【 Weak current College 】 intelligent building recognition of building automation systems and the development trend

With the development of the times, more and more domestic tall buildings, and the development of information technology to enable building intelligent universal development continuously. Almost all the tall buildings, such as Government Office building, hotel, comprehensive office building, according to the size of the scale and financial resources, more or less invested in building intelligent systems, in particular premises equipment automation system is almost a necessity, it is the foundation of intelligent building, target is premises equipment and energy realization of intelligent management, creating a comfortable, environmentally friendly, energy-saving of working and living environment. Building automatic control system on the premises of air-conditioning and ventilation systems, distribution systems, water supply and drainage, and heat source system, lighting system, a large number of devices to be methodical management and maintenance.

Construction equipment monitoring system by building in a variety of mechanical and electrical facility for full computer control, the use of distributed control and centralized management technology for building users with a good working environment, to building managers provide a convenient means of management, reducing the energy consumption of buildings, extend equipment life, increase productivity and reduce labor cost.

The present building automatic control system although develops to a certain degree, whether hardware or software of more advanced and reliable, but really want to achieve the intended purpose, there are a lot of work to do. The author according to years of work experience, this provides some new understanding and perspective.

1 based on building automatic control system of investment and the understanding of the effect

Since 2000, the intelligent building of the early building automation system of investment considerably decreased, from BA control detection point 2000 yuan/points, fell to less than 1000 RMB/point, is in constant decline, while real estate prices are going up, so far, the average increase for 3 times, there is high. Where you can see that the intelligent building of the beginning of the building automation system investment proportion of the total building, investment, and the average life expectancy of modern high-rises for over 100 years old, although the building automation equipment will continue to lag behind, but the entire cabling framework exists, the upgrade will be very convenient.

Intelligent building energy-saving building automation system is an important means to recognize its urgency, first of all should strengthen the advocacy building energy efficiency, make everyone aware that energy is not just about money and the environment, but rather the steady development of the sustainability of the country. Current smart building automation systems running energy-saving effect is not very satisfactory, there are many reasons, the first part of the Manager as the deviation of the understanding that the building automation system, as several people manually opened. This went into a misunderstanding that actually rely on people's manual control, impossible construction equipment of energy-saving, efficient and safe operation. Understanding must therefore be changing enhancing property team training and building on the device management can delegate the warranty expires, to improve the professional company take care of the equipment operating life, maximum play the role of the system. Otherwise due to the low level of device management enables the running costs are high, resulting in wasted investment.

Building automatic control system of energy must start from the detail, forming a habit, when it comes to energy-saving design, electrical designers usually think about selecting the right transformer, frequency converters, soft starters, to energy-saving lamp with electronic ballast, coil system with three-speed fan and electric valve, which is a building automation system design content in General. In addition, energy-saving design is also reflected in the light of the details, such as the design of the hotel rooms, energy saving switch in time the power is switched on, people leave the power cut off in order to achieve energy-saving purposes.
2 intelligent building automation system for building equipment put forward higher requirements

Intelligent building building automatic control system requires a variety of professional support, building automation and energy-saving is not just a professional thing, it requires the intelligentized, building structures, HVAC, ventilation, electric power, water supply and drainage, and other professional to join cooperation, proposals that are energy-saving potential. Lighting system for building a separate subsystem, including the public area of the public lighting (such as parking, lobby, corridor, dining room lighting, interior lighting (offices, conference rooms etc.), outdoor lighting (decorative lighting, road lighting, flood lighting), etc. Building energy consumption for lighting of buildings accounts for the entire 20%, the lighting system has such characteristics: first, in electric power transmission, to a high voltage transmission to ensure that terminal equipment operating voltage, as the load on the device, the output voltage will be increased by building automatic control system for dynamic voltage control, achieve energy-saving purposes. Second, the demand for lighting function, the time period each day is different, especially outdoor illumination sensors can be combined together, on the public area, piecewise control or direct close all, such as underground garage lighting control. Third, with the development of new lighting source, new energy-saving lamps are emerging to replace traditional heating of fluorescent lamps, energy-saving lamps, incandescent lamps, metal halide lamps and other lights switch control, the use of digital technology and computer technology to fully integrate intelligent control with soft start, control power impulse voltage and surge voltage, so that the filament from thermal shock, lamp life has been extended. Intelligent lighting system usually makes the lamp life extension of 2 ~ 4 times, not only save a lot of light and significantly reduce the workload of the replacement of lamps, effectively reducing the lighting system of running costs for the extensive use of lighting and install a difficult area has special significance. In addition, intelligent lighting system also has the potential of value in return, so that the whole system work in the most comfortable State, thus ensuring people's physical and mental health, improves work efficiency.

