The EcoSense Project: an intelligent energy management system with a wireless sensor and actor network Pedro Díaz1, Teresa Olivares1, Raúl Galindo1, Antonio Ortiz1, Fernando Royo1 and Tomás Clemente2 1
Albacete Research Institute of Informatics, Campus Universitario, 02071 Albacete
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Professors Centre, Avenida España, 13, 02004, Albacete
(pedrodiaz, teresa, raul, amanuel, froyo)@dsi.uclm.es,
[email protected]
Abstract Wireless sensor networks provide a new way of working for applications such as indoor monitoring, security or robotics. The Ecosense project aims to monitor all devices consuming energy in an intelligent building. We are developing this project in steps. Firstly, we have deployed a network equipped only with sensors (for temperature, humidity, luminosity, and electrical consumption, as well as presence detectors). Secondly, we will add an upper layer of manager agents (actors) to communicate and negotiate services. Afterwards, we will obtain conclusions about the sensed data and we will then extend a full wireless sensor network to cover the whole building. The network prototype will also be used to test power-and-time efficient protocols developed by us.
Introduction Sensor networks have been identified as one of the most promising technologies for the future, mainly due to the wide range of real-world applications that have already been identified for this technology. WSNs have the ability to sample, coordinate and actuate at time scales and network dimensions not previously possible [1]. This ability should enable the deployment of a wide array of interesting applications. Our research group at the Albacete Research Institute of Informatics [2] is actively involved in the study and deployment of this technology for indoor and outdoor monitoring. The Ecosense project has been motivated by the aim of effectively designing and deploying WSNs for monitoring environmental indoor conditions, such as the temperature and humidity in an office space. Also, our project includes the design and the implementation of a control system in a building with a wireless sensor network to monitor the situation of all devices that are consuming energy.
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To start with, the network is working only with sensors, and then, in a second phase, the system will be equipped with actors to permit the disconnection of devices and the sending of advice about controlling consumption. These actors may be agents with capabilities including goal management and task execution. Thus, the objective of the project is to set up a control system in the Albacete Research Institute of Informatics with a wireless sensor network to manage their energy consumption and to help with the decisions about energetic reduction. Sensors may also be used by an upper layer of manager agents. These agents are able to communicate and negotiate services to achieve the required functionality [3]. In this paper we describe the sensor network deployed and, after a data gathering phase, we will install the agents to control the sensors. Collaborating with us is the AGECAM, the regional Energy Agency of Castilla-La Mancha [4].
The Ecosense project hardware description We are deploying a smart wireless sensor network in the Institute building, to monitor it and optimize its energy resources. The project is divided into several phases: 1. Deployment of a small wireless sensor network in a room of the building and analysis of the results; 2. Addition of actors to this wireless sensor network in order to improve energy saving and 3. Extensions of the wireless sensor network, to cover the whole building. In terms of building energy saving there are several factors that have to be considered and studied carefully: temperature outdoors and indoors, luminosity, electrical consumption and presence detectors (passive infrared detectors, door and window opening sensors). Another variable considered in this project is the humidity, as it has been demonstrated that a good level of humidity in working areas is healthy for the workers. The main variable in energy control is the temperature, as we have to establish a comfortable temperature for work, and the energy consumed by the air conditioning in cooling the room, or by the heaters, depends to a great extent on this factor. To measure this variable it is not enough to collect data only at one point in the room, we have to deploy several temperature sensors in the room and calculate the average temperature. To optimize energy consumption as much as possible it is very useful to also install a sensor measure the outdoor temperature. In this case we can compare both temperatures. If, for example, outside is colder than inside and we want to cool the room, instead of turning on the air conditioning it is preferable to open the window, reducing in this way the energy consumed by these devices. The device chosen for this task is the embedded system MTM-CM5000-MSP made by Maxfor Technology INC (see fig.1) [5].
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Figure 1 Maxfor sensor node Some advantages of this node are the IEEE 802.15.4 compliant wireless sensor network platform, the fact that it also supports TinyOS, has temperature, light and humidity sensors embedded in the main board, and has an expansion connector that allows other sensors and devices to be plugged into it. The sensor network distribution is shown in fig.2
Figure 2 Sensor network distribution The outdoor sensor node, (1) in fig.2, is used to measure temperature, humidity and luminosity outside the building. The platform assigned to this task is the same as for indoors (MTM-CM5000-MSP), together with a new solar supply prototype that avoids the use of batteries. This is the device called ATON-II, a prototype developed by us in our laboratory [6]. ATON-II is tied to the MTM-CM5000-MSP through its expansion connector and it manages in a smart way the photovoltaic energy adapting the voltage level, filtering noise to avoid node malfunction, and storing the remaining energy in an accumulator in order to be used when the ambient light is not enough to supply ATON-II (see fig.3).
