Design of integrated control system for indoor environment*

Transcription

1 Design of integrated control system for indoor environment* Jie ZHAO Hui XIAO Qi KANG Yong YAN Lei JIANG College of Electronics and Information Engineering, Tongji University Shanghai , China ABSTRACT An integrated control system (ICS) is designed for improving the quality of thermal, air, lighting and other factors of indoor environment. In order to achieve the design, pre-design research on varies factors are completed. It contains two major steps: analysis of the aspects and synthesis of them. By doing the analysis and synthesis for many types of factors that influence on the indoor environment, the main factors will be selected according to three criteria: major consequence, energy efficiency and electronic controllability. Based on the research above, the practical ICS is designed for a residential house, to indicate that the approach adopted in the pre-design research is feasible and helpful in similar types of engineering design. Keywords: indoor environment, integrated control system (ICS), pre-design research, HVAC, lighting. 1. INTRODUCTION In recent years, green building draws more and more attention from architects, engineers, contractors, as well as governments and common people. They focus on different aspects of green building, such as sustainable design, zero-energy building, operations and maintenance optimization, and many other subareas of green building. One of the significant parts for green building is the indoor environment quality (IEQ) enhancement, according to LEED standards. [1] Indoor Environment Quality mainly includes three parts: indoor air quality (IAQ), thermal quality, and lighting quality. And humidity, acoustic, psychological and aesthetic factors should also be considered in the design of indoor environment. [2] One important goal for the green building is to create a healthy, comfortable, energy-efficient and productive indoor environment. Traditionally, different technologies and control strategies are used to ensure varies aspects of indoor quality. Heating, ventilating and air conditioning (HVAC) are used to ensure air and thermal quality. Johnny K.W. Wong and Heng Li, propose a selection evaluation model to compare and evaluate different approaches of intelligent control systems for HVAC. [3] It is very useful for HVAC control system design. As to electric lights and daylight control, there are also several control systems to ensure the lighting quality. Hui Xiao, Qi Kang, Jie Zhao and Yun-shi Xiao present an active green lighting model [4] for control and optimization of building luminous environment. The research targets in lighting aspects of indoor environment from the energy and comfort point of view. There are few researches focusing on the integrated control for both HVAC and lighting of the indoor environment. On the other hand, there are some researches focusing on some untraditional factors of indoor environment. Jørn Toftum, from Technical University of Denmark, compares the central automatic control mode and distributed occupant control mode for indoor environment. The author considers occupants perception as a very important factor. [5] This is not a common concern in the field of indoor environment, which inspires the authors of the paper that it is necessary to adopt a research method that considering factors from varies perspectives that contributes to the indoor environment before design a control system for indoor environment. The benefit to perform the research is that it can ensure control system designers to think of as many factors as possible before design, and then by certain approach defined in the research, they can find the major factors and rule out minor ones to simplify the system. In this paper, first of all, varies factors of indoor environment are analyzed and synthesized in the pre-design research, so as to clarify all the information needed in the integrated control system (ICS); secondly, in the design process, the ICS is *Supported by National Science Foundation of China (NSFC: ), Science and Technology Commission of Shanghai Municipality (STCSM: 08DZ , 09DZ , 09DZ ), and Program for Young Excellent Talents in Tongji University (2009KJ028)

2 designed and realized based on the information acquired in the pre-design research; and then, the conclusion is provided to emphasize that design research is significant for not only the ICS for indoor environment, but also for the similar engineering design. 2. PRE-DESIGN RESEARCH 2.1 Analysis of varies aspects of indoor environment Several factors affect the overall indoor environment, including thermal, humidity, air, light, acoustics, psychology, aesthetics, and so on. The factors will be analyzed separately in order to determine the controllability objects that can be used in the integrated control system. And other factors that not suitable for ICS will be designed separately, which are not the concern of this paper. The Objectives Factors Methods analysis pattern is adopted in the analysis process. In this pattern, the objectives are stated firstly; and the factors that influence the objectives are provided; and then practical methods or/and executives that can affect the factors will be listed, so as to provide solid and realistic reference for the following control system design. The analysis flow charts of several factors are shown below. change these factors are shown in Figure Indoor air quality (IAQ): Indoor air quality (IAQ) is affected by microbial contaminants (mold, bacteria), gases (including carbon monoxide, radon, and volatile organic compounds), particulates, or any mass or energy stressor that can induce adverse health conditions. [7] The ASHRAE defined the term of acceptable indoor air quality in the document of Ventilation for Acceptable Indoor Air Quality (ASHRAE ) [8], to guarantee the acceptable indoor air. Figure 2 shows the methods to achieve the goal. Fig. 2 Analysis of air aspects Lighting quality: Luminous environment quality can be divided into two parts: objective standards and subjective evaluations. Objective standards should ensure the proper light for work, study, safety and other required situation in the building. On the other hand, subjective evaluations are related to diverse factors, such as personal preference, emotion, psychological factors and so on. Both of the objective and subjective goals towards lighting come from daylight and electric lights. Figure 3 shows the Objectives Factors Methods pattern for luminous environment. Fig. 1 Analysis of thermal aspects Thermal quality: According to the definition of ASHRAE [6], Thermal comfort is affected by heat conduction, convection, radiation, and evaporative heat loss. And subjective factors like health, psychology, sociology and situational factors also affect thermal comfort in the building. The methods to Other factors: There are also some other factors should be considered to enhance the indoor environment quality, such as humidity, acoustics, aesthetics, and psychological aspects. We can show the pattern in Figure 4.

