Method for analyzing, monitoring, optimizing and/or comparing energy efficiency in a multiple compressor system

Abstract

The present invention provides a method for analyzing, monitoring, optimizing and/or comparing energy used for producing a unit of mass or volume of compressed gas (Specific Energy Consumption) in relation to a common output flow in a multiple compressor system, said method comprising: —collecting measured data of common output flow and energy/power use and calculating the specific energy consumption in the multiple compressor system, —identifying which data points of measured specific energy consumption that affiliate to a certain compressor or compressor combination in the multiple compressor system and/or operating mode(s) of the multiple compressor system; and —plotting the data points of measured specific energy consumption that affiliate to a certain compressor or compressor combination in the multiple compressor system and/or operating mode of the multiple compressor system and marking affiliation of said data points to the certain compressor or compressor combination and/or operating mode.

Claims

1. A method for analyzing, monitoring, optimizing and/or comparing energy used for producing a unit of mass or volume of compressed gas (Specific Energy Consumption) in relation to a common output flow in a multiple compressor system, said method comprising: collecting measured data of common output flow and energy/power use and calculating the specific energy consumption in the multiple compressor system, identifying which data points of the specific energy consumption that affiliate to a certain compressor or compressor combination in the multiple compressor system and/or operating mode(s) of the multiple compressor system; plotting the data points of the specific energy consumption that affiliate to a certain compressor or compressor combination in the multiple compressor system and/or operating mode of the multiple compressor system and marking affiliation of said data points to the certain compressor or compressor combination and/or operating mode, wherein an ideal specific energy consumption curve(s) is plotted and each ideal specific energy consumption curve is complemented with another curve visualizing the working limit for each certain compressor or compressor combination in the multiple compressor system, and wherein the curves together form a working area for each certain compressor or compressor combination in the multiple compressor system and adapting the multiple compressor system based on the data points of the specific energy consumption.

2. The method according to claim 1, wherein plotting the data points is performed in a chart of specific energy consumption vs common output flow.

3. The method according to claim 1, wherein said method also comprises from a the first compressor, constructing an ideal specific energy consumption curve in the first compressor as a function of the output flow of the first compressor; and from a first compressor and a second compressor, calculating a combined ideal specific energy consumption curve in the first compressor and the second compressor as a function of the combined output flow of the first compressor and the second compressor, and wherein the method comprises structuring calculated data to be visualized in ideal specific energy consumption curves, to analyze, monitor, optimize and/or compare with measured data for a corresponding multiple compressor system.

4. The method according to claim 1, wherein constructed curves and/or measurement data points in the plots are linked to different compressor combinations, operation modes and/or transitions between different operation modes or compressor combinations and where the links are visualized by markings such as front- or background colors, symbols, separation into different sub-plots or similar to enable analysis of the effects of transitions and operating combinations in the multiple compressor system.

5. The method according to claim 3, wherein the method involves constructing and visualizing the ideal specific energy consumption curve(s) for one or more fixed system reference pressure(s) and/or inlet conditions.

6. The method according to claim 3, wherein the method involves constructing and visualizing one or several ideal specific energy consumption curve(s) for compressor combination(s), in any combination(s).

7. The method according to claim 3, wherein the method involves constructing and visualizing one or several ideal specific energy consumption curves(s) for compressor combination(s), in any combination(s), and wherein at least one combination is based on combining adjustable flow ranges of individual compressors.

8. The method according to claim 3, wherein the calculation of ideal specific energy consumption curves is based on combining non-adjustable flow ranges and adjustable flow ranges for individual compressors separately to form one single virtual compressor.

9. The method according to claim 3, wherein the ideal specific energy consumption curve(s) is calculated with specific energy consumption set as a constant or close to constant within a compressor(s) regulating flow range and where ideal specific energy consumption is calculated from a constant power use for a compressor(s) non-regulating flow range.

