Driven by her concern over the rising global demand for air conditioning—which reached 2.339 million units in 2018, primarily powered by fossil-fuel-based electricity and synthetic refrigerants—Desy explored solar-based absorption chiller technology as an alternative solution that could reduce environmental impact by harnessing solar heat. This technology uses an ammonia-water solution effective for low-temperature cooling and enables easy leak detection. However, the primary challenges include the need for a large area for solar collectors and support for backup energy systems.
Motivated to address these issues, Desy developed a model for a single-stage ammonia-water absorption chiller powered by solar energy. She conducted simulations using Engineering Equation Solver (EES) and TRNSYS software to analyze the system’s performance characteristics under steady-state and transient conditions. These simulations evaluated critical parameters, such as evaporation and condensation temperatures, to optimize the system’s Coefficient of Performance (COP).
Desy’s research findings indicate that an air-cooled absorption chiller configuration offers significant savings by reducing water usage, pumps, and maintenance needs. Optimization results from her simulations showed that the highest COP (0.313) was achieved at a condensation temperature of 38°C and an evaporation temperature of 6°C. Further studies on a water heater configuration (ABS-WH) revealed that the first configuration (ABS-WH1) had the highest performance, with a maximum COP of 0.64 at a heat source temperature of 150°C. This configuration achieved optimal performance in various tropical climate conditions, especially during months with high solar radiation, such as October, where the COP increased as the hot water temperature reached 150°C.
“With Indonesia’s vast solar energy potential, my research on absorption chillers serves as an energy-efficient and eco-friendly alternative. I hope this research encourages the broader adoption of renewable energy-based cooling technology to support global efforts in reducing the carbon footprint in the air conditioning sector,” said Desy.
The Dean of FTUI, Prof. Dr. Heri Hermansyah, ST., M.Eng., IPU, commented on the research, stating, “Desy’s work not only demonstrates a deep understanding of modern thermal technology but also contributes to supporting energy and environmental sustainability agendas, highly relevant amidst the global challenges of climate change. This initiative is significant as it offers concrete solutions for reducing carbon emissions and optimizing renewable energy sources, particularly solar energy, abundant in Indonesia.”
Thanks to her research, I Gusti Agung Ayu Desy Wulandari graduated with a doctorate, a GPA of 4.00, and the honour of Cum Laude. She became the 110th doctoral graduate from the Department of Mechanical Engineering and the 570th doctoral graduate at FTUI. The Doctoral Promotion Session was chaired by Prof. Dr. Ir. Yanuar, M.Eng., M.Sc., with her Promoter, Prof. Dr.-Ing. Ir. Nasruddin, M.Eng., and Co-Promoter, Dr. Eng. Arnas, S.T., M.T. The examining committee included Prof. Dr.-Ing. Ir. Nandy Setiadi Djaya Putra, Haolia Rahman, Ph.D., Prof. Dr. Ir. Muhammad Idrus Alhamid, Dr. Ir. Budihardjo, Dipl.-Ing., and Ir. Ardiyansyah, S.T., M.Eng., Ph.D.
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