JP4429357B2 - Energy cost analyzer for refrigeration systems - Google Patents

Description

This application is a continuation-in-part of US patent application Ser. No. 10/819850, filed Apr. 7, 2004.
The present invention relates generally to energy analyzers, and more particularly, to operating cost savings of refrigeration systems incorporating variable speed drives for use in refrigeration systems incorporating fixed or constant speed beats, as compared to fixed or constant speed drives. Relates to an energy analyzer for providing an estimate of.

  A refrigeration system, such as a refrigeration system, is driven by a compressor that operates at a substantially constant speed to compress refrigerant vapor circulating in a refrigeration circuit including a compressor and an evaporator to cool an interior space. Can be driven. The performance of the refrigerator system is designed to achieve the rated capacity with the rated head while consuming a predetermined amount of energy. For example, a refrigerator system with an inlet condenser water temperature (“ECWT”) rated at approximately 30 ° C. (85 ° F.) and a cooling capacity rated at 400 tons will achieve 400 tons of cooling at a predetermined energy rate such as 250 kW. obtain. By operating the compressor at a constant speed using a constant speed drive (“CSD”), the compressor will adapt to the cooling load and head when the cooling load and head are less than the rated capacity of the compressor. Consumes more energy than is needed The amount of wasted energy caused by lower cooling loads and lower heads can be significant.

  Introducing a variable speed drive ("VSD") to drive the compressor motor allows the compressor motor to operate at variable speeds in response to variable cooling loads and variable cooling heads become. For example, in response to a reduction in cooling load, the VSD reduces the operating speed of the compressor motor and also reduces the cooling provided by the refrigeration system to accommodate the reduced cooling load. Even if the system is operating at full capacity, it is possible to reduce the speed in response to a drop in water head (a drop in wet bulb outside air temperature). Decreasing the operating speed of the compressor motor reduces the amount of energy required to operate the compressor, resulting in energy savings. Such savings can be substantial, and typically only a few years of operation can cover the cost of installing a VSD to replace the existing CSD in the refrigeration system.

  One way to encourage the refrigeration system owner to install the VSD is that the installer installs the VSD in the owner's refrigeration system with little or no cost to the owner. Is to construct a mechanism to be performed. The installer will be paid a percentage of the cost savings realized by operating the refrigeration system for a predetermined period of time to recover the VSD costs and their mounting costs. However, calculating cost savings is not easy to perform. First of all, since the CSD has been removed, there is no longer any direct means of measuring the energy costs associated with CSD operation. Second, because the compressor speed, or VSD, is constantly changing as its name suggests, VSD operation is unsuitable for comparing CSD vs. VSD operation-related costs.

  Another way to encourage refrigeration system owners to install a VSD is that the installer attaches an analyzer to the refrigeration system and presents potential cost savings between VSD vs. CSD operation without installing the VSD. That is. However, as discussed earlier, such comparisons are not easy to perform.

  Therefore, while the refrigeration system uses only VSD, or alternatively, the refrigeration system uses only CSD, the difference between the CSD vs. VSD operation-related costs in the cooling system is accurately compared and calculated. There is a need for a method for displaying.

  The present invention relates to a method for comparing costs associated with operation of a refrigeration system using a first drive type to a second drive type while the refrigeration system is operating in a first drive type. These steps provide, for a refrigeration system that uses the second drive type, an equation that correlates the operating performance of the refrigeration system that uses the first drive type, and values related to the operation of the refrigeration system. , Measuring a parameter associated with the equation, determining an amount of energy required by the first drive type to operate the refrigeration system for a predetermined time, and Calculating a ratio based on the amount of energy required by the first drive type divided by the required amount of energy; calculating a cost associated with operating a refrigeration system using the first drive type; Calculating the costs associated with operating the refrigeration system using the second drive type using the equations, and for the refrigeration system using the first drive type. The costs associated with rolling, and a step of comparing the cost associated with operation of the refrigeration system using the second drive type.

  The invention further relates to a refrigeration system including a refrigeration circuit having a compressor driven by an electric motor, a condenser, and an evaporator connected in a closed loop. The first drive type drives the motor of the compressor. A computer system comprising a microprocessor and a storage device for storing an equation for calculating an operating cost of a refrigeration circuit using a second drive type. The equation captures at least one measured operating parameter of the refrigeration circuit. At least one sensing element measures at least one operating parameter of the refrigeration circuit. The computer system is configured to determine the amount of energy required by the first drive type that uses the refrigeration circuit during a predetermined time. A first ratio based on the amount of energy required by the first drive type divided by the predetermined amount of energy required by the first drive type. A second ratio obtained by a computer system for solving the equation using the first ratio and at least one operating parameter. The second ratio is based on the amount of energy required by the second drive type divided by the predetermined amount of energy required by the second drive type.

  The present invention relates to a refrigeration system including a refrigeration circuit having a compressor driven by an electric motor, a condenser, and an evaporator connected in a closed loop. The first drive type drives the motor of the compressor. At least one sensing element measures at least one operating parameter of the refrigeration circuit. The computer system includes a microprocessor and a storage device and at least one computer program, the at least one computer program configured to calculate the operating cost of the refrigeration circuit using the first drive type and the second drive type. Is done. A certain amount of energy is used by the first drive type in the refrigeration circuit for a predetermined time. The first ratio is based on the amount of energy consumed by the first drive type divided by the predetermined amount of energy required by the first drive type. The second ratio is based on the amount of energy required by the second drive type divided by the predetermined amount of energy required by the second drive type. The second ratio is determined from an equation having the first ratio and at least one operating parameter as input to the equation.

  A major advantage of the present invention is that the energy savings in the operation of a refrigeration system with a VSD different from CSD can be compared without the need for a CSD driven refrigeration system.

