Energy Efficiency in Motor Systems

Inhaltsverzeichnis

1. Transformation Program for Low-Efficiency Electric Motors and Market Surveillance Activities in Turkey

   Mevlüt Hürol Mete

   Abstract

   “Industrial Energy Efficiency Action Plan” (IEEAP) within the context of the “Energy Efficiency Improvement Program” which is one of the primary transformation programs of the 10th Development Plan has been coordinated by the Ministry of Industry and Technology (MoIT). One of three key policy areas of this Action Plan outlines the goal of “increasing energy efficiency through transforming low-efficiency AC electric motors” for which MoIT has formulated national standards on electric motors following EU Commission Regulation (EC) No 640/2009 on electric motors.

2. The Public Energy Efficiency Policies Mapped and Implemented for the Industrial Motor Reconditioning Sector in Brazil

   Rodrigo Santos Vieira, George Alves Soares, Rodrigo Flora Calili, Glycon Garcia Junior, Reinaldo Castro Souza, Carlos Aparecido Ferreira

   Abstract

   In 2001, Law 10,295 established the process to make mandatory the minimum energy performance standards (MEPS) in equipment that consumes a lot of energy. About 25% of Brazil’s electric energy is consumed by loads connected to industrial electric motors (IEM), making them the main targets of public policies of energy efficiency. Led by this law, decrees and ordinances were created for IEM, which raised the minimum nominal efficiency level of these motors from low efficiency class IR1 to those of class IR3, that took effect in 2019. IR1, IR2 and IR3 are Brazilian efficiency classes which have the same values for nominal efficiencies of IE1, IE2 and IE3, except for 7 cases in which smaller efficiencies are allowed for motors built in smaller frames. After regulating the market of new motors, it was necessary to understand the market of repaired/reconditioning motors (RM). In 2013, a study (Souza RC, Dantas BF, Reis D, Sant’Anna H, Calili RF, Fagundes WDC, Final report – market research on refurbished engines, a proposal for the regulatory agency. PUC-Rio, Rio de Janeiro, 2013) was accomplished to analyze it. At that time, a large resale market of RM was identified, in which these motors are less efficient and with a major impact on the country’s energy consumption. The number of motors repaired is much larger than the number of new motors. Also, the RM sector is unstructured, maintenance companies do not have a representative association with the government, do not have defined technical standards and, generally, the employees do not receive adequate training in how to maintain the motors. This work has been used by the Ministry of Mines and Energy to create two major measures: the formation of a working group and the inclusion of RM in the Interministerial Ordinance Joint of 2017, which established the efficiency class IR3 as MEPS. This working group has been promoting the energy efficiency in RM with actions implemented in six areas: sector identification including a new market study (Souza RC, Calili RF, Vieira RS, Teixeira RSD, Market research on refurbished engines, a proposal for the regulator, technical report for international cooper association. PUC-Rio, Rio de Janeiro, 2019), qualification / training, consumer awareness, standardization, representativeness creation and energy regulation. This chapter shows the implemented public policy, their results, earnings and barriers.

3. Self-Assessment Tool for the Estimation of the Savings Potential of Electric Motor Systems

   Richard Phillips, Yannick Riesen, Nicolas Macabrey

   Abstract

   The industry and services sectors account for two-thirds of Switzerland’s total electricity consumption. Furthermore, a large portion of electricity consumption in the industry sector is attributable to electric motor systems. Several analyses were conducted during the past five years, and they all found that the savings potential lies between 20% and 30%. However, the companies still do not know the real savings potential of their electric motor systems. In view of this, several tools were developed in order to help them to assess it. This chapter presents a new all-in-one tool for the assessment of the savings potential of pumps, fans, compressed air systems and cooling compressors. Its design is such that companies can use it without assistance. If the data are available, the company can perform a more detailed analysis to increase the precision of the assessment by providing additional information, such as the ratio between the nominal power of the motor and the application (pumps, fans), the load profiles and the ratio between the nominal and maximum loads. Upon completion of this self-assessment, the company receives an estimation of the savings potential of its installations, as well as a list of basic efficiency measures to implement.

