Abstract: This paper introduces relevant domestic and international standards for building energy conservation, as well as the architecture and functions of Advantech's BEMS building energy management system, and provides relevant application instructions. Advantech's BEMS building energy management system can be applied to the daily energy management of large buildings or factories; furthermore, the BEMS communication interface can transmit data to national, provincial, and municipal energy consumption data centers, participating in the construction of the national building energy consumption statistics platform, indicating immeasurable future market potential.
Keywords: BEMS, building energy conservation, energy consumption statistics, energy consumption monitoring, sub-item energy consumption, demand control
1 Introduction
The proportion of building energy consumption in total energy consumption reflects a country's or region's economic development level and quality of life. Currently, building energy consumption in major developed countries accounts for about one-third of total social energy consumption. Although my country's building energy consumption ratio is lower than that of developed countries, due to the rapid development of the construction market, the proportion of building energy consumption in total energy consumption is increasing year by year. Data shows that in the next few years, the number of large public buildings such as office buildings, apartments, hotels, and convention centers will increase significantly, with approximately 1 billion square meters of new large public buildings expected in my country by 2020. Since over 90% of my country's large public buildings are typical high-energy consumers (electricity), adopting various methods to achieve building energy conservation is an inevitable choice given the increasingly tight energy demand. How to conduct quantitative management and effectiveness evaluation of building energy consumption, and reduce the energy consumed during building operation, including air conditioning, lighting, heating, elevators, and office equipment, thereby reducing operating costs, has become a primary concern for building owners.
To reduce energy consumption, it is necessary to manage energy effectively. For a modern building, without the installation of BEMS, it is difficult to understand the operation of energy-consuming equipment such as air conditioning and lighting in the building. Statistics show that 35% to 50% of energy is wasted as a result. On the other hand, there is a parameter to consider when paying for industrial and commercial electricity: contracted electricity capacity. When all energy-consuming equipment is running, it will generate strong electricity demand. Even if the electricity load exceeds the contracted capacity for only 15 to 20 minutes in a month, the basic electricity fee for the whole month is still charged based on the maximum load. Statistics show that these additional costs usually account for 25% of the company's electricity bill[2].
Building Energy Management System (BEMS) is a centralized monitoring, management, and decentralized control system for the energy usage of power distribution, lighting, elevators, air conditioning, heating, water supply, and drainage within a building or building complex. It is a collective term for the hardware and software systems that enable online monitoring and dynamic analysis of building energy consumption. It consists of various metering devices, data acquisition units, and energy consumption data management software. BEMS achieves the following effects through real-time online monitoring and analysis:
1) Monitor equipment energy consumption to improve overall management level;
2) Identify equipment that is operating inefficiently;
3) Identify abnormal energy consumption;
4) Reduce peak power consumption levels.
The ultimate goal of BEMS is to reduce energy consumption and save costs.
2 Standards
When designing BEMS products and energy-saving project technical solutions, we referenced relevant international and domestic standards for energy management systems, especially in the BEMS data remote transmission interface, which complies with the relevant national standards and specifications.
2.1 International Standards
1) IEEE Std 739-1995, "IEEE Recommended Practice for Energy Management in Industrial and Commercial Facilities"
Issued by the Institute of Electrical and Electronics Engineers (IEEE), this document provides guidance on monitoring and managing energy consumption in various systems and equipment within industrial and commercial enterprises. It outlines how to conduct energy audits to examine for energy waste in individual devices. Specifically, it provides methods for assessing and improving energy efficiency for systems such as lighting, air conditioning, motors, and air compressors.
2) IPMVP International Energy Efficiency Measurement and Certification Procedure
Issued by the International Committee on Measurement and Certification of Energy Efficiency, the MVP provides an overview of the best available technologies for verifying the effectiveness of energy efficiency, water conservation, and renewable energy projects.
2.2 Domestic Standards
To prepare for the establishment of systems such as energy consumption statistics, energy audits, energy efficiency disclosure, energy consumption quotas, and surcharges for exceeding quotas, and to promote improved energy-saving operation and management in office buildings and large public buildings, the Ministry of Housing and Urban-Rural Development officially promulgated a set of technical guidelines for energy consumption monitoring systems in national government office buildings and large public buildings in June 2008. The guidelines consist of five parts (hereinafter collectively referred to as the "Guidelines"): Technical Guidelines for Sub-item Energy Consumption Data Acquisition; Technical Guidelines for Sub-item Energy Consumption Data Transmission; Technical Guidelines for Building Sub-item Metering Design and Installation; Technical Guidelines for Data Center Construction and Maintenance; and System Construction, Acceptance, and Operation Management Specifications.
