International Journal of Electronics, Communication & Instrumentation Engineering Research and Development (IJECIERD) ISSN 2249-684X Vol. 3, Issue 4, Oct 2013, 65-72 ÂŠ TJPRC Pvt. Ltd.
ENERGY EFFICIENT BUILDING AUTOMATION SYSTEMS USING PROTOCOLS AND CONTROL METHODS S. P. RASAL Mudhoji College, Phaltan, Maharashtra, India
ABSTRACT In recent years, due to the energy crises, the recognition of energy sources is limited and there is the tendency to have cleaner and comfortable environment leading to development in using energy as optimally as possible. The key driver of the building automation market is the promise of increased user comfort at reduced operation cost. Building Automation Systems (BAS) provide automatic control of the conditions of indoor environments. In the past few years, many researchers have been done on application, structure and also efficiency of different methods to achieve saving more energy. However, selecting technologies and using them effectively is a true challenge. The initial cost and maintenance of the control system is the main criteria for selecting a control system from the point of view of customer or building owner. In this paper, lighting control systems, security control and HVAC control systems using different protocols and methods as a part of building automation are studied along with their advantages and disadvantages. The paper gives concluding remarks on the most commonly used protocols and control methods for building automation.
KEYWORDS: BAS (Building Automation System), HVAC (Heating, Ventilating and Air-Conditioning), BACnet (Building Automation Control Network), LON (Local Operating Network)
INTRODUCTION OF PROTOCOLS USED FOR BAS In the broadest sense, Building automation systems are concerned with improving interaction with and between devices typically found in an indoor habitat. As such, they provide a topic with many facets and range from small networks with only a handful of devices to very large installations with thousands of devices. A BAS is mainly consists of subsystems like heating, ventilating and air-conditioning system (HVAC), lighting control, automatic fire alarm system and security system . The tasks of these subsystems are helping to understand and realize the situation of building performance, measuring building energy consumption, optimizing system running strategy and improving system management . Carlson (1991) reported that a BAS is more effective and efficient control tool to be used for building . Automatic control of indoor parameters is provided by Building automation systems (BAS) . According to him, the core and root of BAS is the automation of heating, ventilation and air-conditioning systems in large functional buildings. The primary goals of using BAS are saving energy and decreasing the cost and make all the controls automatic. Building Energy Management Systems (BEMS) in building sector is becoming a popular term now a days. According to Nikolaou et al. (2002), BEMS refers to a computerized system that tries to control energy consumption of every operation in a building . These operations may consist of heating, ventilation, lighting and indoor climate which may be controlled dependently or not based on the level of complication. Nevertheless, reaching to the optimum
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operation leads to count interrelation between the different parameters. The recent technologies help in satisfying the increase for comfort living in environment by making it automatic. Many researchers are working on the protocols and the control systems for building automation. According to Wong et al. (2005), these researches have focused on the advanced development of system integration, network protocol and building subsystem services, which include HVAC system, lighting system, fire protection system, life system, security system and communication system. They mainly focused on energy saving and performance adjustment based on occupancy and environment considering the occupantâ€™s comfort. The main part of each Intelligent Building (Harrison et al., 1998; Kroner, 1997; Wigginton and Harris, 2002; Wong et al., 2005) is a sophisticated BAS (Wong and So, 1997) . The control method techniques used for building automation are mainly classified into the three categories: conventional methods (Classical methods, Digital methods, and Fuzzy methods), and computational intelligence techniques, agent-based intelligent control systems (Dounis and Caraiscos, 2009). The expansion of BAS includes information from all aspects of Building Systems, working toward the intelligent Buildingâ€™s goal . Further, supervisory control and data acquisition (SCADA) systems for buildings, referred to as central control and monitoring systems (CCMS), were introduced. BACnet (Building Automation Control network) and LON (Local Operating Network) are two basic protocols used in BAS. BACnet was designed specifically for building automation and control applications while LON was designed to be a general purpose control network solution or LonWorks is more predominant in the application-specific controllers. However, the highest growth rate is actually witnessed among standard IT communication technologies such as TCP/IP and Web services. Comparison of these two protocols gives a basic idea of the merits and demerits of each. The first main idea explaining BACnet's superiority is that BACnet was designed specifically for HVAC control and BAS. Uniquely, BACnet is applicable to every kind of building system: HVAC, Security, Access Control, Fire, Maintenance, Lighting etc. This is an important distinction from LonWorks, which was not designed for complex system-level devices, nor was it designed specifically to meet the needs of the HVAC/ BAS industry. The consequence is that some of the functions intimately associated with building controls, and central to BACnet, such as time-of-day scheduling, alarm generation, and control prioritization, are simply not present in LON. Moreover, BACnet is designed to be scalable, i.e., it can be applied to very small or very large systems with equal effect. LON, as it exists today, is most suitable for systems with a small number of nodes. Other points of comparison are these. BACnet is an American National Standard, LON is proprietary. Figure 1 shows the BACnet protocol.
