Eco-Friendly Desalination under Tropical Conditions Using Low-Grade Heat on Indonesian Seawater

¹ Department of Mechanical Engineering, Faculty of Engineering, Universitas Sumatera Utara, 20155 Medan, Indonesia
² Department of Mechanical Engineering, Faculty of Engineering, Bursa Uludag University, 16059 Bursa, Türkiye
³ Department of Mechanical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, 16424 West Java, Indonesia
⁴ Department of Mechanical Engineering, National Cheng Kung University (NCKU), Tainan, Taiwan
⁵ Department of Mechanical Engineering, Politeknik Negeri Sriwijaya, Palembang 30139, South Sumatera, Indonesia

^* Corresponding author: ahmadzikri@usu. ac.id

Abstract

Global freshwater shortage and growing energy consumption underscore the demand for emerging environmentally friendly and energy-efficient desalination technologies. The United Nations World Water Development Report predicts that almost six billion people will face water scarcity by 2050. Being the world's largest archipelagic country, Indonesia has a wide range of issues in supplying clean freshwater especially in small islands and remote coastal areas where the availability of groundwater is overwhelmingly limited and threatened with seawater intrusion and seasonal variation. Although desalination presents a promising solution, conventional systems remain highly energy-intensive. This study investigates a renewable, eco-friendly vacuum thermal desalination system that integrates a throttling process with a cyclone separator at the pilot scale. A thermodynamic simulation is conducted to evaluate the influence of heat source temperature (34-90 °C) and post-throttling vacuum pressure (0.7-3.4 kPa) on system performance, expressed in terms of Specific Aquadest Production (SAP) and Specific Energy Consumption (SEC). The results show that SAP increases nearly linearly with heat source temperature, ranging from 0.014 to 0.148 kg/s, with lower vacuum pressures consistently producing higher yields. Meanwhile, SEC values remain within 0.05-0.15 kJ/kg (equivalent to 0.014-0.042 kWh/m³), indicating competitive energy performance compared to conventional thermal desalination systems. These findings support the potential of portable, energy-efficient, and eco-friendly desalination technologies to address freshwater scarcity in tropical island communities such as those in Indonesia.