CONTROLLER AND METHOD FOR CONTROLLING OPERATION OF A REFRIGERANT CIRCUIT

The invention refers to a controller for controlling operation of a refrigerant circuit, which refrigerant circuit comprises a compressor arrangement, a heat releasing heat exchanger heating an external medium, for example ambient air, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in a storage volume, in particular a refrigerant circuit for transport refrigeration.

Controllers for such kind of refrigerant circuits are well known.

The object of the present invention is to operate a refrigerant circuit with optimized energy efficiency.

Such optimized energy efficiency is desirable in particular in case the refrigerant circuit has to be operated under power saving conditions, in particular in case of a power source providing limited power, which can be an engine-less power source, for example a battery.

According to the present invention the controller controls at least one of a first actuator driving said compressor arrangement such that a first parameter detected by said controller meets a predefined first parameter setting associated with said compressor arrangement, a second actuator driving a blower arrangement associated with said heat releasing heat exchanger such that a second parameter detected by said controller meets a predefined second parameter setting associated with said heat releasing heat exchanger and a third actuator driving a blower arrangement associated with said heat absorbing heat exchanger such that a third parameter detected by said controller meets a predefined third parameter setting associated with said heat exchanger. Preferably the predefined parameter settings are energy optimized parameter settings, in particular energy optimized parameter settings specific for the refrigerant circuit which is to be controlled by said controller.

Such energy optimized predefined parameter settings are for example predefined by a calibration process which can be performed before or during use of the controller in connection with the refrigerant circuit or repeated during the course of use of the controller in connection with a refrigerant circuit after certain time periods, for example maintenance periods of the refrigerant circuit.

The advantage of the present invention has to be seen in the fact that the controller will operate the refrigerant circuit under energy optimized predefined conditions.

According to the aforementioned definition of the present invention it is provided that the controller controls at least one of the first actuator, the second actuator and the third actuator based on predefined parameter settings, however it is of advantage if the controller controls at least two or at least all three actuators according to such predefined parameter settings.

According to the concept as explained before the operation of the refrigerant circuit can be already optimized according to the predefined parameter settings.

However in order to permanently optimize the operation of the refrigerant circuit it is provided that the controller optimizes the energy efficiency of said refrigerant circuit, during operation which energy efficiency comprises an optimization of the COP and/or the energy consumption of the at least one actuator controlled in order to meet the respective parameter setting by an optimization process comprising varying the respective predefined parameter setting by a step of change in a predefined direction of change increasing or decreasing the respective parameter setting, waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit, thereafter defining the change of energy efficiency of the refrigerant circuit obtained by said step of change and in case the change of the energy efficiency corresponds to an improved energy efficiency the parameter setting amended by said step of change and said direction of change are maintained and stored as predefined parameters for the next variation of said selected parameter setting, and in case the change of energy efficiency does not correspond to an improved energy efficiency the parameter setting preceding said step of change is maintained and said direction of change is inverted and stored as predefined parameter for the next variation of said parameter setting.

The advantage of this concept has to be seen in the fact that it is possible to further optimize the energy efficiency of said refrigerant circuit during operation so that it is possible to compensate for an influence on the energy efficiency of the refrigerant circuit during operation. Such an influence on the energy efficiency can occur for example by partial clogging of the heat exchangers or by any other influence of the refrigerant circuit, for example environmental influences on the refrigerant circuit but also wear and tear of components such as the compressor or reduced insulation coefficient of the cargo room.

According to the aforementioned concept the optimized process can be performed once, however it is of advantage if such an optimizing process is repeated, for example repeating during predefined periods of time or even permanently.

In connection with the present invention the energy consumption of at least one actuator is optimized. It is of particular advantage if said controller optimizes the energy efficiency of said refrigerant circuit during operation, which energy efficiency comprises an optimization of the COP and/or the energy consumption of at least two, preferably all, actuators controlled in order to meet the respective parameter setting by an optimization process comprising varying a selected one of the predefined parameter settings by a step of change in a predefined direction of change increasing or decreasing the respective parameter setting, waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit, thereafter determining the change of an energy efficiency of the refrigerant circuit obtained by said step of change and in case the change of energy efficiency corresponds to an improved energy efficiency the parameter setting amended by said step of change and said direction of change are maintained and stored as predefined parameters for the next variation or said selected parameter setting, and in case the change of energy efficiency does not correspond to an improved energy efficiency the parameter setting preceding said step of change is maintained and said direction of change is inverted and stored as predefined parameters for the next variation of said selected parameter setting.

The advantage of this concept is to be seen in the fact that the optimization process takes place for the at least two or all actuators controlled in order to meet the respective parameter setting so that all actuators primarily relevant for the energy consumption of the refrigerant circuit are optimized during operation.

Such optimization can take place after certain periods of time or permanently during operation.

According to the present invention it would be possible to apply the aforementioned optimization process to the at least two or all actuators at the same time. However, due to the fact that any influence on the refrigeration circuit which leads to a change of energy efficiency and to an adaption of the one or more parameter settings is very slow it is of advantage if the optimization process is applied to optimize the parameter setting for one of the actuators at a time and then applied to optimize the parameter setting for the next actuator.

The advantage of this optimization of the parameter settings is to be seen in the fact that not all parameter settings are optimized at the same time so that the optimization of one parameter setting cannot have a direct influence of the optimization of the next parameter setting, because the energy optimization of one parameter setting takes place whereas the other parameter settings are maintained unamended.

The optimization process changing one selected parameter setting by one step of change can be followed by again changing the same parameter setting before selecting a further parameter setting.

Such a process can be for example used if the steps of change are defined to be very small so that a slow approach to the optimized parameter setting is desired.

Another advantageous optimization process provides that changing one selected parameter setting by one step of change is followed by selecting a further or another parameter setting and changing said further parameter setting by one step of change.

The advantage of this optimization process is to be seen in the fact that it is avoided that one parameter setting is changed too far which could prevent the optimization of the other parameter settings to lead in summary to an optimized combination of parameter settings. In connection with the aforementioned explanations of the inventive concept the parameters and the corresponding parameter settings have not been specified further.

For example it would be possible to use different parameter settings based on different physical values as far as they are related to the operation of the respective actuator within the refrigerant circuit.

A preferred solution provides that the parameters and the corresponding parameter settings are temperature based.

This means that they need to be related to a temperature but the parameter detected could be for example also a pressure or any other value as far as it relates to a temperature variation.

In particular it is of advantage if the parameters and the parameter settings are based on temperatures detected at the refrigerant circuit.

In particular it is of advantage if the first parameter and the first parameter setting are based on a temperature detected close to the heat absorbing heat exchanger.

Such a temperature could for example be a temperature of the heat absorbing heat exchanger.

However it is of advantage if the first parameter and the first parameter setting relate to the temperature of the flow of gaseous medium through the heat absorbing heat exchanger, in particular to the temperature of the return flow of gaseous medium which is the best indication for the heating of the flow of gaseous medium when flowing through the storage volume.

Further in connection with the embodiments described before the second parameter and the second parameter setting have not been specified further. It is of advantage if the second parameter and the second parameter setting are based on a temperature indicating the operation of the heat releasing heat exchanger.

Such parameters could be for example related to the pressure of the refrigerant flowing through the heat releasing heat exchanger, in particular to the pressure at the high pressure section of the refrigerant circuit.

