Often the main compressor station is placed near the main loads demanding compressed air, to decrease the pressure drops along the lines. It is not uncommon to find the main station placed underground, or in inner rooms inside the installation. In such cases, there is normally a lack of fresh air to feed the compressors, and the motors are compelled to compress the ambient air, which is generally at a temperature higher than the outside air temperature. For thermodynamic reasons, the compression of warm air requires more energy than the compression of cool air. In technical literature, it is found that each increase of 5 °C of inlet air temperature at the compressor causes an increase of ab out 2 % of the power needed. This energy can be saved simply by feeding the compressed air station with outside air, especially in cold seasons, when the difference between outside and inside temperatures can be several times greater than 5 °C, depending on the location. A duct can be installed connecting the outside and the intake of the compressor, or to the entire compressed air station. A fan may be required, depending on the length of the duct, and this energy should be considered during planning. The outside intake should be placed on the north side, or at least in the shade for most of the time.
主壓縮機站往往會設置在靠近需要壓縮空氣的主要負載處，以減少管路壓降。把主壓縮機站設置在地下或設施室內的情形比較少見，在此情況下，空壓機通常無法得到新鮮空氣作為進氣，馬達被迫壓縮溫度較外界高的周圍空氣。以熱動力學來說，要壓縮溫度高的空氣比冷空氣需要更多的能量。技術研究報告指出，壓縮機的進氣溫度每增加5 °C，將增加2%的電力需求。此2%的能源需求其實可用外界空氣給壓縮空氣站作為進氣而節省下來，尤其是在寒冷季節更為有效。寒冷天候室內外溫度差因地區的不同可能是數倍的5 °C。為解決這個問題，可用風管從室外(外面)連接到壓縮機進氣口，或連接到整個壓縮機站。如果風管的距離長，可能需要加裝風車，其使用的能量在計畫時就要一併計算進來。室外風管進氣口要裝在北邊或至少經常曬不到太陽的位置。
Reducing the compressors inlet air temperature by feeding cool air from the outside is always possible. Sometimes it is sufficient to open a circular hole in a wall, and install a duct connecting the outside intake with the compressor intake. When the CA station is located in a situation where access to the outside is difficult, the ventilation of the room should be improved. It is estimated to be applicable in 50 % of cases.
The reduction o f the air temperature entering the compressor involves economic advantages such as: the cold air feed is free; the reduction of running use of compressors (savings of kWh); the reduction of electric power supply (savings of kW).
Energy Efficiency (2009) 3.7.8