Figure 1: BACnet Devices can all Share a Common LAN Selected from the Four Approved BACnet Choices Because of the way BACnet messages are packaged, other types of computers, for example office PCs and servers, can coexist on the same LAN without interference. Another protocol which is usually used for building automation with BACnet is ZigBee protocol. Zigbee offers a global standard for interoperable products enabling the
Energy Efficient Building Automation Systems Using Protocols and Control Methods
secure and reliable monitoring and control of commercial building systems. It is the only BACnetÂŽ approved wireless mesh network standard for commercial buildings. ZigBee is the only standards-based wireless protocol technology that addresses the unique needs of remote monitoring and control and sensor network applications. The ZigBee wireless standard enables broad based deployment of wireless networks with low cost, low power solutions providing the ability for devices to run for years on inexpensive batteries in a typical monitoring application. ZigBee chips can be embedded in devices such as controllers, switches, and sensors for light, heat, or moisture. The devices can be cheap, but the savings for commercial facilities are in the avoided cabling cost. With no wiring required, peel-and-stick devices like these can be added anywhere, and moved easily. Even greater is the cost savings associated with more efficient control of a building's HVAC and lighting systems, an improvement that often requires the addition of many controllers and sensors. As per application and userâ€™s demands, Building automation also uses S-Bus, C-Bus and oBIXS-Bus protocols. S-Bus is a protocol based on RS485 connection Topology for intelligent buildings. S-bus is the developed protocol used 64 bits to be an Asian and African Standard protocol that administered by the smart-group Association. C-Bus is a proprietary communications protocol for home and building automation that can handle cable lengths up to 1000 meter using Cat-5 cable. C-Bus is used in the control of domotics, or home automation systems, as well as commercial building lighting control systems. The C-Bus system is available in a wired version and a wireless version, with a gateway available to allow messages to be sent between wired and wireless networks. oBIX (for Open Building Information Exchange) is a standard for RESTful Web Services-based interfaces to building control systems. oBIX provides a publicly available web services interface specification that can be used to obtain data in a simple and secure manner from HVAC, access control, utilities, and other building automation systems, and to provide data exchange between facility systems and enterprise applications. Further, the protocols and control methods used for illumination control, heating, ventilating and airconditioning (HVAC) control, security system are discussed.
HVAC SYSTEMS HVAC systems are active and more power consumed subsystems in BAS. Due to the great impact of HVACs systems on power and energy consumption, knowing the structure and operation of HVAC systems is becoming important. Energy efficiency and indoor climate conditions are most important goals of designing HVAC systems. Almost 50% of the total used energy in buildings is consumed by HVAC systems. So, the selection of control method and protocols is very important in case of HVAC. HVAC control system has to control four main parameters variables: temperature, humidity, pressure and ventilation. The HVAC system includes equipment such as chillers, boiler, hot water generator, heat exchangers, pumps etc and their controls located in the main mechanical room. The other types of control methods used for HVAC are: Direct acting systems, Electric/Electronics systems, Pneumatic systems, Microprocessors systems etc. HVAC control system, from the simplest room thermostat to the most complicated computerized control, has four basic elements: sensor, controller, controlled device and source of energy. Basically there are two types of controls viz. open loop control and closed loop control. Open loop control is a system with no feedback i.e. there is no way to monitor if the control system is working effectively. Closed loop control considers the feedback from the output to take the further action. So, closed loop control is also called feedback control. The simplest control in HVAC system is
S. P. Rasal
cycling or on/off control to meet part load conditions. If building only needs half the energy that the system is designed to deliver, the system runs for about ten minutes, turns off for ten minutes, and then cycles on again. As the building load increases, the system runs longer and its off period is shorter. One problem faced by this type of control is shortcycling which keeps the system operating at the inefficient condition and wears the component quickly. A furnace or air-conditioner takes several minutes before reaching "steady-state" performance. Recent technologies for control methods include the use of microcontroller, fuzzy logic, internet based protocols, web based protocols and GSM based protocols. It was proved that a system can be controlled by three different units (web based control, remote control hand device and key pad control mounted on AC). All hardware system of Ac is controlled by a PIC microcontroller using PCI bus . The sensors used for HVAC are mainly analog sensors: Temperature sensor (Bi-Metallic strip, sealed bellows, RTD, Thermocouples, Thermisters etc.), Pressure sensors (Variable resistance, capacitor) and Flow sensors.
