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Implementation of Energy Metering Systems in Complex Manufacturing Facilities–A Case Study in a Biomedical Facility
Available online at www.sciencedirect.com
Procedia CIRP 1 (2012) 524 – 529
5th CIRP Conference on High Performance Cutting 2012
Implementation of energy metering systems in complex manufacturing facilities – A case study in a biomedical facility E. O’Driscolla*, D. Og Cusackb, G.E. O’Donnella a
Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Ireland b Biomedical Device Industry Focus Group, I2E2, Co.Cork, Ireland * Corresponding author. Tel.: +353-1-8963431 ; fax: +353-1-6795554 E-mail address: [email protected]
Abstract The continuing inflation of energy costs coupled with the imminent implementation of environmental taxes have placed the manufacturing sector under significant pressure to increase energy performance and reduce emissions. Current state of the art research is focused on reducing the energy consumption of machine tools and process chains. In order to quantify the impact of energy efficient machine and facility optimisations it is first necessary to robustly measure, map, and record the energy requirements of manufacturing facilities. Research projects in the area of machine tool energy performance optimisation are extensive; however, the attention given to the accurate and reliable quantification of machine tool and process chain energy requirements is not comprehensibly addressed in the literature. This paper provides an overview of industrial energy measurement technology and describes a methodology facilitating the effective installation of large scale energy metering systems in complex manufacturing facilities; with an Irish based case study. The aim of the project is to illustrate the benefits associated with absolute energy consumption transparency, only achievable through extensive and continuous power metering. The results of the project, as well as some limitations associated with large scale energy monitoring solutions are also discussed. © 2012 Authors. by Elsevier B.V.and/or Selection and/or peer-review under responsibility of Professor Konrad Wegener 2012 The Published byPublished Elsevier BV. Selection peer-review under responsibility of Prof. Konrad Wegener Keywords: Measurement; Manufacturing; Energy Efficiency;
1. Introduction Delivering goods and services more efficiently, using less energy, is a core component of today’s attempts to reduce global carbon emissions [1]. Improving energy efficiency remains the largest and least costly strategy for realising reductions in carbon emissions, according to the international energy agency (IEA) [2]. In manufacturing, energy cost has traditionally been only a small portion of the total production cost, and therefore, energy expenditure has received relatively little attention. The combination of increased energy prices, Kyoto protocol, and increased environmental awareness among consumers have forced management in manufacturing facilities to focus both time and capital on energy efficient process and facility optimisations [3]. Early studies in the area of energy conscious manufacturing predominantly focused on bridging the
gap between electricity consumption and machine tools [4, 5] followed by some more recent studies that proposed and discussed the ideology of life cycle engineering, design, and management [6, 7]. Contemporary research studies are still concerned with all of the above topics, however, there has been a shift in emphasis towards the modeling and energy orientated simulation of manufacturing process chains, as well as the embodied energy of products [8-10]. It is widely accepted that before power consumption in machining processes can be reduced it is necessary to quantify the amount of energy needed, to determine the degrees of freedom for an optimisation [11]. In the literature there is minimal attention given to the benefits and limitations associated with implementing an extensive energy measurement and quantification system in a complex manufacturing environment. The implementation of such a system has the potential to give absolute energy transparency; providing a platform
2212-8271 © 2012 The Authors. Published by Elsevier B.V. Selection and/or peer-review under responsibility of Professor Konrad Wegener http://dx.doi.org/10.1016/j.procir.2012.04.093
E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529
525
for the optimisation of a manufacturing facility at all hierarchical levels.
and also the characteristics of the electrical event (spectral content, duration, etc..,).