10. The method according to claim 3, wherein the ideal specific energy consumption curve(s) is adjusted for efficiency variations within a regulating flow range compared to a constant specific energy consumption and/or wherein the ideal specific energy consumption curve(s) is calculated employing design or performance curves of tho individual compressors.

11. The method according to claim 1, wherein data points outside of the working area(s) for each certain compressor or compressor combination in the multiple compressor system are identified and/or indicated as measuring errors or system or equipment faults.

12. The method according to claim 1, wherein the working limit curve is constructed and plotted as an ideal specific energy consumption curve independent of regulating capabilities of any of the compressors involved in the compressor combination.

Description

DETAILED DESCRIPTION OF THE DRAWINGS

(1) Below, the drawings are described.

(2) In FIG. 1, is shown a schematic view of a multiple compressor system with common output flow. In this case there are three different compressors in the system. The compressors are regulated individually, and the total input power is divided accordingly over the different compressors. A multiple compressor system provides one common output flow regardless if this is directly in one mixing point subsequently to the compressors or if this is e.g. after a common expansion tank.

(3) The compressors may be connected to a ring-line or distribution line and the flow may be split into different end-usage areas in a way that there is no single measurement point where all the combined flow from all compressors passes. The combined end-usage is then the common output flow. The common output flow must then be measured as an aggregated flow from individual measurements throughout the system and/or over the distribution network.

(4) Any compressor system where there at some point in the system is an interconnection between the compressors enabling a cross-flow can be considered as a multi compressor system with a common output flow. It is also common that the air flow from the compressors may be directed in such a way that there are losses of air from certain compressors from e.g. air dryers that are only connected to part of the compressors. The losses occurred in such a process will then be a part of the total output flow (and/or compensated for in the performance adjustments). Such losses can either be measured or calculated from models and/or other parameters such as pressure. One such example is compressor units sold with an integrated dryer unit which may be connected into a system with compressors with external air dryers and where the air from the two types is mixed after dryers.

(5) In FIG. 2 is shown further embodiments according to the present invention. In the different cases the profiles in the regulating flow range for a certain compressor set-up are adjusted in accordance as shown in the figures of FIG. 2. The adjustment may be performed with one or more linear compensations, with a mathematically adjusted curve or with a curve based on some decided points (see the last alternative).

(6) With reference to FIG. 2, there are several parameters which is of interest to calculate or know. Firstly, specific energy consumption (SEC) at 100% output flow. Secondly, specific energy consumption at an optimal output flow, i.e. the minimal specific energy consumption, as well as the optimal output flow in percentage. Finally, specific energy consumption when the regulation starts, as well as the output flow, in percentage, when the regulation starts. If more data is available, this is of course beneficial. The upper curve to the left is in the shape of quadratic curve, and may e.g. be any type of n-degree polynomial curve. Also other types are possible, such as Gauss curve, Bézeir curve or other form of parametric curve, cos- or sinus curve. The curve down to the left is two first order curve. In this case, any type of piecewise functions where the function is divided into different flow ranges. Finally, the curve down to the right is also a variant to a piecewise function where an assumption has been made so that the flow ranges are about the same size. This is one possible assumption, but many others are also possible.

