Abstract Waste heat from Air Conditioning (AC) systems has long been neglected as a heat source for power generation. With the increasing AC demand worldwide, relevant technology development are urgently required. In this study, four different combined systems have been proposed for AC waste heat conversion. Power generation modules are based on organic Rankine cycle (ORC), organic flash cycle (OFC), Kalina cycle (KCS) and transcritical CO2 cycle (T-CO2), respectively. Each of the above is integrated with a basic AC cycle to establish a combined system. Modelling studies have been carried out to evaluate the performance of the systems and it is found that an ORC-based system has a higher system performance than others throughout the entire AC condensing temperature range considered, and it results in an overall COP enhancement between 15% and 30%. The exergy analysis shows that the relatively low performance of the KCS, OFC or T-CO2-based systems is due to the higher irreversibility in the evaporator. By replacing the ORC module with a dual-pressure ORC counterpart and installing a liquid-line/suction-line heat exchanger in the AC cycle, a further COP enhancement up to 15% is achieved. Preliminary economic analysis indicates that employment of the heat recovery module becomes viable as the system cooling capacity is over 1000 kW and a payback period less than 5 years is expected.

中文翻译：

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空调余热发电循环回收热力学及可行性分析

摘要 空调 (AC) 系统的废热作为发电热源长期以来一直被忽视。随着全球交流需求的不断增加，迫切需要相关技术的发展。在这项研究中，已经提出了四种不同的组合系统用于交流废热转换。发电模块分别基于有机朗肯循环（ORC）、有机闪蒸循环（OFC）、卡林纳循环（KCS）和跨临界二氧化碳循环（T-CO2）。以上每一个都与一个基本的交流循环相结合，以建立一个组合系统。已进行建模研究以评估系统的性能，发现基于 ORC 的系统在所考虑的整个 AC 冷凝温度范围内具有比其他系统更高的系统性能，并导致整体 COP 提高 15%和 30%。火用分析表明，基于 KCS、OFC 或 T-CO2 的系统性能相对较低是由于蒸发器的不可逆性较高。通过用双压 ORC 对应物替换 ORC 模块并在 AC 循环中安装液体管路/吸入管路热交换器，可进一步将 COP 提高高达 15%。初步经济分析表明，由于系统冷却能力超过 1000 千瓦，并且预计投资回收期不到 5 年，因此热回收模块的使用变得可行。实现了高达 15% 的进一步 COP 增强。初步经济分析表明，当系统冷却能力超过 1000 kW 且预计投资回收期少于 5 年时，热回收模块的使用变得可行。实现了高达 15% 的进一步 COP 增强。初步经济分析表明，由于系统冷却能力超过 1000 千瓦，并且预计投资回收期不到 5 年，因此热回收模块的使用变得可行。