Salinity gradient energy (dissipated by mixing of freshwater with seawater) is currently a vast and untapped energy resource: 1 TW is believed to be realistically harvestable, representing ~40% of global electricity production. The low hanging fruit for recovery of such energy is found in coastal wastewater treatment, where large volumes of treated low-salinity wastewater are discharged to the ocean. To capture this stranded energy, we propose scale-up and commercialization of the mixing entropy battery (MEB), a simple device (membrane-free and no moving parts) invented and developed here at Stanford, containing low-cost electrodes that are alternately flushed with the two different salinity streams. In essence, the MEB is an electrical generator powered by diffusion of Na and Cl- ions into and out of electrodes accompanied by corresponding changes in the redox state of the electrode materials. Over the past few years, we (Cui and Criddle groups) have tested and identified low-cost electrodes, and have created a new operational mode that does not require any input during the device’s charging cycle. We have the IP and a lab-scale device; we now desire to build a larger demonstration system to i) increase throughput and energy density, and ii) attract investment and licensing.
Jianqiao Xu (Eng, CEE), Kristian Dubrawski (PostDoc, CEE), Prof. Yi Cui (MSE), Prof. Craig Criddle (CEE)