Wireless Sensor Network for Power Consumption Reduction in Information and Communication Systems Toshihiro Itoh, Yi Zhang, Mitsutaka Matsumoto, Ryutaro Maeda National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1, Namiki, Tsukuba, Japan, 305-8564
[email protected] JST, CREST, Japan of machines and peripheral facilities. A reduction of about 20% in energy consumption is reported by the real-time optimization of controls of the operation system of an oil refinery. It is estimated that there is a reduction of about 5% in energy consumption through unified management based on supply chain management (SCM) using technologies such as radio frequency identification (RFID) and allocation of vehicles through the most efficient routes. More than 40% reduction of the maximum energy consumption was achieved by the unified management and optimally coordinated operation of freezers and air conditioners at supermarkets and other stores. It is estimated that the energy consumption of TV and refrigerator for family usage could be reduced by 30% in next three year and 50% in next ten year, respectively by using ICT.
Abstract— This paper presents prototypes of wireless sensor nodes and network system for monitoring the power consumption of information and communication devices. Nowadays, carbon dioxide (CO2) emission in the information and communication technology (ICT) field is increasing enormously due to the high electric power consumption in ICT devices, e.g., in internet data centers (IDC) as well as offices and homes. In order to reduce CO2 emission from the ICT devices, it is very important to introduce energy management systems taking the advantages of wireless sensor network technology. In this study, we have developed the prototypes of a wireless current clamp probe integrated with a thermometer and a network system that enables simultaneous monitoring of 50 power lines. Using the sensor nodes and system, power consumption monitoring of several typical ICT appliances in home has been successfully demonstrated.
INTRODUCTION
Power Consumption (billion kWh)
I.
In the last two decades, there are rapidly increasing concerns about greenhouse gas concentrations in the atmosphere that might cause dangerous anthropogenic interference with the climate system. Therefore, Kyoto Protocol was adopted in the year 1997 and entered into force in the year 2005. Under Kyoto protocol, Japan proposed to reduce its CO2 emission by 50% by year 2050. After that, more and more interests and effort are concentrated into developing energy-saving technology and energy-efficient for less emission of carbon dioxide and other green gases. Information and communication systems technology (ICT) attracts much attention because it has been actively used in quiet a large number of fields including industry, transportation, business and homes. ICT not only gives positive impacts on energy efficiency of those fields but also greatly reduces the environmental burden by improving their operational efficiency. In particular, ICT is important in improving energy efficiency of many activities from production, distribution, transportation to endapplications in Japan [1]. For example, energy consumption has been reduced by about 12% for the manufacture of automobiles by using a system that synchronizes operations
978-1-4244-5335-1/09/$26.00 ©2009 IEEE
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Power Consumption (billion kWh)
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Figure 1 Estimation of ICT electricity consumption (Source: METI / Green IT Promotion Council (2008))
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ICT as well as ICT-driven technologies. Different from traditional concept of Green IT for reducing energy consumption, this project also aims to develop energyefficient society by ICT technology.
However, with more applications, not only more ICT devices are used including servers, network equipments, PCs and displays, but also the amount of data traffic on the internet will be 100-200 times its present value by the year 2025. Correspondingly, the electricity power consumption of ICT technology is increasing enormously. For example, a report says that the electricity consumption of ICT devices is estimated to grow to be 20% of total generated electricity power in the year 2025 than that of today [2]. In Japan, as shown in figure 1, the electricity consumption of ICT would increase by about 4.2 times by the year 2025. At the same time, in the worldwide, the electricity consumption of ICT would grow to be 15% of the total generated electricity power, i.e., it would increase by 8.4 times. It is also noteworthy that the energy consumption of IDC is rapidly increasing with the developing of commercial IDC as well as large power-consumed servers. It could draw the conclusion that CO2 emission in the ICT field should be reduced by the requirements of Kyoto Protocol. New energy management technology should be developed for ICT field. Since April 2008, the Green IT Project has started in Japan, to develop innovative technologies to achieve a drastic reduction of energy consumption for entire network systems including data centers, in addition to saving energy IT devices. These innovation technologies would also promote utilization of more energy-efficient products and improve productivity by the introduction of
Sensor networks, one of the most promising next generation ICT, are expected to be utilized for health [3] and security [4] applications as well as environmental monitoring [5] and control ones. It is reported in particular that sensor networks for facility energy controls can generate positive economic impact of 25 billion USD or reduce 15 million ton CO2 in the year 2010 [6]. Sensor network could enable live visualization of power consumption and CO2 emission so that energy efficiency could be better. This is very attractive for the energy-management systems of ICT devices in existing information data centers (IDC) as well as offices and homes. It is particularly interesting for us also because of rapid progress of information society in both developed and developing countries resulted in huge market potential. Our research team has been developing ultra low power (ULP) wireless sensor node and network systems to visualize the energy consumption of ICT systems in the CREST project “Optimum Control of Electrical Power in IT Systems by ULP Networked Sensing Systems” of JST, Japan [7]. This paper would present development of prototype of such wireless sensor node including its wireless communication module and sensor interface circuits, as well as graphic user interface.
