Towards Improved Efficiency of Low-Grade Solar Thermal Cooling: An RSM-Based Multi-Objective Optimization Study

Identifier:  imarina:9475705

Handle: https://hdl.handle.net/20.500.11797/imarina9475705

Authors:  Saoud, A; Bruno, JC

Abstract:
Featured Application The proposed low-grade solar thermal absorption chiller provides a sustainable cooling solution for residential and commercial buildings in sun-rich regions. By operating efficiently at low driving temperatures achievable with evacuated flat plate collectors, the system reduces electricity consumption from conventional vapor compression systems and lowers greenhouse gas emissions. Its optimized design offers a cost-effective pathway for integrating renewable energy into HVAC applications, particularly in hot climates where cooling demand coincides with peak solar availability.Abstract This study investigates an integrated solar-driven single-effect H2O-LiBr absorption chiller powered by low-grade thermal energy. A detailed thermodynamic model, comprising a solar collector, a thermal storage tank, and an absorption cycle, was developed using the Engineering Equation Solver (EES) software V10.561. A comprehensive parametric analysis and multi-objective optimization were then conducted to enhance both the energy and exergy performance of the system. The Response Surface Methodology (RSM), based on the Box-Behnken Design, was employed to develop regression models validated through analysis of variance (ANOVA). The generator temperature (78-86 degrees C), evaporator temperature (2.5-6.5 degrees C), and absorber/condenser temperature (30-40 degrees C) were selected as key variables. According to the results, the single-objective analyses revealed maximum values of COP = 0.8065, cooling capacity = 20.72 kW, and exergy efficiency = 39.29%. Subsequently, the multi-objective RSM optimization produced a balanced global optimum with COP = 0.797, cooling capacity = 20.68 kW, and exergy efficiency = 36.93%, achieved under optimal operating conditions of 78 degrees C generator temperature, 6.5 degrees C evaporator temperature, and 30 degrees C absorber/condenser temperature. The obtained results confirm the significance of the proposed low-grade solar absorption chiller, demonstrating comparable or superior performance to recent studies (e.g., COP approximate to 0.75-0.80 and approximate to 35-37%). This agreement validates the RSM-based optimization approach and confirms the system's suitability for sustainable cooling applications in low-temperature solar environments.