  Another advantage of the present invention is that unrealized energy savings in the operation of refrigeration systems with a CSD different from VSD can be compared without requiring a VSD driven refrigeration system.

  Another advantage of the present invention is that the energy savings in operating a refrigeration system with a VSD different from the CSD can be compared without requiring the processing of a group of performance curves associated with the CSD.

  Yet another advantage of the present invention is that unrealized energy savings in the operation of a refrigeration system with a CSD different from the VSD can be compared without requiring the processing of a group of performance curves associated with the VSD.

  Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example only, the principles of the invention.

  Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

  FIG. 1 illustrates the overall application of the present invention. The AC power supply 20 supplies power to a variable speed drive (VSD) 30 that supplies power to the electric motor 50. In another embodiment, the VSD 30 may power more than one motor 50 or may power each corresponding motor 50 using each of several VSDs 30 or VSD sections. . Preferably, the electric motor 50 is used to drive the refrigeration system or the corresponding compressor 60 of the refrigeration system 10.

  The AC power supply 20 supplies single-phase or multi-phase (eg, three-phase) fixed voltage, fixed frequency AC power to the VSD 30 from an AC public power supply network or power distribution system existing in the field. The AC power source 20 can supply 200 V, 230 V, 380 V, 460 V, or 600 V AC voltage or line voltage to the VSD 30 at a power frequency of 50 Hz or 60 Hz, depending on its corresponding AC public power network.

  The VSD 30 receives AC power from the AC power supply 20 with a specific fixed line voltage and fixed power frequency, and the desired voltage and desired frequency (both can be changed accordingly to suit specific requirements). Then, AC power is supplied to the electric motor 50. The VSD 30 is preferably capable of supplying AC power to the motor 50 that may have a voltage and frequency higher and lower than the rated voltage and frequency of the motor 50. In another embodiment, the VSD 30 can supply higher and lower frequencies than the rated voltage and frequency of the motor 50, but can also supply only the same or lower voltage.

  A microprocessor, controller, or control board 40 is used to control the VSD 30, motor 50, and the control board 40 preferably includes a display and a keypad, rather than using a CSD (not shown). Can be used to analyze and compare costs associated with operating a cooling system using the VSD 30. In the following, in particular, such VSD 30 and CSD cost comparison will be discussed in more detail in the absence of CSD.

  The control panel 40 uses one or more control algorithms or software to control the operation of the refrigeration system 10 and to control the capacity of the compressor 60 in response to specific output capacity requirements for the refrigeration system 10. A control system that determines and implements an operational configuration for execution is executed. In one embodiment, the one or more control algorithms may be a computer program or software stored in a non-volatile storage device of the control board 40, which further includes a series of instructions that can be executed by the macro processor of the control board 40. Can be included. Although the control algorithm is preferably embodied as one or more computer programs and executed by a microprocessor, the control algorithm is implemented and executed by those skilled in the art using digital and / or analog hardware. It should be understood that this can be done.

  The electric motor 50 is preferably an induction motor operable at a variable speed. The induction motor may have any suitable pole arrangement including two poles, four poles, or six poles. However, any suitable electric motor that can operate at a variable speed can be used in the present invention.

  The control board, microprocessor, or controller 40 may operate the VSD 30 in order to provide optimal operating settings to the VSD 30 and the motor 50 in response to specific sensing element readings received by the control board 40. It is preferable to send a control signal for controlling the operation of the electric motor 50 to the VSD 30. For example, in the refrigeration system 10, the control panel 40 can adjust the output voltage and frequency supplied by the VSD 30 to accommodate changing conditions of the refrigeration system 10. That is, the control board 40 responds to increasing / decreasing load / head conditions to the compressor 60 to achieve the desired operating speed of the motor 50 and the desired capacity of the compressor 60, thereby providing an output voltage supplied by the VSD 30. And the frequency can be increased or decreased. A conventional HVAC system, refrigeration system, or liquid refrigerator system 10 includes a number of other features not shown in FIG. These features are intentionally omitted to simplify the drawing for ease of illustration.

  The refrigeration system 10 has a condenser arrangement 70, a heat removal (HOR) device 80 such as a liquid reservoir (having a supply pipe 90 for supplying water to the condenser 70 and a return pipe 100 for returning water to the HOR device 80), Further included is an expansion device, water refrigerator, or evaporator arrangement 110. The control board 40 may include an analog / digital (A / D) converter, a microprocessor, a non-volatile storage device, and an interface board for controlling the operation of the refrigeration system 10. The control panel 40 can also be used to control the operations of the VSD 30, the electric motor 50, and the compressor 60. The compressor 60 compresses the refrigerant vapor and sends it to the condenser 70.

  The compressor 60 is preferably a screw compressor or a centrifugal compressor, but the compressor may be any suitable type of compressor, including a reciprocating compressor, scroll compressor, rotary compressor, or other type of compressor. It can be. The coefficients of the best fit curve remain the same, but are compressor type dependent or refrigerant dependent (see equations [1] and [2] below). The output capability of the compressor 60 can be based on the operating speed of the compressor 60, but the operating speed depends on the output speed of the electric motor 50 driven by the VSD 30. In some cases, the refrigerant vapor sent to the condenser 70 can also use air, but enters a heat exchange relationship with a fluid such as water, and as a result of the heat exchange relationship with this fluid, changes the phase to the refrigerant liquid. It passes. The condensed liquid refrigerant from the condenser 70 passes through the corresponding expansion device and flows to the evaporator 110.

