Below are several commonly used energy-saving technologies for air compressors:
1. Reactive Power Compensation
Air compressors typically use asynchronous motors, which have relatively low power factors ranging from 0.2 to 0.85, varying significantly with the load and leading to high energy losses.
Reactive power compensation enhances the power factor under normal motor operation, reducing energy waste. Installing power capacitors at the electricity receiving end can effectively improve the power factor, especially suitable for continuously running medium-sized low-voltage motors.
2. Variable Frequency Drive (VFD)
Variable frequency drive energy saving involves placing a VFD between the electrical grid and the motor to change the voltage and frequency, thus controlling the motor speed. By regulating the speed of the air compressor with a VFD, energy consumption can be reduced, particularly under light load conditions, aligning the discharge volume with the actual air consumption.
Practice has shown that using VFDs can significantly improve the efficiency of air compressors under light load conditions and reduce energy consumption, thereby generating better economic benefits. The system controls the output pressure, sends feedback signals to the VFD, compares them with the set signals, and adjusts the motor's speed and power according to pressure changes through PID regulation.
3. Multi-unit Group Control
In situations with large air consumption and fluctuating loads, using a single large-capacity air compressor can be inadequate for adjusting the air volume. Multi-unit group control technology is an effective method to save energy when operating multiple air compressors. It selects the necessary machines and numbers based on actual air consumption, eliminating unnecessary waste and achieving significant energy savings. Screw compressors can reduce unloaded running time through group control systems, adjusting supply pressure according to the actual demand, enhancing energy efficiency.
4. Waste Heat Recovery
During compression, over 90% of electrical energy is converted into heat, which is largely wasted. In engineering, the recoverable heat energy can account for no less than 70% of the electricity consumed by an air compressor. The recovered heat can be used for domestic heating, boiler feedwater preheating, process heating, and space heating. Waste heat recovery can reduce the exhaust temperature of air compressors, extend their lifespan, and prolong the usage period of the cooling oil, among other benefits.
5. Techniques to Improve the Energy Efficiency of Air Compressor Operations
1)Use of High-Efficiency Motors
The load ratio of air compressor motors should be maintained above 80% to enhance energy efficiency. Therefore, selecting high-efficiency motors and reducing the motor size are essential steps. Y-type step motors consume 0.5% less power than traditional JO-type motors, and YX-type motors have an average efficiency that is 3% higher.
2)Improving Transmission Efficiency
High-quality belts and pulleys can significantly enhance the efficiency of V-belt drives. If the tension of V-belts is found to be inconsistent, they should be replaced as a complete set to avoid uneven load distribution. To ensure the required wrap angle and tension force, it's crucial to adjust the distance between pulleys and improve installation precision. Modern coaxial designs with the motor rotor eliminate losses from mechanical transmission, increasing airflow and allowing full-range speed control of the equipment.
3)Reducing Friction Losses
In reciprocating air compressors, the internal movement of pistons generates significant friction, which directly impacts efficiency. Ensuring optimal lubrication between the cylinder and piston, regular maintenance of piston rings, using clean lubricating oil, and checking oil levels are essential practices to minimize friction and maintain compressor performance.
4)Minimizing Pressure Losses and Leaks
The air path system of an air compressor, which includes intake and exhaust valves, filters, and seals, plays a critical role in the compressor's operation and safety. Utilizing advanced pressure reduction components and designing systems to minimize airflow resistance can significantly reduce energy consumption. Moreover, addressing traditional issues of internal and external leaks can enhance the efficiency of air compressors by avoiding repetitive compression operations.
Equipment, operational management, and comprehensive analysis are vital to ensure the energy-efficient, stable, and safe operation of air compressors. While implementing advanced technologies like VFDs, it is also crucial for staff to manage and maintain equipment diligently to support production and achieve energy savings, thereby enhancing economic and social benefits.