How to calculate the electricity consumption per cubic meter of air compressor

Calculation Method of Energy Consumption per Unit Gas Production of Air Compressor

air compressor is the core energy consumption equipment in the industrial field, and its energy consumption per unit of gas production is the key index to evaluate the operation efficiency. Now on the calculation method and optimization path for professional description:

1. Foundation Calculation Formula
energy consumption per unit of gas production (kWh/m & sup3;)= total electricity consumption (kWh)÷ compressed air production (m & sup3;)

2. Data Acquisition Specification

1. electricity metering

• it is necessary to configure an independent meter to measure the power of the main circuit of the air compressor to avoid mixing with other equipment.
• The measurement cycle is recommended in units of complete production shifts (e. g. 8 hours) to ensure data representativeness
• frequency conversion equipment needs to record the operating frequency curve and calculate the weighted average power.

2. determination of gas production

• install gas flow meter to measure volume flow under standard condition (0 ℃,101.325kPa)
• regularly check the accuracy of the flowmeter, and the error shall be controlled within ± 1%
• record the ambient temperature and pressure, and convert the actual working condition to the standard state.

Correction of 3. influencing factors

1. environmental parameter compensation

• temperature correction coefficient: Kt = (273.15)/(273.15 + t) ,t is intake air temperature (℃)
• pressure correction coefficient: Kp = (101.325)/(101.325 + & Delta;p) ,& Delta;p is intake pressure loss (kPa)
• actual gas production = reading of flowmeter × Kt × Kp

2. equipment efficiency conversion

• load rate correction: actual energy consumption = meter reading × load rate (running time/total time)
• deduction of unloading energy consumption: for equipment with automatic start-stop function, the empty power consumption in the unloading state shall be deducted.

4. optimization calculation example
in a factory screw air compressor as an example:

• 8-hour shift meter reading: 1200kWh
• flow meter shows gas production: 9600m & sup3;
• intake air temperature 35 ℃, pressure loss 5kPa

calculation process:

1. temperature correction coefficient Kt = 273.15/(273.15+35) = 0.892
2. pressure correction factor Kp = 101.325/(101.325+5) = 0.953
3. actual gas production = 9600 × 0.892 × 0.953=8147m & sup3;
4. unit energy consumption = 1200 ÷ 8147=0.147kWh/m & sup3;

5. energy efficiency improvement path

1. leakage management

• periodically conduct pipe network pressure holding test, and the leakage rate shall be controlled within 5%
• use ultrasonic leak detector to locate small leak points, typical repair investment payback period <6 months

2. pressure optimization

• under the premise of ensuring the quality of gas, the energy consumption can be reduced by about 7% for every 0.1MPa reduction in system pressure.
• Determine the economic gas supply pressure by pipe resistance calculation: & Delta;P = (& lambda;L/D)(v² & rho;/2g), where & lambda; is the friction coefficient, L is the pipe length, and D is the pipe diameter

3. thermal energy recovery

• air compressor waste heat recovery rate can reach 70%-94% of the input power
• 1m & sup3;/min annual heat recovery of air compressor is equivalent to 3.5 tons of standard coal

enterprises should establish an energy consumption monitoring platform to collect electrical parameters and gas production data in real time to generate energy efficiency curves. When the unit energy consumption exceeds 0.15kWh/m & sup3;, it is necessary to start a special diagnostic program to improve the equipment efficiency, pipe network design and gas management. Through systematic optimization, energy consumption per unit of gas production can be reduced by 15%-30%, significantly improving energy efficiency.