Osmotic Power Potential Questions and Answers

By: Maher Kelada- MIK Technology- Houston, TexasDISTRIBUTION OR MODIFICATION OF THIS COPYRIGHTED DOCUMENT IS STRICTLY PROHIBITED AND PROTECTED BY UNITED STATES COPYRIGHT LAWS.1. What is the latest on the Statkraft project?2. Is U.S. scrapping plans for the proposed plant in New Orleans?3. Is the U.S. Navy has developed a process for generating power from water?4. Is the U.S. Navy power generation based on osmosis energy generation?

MIK Technology Answers1. Statkraft Osmotic Power Project Status:To the best of my knowledge, a future full-scale plant is contemplated for producing 25 MW of electricity, enough to provide power for 30,000 European households, would be as large as a football stadium and requires some 5 million square meters of membrane. Statkraft is forecasting plant completion in 2015.Membranes flux and fouling are issues, which are common problems in this field, but it appears that availability of potential energy to minimize pumping head requirements is a challenge. For example, consideration was given to build the proposed plant underground.

The attached figure was published by Statkraft earlier to depict this idea.

You may need also to refer to the attached sitehttp://newenergyandfuel.com/http:/newenergyandfuel/com/2008/12/05/osmotic-energy-potential/2. Proposed US Osmotic Plant in New Orleans:Sorry for the confusion. U.S. is not contemplating such a plant. I have postulated this example to explain the deficiency of the concept that promotes seawater-riverwater osmotic potential and the claims that this system will solve world energy crisis.I doubt if the U.S. Government acknowledges that osmotic power is an energy source.  All the grants offered by the Department of Energy deals with conventional alternative energy; solar, wind, geothermal, OTEC, etc.

3. US Navy process for generating power from waterAs reported in media, it seems that the U.S. Navy has commissioned an 8-megawatt for power and water desalination for its base on the island of Diego Garcia, in the Indian ocean. The plant is intended for energy security in this region and is based on OTEC technology (Ocean Thermal Energy Conversion) for energy security. This process relies on making the advantage of temperature difference between deep sea water and surface water (5 C -15 C), using heat engine, normally operated with ammonia as the heat transfer media. Here, when we talk energy security for the Navy fleet economics takes a back seat.Other plants are in the works as well. The U.S. Navy is exploring the feasibility of an OTEC plant for its base on Guam, a South Pacific island. Recently US has offered Lockheed Martin in September 2009 a contract for US $8 million to develop Ocean thermal energy conversion system, OTEC system components and further mature its design for an OTEC pilot plant.

4. US Navy use of osmotic powerThe electric ship vision is a new concept that is being discussed frequently in the recent years. As it appears, the US Navy is interest in modernizing their fleet by improving the fleet efficiency, less dependence on carbon-based fuel and significantly increase its electric power capability (generation and storage) to support modern armaments that rely on electric energy; lasers and others.Regarding the use of osmotic pressure, this concept is still unknown here in U.S.  In fact, I am promoting this technology and eager to establish a salinity laboratory here in the States, hopefully with collaboration with academia and foresighted investors. This is an extensive field and will definitely impact the semipermeable membrane technology and market worldwide.Hopefully soon, I will have an article discussing the “Osmotic Power Potential of the Great Salt Lake”

Few months ago, I have applied for a grant from the Navy regarding their solicitation of “New Concepts in Energy Conversion and Power Management.” It seems doubtful at this point that a grant will be awarded due to procedural issues.

In my grant application, I indicated that osmotic power is low density energy, requiring adequate space and source of energy; solar, waste, etc, that is not necessarily available on Navy attack ships such as destroyers and frigates.  However, it could be used as a land installation for the docking fleet and shipyards.  A reduced size closed type osmotic power generation can be potentially used on airplane carriers, since a large amount of waste fuel, spillage and human waste can be accumulated and used to generate steam, using a wet oxidation process.

Further, in analyzing power scenarios, it appears that four (4) GE LM2500 gas turbines are a common power generator in many of the US navy ships. Efficiency of a turbine of this kind is 37% generating useful power of 25 MW (33,600 shaft horsepower). If waste energy is not already recovered and efficiently reused, it would be prudent that the navy may consider a hybrid cogeneration power train (combined gas turbine for main propeller drive + exhaust heat boiler with steam turbine for electricity generation + electric energy storage).

