Iraqi Journal of Chemical and Petroleum Engineering 

 Vol.12 No.4 (December 2011) 1- 4 

ISSN: 1997-4884 

 

 

 

 

Energy Generation from Static Water Head Developed  

By Forward Osmosis 

 
Adel A. Al-Hemiri, Ghazwan A. Mohammed

 
 and Ghazi F. Naser 

 

Department of Chemical Engineering, Baghdad University, Baghdad, Iraq 

 

 

In this work, the possibility of utilizing osmosis phenomenon to produce energy as a 

type of the renewable energy using Thin Film Composite Ultra Low Pressure 

membrane TFC-ULP was studied. Where by forward osmosis water passes through 

the membrane toward the concentrated brine solution, this will lead to raise the head 

of the high brine solution. This developed static head may be used to produce energy. 

The aim of the present work is to study the static head developed and the flux on the 

high brine water solution side when using forward and reverse osmosis membranes 

for an initial concentration range from 35-300 g/l for each type of membrane used at 

room temperature and pressure conditions, and finally calculating the maximum 

possible power generated from developed static head. 
 

Introduction 
   Osmosis a physical phenomenon 

extensively studied by scientists in 

various disciplines of science and 

engineering. Early researchers studied 

the mechanism of osmosis through 

natural materials, and from the 1960s, 

special attention was given to osmosis 

through synthetic materials. 

Osmotically driven membrane 

processes utilize an osmotic pressure 

difference, which is generated when a 

semi-permeable membrane separates a 

dilute feed solution from a more 

concentrated draw solution, to drive 

the permeation of water from the feed 

solution to the draw solution. These 

processes have the potential to 

sustainable produce clean drinking 

water or electric power [1]. Forward 

osmosis (FO), a subset of osmotically 

driven membrane processes is 

appealing because it requires no 

applied hydraulic pressure and has a 

low membrane fouling propensity [2]. 

Because of these benefits, FO is 

attracting attention as a new 

technology to augment water supplies 

using non-traditional sources. The 

potential of this technology was 

demonstrated in a variety of 

applications, such as desalination [3, 

4],     wastewater reclamation [5, 6], 

industrial wastewater treatment [7], 

brine concentration [8], osmotic 

membrane bioreactors [9], liquid food 

processing [10, 11], and protein 

concentration [12]. Renewable energy 

can be extracted wherever two streams 

of different salinity or different 

chemical potential meet. Considering 

that the salinity of seawater yields 

osmotic pressures of approximately 

2.7MPa and that the osmotic pressure 

of river water is relatively 

insignificant, a large portion of the 

2.7MPa can be used for power 

generation. The Pressure-Retarded 

Iraqi Journal of Chemical and 

Petroleum Engineering 

 

University of Baghdad 

College of Engineering 



Energy Generation from Static Water Head Developed By Forward Osmosis 

 

 

  

2                                       IJCPE Vol.12 No.4 (December 2011)         Available online at: www.iasj.net  

 
 

Osmosis (PRO) is one method that can 

be used to realize this energy. PRO is 

preferred for Osmotic hydropower 

generation and is a similar 

phenomenon to FO but with applying a 

pressure on the brine solution side 

lower than its osmotic pressure, so that 

PRO will act in conditions between 

those of FO and RO. PRO for power 

generation has been continuously 

studied by Loeb and co-workers [13]. 

Additionally intensive studies funded 

by the European union with the main 

objective being to develop membranes 

for PRO power that have a production 

capacity equivalent to at least 4 W/m² 

[14]. 

 

Experimental Section 
Studied Variables In the present work the 

variables taken into consideration are 

classified into categories according to 

system arrangements made. The 

arrangements are: type of membrane, FO 

and RO membranes and the effect of initial 

concentration of the brine solution in the 

brine solution side. 35,100,165.230 and 

300 g / l. 

Experimental Apparatus. The apparatus 

consists of the following parts: (1) Two 

glass vessels type QVF 15 cm in diameter 

with 3.5 l capacity. One vessel contains 

the brine solution and the other contains 

water. (2) Two membranes type RO and 

FO. One of the membranes is placed 

between the two glass vessels; the active 

layer will face the vessel holding the brine 

solution. The glass vessels and the 

membrane are assembled with two flanges 

and a silicone seal. (3) A glass pipe type 

QVF with a length of 2m and diameter of 

1.8 cm is connected on the brine solution 

vessel to measure the hydraulic head. (4) 

A glass L shaped fitting type QVF 

connected to a rubber hose which will 

collect the liquid from the brine solution 

side into a graduated glass cylinder to 

measure the permeate flux. Figure 1 shows 

a simple sketch of the apparatus used. 