  The evaporator 110 may include connections for a cooling load supply and return pipe. The secondary liquid, preferably water, is preferred, but any other suitable secondary liquid, such as ethylene glycol, propylene glycol, calcium chloride brine, or sodium chloride brine, is connected to the evaporator 110 via the return pipe. Enters and exits the evaporator 110 via a supply pipe. The liquid refrigerant in the evaporator 110 enters a heat exchange relationship with the secondary liquid to cool the temperature of the secondary liquid. The refrigerant liquid in the evaporator 110 undergoes a phase change to refrigerant vapor as a result of the heat exchange relationship with the secondary liquid. Next, the vapor refrigerant in the evaporator 110 returns to the compressor 60 and the cycle ends. It should be understood that any suitable configuration of the condenser 70 and evaporator 110 can be used in the present system 10 if an appropriate phase change of refrigerant is achieved in the condenser 70 and evaporator 110.

  The present invention includes equations that can correlate the operating performance of the refrigeration system 10 to VSD 30 vs. CSD. The equations of the present invention are derived from an air conditioning and refrigeration facility (ARI) program that has been certified to accurately correspond to the operational performance of the represented refrigeration system. However, the equations of the present invention are generated from many curves (as illustrated in FIGS. 2, 3, and 7, 8) relating to the operation of a refrigeration system using VSD, with each curve representing a selected constant head. Use a single “best fit” curve. Similarly, a single “best fit” curve is created from many curves related to operating a refrigeration system using CSD. Each “best fit” curve corresponds to the operation of a refrigeration curve with a cooling fluid such as water entering the condenser 70 from the supply tube 90 at a given temperature. Once the refrigeration system is operated using the VSD 30, the load percentage (% load) can be measured. This% load is the ratio of the amount of cooling supplied by the refrigeration system divided by the design capacity of the refrigeration system. For example, if the refrigeration system has a design cooling capacity of 400 tons and is operating to supply 200 tons, its% load is 50%. Since the% load for the corresponding CSD and VSD curves is the same at the time of comparison, the curves can overlap. Y-axis intercept (% kW) so that operating costs can be compared by correlating overlapping best-fit curves with common x-axis intercept values (% load), which define a calculation chart Can be compared.

  Two equations of the present invention were derived from a refrigeration system using refrigerant R134a (FIGS. 2-6) and the other from a refrigeration system using refrigerant R123 (FIGS. 7-11). Since each equation is derived in the same way, only FIGS. 2-6 will be discussed in detail. Each derived equation is a nine-term polynomial that contains the same combination of the two parameters discussed in more detail below.

  FIG. 2 shows the performance for a refrigeration system using CSD, using refrigerant R134a, and having an inlet condenser water temperature (“ECWT”) of about 18 ° C. (65 ° F.) (see supply line 90 in FIG. 1). A curve is shown. Each curve corresponds to a refrigeration system having a different cooling capacity expressed in tons (1 ton equals 12,000 British thermal units). There are six different cooling capacity curves corresponding to 400 to 1,400 tons increasing in increments of 200 tons. The seventh curve is the best fit curve, which was calculated from a curve fitting program that most closely corresponds to the six cooling capacity curves. FIG. 3 measures the same data as that measured in FIG. 2, except that FIG. 3 corresponds to the performance curve for a refrigeration system using VSD. However, as is well known to those skilled in the art, the head can also be measured as a function of the exit condenser water temperature ("LCWT"), the saturation condensation temperature, the refrigerant pressure, or the temperature difference between the evaporator and the condenser. It is. These different measurements can be incorporated into the equation by changing the coefficients of the relational expression (see equations [1] and [2] below).

  Similar sets of performance curves were generated for a range of about 7 ° C. to about 35 ° C. (45 ° F. to 95 ° F.) for each ECWT increase in steps of about 2.8 ° C. (5 ° F.). . FIG. 4 shows the performance curves for refrigeration systems using CSD at different ECWTs ranging from about 7 ° C. to about 35 ° C. (45-95 ° F.) increasing in increments of about 2.8 degrees (5 degrees). Similarly, FIG. 5 shows the performance curves for refrigeration systems using VSD at different ECWTs ranging from about 7 ° C. to about 35 ° C. (45-95 ° F.) increasing in steps of about 2.8 ° (5 °). Show.

  FIG. 6 includes both performance curves for a refrigeration system using CSD and VSD for an ECWT of about 18 ° C. (65 ° F.). Although these curves are different from each other, these curves share a common cooling load at the particular time they are applied. For example, if the refrigeration system is a 500-ton device and the specific cooling load is 350 tons, the% load is 70%. A vertical x-intercept line can be drawn from the 70% load to intersect each of these curves, with point A relating to the VSD curve and point B relating to the CSD curve. Similarly, a horizontal line can then be drawn from point A of the VSD curve to define y-intercept point C. A horizontal line can then be drawn from point B of the CSD curve to define y-intercept point D. Each of points C and D corresponds to a% kW reading, which is 100% load, ie the percentage of energy consumed compared to the energy consumed at the design load. The amount of energy consumed by the design load is the design kW. Since this design load is based on the rated motor speed and the voltage supplied to the motor, if the motor speed exceeds the rated motor speed, as shown by part of the curve in the upper right part of FIG. Both can exceed 100%, ie, design load and design kW.

  To calculate the energy cost, multiply each of the% kW readings for each speed drive by its design kW to obtain a kW value. Then, after multiplying by the respective design kW, each of the calculated kW values is reduced with respect to each other to obtain the difference kW, which is the difference between points C and D on the% load (y-axis). However, energy consumption is typically expressed in kWh. Therefore, once the difference kW is calculated, this difference is multiplied by the amount of time that the difference kW has occurred, and then further multiplied by the energy billing rate (such as $ 0.06 per kWh).

