Hybrid Solar Desalination to Produce Fresh Water, Electrical Power With Energy Storage

The numerical analysis of solar desalination processes in a unique tray was extended to include an RED device to produce electricity either during operation or using the stored concentrated salt mixture. The motivation for this using device was based on an exergy analysis and the second law efficiency. Previous analysis illustrated how the exergy analysis could be used to identify the irreversibilities in the system and indicated modifications to increase the performance of the tray design desalinator for the sensible energy content of the discharge. The exergy related to the higher concentration level of the discharge is now investigated for a RED device. These analyses are extended to investigate the potential of using the higher salinity of the out flowing brine to produce electrical energy by using the reversed electrodialysis (RED) process. The RED process which converts 70–80% of the change in Gibbs energy to electricity uses the concentrated brine to produce electrical power while the freshwater is being produced. The analysis demonstrates it is possible to produce a maximum electrical output of 0.32 kJ/kg for the expected concentration differences. Using the predicted mass flow over the day of 6 kg/(day m²) it is expected that one could produce approximately 1.9 kJ/(day m²) of electricity in addition to the freshwater production.