The product design primarily referenced the "Technical Guidelines for Sub-item Energy Consumption Data Acquisition," the "Technical Guidelines for Sub-item Energy Consumption Data Transmission," and the "Technical Guidelines for Building Sub-item Metering Design and Installation." The "Technical Guidelines for Sub-item Energy Consumption Data Acquisition" specifies unified energy consumption data classification, sub-item methods, and coding rules, providing support for real-time acquisition, accurate transmission, scientific processing, and effective storage of sub-item energy consumption data. The "Technical Guidelines for Sub-item Energy Consumption Data Transmission" specifies the energy consumption data transmission process and format between energy consumption metering devices, data acquisition units, and data centers at various levels in the energy consumption monitoring system. The "Technical Guidelines for Building Sub-item Metering Design and Installation" standardizes the methods for building sub-item metering and heating/cooling metering.
Based on the building's function and energy consumption characteristics, the Guidelines classify government office buildings and large public buildings into eight categories: 1) Office buildings; 2) Shopping mall buildings; 3) Hotel and restaurant buildings; 4) Cultural and educational buildings; 5) Medical and health buildings; 6) Sports buildings; 7) Comprehensive buildings; and 8) Other buildings (referring to buildings other than the above seven types).
For each type of building, the data indicators to be collected are divided into two main categories: basic building information data and energy consumption data. Basic building information data includes parameters characterizing the building's scale, function, and energy consumption characteristics, such as building name, address, construction year, number of floors, function, total floor area, air-conditioned area, heating area, and type of air conditioning system. Energy consumption data includes hourly, daily, monthly, and yearly data for each category and sub-item of energy consumption, as well as various related energy consumption indicators. The specific content of each category, sub-item of energy consumption, and related energy consumption indicators is shown in the table below.
The guidelines stipulate that energy consumption data charts should intuitively reflect and compare the values, trends, and distribution of various collected and statistical data, and provide suggestions for various data chart display methods, such as pie charts, bar charts, line charts, area charts, distribution charts, mixed charts, Gantt charts, dashboards, or animations.
To ensure that energy consumption data can be identified and processed by computers or humans, to ensure that the data is effectively managed and supports efficient query services, and to achieve consistency in data organization, storage and exchange, the "Guidelines" have formulated coding rules for remote transmission of energy consumption data and detailed the code structure.
3 Advantech Building Energy Management System
Advantech's Building Energy Management System (BEMS) is designed and developed based on the international and domestic standards described in Section 2, while also drawing on the products of major manufacturers in the market.
Advantech BEMS consists of hardware devices and software systems. The selection of meters and data acquisition units in the hardware devices can refer to the specifications in the "Guidelines," used for data acquisition, storage, and analysis of electrical equipment. The software system is developed based on WebAccess configuration software, inheriting WebAccess's advantages such as configurability and remote maintenance. It includes two subsystems: an energy consumption monitoring and management subsystem and a demand control subsystem. The energy consumption monitoring and management subsystem collects, monitors, manages, and controls various categories and items of energy consumption data in buildings, providing rich data charts and reports, as well as data statistical analysis functions, helping users to grasp energy consumption anytime, anywhere, identify energy usage anomalies, and establish energy reduction plans. The energy consumption monitoring and management subsystem is embedded in the WebAccess project nodes and monitoring nodes. Energy consumption data is collected by the WebAccess monitoring nodes, and the project nodes can be configured with energy management projects to store, statistically analyze, and provide web services for data chart display. The demand control subsystem runs on the WebAccess monitoring nodes. Through real-time acquisition and calculation of energy consumption data, it uses advanced control algorithms to limit peak electricity demand and reduce electricity costs. It is worth noting that the configurable nature of BEMS extends its application beyond the building industry. Industrial enterprises, such as steel and petrochemical companies, can also achieve energy management through flexible user configuration.
Advantech's BEMS energy management system helps users achieve the following needs:
1) Establish a real-time energy consumption data acquisition system
The real-time energy consumption data acquisition system includes various metering devices, data acquisition units, and data acquisition software. Real-time data is stored in the energy management system's energy consumption database. Managers at all levels can access the energy management system from their offices using a web browser and view all or part of the relevant energy metering information according to their permissions.
