Thermal energy
The solar humidification–dehumidification (HDH) process (also called the multiple-effect humidification–dehumidification process, solar multistage condensation evaporation cycle (SMCEC) or multiple-effect humidification (MEH) mimics the natural water cycle on a shorter time frame by distilling water. Thermal energy produces water vapor that is condensed in a separate chamber. In sophisticated systems, waste heat is minimized by collecting the heat from the condensing water vapor and pre-heating the incoming water source.