2. Energy and power measurement technology
2.3. Energy metering system communications
2.1. Data collection
The communication medium that energy meters utilise establishes the transmission quality, i.e. the speed, distance, and electromagnetic immunity. Power meters used in complex manufacturing applications utilise a wide variety of communication protocols ranging from traditional wired solutions (RS-232/RS-485) to cutting edge wireless systems. Some of the most commonly used communication mechanisms are:
Industrial power meters use both voltage and current sensing elements. Voltage measurements are recorded directly using voltage clips that are attached to an exposed wire forming part of the circuit being monitored. Current measurements are recorded indirectly through the use of current transformers or current transducers. Current transformers work by converting the primary AC current into a smaller secondary AC current, whereas current transducers take the primary AC current and output a DC voltage signal [12]. The accurate measurement of current is the more complex of the two as it requires a broader measurement range and also needs to handle a wider frequency range as a result of the rich harmonic contents of the current waveform. 2.2. Sampling rate The duration and type of event that a power meter can record is dependent on the sampling rate. The most basic metering devices sample at low rates (1 reported value per minute/hour) and report only low level information, for example, kWh’s. More advanced measurement and quantification solutions sample at very high rates (up to 750kHz) in order to identify transient events that appear and disappear within a fraction of a second [13, 14]. The sampling rate of a meter is also the main driver behind the unit cost as the following chart illustrates.
Fig. 1. Relationship between sampling rate and price for industrial power meters
Choosing the correct meter for the required analysis is a complex task and requires an understanding of both the meter characteristics (sampling rate, accuracy, etc..,)
• RS-232 RS-232 is an unbalanced transmission medium as only one wire carries the signal voltage. This communication method allows full duplex communications, supporting concurrent data flow in both directions. In an RS-232 system the transmitted signal is the voltage between the signal conductor and the common reference conductor. RS-232 supports point to point communications and this is a limiting factor for its application in large scale metering installations. Standards suggest RS-232 can operate at about 20 kbps over distances of 15 meters [13]. • RS-485 This is a half duplex communication system that provides good immunity to interference. RS-485 communications require two conductors to transmit each signal. The voltage at the receiving end is measured as the voltage difference between these two wires. This system type eliminates many of the interference problems associated with the common reference wire. RS-485 supports multi-drop applications as it is a single channel bus and this makes it suitable for a multiple device energy metering network. The maximum transmission distance is 1200 meters at 100 Kbps. Data rates up to 10Mbps are possible. • Ethernet Ethernet communication sends data via the carrier sense multiple access collision detection (CSMA-CD) method. Ethernet is available on three mediums, coaxial cable, shielded twisted pair and optical fibre. Optical fibres are popular because they are secure (absence of electrical currents), compact and immune to noise and electromagnetic interference [14]. Ethernet is a low cost method and it is widely used in industrial settings for a wide variety of automation and process control applications.
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E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529
• Wireless The majority of wireless meter networks used in industrial environments use a star, mesh or hybrid starmesh topology. Power meters communicating via wireless networks typically operate at the 802.11/Wi-Fi frequency or the 802.15/Zigbee. The decision on which band is most suitable is dependent on the required data transfer rate as well as the transmission distance. The graph below places each communication medium on an x-y graph of range and data transfer rate. The respective squares for each communication method represent the upper limit of the technology.
consumption greater than 5kW’s and a dynamic power profile (i.e. a kW demand outside of the 3ı limit during the screening test) require metering.
Fig. 3. Energy metering implementation methodology
4. Biomedical manufacturing facility case study
Fig. 2. Overview of industrial communication methods
3. Energy metering implementation strategy In order to ensure that measurement devices are installed at all of the correct locations within a manufacturing facility, a metering strategy was developed. The metering strategy, which is applicable to any manufacturing facility, is a number of sequential steps ensuring the most effective and cost efficient metering system is installed. The first phase of the metering implementation strategy is to install metering devices at the main electrical system points (level 1 components); site incomer, transformers, and also distribution boards. Beyond the high level electrical points, all significant energy users (level 2 components) identified in accordance with EN16001/EN50001 must be metered. A basic decision support tool is then required to effectively select the end use equipment (level 3 components) requiring fixed measurement devices. The selection criteria are as follows; 1. Equipment with static power consumption (i.e. a kW demand never more than 3ı from the mean during the screening test) over 20kW’s require metering. 2. Equipment with an average power
Ireland’s medical technology sector has evolved into one of the leading clusters for medical device and diagnostic products globally [15]. The sector is intensively regulated and certain regulations have a significant impact on energy consumption, for example, maintaining clean rooms appropriately (temperature control and air changes/hour) has a measureable energy requirement. The biomedical manufacturing facility forming the basis of this research covers an area of over 10,000m². Electricity is received from the provider through a main incomer before reaching one of three 1600 kVA transformers. The electricity then passes through one of fifteen distribution boards that service different areas of the plant. The facility in question required a flexible metering solution that could quickly and easily adapt to the movement of equipment to different locations on the plant floor. The level of data required from the meters was simple kW, kWh, and power factor information to feed into the existing building management system (BMS). To this end, the metering system needed to be capable of integrating with the pre-existing quality and site management systems. The meter that provided the best solution for the given application from a cost, functionality, installation, and support standpoint was the Episensor ZEM-61 wireless three phase electricity monitor (figure 4).