4. Labelling of Air Compressors – Much More Than Nameplate Data

   Peter Radgen

   Abstract

   Labelling of household appliances has been a success story by delivering information on energy consumption and the lifetime cost of operation of the appliances to private consumers. Energy efficiency labelling has triggered a boost of improvements. This paper addresses the difficulty of comparing energy efficiency data for air compressors, as the compressor manufacturers do not release them. The results demonstrate that a single energy efficiency value per compressor has only a limited value to identify the best product for the application. From the analysis and comparison of fixed speed and variable frequency drive air compressors, it is also demonstrated that compressors with variable frequency drive do not necessarily perform better than fixed speed compressors. The paper also stresses the importance of a compressed air system approach, being necessary to tap the largest energy-saving potentials in compressed air systems. The requirement to release complete data sheets of compressor packages sold in Europe similar to the USA is supported.

5. Theoretical and Experimental Evaluation of Compressed Air Leakages

   Manuel Unger, Peter Radgen

   Abstract

   The use of compressed air (CA) is common in almost every industrial sector and requires a significant share of the overall electricity consumption. Many studies have underlined the importance of energy efficiency in compressed air systems and have highlighted two key areas for the improvement of energy efficiency in compressed air systems, heat recovery and use and the reduction of air leakages. However, there is very little research so far on the quantification of air leaks and the effects and relations of leak configurations, pressures and air quality. The quantification of air leakages is still based on rather rough assumptions and calculations with a broad band of values and only few experimental evaluations.

   This chapter will describe the range of published leakage rates for predefined geometries and pressures, which shows deviations of up to 65%. Therefore, the calculation techniques and experimental setups of relevant publications are examined, highlighting their strengths and weaknesses. An improved and comprehensive simulation model for a detailed calculation of leakages will be presented. The model enables the user to vary a set of parameters (e.g. system pressure, system temperature, pressure dew point …) to gain a detailed understanding of leakage rates under different conditions.

   An experimental setup has been developed and commissioned. The setup allows the precise measurement of defined leakages. Experimental data are used to further improve and validate the simulation model. The chapter will present reliable data on leakage rates for standard geometries such as circular holes, based on high-precision measurements. The chapter will also describe the procedures how the artificial leakages are precisely manufactured and quality controlled. Encountered challenges will be discussed and the found solutions presented.

6. Digitalization in Electric Motor-Driven Systems

   Maarten van Werkhoven, Konstantin Kulterer

   Abstract

   Digitalization can bring ‘smart’ applications to all kinds of industrial energy systems, of which electric motor-driven systems take the largest part of the industrial electricity use. Electric motor-driven systems (EMDS) are currently responsible for some 53% of global electricity consumption, and approximately 70% of the industrial electricity use (International Energy Agency: World Energy Outlook 2016, IEA Paris, 2016; Digitalization and the future of energy, DNV GL, 2019). An optimal interaction of the respective motor system components (motor control, motor, mechanical equipment and application) combined with digital technologies bring about large energy savings in operation. The ‘addition’ of digital solutions can enlarge the scope of optimization, including efficiencies in operating cost (flexibility, procurement, life cycle), energy, materials (circularity) and emissions.

   While it is already possible to seamlessly record energy data from components to enterprise level (MES systems) from the hardware and software side, the next step would be (automated) control of the system based on this analysis. This could be done by using all relevant data (for example, order situation, operating status, product quality and quantity, environmental conditions) in real-time resolution to operate the machines in optimal operating condition.

   The IEA 4E EMSA develops activities to conduct impact assessments of technology developments in the field of industrial digitalization. Interest is into identifying the potential impact and possible or needed policy measures to stimulate the development and implementation of digital technologies towards more efficient motor systems in industry. Examples of related digital technologies and products are sensors and big data analysis, decision tools and new testing tools. The application of digital twins and artificial intelligence will enhance energy and motor management and maintenance and systems efficiency strategies. First assessments indicate a significant contribution i.e. an improvement of energy efficiency of 20–25% and an increase of operational efficiency of 25%. The effects towards related policy areas with regard to capacity building, pilots and regulatory issues will be made.