  As described above, FIGS. 2 to 6 and FIGS. 7 to 11 correspond to the refrigeration system performance curves, and the refrigeration system of FIGS. 7 to 11 has a different refrigerant R123 with respect to R134a (or R22) of FIGS. (Or R11), and the cooling capacity in the R123 refrigeration system was 300 to 800 tons compared to 400 to 1,400 tons in the R134a refrigeration system, but is made in the same way.

  By combining curve fitting points to obtain a single curve for ECWT, each increasing in steps of about 2.8 ° C. (5 ° F.), as in FIG. Absent. That is, the fitting curve in FIG. 2 does not exactly match the curve for any of the head / capacity curves in FIG. However, since these curves substantially overlap each other, the best fit approximation is close, and these values are typically within about 5% of the arbitrarily selected head / capacity. Best fit approximation removes the requirement for a significant amount of data that would otherwise need to be obtained to perform such a calculation. Such a best-fit approximation method is a greatly simplified approach, but as discussed in FIG. 6, it includes CSD for ECWT increasing in steps of about 2.8 ° C. (5 ° F.), respectively. It is still necessary to perform a number of calculations to maintain the performance curves for both VSD and VSD and to determine the% kW ratio.

  To avoid curve processing and related calculations, to obtain a ratio of CSD input to CSD design kW (identified as “D”), for each ECWT increasing in steps of about 2.8 ° C. (5 ° F.) The best fit curve data was used to derive equations for each of the two refrigeration systems in each of FIGS. These equations define 9-term polynomials with different coefficients, but each based on various combinations of 2 terms. The first term “X” is the ratio of the VSD input kW to the VSD design kW over a range of 0.00 to 1.00. The second term “Y” is ECWT measured in Fahrenheit (° F.). Equation [1] is derived from data extracted from the curve of FIG. 4, and equation [2] is derived from data extracted from the curve of FIG.

  These equations do not require a refrigeration system performance curve for either drive, allowing a comparison between the energy cost of a refrigeration system using CSD and the measured energy cost of a refrigeration system using VSD. .

  By applying this equation, for refrigeration system 10 using CSD, cost per kW hour and ECWT need to be given to calculate the cost savings for refrigeration system 10 using VSD 30. Both VSD design kW and CSD design kW need to be given. In one example, an 800 ton refrigeration system using refrigerant R134a had a design kW for VSD of 530 kW, a design kW for CSD of 508 kW, and an input VSD of 285 kW. The ECWT was about 22 ° C. (72 ° F.). Thus, the “X” term (input variable speed kW / VSD design kW) was 285 kW divided by 530 kW, ie about 0.54. The “Y” term is about 22 (72). Substituting these values into equation [1] yields a value for “D” of about 0.68, which is the ratio of CSD input kW (“Z”) divided by CSD design kW (D = 0). .68 = Z / 508). This gives a value for a CSD input kW of 345 kW.

  See FIG. 5 which is a variable speed curve using refrigerant R134a to double check the results from the equation against the chart data. Line “E” is the y-intercept that extends horizontally from 0.54 (54%) to point “F”. Point “F” was an interpolation between an ECWT curve of about 21 ° C. (70 ° F.) and an ECWT curve of about 24 ° C. (75 ° F.) because the ECWT was about 22 ° C. (72 ° F.). is there. Following the vertical line from point “F” to the x-intercept, ie point “G”, we get about 80% load. Refer now to FIG. 4, which is a constant velocity curve using R134a. Starting at 80% load, that is, starting from point “H” and following vertical line “I” to point “J”, ECWT was about 22 ° C. (72 ° F.), so that point was also about 21 ° C. Interpolation between an ECWT curve of (70 ° F.) and an ECWT curve of about 24 ° C. (75 ° F.). Tracing the line “K” from the point “J” to the y-intercept, ie the point “L”, is 0.68, which matches the ratio calculated for D above. Thus, this example confirms that equation [1] defines the relationship between CSD performance and VSD performance for refrigeration systems.

  Then, to calculate the actual cost savings, for convenience, assuming these values were maintained for 1 hour, a refrigeration system using VSD and CSD would have an energy cost of $ 0.06 per kWh. The difference in kW with the refrigeration system using is 60 kW (345-285 kW). In that case, the one hour savings under these conditions is $ 3.60 ($ 0.06 × 60).

  FIG. 12 exemplifies a flowchart clearly showing the control process of the present invention regarding cost comparison in the refrigeration system 10 shown in FIG. The process begins at step 200 where values such as price per kW hour, variable speed design kW, and constant speed design kW are input to the control panel 40. The variable speed design kW and the constant speed design kW are values set by the manufacturer when the refrigeration system is commissioned and are intended to be input by the installer. The price per kW hour can be updated as needed. This information is preferably input to a keypad provided on the control panel 40. In the configuration of the control panel 40 that is not provided with a keypad and a screen, separate devices having these characteristics can be mounted. The display screen of the control panel 40 is typically set to either “total energy saving” or “total savings” (both displayed in US dollars).

  Once these values are input to the control board 40 at step 200, the refrigeration system is operational and at step 210, the control board 40 measures parameters such as ECWT or other values related to operating performance. The Fahrenheit ECWT is preferably obtained from an analog input channel using a sensing element such as a thermistor. This information and other information can be supplied directly to the control board 40. Further, at step 210, the input VSD kW data undergoes a change in response to the cooling load measured by the control panel 40, so that the input VSD kW data from the VSD or optional harmonic filter or other device is predetermined. Are supplied to the control panel 40 at intervals of 2 seconds (such as every 2 seconds).

  After measuring the parameter, the value is calculated at step 220 and stored at step 230. The stored values can include not only the values calculated in step 220 but also the parameters measured in step 210. Several values calculated at step 220 and described below are outlined by the subject matter and further include consideration of measurement, calculation, and storage steps.