527
E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529 Table . 1. Sample of screening investigation results
Fig. 4. Episensor ZEM-61 3 phase electricity monitor [16]
Each ZEM-61 meter sends kW, kWh, and power factor information wirelessly, using 802.15.4 (Zigbee), to a SiCA gateway which is then linked (via ethernet) to a SiCA server that communicates directly to the existing BMS. The meters have a reporting rate of anywhere from 1 value per second to 1 value per hour and the rate at which each meter reports data is customisable depending on the process in question. In accordance with the metering implementation strategy, meters were installed at the main incomer and all of the distribution boards. Measurement devices were also installed at each significant energy user (including air compressors, chillers, extraction fans, etc.). The next step was to complete the screening study and monitor each piece of end use equipment with a portable power meter in order to assess the individual power profiles. The power consumption of all processes including metal cutting, measurement, coolant circulation, and laser marking were recorded for a period encompassing 3 complete machining cycles. The power profiles found during these screening tests supported the state of the art research from Herrmann, et al. [17], Dahmus, et al [18], and more recently Kara, et al. [9] outlining the inherent differences between the power consumption characteristics of various types of complex manufacturing equipment. The machine level investigations also reinforced the assertions of Gutowksi, et al. [19] that focused attention on the division between fixed (supporting) energy consumption and variable (direct) energy consumption in manufacturing environments. The screening tests illustrated a clear divide between the power requirements of machinery required directly for manufacture as opposed to equipment required indirectly. Production supporting activities including coolant pumps, extraction fans, and other equipment operating under fixed speed conditions require power at a constant rate during periods of activity. This contrasts with production equipment required directly for manufacturing (e.g. metal cutting machines and cleaning processes) that require power at a variable rate depending on machine state, e.g. idle, calibrating, removing material, etc. An example of some of the results obtained during the level 3 screening investigations is included in the following table.
Operation Type
Power Profile
Avg. Power (kW)
Meter Required
Milling
Dynamic
7.42
Yes
Coolant pump
Static
9.87
No
Sand blasting
Dynamic
2.84
No
Extraction fan
Static
34.26
Yes
Cleanline (large)
Dynamic
15.31
Yes
5. Experimental results and discussion Prior to the implementation of this metering system the organisation in question was unable to perform an analysis of their energy consumption patterns due to a lack of information. The newly installed energy metering system provides a level of energy consumption transparency that is typically only available in research labs and facilitates the use of statistical methods to analyse and forecast past and future energy consumption respectively. The organisation now assesses each significant energy user against an appropriate variable as a means to monitor the energy performance of the facility on a daily basis. For example the HVAC energy consumption is plotted against outside temperature and energy consumption for dust extraction is analysed alongside units shipped. Both of the above assessments produce strong correlations and deviations from expected values produce energy non conformances (in accordance with EN 50001), which must be rectified. The level of energy visibility now afforded to this facility resulting from the metering system is illustrated with a bottom up example in the image below.