However it is of particular advantage if the second parameter and the second parameter setting are based on a temperature difference between the saturated discharge temperature detected at the compressor arrangement, in particular the output thereof, and the ambient temperature detected close to the heat releasing heat exchanger.

Another possibility would be to detect the flow of medium through the heat releasing heat exchanger and the heating of the flow of medium when flowing through the heat releasing heat exchanger.

Further, in connection with the embodiments explained before the third parameter and the third parameter setting have not been specified further.

It is of advantage if the third parameter and the third parameter setting are based on the temperature in the storage volume.

This temperature in the storage volume can be detected in various manners.

In order to optimize the control of the third actuator it is of advantage if the third parameter and the third parameter setting are based on the maximum temperature variation in the space within the storage volume surrounding the cargo. Such temperature variation is important to be maintained in order to keep the cargo under optimized conditions.

In connection with the explanation of the invention before the step width of the respective step of change has not been specified.

It is of advantage if the step width of the respective step of change is within the range from 0,1 K to 4 K in particular in the range from 0,5 K to 2 K,, in order to only use very small steps of variation.

According to the embodiments of the invention explained before it has not been specified whether the step width of the steps of change is constant or not.

In the simplest version the step width is kept constant.

However, an improved version of the inventive concept provides that a step width of the step of change is variable between the maximum step width and the minimum step width.

Such a maximum step width and a minimum step width can depend on the conditions of operation of the controller or of the refrigerant circuit.

According to one preferred embodiment for each parameter setting the optimization process starts with a maximum step width and reduces the step width if the change of energy efficiency is reduced in relation to the change of energy efficiency obtained in the course of the preceding step.

This means that if the change of energy efficiency is reduced the step width is reduced in order to slowly approach the optimized value for the respective parameter setting. The inventive concept as explained before is improved if the controller detects, permanently or at least after defined time periods, a cargo temperature by at least one cargo temperature sensor and compares it to a given maximum admissible cargo temperature and in case the given maximum admissible cargo temperature is reached at least one of the first and second parameter settings are changed in order to reduce the cargo temperature.

Such a safe-guard operation is desired in order to make sure that the cargo temperature never exceeds the maximum admissible cargo temperature which has to be maintained in order to maintain the cooling chain for the cargo and therefore to maintain the cargo quality.

Further, according to the present invention it could be possible to control the respective actuator in certain steps.

However these certain steps for controlling the respective actuator should be very small in order to efficiently approach the optimum energy efficiency.

Therefore the respective actuator is controlled in steps amounting to less than 10 %, even better less than 5 %, of the available control range of said actuator.

An improved option provides that the respective actuator is continuously controlled within the available control range.

According to one preferred solution the predefined parameter settings are stored in a memory of said controller.

Further it is of advantage if several operational data sets, each comprising the parameter settings, which refer to different environmental conditions detected by said controller are stored in the memory. With the several operational data sets it is possible to provide optimized parameter settings for different environmental conditions.

These environmental conditions can be any conditions provided by the environment of the storage volume which have an influence on the energy efficiency of the refrigerant circuit.

One example of such several operational data sets is that different daytime related operational data sets are provided.

Such data sets for example enable consideration of the environmental conditions over the day or at night or even in the morning or the evening.

Another advantageous solution provides that different location related data sets are provided.

Such different location related data sets take into consideration the specific location of the refrigerant circuit on the globe for example the conditions in several countries or the conditions depending from the distance from the equator.

A further optimized solution of the present invention provides that the controller is provided with the remote access unit.

Such a remote access unit enables for example to remotely change the predefined parameter settings or to remotely monitor the operation of the refrigerant circuit or to remotely discover maintenance of the refrigerant circuit.

Another advantageous embodiment of the inventive controller provides that the controller comprises a processor for controlling said actuators and for performing said optimization process. Further it is of advantage if said controller comprises an input/output unit for operating the actuators and detecting the parameters.

The invention also relates to a method for controlling operation of a refrigerant circuit which refrigerant circuit comprises a compressor arrangement, a heat releasing heat exchanger heating ambient air, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in a storage volume, in particular a refrigerant circuit for transport refrigeration.

According to the invention said method provides cooling of at least one of a first actuator driving said compressor arrangement such that a first parameter detected by said controller meets a predefined first parameter setting associated with said compressor arrangement, a second actuator driving a blower arrangement associated with said heat releasing heat exchanger such that a second parameter detected by said controller meets a predefined second parameter setting associated with said heat releasing heat exchanger and a third actuator driving a blower arrangement associated with said heat absorbing heat exchanger such that a third parameter detected by said controller meets a predefined third parameter setting associated with said heat absorbing heat exchanger.

The advantage of the inventive method has to be seen in the fact that it enables permanent control of at least one actuator.

With respect to further advantages of the aforementioned defined method according to the present invention reference is made to the advantages explained in connection with the various embodiments of the controller explained before.

In particular the inventive method provides controlling at least two of said first actuator, said second actuator and said third actuator according to the respective parameter and the respective parameter settings. An even more advantageous solution provides controlling the first actuator, the second actuator and the third actuator according to the respective parameter detected at the refrigerant circuit and the respective parameter setting.

Preferably, the predefined parameter settings are already optimized with respect to energy efficiency of said refrigerant circuit.

In particular the predefined parameters are optimized with respect to the energy efficiency of the specific refrigerant circuit.

According to the invention defined before the method operates based on the respective predefined parameter settings for controlling the actors.

A more advantageous solution of the present invention provides that said method optimizes the energy efficiency of said refrigerant circuit during operation, which energy efficiency comprises an optimization of the COP and/or the energy consumption of the at least one actuator controlled in order to meet the respective parameter setting by an optimization process comprising varying the respective predefined parameter setting by a step of change in a predefined direction of change increasing or decreasing the respective parameter setting, waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium in the refrigerant circuit, thereafter determining the change of energy efficiency of the refrigerant circuit obtained by said step of change and in case the change of energy efficiency corresponds to an improved energy efficiency the parameter setting amended by said step of change and said direction of change are maintained and stored as predefined parameters for the next variation of the selected parameter setting and in case the change of energy efficiency does not correspond to an improved energy efficiency the parameter setting preceding said step of change is maintained and said direction of change is inverted and stored as predefined parameters for the next variation of said parameter setting.

The advantage of this improved method has to be seen in the fact that the energy optimization is not only achieved by optimized predefined parameter settings but also improved during operation of said refrigerant circuit so that any influence on the refrigerant circuit during operation can be considered for optimizing the operation of said refrigerant circuit.

According to this improved solution at least optimizing the parameter setting for one actuator leads to a certain progress.

Although even one step leads to an improvement of the energy efficiency the efficiency can be further improved by repeating the optimizing process for the respective actuator.

A further improved method according to the present invention provides that said method optimizes the energy efficiency of said refrigerant circuit during operation, which energy efficiency comprises an optimization of the COP and/or the energy consumption of at least two of the actuators controlled in order to meet the respective parameter setting by an optimization process comprising varying a selected one of the predefined parameter settings by a step of change in a predefined direction of change increasing or decreasing the respective parameter setting, waiting for a defined period of time, for example in order to obtain a thermodynamic thermal equilibrium of the refrigerant circuit, thereafter determining the change of energy efficiency of the refrigerant circuit obtained by said step of change, and in case the change of energy efficiency corresponds to an improved energy efficiency the parameter setting amended by said step of change and said direction of change are maintained and stored as predefined parameters for the next variation of said selected parameter setting, and in case the change of energy efficiency does not correspond to an improved energy efficiency the parameter setting preceding said step of change is maintained and said direction of change is inverted and stored as predefined parameters for the next variation of said selected parameter setting.

