Environmental and energy comparative analysis of expediency of heat-driven and electrically-driven refrigerators for air conditioning application
Olga Khliyeva, Kostyantyn Shestopalov, Volodymyr Ierin, Vitaly Zhelezny, Guangming Chen, Neng Gao
Abstract
The refrigeration industry is responsible for a sizable contribution to greenhouse gas emission. Heat-driven refrigerators are often declared “environmental-friendly” vs electrically-driven ones, but for each specific operating condition and application, this statement needs to be confirmed. The modified approach of the eco-energy analysis is proposed to apply to these purposes. Its novelty consists in modifying the existing environmental life cycle metrics by considering the CO2 emission from human labor (which provides the workers with goods and services) during refrigerator maintenance and the emission during the manufacturing of the power-intensive components of the refrigerator. A comprehensive analysis of the heat-driven absorption (AS) and ejector (ES) refrigerators, as well as the electrically-driven vapor compression (VCS) refrigerators, to assess the practicability of the waste heat utilization for the artificial cold production, was performed within proposed metrics. It was shown that the value of specific life cycle CO2 emission per 1 kW h of cooling energy emrefr for analyzed systems depends greatly on national environmental and energy indicators and varies from (1.29 ± 0.047)∙10−5 for France to (15.07 ± 0.57)∙10−5 (kg CO2) kJ−1 for India for VCS. The application of ES and AS vs VCS is preferable in terms ofemrefr. For example, for France emrefr=(0.526 ± 0.032)∙10−5 for ES, (0.413 ± 0.025)∙10−5 for AS, and (1.29 ± 0.047)∙10−5 (kg CO2) kJ−1 for VCR. The utilization of low-grade heat with its increased energy potential from 55 to 100 °C by additional energy resources is appropriate for heat-driven machines in terms of reduction of emrefr value only for countries with low national electricity emission factor. For example, for France for ES when the heat is produced by natural gas combustion emrefr =(34.44 ± 2.26)∙10−5 vs emrefr =(4.46 ± 0.26)∙10−5 (kg CO2) kJ−1 when heat is produced by the use of additional energy resources; analogously for India emrefr = (38.69 ± 2.27)∙10−5 vs (52.64 ± 3.20)∙10−5 (kg CO2) kJ−1. Emission from human labor makes a significant (up to 20 %) contribution to theemrefr. The practical applicability of the proposed metric of emrefr consists of simply collecting the initial data, also it is open source, and can be easily extended to the analysis of various refrigeration as well as heat-power systems.