A researcher from Saudi Arabia's University of Ha'il has conducted an exergy and energy analysis of a PV-driven single-effect absorption cooling system (SEAC) that uses water-lithium bromide (H₂O–LiBr) as the working fluid pair.
The working fluid pair is a central part of a SEAC, using heat instead of electricity to create cooling. “Low-pressure refrigerant vapor is released from the evaporator and is then absorbed by the absorber's liquid strong solution,” explained researcher Naif Khalaf AlShammari. “After that, the pump gathers the absorber's low-pressure liquid weak solution, raises its pressure, and transports it to the generator. Refrigerant vapor escapes from the weak solution in the generator due to the heat from a high-temperature source. The solutions heat exchanger cools the solutions returning from the generator to the absorber and heats the cool solutions leaving the absorber and traveling to the generator.”
The system was analyzed under the environmental conditions of Riyadh, the capital of Saudi Arabia. The absorption system was divided into 18 levels, with exergy and exergy rates calculated for each state using empirical equations and input parameters. The system's parts are an absorber, an evaporator, a generator, a condenser, a heat exchanger, a pump, and two expansion valves.
An engineering equation solver (EES) software was utilized to execute the simulation, accounting for the thermo-physical characteristics of the fluids employed in the procedure. “Thermodynamics' first and second laws, along with the conservation of mass principle, are applied to every system component in the thermodynamic investigation of the absorption system,” said the researchers. “With regard to heat transmission, inlet and exit flows, and working interaction, each element functions as a control volume.”
Image: University of Ha’il, Journal of Engineering Research, CC BY 4.0
Results of the simulation revealed that lowering absorber temperatures enhances the coefficient of performance (COP) and exergy efficiency. More specifically, optimal generator performance peaks at 80 C, as they balance COP and exergy efficiency, with levels ranging from 0.52–0.78 and 0.11–0.68, respectively.
“Exergy destruction is dominated by the generator (52% of total losses), followed by the absorber and condenser, underscoring the need for targeted component optimization,” the results showed. “Furthermore, rising ambient temperatures (25–50 C) slightly reduce COP but improve exergy efficiency, highlighting trade-offs between first- and second-law performance.”
Concluding the paper, AlShammari said that “by bridging the gap between theoretical analysis and practical application, this study contributes to the development of efficient, scalable, and environmentally friendly cooling systems, offering a pathway for reducing reliance on conventional vapor compression systems and advancing the adoption of renewable energy-driven technologies.”
The results were presented in “An examination of the exergy and energy of a solar-powered absorption cooling systems in the Riyadh climate,” published in the Journal of Engineering Research.
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