Hourly average return condenser liquid temperature (x 24 hours)
The return condenser liquid temperature is preferably read every second and summed. After 3600 seconds, the sum is divided by 3600 to get the average of the past hour, and then the sum is set back to zero. The average for the last 24 hours is preferably scrolled using a first-in first-out (“FIFO”) scheme, and the most recently calculated average is preferably stored at the first array position. These values are preferably stored in an erasable random access storage device ("RAM") (such as battery-backed RAM or BRAM) that includes the total sum, the data index point, and the Julian time of the last data point.

Daily return condenser liquid temperature (x 30 days)
The hourly average return condenser liquid temperature is preferably read hourly and summed. After 24 hours, the sum is preferably divided by 24 to obtain the average of the previous day, and then the sum is returned to zero. The average for the last 30 days is preferably scrolled using a FIFO scheme, and the latest calculated average is preferably stored at the first array position. These values are preferably stored in a storage device that includes the total sum, the data index point, and the Julian time of the last data point.

Monthly average return condenser liquid temperature (x 12 months)
The daily average return condenser liquid temperature is preferably read daily and summed. After 30 days, the sum is preferably divided by 30 to obtain an average for the last month, and then the sum is preferably set back to zero. The average for the past 12 months is preferably scrolled using a FIFO scheme, and the latest calculated average is preferably stored at the first array position. These values are preferably stored in a storage device that includes the total sum, the data index point, and the Julian time of the last data point.

Annual average return condenser liquid temperature (× 20 years)
The monthly average return condenser liquid temperature is preferably read monthly and summed. After 12 months, the sum is preferably divided by 12 to obtain an average over the past year, and then the sum is preferably set back to zero. The average over the last 20 years is preferably scrolled using a FIFO scheme, and the latest calculated average is preferably stored at the first array location. These values are preferably stored in a storage device that includes the total sum, the data index point, and the Julian time of the last data point.

Hourly minimum return condenser liquid temperature (x 24 hours)
The return condenser liquid temperature is preferably read every second and compared to the final minimum. If it is less than the final minimum, the final minimum is preferably set to the current temperature reading. The minimum value for the past 24 hours is preferably scrolled using a FIFO scheme, and the latest evaluated minimum value is preferably stored in the first array position. These values are preferably stored in a storage device containing the Julian time of the last data point.

Daily minimum return condenser liquid temperature (x 30 days)
When the calendar day changes, the hourly minimum return condenser liquid temperature for the last 24 hours is checked for the minimum of the day. The minimum value for the last 30 days is preferably scrolled using a FIFO scheme, and the latest evaluated minimum value is preferably stored at the first array location. These values are preferably stored in a storage device containing the Julian time of the last data point.

Monthly minimum return condenser liquid temperature (x 12 months)
When the calendar month changes, the daily minimum return condenser liquid temperature for the last 30 days is examined for the minimum for that month. The minimum value for the past 12 months is preferably scrolled using a FIFO scheme, and the latest evaluated minimum value is preferably stored at the first array position. These values are preferably stored in a storage device containing the Julian time of the last data point.

Annual minimum return condenser liquid temperature (× 20 years)
When the calendar year changes, the monthly minimum return condenser liquid temperature for the last 12 months is examined for the minimum value for that year. The minimum value for the past 20 years is preferably scrolled using a FIFO scheme, and the latest evaluated minimum value is preferably stored at the first array location. These values are preferably stored in a storage device containing the Julian time of the last data point.

VSD kW hour meter This calculation can be performed as follows. That is, VSD kW is transmitted from the VSD to the control panel once every 2 seconds. This value is added to the VSD kW total. When this sum exceeds 1800 (3600 seconds per hour / 2 seconds per reading), 1800 kW is equal to 1 kW at this data collection rate, so the VSD kW hour meter increases by 1 kW hour, corresponding to partial kW time 1800 is subtracted from the VSD kW total, which resets the partial kW hour component of the VSD kW hour meter. The value of the VSD kW meter can be modified if the access level is set appropriately. Preferably both the VSD kW hour meter and the VSD kW total are stored in the storage device.

CSD kW hour meter To obtain VSD% design kW, VSD kW is divided by VSD design kW every 2 seconds during the operation of the refrigerator. Using ECWT and equations, the CSD% design kW is determined. This is preferably multiplied by the CSD design kW to obtain CSD kW. The CSD kW value is preferably added to the CSD kW total. When this sum exceeds 1800 (3600 seconds per hour / 2 seconds per reading), at this data collection rate, 1800 kW is equal to 1 kW, so the CSD kWh meter preferably increases by 1 kWh The 1800 corresponding to kW hour is preferably subtracted from the CSD kW total, which resets the partial kW hour component of the CSD kW hour meter. The value of the CSD kW hour meter can be modified if the access level is set appropriately. Preferably, both the CSD kW hour meter and the CSD kW total are stored in the storage device.

Total saving energy Preferably, every 2 seconds during operation of the refrigerator, the saved energy is calculated by subtracting VSD kW from CSD kW using the transmitted VSD kW and the calculated CSD kW. This value is then added to the saving kW total. When this sum exceeds 1800 (3600 seconds per hour / 2 seconds per reading), this data collection rate is equal to 1800 kW at 1 kW, so the total saving energy (in kW) increases by 1 kW Preferably, the corresponding 1800 at the time of the partial kW is subtracted from the saving kW total, which resets the partial kW hour component of the VSD kW hour meter. The value of total energy savings can be modified if the access level is set appropriately. Both total saving energy and saving kW total are preferably stored in the storage device.

Total saving energy per hour (× 24 hours)
The total saving energy is preferably read every hour. To determine the current hourly value, the reading read one hour ago is subtracted from the most recent reading. The hourly values for the past 24 hours are preferably scrolled using a FIFO method, and the latest hourly value calculated most recently is preferably stored in the first array position. These values are preferably stored in a storage device that includes the total sum, the data index point, and the Julian time of the last data point.

