Air conditioning energy saving system engineering
Energy saving measures for air conditioning systems "from design to operation"
If the air conditioning system adopts reasonable design and operation measures, it can save the energy consumption of air conditioning, save resources, reduce carbon emissions, and avoid unnecessary cost of power distribution and capacity increase. Taking appropriate design and operation measures is the trend of benefiting the country and the people for users.
How to take effective measures in the design and operation of air conditioning system to achieve the goal of energy saving?
First, the design of air conditioning system and the trend of reducing energy consumption
The reduction of energy consumption of air conditioning systems is firstly to reduce the cooling capacity and heat loss, secondly to reduce the consumption of water and electricity, and to take reasonable and appropriate measures to implement low-cost operation.
Energy consumption of air conditioning refrigeration system According to relevant statistics in the industry, the largest proportion of energy consumption of air conditioning system is the central air conditioning system host and terminal equipment.
According to the current professional design method, according to the medium used in indoor heat and humidity load, it can be divided into all-water system, refrigerant system, air-water system, all-air system; According to the concentration of air treatment equipment can be divided into centralized and semi-centralized; According to the source of the treated air, it can be divided into closed, direct flow, and mixed (one return air and two return air).
Air conditioning system is usually composed of cold and heat source unit, cooling tower, air cabinet, cooling water circulation pump, chilled water circulation pump, water supply device, fan coil and other equipment; Air conditioning heating and cooling system is an indispensable functional system in various types of building facilities. Air conditioning system not only improves human working and living environment, but also consumes a lot of social energy. At present, the whole society to reduce carbon emissions, energy saving and consumption has been the general trend, it is imperative.
Two, reduce the air conditioning system energy consumption of multiple ways and measures
1. The design stage adopts the new technology of full heat recovery fresh air exhaust system
For projects with suitable comprehensive conditions, the full heat recovery fresh air exhaust system can be used in the design, such as large supermarkets, restaurants, factories, exhibition halls and other buildings, which can replace the previous independent new fans and exhaust machines in the system design, recover heat from the discharged wind, and be used for new air preheating and precooling, dehumidification, which can save the cooling and heat energy consumed by the original independent new fans. It is an effective new technology to save energy and reduce consumption.
2. The new technology of automatic cleaning of condenser is adopted in the design stage
The basic principle of automatic cleaning of condenser is to send the sponge ball into the condenser regularly and quantitatively through a device to wash the scale, sludge, bacteria and algae on the inner wall of the copper pipe, so that the condenser can reduce the thermal resistance and maintain the best heat energy state. At present, the design of air conditioning system has been stipulated to use the condenser automatic cleaning technology, for building energy saving renovation projects, for the old air conditioning system energy-saving transformation also began to use the condenser automatic cleaning system, to achieve the effect of energy saving 10 to 30%; It is a new technology to improve operation efficiency, reduce carbon emissions, and save energy and consumption.
3. Attach importance to equipment selection and system matching in design
In the preferred design method of air conditioning system, the cold water system of air conditioning mostly adopts the idea of 1 stage pump constant flow. The selection of the pump is selected according to the maximum load of the chiller, and it takes into account the operation of a fixed water flow throughout the year.
Many air conditioning systems run when the terminal device is off. As the water valve is normally open, the temperature of the return water pipe decreases, resulting in a small temperature difference between the supply and return water pipes. Due to the difference in energy consumption between day and night during the operation of the system, the user's energy consumption requirements in the building indoor environment temperature, the use of functions and other aspects will be different, and the actual operation of the air conditioning load most of the time in the year, the temperature of the air conditioning system is much higher than the design value. Low load phenomenon, there are many actual project cases show that the air conditioning system in a year about 40%~60% of the time, the actual operating load running in the state of 30%~50% below the design load changes, so when the cold water flow remains unchanged, the temperature difference between the supply and return water may be reduced from the original design of 5 ~ 7 ° C to about 1.0 ° C temperature difference. Therefore, the air conditioning system mostly operates in the case of large flow and small temperature difference, resulting in the circulation of the pump. The waste of energy consumption in the process of conveying energy also increases the loss of heat and cold in the pipeline system. From the process and data analysis of air conditioning system to adjust the indoor ambient temperature of buildings, it can be seen that the lower the indoor temperature in summer, the lower the relative humidity. The energy consumption of the system equipment will be greater; In winter, the higher the indoor temperature is, the higher the relative humidity is, and the energy consumption of the system equipment is the largest. This phenomenon proves that the pre-construction investment and the later system operation cost will increase correspondingly.
4. Combined optimization of system design and operation control
The system design takes into account the determination of the ambient temperature comfort zone range. In the design, higher temperature and humidity values can be selected for cooling in summer. In winter heating, lower temperature and humidity values are adopted to ensure that the design and operation can achieve the purpose of saving energy consumption. The change of indoor temperature and humidity in the building has a certain correlation with energy conservation. According to the relevant data of the industry, if the set temperature of the unit is lowered by 1℃ in the summer, the energy consumption will increase by 9%; Increasing the set temperature by 1 ° C in winter will increase energy consumption by 12%. Therefore, the indoor temperature and humidity control in a reasonable comfort zone of a certain precision range, is the most effective energy-saving method of the air conditioning system, so in order to reduce energy consumption, air conditioning room indoor temperature and humidity base, under the conditions of meeting the production needs and living comfort, as much as possible in summer, winter should be reduced as much as possible, air conditioning system operation energy-saving effect is the most obvious; Therefore, the accuracy of the signal measured at the front end of the air conditioning system directly affects the precise control degree of the air conditioning system.
Therefore, the measured signal data of temperature and humidity must be accurate, and BAS with high control accuracy should be used to control the air conditioning unit and system, because the opening of the electric water valve can be directly controlled. In addition, the calculation and control software of some systems can be combined to improve the accurate control of temperature and humidity of the air conditioning system, and the energy-saving management effect of the air conditioning system is better.
5. Adopt new risk control system
According to the comfort requirements, the total fresh air volume is generally controlled at about 10% of the total air volume, which can save energy. Some air conditioning systems return air volume is less than 90%, the return air volume is small, and the fresh air heat load is increased indefinitely, which is not energy-saving operation.
6. Design and use frequency conversion control mode to run the pump and fan equipment
The chilled water and cooling water circulating pump of the air conditioning system will consider a margin of 10 to 20% in the flow design, the load will fluctuate and change during the operation of the system, the unit will also load and reduce the load, and the chilled water flow can also increase or decrease accordingly. The energy saving technology stipulates that when the temperature difference of the outlet and return water of the host is 5℃, the economic flow of freezing and cooling water is large. When the temperature difference is <5℃, the flow is large, the host is energy-saving, and the pump consumes more energy. When the temperature difference is >5℃, the pump saves energy, the host consumes energy, and even the operation will be unsafe. Use temperature sensor, pressure difference sensor, PLC and inverter to control the speed of refrigeration, cooling pump, temperature difference =5℃, refrigeration, cooling pump operation can save 30 to 50%.