Air conditioning system is another subsystem, it is divided into air handling terminal equipment such as fresh air handling units, air handling units, VAV variable air volume, another part of the source system to the cold, it's power consumption in General covers the entire building of 70% or so, how to run and manage air conditioning equipment of the more important, the use of advanced building automation systems, in meeting room of the comfort level, you can save energy, extend equipment life, andYou can reduce the number of device management, are set out each analysis;

(1) fresh air system is based on the floor of the size, conveying a certain temperature, the amount of fresh air to ensure the room air quality, ventilation system of automatic control design generally determine a supply air temperature point, if you have high humidity requirements, the need to increase a humidity, air conditioning pipes such as take second control, hot summer-winter-cold water, selected a electric regulating valve. High requirements for temperature and humidity, the air conditioning of buildings in General take four pipe, cold and hot water control to be installed separately, and the installation of an electric regulating valve, to prevent freezing during the winter, the installation of the condenser antifreeze switch and fresh air electric valve, run into outdoor temperature is low, the air conditioning is not used directly off the fresh air door or hot water circulation pump start, hot water running at low flow rate.

In the air runtime, control of the target parameter as the air temperature and humidity degree, compared with the set value, the deviation value of output signal via DDC operations, control of cold (hot water) electric two-way valve to open degree. For air supply unit temperature setpoint floor control system can be combined with the size of the outdoor temperature, automatic adjustment, winter is 30 ~ 32 ° c, in summer as 18 ~ 20 ° c.

(2) for public areas (lobby, cafeteria) temperature and humidity environmental improvement is mainly through the air conditioning unit air-handling means, its flow chart than the new fan complex, increasing the return air ducts.

General-controlled configuration of equipment for hot and cold water valve, humidifying air valve, valve, air temperature, air temperature, some also install public regional temperature sensor, air through frequency can be adjusted to the target control parameters of the generic to the return air temperature, but is not necessarily appropriate, such as back to the outlet from the door closer, sampling data is inaccurate, or in the public region layout multiple temperature sensor, and averaged, the specific projects to specific analysis, comprehensive consideration. For control of it than the new blower air temperature control is more complex, its own characteristic is dead, the reaction is slow, if you take regular PID control is bound to cause control valve frequent switching, temperature of the volatility. Therefore take unconventional strategies, such as the dead zone, when a target parameter entry and set the value of the accepted deviation range DT1 (General 0.5 degrees), cold (hot) water valve remains unchanged. Variable PID control mode, that is, when the target parameters and set values for the control of large, strong, when the objective parameters and set values for hour, some control of the weak. You can take under temperature deviation and increase or decrease speed of fuzzy control mode, when the temperature and the set value is positive DT2 (1 degree), but when it is dropped, the water will slowly open the valve, when the temperature and the set value is less than negative deviation DT2, but is on the rise and fall, the water valve will slow down. In short, for the control of the target parameters, temperature measurement values, set values, units of time, temperature deviation value less the "see more truly dynamic" will target parameter control. In order to save energy, according to the size of the outdoor temperature, winter conditions will drop in temperature setpoint 1 degree, summer conditions will improve temperature setpoint 1 degree, while taking full advantage of the new air valve chain function, in the transitional quarter full on fresh air valve, in summer or winter, the air supply valve can be kept to a minimum, so you can save energy up 12%.

Building automatic control system not only has a wealth of controls, but also a powerful management features, user-friendly interface design, filter clogging and fan failures will issue a sound and light alarm to remind managers clearance sin and maintenance, equipment uptime, regular maintenance of equipment, used in the process, and make full use of the building control systems, and air supply unit air conditioning units, according to the time-saving program, Kai/stop reflected in:

Intermittent operation: make the device a reasonable interval, but does not affect the environmental comfort and technology requirements.