Power Consumption HEMS
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Home
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Visualization of CO2
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Wireless Sensor Node for Power Consumption Monitoring
Office
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BEMS ULP IDC
Low Energy Society Figure 2 Concept of wireless sensor based power consumption monitoring system for ICT devices.
II.
interface circuits, a diode temperature sensor, and a clamp-on type current transformer having two jaws which open to allow clamping around an electrical conductor. Table 1 shows specifications of the key components used in the prototype of sensor node. The sensor node can detect the flow of current with the help of the current transformer and
SENSOR NODE AND NETWORK SYSTEM
Figure 3 shows a prototype of the wireless sensor node for detecting the power consumption of devices. Each node consists of a wireless communication module, sensor
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the circumambient temperature. The sensor node can detect the power of 1 – 1500 W, since the small clamp-on type current transformer (CTL-6-S32-8F-CL, U.R.D., Ltd.) can be applied to the current range of 0.01 – 15 Arms. The wireless communication module includes a low-voltage and low-power microcontroller unit (C8051F930, Silicon Laboratories) and single-chip 2.4 GHz transceiver (nRF24L01, Nordic Semiconductor ASA). Since the microcomputer can be operated with 0.9 V at minimum and has a built-in dc-dc converter, the module can work with one 1.5 V button-type battery. When using a battery of 100 mAh, the sensor node with transmission once a second was working continuously throughout two months. If the transmission frequency is set to be once a minute, the sensor node could work throughout 10 years and be described as a “maintenance-free” node.
USB-Receiver
Figure 4 Prototyped monitoring system with the GUI.
III.
DEMONSTRATION
Utilizing the sensor nodes and system, power consumption monitoring of several typical ICT appliances in home has been demonstrated, as shown in Figure 5. In this case, it was found that the power consumption of the plasma TV is very large compared to that of other ICT devices such as laptop PCs and wireless router. We can say that this kind of wireless energy monitoring system can be easily introduced to existing facilities and be effective to improve their energy efficiency. 1000
Power Consumption (Wh)
Laptop PC (x2) (AC Adapter)
Figure 3 Wireless sensor node integrated with a current clamp probe and thermometer.
Table 1 Key components of prototype of wireless sensor node Clamp-on Type AC Current Sensor CTL-6-S32-8F-CL [8] MCU C8051F930 [9]
Transceiver IC nRF24L01 [10]
- Dimensions (mm): 18W x 25H x 18t - Windng (Turn): 800 - Current Range (Recommended): 10 mA – 15 A - Supply Voltage: 0.9 – 1.8 V (One-cell mode operation) - Built-in dc-dc converter with 1.8 – 3.3 V output (65 mW max) - Typical sleep mode current < 0.1 μA - 10-Bit Analog to Digital Converter - 2.4-2.5 GHz ISM band - Minimum supply voltage: 1.9 V - Supply current in TX mode @ 0dBm output power: 11.3 mA - Supply current in Power Down mode: 900 nA
Wireless Router
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TV (PDP) Refrigerator Switchboard (Total)
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Figure 5 Example of power consumption monitoring for ICT devices in home.
IV.
SUMMARY
We have developed prototypes of wireless sensor nodes and network system for monitoring the power consumption of information and communication devices. The prototype of sensor node is a wireless current clamp-on type probes integrated with a thermometer and the system enables simultaneous monitoring of 50 power lines. Using the sensor nodes and system, power consumption monitoring of several typical ICT appliances in home has been successfully demonstrated. The developed system can be applied to energy management systems to reduce CO2 emission from the ICT devices in internet data centers (IDC) as well as offices and homes.
Figure 4 shows the monitoring station with the graphic user interfaces (GUI). The receiver is connected to the PC through the universal serial bass (USB) interface. The system can monitor the AC current and circumambient temperature of different 50 devices simultaneously. The monitor displays power consumption and circumambient temperature of each device in the room.
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ULTRA-LOW POWER WIRELESS SENSOR NODE”, Ibid., pp. 542-545. [5] J. Hayes, S. Beirne, K.-T. Lau, and D. Diamond, “EVALUATION OF A LOW COST WIRELESS CHEMICAL SENSOR NETWORK FOR ENVIRONMENTAL MONITORING”, Ibid., pp. 530-533. [6] http://www.soumu.go.jp/s-news/2004/040806_4.html [7] http://www.jst.go.jp/kisoken/crest/pdf/crest_eng_pamph.pdf [8] http://www.u-rd.com/english/products/ac/ac_3.html [9] https://www.silabs.com/products/mcu/lowvoltagelowpower/Pages/def ault.aspx [10] http://www.nordicsemi.com/files/Prod_brief_RFSilicon_nRF24L01.p df
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