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Figure 3 The ATON II prototype ATON-II uses a small 7x4cm solar panel and a 50F high-density capacitor as an energy storage device. When the capacitor is fully charged, ATON-II can supply the MTM-CM5000-MSP without light for up to four days. In order to know if the windows are opened or closed there are some sensors that can control this event. These are the sensors labeled as (2) and (3) in fig.2. The device used is a magnetic switch plugged into the Maxfor node through its expansion connector; this switch can interrupt the node, detect the window event and send this event to the main server. To collect more data about temperature, humidity and luminosity at different points in the room, these Maxfor nodes also get data about these variables. In addition, some sensor nodes are responsible for detecting people. These sensors are labeled (4) and (7) in fig.2. Node (4) uses a motion detector based on passive infrared (PIR), and this device is plugged into the Maxfor node and interrupts it, triggering the sending of data to the server of the motion detect event. The sensor labeled (7) in fig.2 can also monitor people´s actions. This control is carried out through the open/close door event. For this task we use the same magnetic switch plugged into the Maxfor node as nodes (2) and (3). It is very important to know if there are people in the room, otherwise the air conditioning or the heaters are using energy that could be saved. Besides energy control in the building, we install some sensors in order to create a safe place of work and control it in terms of security. Along these lines there is one sensor used as a smoke detector. This is the sensor node labeled (5) in fig.2. The device that detects the event of fire or smoke is a commercial one adapted to plug into the sensor node. Like the other sensors, this device is tied through the expansion connector of the node and when it detects the event, the node sends this data to the main server and produces an acoustic signal as an alarm. Finally, in order to measure and monitor the energy consumed, instantaneously, and to perform data collection with energy trends over time, we have to insert a new sensor device. This sensor is placed in the room of the electrical cabinets; in fig.2 this sensor is labeled (8). We have developed a device that can measure this variable without the need to disturb the electrical installation. The principle on which the device is based is the magnetic field generated by the wires of the installation. Through the magnetic field and a specific transducer we can obtain a voltage depending on the current
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through one wire. This device consists of a ferrite core surrounding the specific wire with a magnetic transducer inside it. The connection is shown in fig. 4.
Figure 4 Connection of the magnetic field sensor The output from the device has to be managed to adapt the levels of voltage. We have implemented this intermediate stage in order to plug it into the Maxfor sensor node. The nodes making up the Ecosense project, gathering and storing data, are also used as a special platform to create a testbed. This testbed is very important in our laboratory because there are many activities related with the development of energy-efficient protocols. Our power-efficient work methodology integrates different energy-aware network protocols through the principles of cross-layer protocol engineering. We focus on the medium access control and network layers, as the radio device is the most power -consuming device. We have developed an optimal architecture for sensor networks [7] and we need to test the different protocols that operate in this architecture.
Our Sensor Testbed Sensor Network testbeds provide a platform network that can be used for realtime analysis and evaluation of a sensor network application. Experimental evaluation through testbeds is a fundamental step in most of the research projects in sensor networks in the main universities of the world. Moreover, testbeds together with a simulation and the later deployment of the hardware and software evaluating a real platform will help us to obtain reliable and innovative sensor network prototypes. Some related projects in this field are the testbeds developed in the following universities: University of Harvard. Motelab [8] is a wireless sensor network testbed deployed in the Maxwell Dworkin laboratories. This testbed is composed of MicaZ sensor nodes plugged by Ethernet through UTP cable to a central server. This testbed has a web interface to interact with the system and a database system (MySQL server). Ohio State University. Kansei [9] is a testbed divided into three subsystems: static array, portable array and mobile array. The static array consists of 210 sensor nodes deployed in a square platform separated by 75 cm.
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As sensor nodes, the Extreme Escala Motes (XSMs) are used. University of Harvard BBN Technologies. Citysense [10] is a testbed composed of more than 100 wireless sensors deployed around the city on streetlight posts, and private and public buildings. Each node is composed of a computer with a WIFI interface. The sensors monitor environmental variables and atmospheric pollution. As a result, this is an example of how a testbed can be deployed that covers a whole city and which is not focused on a laboratory or research center. In the last few years, in our laboratory we have tested the sensor network protocols through simulators and emulators. After testing we implement these applications and protocols in real sensor networks such as IntellBuilding [11] and WiseVine[12]. In these real sensor networks we have the problem of the power supply, and we lose data packets and so we cannot make a reliable study of our protocols because the final results are affected. As a result theI3ASensorBed was born. We needed a real cabled sensor node platform in order to test our applications and protocols easily, without the problem of power supply. The architecture of our system is organized in a tree. This tree form has three levels; each level is interconnected via different technologies. On the one side, there are the sensor nodes MTM-CM5000-MSP (they are the final devices or the leaf) tied through USB cables to special nodes called super nodes. Finally, as root of the tree there is a central server to which the super nodes are connected through an Ethernet network. The use of these super nodes is due to USB standard restrictions. If we use only USB connections, the maximum number of nodes will be 127 and with a distance of 30m between nodes. For this reason we need a change between the USB environment to the Ethernet one with UTP cable and RJ45 connections because these kinds of networks are cheap and accessible. There are some devices on the market that can connect USB massive storage devices through an Ethernet network, but our sensor nodes, although they have USB connectors, are not like storage devices and we need to modify some factors in the firmware. For this reason we have to find a new solution. As a consequence, we use a specific device by Linksys, the Network Storage Link for USB2.0 (NSLU2). This device has firmware based on the Linux O.S. and consequently the source code is released by Linksys. It has permitted us to modify the firmware and install a full version of Linux for embedded devices (Debian version). Thus, we have a full computer with Ethernet connections and USB ports for a small cost (less than 100€).