7. Calorimetric Efficiency Determination of Power Electronic Variable Speed Drives

   Stan Caron, Arne Berteyn, Pieter Defreyne, Steve Dereyne, Kurt Stockman

   Abstract

   A calorimeter test bench for the efficiency and power loss determination of power electronic variable speed drives is presented. The balanced calorimetric setup with air as the cooling medium is proposed to test small electronic drives for AC motors in a power range from 1 kW up to 7,5 kW. The construction, the required measurement equipment, the measurement procedure and especially the measurement results and uncertainty are important aspects of this test bench and are discussed in this chapter. The device under test is a 2,2 kW drive which is measured using both the input–output method and the calorimetric method. The test results are compared and conclusions are made concerning usability, repeatability and accuracy of the test bench. The overall goal is to further examine and optimize the calorimetric approach and to be able to obtain more accurate and comparable test results of very high efficient frequency converters. This setup reaches an uncertainty of ±2,39% or ± 1,48 W on the power loss at full load and speed using the calorimetric method.

8. Round Robin for Converter Losses: Uniform Testing Protocol and Results from Tests in Phase 1

   Conrad U. Brunner, Emmanuel Agamloh, Andrew Baghurst, Sandie B. Nielsen, Andrea Vezzini

   Abstract

   Variable frequency converters (VFC) are becoming more and more important elements of an energy-efficient electric motor-driven system (EMDS). They help to adjust the speed and torque of the motor output to the required load of the application and thus are a major source of energy savings. On the other hand, a variable speed-driven system adds more cost and complexity, and the converter causes additional losses both in its own electronics as well as in the driven motor. The losses of converters for electric motor-driven systems have never been systematically and independently verified, as there are no consensus test standards on the subject. Following the publication of IEC 61800-9-2, edition 1, 2017 (IEC 61800-9-2, edition 1: Adjustable speed electrical power drive systems – Part 9–2: Ecodesign for power drive systems, motor starters, power electronics and their driven applications – Energy efficiency indicators for power drive systems and motor starters, Geneva, Switzerland, 2017), the need for a more robust testing protocol and repeatable results of tests from independent laboratories emerged and was recognized both by 4E EMSA (IEA Technology Collaboration Programme on Energy Efficient End-Use Equipment (4E), Electric Motor Systems Annex (EMSA)) and IEC SC 22G WG18 (IEC, Subcommittee (SC) 22G for Adjustable speed electric drive systems incorporating semiconductor power converters, Working Group (WG) 18 for Energy efficiency of adjustable speed electric power drive systems).

   Also, the move by the European Commission to introduce in 2019 Minimum Energy Performance Standards for converter losses in the draft for the revision of the Ecodesign regulation no. 640 for motors (European Commission (EC), Commission Regulation No. 640/2009 of 22 July 2009 implementing Directive 2005/32/EC of the European Parliament and of the Council with regard to ecodesign requirements for electric motors, Brussels, Belgium, 2009) stimulated the research effort. Four independent labs (CalTest/Australia; DTI/Denmark; BFH/Switzerland and Advanced Energy/USA) agreed to team up for this project, financed by the four respective governments. Phase 1 of the Round Robin project started by the end of 2017 through early 2019. The goal of the project was to define/refine a proposed test method, known as Uniform Testing Protocol (UTP) and a Standard Reporting Format (SRF). By testing a number of converters, the project expected to provide a first feedback on the validity of the reference losses of the IEC standard.