Fig. 5. Energy consumption transparency resulting from the state-ofthe-art metering installation
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E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529
From a systems integration perspective, the metering system has combined seamlessly with the existent quality and management structures on site. The final metering installation has given the energy management team a new level of energy consumption visibility that was previously unavailable. The metering system has also allowed the development of energy performance indicators and goals in accordance with EN 50001:2011; the international energy management standard. The implementation of this metering project also facilitates the evolution of lean principles currently employed on site. For example, value stream mapping, a lean manufacturing concept, has traditionally been used on site to analyse and evaluate processes from a cycle time, takt time, and throughput perspective. It is now possible for this organisation to evolve its value stream maps and assess process chains from an energy consumption standpoint, in a real time environment. The completion of this type of value stream map will pave the way for value stream competition; a concept which will see value stream managers competing with each other within a single facility in order to have the lowest kWh/part (or other normalised metric) over an allocated time period.
will also allow the facility to accurately identify, prioritise, and record new opportunities for improving energy performance. In terms of metering system limitations, there are two main issues that need to be considered during the design stage; cost and data storage space. The system installed in the case study described here utilises power meters which only record basic electrical system information, i.e. kW, kWh, and power factor. Although it would be beneficial from a power quality perspective to monitor more complex characteristics (e.g. sags, dips, and harmonics) the associated rise in unit cost for each meter would increase the system price to such a degree that the project would no longer be cost effective. In addition to the inhibitive cost of a large scale power quality monitoring installation there would also be a prohibitive increase in the amount of storage space required to manage the data. Future work in this research project will focus on the application of statistical techniques to the data obtained from the metering system, with a view to further refining the EPI’s and also utilising the data to forecast future energy consumption based on planned production schedules.
6. Conclusions Acknowledgements The scale of the energy metering installation that has been implemented here is a first for an Irish based biomedical device manufacturing facility. The level of energy related information that is now available to the energy management team at this facility places the organisation at the leading edge of industrial energy measurement and management. This paper discusses the technology behind industrial energy measurement systems and provides an overview of the available communication methods. The decision regarding meter selection is based on the systems measurement requirements (power quality analysis or basic energy consumption information) as well as financial constraints. In terms of the metering systems communication, a decision on whether to install a wired or wireless infrastructure is dependent on the level of flexibility required in addition to the level of data being recorded and transferred. The results focus on the level of energy transparency achieved as a result of this project and how this improved visibility has enabled the organisation to further progress the lean principles currently employed on site by including energy in the lean framework. The energy metering system has also facilitated the development of robust energy performance indicators (EPI’s) and targets that are used as a benchmark to monitor and continuously improve energy efficiency within the site. In addition to the increased energy visibility and development of EPI’s, the metering system
The authors gratefully acknowledge the support of the Irish Research Council for Science, Engineering and Technology (IRCSET) for this ongoing research project. References [1] Cullen J M, Allwood J M. The efficient use of energy: Tracing the global flow of energy from fuel to service. Energy Policy, vol. 38, pp. 75-81, 2010. [2] International Energy Agency. Worldwide Trends in Energy Use and Efficiency. 94. 2008. [3] Muller D, Marechal M A, Wolewinski T, Roux J. An energy management method for the food industry. Applied Thermal Engineering, vol. 27, pp. 2677-2686, 2007. [4] De Filippi A, Ippolito R, Micheletti G F. NC Machine Tools as Electric Energy Users. CIRP Annals - Manufacturing Technology, vol. 30, pp. 323-326, 1981. [5] De Filippi A, Ippolito R, Micheletti G F. Forecast of the Electric Energy Requirement in a Mechanical Plant by Using a Stochastic Model. CIRP Annals - Manufacturing Technology, vol. 29, pp. 285-288, 1980. [6] Alting L. Life Cycle Engineering and Design. CIRP Annals Manufacturing Technology, vol. 44, pp. 569-580, 1995. [7] Westkämper E, Alting L, Arndt G. Life Cycle Management and Assessment: Approaches and Visions Towards Sustainable Manufacturing (keynote paper). CIRP Annals - Manufacturing Technology, vol. 49, pp. 501-526, 2000. [8] Herrmann C, Thiede S, Kara S, Hesselbach J. Energy oriented simulation of manufacturing systems - Concept and application. CIRP Annals - Manufacturing Technology, vol. 60, pp. 45-48, 2011.
