Unifying Efficiency Metrics for Solar Evaporation and Thermal Desalination

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