Total energy saving per day (× 30 days)
The total saving energy is preferably read daily at midnight. To determine the value for the current day, the reading read one day ago is subtracted from the reading that was just read. The day values for the last 30 days are preferably scrolled using a FIFO scheme, and the latest calculated day value is preferably stored at the first array position. These values are preferably stored in a storage device that includes the total sum, the data index point, and the Julian time of the last data point.

Total monthly energy savings (× 12 months)
The total saving energy is preferably read at midnight on the last day of every month. To determine the current monthly value, the reading read one month ago is subtracted from the most recent reading. Monthly values for the past 12 months are preferably scrolled using a FIFO scheme, and the latest calculated monthly value is preferably stored in the first array position. These values are preferably stored in a storage device that includes the total sum, the data index point, and the Julian time of the last data point. The actual meter reading on the last day of each month is also stored.

Annual energy savings (× 20 years)
The total saving energy is preferably read at midnight on the last day of each year. To determine the current annual value, the reading read one year ago is preferably subtracted from the most recent reading. The annual values for the past 20 years are preferably scrolled using a FIFO scheme, and the most recently calculated latest annual value is preferably stored in the first array location. These values are preferably stored in a storage device that includes the total sum, the data index point, and the Julian time of the last data point.

Total savings in US dollars To calculate the total savings in US dollars, the total savings energy is preferably multiplied by the cost per kWh.

  After these values and parameters are stored at step 230, the values as identified above and preferably the value relating to the savings may be output to a display provided on the control panel 40.

  FIG. 13 generally illustrates another application of the present invention. FIG. 13 is the same as FIG. 1 except that the CSD 130 is provided instead of the VSD 30. In another embodiment, a CSD 130 can power more than one motor 50, or each of a plurality of CSDs 130 can power a corresponding motor 50. .

  CSD 130 receives AC power having a specific fixed line voltage and fixed power frequency from AC power supply 20 and supplies AC power to motor 50 at a fixed voltage and frequency to drive motor 50 at a substantially constant rotational speed. To do.

  The present invention includes equations that can correlate the operating performance of refrigeration system 10 to CSD 130 vs. VSD. The equations of the present invention are derived from an air conditioning and refrigeration facility (ARI) program that has been certified to accurately correspond to the operational performance of the represented refrigeration system. However, the equations of the present invention are generated from many curves (as illustrated in FIGS. 2, 3, and 7, 8) relating to the operation of a refrigeration system using CSD, with each curve representing a selected constant head. Use a single “best fit” curve. Similarly, a single “best fit” curve is created from many curves related to operating a refrigeration system using VSD. Each “best fit” curve corresponds to the operation of a refrigeration curve with a cooling fluid such as water entering the condenser 70 from the supply tube 90 at a given temperature. Once the refrigeration system is operated using the CSD 130, the load percentage (% load) can be measured. This% load is the ratio of the amount of cooling supplied by the refrigeration system divided by the design capacity of the refrigeration system. For example, if the refrigeration system has a design cooling capacity of 400 tons and is operating to supply 200 tons, its% load is 50%. Since the% load for the corresponding CSD and VSD curves is the same at the time of comparison, the curves can overlap. The y-axis intercept (% kW) can be compared so that operating costs can be compared by correlating overlapping best-fit curves with common x-axis intercept values (% load) (which define the calculation chart). It is possible to compare.

  In other words, since the same CSD and VSD curves are used in the same way, the previous discussion regarding the curves of FIGS. 2-6 (and FIGS. 7-11) applies equally to this case. Furthermore, since the same best fit curve data of FIGS. 4 and 5 are used, the derivation equations [1] and [2] that correlate the operating performance of the refrigerator system 10 with VSD 30 vs. CSD (FIG. 1) are When comparing the operational performance of the system 10 with the derived equations [3] and [4] that correlate to CSD 130 vs. VSD (FIG. 13), a similar 9-term polynomial is represented.

  To avoid curve processing and related calculations, to obtain a ratio of VSD input to VSD design kW (identified as “E”), for each ECWT increasing in steps of about 2.8 ° C. (5 ° F.) The best fit curve data was used to derive equations for each of the two refrigeration systems in each of FIGS. These equations define 9-term polynomials with different coefficients, but each based on various combinations of 2 terms. The first term “A” is the ratio of the CSD input kW to the CSD design kW over a range of 0.00 to 1.00. The second term “B” is the ECWT measured in Fahrenheit (° F.). Equation [3] is derived from data extracted from the curve of FIG. 5, and equation [4] is derived from data extracted from the curve of FIG.

  These equations do not require refrigeration system performance curves for either drive, allowing comparison of the refrigeration system energy cost using VSD with the measured energy cost of refrigeration system using CSD. .

  For the refrigeration system 10 using VSD, to calculate the cost savings for the refrigeration system 10 using CSD 130, the cost per kW and ECWT need to be given, so that the CSD design kW and the VSD design kW You need to be given both. For convenience and to compare the results obtained from equations [1] and [3], the 800 ton refrigeration system embodiment using refrigerant R134a is again used. Since this example for a refrigeration system was tested using VSD, the CSD input kW value calculated using equation [1] is given for use in equation [3]. Thus, the following value is given: That is, the design kW for VSD was 530 kW, the design kW for CSD was 508 kW, the input CSD was 345 kW, and the ECWT was about 22 ° C. (72 ° F.). Thus, the “A” term (input constant speed kW / CSD design kW) is 345 kW divided by 508 kW, ie approximately 0.67. The “Y” term is about 22 (72). Substituting these values into equation [3] yields a value for “E” of approximately 0.56, which is the ratio of VSD input kW (“F”) divided by CSD design kW (E = 0). .56 = F / 530). This gives a value for a VSD input kW of about 297 kW.