(7) In FIG. 3 is shown the system measurement data of specific energy use and common output flow classified into different compressor combinations which are visualized with different symbols in the plot. The combined ideal specific energy consumption (SEC) curves according to one embodiment of the present invention that are matching the plotted compressor combinations has also been plotted into the graph. As may be noted, the first curve to the left is the ideal specific energy consumption curve of one compressor. This “first” compressor may be any compressor of the multiple compressor system, when being the only compressor in operation. As described above, the ideal specific energy consumption curve of this first compressor is calculated as a function of the output flow of the first compressor, and then plotted. The next curve is a combined ideal specific energy consumption curve of a first compressor and a second compressor, in a general context this could be any two compressors of the system. Accordingly, the last curve shows the combined ideal specific energy consumption of three compressors in sequential operation, i.e. 1, 1 plus 2, 1 plus 2 plus 3 as derived from the combinations used in the plotted measurement data. This example is of two non-regulating screw compressors and one frequency regulated screw compressor. The measured data points are from 4 different compressor combinations. I.e. 1 compressor, 2 compressors, 3 compressors, and 4 compressors are plotted with different symbols and are overlaid with the four corresponding ideal specific energy consumption curves matching the different compressor combinations. It should be noted that also curves of unloaded combinations may be constructed and visualized as well as measurement data for unloaded combinations may be marked with different symbols. As notable, most real measurement data points are not on a (SEC) curve that would provide the lowest possible specific energy consumption for a certain flow. Furthermore, many measurement points are not directly on or in close proximity to the (SEC) curves but are present at a higher specific energy consumption than if they would have been on the ideal (SEC) curve which further shows improvement opportunities for operating this specific multiple compressor system in a much more efficient way than it is performed today. The figure shows that the system as measured operate at close to optimal efficiency only in the highest flow range and while operating four compressors.

(8) In FIG. 4 is shown a model according to one specific embodiment of the present invention. The non-regulating flow ranges and regulating flow ranges in relation to flow for the individual compressors are shown firstly. According to one embodiment of the present invention, the theoretical operation model is based on combing non-adjustable flow ranges and adjustable flow ranges for individual compressors separately to form one single virtual compressor. This single virtual compressor is shown below where one may see how the different parts of the individual compressors have been added to form the virtual compressor. As such, this embodiment provides one single virtual compressor with one non-regulating flow range and one regulating flow range in relation to the total flow as a model to use when evaluating a multiple compressor system. The FIG. 4 shows the regulating flow ranges of two compressors being modelled in sequential order so that only one compressor is regulating at a time and the next compressor starts regulating as soon as the previous compressor reaches its regulating flow range limit. The regulating flow ranges of the combined compressor may also be modelled as regulating in parallel over the common regulating flow range or a combination of sequential and parallel. Compressors regulating in parallel would be simultaneously regulating throughout their entire common regulating flow range.

(9) In FIG. 5 is shown one specific embodiment according to the present invention, in which at least two ideal specific energy consumption (SEC) curves are aggregated into one common reference curve (called composite curve in FIG. 5). Moreover, real measurement data from two different compressor combinations has been plotted into the graph and based on this the inefficiency measured in delta specific energy consumption at a certain system flow may be calculated. The individual ideal efficiency curves may also be adjusted before aggregation based on reduced regulating flow ranges taking system dynamic time constraints into consideration.

(10) In FIG. 6 is shown three plots of ideal specific energy curves from a three compressor system comprising of one VSD screw compressor and two load/unload type of screw compressors all with similar sizes. The two upper plots show SEC (kWh/Nm.sup.3) vs common output flow (Nm.sup.3/min) and the bottom plot show the systems regulating capacity for different common output flows.

(11) The uppermost plot shows the available regulating ranges of the different compressor combinations (1, 1 plus 2, 1 plus 2 plus 3) and the non-usable part if the regulating range is marked separately. The non-usable part of the regulating range has been set by taking account of the systems desired capability in handling fast flow changes as well as the needed start-up time for an individual compressor.

(12) The middle plot shows the aggregated ideal specific efficiency curve constructed from the three separate ideal specific energy curves for the three different compressor combinations. The non-usable part of each curves regulating range has been excluded while performing the aggregation. The bottom plot shows a visualization of where the regulating gaps for the system is present based on the aggregated curve shown in the middle plot. 100% on the y-axis show that the system has full regulating capability and thus can operate efficiently and stable. 0% on the y-axis show that the system lack regulating capability for those flow ranges and thereby indicates the position of the systems regulating gaps.

(13) In FIG. 7 is shown a schematic view of a method and the steps therein according to one embodiment of the present invention.

(14) In FIG. 8 is shown five separate linked plots for a four compressor system according to one embodiment of the invention where the individual measurement points for each detected compressor combination is identified with a unique symbol. The upper plot shows measured SEC vs. common output flow, the lower left plot shows system pressure vs. common output flow and the lower right triplet plots show individual compressors energy usage vs. the common output flow for three of the system's compressors.