3 However, it is not indicate that other factors that appear only once are not important. For example, phase change material (PCM) [9] has excellent thermal characteristics, which can be used as one type of coating to achieve heat storage and release in different time periods by using simple ventilation devices. Besides PCM, daylighting is also significant for indoor environment. Not only because of its natural, clean, healthy and comfortable characteristics, but it is also the best way to save energy cost by electrical lighting. Fig. 3 Analysis of light aspects Fig. 4 Analysis of other aspects 2.2 Synthesis of varies aspects of indoor environment On the basis of the analysis above, it is safe to determine the main factors that should be controlled by the ICS, which are selected based on the following criteria Major consequence: The purpose of the ICS is to create a comfortable, healthy, energy-efficient and productive indoor environment. As a result, the factors should be selected to control considering the actual effects or major consequences of the methods shown on the figures above. We can see that Air conditioner, Ventilation, Lighting, Windows, Emotions, and Residential Appliance affect more than three factors among all the factors related to the indoor environment. So it is necessary to put these methods into the ICS Energy efficiency: It is well known that HVAC, electrical lighting, and residential appliance cover most parts of the electric energy when building is under operation. According to the sources of US Department of Energy, the electricity cost by HVAC, lighting and residential appliances (refrigeration, computers, cooking, and electronics) take up 31%, 24% and 17% of the total electricity consumption of commercial buildings. [10] Hence, it is reasonable to make HVAC, electrical lighting and residential appliance as the main factors of the ICS for indoor environment. Besides, from the energy perspective, the traditional HVAC system should be re-designed as energy-efficient type, which complies with the principles of green building. In this paper, the solar system (SS) is combined in the ICS for indoor environment. Although it has little influence on the indoor environment directly, it can save energy for HVAC system, as well as providing hot water and generating electricity for the building by using solar power. It is worthwhile to design a combined system for HVAC and solar system. However, as to the solar system, only the parts that related to HVAC will be stated and other parts of the system are beyond the scope of the paper Electronic controllability: The ICS is based on computer control technology, which can automatically change the indoor environment in real time according to feedback signals and certain control algorithm. Its limitation is that all the actuators in the control system should be electronic controllability, which means many important factors related to indoor environment cannot be controlled in the ICS, such as interior design and human emotions. Some factors, which cannot be controlled electronically in the past, are able to control and combined in certain type of control system, for instance, blinds or windows with motors for daylighting and ventilation, human occupation sensors, residential appliance

4 with the idea of intelligent home [11], and so on Summary of aspects: Considering all the three perspectives that limit and / or select the factors, it is concluded that the following aspects should be considered in the ICS: air conditioner, ventilation, lighting, daylighting, appliance, PCM and SS, shown in Figure 5. As a matter of fact, the actual ICS will realize all these aspects or parts of them, according to the local situations, costs and many other limitations when applying to engineering. bedroom, one living room, one restroom, one kitchen and front and back hallway. The floor plan of the house is shown in Figure Function description On the basis of the research for varies factors that affect indoor environment, the practical system architecture can be achieved. Five out of seven aspects to influence the indoor environment are chosen to apply in the given house, which are air conditioner, ventilation, lighting, PCM and SS. Daylighting and residential appliance are not included in this design, given the limitation of cooperation with architects, short of time and invest. The ICS with complete factors will be considered when the condition permits. However, lack of two methods will not change the system function performance significantly. In the design of HVAC, the exhausted heat from the heat pump is used to as an assistant heat source or exclusively heat water if solar radiation is not enough in winter or raining days. For the ventilation side, the needed outdoor air can be delivered based on the feedback from CO 2 sensors located in the rooms, and can be treated after heat exchange with indoor exhaust air. Fig.5 Synthesis of different aspects 3. ICS DESIGN 3.1 Background Fig. 6 floor plan of the house for ICS Besides, the PCM wall coating is painted on the wall as well as under the floor. It acts to level the heating and cooling loads and reduce the peak loads significantly. Meanwhile, it allows the use of cool air in the night to discharge the stored heat energy. The photovoltaic (PV) system is installed in the house. The electricity generation of PV system is irrelevant to the topic discussed in the paper, however, much of solar energy lost as heat, which otherwise can contribute to the quality of indoor environment. Waste heat produced by PV is released in summer and collected to heat floor panel in winter, which is called a PV/T (photovoltaic/thermal) system. The collected heat from PV/T is used with PCM floor channels to provide hot air to bedroom and maintain a relative high temperature in winter night. The complete thermal and air circling process in summer and winter are shown in Figure 7 and Figure 8, respectively. In summer, heat stored in PCM released at night, cooling transferred to bedroom space in day. While in winter, heat from SS stored in PCM in the day time, heat transferred to bedroom space at night. The ICS is designed for a typical residential house. The foot print, air conditioning area and maximum height of the house are 74.0 m2, 43.9m2, and 4.970m, respectively. It contains one