The advantage of this solution has to be seen in the fact that during operation the energy efficiency of at least two or even all actuators is subject to said optimization process so that the operation of at least two or even more actuators can be optimized.

In general it is possible to optimize the energy efficiency of the at least two or even more actuators at the same time.

Good results can be obtained by optimizing the energy efficiency of at least three or even more, in particular all, actuators of the refrigerant circuit.

However, a simplified process avoids that the optimization process for optimizing the energy efficiency of one actuator is directly influenced by the optimization process for another actuator and in such simplified process it is of advantage if the energy efficiency of only one actuator is optimized at a time whereas the other actuators are controlled according to a constant parameter setting.

Further according to the invention explained before it would be possible to run said optimization process by changing one selected parameter setting by one step of change which is then followed by again changing the same parameter setting before selecting a further parameter setting for change. Such a method could be used if various small steps of change are provided so that it is possible to optimize the energy efficiency by a subsequent chain of steps of change.

Another improved solution provides that according to the optimization process changing of one selected parameter setting by one step of change is followed by a selection of a further parameter setting and changing said further parameter setting by one step of change.

This solution has the advantage that the optimization of one actuator is only changed once and then the next actuator is optimized and thereafter the next actuator is optimized so that the optimization process considers the optimization of all actuators subsequently by one step of change and thereafter may start with the same sequence of energy optimization of said actuators.

In connection with the various embodiments of the inventive method as explained before the parameters and the corresponding parameter setting have not been further specified.

It is of advantage if the parameters and the corresponding parameter settings are temperature based.

This does not necessarily mean that they only refer to temperature measurements, in particular as far as the low pressure side and the high pressure side of the compressor arrangement are concerned a temperature based parameter could also be based on the measurement of the low pressure or the high pressure before and after the compressor arrangement.

However for the sake of simplicity it is of advantage if the parameter settings are based on temperatures detected at the refrigerant circuit. A particular advantageous method provides that the first parameter and the first parameter setting are based on a temperature detected close to a heat absorbing heat exchanger.

It is of particular advantage if said first parameter and said first parameter setting relate to the temperature of the flow of gaseous medium through the heat absorbing heat exchanger, in particular the temperature of return flow of gaseous medium from the storage volume, which is very closely related to the necessary cooling power provided to the cargo.

Another advantageous solution provides that the second parameter and the second parameter setting are based on a temperature indicating the operation of the heat releasing heat exchanger.

Also in this case it might be possible not to directly detect the temperature at the high pressure side of the compressor arrangement by detecting the pressure there.

A particular advantageous method provides that the second parameter and the second parameter setting are based on a temperature difference between said saturated discharge temperature detected at the compressor arrangement and the ambient temperature detected close to the heat releasing heat exchanger.

However such a temperature detection could also be replaced by detecting the warming up of the ambient air flowing through the heat releasing heat exchanger.

Another advantageous solution provides that the third parameter and the third parameter setting are based on the temperature in the storage volume.

There are various kinds of measurements possible to detect the temperature in the storage volume. One advantageous solution provides that the third parameter and the third parameter setting are based on the maximum temperature variation in the space within the storage volumes surrounding the cargo. This method enables some variation in the temperature of surrounding the cargo.

According to the present embodiments of the inventive method there has been no specification of the step width for the respective step of change.

For example the step width of the respective step of change is within the range from 0,1 K to 4 K, in particular in the range from 0,5 K to 2 K.

According to the simplest version of the inventive method the step of change always has the same step width.

However, it could be of advantage if a step width of the step of change is variable between a maximum step width and a minimum step width.

This variation of the step width enables to more precisely approach the optimum of the energy efficiency.

For example an advantageous solution provides that for each parameter setting the optimization process starts with a maximum step width and reduces the step width if the change of energy efficiency is reduced in relation to the change of energy efficiency obtained in the course of the preceding step.

The advantage of this solution has to be seen in the fact that it is possible to approach the optimized energy efficiency in several steps without overrunning the optimum energy efficiency. In order to strictly maintain the chain of cooling a further improved method provides detection, permanently or at least after defined time periods, of a cargo temperature by at least one cargo temperature sensor and compares it to a given maximum admissible cargo temperature and in case the given maximum admissible cargo temperature is reached at least one of the first and second parameter settings are changed in order to reduce the cargo temperature.

According to the previous embodiments of the inventive method the steps of control of the respective actuator have not been specified further.

One advantageous solution provides that the respective actuator is controlled in steps amounting to less than 10 %, even better less than 5 %, of the available control range of said actuator.

An even more preferred solution provides that the respective actuator is continuously controlled within the available control range.

According to the method as explained before the storage of the parameter settings has not been specified further.

One advantageous embodiment of the present method provides that the predefined parameter settings are stored in a memory.

Further according to another optimized method it is provided that several operational data sets, each providing the parameter settings which refer to different environmental conditions are provided.

In particular different daytime related operational data sets are provided.

Another advantageous solution provides different location related data sets in order to have the respective data set available for the respective environmental condition which can be detected by said inventive method. Another advantageous solution of the inventive method provides that the method is remotely accessible, so that in particular the method enables to remotely monitor operation of the refrigerant circuit and/or change the parameter settings used for said method remotely.

Further the invention refers to a refrigerant circuit in particular a refrigerant circuit for transport refrigeration, comprising a compressor arrangement, a heat releasing heat exchanger heating an external medium, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in a storage volume, a first actuator driving said compressor arrangement, a second actuator driving a blower arrangement associated with said heat releasing heat exchanger, a third actuator driving a blower arrangement associated with said heat absorbing heat exchanger, said refrigerant circuit comprising a controller for controlling operation of a refrigerant circuit, according to at least one of the embodiments explained before.

In addition the invention refers to a refrigerant circuit, in particular refrigerant circuit for transport refrigeration being provided with a controller according to one of the various embodiments as defined before.

Further the invention also relates to a refrigerant circuit, in particular a refrigerant circuit for transport refrigeration, controlled according to one of the embodiments of the method as defined before.

Further the invention refers to a storage unit comprising an insulated housing enclosing a storage volume within which temperature sensitive cargo is received and surrounded by a gaseous medium, and a refrigerant circuit comprising a compressor arrangement, a heat releasing heat exchanger heating an external medium, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in the storage volume, a first actuator driving said compressor arrangement, a second actuator driving a blower arrangement associated with said heat releasing heat exchanger, a third actuator driving a blower arrangement associated with said heat absorbing heat exchanger, said refrigerant circuit comprising a controller for controlling operation of a refrigerant circuit, in particular according to at least one of the embodiments explained before.

In particular, advantageous embodiments of the invention comprise the combination of features as defined by the following consecutively numbered embodiments.