SECURITY SYSTEM During the past few years, some people have thought that protocols had been â€œdone,â€? and that we should turn to new research topics. These people have been repeatedly proved wrong by the emergence of new protocol applications, with a new crop of errors and attacks to be explored. So, protocols or control methods for security systems are still in innovation. A typical security system consists of a number of principals such as people, companies, computers, and magnetic card readers, which communicate using a variety of channels including phones, email, radio, infrared, and by carrying data on physical devices such as bank cards and transport tickets. The security protocols are the rules that govern these communications. There are number of control methods and protocols used for security systems. Passwords are still the foundation on which much of computer security rests, as they are the main mechanism used to authenticate human users to computer systems. However, password can be cracked. So, instead of password thumb impression or brain scanning is used for giving the entry in restricted areas. In recent years, occupancy sensors are used to detect the motion and smoke detectors are used for fire alarm system. The integration of security subsystems significantly tightens security requirements on the protocol of a networked control system of BAS. The security of BAS, LonTalk and other protocols is the major issue of the security system used for building automation. It is difficult to design effective security protocols. They suffer from a number of potential problems, including middleperson attacks, modification attacks, reflection attacks, and replay attacks.
ILLUMINATION / LIGHT CONTROL SYSTEM Adding simple local sensor and relay based lighting control is the easiest way to reduce lighting energy consumption. It has been shown that adding simple occupancy control to an existing lighting system can save 40% on average in lighting energy. There are two basic sensor technologies, passive infrared (PIR) and ultrasonic. PIR sensors track the movement of warm objects in a room and require line of sight for operation. Ultrasonic sensors create a high frequency standing acoustic wave and measure changes in the wave (human movement) to detect occupancy and can operate around corners and office partitions. In a daylighting control system, photo sensors read the light level in the space and switch off or dim perimeter lights by circuit or fixture in order to harvest available daylight. Occupancy and daylight harvesting can be taken to the next level by connecting the sensors to a network based lighting control system.
Energy Efficient Building Automation Systems Using Protocols and Control Methods
On average, lighting accounts for about 25 percent of a buildingâ€™s energy use. A major portion of this expense is unnecessary. Technologies developed during the past 10 years can help to cut lighting costs by 30 to 60 percent while enhancing lighting quality and reducing environmental impact. Use of day light helps in saving the energy. DALI (Digital Addressable Lighting Interface) is the New Digital Standard or protocol specially designed for lighting control system. The (DALI) is a bi-directional, digital protocol developed by lighting manufacturers to control light source levels. The new protocol was initially applied to the control of linear and compact fluorescent lamps, followed by additional light sources, such as HID, LEDand incandescent lamps. Because DALI gives each lighting fixture a unique IP address, it is an ideal way to control lighting costs in new construction, and applications with shifting occupancies or round-the-clock operations, such as office buildings and hospitals and individual components of a lighting system. DALI provides simplified communication and installation, yet maximum control and flexibility. Wiring is simpler. Installation costs are lower. Each ballast can be individually controlled (addressed) as well as belong to any or all of 16 different groups. Maintenance costs are reduced through central monitoring of ballast and lamp status. Energy costs are lowered through daylight harvesting and standard controls such as occupancy sensors. Moreover, most importantly, the open standard allows interchangeability of DALI ballasts and controls from different manufacturers. Digital Signal Interface (DSI) is a protocol for the controlling of lighting in buildings (initially electrical ballasts). DSI was one of the first proprietary protocols to digitally control electrical ballasts. Like 1-10v it is very simple and easy to implement. As the predecessor to DALI, individual ballasts are not uniquely addressable like DALI. Each run of lights is controlled as a single entity. DSI has the same advantages as 1-10v, simplicity of deployment and troubleshooting. It also has similar disadvantages of large DSI installations requiring complex and expensive runs of multi-core cable.