Such combined system operates at relatively higher efficiency approaching 85%. This implies that at least an additional 25 MW can be recovered and stored in some storage means (batteries and capacitors) or used for driving additional electrically driven propeller(s).  In this case, only two cogeneration trains would be sufficient to meet ship propulsion power requirement. As important, this concept will insure higher efficiency, greater operation flexibility and maneuverability, as well as ample electric power for modern armaments, yet with economical service and less dependence on fossil fuels.

How are Osmotic Pressure and Power Calculated?

By: Maher Kelada- MIK Technology- Houston, Texas

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This post is in response to readers of my article, “Seawater Osmotic Salinity Power Reality.”  Without getting into many thermodynamic derivations, the combined

first and second laws of thermodynamics can be reduced in terms of Gibbs free energy to:

dG = Vdp – SdT + Σi μi dNi

Where, entropy S, volume V and substance amount N are extensive properties and temperature T, pressure p, and chemical potential μ are energy-conjugated

intensive quantities.

This relation is further reduced to give a simple mathematical relation in terms of osmotic pressure p, concentration and temperature. Osmotic pressure was

originally proposed by Nobel Laureate Van’t Hoff and modified to include Staverman’s osmotic reflection coefficient to become:

                                              Osmotic Pressure

Where:π = osmotic pressure or force imposed on the membrane given in bars, atm, psi, etc.Φ = Osmotic Reflection Coefficient (NaCl = 0.93, CaCl2 = 0.86, MgCl2= 0.89, etc.),[It is ratio of real to ideal osmotic pressures for a given membrane]I = Ions concentration per dissociated solute molecule (Na+ and Cl- ions = 2),C = molar concentration of the salt ions,

R = gas constant (0.08314472 liter· bar / (k.mol)),

T = ambient temperature in absolute Kelvin degrees (20o C +273o = 293o K).The amount of average concentration of oceans salt is about 3.5% (35 gram/liter), mostly in the form of sodium chloride (NaCl).  For simplicity of calculation, it is assumed that seawater contains 35 grams NaCl/liter. The atomic weight of sodium is 23 grams, and of chlorine is 35.5 grams, so the molecular weight of NaCl is 58.5 grams. Therefore, the number of NaCl moles in seawater is 35 / 58.5 = 0.598 mol / liter and the osmotic pressure of seawater is:

π = [0.93] [2] [0.598 mol/liter] [0.08314 liter.bar/ (k.mol)] [293 K] = 27.1 bar

Since one bar = 100,000 Pascal (Pa) and one kilogram (force) per square centimeter (kgf/cm2) = 98066.5 Pascal. Then,π = [27.1 x 105 Pa] / [98066.5 Pa / (kgf/cm2)] = 27.63 kgf/ cm2

π = [27.63 kgf/ cm2] [m/100 cm] [1000 cm3/liter] = 276.3 kgf. m/ liter1)  Sea Water Energy Potential*, SWE

SWE = [276.3 kgf. m/liter] [9.80665 Joule/ kgf. m] = 2711 Joule/liter = 2.711 MJ/m3

[The value of the osmotic pressure in bars /10 = the value of energy in MJ/m3]SWE = [2711 Joule/liter] [1 cal/ 4.184 J] [1 kcal/1000 cal] = 0.6479 kcal/literSWE = [2711 Joule/liter] [1000 liter/m3] = 2.711 MJ/m3

In case of generating power continuously (1 m3 per sec, of every hour), which is the case with power generation systems, the potential energy of this system is:SWE = [2.711 MJ/m3] [(1 m3 /sec) (3600 sec)] = 9.759 x 109 JSince 1 Watt = 1 Joule/Second

SWE = [9.759 x 109 W.s] [h /3600 s] [1 kW /1000 W] = 2711 kWh[or simply use the relation of 3.6 x 106 J = 1 kWh]SWE = [2711 kWh] [24 hrs/day] [365 days/year] = 23.75 x 106 kWh per year2) Osmotic pressure of multi-salt brine; Dead Sea water

Osmotic Pressure of Multi-Salt Solution

The author’s estimation of the Dead Sea osmotic pressure is 225 Bar.

Maher Kelada

MIK Technology

mik.technology@gmail.com

*Energy potential is a theoretical value. Realistically, the net recovered amount of the potential energy is modest, and highly dependent on salt concentration.

Please refer to MIK Technology article “Seawater Osmotic Salinity Power Reality,” posted on January 24, 2010.

