Energy Consumption Optimisation for Compressed Air Systems

A large machinery manufacturing company in South China operates six screw air compressors (three 200kW and three 160kW), primarily supplying compressed air to pneumatic tools, automated instruments, and material conveying systems in the workshop. The annual electricity consumption is approximately 5.2 million kWh, accounting for 19% of the total electricity consumption of the entire factory. During the initial operation, the energy consumption remained high due to issues such as improper pressure settings and frequent loading and unloading.

The renovation focused on optimising loading and unloading pressures, coupled with leakage management and group control optimisation. First, pressure parameters were optimised, reducing the compressed air station’s outlet pressure from 0.78MPa to 0.68MPa. Local pipeline modifications were made to lower pressure losses to 0.05MPa, ensuring a stable end-of-line pressure of 0.63±0.02MPa. The loading and unloading pressure differential was adjusted to 0.18MPa to minimise frequent loading and unloading and reduce unloading energy consumption. Second, a specialised leakage management program was implemented, using ultrasonic detectors to comprehensively identify leakage points, replace aged seals and hoses, and apply anti-corrosion sealing treatments to connection points. A monthly leakage inspection system was established. Third, the intelligent group control system was upgraded to dynamically schedule the operation of the units based on the load, prioritising the start of more energy-efficient new machines, and balancing the operating time of each equipment to maintain a load rate between 75% and 85%.

After the renovation, the system’s operational indicators significantly improved: the annual electricity consumption dropped from 5.2 million kWh to 4.664 million kWh, saving 536,000 kWh, with a 10.3% electricity savings rate. The average specific power decreased from 7.2kW/(m³/min) to 6.4kW/(m³/min), a reduction of 11.1%. The system leakage rate decreased from 23% to 7%, and the frequency of loading and unloading was reduced to 3-4 times per hour. The proportion of unloading energy consumption dropped below 20%. Based on an industrial electricity price of 0.8 yuan per kWh, the annual electricity cost savings amounted to 428,800 CN¥. The total renovation investment was 950,000 CN¥, resulting in a static payback period of just 2.2 years. Additionally, equipment wear and tear was reduced, and maintenance costs were reduced by an average of 15% per year, significantly enhancing overall efficiency.