COMPARISON OF PROTOCOLS AND CONTROL METHODS USED FOR BAS BACnet (Building Automation Control network) and LON (Local Operating Network) are most popular protocols used for BAS. BACnet was developed by a committee formed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). LonWorks was designed by Echelon Corporation for use with virtually all types of control systems. BACnet was designed specifically for HVAC control and BAS. This is an important distinction from LonWorks, which was not designed for complex system-level devices, nor was it designed specifically to meet the needs of the HVAC/ BAS industry. BACnet developed specifically for Building Services, defines how all the elements of the Building Management System work together. Uniquely, BACnet is applicable to every kind of building system: HVAC, Security, Access Control, Fire, Maintenance, Lighting etc. It offers compatibility with devices made by different vendors as well as with future generations of systems. Another important benefit of BACnet is that it supports a wider range of communication transports than LonWorks. BACnet can communicate with different LAN technology for transporting BACnet application messages via BACnet routers, providing significant flexibility in choosing the best fit for each situation. Its high-speed capabilities provide room for future growth, while its flexibility in networking options allows it to be used in even small zone controller subnets. Ethernet capability allows connection directly to wide area networks that link remote building sites as well as multiple local area networks.
S. P. Rasal
The comparative analysis of BACnet and LON is given in table 1 Table 1: Comparison of BACnet and LONWorks Category Cost Complexity Interoperability Diagnostic and Development Tool Availability
BACnet Higher cost system Needless Complexity No Device Interoperability Limited Diagnostic tools available
LONWorks Lower cost system Well defined structure Device Level Interoperability Tools available from multiple sources
BACnet can use wired or wireless networks. Zigbee is the only BACnet® approved wireless mesh network standard for commercial buildings. There are merits and demerits of wired and wireless transmission media. The comparison of these two is given in table 2 Table 2: Features of Wired and Wireless Transmission Media Features Range Installation effort and flexibility Data Volume Reliability Cost
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The table 2 shows a collective assessment of major criteria relevant for the market indicates that neither of the two transmission media, Wired or Wireless, comes out alone on top in a building-automation scenario. For an optimal solution, it takes both; each implemented where it is better than the other.
CONCLUSIONS In this paper, a review of control methods and protocols for energy efficiency and comfort in buildings is presented. At the beginning of this paper, BACnet and LonTalk protocols are discussed with their merits and demerits. The comparison of two main protocols says that the BACnet is more superior than LonTalk protocol. BACnet is a unique object-oriented model for data representation makes it the most advanced protocol of its kind, and provides maximum flexibility than LonTalk. Then protocols and control methods for HVAC system, Security system and illumination or light control system are investigated along with the sensors used for each system. According to investigation of control systems, the intelligent control systems are more developed for improving the energy efficiency in buildings. While control systems can indeed be complex, they are now an essential component of modern buildings and will continue to evolve. Designers and owners should make every effort to understand the technology so they can operate their buildings at their best efficiency. Identifying the appropriate technologies for particular building types and occupancies will reduce overall energy use. A successful building automation system design implements effective strategies to optimize these new control technologies. One key challenge in BAS is that large areas need to be covered especially in high-rise buildings or larger building complexes. Another challenge is that the domain is highly cost sensitive when compared with industrial automation. Also, systems have to be long-lived (at least in comparison with the IT world). They are required to be “future proof,” which favors proven, technologically conservative approaches. Hence, the domain is very slow to accept and adopt new technological developments.
Energy Efficient Building Automation Systems Using Protocols and Control Methods
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