   The phase 1 report of March 2019 (Agamloh E., Baghurst A., Brunner C.U., Nielsen S.B., Vezzini A., EMSA IEC WG 18, Round Robin of Converter Losses, Report of Results of Phase 1, Zurich, Switzerland, March 2019. Available at: www.motorsystems.org) [8] shows the results of 58 tests on nine converters between 0.75 kW and 11 kW. It documents excellent agreement of the results for losses and efficiencies. Between the four laboratories a high level of repeatability was achieved, despite the fact that 24 different load motors were used in the tests. The newly defined UTP testing methodology includes the precise definition of the product under test and its auxiliaries (filters, cooling fan, etc.), the selection of the nominal output current (rated or adapted to motor), the status of the converter (out-of-the-box, no automatic self-test run), the type and size of cabling and the preferred characteristics of the load motor (size vs. converter, rated current, IE-class, pole number, etc.). After the completion of phase 1, the UTP was updated with lessons learned into a new version (UTP2). About 60 converters are planned to be tested in phase 2 (Nielsen SB, Vezzini A, Preliminary results from (RR’C) round robin for converter losses, phase 2, in EEMODS’19 conference proceedings, Tokyo, Japan, 2019) from 2019–2020 [9]. With the updated UTP2, a sufficient quantitative data will be made available to WG 18 to revise the reference losses in IEC 61800-9-2, which are widely seen as too high. Eventually, also the efficiency classification can be revised in an edition 2 of the standard, which is planned for 2021 publication.

9. Preliminary Results from RR’C 2: Round Robin for Converter Losses, Phase 2

   Andrea Vezzini, Sandie B. Nielsen

   Abstract

   In the context of the revision of IEC 61800-9-2:2017 (IEC 61800-9-2, edition 1, Adjustable speed electrical power drive systems – Part 9–2: Ecodesign for power drive systems, motor starters, power electronics and their driven applications – Energy efficiency indicators for power drive systems and motor starters, Geneva, Switzerland, 2017) and the publication of an upcoming edition 2, several issues around converter losses need to be clarified. The testing method itself have been proven ambiguous as well as the reference losses which have been defined 5 years ago based on a simulation model that eventually appeared in a CENELEC standard EN 50598-2:2015 (CENELEC EN 50598-2, Ecodesign for power drive systems, motor starters, power electronics & their driven applications – Part 2: Energy efficiency indicators for power drive systems and motor starters, Brussels, Belgium, 2014). These values have never since been verified by actual tests of market products from different manufactures. The current test method has never been described in enough detail nor verified by independent test labs.

   On its meeting on 6 September 2017 at EEMODS’17 in Rome, representatives from IEC WG18 (IEC, Subcommittee (SC) 22G for Adjustable speed electric drive systems incorporating semiconductor power converters, Working Group (WG) 18 for Energy efficiency of adjustable speed electric power drive systems), 4E EMSA (IEA Technology Collaboration Program on Energy Efficient End-Use Equipment (4E), Electric Motor Systems Annex (EMSA) (European Commission (EC), Commission Regulation No. 640/2009 of 22 July 2009 implementing Directive 2005/32/EC of the European Parliament and of the Council with regard to ecodesign requirements for electric motors, Brussels, Belgium, 2009)) and several independent testing labs (“project group”) decided to have 4E EMSA to undertake the project leadership and the organization of a round robin exercise for converters cooperation with IEC WG18.

   Subsequently the round robin testing program for converter losses (RR’C) was established to serve as scientific base for establishing both a secured testing method and the necessary data base for converter losses through the entire range of 0.12 kW to 1000 kW that can be implemented in the coming revision of IEC 61800-9-2.

   In Phase 1 (from November 2017 to February 2019) the main goal was to establish a testing method that would be both accurate and repeatable and that would be practical for industry and research testing labs. The “Uniform Testing Protocol” (UTP) has been made available as ed. 2 by November 2018. Phase 1 was completed, and the final report discussed during the IEC SC22G WG18 Meeting in Melbourne, Australia (19–21 February 2019). Phase 1 results will be published in a separate paper at EEMODS’19 (Agamloh E, Baghurst A, Brunner CU, Nielsen SB, Vezzini A: EMSA IEC WG 18, Round Robin of Converter Losses, Report of Results of Phase 1, Zurich, Switzerland, March 2019. Available at www.motorsystems.org).