(15) In FIG. 9 the pressure vs common output flow for a multi compressor system is plotted and the individual measurement points are identified in two different categories depending on whether all compressors are working within the regulating range or if one or more compressors are operating outside their regulating range, i.e. with an open blow-off valve and thus in a less energy efficient state. The plot is used as a supplementary plot to other plots as described in the description herein and the same classification and marking can be used in any other plot such as specific energy vs. common output flow. It can also be part of a larger multi-dimensional (3D) plot.

(16) In FIG. 10 three plots are shown where each plot corresponds to an individual compressors energy usage vs. common output flow. The charts are segmented in the Y-axis direction and marked in different areas depending on the compressor operating mode present in the specific energy usage range.

(17) The areas used in the three plots are “production” which corresponds to the compressor contributing to the common output flow, “Unload”, where the compressor is in unloaded state and does not provide any contribution to the common output flow and finally “Off”, where the compressor is completely shut down. There are many different options of area classifications that can be used such as separation of the production range into smaller segments and/or presentation of expected IGV position.

(18) In FIG. 11 it is visualized how a sub-set of the collected measurement data is selected in a pressure vs. common output flow plot through the use of a polygon selection according to the present invention and where the corresponding measurement points to the selected ones are highlighted in a secondary plot. This selection procedure and highlighting can be used on any of the in the invention mentioned plots and the highlighting can be implemented in any of the plots and in any number of plots simultaneously. The selection can also be further refined through selecting an even smaller sub-set of the previous selected points using the same polygon tool or by selecting individual measurement points.

(19) In FIG. 12 there is shown plots of a multiple compressor system in accordance with FIG. 3 and in this case comprising 3 compressors in 3 different compressor combinations. In these cases, all the created ideal specific energy consumption curve(s) are complemented with another type of curve. This complemented curve sets the working limit for each certain compressor or compressor combination in the multiple compressor system. As may be seen in extra Fig. A, these curves are plotted using the maximum flow of each compressor combination and from this plotting a curve assuming none if the compressors used in the combination is using any of their regulating capacity whereas the energy use remains constant or close to constant for any flow. The curve is thereby constructed in the same way as an ideal curve for a compressor combination that does not include any compressors with regulating capabilities. In FIG. 12 it is shown that a working area is created by combining an ideal specific energy consumption curve with this complemented working limit curve. As such, data points found outside of the working area may be identified and indicated as measurement errors and/or system/compressors faults.

(20) Based on the above, according to one specific embodiment of the present invention, the ideal specific energy consumption curve(s) is plotted and each of them is complemented with another curve visualizing the working limit for each certain compressor or compressor combination in the multiple compressor system, and wherein the curves together form a working area for each certain compressor or compressor combination in the multiple compressor system. Furthermore, according to yet another specific embodiment of the present invention, data points outside of the working area(s) for each certain compressor or compressor combination in the multiple compressor system are identified and/or indicated as measuring errors or system or equipment faults. Moreover, and as hinted above, according to yet another embodiment of the present invention the working limit curve is constructed and plotted in the same way as an ideal specific energy consumption curve but assuming that none of the compressors involved in the compressor combination is using any of their regulating capabilities.

CONCLUSIONS

(21) The present invention provides a model for analyzing an existing multiple compressor system to find the optimal operation mode based on real measurement data.

(22) The method according to the present invention may be directed to different types of usage. For instance, the method may be directed to regulation of a multiple compressor system as such. Moreover, the operation model according to the present invention may also be used only as a simulation model or mathematical model for analyzing an existing multiple compressor system. By use of the model as such, a multiple compressor system may be evaluated and improvements may be implemented. Furthermore, this also implies that the operation model according to the present invention may be used as a type of virtual multiple compressor. Regardless, the main direction of the present invention is a modelling method, implemented directly into a multiple compressor system or used indirectly off-site only on collected data.