  See FIG. 4, which is a constant velocity curve using refrigerant R134a to double check the results from the equation against the chart data. Line “K” is the y-intercept that extends horizontally from 0.67 (67%) to point “L”. Point “L” is an interpolation between an ECWT curve of about 21 ° C. (70 ° F.) and an ECWT curve of about 24 ° C. (75 ° F.) because the ECWT was about 22 ° C. (72 ° F.). is there. Tracing the vertical line from point “J” to the x-intercept, ie point “H”, yields about 80% load. Refer now to FIG. 5, which is a variable speed curve using R134a. Starting at 80% load, that is, starting from point “G” and following vertical line “M” to point “F”, ECWT was about 22 ° C. (72 ° F.), so that point was also about 21 ° C. Interpolation between an ECWT curve of (70 ° F.) and an ECWT curve of about 24 ° C. (75 ° F.). Tracing line “E” from point “F” to the y-intercept, ie, point “N”, is 0.54, which is within about 3% of the ratio calculated for E above. Since the calculation result obtained by using equation [3] was obtained from the previous calculation using equation [1], the calculated variable speed input kW of equation [3] is 3% at 0.56. It is noted that at least some of the differences can be derived from equation [1]. Thus, this example confirms that equation [3] defines the relationship between CSD performance and VSD performance of the refrigeration system.

  FIG. 12 exemplifies a flowchart clearly showing the control process of the present invention regarding cost comparison in the refrigeration system 10 shown in FIG. 13. The process begins at step 200 where values such as price per kW hour, variable speed design kW, and constant speed design kW are input to the control panel 40. The variable speed design kW and the constant speed design kW are values set by the manufacturer when the refrigeration system is commissioned and are intended to be input by the installer. The price per kW hour can be updated as needed. The display screen of the control panel 40 is typically set to either “total energy saving” or “total savings” (both displayed in US dollars). It is preferable that such information can be input to a keypad provided on the control panel 40.

  Once these values are input to the control board 40 at step 200, the refrigeration system is operational and at step 210, the control board measures parameters such as ECWT or other values related to operating performance. The Fahrenheit ECWT is preferably obtained from an analog input channel using a sensing element such as a thermistor. This information and other information may be supplied directly to the control board 40 or obtained from the control board 40. Further, in step 210, the input CSD kW data undergoes a change in response to the cooling load measured by the control panel 40, so that the input CSD kW data from the CSD or optional harmonic filter is at predetermined time intervals ( (Every 2 seconds, etc.) supplied to the control panel 40.

  After measuring the parameter, the value is calculated at step 220 and stored at step 230. The stored values can include not only the values calculated in step 220 but also the parameters measured in step 210. Some of the values calculated in step 220 and described below are outlined by the subject and further include consideration of measurement, calculation, and storage steps.

CSD kW hour meter This calculation can be performed as follows. That is, CSD kW is sent from the CSD to the control panel once every 2 seconds. This value is added to the CSDkW total. When this sum exceeds 1800 (3600 seconds per hour / 2 seconds per reading), this data collection rate is equivalent to 1800 kW at 1 kW, so the CSD kW hour meter increases by 1 kW hour and corresponds to partial kW time 1800 is subtracted from the CSD kW total, which resets the partial kW hour component of the CSD kW hour meter. The value of the CSD kW hour meter can be modified if the access level is set appropriately. Both the CSD kW hour meter and the CSD kW total are preferably stored in a storage device. AAA.

VSD kW Hour Meter Every 2 seconds, CSD kW is divided by CSD design kW to obtain CSD% design kW. Using ECWT and equations, the VSD% design kW is determined. This is preferably multiplied by the VSD design kW to obtain VSD kW. The VSD kW value is preferably added to the VSD kW total. When this sum exceeds 1800 (3600 seconds per hour / 2 seconds per reading), since 1800 kW is equal to 1 kW, the VSD kW hour meter is preferably incremented by 1 kW hour, and the 1800 corresponding to partial kW is Preferably it is subtracted from the VSD kW sum, which resets the partial kW hour component of the VSD kW hour meter. The value of the VSD kW meter can be modified if the access level is set appropriately. Preferably both the VSD kW hour meter and the VSD kW total are stored in the storage device.

  These examples illustrate the use of the present invention to compare a refrigeration system operating with CSD to a refrigeration system operating with VSD, but with two different VSDs, i.e., different configurations. It is also contemplated that the first VSD and the second VSD can be compared, or that two different CSDs can be compared, namely the first CSD and the second CSD. These comparisons can be performed as long as equations corresponding to the operation of the drive to be compared are given. It is also contemplated that more than two similar or different types of drives can be compared.

  Although the invention has been described with reference to preferred embodiments, those skilled in the art will recognize that various modifications can be made and equivalents can be substituted for the elements without departing from the scope of the invention. Will be understood. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Accordingly, the present invention is not intended to be limited to the particular embodiments disclosed as the best mode contemplated for carrying out the invention, but the invention includes all implementations falling within the scope of the appended claims. The form is included.

