Unifying Efficiency\nMetrics for Solar Evaporation\nand Thermal Desalination

Worsening water crises and climate change drive the need\nfor solar\nevaporation and thermal desalination. Yet, diverse performance metrics,\nsiloed communities, and a research shift away from high-efficiency\ntechnologies pose challenges to their advancement. We present a thermodynamic\nframework for unifying performance measurements across technologies,\ncategorizing 17 leading performance metrics by their local- or system-level\napplication and by thermodynamics laws. These are then organized into\nfour categories of conceptually equivalent “sister”\nmetrics. We clarify their best applications and measurement methods,\ndetailing old and new conversion techniques using the temperature,\nrecovery ratio, and salinity. Additionally, we compare six leading\nsolar evaporation and thermal desalination technologies, identifying\ntheir second law efficiency and the specific exergy consumption. Furthermore,\nwe reveal the unifying role of least work for solar desalination and\nsteam generators and identify that many first law metrics become identical\nin these processes. Additionally, we create contour plots that link\nthe energy efficiency metrics, recovery ratio, salinity, and temperature\nacross a wider range than previously modeled, providing intuitive\nand easy comparisons and efficiency calculations. These findings contribute\nto enhancing comparisons and expediting optimal technology development.