(23) The present method is directed to visualize ideal specific energy consumption curves for different compressor combinations and operating modes in the multiple compressor system. This is different when comparing to other existing systems today. Moreover, another clear difference is the fact that the present invention provides both disaggregation and visualization of measurement data into different compressor combination, operating modes, individual compressor operation and system pressure as well as direct comparison of the measurement data with simulated system performance. Other known methods, are limited to comparison only with static reference levels of specific energy usage and/or time average/accumulated key performance indicators, whereas the invention enables the use of key performance indicators measuring efficiency while at the same time taking ideal system performance into consideration thereby providing a much more accurate measurement and base for further analysis. Other known methods are also limited to plotting the systems measured or calculated values in time based plots or in some cases in flow profiles (i.e. histograms), and thereby not providing the analyzing user with any associations between the measured data and the systems operational mode and thereby severely limiting the possibility to find the causes of problems and in many cases to identify the existence of the problems or inefficiencies altogether. The possibility to analyze the system in a time independent manner enable analysis over long periods of time as well as the possibility to compare with an operational model that is directly associated to the data to provide the user with advantage over other available analyzing methods.

(24) To summarize, the method according to the present invention has several advantages in comparison to existing analysis methods for compressed air systems and other multiple compressor systems. Firstly, it provides disaggregation and association of the measured data into unique compressor combinations and system operating modes, enabling identification of problems as well as visualizing the cause. Secondly, real data may be compared directly to a simulation model matching the associated data enabling identification of improvement potential as well as possible improvements to the system set-up, control or operation. Moreover, the present invention provides the tool for a full analysis of an existing multiple compressor system without the need of deep expert knowledge and skill through indication and visualization of both inefficient or unstable operation as well as means to visualize and find the causes and also indicate the possible solution by comparing with simulation of optimal system operation.

(25) To give a guidance of the possible level of improvement when using the present invention, a possible value of specific energy consumption as kWh/Nm.sup.3 at around 0.09 or 0.1 in the widely used pressure band of 6-8 bar may be obtainable using large size screw or turbo compressors, which may be compared to a level of anywhere from 0.15 and upwards which is a common level for a reference multiple compressor system running without proper optimization and/or regulating capability. To lower the specific energy consumption value of this magnitude is of course of great interest. To simplify the process so that non-expert users can perform such system optimizations as well as providing expert users tools to find further earlier unrealized optimization potential is also of great value.

(26) As described above, measured data of common output flow and energy/power use can be collected using different types of sensors, e.g. the power of the compressor can be measured by measuring current and measuring voltage, if not being set at a constant value. By continuously collecting data related to the common output flow of energy/power use as well as determining, or in other words calculating, the specific energy consumption in the multiple compressor system, it is made possible over time to collect data that can be used for increasing the understanding of how to control the system in an energy efficient manner.

(27) Further, it can be identified which data points of measured specific energy consumption, collected by using the sensors, that affiliate to a certain compressor or compressor combination in the multiple compressor system and/or operating mode(s) of the multiple compressor system. Put differently, a specific data point can be associated with the compressor or compressor combination used when the specific data point was collected as well as the operating mode(s) the compressor or compressor combination was set to when the data point was collected. Information of the compressor or the compressor combination used when collecting the data point can be retrieved from the compressors themselves or alternatively from a control unit connected to and controlling the compressors.

(28) Time stamps may be used for affiliating the data points to the compressor or compressor combination as well as the operating mode. When measuring the common output flow and energy/power a time stamp may be added to the measured data. In a similar manner, a compressor or compressor combination being used, as well as the operating mode being used, may be logged with a time stamp. By having time stamps both for the measured data and the compressor and compressor combination, as well as operating mode(s), it is possible to affiliate these to each other.