1. Controller (120) for controlling operation of a refrigerant circuit (40), which refrigerant circuit (40) comprises a compressor arrangement (54), a heat releasing heat exchanger (62) heating an external medium, a heat absorbing heat exchanger (42) cooling a flow (22) of gaseous medium through said heat absorbing heat exchanger (42) for cooling cargo (16) arranged in a storage volume (14), in particular a refrigerant circuit (40) for transport refrigeration, said controller (120) controlling at least one of a first actuator (132) driving said compressor arrangement (54) such that a first parameter (Pl) detected by said controller (120) meets a predefined first parameter setting (PSI) associated with said compressor arrangement (54), a second actuator (154) driving a blower arrangement (152) associated with said heat releasing heat exchanger (62) such that a second parameter (P2) detected by said controller (120) meets a predefined second parameter setting (PS2) associated with said heat releasing heat exchanger (62) and a third actuator (144) driving a blower arrangement (32) associated with said heat absorbing heat exchanger (42) such that a third parameter (P3) detected by said controller (120) meets a predefined third parameter setting (PS3) associated with said heat absorbing heat exchanger (42). 2. Controller according to embodiment 1, wherein said controller (120) optimizes the energy efficiency (EE) of said refrigerant circuit (40) during operation, which energy efficiency comprises an optimization of the COP and/or the energy consumption of the at least one actuator (132, 154, 144) controlled in order to meet the respective parameter setting (PSI, PS2, PS3) by an optimization process comprising varying the respective predefined parameter setting (PSI, PS2, PS3) by a step of change (AP) in a predefined direction of change (A+, A-) increasing or decreasing the respective parameter setting (PSI, PS2, PS3), waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit (40), thereafter determining the change (AEE) of energy efficiency (EE) of the refrigerant circuit (40) obtained by said step of change (AP) and in case the change (AEE) of the energy efficiency (EE) corresponds to an improved energy efficiency (EE) the parameter setting (PSI, PS2, PS3) amended by said step of change (AP) and said direction of change (A+, A-) are maintained and stored as predefined parameters for the next variation of said selected parameter setting (PSI, PS2, PS3), and in case the change (AEE) of energy efficiency (EE) does not correspond to an improved energy efficiency (EE) the parameter setting (PSI, PS2, PS3) preceding said step of change (AP) is maintained and said direction of change (A+, A-) is inverted and stored as predefined parameters for the next variation of said parameter setting (PSI, PS2, PS3).

3. Controller according to embodiment 2, wherein said optimizing process is repeated.

4. Controller according to embodiment 2 or 3, wherein said controller (120) optimizes the energy efficiency (EE) of said refrigerant circuit (40) during operation, which energy efficiency comprises an optimization of the COP and/or the energy consumption of at least two of the actuators (132, 154, 144) controlled in order to meet the respective parameter (PSI, PS2, PS3), by an optimization process comprising varying a selected one of the predefined parameter settings (PSI, PS2, PS3) by a step of change (AP) in a predefined direction of change (A+, A-) increasing or decreasing the respective parameter setting (PSI, PS2, PS3), waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit (40), thereafter determining the change (AEE) of energy efficiency (EE) of the refrigerant circuit (40) obtained by said step of change (AP) and in case the change (AEE) of energy efficiency (EE) corresponds to an improved energy efficiency (EE) the parameter setting (PSI, PS2, PS3) amended by said step of change (AP) and said direction of change (A+, A-) are maintained and stored as predefined parameters for the next variation of said selected parameter setting (PSI, PS2, PS3), and in case the change (AEE) of energy efficiency (EE) does not correspond to an improved energy efficiency (EE) the parameter setting (PSI, PS2, PS3) preceding said step of change (AP) is maintained and said direction of change (A+, A-) is inverted and stored as predefined parameters for the next variation of said selected parameter setting (PSI, PS2, PS3).

5. Controller according to embodiment 4, wherein said optimization process changes only one predefined parameter setting (PSI, PS2, PS3) at a time.

6. Controller according to embodiment 4 or 5, wherein according to said optimization process changing one selected parameter setting (PSI, PS2, PS3) by one step of change (AP) is followed by again changing the same parameter setting (PSI, PS2, PS3) before selecting a further parameter setting (PS2, PS3, PSI).

7. Controller according to embodiment 4 or 5, wherein according to the optimization process changing of one selected parameter setting (PSI, PS2, PS3) by one step of change (AP) is followed by selecting a further parameter setting (PS2, PS3, PSI) and changing said further parameter setting (PS2, PS3, PSI) by one step of change (AP). 8. Controller according to one of the preceding embodiments, wherein the parameters (Pl, P2, P3) and the corresponding parameter settings (PSI, PS2, PS3) are temperature based.

9. Controller according to embodiment 8, wherein the parameters (Pl, P2, P3) and the parameter settings (PSI, PS2, PS3) are based on temperatures detected at the refrigerant circuit (40).

10. Controller according to one of the preceding embodiments, wherein the first parameter (Pl) and the first parameter setting (PSI) are based on a temperature detected close to the heat absorbing heat exchanger (42).

11. Controller according to embodiment 10, wherein the first parameter (Pl) and the first parameter setting (PSI) relate to the temperature of the flow of gaseous medium (22) through the heat absorbing heat exchanger (42), in particular the temperature of return flow of gaseous medium (28).

12. Controller according to one of the preceding embodiments, wherein the second parameter (P2) and the second parameter setting (PS2) are based on a temperature indicating the operation of the heat releasing heat exchanger (62).

13. Controller according to embodiment 12, wherein the second parameter (P2) and the second parameter setting (PS2) are based on a temperature difference between the saturated discharge temperature detected at the compressor arrangement (54) and the ambient temperature detected close to the heat releasing heat exchanger (62).

14. Controller according to one of the preceding embodiments, wherein the third parameter (P3) and the third parameter setting (PS3) are based on the temperature in the storage volume (14). 15. Controller according to embodiment 14, wherein the third parameter (P3) and the third parameter setting (PS3) are based on the maximum temperature variation in the space within the storage volume (14) surrounding the cargo (16).

16. Controller according to one of the preceding embodiments, wherein a step width of the respective step of change (AP) is within the range from 0,1 K to 4 K.

17. Controller according to one of the preceding embodiments, wherein a step width of the step of change (AP) is variable between a maximum step width and a minimum step width.

18. Controller according to embodiment 17, wherein for each parameter setting (PSI, PS2, PS3) the optimization process starts with a maximum step width and reduces the step width if the change (AEE) of energy efficiency (EE) is reduced in relation to the change (AEE) of energy efficiency obtained in the course of the preceding step.

19. Controller according to one of the preceding embodiments, wherein the controller (120) detects, permanently or at least after defined time periods, a cargo temperature (CT) by at least one cargo temperature sensor (174) and compares it to a given maximum admissible cargo temperature (MACT) and in case the given maximum admissible cargo temperature (MACC) is reached at least one of the first and second parameter settings (PSI, PS2) are changed in order to reduce the cargo temperature (CT).

20. Controller according to one of the preceding embodiments, wherein the respective actuator (132, 154, 144) is controlled in steps amounting to less than 10 % of the available control range of said actuator (132, 154, 144). 21. Controller according to one of the preceding embodiments, wherein the respective actuator (132, 154, 144) is continuously controlled within the available control range.

22. Controller according to one of the preceding embodiments, wherein the predefined parameter settings (PSI, PS2, PS3) are stored in a memory (180) of said controller (120).

23. Controller according to embodiment 22, wherein several operational data sets (ODDN, ODNS) each comprising the parameter settings (PSI, PS2, PS3) which refer to different environmental conditions are stored in the memory (180).

