Why should we pay attention to the operating energy consumption of the fan box? Calculate costs based on annual operating conditions
Direct answer: The annual power consumption of the fan box is equal to the sum of the input power of the entire machine during each operating period multiplied by the corresponding operating hours. The nameplate power is only the upper limit of the motor's capability and does not equal the annual power consumption. Only looking at the maximum power multiplied by the number of hours throughout the year will overestimate the actual power consumption; only looking at low-speed operating conditions will miss high-load periods. To calculate the operating costs, the annual operation must be divided into several working conditions and accumulated separately.
Aili Industry is discussingWhen planning the wind turbine box , the project is usually required to provide the power and hours during the working period and the low load period, and then total the kilowatt-hours based on the number of operating days per year. The energy consumption data obtained in this way has more reference value than just looking at a power number.
Nameplate power is not the year-round power consumption
At different speeds, air volumes and resistances of the fan box, the input power of the whole machine may vary greatly. The motor may operate close to full load under design conditions, but may only have 30% to 50% of the rated power during night duty. If more than half of the annual operating time is in a low-load state, using full load power to estimate the annual power consumption will result in a significantly higher estimate.
On the other hand, if the calculation is only based on low load power, the electricity consumption during peak production hours will be missed. The correct approach is to break the annual operation into several typical working conditions, record the input power and operating hours of the whole machine in each working condition, and then multiply the items one by one and add them up.
The input power of the whole machine should be measured on site or on the test bench, rather than replaced by the rated power of the motor. The rated power of the motor is used to define the capacity of the motor. The input power of the whole machine is the actual power consumption of the fan box under specific working conditions. It includes the comprehensive result of motor loss, driver loss and fan aerodynamic efficiency. The two are not the same number.
Write down the electricity bill calculation clearly
Assume that a system has two modes: working period and low load period every day. During the working period, the input power of the whole machine is P1, and the operating hours are t1; during the low load period, the input power of the whole machine is P2, and the operating hours are t2. The number of operating days throughout the year is D, and the annual power consumption is approximately (P1 × t1 + P2 × t2) × D.
The electricity price only affects the amount of the fee and does not change the power consumption of the device itself. If the terminal air volume is different before and after the transformation, the working conditions should be corrected first, and then the energy saving benefits and payback period can be discussed. For example, the air volume has been reduced after the transformation, but the terminal demand does not require such a large air volume. This 'energy saving' comes from demand correction, not equipment efficiency improvement, and the two should be evaluated separately.
If the system has a filter section, the resistance of the filter will increase with dust accumulation. The pressure difference allowed before maintenance should be used for the design working conditions, and the clean state or typical operating state can be used for common working conditions. System end configurationWhen using HEPA/ULPA high-efficiency filters , the initial resistance of the filter and the resistance at the end of use should be included in the calculation of the working point. When the process requirements are higher, it can be evaluatedDoes the ULPA ultra-high efficiency filter meet the requirements?
First find out 'the extra wind'
Energy saving analysis cannot just focus on the motor. Long-term valve throttling, high air volume settings, abnormal filter resistance, or air duct leakage will all cause the system to consume extra energy. First review the minimum terminal demand and actual operating period, and then decide whether to optimize the pipeline, adjust the control strategy, or replace the power equipment.
A common situation on site is that the system is selected according to the maximum load during design. In actual operation, the terminal demand is far lower than the design value, and the operator can only adjust the air volume by turning down the valve. In this operating mode, the fan is still running at high speed, and the excess air volume is consumed by the valve. It is more effective to deal with this type of system loss first than to directly replace the high-efficiency motor.
Air duct leaks are equally easy to overlook. Air leakage will cause the fan to supply more air, but not enough air volume at the end. By measuring the air volume of the main branch and the air volume of the fan outlet, you can determine whether the air leakage is serious. If the air leakage rate is high, repair the air duct first, and then evaluate whether the power equipment needs adjustment.
Base the comparison on the same level of service
Aili Industry is discussingWhen the DC fan box is used for new construction or energy-saving renovation, it is recommended to record the target air volume, the most unfavorable point pressure difference and the complete machine power at the same time. Only when the old and new solutions meet the same air supply requirements will the power comparison be meaningful.
From the fan law, the air volume is proportional to the rotational speed, and the shaft power is proportional to the cube of the rotational speed. The rotation speed is reduced by 20%, the air volume is reduced by approximately 20%, and the shaft power is reduced to approximately 51% of the rated value. This is the fundamental reason why speed regulation can save energy. However, the actual energy saving depends on the load curve, system resistance characteristics and speed regulation strategy. If the system operates at full load for a long time, the energy saving space of the DC solution mainly comes from the improvement of motor efficiency; if there are obvious duty or partial load periods, the benefits brought by speed regulation will increase significantly.
Clean room ceiling air supply can be compared simultaneouslyFFU fan filter unit ; centralized management of multiple devices can be matchedThe FFU computer group control system realizes zone speed regulation and status monitoring. Protection of single process equipment can be consideredEquipment-side fan filter unit (EFU) . The final filtered air supply at the end of the air duct can beHigh-efficiency air supply outlet (HEPA BOX)。
What data needs to be recorded for energy consumption analysis?
A basic record that can be used for energy consumption analysis should at least include:
The input power of the whole machine in each operating period
Operating hours and annual operating days for each operating period
Corresponding air volume and external static pressure
Filter status and valve opening
Control mode (fixed speed, speed regulation, duty mode)
Electricity prices and annual operating costs
Power figures for test conditions are missing and cannot be used for energy saving comparisons. The energy saving range is still based on project testing and actual operating time. The energy saving effect cannot be promised based on sample parameters or a single percentage.
Aili Industry is discussingWhen planning the fan box , operating condition data can be provided according to the project to assist in checking the power configuration and expected energy consumption. Specific structure and configuration options can be found inIt is confirmed in the fan box product catalog that non-standard projects should provide equipment or machine room drawings, and then shape them based on the determined working points and on-site interfaces.
