The main objective of this thesis was to design and create the Microsoft Excel based savings calculator for centrifugal pumps for energy auditions, which calculates the achievable sav-ings when substituting throttle control with variable speed drive control in the pumping sys-tem. The goal was also to require less input information from the user and calculate more accurate results than similar existing programs. Also some useful additional features were added to the designed program to make it more user friendly.
The accuracy of the results calculated by the designed program SCCP (Savings Calculator for Centrifugal Pumps) are verified by comparing them to the laboratory measurements done for one pump and to the three pump performance curves published by the manufacturer.
Designed program seems to be on average at least as accurate as one similar existing program ABB PumpSave, even it requires less input information. When comparing to the laboratory measured results, both programs, SCCP and PumpSave, give realistic results and they are almost equal in accuracy. On the basis of the comparison with manufacturer’s curves, PumpSave uses more accurate model for pump head curve, while SCCP has better model for pump efficiency. In comparison of the shaft power calculations accuracy, SCCP was more accurate in two of the three cases. SCCP has also some useful additional features, it calculates detailed financial information and provides an option to read the process flow profile from the text file and possibility to save calculation results and graphs as PDF report.
SCCP seems to calculate quite accurate results and it can be used reliably to help in invest-ment decision in energy efficient variable speed drives as a pumping system control. The designed program could still be made better by studying the accuracy of used models for pump, motor and VSD. More comparing with laboratory measurements for different sizes of pumps would be required to understand, if the pump model could be made more accurate.
Models for motor and VSD used in program are also not verified at all in this thesis, so one subject for further studies could be their verification and improvement of their accuracy.
REFERENCES
ABB Automation Group Ltd, 2002. Efficiency tool: User's Manual.
ABB Automation Group Ltd, 2012. PumpSave User's Manual.
ABB Automation Grout Ltd, 2014. PumpSave 5.3 Energy Saving Calculation Tool [Online]. [Accessed 6.10.2014]. Software is available at
http://new.abb.com/drives/software-tools/pumpsave
de Almeida, A. T., Fonseca, P., Falkner, H. & Bertoldi, P., 2003. Market transformation of energy-efficient motor technologies in the EU. Energy Policy, May, 31(6), pp. 563-575.
Europump and Hydraulic Institute, 2004. Variable Speed Pumping – A Guide to Succesful Applications, Elsevier, Kidlington, Oxford, UK.
Ferman, R., Hardee, R., Livoti, W.C., Pemberton, M., Tutterow, V., Walters, T., 2008. Op-timizing Pumping Systems: A Guide to Improved Energy Efficiency, Reliability & Profita-bility. Parsippany, New Jersey: Hydraulic Institute.
Fisher, I., 1896. Appreciation and Interest, The MacMillan Company, New York, USA.
Gülich, J.F., 2008. Centrifugal Pumps, Springer-Verlag, Berlin, Germany.
ISO 9906:1999, 1999. Rotodynamic pumps - Hydraulic performance acceptance tests - Grades 1 and 2.
ISO 9906:2012, 2012. Rotodynamic pumps - Hydraulic performance acceptance tests - Grades 1, 2 and 3.
Kaya, D. Alptekin Yagmur, E., Suleyman Yigit, K., Fatma Canka Kilic, Salih Eren, A., Cenk Celik, 2008. Energy efficiency in pumps. Energy Conversion and Management, 49 (2008), pp. 1662-1673.
Leonow, S., Mönnigmann, M., 2013. Soft sensor based dynamic flow rate estimation in low speed radial pumps, 2013 European Control Conference (ECC), July 17-19, 2013, Zürich, Switzerland.
Mustonen, P., 2013. Pumping System Optimizing Tool, Bachelor’s thesis, Lappeenranta Uni-versity of Technology.
Sârbu, I., Borza, I., 1998. Energetic optimization of water pumping in distribution systems.
Periodica Polytechnica Ser. Mech. Eng., 42, pp.141–152.
Taanila, A., 2013. Excel VBA-Ohjelmointi [Online]. [Accessed 22.8.2014]. Available at http://excelapu.wordpress.com/vba/
Tamminen, J., Kosonen, A., Ahonen, T., Ahola, J., Immonen, P., Muetze, A., Tolvanen, J., 2013. Component selection tool to maximize overall energy conversion efficiency in a pumping system, 2013 15th European Conference on Power Electronics and Applications (EPE), September 2-6, 2013
Taskinen, T., 2008. Calculation analysis of energy saving tools for fan and pump applica-tions, Master’s thesis, Lappeenranta University of Technology.
Vacon, 2014. VACON Save PC Tool [Online]. [Accessed 6.10.2014]. Software is available at
http://www.vacon.com/downloads/?DownloadCategory=Software+related&docu-ment+type=pc+tool#1724887359
VTT, 2008. Sähkönsäästöpotentiaali energiatehokkailla sähkömoottorikäytöillä Suomen energiavaltaisessa teollisuudessa.