24. Controller according to embodiment 23, wherein different day time related operational data sets (ODD, ODN) are provided.

25. Controller according to embodiment 23 or 24, wherein different location related data sets (ODDS, ODNN) are provided.

26. Controller according to one of the preceding embodiments, wherein the controller (120) detects environmental conditions.

27. Controller according to one of the preceding embodiments, wherein the controller is provided with a remote access unit (190).

28. Controller according to one of the preceding embodiments, wherein the controller (120) comprises a processor (182) for controlling said actuators (132, 154, 144) and for performing said optimization process.

29. Controller according to one of the preceding embodiments, wherein said controller (120) comprises an input/output unit (184) for operating the actuators (132, 154, 144) and detecting the parameters (Pl, P2, P3). 30. Method for controlling operation of a refrigerant circuit (40), which refrigerant circuit (40) comprises a compressor arrangement (54), a heat releasing heat exchanger (62) heating an external medium, a heat absorbing heat exchanger (42) cooling a flow (22) of gaseous medium through said heat absorbing heat exchanger (42) for cooling cargo (16) arranged in a storage volume (14), in particular a refrigerant circuit (40) for transport refrigeration, said method providing controlling at least one of a first actuator (132) driving said compressor arrangement (54) such that a first parameter (Pl) detected at said refrigerant circuit (40) meets a predefined first parameter setting (PSI) associated with said compressor arrangement (54), a second actuator (154) driving a blower arrangement (152) associated with said heat releasing heat exchanger (62) such that a second parameter (P2) detected at said refrigerant circuit (40) meets a predefined second parameter setting (PS2) associated with said heat releasing heat exchanger (62) and a third actuator (144) driving a blower arrangement (32) associated with said heat absorbing heat exchanger (42) such that a third parameter (P3) detected at said refrigerant circuit (40) meets a predefined third parameter setting (PS3) associated with said heat absorbing heat exchanger (42).

31. Method according to embodiment 30, wherein said method optimizes the energy efficiency (EE) of said refrigerant circuit (40), during operation, which energy efficiency comprises an optimization of the COP and/or the energy consumption of the at least one actuator (132, 154, 144) controlled in order to meet the respective parameter setting (PSI, PS2, PS3) by an optimization process comprising varying the respective predefined parameter setting (PSI, PS2, PS3) by a step of change (AP) in a predefined direction of change (A+, A-) increasing or decreasing the respective parameter setting (PSI, PS2, PS3), waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit (40), thereafter determining the change (AEE) of energy efficiency (EE) of the refrigerant circuit (40) obtained by said step of change (AP) and in case the change (AEE) of energy efficiency (EE) corresponds to an improved energy efficiency (EE) the parameter setting (PSI, PS2, PS3) amended by said step of change (AP) and said direction of change (A+, A-) are maintained and stored as predefined parameters for the next variation of said selected parameter setting (PSI, PS2, PS3), and in case the change (AEE) of energy efficiency (EE) does not correspond to an improved energy efficiency (EE) the parameter setting (PSI, PS2, PS3) preceding said step of change (AP) is maintained and said direction of change (A+, A-) is inverted and stored as predefined parameters for the next variation of said parameter setting (PSI, PS2, PS3).

32. Method according to embodiment 31, wherein said optimizing process is repeated.

33. Method according to embodiment 31 or 32, wherein said method optimizes the energy efficiency (EE) of said refrigerant circuit (40) during operation, which energy efficiency comprises an optimization of the COP and/or the energy consumption of the at least two of the actuators (132, 154, 144) controlled in order to meet the respective parameter setting (PSI, PS2, PS3) by an optimization process comprising varying a selected one of the predefined parameter setting (PSI, PS2, PS3) by a step of change (AP) in a predefined direction of change (A+, A-) increasing or decreasing the respective parameter setting (PSI, PS2, PS3), waiting for a defined period of time, for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit (40), thereafter determining the change (AEE) of energy efficiency (EE) of the refrigerant circuit (40) obtained by said step of change (AP), and in case the change (AEE) of energy efficiency (EE) corresponds to an improved energy efficiency (EE) the parameter setting (PSI, PS2, PS3) amended by said step of change (AP) and said direction of change (A+, A-) are maintained and stored as predefined parameters for the next variation of said selected parameter setting (PSI, PS2, PS3), and in case the change (AEE) of energy efficiency (EE) does not correspond to an improved energy efficiency (EE) the parameter setting (PSI, PS2, PS3) preceding said step of change (AP) is maintained and said direction of change (A+, A-) is inverted and stored as predefined parameters for the next variation of said parameter setting (PSI, PS2, PS3).

34. Method according to embodiment 33, wherein said optimization process changes only one predefined parameter setting (PSI, PS2, PS3) at a time.

35. Method according to embodiment 33, wherein according to said optimization process changing one selected parameter setting (PSI, PS2, PS3) by one step of change (AP) is followed by again changing the same parameter setting (PSI, PS2, PS3) before selecting the further parameter setting (PS2, PS3, PSI).

36. Method according to embodiment 33, wherein according to the optimization process changing of one selected parameter setting (PSI, PS2, PS3) by one step of change (AP) is followed by selecting a further parameter setting (PS2, PS3, PSI) and changing said further parameter setting (PS2, PS3, PSI) by one step of change (AP).

37. Method according to one of the preceding embodiments, wherein the parameters (Pl, P2, P3) and the corresponding parameter settings (PSI, PS2, PS3) are temperature based.

38. Method according to embodiment 37, wherein the parameters (Pl, P2, P3) and the parameter settings (PSI, PS2, PS3) are based on temperatures detected at the refrigerant circuit (40).

39. Method according to one of the preceding embodiments, wherein the first parameter (Pl) and the first parameter setting (PSI) are based on a temperature detected close to the heat absorbing heat exchanger (42). 40. Method according to embodiment 39, wherein the first parameter (Pl) and the first parameter setting (PSI) relate to the temperature of the flow of gaseous medium (22) through the heat absorbing heat exchanger (42), in particular the temperature of return flow of gaseous medium (28).

41. Method according to one of the preceding embodiments, wherein the second parameter (P2) and the second parameter setting (PS2) are based on a temperature indicating the operation of the heat releasing heat exchanger (62).

42. Method according to embodiment 41, wherein the second parameter (P2) and the second parameter setting (PS2) are based on to a temperature difference between the saturated discharge temperature detected at the compressor arrangement (54) and the ambient temperature detected close to the heat releasing heat exchanger (62).

43. Method according to one of the preceding embodiments, wherein the third parameter (P3) and the third parameter setting (PS3) are based on the temperature in the storage volume (14).

44. Method according to embodiment 43, wherein the third parameter (P3) and the third parameter setting (PS3) are based on to the maximum temperature variation in the space within the storage volume (14) surrounding the cargo (16).

45. Method according to one of the preceding embodiments, wherein a step width of the respective step of change (AP) is within the range from 0,1 K to 4 K.

46. Method according to one of the preceding embodiments, wherein a step width of the step of change (AP) is variable between a maximum step width and a minimum step width. 47. Method according to embodiment 46, wherein for each parameter setting (PSI, PS2, PS3) the optimization process starts with a maximum step width and reduces the step width if the change (AEE) of energy efficiency (EE) is reduced in relation to the change (AEE) of energy efficiency (EE) obtained in the course of the preceding step.

