0
research-article

Harvesting Natural Salinity Gradient Energy for Hydrogen Production Through Reverse Electrodialysis (RED) Power Generation

[+] Author and Article Information
Mohammadreza Nazemi

Graduate Research Assistant, Student Member of ASME Department of Mechanical Engineering Georgia Institute of Technology Atlanta, Georgia 30332-0405
mrnazemi@gatech.edu

Jiankai Zhang

Graduate Research Assistant, Student Member of ASME Department of Mechanical Engineering Georgia Institute of Technology Atlanta, Georgia 30332-0405
jzhang794@gatech.edu

Marta C. Hatzell

Assistant Professor, Member of ASME Department of Mechanical Engineering Georgia Institute of Technology Atlanta, Georgia 30332-0405
marta.hatzell@me.gatech.edu

1Corresponding author.

ASME doi:10.1115/1.4035835 History: Received November 17, 2016; Revised January 15, 2017

Abstract

There is an enormous potential for energy generation from the mixing of sea and river water at global estuaries. Here we present a novel approach to convert this source of energy directly into hydrogen and electricity using Reverse electrodialysis (RED). RED relies on converting ionic current to electric current using multiple membranes and redox based electrodes. A thermodynamic model for RED is created to evaluate the electricity and hydrogen which can be extracted from natural mixing processes. With equal volume of high and low concentration solutions (1L), the maximum energy extracted per volume of solution mixed, occurred when the number of membranes is reduced, with the lowest number tested here being 5 membrane pairs. At this operating point, 0.32 kWh/m3 extracted as electrical energy and 0.95 kWh/m3 as hydrogen energy. This corresponded to an electrical energy conversion efficiency of 15%, a hydrogen energy efficiency of 35% and therefore a total mixing energy efficiency of nearly 50%. As the number of membrane pairs increases from 5 to 20, the hydrogen power density decreases from 13.6 W/m2 to 2.4 W/m2 at optimum external load. In contrast, the electrical power density increases from 0.84 W/m2 to 2.2 W/m2. Optimum operation of RED depends significantly on the external load (external device). A small load will increase hydrogen energy while decreasing electrical energy. This trade-off is critical in RED optimization for both hydrogen and electricity generation.

Copyright (c) 2017 by ASME
Your Session has timed out. Please sign back in to continue.

References

Figures

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In