Technical analysis of low-cost energy-saving transformation of large commercial buildings?

Technical analysis of low-cost energy-saving transformation of large commercial buildings?

1, preface

The Outline of the Eleventh Five-Year Plan for National Economic and Social Development proposes that the energy consumption per unit of GDP will be reduced by 20% by 20 10 compared with the end of the Tenth Five-Year Plan, that is, the average energy consumption will be reduced by 4% during the Eleventh Five-Year Plan and by 1.2% in 2006. In June, 2007, the National People's Congress passed the "China People's Congress *", which clearly stipulated that energy-using units with annual comprehensive energy consumption 1 10,000 tons of standard coal should be the key energy-using monitoring units, and the key energy-using units should focus on energy-saving planning and transformation, and large commercial buildings should basically be the key energy-using units. In the increasingly fierce competition, the problem of energy saving is more urgent.

2. Energy consumption of large commercial buildings

With the rapid economic growth, the area of commercial buildings (hotels, office buildings, shopping malls, comprehensive buildings, etc.). ) is expanding day by day in China, accounting for 25.4% of the total construction area in China. At present, there are about 2000 high-class hotels, more than 3000 high-class office buildings, more than 800 large hospitals and more than 800 large shopping malls.

In general, in addition to the use of special equipment, the main energy consumption of large commercial buildings includes central air conditioning system energy consumption, lighting system energy consumption, cold and hot water energy consumption, electricity and other energy consumption. Taking Shanghai as an example, the energy consumption ratio of building lighting system is about 10% ~ 20%, air conditioning system is about 40% ~ 60%, and other power systems are about 30% ~ 40%.

3. Main measures for low-cost energy-saving transformation of large commercial buildings.

For large commercial buildings, the main energy-saving objects are central air conditioning, water supply and drainage, lighting and electrical energy saving.

3. 1 Low-cost transformation technology of central air conditioning

The energy consumption of central air conditioning accounts for 40% ~ 60% of the total energy consumption of commercial buildings, so energy saving of central air conditioning is an important means of energy saving of commercial buildings. Judging from the current operation of central air conditioning, there is a general situation of "big horse-drawn cart", that is, the selection of main engine and water pump in central air conditioning system is greater than the actual load demand of the system, resulting in a lot of energy waste. Although there are many methods for energy-saving transformation of central air conditioning at present, most of them are difficult and costly, such as using ground source and water source heat pump technology and ice storage technology. At present, there are mainly the following technical means that can be applied to the energy-saving transformation of central air-conditioning system at low cost.

3. 1. 1 central air conditioning automatic control technology (BA)

The automatic control technology of central air-conditioning can be easily combined with the automatic control technology of buildings to realize network control. According to the real-time load of commercial buildings, the host and other air-conditioning equipment can be adjusted, and energy can be saved as much as possible under the premise of ensuring indoor temperature and humidity. The automatic control system of central air conditioning includes the control of cold and heat sources (refrigeration host, boiler, etc.). ), water pump (freezing pump, cooling pump, hot water pump, supply pump, etc. ), cooling equipment (cooling tower and cooling well), terminal equipment (fresh air unit, combined air conditioning unit, fan coil unit, etc. ) and various fans and valves.

The main advantages of adopting central air conditioning automatic control technology are: it can automatically detect the room temperature and reduce the energy consumption of air conditioning equipment; Provide a comfortable environment that can be adjusted automatically; Prevent accidents and protect equipment investment; Prolong the service life of the equipment and reduce the management and operation costs; Unified management of all air conditioning equipment in the whole building; Complete all operations on the graphical operation interface. Its main shortcomings and shortcomings are: it needs secondary programming on site, which is greatly influenced by human factors; Due to the lack of advanced control algorithm model, the energy saving effect is not ideal; High maintenance cost in the later period; Energy saving effect is difficult to evaluate.

3. 1.2 fuzzy variable frequency control technology for main engine room

The fuzzy variable frequency control system in the main engine room mainly manages the energy-saving operation of energy-consuming equipment in the freezing room. Because the equipment energy consumption of freezer accounts for about 50% of the energy consumption of commercial buildings, the application of this technology in commercial buildings is very valuable.

The main advantages of fuzzy frequency conversion technology in the main engine room are as follows: energy-saving transformation is limited to the main engine room, and the transformation period is short and easy to realize; The energy saving rate of air conditioning in large shopping malls is as high as 20% or more; Less investment, short payback period, generally about three years; It is also convenient to bring the frequency conversion control of terminal equipment into this system; Networking or cooperation with BA system is also very convenient. Its disadvantages are: the energy-saving rate fluctuates with the change of season and passenger flow, and the workload of calculating the energy-saving rate is large; The service life of the system is short, about 15 years.