E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529 [9] Kara S, Ibbotson S. Embodied energy of manufacturing supply chains. CIRP Journal of Manufacturing Science and Technology, vol. In Press, Corrected Proof, 2011. [10] Hesselbach J, Hermann C, Detzer R, Martin L, Thiede S, Ludedmann B. Energy efficiency through optimized coordination of production and technical building services. 15th CIRP International Conference on life Cycle Engineering, 17-19 March 2008 2009. [11] Larek R, Brinksmeier E, Meyer D, Pawletta T, Hagendorf O. A discrete-event simulation approach to predict power consumption in machining processes. Production Engineering, vol. 5, pp. 575579, 2011. [12] Koon W. Current sensing for energy metering. International IC – China (IIC-China) Conference and Exhibition and the Embedded Systems Conferences – China (ESC-China), Shanghai, 2002. [13] Abdel-Galil T K, Kamel M, Youssef A M, El-Saadany E F, Salama M A. Power quality disturbance classification using the inductive inference approach. IEEE Transactions Power Delivery vol. 19 pp. 1812-1818, 2004. [14] Gosbell V, Perera S, Smith V. Technical Note 5 – Power Quality Monitoring – Plant Investigations. Endeavour Energy Power Quality and Reliability Centre. Available www.elec.uow.edu.au, accessed on 20/02/2011 [15] Irish Medical Devices Association. Biomedical Manufacturing Sector Profile. 2011. Available: www.imda.ie, accessed on 23/02/2011 [16] Episensor. ZEM-61 Wireless 3 phase power meter - Technical data sheet. 2010. Available: www.episensor.com [17] Herrmann C, Thiede S. Process chain simulation to foster energy efficiency in manufacturing. CIRP Journal of Manufacturing Science and Technology, vol. 1, pp. 221-229, 2009. [18] Dahmus J, Gutowski T. An environmental analysis of machining. ASME International Mechanical Engineering Conference and R&D Expo, Anaheim, California, 2004. [19] Gutowski T, Dahmus G, Thiriez A. Electrical energy requirements for manufacturing processes. 13th CIRP international conference on Life Cycle Engineering, Leuven, 2006.
529
Procedia CIRP 1 (2012) 524 – 529
5th CIRP Conference on High Performance Cutting 2012
Implementation of energy metering systems in complex manufacturing facilities – A case study in a biomedical facility E. O’Driscolla*, D. Og Cusackb, G.E. O’Donnella a
Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Ireland b Biomedical Device Industry Focus Group, I2E2, Co.Cork, Ireland * Corresponding author. Tel.: +353-1-8963431 ; fax: +353-1-6795554 E-mail address: [email protected]
Abstract The continuing inflation of energy costs coupled with the imminent implementation of environmental taxes have placed the manufacturing sector under significant pressure to increase energy performance and reduce emissions. Current state of the art research is focused on reducing the energy consumption of machine tools and process chains. In order to quantify the impact of energy efficient machine and facility optimisations it is first necessary to robustly measure, map, and record the energy requirements of manufacturing facilities. Research projects in the area of machine tool energy performance optimisation are extensive; however, the attention given to the accurate and reliable quantification of machine tool and process chain energy requirements is not comprehensibly addressed in the literature. This paper provides an overview of industrial energy measurement technology and describes a methodology facilitating the effective installation of large scale energy metering systems in complex manufacturing facilities; with an Irish based case study. The aim of the project is to illustrate the benefits associated with absolute energy consumption transparency, only achievable through extensive and continuous power metering. The results of the project, as well as some limitations associated with large scale energy monitoring solutions are also discussed. © 2012 Authors. by Elsevier B.V.and/or Selection and/or peer-review under responsibility of Professor Konrad Wegener 2012 The Published byPublished Elsevier BV. Selection peer-review under responsibility of Prof. Konrad Wegener Keywords: Measurement; Manufacturing; Energy Efficiency;
1. Introduction Delivering goods and services more efficiently, using less energy, is a core component of today’s attempts to reduce global carbon emissions [1]. Improving energy efficiency remains the largest and least costly strategy for realising reductions in carbon emissions, according to the international energy agency (IEA) [2]. In manufacturing, energy cost has traditionally been only a small portion of the total production cost, and therefore, energy expenditure has received relatively little attention. The combination of increased energy prices, Kyoto protocol, and increased environmental awareness among consumers have forced management in manufacturing facilities to focus both time and capital on energy efficient process and facility optimisations [3]. Early studies in the area of energy conscious manufacturing predominantly focused on bridging the
gap between electricity consumption and machine tools [4, 5] followed by some more recent studies that proposed and discussed the ideology of life cycle engineering, design, and management [6, 7]. Contemporary research studies are still concerned with all of the above topics, however, there has been a shift in emphasis towards the modeling and energy orientated simulation of manufacturing process chains, as well as the embodied energy of products [8-10]. It is widely accepted that before power consumption in machining processes can be reduced it is necessary to quantify the amount of energy needed, to determine the degrees of freedom for an optimisation [11]. In the literature there is minimal attention given to the benefits and limitations associated with implementing an extensive energy measurement and quantification system in a complex manufacturing environment. The implementation of such a system has the potential to give absolute energy transparency; providing a platform
2212-8271 © 2012 The Authors. Published by Elsevier B.V. Selection and/or peer-review under responsibility of Professor Konrad Wegener http://dx.doi.org/10.1016/j.procir.2012.04.093
E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529
525
for the optimisation of a manufacturing facility at all hierarchical levels.