   In Phase 2 (from May 2019 to December 2020) the main goal is to validate the adapted testing method as well as establish a sufficiently wide data base of testing results over the entire range of converters between 0.12 kW to 1000 kW. In phase 2 the testing method shall also be verified in terms of “alternative” converter types such as active frontend converters.

   This chapter shall report intermediate results of the current status of RR’C phase 2 – Converter losses.

10. Embedded Estimation of Variable Speed Drive Input Current Distortion

    Thomas Devos, François Malrait

    Abstract

    This chapter addresses the estimation of the Total Harmonic Distortion (THD) of the drive input current, which is an interesting performance indicator of the variable speed drive. The analysis of the complete drive system is done (study of the dynamic model of the DC bus and its stability, frequency analysis of the input signals). A simplified estimator of the THD is proposed to be able to embed the calculation algorithm in real-time Drive control load with good accuracy and depending on the conduction mode of the DC choke (continuous or discontinuous).

11. Comparison of Fixed and Variable Speed Pumps Under Consideration of Manufacturer and Operator Aspects

    Sebastian Bold, Vincent Becker, Sven Urschel, Jochen Schaab

    Abstract

    Pumps are among the largest energy consumers in the industry and household sector. The operating point of a process is the decisive criterion for a plant operator when purchasing a pump system. To adjust the desired operating point of the pump, various methods are available. With the increasing number of variable speed drives, there is now another possibility to adjust the operating point. This study examines the effects of the use of variable speed drives on operators and manufacturers.

    For the operator, safe and energy-efficient operation of the pumps is particularly important. In order to carry out investigations here, a concrete application example is considered from the operators’ point of view. Two adjacent pump sizes are selected from a pump type series of a pump manufacturer and the smaller one is also operated with a variable speed drive. The measurement of these pump configurations shows that the variable speed operation of the pump is up to 6% more efficient than conventional operation.

    For the pump manufacturer, cost-efficient production and high product quality are important. With the help of variable speed drives, pumps can cover a larger operating area. This enables pump manufacturers to reduce their product range, which positively affects not only resource efficiency but also production and warehousing costs. In the application case it is shown that 71% of the pump sizes can be saved without any loss in efficiency.

    The conclusions elaborated in this study will help both plant operators and manufacturers to decide on the best way forward in terms of energy, resource and cost efficiency.

12. New Composite Containment Shell for Magnetically Driven Pumps

    Nicolas Weibel, Samuel Stutz, Daniel Rougnon, Frederic Perrottet

    Abstract

    Ten years ago, Greene, Tweed & Co. successfully introduced a carbon-fiber-reinforced polyetheretherketon (PEEK) containment shell under the trade name Xycomp®, to serve the API 685 seal-less pump market (Weibel, Bieler, Magnetic-coupled pumps: the containment shell. EEMODS’09, Paper #46, 6 May 2009). Today, we introduce a new material called Xycomp® DLF (i.e., Discontinuous Long Fibers) for lower pressure rated shells, targeting the ANSI/ASME market. This new material offers the same high-service temperature of 180 °C (350 °F) at a significantly lower price. It was originally developed to serve the Aerospace market, where it sees a great success and market traction. Creating pump-shells from Xycomp® DLF was an obvious match, as it allows eliminating the eddy currents generated by current metallic shells, and therefore offers significantly higher safety in case of an upset condition such as fluid starvation and subsequent dry running. Compared to other non-metallic shells, such as those made from ceramics, Xycomp® is non-fragile, insensitive to thermal shock, and does not build up electrostatic charges. Its failure mode is well understood and highly predictable as required for any Aerospace application.

    With current legislation requiring zero emissions when pumping fluids are identified as hazardous (e.g., carcinogenic, explosive, toxic), magnetically coupled pumps offer a reliable alternative to the expensive and maintenance-intensive, double mechanical sealed pumps. However, if a magnetically driven pump is lined with a metallic containment shell, the required power to drive the pump is increased due to the eddy current losses. To overcome the eddy current losses (15–25% for large pumps), additional power is needed, and it is not always available in existing buildings, leading to higher service cost. With Xycomp® DLF shells, the same power will be required to drive the impeller as a mechanically driven pump.