LABORATORY EQUIPMENT
Pumping system in LUT pump laboratory is illustrated in Fig. I.1. System includes piping, reservoir and two centrifugal pumps. Piping and reservoir of the pumping system are equipped with multiple pressure, flow and temperature sensors. Pump shafts are equipped with torque and rotational speed sensors.
Fig. I.1 Drawing of pumping system in LUT pump laboratory. Pneumatically controlled valves are marked in red and green. The system is equipped with multiple different sensors.
The pumps in the laboratory are shown in Fig. I.2. System includes two centrifugal pumps, Sulzer APP22-80 on the left and Sulzer A22-80 on the right. The former was used in meas-urements of this thesis. Sulzer APP22-80 is driven by 11 kW ABB M3BP160M4 induction motor.
Fig. I.1 Pumps and motors in the laboratory. Sulzer APP22-80 on the left was used in the measurements of this thesis.
The induction motors in the laboratory are driven by frequency converters, shown in Fig.
I.3. Frequency converter used in measurements, ABB ACS880-01-032A-3+L503, can cal-culate the estimates of the torque and rotational speed values. Consumed electric power was measured with Fluke-1735 Power Logger.
Fig. I.3 Frequency converters in the laboratory. Right one, ABB ACS880-01-032A-3+L503 was used in measurements of this thesis. Fluke-1735 Power Logger used for electric power consumption meas-uring lies on the bottom of the picture.
MEASUREMENTS OF THE PUMP NOMINAL VALUES
The nominal values for the pump used in laboratory measurements Sulzer APP22-80 were defined on the basis of measured head efficiency and head curves. In measurements, pump was driven at constant rotational speed 1450 rpm and valve was first throttled from 100 % to 75 % and the opened back to 100 %. Sample rating in measurements was one per second and the valve position was changed 1 % every 30 seconds. The results of the measurements are shown in Fig. II.1.
Fig. II.1 Measurements of pump nominal values. Upper graph is pump efficiency curve and lower is pump head curve. The black dashed lines in QH curve graph illustrate the allowed deviations from man-ufacturers curve. The allowed deviation for head value is ±7% of the actual value and it’s defined in ISO 9906 (1999) standard. Pump efficiency curves are different, when throttling and opening the valve. This may be caused by hysteresis of the valve or sensors.
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As seen from the efficiency curve in Fig. II.1, there occurs hysteresis when operating the valve. The pump efficiency seems to stay better when valve is throttled than when it’s opened. This may be caused by the hysteresis of the valve or sensors.
In QH graph in Fig. III.1, measured head curve is compared to the manufacturer’s curve.
Black dashed lines in figure illustrate the allowed maximum deviation, which is ±7% of the actual value and it’s defined in grade 2 accuracy criteria in ISO 9906 (1999) standard. As seen, the measured curve is mostly inside allowed limits, expect at high flow rates.
On the basis of these graphs, the efficiency of the pump is η=66 % in nominal operating point where Q=90 m3/h and H=16.5 m. Nominal values specified by manufacturer are η=73
%, Q=100.8 m3/h and H=17 m.
TABLES OF LABORATORY MEASURED VALUES
Laboratory measurement were done to verify the results calculated by SCCP. Measurements were done for throttle controlled open loop system, and VSD controlled open and closed loop systems. Tables of laboratory measured values are shown in Tables III.1, III.2 and III.3 below. Measured quantities were valve position, rotational speed, flow rate, head, total effi-ciency, electric power and power factor.
Table III.1 Measured values for throttle controlled open loop system (Hst=5.8m). Rotational speed was 1450 rpm during the measurements.
Valve Position (%) Q(m3/h) H(m) ηtot(%) Pe(kW) cos(φ)
Table III.2 Measured values for VSD controlled open loop system (Hst=5.8m). Valve position was 82
% during the measurements to get to the best efficiency operating point with rotational speed 1450 rpm.
Table III.3 Measured values for VSD controlled closed loop system (Hst=0m). Valve position was 80 % during the measurements to get to the best efficiency operating point with rotational speed 1450 rpm.
EXAMPLE OF PUMP INFORMATION AND CURVES FROM SULZER SELECT
Pump information and performance curves to verify the program calculations were down-loaded from Sulzer Select online tool. Example of pump performance curves and infor-mation shown in Figs. IV.1 and IV.2 are for Sulzer APP41-300 C pump with 355 mm im-peller.
Fig. IV.1 Pump performance curves for Sulzer APP41-300 C pump from Sulzer Select online tool.
Fig. IV.2 Additional pump information for Sulzer APP41-300 C pump from Sulzer Select online tool.