Electrokinetic streaming power generation using squeezing liquid flows in slit channels with wall slip

Electrical power generation via squeezing liquid motion is theoretically analyzed. Instead of squeezing discrete liquid droplets as extensively investigated in recent literature, we consider extracting the electrokinetic energy resulting from the streaming potential/current phenomenon by squeezing continuous liquid flows in an arbitrary number of slit channels arranged in parallel with an external load resistance and subjected to wall boundary slip. Analytical solutions to the instantaneous energy conversion efficiency, load current, and squeezing force and speed are derived assuming quasi-static, unidirectional flow conditions for the two squeezing modes of constant squeezing speed and force. Electrokinetic energy conversion efficiencies predicted by our present linear analysis for the two squeezing modes are found to be mathematically the same despite the drastic differences found in the load current and squeezing force-speed responses between the two modes. Parametric studies reveal that energy conversion efficiencies above 30% can be attained by introducing boundary slip, and that the value of the external load resistance at which the energy conversion efficiency approaches to maximum varies with respect to variations in the slip length, number of slit channels, and the slit channel geometry. Depending on the parametric conditions given, the electrokinetic energy conversion efficiency can either be increased or decreased as the separation distance between the slit channel parallel plates is reduced over the duration of the squeezing motion. Conversion efficiencies are also discussed in terms of the Debye parameter, liquid conductivity, and surface conductance for the electrokinetic power generator considered herein. © 2016 Elsevier B.V.