    This chapter presents the results of a large number of internal and field tests performed on many different Xycomp® shell sizes and pressure ratings, demonstrating the high reliability and advantages over other industry standard shells. Results include creep tests up to 204 °C (399 °F) for 10,000 h, statistical shell burst pressures from −196 °C to 200 °C (−320 °F to 392 °F), fatigue testing up to 36,000 cycles, dry running up to 12 min, sand erosion wear, pumped fluid temperature increase as a function of flow rate, thermal shock, fire burn through tests, thermal expansion, and impact resistance.

13. Hydraulic System Optimization

    Sandie B. Nielsen, Claus M. Hvenegaard, Otto Paulsen, Søren Draborg

    Abstract

    There are considerable opportunities for increased efficiency in hydraulic systems that can be realized through demand-oriented control methods and use of energy-efficient components. Experiences from studies shows that in many cases, a potential of up to about 50% can be realized compared to conventional systems (isbn: 978-87-91326-11-0).

    The project has developed a concept for optimization of hydraulic systems based on latest technology in components and controls compiled in a demand-driven approach. The demand-driven approach to system optimization and methods including necessary registrations for energy optimization of existing and design of new hydraulic systems was developed in the project (Hydraulic system optimization, research project report (349-016)).

    Furthermore, a new, independent tool for optimization of hydraulic systems is developed based on the latest knowledge about the operation of hydraulic. The tool is built on knowledge from the well-known Motor Systems Tool (Motor Systems Tool: http://motorsystems.org) as algorithms for motors, frequency converters are used in the hydraulic systems tool. The hydraulic systems tool compares eight different system setups based on specific data for system requirements as hydraulic flow and pressure from the hydraulic-operated equipment.

    In addition to the tool mentioned above, a guide for the design of energy-efficient hydraulic systems was developed since experiences show that the interaction between the capacity of the hydraulic pump, the accumulation tank, and regulation of hydraulic pressure relative to the actual needs is essential to ensure optimal energy-efficient operation.

    The main results of the project are:

    • Optimizing tool for hydraulic systems
    • Design guide for hydraulic systems
    • Draft handbook for hydraulics
    • Reporting incl. identification of potentials by sectors and technologies

    The project was funded by public means from the Danish ELFORSK Program (ELFORSK program webpage: www.elforsk.dk) and by the participating companies lead by Danish Technological Institute.

14. Comparison of Different Methods to Determine the Per-Phase Equivalent Circuit Parameters of Three-Phase Induction Motors Using IEC Nameplate and Catalogue Data

    Fernando J. T. E. Ferreira, André M. Silva, Edson Bortoni

    Abstract

    The per-phase equivalent circuit (EC) of three-phase, squirrel-cage, induction motors (SCIMs) is used to simulate their performance and for example to set motor control parameters in variable-speed drives. In this chapter, a new method based on a stochastic approach is applied to determine the EC parameters of IE1-, IE2-, IE3- and IE4-class SCIMs on the basis of motor nameplate and catalogue data, and the simulated motor efficiency, power factor and current curves, as a function of slip, are compared to those obtained with two deterministic methods, namely, the IEEE 112 F/F1 standard method (traditional method), based on the no-load and locked-rotor tests, and the method proposed in (Bortoni’s method), based on the motor nameplate and catalogue data. The proposed method is relatively fast and may lead to better results when compared to the deterministic methods.

15. Experimental Study on Three-Phase Induction Motor Performance Under Supply Voltage Unbalance for Star and Delta Connections

    Fernando J. T. E. Ferreira, José Alberto, Edson Bortoni, A. T. De Almeida

    Abstract

    In this chapter, an experimental study is presented comparing the performance of an induction motor under supply voltage unbalance at no-load and full-load, for star and delta connections. Using a programmable voltage source, one of the phase voltages that supplies the motor is reduced gradually down to 80%. Then, a comparison is made regarding the motor phase voltage and current deviations in relation to the nominal values. Moreover, the phase current deviations are used to estimate the winding temperature rise in the slots. Finally, for both connection modes, the maximum output shaft power for nominal temperature rise under unbalanced supply voltage is compared to the NEMA derating curve.

