Application of multi-objective optimization based on Sobol sensitivity analysis in solar single-double-effect LiBr−H2O absorption refrigeration
image: Schematic diagram of solar single-double-effect LiBr−H2O ARS
Credit: Shiqi Zhao, Qingyang Li, Yongchao Sun, Dechang Wang, Qinglu Song, Sai Zhou, Jinping Li & Yanhui Li.
Solar energy offers a promising solution for clean cooling, particularly through absorption refrigeration systems (ARS). However, the intermittent nature of solar radiation and the limited adaptability of conventional systems to varying heat source temperatures pose significant challenges to efficiency and widespread adoption. Single-effect absorption chillers operate at lower temperatures but with lower performance, while double-effect chillers offer higher efficiency but require higher driving temperatures, which are not always consistently available from solar sources. Improving both solar energy utilization and economic viability remains a critical research focus.
A research team from Qingdao University and Lanzhou University of Technology, led by corresponding authors Dechang Wang and Qinglu Song, has published a study in Frontiers in Energy titled "Application of multi-objective optimization based on Sobol sensitivity analysis in solar single-double-effect LiBr–H2O absorption refrigeration."
The study introduces a novel solar-driven single-double-effect LiBr–H2O ARS that can switch operation modes based on solar irradiance levels. Its key innovation lies in applying a multi-objective optimization framework integrating Sobol global sensitivity analysis and the NSGA-II algorithm to simultaneously maximize the solar fraction (SF) and minimize the levelized annual cost, addressing a common trade-off in solar system design.
The system was modeled and simulated under Qingdao weather conditions. Without an auxiliary heater, it provided an average daily cooling duration of approximately 8.5 hours. With an auxiliary heater, the initial SF reached 59.29%. Sobol analysis identified that collector area significantly impacted SF, whereas tank volume and pump flowrate had minor effects. Eleven key parameters, including collector area and various fluid flowrates and temperatures, were selected for optimization.
After optimization using NSGA-II, the system achieved a 3.22% increase in SF and a 10.18% reduction in levelized cost. Compared to a standard solar single-effect system, the optimized single-double-effect system showed a 17.42% higher SF. Additionally, the daily cooling capacity per unit collector area increased by 10.5%, and CO2 emissions were reduced by 8.29%.
This work demonstrates that combining a mode-switching single-double-effect absorption chiller with a systematic optimization strategy can significantly enhance both the solar energy utilization and economic performance of solar cooling systems. The methodology provides a practical approach to designing more efficient and cost-effective solar refrigeration systems, contributing to reduced primary energy consumption and lower operational costs without overstating performance beyond the studied conditions.
Original source:https://link.springer.com/article/10.1007/s11708-024-0938-4
https://journal.hep.com.cn/fie/EN/1159579523324895622
Sharable link: https://rdcu.be/eQ1Nh