(29) Having data points collected over time from the compressors and having these affiliated with different compressors or compressor combinations, and also to different operating mode(s) it is made possible to analyze, monitor, optimize or compare different alternatives for producing a unit of mass or volume of compressed gas (Specific Energy Consumption) in terms of energy used. This can be achieved in different ways. For instance, data points related to a specific alternative may be color coded such that when the data points are presented to the user, sometimes also referred to the operator, the different alternatives can be easily kept apart. Still an option is to configure a computer, or a control unit, such that based on the data points a most energy efficient can be chosen and the multiple compressor system adapted accordingly.

(30) The approach above may be described as below:

(31) A method for controlling a multiple compressor system, wherein the multiple compressor system comprises a number of compressors together providing a common output flow, said method comprising

(32) receiving power/energy usage measurement data from a number of sensors connected to the number of compressors, respectively, over a period of time such that a power/energy usage measurement data set covering several compressor combinations and/or operating modes is provided,

(33) receiving, in parallel with receiving the power/energy usage measurement data, system operation data related to operational compressor combination(s) and operating mode(s) from the number of compressors such that system operation data set is provided,

(34) processing the power/energy usage measurement data set and the system operation data set by using a control unit such that data points, related to the power/energy usage measurement data set, are affiliated to operational compressor combination(s) and operating mode(s) by using the system operation data set, such that a measured specific energy consumption data set comprising power/energy usage measurement data for different compressor combinations and operating mode(s) is provided,

(35) selecting, based on the measured specific energy consumption data, a selected compressor combination, and

(36) configuring the multiple compressor system according to the selected compressor combination.

(37) The power/energy usage measurement data may comprise measurement data of flow and power/energy consumption or estimated flow associated with the measured power/energy consumption.

(38) Alternatively, if one system is used for collecting and processing data and another system is used for controlling the multiple compressor system, the approach may be described as below:

(39) A method for monitoring a multiple compressor system, wherein the multiple compressor system comprises a number of compressors together providing a common output flow, said method comprising

(40) receiving power/energy usage measurement data from a number of sensors connected to the number of compressors, respectively, over a period of time such that a power/energy usage measurement data set covering several compressor combinations and/or operating modes is provided.

(41) receiving, in parallel with receiving the power/energy usage measurement data, system operation data related to operational compressor combination(s) and operating mode(s) from the number of compressors such that system operation data set is provided,

(42) processing the power/energy usage measurement data set and the system operation data set by using a control unit such that data points, related to the power/energy usage measurement data set, are affiliated to operational compressor combination(s) and operating mode(s) by using the system operation data set, such that a measured specific energy consumption data set comprising power/energy usage measurement data for different compressor combinations and operating mode(s) is provided,

(43) such that, based on the measured specific energy consumption data, a selected compressor combination may be selected, and the multiple compressor system configured according to the selected compressor combination.

(44) The power/energy usage measurement data may comprise measurement data of flow and power/energy consumption or estimated flow associated with the measured power/energy consumption.

(45) The different features and advantages mentioned above with reference to the method set forth in claim 1 are also applicable to the methods above.

(46) As illustrated in FIG. 13, a server 1302 may be used for implementing the approach described above. The server 1302 may be part of a system 1300, and can comprise a memory 1304 comprising an affiliation function 1306, a compressor combination selection function 1308 and a configuration function 1310. In short, the affiliation function 1306 can be configured to affiliate the power/energy usage measurement data set and the system operation data set as explained above. The compressor combination selection function 1308 can be configured such that based on the measured specific energy consumption data, a selected compressor combination can be selected. This selection may be based on user input or may be performed automatically by the server. The configuration function 1310 can be configured to configure the multiple compressor system according to the selected compressor combination, which may comprise changing the system operation data, that is, which compressor combination(s) and operating mode(s) that are in operation.

(47) In addition, the server 1302 can comprise a control unit 1312, comprising a processor 1314, and a transceiver 1316. By using the transceiver 1316, data can be exchanged with multiple compressor systems 1318a, 1318b, 1318c communicatively connected to the server 1302. More particularly, power/energy use measurement data 1320a, 1320b, 1320c and system operation data 1322a, 1322b, 1322c may be transferred from the multiple compressor systems 1318a, 1318b, 1318c to the server 1302, and from the server 1302 configuration data 1324a, 1324b, 1324c may be transferred to the multiple compressor systems 1318a, 1318b, 1318c.