Best startup: according to personnel usage or production processes, open air conditioning equipment in advance, summer take high winds and low temperatures in winter to take big air flow and high temperature; room temperature stable, low airflow.

Best off: according to personnel work situation or production processes, early air conditioning equipment.

(3) VAV system (VAV) is a new air conditioner, intelligent buildings air conditioning is increasingly applied. When the indoor temperature environment changes, change in air temperature and change the size of two air control mode can achieve the same results. Use of VAV system of air conditioning system can save energy by 40%, and only in the cooling load and thermal load peak is only used when the maximum air volume, so you can dramatically reduce energy consumption.

VAV system by adjusting motor with frequency inverter air conditioning units and variable air volume adjustable air valve terminal device. Monitoring includes control fan, and monitor the operational status of the fan, depending on the size of the indoor temperature, automatically adjusting the size of the new back to throttle and water valve to open degree to realize temperature control, keep the room temperature stability. With the VAV unit of air conditioning system links need to coordinate control, primarily in the following areas:

① due to the load in each room is different, then fed into the room air is changing, the air conditioner will change, so you should adjust the size of the frequency used for forced draft fan control.

② fan speed adjustment, you can set static or constant pressure control mode, make the room pressure remains stable, guarantee the equipment normal work.

③ for VAV system, you need to detect various room air flow, temperature and air-valve position signal, and after a comprehensive analysis of the process to give the air temperature setting values.

④ in air conditioning, new, should also be adjusted back to the air valve so that the room is full of fresh air to ensure the room air quality.

(4) cold source system is the core of the HVAC system, how to coordinate management crucial influence on the energy consumption is considerable, the amount transferred in GeneralAnd mass transfer two adjustment mode, volume adjustment is under load changes, adjust the frozen water pump's opening number, or by the frequency for water pumps, and then under cold source system total load weight (for water temperature and flow of multiplication) number controls the chillers. Quality adjustment is to adjust the temperature of the chilled water, usually in the low-load conditions, due to cooler outlet temperature increase several times, achieving optimal start and stop time control unit, enabling the device to run optimize equipment alternation of run time.

To a building, for example, frozen station system has four sets of refrigeration unit, 5 sets of frozen water pump (option a), 5 bed cooling water pump (option 1), 4 Tower and expansion tank, building automatic control system installed in the refrigerated room direct digital controller DDC to complete the control requirements of refrigerating units: chillers, cooling water pumps, cooling water pumps, cooling fan, cooling tower water inlet valve and the associated devices achieve linkage control, and monitor its health status and fault status. Test the temperature of the chilled water, backwater for return water pressure and flow of cooling water inlet and return water temperature, pressure, calculation of cooling load of air conditioning systems.

Implementation of coordinated control:

Frozen water valve to open → freezing water circulation pump (delay time 1 minutes) → cooling water valve to open → cooling water circulation pump open → Tower fan open → cold water host.

Linkage to stop order:

Cold water main organs → (delay time of 5 minutes) cooling fan off → cooling water circulation pump off (delayed 20 minutes) → cooling water valve clearance → freezing water circulation pump off → freezing water valve off.

In addition to the rigorous chain, running process, in order to protect the freezer, in the event of unexpected chilled water pumps, pump stops running, freezer must stop running, cooling water pumps must longer run.

Building automatic control system complete the above basic functions, but also major optimizations on the refrigerator, Central Station control acquisition field DDC data and Manpower, ongoing analysis to determine each time building load situation, determine the number of cold machine running through the traffic patterns on the site of the present order, DDC focused on solving the following problems.

① How to determine the chiller run initial number

Early in the system by artificial manual setting system running cold water unit number of the initial run, the system automatically records all operation on climatic conditions as well as hourly amount of cooling load and begin execution load forecasting and optimization of control software, accumulated to a certain extent, the monitoring system will be in accordance with load prediction results, and on climatic conditions, prior to the load and the system running data for analysis of empirical data, access to certain rules and progressive realization of the chiller system operation control optimization. To determine the initial operation of chiller units.