3. 1.3 fresh air ventilation technology

Large commercial buildings are extremely crowded places, and when air conditioning is running, generally speaking, except the first floor, the doors and windows of other floors are relatively closed, so the number of indoor natural ventilation is very small. It is necessary to rely on the air conditioning system to deliver fresh air indoors, and at the same time, the exhaust system needs to exhaust the same amount of indoor air and fresh air outdoors to meet the health requirements of the crowd. Because the outdoor air temperature is low and high in summer, it is a scientific energy-saving measure to reduce the inlet air temperature of outdoor air through heat exchange between outdoor air and outdoor air, which can save a lot of refrigerator cooling capacity.

The main advantages of adopting fresh air ventilation technology are: it can recover the cold heat of indoor air and save a lot of energy consumption of refrigerators or boilers; The energy saving rate of air conditioning in large shopping malls can be as high as 20%; Less investment, short payback period, generally two years. Its main shortcomings and shortcomings are: large volume, large air-conditioned room, and the transformation of air duct system, it is difficult to transform the built shopping mall; Because the air dust needs to be cleaned regularly, the maintenance workload is also relatively large.

3.2 Lighting energy-saving technology

In commercial buildings, lighting energy consumption is generally second only to central air conditioning, but the energy-saving transformation of lighting must be completed on the basis of ensuring the illumination in the building. If energy saving is achieved at the expense of lighting, people in the building will feel uncomfortable and affect the management effect of commercial buildings. Commonly used lighting energy-saving and low-cost transformation technologies include replacing energy-saving appliances, installing lighting power saver and lighting automatic control system.

3.2. 1 Replace energy-saving lighting fixtures.

At present, the lamps used in commercial buildings are mostly T8 fluorescent lamps, compact fluorescent lamps or metal halide lamps and tungsten halide lamps used to highlight the characteristics of commodities and buildings. It is difficult to replace lamps and lanterns in large shopping malls due to actual use requirements and installation characteristics. T8 fluorescent lamp is widely used in large supermarkets, office buildings, hospitals and large underground parking lots of commercial buildings, and the lighting time is also very long. Therefore, replacing lamps and lanterns has broad energy-saving prospects.

According to the data, energy-saving lamps save 80% electricity compared with incandescent lamps, with a life span of 5 times and a light efficiency of 3.5 times. Although the cost of energy-saving lamps is several times higher than that of incandescent lamps, the difference can be saved in future use, which is more cost-effective.

Practice has proved that replacing energy-saving light sources and lamps is the most effective lighting energy-saving measure without affecting the lighting effect. But at present, energy-saving lamps emerge one after another, and the quality of products is also mixed. When choosing to replace lighting fixtures, we should choose the right products strictly according to the actual needs.

3.2.2 Installation of lighting economizer

Installing lighting economizer can stabilize voltage, filter and improve power factor, and achieve the effect of saving energy and prolonging the service life of lamps. However, the effect of installing lighting economizer in buildings with good power quality is not obvious, and some will reduce the illumination in buildings, so it is not suitable to use lighting economizer in occasions with strict requirements on illumination.

3.2.3 Automatic lighting control system

The intelligent lighting control system can intelligently and flexibly control the start, stop and dimming of the lighting system of large commercial buildings, and make the lighting system as energy-saving and beautiful as possible while ensuring the illumination. Specifically, it includes an automatic timing switch lamp; Automatically open and close according to the light; Automatic dimming according to illumination; Change the preset scene lighting mode.

The main advantages of automatic lighting control technology are: flexible scene control; Control lighting according to illumination or personnel entry; Computer can be used for unified control and management to improve efficiency; Can be controlled remotely. Its main shortcomings and shortcomings are: the system structure is complex and requires high-level operation and maintenance personnel; Energy saving effect is difficult to evaluate; The system focuses on improving management efficiency, supplemented by energy saving, and the measurable energy saving rate is not high.

3.3 Building water supply and drainage system energy saving

The water consumption of commercial buildings is an important part of building energy consumption. At present, facing the situation of increasingly scarce water resources, water saving in commercial buildings is also of great significance. However, some technologies (such as reclaimed water reuse, etc. ) Because of its complex building structure and great difficulty in reconstruction, it is difficult to realize in existing buildings. Common low-cost renovation technologies of water supply and drainage include: replacing water-saving appliances, saving water in air conditioning cooling water, etc.

3.3. 1 Replace water-saving appliances.

Using water-saving appliances is the most direct means to save water in commercial buildings, such as installing water-saving toilets, installing infrared sensing faucets, water-saving showers, etc. Or install a water-saving valve (you can add bubbles to the tap or shower head) to save a lot of water.

