Solar-Thermal Energy Harvesting to Achieve Water Desalination

Harnessing solar energy to desalinate water is a critical need in many areas of the world where water supplies are scarce, or in regions affected by natural disasters. To address this problem, we developed a novel small-scale solar-thermal energy harvesting scheme to rapidly heat water to boiling, enabling distillation, water desalination, and generation of potable water.<br/>We performed outdoor experiments demonstrating that concentrated solar power can heat water to boiling effectively and achieve desalinate water on a small scale. Using a 1.5 m dish shaped mirror to concentrate solar energy on a flask of water we achieved boiling of water within 1 hour. To accelerate the solar-thermal energy harvesting process we compare the performance of absorbing carbon-black coatings on glass flasks with uncoated flasks. We discuss the use of photonic structures that enhance thermal emission in relevant wavelength windows and describe preliminary measurements with these structures.<br/>We measured the conductivity (s) and concentration of total dissolved solids (TDS) in the starting water solution to be 4.32 milli-S/cm and 2.2 ppt respectively and found that these decreased to 20 micro-S/cm and 10 ppm in the distillate achieved with solar-thermal energy conversion, illustrating excellent desalination. To calibrate the outdoor solar-thermal energy conversion results we performed baseline indoor water distillation experiments. We found that the decreases of conductivity and TDS are in outdoor experiments are comparable with those achieved in benchmark indoor distillation experiments. We discuss pathways for scale-up of solar-thermal energy harvesting and water desalination to larger scales. The critical thermal transport processes will be described.<br/>The work was partially supported by Iowa State University through the ECpE FuTure Grant and the ISU Honors program.