A Self-Adaptive-Step-Size Incremental-Resistance-MPPT Technique for Reverse-Electrodialysis System

Salinity gradient power (SGP) is a kind of promising renewable energy source with huge potential, which can be derived through reverse electrodialysis (RED). Generally, RED stacks operate at either continuous mode or recycle mode, both of which possess respective advantages in different application scenes. Since SGP technology is still at an infant stage, there is a few research focusing on maximum-power-point-tracking (MPPT) techniques of RED stacks, which are crucial for the effective energy utilization of SGP. In this article, based on the generalized hybrid RED model, a self-adaptive-step-size incremental-resistance MPPT technique is proposed to extract maximum power from RED stacks. Not only is it simple and easy to implement but also it realizes self-adjustment of the step size to strike a balance between fast dynamic responses and small oscillations at a steady state. Moreover, according to the unique intrinsic features of RED stacks, the systematic design principles of the sampling interval and scaling factor are detailed, which help facilitate a fast and stable system. Various tests with the proposed technique under different parameter settings, as well as tests with other conventional MPPT techniques, are conducted on a RED stack prototype to validate the effectiveness of the proposed MPPT.