It is a schematic diagram which shows the refrigeration system for using for this invention. FIG. 6 shows a set of actual performance curves for a multi-functional refrigeration system using refrigerant R134a, using CSD, and having an inlet condenser water temperature of about 18 ° C. (65 ° F.). FIG. 6 shows a set of actual performance curves for a multifunction refrigeration system using refrigerant R134a, using VSD, and having an inlet condenser water temperature of about 18 ° C. (65 ° F.). FIG. 6 shows a set of curve fitting performance curves for a refrigeration system using refrigerant R134a, using CSD, and having an inlet condenser water temperature of about 7-35 ° C. (45-95 ° F.). FIG. 6 shows a set of curve fitting performance curves for a refrigeration system using refrigerant R134a, using VSD, and having an inlet condenser water temperature of about 7-35 ° C. (45-95 ° F.). FIG. 5 shows a curve fitting performance curve for a refrigeration system using CSD, superimposed by a refrigeration system using VSD, using refrigerant R134a, and having an inlet condenser water temperature of about 18 ° C. (65 ° F.). is there. FIG. 6 shows a set of actual performance curves for a multi-functional refrigeration system using refrigerant R123, using CSD, and having an inlet condenser water temperature of about 18 ° C. (65 ° F.). FIG. 5 shows a set of actual performance curves for a multi-functional refrigeration system using refrigerant R123, using VSD, and having an inlet condenser water temperature of about 18 ° C. (65 ° F.). FIG. 6 shows a set of curve fitting performance curves for a multifunction refrigeration system using refrigerant R123, using CSD, and having an inlet condenser water temperature of about 7-35 ° C. (45-95 ° F.). FIG. 6 shows a set of curve fitting performance curves for a multifunction refrigeration system using refrigerant R123, using VSD, and having an inlet condenser water temperature of about 7-35 ° C. (45-95 ° F.). FIG. 6 shows a curve fitting performance curve for a refrigeration system using CSD, overlaid by a refrigeration system using CSD, using refrigerant R123, and having an inlet condenser water temperature of about 18 ° C. (65 ° F.). is there. Fig. 6 is a flowchart for the process of the present invention showing a cost comparison of a refrigeration system using CSD versus VSD. It is a schematic diagram which shows embodiment by another method of the refrigerating system for using for this invention.

Claims (8)

A method for determining operating cost savings realized in connection with operation of a refrigeration system using a variable speed drive when compared to operation of a refrigeration system using a constant speed drive comprising:
Providing a refrigeration system;
The refrigeration system comprises a variable speed drive and a sensing element arranged to sense at least one operating parameter of the refrigeration system;
Providing a control device in communication with the sensing element;
The controller is programmed to perform a first process for determining a first operating cost associated with operation of the refrigeration system using the variable speed drive, and for the refrigeration system using a constant speed drive. Programmed to execute a second process for determining a second operating cost associated with driving;
Operating the refrigeration system using the variable speed drive;
Sensing at least one operating parameter of the refrigeration system;
Transmitting the sensed at least one operating parameter to the controller;
Performing the first process to determine the first operating cost according to the sensed at least one operating parameter;
Performing the second process to determine the second operating cost according to the sensed at least one operating parameter;
Comparing the first operating cost and the second operating cost to determine the realized operating cost savings of the refrigeration system;
Displaying the realized operating cost savings to a user ,
The second process for determining the second operating cost includes executing an algorithm that includes a polynomial for determining a ratio of a constant speed drive input kW to a constant speed drive design kW, the polynomial Is derived from a plurality of performance curves, each of the plurality of performance curves representing the performance of the refrigeration system using a constant speed drive at different water temperatures entering the condenser,
Method.   The method of claim 1, wherein the refrigeration system includes a compressor and a condenser, and wherein the at least one operating parameter comprises a temperature of water entering the condenser. The method of claim 2 , wherein the coefficients of the polynomial depend on a selection from the group consisting of a refrigeration type, a compressor type, a combination of a refrigeration type and a compressor type. The polynomial is
a + b × x + c × x ² + d × y + e × x × y + f × x ² × y + g × y ² + h × x × y ² + i × x ² × y ² e, f, g, h, i are coefficients, the variable x is the ratio of the variable speed drive input kW for variable speed drive designed kW, also variable y is the temperature of the water entering the condenser, claim 2 The method described. A method for determining an unrealized operating cost in connection with operation of the refrigeration system using constant speed drive when compared to operation of a refrigeration system using variable speed drive comprising:
Providing a refrigeration system;
The refrigeration system comprises a variable speed drive and a sensing element arranged to sense at least one operating parameter of the refrigeration system;
Providing a control device in communication with the sensing element;
The controller is programmed to perform a first process for determining a first operating cost associated with operation of the refrigeration system using the constant speed drive, and for the refrigeration system using a variable speed drive. Programmed to execute a second process for determining a second operating cost associated with driving;
Operating the refrigeration system using the constant speed drive;
Sensing at least one operating parameter of the refrigeration system;
Transmitting the sensed at least one operating parameter to the controller;
Performing the first process to determine the first operating cost according to the sensed at least one operating parameter;
Performing the second process to determine the second operating cost according to the sensed at least one operating parameter;
Comparing the first operating cost and the second operating cost to determine unrealized operating cost savings of the refrigeration system;
Displaying the unrealized operating cost savings to a user ,
The second process for determining the second operating cost includes executing an algorithm that includes a polynomial for determining a ratio of the variable speed drive input kW to the variable speed drive design kW, the polynomial Is derived from a plurality of performance curves, each of the plurality of performance curves representing the performance of the refrigeration system using variable speed drive at different water temperatures entering the condenser,
Method. The method of claim 5 , wherein the refrigeration system includes a compressor and a condenser, and the at least one operating parameter comprises a temperature of water entering the condenser. The method of claim 6 , wherein the coefficients of the polynomial depend on a selection from the group consisting of a refrigeration type, a compressor type, a combination of a refrigeration type and a compressor type. The polynomial is
a + b × x + c × x ² + d × y + e × x × y + f × x ² × y + g × y ² + h × x × y ² + i × x ² × y ² e, f, g, h, i are coefficients, the variable x is the ratio of the constant-speed drive input kW for a constant speed drive designed kW, also variable y is the temperature of the water entering the condenser, claim 6 The method described.

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