3.3.2 Cooling water saving technology

The water consumption of air conditioning cooling water is huge, accounting for 50% of the total water consumption of shopping malls and office buildings in summer. For the cooling water system with the circulating water volume of 1000m3/h, the normal evaporation water volume is about 8.5m3/h, which is about 100t/ day. The floating water is about 2.5m3/h, about 30 tons per day; Sewage discharge is about 4m3/h, about 50 tons per day. Among them, except evaporation of water is a necessary loss, bleaching water and sewage have huge water-saving space.

Under the cooling tower fan, a certain wavy water baffle can prevent water droplets from splashing, which can effectively reduce the floating amount of cooling water by 80%, but the air resistance is increased.

Flushing toilets with sewage from cooling towers and greening irrigation are important measures to save water in cooling water. Generally speaking, the flushing water volume of large commercial buildings is more than 50% of the cooling water sewage volume. The advantages of flushing toilets with cooling water are: increasing the amount of sewage and improving the quality of cooling water; Saving the consumption of cooling tower; The supplement of low-temperature tap water reduces the temperature of cooling water, thus reducing the power consumption of the main engine and cooling tower.

3.4 Electrical energy saving

The main transformation measures of electrical energy saving in commercial buildings include installing equipment to improve power quality, elevator kinetic energy feedback energy saving and escalator energy saving control system.

3.4. 1 Install equipment to improve power quality

The existence of a large number of harmonics and reactive power will not only adversely affect the normal use of commercial building equipment, but also interfere with electric energy measurement and cause electric energy loss. By installing equipment to improve power quality, the power consumption quality of commercial buildings can be effectively improved, and the energy saving efficiency in hotels and office buildings can reach 8% ~ 15%.

The advantages of improving power quality and saving energy mainly include: the equipment is installed in the power distribution room of the building, and the transformation will not affect the business; The reconstruction project is small and easy to realize; Small investment, quick effect and easy measurement and evaluation of energy-saving effect. The main disadvantages are: the installation of energy-saving equipment on the high-voltage side requires the permission of the electric power department, which brings certain difficulties to the transformation; Different projects have different solutions to power quality, and the workload of preliminary investigation and evaluation is heavy.

3.4.2 elevator kinetic energy feedback energy-saving technology

The frequency conversion governor can convert the mechanical energy generated by elevator deceleration or poor mass between elevator car and counterweight into electrical energy, which is stored in the large capacitor of DC link of frequency converter, and the electrical energy stored in the large capacitor is fed back to the power grid through the active energy feedback device without consumption. So as to achieve the purpose of saving electricity, and there is no power consumption and high power resistance, which greatly improves the operating environment of the system.

The analysis and calculation and prototype measurement show that the faster the elevator pace, the higher the floor and the smaller the mechanical transmission consumption, the more energy can be sent back to the power grid, and the maximum amount of electricity sent back can reach 40% of the total elevator consumption.

3.4.3 escalator energy-saving control system

Add a passenger sensor at the entrance of the escalator to stop running when no passengers arrive. When passengers arrive at the entrance induction area, the elevator automatically starts running. If no new passengers arrive after a passenger transport cycle, the elevator will automatically stop running. The passenger transport cycle begins with the arrival of the last passenger.

The elevator starts and stops smoothly without jumping. Gradually accelerate to full speed when starting, and gradually slow down to zero speed when stopping.

The escalator energy-saving control system has remarkable energy-saving effect, and the energy-saving efficiency can usually reach 20% ~ 60%.

4. Comparative analysis of energy-saving technologies

At present, there are many energy-saving technologies in commercial buildings. Combined with the current energy-saving situation of commercial buildings, the above low-cost transformation technologies can be compared by fuzzy analysis, and the comparison results are shown in the following table.

Through comparison, it can be found that the following four technologies should be given priority in the energy-saving transformation of shopping malls: fuzzy frequency conversion control system in the main engine room; Replace energy-saving light sources and lamps; Cooling water saving technology; Install equipment to improve power quality. Their similarities are mainly reflected in:

(1) The energy-saving technology is mature, with a large amount of energy-saving renovation and low risk;

(2) The energy-saving transformation is simple, the cost is low, and the normal use of commercial buildings is not affected;

(3) Energy-saving benefits can be measured, which is convenient for energy-saving comparative analysis;

(4) Short payback period and high return on investment.

5. Concluding remarks

According to statistics, large-scale commercial buildings consume a lot of energy, and the energy consumption per unit building area is 10- 15 times that of residential buildings, with about 25%-30% energy-saving space. Due to the cost, large commercial buildings tend to adopt energy-saving technology with no cost or low cost for renovation. From the comparison of energy-saving investment and income, priority should be given to the fuzzy variable frequency control system in the main engine room, the replacement of energy-saving light sources and lamps, the water-saving technology of cooling water and the installation of equipment to improve power quality.

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