5 PLC (Programmable logic controller) module reads temperature sensors which are installed within the hot water loop and PCM module. Another PLC module is used to read CO2 / Temperature / Humidity sensors which are installed in living room and bedroom. A relay module is used to driver low power loads such as ventilation fans and airflow valve. The PLC will send control command to air-conditioner controller by Modbus protocol [12]. The control command will switch work modes of air-conditioner. Fig.7 Thermal and air flow in summer Fig.8 Thermal and air flow in winter 3.3 System architecture According to the function description above, the system architecture is given, shown in Figure 9. There are three major parts of the ICS: HVAC, PCM and SS integrated control subsystem, smart lighting control subsystem, and Human machine interface (HMI) Design of smart lighting control subsystem (SLCSS): We use EIB/KNX system for electrical lighting control. [13, 14] It is a widely-applied lighting control system for home. The key part of the design is to connect the SLCSS to other parts of the ICS, which complies with Modbus protocol. The work is done by programming in certain controller to translate EIB/KNX to Modbus. Then it can be used as gateway and the overall ICS is under the Modbus protocol Design of human machine interface (HMI): Human-machine interface (HMI) is the main user-interface of ICS. HMI can accept multiple operation actions from HPS-ICSS and SLCSS. Users can browse information and set system parameters through HMI touch screen, mobile phone with Wi-Fi and desktop computers with internet connection. 3.4 Design results and discussion The design has been realized in the given residential house mentioned in Section 3.1. The following work is to compare the ICS with other separate indoor environment systems from different points of view. It is significant to validate the ICS, so as to further prove the pre-design research is essential and helpful for control system designs. 4. CONCLUSION Fig. 9 ICS system architecture Design of HVAC, PCM and SS integrated control subsystem (HPS-ICSS): A PLC works as the core part. Certain The indoor environment is so significant that plenty of methods and factors have impacts on it. It is crucial to design an integrated control system to ensure the healthy, comfortable, energy-efficient and productive indoor environment conveniently. Before making design, by doing research on varies aspects of the indoor environment, we can determine the major factors and minor ones based on three criteria: major consequence, energy-efficiency, and electronic controllability. In the following steps, the design process will begin. Some factors may be not used in the actual design because of the

6 practical concerns, but the overall ICS for indoor environment is feasible. Additionally, the pre-design research - design pattern may also be applied in other types of engineering design, which content many factors that may affect the outcome and / or needs interdisciplinary cooperation. 5. REFERENCE [1] Lee YS, Guerin DA. Indoor environmental quality differences between office types in LEED-certified buildings in the US. Building and Environment, Vol. 45, No , pp [2] Yu Jie. Study of residence interior environmental design from the angle of aesthetics & ecology. Chongqing University, house embedded system. Intelligent Control and Automation Hangzhou: WCICA 2004, [12] Modbus Organization, Inc. Modbus Technical Resources. USA: [13] Wolfgang Kastnera, Georg Neugschwandtnera and Martin Kögler. An open approach to EIB/KNX software development. A Proceedings Volume from the 6 th IFAC International Conference, Puebla, Mexico [14] KNX Association cvba. KNX Association. Belgium: [3] Johnny K.W. Wong, Heng Li. Construction, application and validation of selection evaluation model (SEM) for intelligent HVAC control system. Automation in Construction, Vol. 19, No , pp [4] Hui Xiao, Qi Kang, Jie Zhao, Yun-shi Xiao. A dynamic sky recognition method for use in energy efficient lighting design based on CIE standard general skies. Building and Environment, Vol, 45 No. 5, 2009, pp [5] Jørn Toftum. Central automatic control or distributed occupant control for better indoor environment quality in the future. Building and Environment, Vol, 45 No. 1, 2010, pp [6] American Society of Heating, Refrigerating and Air-Conditioning Engineers. USA: [7] Wikipedia. Indoor air quality. USA: [8] Yaning Liu, The research of daylighting and energy consumption on office building. Tianjin University, [9] PCM Thermal Solutions, Inc. PCM Thermal Solutions. USA: [10] Pat Quinn, Damon T. Arnold. Illinois Department of Public Health Guidelines for Indoor Air Quality, USA: ualityguide_fs.htm, [11] Hui Xiao, Yunshi Xiao, Jiguang Yue, Cong Cao, Chen Ye, Lei Jiang. Swarm intelligence based design of intelligent