and also the characteristics of the electrical event (spectral content, duration, etc..,).
2. Energy and power measurement technology
2.3. Energy metering system communications
2.1. Data collection
The communication medium that energy meters utilise establishes the transmission quality, i.e. the speed, distance, and electromagnetic immunity. Power meters used in complex manufacturing applications utilise a wide variety of communication protocols ranging from traditional wired solutions (RS-232/RS-485) to cutting edge wireless systems. Some of the most commonly used communication mechanisms are:
Industrial power meters use both voltage and current sensing elements. Voltage measurements are recorded directly using voltage clips that are attached to an exposed wire forming part of the circuit being monitored. Current measurements are recorded indirectly through the use of current transformers or current transducers. Current transformers work by converting the primary AC current into a smaller secondary AC current, whereas current transducers take the primary AC current and output a DC voltage signal [12]. The accurate measurement of current is the more complex of the two as it requires a broader measurement range and also needs to handle a wider frequency range as a result of the rich harmonic contents of the current waveform. 2.2. Sampling rate The duration and type of event that a power meter can record is dependent on the sampling rate. The most basic metering devices sample at low rates (1 reported value per minute/hour) and report only low level information, for example, kWh’s. More advanced measurement and quantification solutions sample at very high rates (up to 750kHz) in order to identify transient events that appear and disappear within a fraction of a second [13, 14]. The sampling rate of a meter is also the main driver behind the unit cost as the following chart illustrates.
Fig. 1. Relationship between sampling rate and price for industrial power meters
Choosing the correct meter for the required analysis is a complex task and requires an understanding of both the meter characteristics (sampling rate, accuracy, etc..,)
• RS-232 RS-232 is an unbalanced transmission medium as only one wire carries the signal voltage. This communication method allows full duplex communications, supporting concurrent data flow in both directions. In an RS-232 system the transmitted signal is the voltage between the signal conductor and the common reference conductor. RS-232 supports point to point communications and this is a limiting factor for its application in large scale metering installations. Standards suggest RS-232 can operate at about 20 kbps over distances of 15 meters [13]. • RS-485 This is a half duplex communication system that provides good immunity to interference. RS-485 communications require two conductors to transmit each signal. The voltage at the receiving end is measured as the voltage difference between these two wires. This system type eliminates many of the interference problems associated with the common reference wire. RS-485 supports multi-drop applications as it is a single channel bus and this makes it suitable for a multiple device energy metering network. The maximum transmission distance is 1200 meters at 100 Kbps. Data rates up to 10Mbps are possible. • Ethernet Ethernet communication sends data via the carrier sense multiple access collision detection (CSMA-CD) method. Ethernet is available on three mediums, coaxial cable, shielded twisted pair and optical fibre. Optical fibres are popular because they are secure (absence of electrical currents), compact and immune to noise and electromagnetic interference [14]. Ethernet is a low cost method and it is widely used in industrial settings for a wide variety of automation and process control applications.