48. Method according to one of the preceding embodiments, wherein the method provides detection, permanently or at least after defined time periods, of a cargo temperature (CT) by at least one cargo temperature sensor (174) and compares it to a given maximum admissible cargo temperature (MACT) and in case the given maximum admissible cargo temperature (MACC) is reached at least one of the first and second parameter settings (PSI, PS2) are changed in order to reduce the cargo temperature (CT).

49. Method according to one of the preceding embodiments, wherein the respective actuator (132, 154, 144) is controlled in steps amounting to less than 10 % of the available control range of said actuator (132, 154, 144).

50. Method according to one of the preceding embodiments, wherein the respective actuator (132, 154, 144) is continuously controllable within the available control range.

51. Method according to one of the preceding embodiments, wherein the predefined parameter settings (PSI, PS2, PS3) are stored in a memory (180).

52. Method according to embodiment 51, wherein several operational data sets (ODDN, ODNS) each comprising the parameter settings (PSI, PS2, PS3) which refer to different environmental conditions are provided.

53. Method according to embodiment 52, wherein different day time related operational data sets (ODD, ODN) are provided. 54. Method according to embodiment 52 or 53, wherein different location related data sets (ODDS, ODNN) are provided.

55. Method according to one of the preceding embodiments, wherein said method is remotely accessible.

56. Refrigerant circuit (40) in particular a refrigerant circuit (40) for transport refrigeration, comprising a compressor arrangement (54), a heat releasing heat exchanger (62) heating an external medium, a heat absorbing heat exchanger (42) cooling a flow (22) of gaseous medium through said heat absorbing heat exchanger (42) for cooling cargo (16) arranged in a storage volume (14), a first actuator (132) driving said compressor arrangement (54), a second actuator (154) driving a blower arrangement (152) associated with said heat releasing heat exchanger (62), a third actuator (144) driving a blower arrangement (32) associated with said heat absorbing heat exchanger (42), said refrigerant circuit (40) comprising a controller (120) for controlling operation of a refrigerant circuit (40), according to at least one of embodiments 1 to 29.

57. Storage unit (10) comprising an insulated housing (12) enclosing a storage volume (14) within which temperature sensitive cargo (16) is received and surrounded by a gaseous medium (16), and a refrigerant circuit (40) comprising a compressor arrangement (54), a heat releasing heat exchanger (62) heating an external medium, a heat absorbing heat exchanger (42) cooling a flow (22) of gaseous medium through said heat absorbing heat exchanger (42) for cooling cargo (16) arranged in the storage volume (14), a first actuator (132) driving said compressor arrangement (54), a second actuator (154) driving a blower arrangement (152) associated with said heat releasing heat exchanger (62), a third actuator (144) driving a blower arrangement (32) associated with said heat absorbing heat exchanger (42), said refrigerant circuit (40) comprising a controller (120) for controlling operation of a refrigerant circuit (40), according to at least one of embodiments 1 to 29.

Further features and advantages of the present invention are disclosed in the following detailed specification.

In the figures:

Fig. 1 shows a longitudinal sectional view through a storage unit according to the present invention provided with a refrigerant circuit for cooling;

Fig. 2 a side view of one example of an inventive storage unit;

Fig. 3 a front view of the example according to Fig. 2 of the inventive storage unit;

Fig. 4 a front view according to fig. 3 of the inventive storage unit provided with the refrigerant circuit and a control with a front cover removed;

Fig. 5 a schematic representation of the refrigerant components of the refrigerant circuit;

Fig. 6 a schematic representation of the controller with a memory, a processor and an input/output unit and the parameters processed in said controller;

Fig. 7 a diagram of the optimization process during operation of the refrigerant circuit. The invention is explained for example in connection with a storage unit 10 comprising an insulated housing 12 enclosing a storage volume 14 within which temperature sensitive cargo 16 is received and surrounded by a gaseous medium 18, in particular air, which is kept at a defined temperature level for maintaining said cargo 16 in a defined temperature range (Fig. 1).

However the inventive concept can be used in connection with any other environment.

Said storage unit 10 can be for example a storage unit 10 in a supermarket or any other warehouse.

Said storage unit 10 can also be a transportable storage unit, for example of a truck or a trailer (Fig. 2, 3) or a ship or a railway carriage transporting cargo 16 or a conventional container for shipping cargo 16 by truck, railway or ship.

In order to maintain a defined or set temperature range of cargo 16 a flow 22 of said gaseous medium 18 is circulating through volume 14 by starting from a tempering unit 24 as a supply gas flow 26 and entering tempering unit 24 as a return gas flow 28.

The circulating flow 22 of gaseous medium is for example generated by a blower arrangement 32 preferably arranged within tempering unit 24 and tempered by a heat exchange unit 34 arranged within tempering unit 24 (Fig. 1).

Preferably supply gas flow 26 exits from tempering unit 24 in an area close to an upper wall 36 of insulated housing 12 and preferably returns to tempering unit 24 close to a lower wall 38 of insulated housing 12 forming said return gas flow 28. According to a preferred embodiment heat exchange unit 34 comprises a heat absorbing heat exchanger 42 arranged in a refrigerant circuit 40 as shown in Fig. 4 and 5 and in particular further comprises heaters 46 which are for example electric heaters, used for example for defrosting heat absorbing heat exchangers 42.

Tempering unit 24 is for example arranged between lower wall 38 and upper wall 36 of isolated housing 12, in particular on a front wall 48 or a rear wall thereof.

However, tempering unit 24 can also be arranged on upper wall 36 or lower wall 38.

Tempering unit 24 is associated with peripheric unit 52 arranged on an outer side of housing 12 which comprises a heat releasing heat exchanger 62 and a blower arrangement 64 for generating a flow of ambient air 66 through heat releasing heat exchanger 62.

In case of a transportable storage unit 10 peripheric unit 52 further comprises a compressor arrangement 54 and a power source 58 represented by a battery provided and for example integrated in peripheric unit 52, which is supplying electric power over a certain period of time for operating refrigerant circuit independent of a mains power supply network and which is rechargeable by any power supply from time to time.

In case of a stationary unit 10 compressor arrangement 54 can be powered by a mains power supply network for example by use of a battery charger for the battery 58.

Refrigerant circuit 40, as shown in Fig. 4 and 5, comprises a low pressure section 72, in which heat absorbing heat exchanger 42 is arranged and a high pressure section 74, in which a heat releasing heat exchanger 62 is arranged, and the compressor arrangement 54 connected with a suction connection 82 to low pressure section 72 of refrigerant circuit 40, in particular to an outlet 84 of heat absorbing heat exchanger 42, and with a discharge connection 86 is connected to high pressure section 74 of refrigerant circuit 40 which is connected an inlet 88 of heat releasing heat exchanger 62, so that compressor arrangement 54 generates and thereby compresses a flow of refrigerant from low pressure section 72 to high pressure section 74.

Further cooling circuit 40 as shown in Fig. 5 comprises an expansion device 94 being connected directly or indirectly to an outlet 104 of heat releasing heat exchanger 62, for example via an expansion device 102 and a flash gas tank 90 for liquid refrigerant, and expansion device 94 is connected with its outlet 106 to an inlet 108 of heat absorbing heat exchanger 42.