2) Establish an energy consumption data statistics and analysis system
The energy consumption data statistics and analysis function provides hourly, daily, monthly, and yearly statistical charts and text reports of energy consumption data for each category and item, as well as charts of various related energy consumption indicators. Managers at all levels can compare the energy consumption per shift, daily, and monthly, analyze loopholes and unreasonable situations in the energy use process, adjust energy allocation strategies, reduce waste in the energy use process, and achieve the goal of energy conservation and consumption reduction.
3) Establish an energy use plan
Based on current energy usage, develop an energy usage plan. Based on energy demand, formulate energy procurement, production, and supply plans to ensure purposeful production and planned use, guaranteeing stable production and rational, economical energy use, and avoiding waste.
4) Establish an energy conversion system
For the use of different types of energy, it is necessary to convert them into standard units for comparison and synthesis. An energy conversion system should be established so that different energy sources can be combined and compared.
5) Establish a demand control system
Users define load groups, loads, and contracted capacity information through configuration. The demand control system automatically predicts the demand at the next moment and unloads or restores loads according to load unloading priority, ensuring that the system demand does not exceed the peak contracted capacity and avoids penalties or power outages.
3.1 Energy Consumption Monitoring and Management Subsystem
The energy consumption monitoring and management subsystem consists of various metering devices, data acquisition units, and a management system (Web server). It helps users establish a real-time energy consumption data acquisition system, an energy consumption data statistics and analysis system, an energy usage plan, and an energy conversion system.
3.1.1 System Architecture
The following diagram shows the system architecture of the energy consumption monitoring and management subsystem. The system adopts a three-layer distributed structure.
Various metering devices are used to measure energy consumption in various categories and items, including electricity meters (single-phase, three-phase, and multi-function meters), water meters, gas meters, and heat (cold) meters. These metering devices have remote data transmission capabilities, connecting to data acquisition units via fieldbus and supporting various communication protocols (such as the MODBUS standard open protocol) for data output. The WebAccess monitoring node serves as the data acquisition unit for the energy consumption monitoring and management subsystem. The management system is located at the WebAccess engineering node, and the data acquisition unit transmits data to the management system's database via Ethernet. Users can configure the energy management project and browse energy consumption data at the WebAccess engineering node. The management system's communication interface can transmit energy consumption data to upper-level data transfer stations or provincial/ministerial-level data centers according to the "Technical Guidelines for Data Transmission of Itemized Energy Consumption in State Organs Office Buildings and Large Public Buildings."
3.1.2 Data Organization Methods
The energy consumption monitoring and management subsystem offers flexible configuration capabilities, allowing users to configure energy management projects according to their actual needs. An energy management project can contain multiple energy management groups, and each energy management group can contain multiple energy management members, or it can contain other energy management groups. Taking a building as an example, a configured energy management group represents the building's various categories and sub-items of energy consumption.
3.1.3 System Functions
1) Energy Profile
Energy management groups provide hourly, daily, monthly, and yearly energy consumption reports to help users understand their energy consumption and identify anomalies. Reports on various related energy consumption indicators, such as Energy Usage per Unit Area (EUI), provide data support for energy statistics and energy audits. Temperature and humidity reference functions help analyze the correlation between energy consumption data and environmental data.
2) Energy Ranking
The energy consumption values of the energy management group are ranked across different time periods to help identify the equipment units with the lowest and highest energy efficiency.
3) Energy Comparison
Comparison of energy consumption values of the energy management group over different time periods.
4) Average Daily Profile
A report of average energy consumption demand every 15 minutes on any given day. This helps users understand their energy consumption patterns and identify peak demand that exceeds expectations, providing a reference when signing contracts with power companies.
5) Deviation Analysis (Deviation Report)
This represents the deviation between energy consumption values at different times of any given day and the management settings. A red deviation value indicates that the actual energy consumption exceeds the planned energy usage value, suggesting an increasing trend in energy consumption.
6) Max/Min Value Analysis
Analysis of maximum/minimum energy consumption values over different time periods. This allows for analysis of the correlation between energy consumption and time for various systems and equipment.
7) Primary Energy Profile
The enterprise's energy consumption value is converted into heat (MJ), standard coal, and primary energy consumption such as crude oil and raw coal, as well as the relative CO2 release.
8) Cost Profile
Each energy management team submits daily, monthly, and yearly energy cost reports. Energy costs are calculated based on energy meter data and rate structures, aiding in energy cost management. Users can set energy cost benchmarks and budget based on deviations from actual costs, helping to reduce risks in energy procurement.