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E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529
• Wireless The majority of wireless meter networks used in industrial environments use a star, mesh or hybrid starmesh topology. Power meters communicating via wireless networks typically operate at the 802.11/Wi-Fi frequency or the 802.15/Zigbee. The decision on which band is most suitable is dependent on the required data transfer rate as well as the transmission distance. The graph below places each communication medium on an x-y graph of range and data transfer rate. The respective squares for each communication method represent the upper limit of the technology.
consumption greater than 5kW’s and a dynamic power profile (i.e. a kW demand outside of the 3ı limit during the screening test) require metering.
Fig. 3. Energy metering implementation methodology
4. Biomedical manufacturing facility case study
Fig. 2. Overview of industrial communication methods
3. Energy metering implementation strategy In order to ensure that measurement devices are installed at all of the correct locations within a manufacturing facility, a metering strategy was developed. The metering strategy, which is applicable to any manufacturing facility, is a number of sequential steps ensuring the most effective and cost efficient metering system is installed. The first phase of the metering implementation strategy is to install metering devices at the main electrical system points (level 1 components); site incomer, transformers, and also distribution boards. Beyond the high level electrical points, all significant energy users (level 2 components) identified in accordance with EN16001/EN50001 must be metered. A basic decision support tool is then required to effectively select the end use equipment (level 3 components) requiring fixed measurement devices. The selection criteria are as follows; 1. Equipment with static power consumption (i.e. a kW demand never more than 3ı from the mean during the screening test) over 20kW’s require metering. 2. Equipment with an average power
Ireland’s medical technology sector has evolved into one of the leading clusters for medical device and diagnostic products globally [15]. The sector is intensively regulated and certain regulations have a significant impact on energy consumption, for example, maintaining clean rooms appropriately (temperature control and air changes/hour) has a measureable energy requirement. The biomedical manufacturing facility forming the basis of this research covers an area of over 10,000m². Electricity is received from the provider through a main incomer before reaching one of three 1600 kVA transformers. The electricity then passes through one of fifteen distribution boards that service different areas of the plant. The facility in question required a flexible metering solution that could quickly and easily adapt to the movement of equipment to different locations on the plant floor. The level of data required from the meters was simple kW, kWh, and power factor information to feed into the existing building management system (BMS). To this end, the metering system needed to be capable of integrating with the pre-existing quality and site management systems. The meter that provided the best solution for the given application from a cost, functionality, installation, and support standpoint was the Episensor ZEM-61 wireless three phase electricity monitor (figure 4).
527
E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529 Table . 1. Sample of screening investigation results
Fig. 4. Episensor ZEM-61 3 phase electricity monitor [16]
Each ZEM-61 meter sends kW, kWh, and power factor information wirelessly, using 802.15.4 (Zigbee), to a SiCA gateway which is then linked (via ethernet) to a SiCA server that communicates directly to the existing BMS. The meters have a reporting rate of anywhere from 1 value per second to 1 value per hour and the rate at which each meter reports data is customisable depending on the process in question. In accordance with the metering implementation strategy, meters were installed at the main incomer and all of the distribution boards. Measurement devices were also installed at each significant energy user (including air compressors, chillers, extraction fans, etc.). The next step was to complete the screening study and monitor each piece of end use equipment with a portable power meter in order to assess the individual power profiles. The power consumption of all processes including metal cutting, measurement, coolant circulation, and laser marking were recorded for a period encompassing 3 complete machining cycles. The power profiles found during these screening tests supported the state of the art research from Herrmann, et al. [17], Dahmus, et al [18], and more recently Kara, et al. [9] outlining the inherent differences between the power consumption characteristics of various types of complex manufacturing equipment. The machine level investigations also reinforced the assertions of Gutowksi, et al. [19] that focused attention on the division between fixed (supporting) energy consumption and variable (direct) energy consumption in manufacturing environments. The screening tests illustrated a clear divide between the power requirements of machinery required directly for manufacture as opposed to equipment required indirectly. Production supporting activities including coolant pumps, extraction fans, and other equipment operating under fixed speed conditions require power at a constant rate during periods of activity. This contrasts with production equipment required directly for manufacturing (e.g. metal cutting machines and cleaning processes) that require power at a variable rate depending on machine state, e.g. idle, calibrating, removing material, etc. An example of some of the results obtained during the level 3 screening investigations is included in the following table.
