The ZW series oil-free single screw air compressor is both eco-friendly and energy-efficient. The compressor uses pure drinkable water as a lubricant, which is used for sealing, cooling, and lubrication. The water is injected and fills the gaps inside the compressor chamber to minimize the leaking of compressed air, significantly reducing power consumption and ensuring better compression efficiency than dry compressors. When compared to single stage dry compressors, the ZW series have a 15% increased capacity. The compression cycle produces near-ideal isothermal compression to ensure high compression efficiency. The compressor also produces sterile compressed air and uses oil-free lubricant to minimize environmental pollution and maintenance costs. The compressor is designed with a unique single-screw force-balance structure with low operating noise.