② How to implement a chiller operation number changes in the control

First, additional chiller control method

When the system load increases, monitoring system monitoring to the backwater of pressure reduction at both ends, frozen water increases, the unit according to their own load can be adjusted, when the chiller system load increases to its current percentage of 95% of the FLA (according to the actual situation adjustment), a single unit in full operation and water pump of full operation are no longer adequate for system load values and chilled water outlet temperature is not stable in water temperature setting, so the second generation of electric valve opening soon, after a certain time, the valve opens second units quickly opened.

The following calculation very abrupt, K should be clear what kind of rules, which determine the opening.

Where: T = CHWT-CHWT.STP

CHWT — chilled water outlet temperature

CHWT.STP — chilled water outlet temperature of the set value (7 ° c).

That is, set the value of the chilled water outlet temperature is 7 ° c, when ¡÷ T ≥ 0.3 ℃ (OLO), while the percentage of current water chillers FLA ≥ 95%, the second unit (running time shortest) automatically turns on.

Second, the automatic machine policy

Assuming that the two units are run when the system load variable hours, backwater differential pressure 2-side, that is, the response to the increase in the unit load corresponding decreases, when two units of load and even less than the total amount of only one unit when the total amount of load (two units < 50% of the FLA can be adjusted according to the actual situation), chiller group control system adequate time delay switch off one of the crew to make another unit in high-load efficiency conditions run at the same time meet the load requirements. According to the comprehensive efficiency chillers, water chillers curve control run within the scope of the best energy efficiency is the chiller group control purposes.
3 intelligent building automation system of the latest development trends

Initially, people in the building of the introduction of automatic control is designed to solve specific practical problems: temperature control, devices launch. With the building of smart devices continue to increase, continuous automatic control system limitations of the father: first, the traditional building system is still a relatively closed system, expressed in the communication protocols, the manufacturers or disjointed, mutually incompatible, system connection between the device cannot do connect seamlessly. Therefore, for a closed system, to building all device integration platform will have a lot of work to do, is not only costly, but poor performance; second, because the system is closed, from design, goods supply, installation, commissioning, upgrade can be performed only by factory owners powerless, monopoly, only passive acceptance, therefore, the initial investment is unprotected; third, today's rapid development of the computer world, product update cycles are getting shorter, building automatic control of the new products will emerge. For a closed system, the product's update will be the manufacturers of the boycott and monopoly, blocking technology, indeed to low cost tracking advanced technology development is impossible.

Hence, uses open, standard communication protocol is a building automation system development trend, the need to perform all common manufacturers, can completely change the status quo. Truly open systems, you must use a standard communication protocol and the agreement must be in the mainstream, to accept all manufacturers. Currently in use in the building automation system is generally the company launched in United States Echelon LonWorks technology agreement, generally use twisted pair connection, communication speed, using hand 76.8K bus communication distance of up to 2500m, free topology can also be reached 500m, LonTalk is the only peer-to-peer communications, its use to the full realization of openness and interoperability provides solutions that make the whole building automation system more modern, high-efficiency. Field device (such as valves and sensors) or you can use network of transport means, reduce the field of pipeline and the amount of construction projects. For now those or non-standard equipment, you can qualify for a transitional period, to provide for equipment-related agreements, building control central station itself has Modbus, BACnet, DDE, OPC interface plug-in functionality, such as through a programming interface software, and related equipment such as boilers and chillers, connection to building automation systems, with the popularity of the Internet, through password management way either in the Office or at home, or as long as you have access to the Internet where you can browse the entire building, equipment operation, management is simple and can save energy.

As a result of the use of advanced open building automatic control system, in line with international trends of the latest, product selection and more diversity in terms of system maintenance and upgrades to choose from a variety of devices, including manufacturers of DDC controllers, routers and other products, the effective control of running costs, protect existing investments, play a bigger role. At the same time in cognitive, design, construction, and other details more fuss about an integrated management approach, building automation role will be fully to the whole building management, energy efficiency, the real benefit of mankind, prospects will become more and more widely.