Operation Type
Power Profile
Avg. Power (kW)
Meter Required
Milling
Dynamic
7.42
Yes
Coolant pump
Static
9.87
No
Sand blasting
Dynamic
2.84
No
Extraction fan
Static
34.26
Yes
Cleanline (large)
Dynamic
15.31
Yes
5. Experimental results and discussion Prior to the implementation of this metering system the organisation in question was unable to perform an analysis of their energy consumption patterns due to a lack of information. The newly installed energy metering system provides a level of energy consumption transparency that is typically only available in research labs and facilitates the use of statistical methods to analyse and forecast past and future energy consumption respectively. The organisation now assesses each significant energy user against an appropriate variable as a means to monitor the energy performance of the facility on a daily basis. For example the HVAC energy consumption is plotted against outside temperature and energy consumption for dust extraction is analysed alongside units shipped. Both of the above assessments produce strong correlations and deviations from expected values produce energy non conformances (in accordance with EN 50001), which must be rectified. The level of energy visibility now afforded to this facility resulting from the metering system is illustrated with a bottom up example in the image below.
Fig. 5. Energy consumption transparency resulting from the state-ofthe-art metering installation
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E. O’Driscoll et al. / Procedia CIRP 1 (2012) 524 – 529
From a systems integration perspective, the metering system has combined seamlessly with the existent quality and management structures on site. The final metering installation has given the energy management team a new level of energy consumption visibility that was previously unavailable. The metering system has also allowed the development of energy performance indicators and goals in accordance with EN 50001:2011; the international energy management standard. The implementation of this metering project also facilitates the evolution of lean principles currently employed on site. For example, value stream mapping, a lean manufacturing concept, has traditionally been used on site to analyse and evaluate processes from a cycle time, takt time, and throughput perspective. It is now possible for this organisation to evolve its value stream maps and assess process chains from an energy consumption standpoint, in a real time environment. The completion of this type of value stream map will pave the way for value stream competition; a concept which will see value stream managers competing with each other within a single facility in order to have the lowest kWh/part (or other normalised metric) over an allocated time period.
will also allow the facility to accurately identify, prioritise, and record new opportunities for improving energy performance. In terms of metering system limitations, there are two main issues that need to be considered during the design stage; cost and data storage space. The system installed in the case study described here utilises power meters which only record basic electrical system information, i.e. kW, kWh, and power factor. Although it would be beneficial from a power quality perspective to monitor more complex characteristics (e.g. sags, dips, and harmonics) the associated rise in unit cost for each meter would increase the system price to such a degree that the project would no longer be cost effective. In addition to the inhibitive cost of a large scale power quality monitoring installation there would also be a prohibitive increase in the amount of storage space required to manage the data. Future work in this research project will focus on the application of statistical techniques to the data obtained from the metering system, with a view to further refining the EPI’s and also utilising the data to forecast future energy consumption based on planned production schedules.
6. Conclusions Acknowledgements The scale of the energy metering installation that has been implemented here is a first for an Irish based biomedical device manufacturing facility. The level of energy related information that is now available to the energy management team at this facility places the organisation at the leading edge of industrial energy measurement and management. This paper discusses the technology behind industrial energy measurement systems and provides an overview of the available communication methods. The decision regarding meter selection is based on the systems measurement requirements (power quality analysis or basic energy consumption information) as well as financial constraints. In terms of the metering systems communication, a decision on whether to install a wired or wireless infrastructure is dependent on the level of flexibility required in addition to the level of data being recorded and transferred. The results focus on the level of energy transparency achieved as a result of this project and how this improved visibility has enabled the organisation to further progress the lean principles currently employed on site by including energy in the lean framework. The energy metering system has also facilitated the development of robust energy performance indicators (EPI’s) and targets that are used as a benchmark to monitor and continuously improve energy efficiency within the site. In addition to the increased energy visibility and development of EPI’s, the metering system
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