Gasous refrigerant collected above a bath of liquid refrigerant in receiver 90 is expanded via expansion device 92 to an intermediate pressure and guided to intermediate pressure connection 96 of two stage compressor arrangement 54. Electric drive 132, for example an electric motor, of compressor arrangement 54 is cooled by refrigerant from heat absorbing heat exchanger 42 before being compressed to high pressure at discharge connection 86.

However, as an alternative electric drive 132 can also be cooled by refrigerant supplied via intermediate pressure connection 96 or compressed refrigerant at high pressure before heaving through discharge connection 86.

A controller 120 associated with cooling circuit 40 is for example connected to a pressure sensor 122 associated with low pressure section 72 and/or a temperature sensor 124 associated with low pressure section 72 and also connected to a pressure sensor 126 associated with high pressure section 74 and/or a temperature sensor 128 associated with high pressure section 74. Further controller 120 is for example connected to a variable frequency converter 130 powering variable frequency electric drive 132, being for example a motor, representing a first actuator for driving compressor arrangement 54 and to a drive 134 for adjusting expansion device 94.

Drive 134 is an electric drive representing another possible actuator for adjusting expansion device 94 which is for example an expansion valve.

Further adjusting drive 136 is representing another possible actuator for adjusting expansion device 92.

In addition adjusting drive 138 is representing another possible actuator for adjusting expansion device 102.

Said cooling circuit 40 is in particular operated by said controller 120 in a heat transfer mode in which compressor arrangement 54 is driven speed controlled by means of variable frequency converter 130 for powering electric drive 132 and said expansion device 94 is controlled in accordance with the amount of heat to be transferred from said heat absorbing heat exchanger 42 extracting heat from said return gas flow 28 in order to obtain a cooled supply gas flow 26 blown into storage volume 14 to heat releasing heat exchanger 62 releasing heat into the flow of ambient air 66 depending on the temperature of the flow of ambient air 66.

In order to maintain a defined circulating flow of ambient air, heat releasing heat exchanger 62 is associated with a blower arrangement 152 driven by electric drive 154 representing a second actuator, for example an electric motor, which is controlled by controller 120.

The operation of heat releasing heat exchanger 62 is monitored by a temperature sensor 156 detecting the temperature of ambient air and for example in addition a temperature sensor 158 detecting the temperature of exiting air. The operation of heat releasing heat exchanger 62 can be further monitored by a pressure sensor 162 and/or a temperature sensor 164 detecting the refrigerant output by heat releasing heat exchanger 62.

Said pressure sensor 162 and said temperature sensor are connected to controller 120.

In order to maintain a defined flow 22 of gaseous medium 18 heat exchanger unit 34 is associated with blower arrangement 32 driven by an electric drive, for example by a frequency controlled electric drive 144, in particular an electric motor, representing a third actuator which is controlled by controller 120.

In addition an improved monitoring of the operation of heat exchanger unit 34, in particular heat absorbing exchanger 42, is possible by controller 120 if a temperature sensor 146 is provided detecting the temperature of return gas flow 28 and a temperature sensor 148 is provided detecting the temperature of supply gas flow 26.

In addition for monitoring the operation of refrigerant circuit 40 by controller 120 refrigerant circuit 40 is provided with a pressure sensor 166 and/or a temperature sensor 168 for refrigerant entering compressor arrangement 54 at intermediate pressure connection 96 after expansion by expansion device 92.

Further a temperature sensor 169 enables detection of the temperature at the exit of flash gas tank 92. In order to obtain information of the temperature of the cargo 16 itself a cargo space sensor 172 (Fig. 1, 5) within storage volume 14 is provided, for example in maximum distance from tempering unit 24 and/or at least one cargo temperature sensor 174 is attached to the cargo 16 itself, in communication, in particular wireless communication, with controller 120.

Controller 120 in particular comprises a processor 182 associated with a memory 180 (Fig. 6).

Controller 120 is provided with a user panel 170 enabling operational control and for example access the data in particular also input of the data stored in memory 180.

In particular an input/output unit 184 of controller 120 is associated with processor 182 which enables operation of actuators 132, 154, 144, and if necessary further actuators 134, 136, 138 and detection of sensor values of all temperature sensors 124, 128, 146, 148, 156, 158, 164, 168, 172, 174 and pressure sensors 122, 126, 162, 166 in refrigerant circuit 40 (Fig. 6) for detecting parameters used in order to control for example actuators 132, 154, 144 and if necessary further actuators 134, 136, 138.

In addition controller 120 comprises a time signal receiver 186 and a GPS receiver 188.

For remote control of refrigerant circuit 40, in particular for operational control of refrigerant circuit 40 and/or for changing one or more of parameter settings PS1,PS2, PS3 and MACT and/or daytime and/or location controller 120 is provided with a remote access unit 190.

In memory 180 at least one predefined operational data set of parameter settings PSI, PS2, PS3, is stored each parameter setting PSI, PS2, PS3 being associated with one of the actuators 132, 154, 144, is stored. For example a first parameter setting PSI for the first actuator 132, a second parameter setting PS2 for the second actuator and a third parameter setting for the third actuator 144.

Since energy optimized parameter settings PSI, PS2, PS3 for an optimized operation of the refrigerant circuit 40 depend on the environmental conditions in case if for example noise is constraint of storage unit 10 it is of advantage to store several different operational data sets ODDN, ODNN, ODDS, ODNS for different environmental conditions of the storage unit, e.g. one operational data set ODD for the day, one operational data set ODN for the night and/or different operational data sets for different local environments on the globe where the storage unit 10 is located when in operation, for example depending on the degree of latitude, e.g. for example north or south of a selected degree of latitude, which would lead to operational datasets ODDN and ODNN for the north and ODDS and ODNS for the south.

The first parameter setting PSI for the first actuator 132 for example is related to the temperature associated with the heat absorbing heat exchanger 42, in particular is related the temperature of the flow of gaseous medium through the heat absorbing heat exchanger 42 detected by temperature sensors 146, 148.

This first parameter setting PSI will be compared with a first parameter Pl by processor 182 which first parameter Pl corresponds to the temperature detected by one of or both temperature sensors 146, 148 in order to control operation of the first actuator 132.

Alternatively or in addition it would also be possible to use the pressure or temperature at the low pressure section 72 detected by pressure sensor 122 and/or temperature sensor 124 as the first parameter Pl. The second parameter setting PS2 for the second actuator is associated with heat releasing heat exchanger 62 for example related to the temperature indicating the operation of heat releasing heat exchanger 62, in particular the temperature difference between the saturated discharge temperature at discharge connection 86 of compressor arrangement 54 and the ambient temperature of heat releasing heat exchanger 62.

This second parameter setting PS2 will be compared with a second parameter P2 by processor 182 and the second parameter P2 is detected either by pressure sensor 126 or temperature sensor 128 and with the ambient temperature of heat releasing heat exchanger 62 detected by temperature sensor 156 being subtracted in order to control the second actuator 154.

The temperature difference should for example remain in a range extending from 6 K to 13 K preferably 7 K to 12 K for maintaining efficient operation of the heat releasing heat exchanger 62.

The third parameter setting PS3 for the third actuator 144 is associated with the temperature within the storage volume 14 and for example is related to the temperature in the storage volume 14 and in particular related to the allowed temperature variation of the flow 22 of gaseous medium 18 in storage volume 14 surrounding cargo 16.

