Energetic, exergetic, environmental, and economic—4E analysis of an absorption refrigeration system operated by parabolic trough collectors

In search of ensuring the sustainability of current processes and the mitigation of the issues related to the high consumption of fossil fuels, different sectors of the global economy have decided to employ alternative methods and technologies to meet the demand and energy needs in their different applications and end uses. Among these end uses, cooling systems stand out, specifically in absorption or adsorption systems, where a thermal energy source is required for the operation of this type of system. At present, natural gas is mainly used worldwide as fuel for this type of process. As a result of the operation of this type of systems, in addition to the consumption of fossil fuel, an environmental impact generated by the pollutants produced in the combustion of natural gas is obtained. For this study, we developed the analysis of function of an absorption refrigeration system coupled to a parabolic trough system working with different heat transfer fluids (HTFs) as an option to replace the consumption of natural gas and the effect generated on the environment. For the development of this study, first, the opto-geometric model of the collector system was developed, with the purpose of determining the thermal behavior. Afterward, the operation of the refrigeration system was characterized in order to complete the energy states in each component of the system. With these models, the exergy levels and components with the highest energy destruction in each system were determined. Finally, the solar field configuration was determined to supply the thermal energy required by an absorption system installed at the Universidad Tecnológica de Bolivar (UTB) and thus the environmental impacts generated by the operation of the cooling system in the actual configuration of the UTB. From the results obtained, it was determined that for the parabolic trough collectors, the efficiencies are around 70%; for temperatures of 100°C, the exergy efficiency is 12%. For the different HTFs, water and supercritical CO2 presented the best efficiencies for the evaluated conditions of the cooling system, which was defined for a cooling load capacity of 369.3 kW, which corresponds to the absorption cooling system of the UTB Auditorium.