A	the effective area of a single membrane (m2)
a c	the activity of the concentrated salt solution (mol·L−1)
a d	the activity of the diluted salt solution (mol·L−1)
AEM	anion exchange membrane
b	compartment width (cm)
C c	the concentration of HC (mol·L−1)
C d	the concentration of LC (mol·L−1)
CEM	cation exchange membrane
d c	the thickness of HCC (cm)
d d	the thickness of LCC (cm)
F	Faraday constant (96485 C·mol−1)
HCC	high salt concentration compartment
I	current (A)
LCC	low salt concentration compartment
N	number of cell pairs for RED
OCV	open circuit voltage (V)
P	output power (W)
P gross	maximum gross power density (W·m−2)
P max	maximum output power (W)
P net	net power density (W·m−2)
P pump	power density consumed on pumping (W·m−2)
Q	volumetric flow rate (mL·min−1)
Q c	the volumetric flow rate of HC (L·s−1)
Q d	volumetric flow rate of LC (L s−1)
R	gas constant (8.314 J·mol−1·K−1)
R a	the area resistance of anion exchange membrane (Ω·m2)
R BL	boundary layer resistance (Ω)
R c	the area resistance of cation exchange membrane (Ω·m2)
R el	the resistance of electrodes (Ω)
R load	load resistance (Ω)
R ohmic	ohmic resistance (Ω)
R stack	stack resistance (Ω)
R △C	concentration difference resistance (Ω)
RED	reverse electrodialysis
SGP	salinity gradient power
T	absolute temperature (K)
U	voltage output
V	line flow velocity (cm·min−1)
z	electrochemical valence
α AEM	permselectivity of the anion exchange membrane
α CEM	permselectivity of the cation exchange membrane
δ	spacer thickness (cm)
ε sp	spacer porosity
κ c	the specific conductivity of the concentrated solution (mS·cm−1)
κ d	the specific conductivity of the diluted solution (mS·cm−1)
∆pc	the pressure drops along HC (KPa)
∆pd	the pressure drops along LC (KPa)