(48) The approach described above, in the form of the server 1302, can be described as below:

(49) The server 1302 configured to control the multiple compressor system 1318a, 1318b, 1318c, wherein the multiple compressor system comprises a number of compressors together providing a common output flow, said server comprising

(50) the transceiver 1316 configured to receive:

(51) the power/energy use measurement data 1320a, 1320b, 1320c from a number of sensors connected to the number of compressors, respectively, over a period of time such that a power/energy usage measurement data set covering several compressor combinations and/or operating modes is provided;

(52) the system operation data 1322a, 1322b, 1322c related to operational compressor combination and operating mode(s) from the number of compressors such that a system operation data set is provided,

(53) the control circuit 1312 configured to execute:

(54) the affiliation function 1306 configured to process the power/energy usage measurement data set and the system operation data set such that data points, related to the power/energy usage measurement data set, are affiliated to operational compressor combination and operating mode(s) such that a measured specific energy consumption data set comprising power/energy usage measurement data for different compressor combinations and operating mode(s) is provided,

(55) the compressor combination selection function 1308 configured to select, based on the measured specific energy consumption data, the selected compressor combination, and

(56) the configuration function 1310 configured to configure the multiple compressor system 1318a, 1318b, 1318c according to the selected compressor combination using configuration data 1324a, 1324b, 1324c,

(57) wherein the transceiver is further configured to transfer:

(58) the configuration data 1324a, 1324b, 1324c to the multiple compressor system 1318a, 138b, 1318c.

(59) The power/energy usage measurement data may comprise measurement data of flow and power/energy consumption or estimated flow associated with the measured power/energy consumption.

(60) Alternatively, as discussed above, if two or more systems are used the server may instead be described as below:

(61) The server configured to monitor the multiple compressor system 1318a, 1318b, 1318c, wherein the multiple compressor system comprises a number of compressors together providing a common output flow, said server comprising

(62) the transceiver 1316 configured to receive:

(63) the power/energy use measurement data 1320a, 1320b, 1320c from a number of sensors connected to the number of compressors, respectively, over a period of time such that a power/energy usage measurement data set covering several compressor combinations and/or operating modes is provided;

(64) the system operation data 1322a, 1322b, 1322c related to operational compressor combination and operating mode(s) from the number of compressors such that a system operation data set is provided,

(65) a monitoring circuit configured to execute:

(66) the affiliation function 1306 configured to process the power/energy usage measurement data set and the system operation data set such that data points, related to the power/energy usage measurement data set, are affiliated to operational compressor combination and operating mode(s) such that a measured specific energy consumption data set comprising power/energy usage measurement data for different compressor combinations and operating mode(s) is provided,

(67) wherein the transceiver is further configured to transfer

(68) the measured specific energy consumption data to other devices configured to execute the compressor combination selection function 1308 configured to select, based on the measured specific energy consumption data, the selected compressor combination, and the configuration function 1310 configured to configure the multiple compressor system 1318a, 1318b, 1318c according to the selected compressor combination using configuration data 1324a, 1324b, 1324c.

(69) The power/energy usage measurement data may comprise measurement data of flow and power/energy consumption or estimated flow associated with the measured power/energy consumption.

(70) The different features and advantages mentioned above with reference to the method set forth in claim 1 are also applicable to the servers above. Further, as illustrated, several multiple compressor systems may be connected to the server. In addition to reducing hardware costs, this also provides an advantage in that information from different multiple compressor systems may be compared and aligned. Thus, for instance, a positive side effect of using the server for assuring energy efficient operation for a plurality multiple compressor systems is that maintenance or service needs may be detected at an early stage by comparing the different multiple compressor systems to one another such that inconsistencies can be detected.