Linking energy efficiency measures in industrial compressed air systems with non-energy benefits - A review

Compressed air is widely used in supporting industrial manufacturing processes due to its cleanness, practicality and ease of use. However, the efficiency of compressed air systems is often very low. Typically, for compressed air-driven tools only 10-15% of the energy input is utilised as useful work. Despite these recognised inefficiencies, and even though energy efficiency measures for compressed air systems normally offer several opportunities for energy savings and energy cost savings, generally, less attention has been given to the energy use and energy costs incurred in compressed air systems. Industrial energy efficiency measures might also yield additional effects, beyond the energy savings, which are denoted as non-energy benefits. This study reviews the existing base of scientific knowledge on energy efficiency in compressed air systems combined with the perspective of non-energy benefits. Even though some measures were mentioned more frequent than others, the results revealed significant variation in which measures could be undertaken to improve energy efficiency in compressed air systems. However, few publications employ a comprehensive approach by examining the entire compressed air system. Furthermore, few publications have addressed the possible additional benefits to be gained from energy efficiency measures in compressed air systems. This study provides a compilation of the various energy efficiency measures reported in the reviewed scientific literature that can be undertaken in order to improve energy efficiency in compressed air systems. It also provides a comprehensive take on the measures, including a systems perspective, by categorising them in respect to where in the compressed air system they can be undertaken. This paper suggests that energy efficiency measures in compressed air systems, and related non-energy benefits, should be studied on a specific measure level to fully understand and acknowledge their effects on the energy use of a compressed air system and possible additional effects, i.e. non-energy benefits.