16. Conserving Energy in Compressed Air System: Practical Case Studies from Indian Industry

    Padmanabh Nagarkar, Prosanto Pal

    Abstract

    India is the second largest market for air compressors, and the market is growing at a rapid pace. All reputed international compressor manufacturers have their presence in India. Air compressors are widely used by large, medium, and small scale industries. Most large industries usually get their compressed air system audited regularly to save energy. However, SMEs cannot afford to engage the services of energy auditors to identify energy-saving options in their compressed air system.

    The authors have extensive experience of providing technical consultancy to SMEs on optimisation of their compressed air systems. SMEs typically use air compressors ranging between 20 and 300 hp. (15–224 kW approx.). Optimisation of compressed air system requires trained energy auditors and technical personnel. Our experience of working with SMEs shows that there is lot of confusion among the users about proper selection and best operating practices of air compressors.

    Some of our experiences with regard to compressed air system optimisation among Indian SMEs are shared in the chapter. Our studies on screw compressors show that there are three major energy conservation opportunities in compressed air system, viz. leakages, unloaded power, and artificial demand. Out of these three options, leakage and unloaded power concepts, are relatively simple to quantify and correct through energy audit studies. Air leakages are very simple to locate using ultrasonic meters. Adoption of variable speed drives for under loaded air compressor will result in substantial energy savings.

    However, the concept of artificial demand is more difficult in terms of acceptability and hence initiating corrective action. A higher compressor pressure causes the whole system to produce, consume, and waste more air than necessary. The authors have conducted several on-site capacity building programs for SMEs and built their capacities on what should be the minimum acceptable pressure and the pressure drop in the compressed air lines. A simple algorithm has been developed by the authors for correcting the receiver and pipeline sizing and reducing the artificial demand. This method works more economical than flow controllers.

    The chapter discusses some of the conventional energy-saving methods such as plugging of air leakage and minimising unloaded power in compressed air systems. In addition, some of the new technological developments, such as permanent magnet motors and inlet cooling systems, are also discussed. A detailed case study of actual compressed air optimisation in an SME unit is also presented.

17. Optimizing Pump and Compressor Selection for Energy Efficiency Using True-Weighted Efficiency (TWE)

    Trygve Dahl

    Abstract

    Energy efficiency is emphasized worldwide for motor-driven fluid-handling equipment including pumps, fans, blowers, and compressors. Energy production and consumption comes with financial and environmental costs, making energy savings an important aspect of the life cycle cost evaluation of the pump or compression system. True-Weighted Efficiency, or TWE, is a general purpose method to provide a single efficiency metric applicable to a machine operating under multiple operating conditions.

    The TWE method is derived from the first principles, based on useful fluid energy output compared to the energy input into the system. Generalized load profiles are used that include one or more control curves, multiple discrete operating points based on those control curves, and the time of operation at each operating point. This method is applicable to pumps, compressors, blowers, and fans operating at fixed or variable speeds, on/off operation, throttle control, or by-pass control.

    As background, the chapter includes a brief survey of legislation known as the Ecodesign requirements for water pumps, and more recently, the United States Department of Energy (DOE) legislation affecting the commercial sale of specific types of pumps or fans sold in the United States.

    In order to promote widespread use and understanding of TWE for commercial applications, this chapter provides a general outline of the theoretical method. The fundamental principles and governing equations are introduced along with a simplified TWE equation based on a specified load profile and weighting factors. Two case studies are provided illustrating the use of the TWE method for a pumping system and a turbocompressor. The studies reveal that the machine with the best design point efficiency is not always the best choice from a TWE and energy consumption perspective. The goal of the chapter is to promote broad understanding and use of this method to reduce energy consumption for pump and compressor applications (Chapter 55).