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Figure 5 (left) Linksys Network Storage Link for USB2.0, NSLU2, (right) Partial view of room NSLU2 has an Ethernet port and two USB ports, shown in fig.5, right. This device uses an Intel IXP420 processor of the XScale family, and runs at 133Mhz. It has 32 MB of SDRAM and 8 MB of flash memory. In the environment of each layer of the tree architecture there can exist other intermediate devices, so between the node layer and the super node layer USB hubs can be deployed in order to connect more USB nodes into the same super node. Furthermore, between the super node layer and the server there exists an Ethernet switch in order to connect several super nodes to the central server. Fig 6 shows the complete tree architecture of the I3ASensorBed.
Figure 6 Tree architecture of the I3ASensorBed
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The device used as USB hub is the USB2HUB4 by Linksys. It is very useful in our application because we can turn on or turn off the sensor nodes in order to test the network application in a better way. Lastly, we have the central server. This element will control all the system, interacting directly with the super nodes through the Ethernet connection of the testbed. This machine offers the necessary network services for the correct working of the super nodes in the testbed: DHCP, DNS, NTP and NFS. The server will offer a database to store the testbed information. The data-base motor is based on PostgreSQL because it is a robust, stable and free code. Another function of the server is to send scripts through the ssh connection to the super nodes in order to interact with the sensor nodes. The interaction with the user is by means of a web interface; so this machine will be a web server too (see figure 7). Through the web interface the final user can program, reset, turn on or turn off and activate the serial forwarder in a specific node or a group of nodes chosen by the user. In order to implement this interface we use a work environment based on Python and Python Twisted Tools.
Figure 7. I3ASensorBed web interface
Conclusions and Future work We have set up a cabled and controlled network in an indoor environment. This network will help us to monitor all important parameters for making an energy
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study. We wish to obtain categorical conclusions about energy efficiency in our building, and after this, to take actions to improve the consumption and working environment. However, this network is not a simple and experimental macroscope of our building, but this network will also be used as a testbed to evaluate the protocols designed by our group. We hope that this experience will be a good opportunity to improve the energy consumption in buildings, turning these into sustainable environments. After the preliminary data, we can extend and clone this network prototype to other rooms of the Institute and to other buildings on the campus. Acknowledgments This work was supported by the Spanish MEC and MICINN, as well as European Commission FEDER funds, under Grants CSD2006-00046, TIN2009-14475-C04. It was also partly supported by Regional Council under Grant PBI08-0273-7562. [1] Intelligent Building Group, http://www.ibgroup.org.uk [2] The Albacete Research Institute of Informatics, http://ww.i3a.uclm.es [3] R. Fuentes, M. Guijarro and G. Pajares, A Multi-agent System Architecture for Sensor Networks, Sensor s 2009. [4] Regional Energy Agency, Castilla-La Mancha, http://www.agecam.es [5] Product Info, http://www.maxfor.co.kr/eng/en_sub5_1_1.html [6] P. Díaz, T. Olivares and L. Orozco-Barbosa, ATON, A battery-less power supply with dynamic duty cycle for wireless sensor networks, In proceedings of Infocom 2009 [7] A. M. Ortiz, T. Olivares, F. Royo, P. Díaz, and L. Orozco-Barbosa, A cross-layer integration prototype for wireless sensor networks, In proceedings of Sigcomm 2009. [8] Proyecto Motelab, http://motelab.eecs.hardward.edu [9] Proyecto Kansei Testbed http://cqast.cse.haio.edu/kansei [10] Proyecto CitySense http://www.citysense.net/ [11] T. Olivares, P.J. Tirado, F. Royo, J.C. Castillo and L. Orozoco-Barbosa, IntellBuilding: A wireless sensor network for intelligent buildings, In proceedings of EWSN 2007. [12] T. Olivares, L. Orozoco-Barbosa, V. López y P. Pedrón, WISEVINE: Wireless Sensor Networks applied to Vineyards, In proceedings of the ACM REALWSN’06.