9) Cost Ranking
Rank the cost values of energy management groups across different timeframes. Help identify the equipment units with the lowest and highest energy consumption.
10) Statistical Report
Annual/monthly/daily statistical reports on categorized and itemized energy consumption data. This provides users with a clear overview of their company's energy consumption and helps them rationally allocate energy usage.
3.2 Demand Control Subsystem
The Demand Limiting (DL) subsystem reduces peak-hour electricity demand by adjusting load usage, thereby reducing additional charges and ultimately lowering long-term energy costs for businesses. In the electricity load power curve, if current electricity demand approaches peak contract capacity, measures should be taken to reduce demand, as illustrated in the diagram below.
DL groups the load. A monitoring node can have multiple load groups, but each load group must correspond to one or more contracts. Control operations for each load group are performed independently, and DL classifies the load according to six offloading levels. DL processes the following processes per minute:
1) DL reads the meter input;
2) DL predicts power demand within the demand period. When power demand exceeds the peak contract capacity setting, DL calculates the power value that needs to be adjusted, and this power value is the amount that DL needs to unload.
3) When the predicted power demand exceeds the peak contract capacity setting, DL first selects the load with an offloading level of 6 for offloading until the offloading target is reached. DL cyclically offloads the offloading equipment.
The load cannot be unloaded under the following conditions:
a) The load is locked;
b) The load is offline or in an alarm state.
c) The load is already in an unloaded state or below the unload level.
d) Load operating time is less than minimum operating time
e) The load has just been unloaded and restored by DL, but the restoration time is less than the minimum restoration time.
4) If all loads at level 6 are offloaded, DL will begin offloading loads at level 4 until the requirements are met.
5) If all loads at level 4 are offloaded, DL will begin offloading loads at level 3 until the requirements are met. This continues until loads at level 1 are offloaded.
6) If unloading all unloadable loads still cannot meet the requirements, DL will generate an alarm notification.
7) Each load attribute has a minimum unloading time. DL compares the unloading time of each load. When the requirements are met, DL can restore the load. The order of load restoration is the reverse of unloading.
The load group diagram and load detail diagram of DL in operation are shown below. Clicking on a load group will display the operating data and power curve for that load group within the demand cycle. The load detail diagram allows you to view the status of each load and control the load.
4. Application of BEMS in Building Energy Conservation
After installing a Building Energy Management System (BEMS), it's like giving a building "eyes," a "nerve system," a "brain," and "limbs." The "eyes" monitor energy consumption; the fieldbus and communication network form the "nerve system" that collects data; the "brain" identifies energy waste and anomalies; and the "limbs" execute the instructions from the "brain." However, the energy management system is only one important tool in energy conservation. In daily energy management, the energy manager primarily acts as the "brain," using BEMS to acquire data, analyze it, and make decisions to ultimately save energy and reduce costs. Energy conservation is not achieved overnight; it's a continuous, feedback-driven, and optimized process.
As mentioned earlier, different types of buildings have different energy consumption characteristics. This section will take office buildings and shopping mall buildings as examples to briefly illustrate the application of BEMS in building energy conservation.
4.1 Office Buildings
1) Understand the building overview
The office building has 13 floors. Working hours are Monday to Friday, 8:00 AM to 6:00 PM (with a 1-hour lunch break), closed on weekends and public holidays. The first floor is retail space, and floors 2-13 are all standard office floors. The total building area is 8625 m², with 7300 m² under air conditioning. A fresh air handling unit plus fan coil unit system is used. The cooling source is two rod-type chiller units, and the heat source is a central hot water unit. Each chiller unit is equipped with two chilled water pumps and two cooling water pumps. Record the rated power values of the main energy-consuming equipment in the building.
2) Building Energy Consumption Structure Analysis
The chart below, obtained from BEMS, shows the electricity consumption ratios of the office building's air conditioning system, lighting system, and office and other equipment in a certain year. The chart clearly shows that the air conditioning system accounts for a large proportion of energy consumption, thus requiring further analysis of air conditioning energy consumption.
The following chart shows the energy consumption proportions of various components within an air conditioning system. As can be seen, the chiller/hot water unit accounts for the largest proportion, reaching 54%. In addition, terminal equipment accounts for 25% of the annual electricity consumption. The water delivery system (cooling water pumps, chilled water pumps) also has a significant energy consumption proportion, reaching 18%.