 

 
Fig .1, Apparatus used in present study 

 

Hydraulic Head Measurements. The 
measurements consist of the following 

steps: (1) Initially a brine solution was 
prepared by putting 35g NaCl in a 1 liter 

flask and completing the volume to 1 liter 

with fresh water. The conductivity of the 

solution is measured using conductivity 

meter, and then the solution was placed in 

one of the QVF vessels and with the active 

side of the membrane facing this solution. 

(2) 3.5 l of fresh water was placed in 

second QVF vessel with the non active 

side facing the fresh water. The 

conductivity of the fresh water was 

measured. (3) The value of the hydraulic 

head was recorded with time in one hour 

intervals. This operation is repeated many 

times using the FO and RO membranes for 

initial brine concentrations range of 35 to 

300 g/l. 

Permeate Flux Measurements. The same 

procedure as above was repeated but for 

measuring the permeate flux. This was 

done by collecting the overflowing volume 

of permeate in a measuring cylinder and 

recording the time for a given volume. 

 

Results and Discussion 
    Hydraulic Head Developed. The 

hydraulic head developed when using the 

FO type membrane is greater than that 

obtained when using RO type membrane 

as shown in table 1 below which  lists the 

head developed ( H ) per unit area of 

membrane after 24 h for initial brine 

concentration ( C ) from 35 to 300 g / L 

using RO and FO membranes. 

 

 

 

 

 



Adel A. Al-Hemiri, Ghazwan A. Mohammed
 
 and Ghazi F. Naser 

  

 

Available online at: www.iasj.net                IJCPE Vol.12 No.4 (December 2011)                                 3 
 
 

Table 1,  Head developed (H) at different 

initial brine concentration (C) Using RO 

and FO membranes after 24 h at room 

conditions [15]. 

 

The relation between the initial brine 

concentration ( C ) and the head developed 

( H ) can be represented by the following 

proposed equation: 

H=KC
N
                                                   (1)  

Where K and N are constants that depend 

on the type of membrane used. Table 2 

below, lists the values of the constants in 

equation 1 for RO and FO membranes. 
 

Table 2, Constants of equation (1) for RO 

and FO membranes [15]. 

Membrane  RO FO 

K 0.3931 1.6437 

N 0.7687 0.5542 

R
2
 0.9915 0.9511 

 

Permeate Flux. The permeate flux ( Jw ) 
when using FO membrane is nearly double 

that when RO membrane was used as 

shown in table 3.  
 

Table 3, permeate flux ( Jw ) at different 

initial brine concentration (C) Using RO 

and FO membranes after 24 h at room 

conditions [15]. 

C  Jw ( RO ) Jw ( FO ) 

35 1.12 2.44 

100 5.82 7.18 

165 6.79 12.00 

230 7.39 13.96 

300 8.30 15.61 

g / L L / m
2
 . day L / m

2
 . day 

 

Power Generated. The maximum power   

( Pm ) obtained from the head developed 

using RO and FO membranes is equal to 

the static pressure of the head developed 

and is given by the following equation: 

  Pm=ρ.g.H                                              (2)                                           

Where ρ is the density of brine solution 

and g is the gravity of acceleration. Table 

4 lists the maximum possible power in 

Watts per unit membrane area ( W/m
2
 

)obtained using RO and FO membranes 

for initial brine concentration range from 

35 to 300 g / L. 

 

Table 4, Power generated (Pm) at different 

initial brine concentration (C) Using RO 

and FO membranes [15]. 

C  Pm ( RO ) Pm ( FO ) 

35 0.71 1.46 

100 1.51 2.00 

165 2.05 3.14 

230 3.02 3.90 

300 3.76 4.72 

g / L W / m
2
  W / m

2
  

 

Conclusions  
    The use of osmotic processes as a 

source of renewable energy is very 

promising, however, with the obtained 

results alongside the available 

literature it remains beyond achieving 

yet. 

 

Literature Cited 
1- Mi B. and Elimelech M., 

(2010),“Organic fouling of  forward 

osmosis membrane: fouling 

reversibility and cleaning without 

chemical reagents”, Journal of 

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2- Kravath R.E. and Davis J.A., (1975), 
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osmosis”, Desalination, vol.16, pp.151-

155. 

3- Cath, T.Y., Childress, A.E. and 
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100 13.30 17.65 

165 18.06 27.69 

230 26.61 34.35 

300 33.12 41.54 

g / L m / m
2
 . day m / m

2
 . day 



Energy Generation from Static Water Head Developed By Forward Osmosis 

 

 

  

4                                       IJCPE Vol.12 No.4 (December 2011)         Available online at: www.iasj.net  

 
 

5- Cath T.Y., Gormly S.,Beaudry E.G., 
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Developed by Forward and Reverse 

Osmosis”, M. Sc. Thesis, Chemical 

Engineering Department, of the 

College of Engineering, University of 

Baghdad.