## 1 Introduction
Direct heat utilization, though simple and effective, is limited by the lack of a suitable heat demand that can be matched with the waste compression heat in terms of amount and temperature grade [13]. To make better use of the low-grade compression heat, researchers have come up with energy conversion methods, which aim to compensate for part of the electricity or cooling demand of the CASU, and to realize the self-utilization of ACS. [PERSON] et al. [14] proposed a direct binary cycle heat engine (ORC systems), which converted the waste compression heat to electricity and reduced the specific power consumption by an average of 11%. ORC has also been successfully applied in other process industries that produce waste compression heat, such as liquid air energy storage [15], combined heat and power systems [16], and oxy-combustion power plants [17]. Though they provide a valuable reference, these literature studies mainly focused on the thermodynamic characteristics of ORC itself, rather than the thermodynamic coupling principles between the ORC and the air compression process. The energy conversion from waste heat to electricity has been demonstrated to be an efficient way for energy utilization; however, some study results also show that the ORC power generation efficiency is significantly affected by the compression heat grade and its volatility [18], and may suffer from refrigerant leakage [19]. The electricity produced by ORC can also be further converted to the cooling capacity to satisfy the cooling demand of ACS. [PERSON] et al. [20; 21] investigated a cascade waste heat recovery system including dehumidification (DEH), ORC, and MR (DEH-ORC-MR), and found that 50% of the feed air humidity ratio can be decreased, which helped to increase the average isothermal efficiency of the compressors by about 5%. The waste compression heat utilization rate and energy saving rate reached 61.5% and 4.9%, respectively. Considering the possible problems caused by solute corrosion of DEH, [PERSON] et al. [22] studied an ORC-MR heat recovery system and obtained a maximum energy saving ratio of 4.2%. Thermoelectric cooling is another choice for converting electricity to the cooling capacity. Though it has advantages of being compact in size, light in weight, of high reliability,and with no mechanical moving parts, no working fluid [23; 24], it is more frequently applied for small-scale cooling demand, such as domestic and portable refrigerators [25], laboratory and scientific equipment cooling, i.e., laser diodes or integrated circuit chips [26], automobile mini-refrigerators, and thermoelectric cooler/heaters in car seats [27]. Researchers have also proposed heat-driven systems to realize the conversion of waste compression heat to cooling capacity directly. [PERSON] et al. [28] proposed a waste heat-driven vacuum fiber membrane dehumidification (VFMD) system, which improved the working condition the of compressors by dehumidifying the feed air, and recovered 55.1% of the waste compression heat. [PERSON] et al. [29] conducted a study on an absorption refrigerator (AR) with combined ACS, and found that 68.7% of the cooling water could be saved in the ACS. [PERSON] et al. [30] coupled an AR with a DEH system via a shared regenerator to achieve both the cooling and dehumidification of the suction air of the compressors. Although AR and ORC have been widely accepted and applied as effective ways to recover low-grade waste heat, their applications in the CASU are still in the proof-of-concept stage. Furthermore, as shown in Figure 1, the waste heat-driven temperature of the ORC and AR lies between 90-150 \({}^{\circ}\)C [31], while the exhaust temperature of compressed air is about 110-120 \({}^{\circ}\)C, which means that the available driven temperature is between 90-120 \({}^{\circ}\)C, leaving a larger temperature difference (at least 40-90 \({}^{\circ}\)C) for the cooling capacity. Obviously, there is a mismatch between the cooling capacity and driving heat, which has to be compensated for by intermediate heat sinks.