3) Hourly/Daily/Monthly/Yearly Analysis of Building Energy Consumption
Hourly, daily, monthly, and yearly energy consumption charts help understand and analyze building energy consumption patterns and identify energy anomalies. The chart below shows the hourly power consumption of various devices in this office building during a typical summer day. Power consumption for each component begins to rise at 7:00 AM and begins to decline at 6:00 PM, with a slight drop around midday. Peak elevator usage occurs between 7:00 AM and 9:00 AM, coinciding with an increase in air conditioning energy consumption. During the midday break, energy consumption for air conditioning, lighting, and office equipment decreases, but not significantly. Between 8:00 PM and 10:00 PM, there is still some energy consumption for lighting and ventilation.
4) Energy-saving potential analysis
Because of the functional use of office buildings, the energy consumption of the building's lighting system and office equipment is basically stable, having little impact on the annual building energy consumption. Energy conservation in the lighting system is reflected in daily management, such as turning off lights when leaving a room and replacing light bulbs with energy-saving ones.
For the main energy-consuming system—the air conditioning system—based on its operating records, the main energy-saving measures are as follows:
a) The main unit is equipped with a relatively large capacity. Most of the time, only one main unit is running, and one chilled water pump and one cooling water pump are sufficient to meet the needs.
b) The air conditioning water system suffers from a problem of high flow rate and small temperature difference. The supply and return water temperature difference should be increased, the water flow rate reduced, and variable flow technology should be adopted.
c) The indoor temperature setting is too low, increasing energy consumption. The indoor temperature and relative humidity settings should be increased respectively.
4.2 Shopping Mall Building
1) Understand the building overview
A large shopping mall has a building area of approximately 510,000 m2, with an air-conditioned building area of approximately 380,000 m2. It uses gas boilers for heating in winter and centrifugal chillers as the cold source in summer, employing a constant air volume all-air system. There are a total of 530 air conditioning units of different models.
2) Building Energy Consumption Structure Analysis
The chart below shows the electricity consumption ratios of the shopping mall's air conditioning, lighting, and elevator systems in a certain year. It can be seen from the chart that the air conditioning and lighting systems account for a large proportion of the energy consumption.
The high energy consumption of shopping mall air conditioning systems is mainly determined by their load conditions. For example, some shopping mall buildings use glass curtain walls and other heat-permeable materials for their building envelope, resulting in a huge cooling load. Indoor lighting also has a high load due to the need for merchandise display. Furthermore, the high density of people in shopping malls means that heat load from people constitutes a significant portion of the air conditioning system's load. Therefore, the energy consumption of shopping mall air conditioning systems is relatively high.
The energy consumption ratios of various equipment in the air conditioning system are shown in the figure below. The chiller accounts for 23% of the electricity consumption, while the water system, including chilled water pumps, cooling water pumps, and cooling towers, accounts for 11.6% combined. Since the shopping mall uses an all-air conditioning system, the air conditioning unit fans operate year-round; therefore, the air conditioning unit fans account for 65.4% of the electricity consumption, representing the most significant waste and the greatest potential for energy saving.
3) Hourly/Daily/Monthly/Yearly Analysis of Building Energy Consumption
The following is a chart showing the total electricity consumption of the shopping mall in a given year.
4) Energy-saving potential analysis
For air conditioning systems, the main energy-saving strategies that can be referenced are:
a) Variable frequency control of the air conditioning unit fan
b) Make full use of the fresh air natural cooling source
c) Avoid uneven heating and cooling by controlling air pressure.
5. Summary
my country implemented the Energy Conservation Law on April 1, 2008, making energy conservation a fundamental national policy. The 11th Five-Year Plan called for "building a resource-saving and environmentally friendly society." Regarding building energy conservation, the government has introduced a series of policies. By 2020, my country's investment in energy-efficient building projects will reach at least 1.5 trillion yuan, indicating a very promising market prospect for Building Energy Efficiency Systems (BEMS).
Advantech Building Automation Division
Since its founding in 1983, Advantech has been committed to providing customers with high-quality, high-performance products and services. Advantech Automation, as Advantech's first business group, focuses on four key vertical industries: building energy conservation, machinery manufacturing, power energy, and intelligent transportation. Advantech Automation provides building energy conservation customers with advanced system products and professional, timely technical services. Specifically for the building automation market, it has independently developed the web-based iBAS building automation control system and BEMS building energy management system. The entire system is centered on web technology, utilizing BEMS's rich graphical reports and data analysis capabilities to help users understand and analyze energy consumption and make decisions. The iBAS system can then systematically load or unload electrical equipment to achieve energy savings.
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