This third parameter setting PS3 will be compared with a third parameter P3, by processor 182, and the second parameter P2 is for example detected by one or both temperature sensors 172, 174 provided in the storage volume 14 or attached to cargo 16 for controlling the third actuator 144.

Preferably the allowed maximum temperature variation is in a range extending from about 1 K to 3 K for chilled cargo 16 or in a range extending from about 1 K to 5 K for frozen cargo 16. Further in memory 180 a maximum admissible cargo temperature MACT for cargo 16 is stored which should never be overrun in order to maintain a cargo cool chain any time during storage, in particular during transport.

In order to keep the cargo 16 below said maximum admissible cargo temperature MACT controller 120 via input/output unit 184 detects the cargo temperature CT by cargo sensor 174 and in case the detected temperature reaches the maximum admissible cargo temperature MACT the parameters settings PSI and PS2 of first and second actuators 132, 154 are amended in order to reduce the temperature of gaseous medium 18 in storage volume 14.

When starting operation of refrigerant circuit 40 processor 182 of controller 120 will determine the appropriate operational data set ODDN, ODNN, ODDS, ODNS by determining the environmental conditions by time and GPS data and load the corresponding predetermined parameter settings PSI, PS2, PS3 for controlling operation of said refrigerant circuit 40 at the given parameter settings PSI, PS2, PS3.

During control of operation controller 120 will permanently or after certain determined time periods detect the cargo temperature CT at cargo sensor 174 by input/output unit 184 and - if necessary - the processor 182 will overrule and redefine the parameter settings PSI and PS2 if the maximum admissible cargo temperature MACT is reached.

In addition processor 182 will start a process for optimization of the energy efficiency of the operation of refrigerant circuit 40 in order to reduce electric power consumption for increasing to time periods after which charging of battery 58 is necessary.

Controller 120 operates refrigerant circuit 40 as follows. When started control 120 with processor 182 runs refrigerant circuit 40 with its actuators 132, 154, 144 which enable operation of refrigerant circuit 40 according to loaded predefined temperature settings PSI, PS2, PS3 stored in memory 180.

These predefined temperature settings PSI, PS2, PS3 have been determined by an optimizing process under predetermined operational conditions for example by the supplier of controller 120.

The invention is primarily focusing on control of actuators 132, 154, 144 having the highest power consumption.

For example control 120 controls as a first actuator electric drive 132 for compressor arrangement 54.

Further for example control 120 controls as a second actuator electric drive 154 driving blower arrangement 152 associated with heat releasing heat exchanger 62.

In addition control 120 controls as a third actuator 144 electric drive 144 driving blower arrangement 32 associated with heat absorbing heat exchanger 42 in order to control a defined flow 22 of gaseous medium 18 therethrough.

For the sake of simplicity control of refrigerant circuit 40 is explained limited to the first 132 second 154 and third 144 actuators however as explained before there are further actuators such as for example adjusting drive 134 for adjusting expansion device 94 or adjusting drive 136 for adjusting expansion device 92 which can be controlled in accordance with corresponding parameter settings referring to a certain temperature or a certain pressure. After the refrigerant circuit 40 with the first 132 second 154 and third 144 actuator 156 is controlled by detecting a first parameter Pl for monitoring operation of compressor arrangement 54, a second parameter P2 for monitoring operation of said heat releasing heat exchanger 62 and a third parameter P3 for monitoring operation of said heat absorbing heat exchanger 42 operating said first 132, second 154 and third 144 actuators such that said parameters Pl, P2, P3 meet their respective parameter settings PSI, PS2, PS3.

In order to improve the operation conditions, processor 182 of control 120 starts a process for optimizing the energy efficiency EE of the operation of refrigerant circuit 40, which energy efficiency can be determined based on the COP and/or the energy consumption of operating actors 132, 154, 144 of refrigerant circuit 40.

The COP for example can be calculated according to the publication :

Compressors and condensing units for refrigeration - Performance testing and test methods - Part 1, Refrigerant compressors

In particular chapter 4.1.5.2 for example equation of European Standard, CEN/TC 113, Date 2014-04, prEN 13 771-1 :2014.

Energy consumption can for example be, by detecting the electric power consumption.

According to this process (Fig. 7) in process step 192 one of the actuators 132, 154 and 144 is selected, for example first actuator 132. First actuator 132 at this time is controlled such that parameter Pl meets the predetermined first parameter setting PSI stored in memory 180 and in process step 194 the first parameter setting PSI is changed in a predetermined direction of change A+ or A- also stored in memory 180 increasing or decreasing the respective stored parameter setting PSI by a step of change AP, for example by a direction of change A-.

After the change of parameter setting PSI by the step of change AP algorithm in process step 196 waits for a certain time period in order to allow refrigerant circuit 40 to reach its thermodynamic equilibrium stage.

Thereafter the algorithm in process step 198 detects the change AEE in energy efficiency EE of the overall operation of refrigerant circuit 40 e.g. for example by calculating the change of the COP and/or of the energy consumption.

If in process step 200 it is recognized that the change AEE in energy efficiency EE is positive, which means the energy efficiency EE is improved, the algorithm in process step 202 maintains the new parameter setting PSI' corresponding to the previous parameter setting PSI amended by the step of change AP and also maintains the direction of change A- and in process step 204 updates the memory 180 with this new parameter setting PSI' and the direction of change A-.

If however in process step 200 it is recognized that the detected change AEE in energy efficiency EE is negative, which means the energy efficiency EE has decreased, the algorithm in process step 206 maintains the previous parameter setting PSI and reverses the previous direction of change A- to Anand in process step 208 updates memory 180 with the parameter setting PSI and the reversed direction of change A+. After process steps 204 or 208 change of parameter setting PSI is terminated and the updated setting, e.g. either PSI' and direction of change A-, or e.g. PSI and direction of change A+, are stored for the next process for optimization of said actuator.

Then the algorithm in process step 210 selects the next actuator, for example actuator 154, and the next parameter setting, for example parameter setting PS2, and to this parameter setting PS2 process steps 200, 202, 204, 206, 208 are applied as described before.

Therefore second parameter setting PS2 is changed by a step of change AP in direction of change A- in process step 194 then in process step 196 the algorithm waits for the defined time period in order to achieve thermodynamic equilibrium and thereafter in process step 198 the algorithm detects the change AEE in energy efficiency EE obtained by a said step, then the decisions according to steps 200, 202 and 206 are made and change of parameter setting PS2 is terminated by process step 204 or 208.

Thereafter in process step 210 the next actuator and the next parameter setting PS are selected and the algorithm operates according to the same process steps as explained before.

After the parameter settings PSI, PS2, PS3 of all actuators 132, 154, 144 have been changed by one step of change AP the algorithm starts again for example with the first one of the parameter settings PSI, PS2, PS3.

According to an alternative algorithm steps 194 to 204 or 206 can be repeated for the same parameter setting once or even more often if it seems advantageous to change one and the same parameter settings PS several times, for example if small values for AP are used. According to another alternative algorithm the step width can be varied, for example by starting with a predefined step width AP and reducing the step width in case in process step 200 it is recognized that the detected change AEE in energy efficiency EE is negative and then in process step 208 the previous parameter setting PS, the reversed direction of change A+ and the reduced step width are stored for the following optimization of this parameter setting PS.