in the eutectic plate(s). Solar energy that would have been wasted.
Later at night Bill runs the 240 volt generator for an hour or so and again the ECO2 trips in and unlike other systems will choose to run direct from the gen-set’s 240 volts leaving any DC charge into the battery to be a net again.
With the ECO-2 power management and Sure-Thaw control; this system would require little if any power from the battery supply.
Example 2: Fred has found that his refrigeration is cold enough if his Ozefridge eutectic system has one freeze per day involving about 4 hours of total running during the 24 hour period.
Often Fred’s batteries are fully charged yet there is still plenty of wind or solar power, power that would otherwise be wasted, but the ECO2 is causing the Ozefridge to run and store this as thermal energy. At night, if the gen-set is used, the Ozefridge will be at it again, storing energy (refrigeration in advance) and sparing precious battery supply. Fred’s system rarely uses power from his battery supply and when he is in the marina the Ozefridge will run on the mains shore power.
Other benefits of the ECO2 management system:
1) Less cost and weight: Reduced demand means that the need for additional battery power is reduced or eliminated.
2) Reducing the number of times any battery is discharged increases its life considerably.
3) With less stored battery power required for refrigeration, more is available for other requirements.
ECO2 is a product developed by Ozefridge and is for Ozefridge Systems only. (Discretely installed inside the A480 or AW480 stainless steel case)