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Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, or 599 mM). This means that every kilogram (roughly one litre by volume) of seawater has approximately 35 grams (1.2 oz) of dissolved salts (predominantly sodium (Na+) and chloride (Cl−) ions). Average density at the surface is 1.025 g/ml. Seawater is denser than both fresh water and pure water (density 1.0 g/ml @ 4 °C (39 °F)) because the dissolved salts add mass without contributing significantly to the volume. The freezing point of seawater decreases as salt

concentration increases. At typical salinity it freezes at about −2 °C (28 °F).[1]

 The coldest seawater ever recorded (in a liquid state) was in 2010, in a stream

under an Antarctic glacier, and measured −2.6 °C (27.3 °F).[2]

Compositional differences from freshwater

Seawater contains more dissolved ions than all types of freshwater.[7] However, the ratios of solutes differ dramatically. For instance, although seawater

contains about 2.8 times more bicarbonate than river water based on molarity, the percentage of bicarbonate in seawater as a ratio of all dissolved ions is far

lower than in river water. Bicarbonate ions also constitute 48% of river water solutes but only 0.14% of all seawater ions. [7][8] Differences like these are due to

the varying residence times of seawater solutes; sodium and chlorine have very long residence times, while calcium (vital for carbonate formation) tends to

precipitate much more quickly.[8] The most abundant dissolved ions in seawater are sodium, chloride, magnesium, sulfate and calcium.[9]

Membrane technologyFrom Wikipedia, the free encyclopedia

This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. Please help to improve this article by introducingmore

precise citations. (September 2011)

Membrane technology covers all process engineering measures for the transport of substances between

two fractions with the help of permeable membranes. In general, mechanical separation processes for

separating gaseous or liquid streams use membrane technology.

Contents

[hide]

1 Applications

2 Current market and forecast

3 Mass transfer

o 3.1 Solution-diffusion model

o 3.2 Hydrodynamic model

4 Membrane operations

5 Membrane shapes and flow geometries

6 Membrane performance and governing equations

7 Membrane separation processes

8 See also

9 Notes

10 References

[edit]Applications

Ultrafiltration for a swimming pool

Venous-arterial ECMO scheme

The particular advantage of membrane separation processes is that they operate without heating and

therefore use less energy than conventional thermal separation processes

(distillation, Sublimation or crystallization). This separation process is purely physical and because it is a

gentle process, both fractions (permeate andretentate) can be used. Therefore, cold separation by means

of membrane processes is commonly applied in the food

technology, biotechnology andpharmaceutical industries. Furthermore, with the help of membrane

separations realizeable that with thermal processes are not possible. For example,

becauseazeotropics or isomorphics crystallization making a separation by distillation

orrecrystallization impossible. Depending on the type of membrane, the selective separation of certain

individual substances or substance mixtures is possible. Important technical applications include drinking

water by reverse osmosis(worldwide approximately 7 million cubic meters annually), filtrations in the food

industry, the recovery of organic vapors such as gasoline vapor recovery and theelectrolysis for chlorine

production. But also in wastewater treatment, the membrane technology is becoming increasingly

important. With the help of UF and MF (Ultra-/Mikrofiltration) it is possible to remove particles, colloids and

macromolecules, so that wastewater can be disinfected in this way. This is needed if wastewater is

discharged into sensitive outfalls, or in swimming lakes.

About half of the market has applications in medicine. As an artificial kidney to remove toxic substances

by hemodialysis and as artificial lung for bubble-free supply of oxygen in the blood. Also the importance of

membrane technology is growing in the field of environmental protection (NanoMemPro IPPC Database).

Even in modern energy recovery techniques membranes are increasingly used, for example in the fuel

cell or the osmotic power plant.

[edit]Current market and forecast

The global demand on membrane modules was estimated at approximately 15.6 billion USD in 2012.

Driven by new developments and innovations in material science and process technologies, global

increasing demands, new applications, and others, the market is expected to grow around 8% annually in

the next years. It is forecasted to increase to 21.22 billion USD in 2016 and reach 25 billion in 2018. [1]

[edit]Mass transfer

For the mass transfer at the membrane, two basic models can be distinguished: the solution-diffusion

model and thehydrodynamic model. In real membranes, these two transport mechanisms certainly occur

side by side, especially during the ultrafiltration.

[edit]Solution-diffusion model

The transport occurs only by diffusion. The component that needs to be transported must first be dissolved

in the membrane. This principle is more important for dense membranes without natural pores such as

those used for reverse osmosis and in a fuel cell. During the filtration process a boundary layer forms on

the membrane. This concentration gradient is created bymolecules which cannot pass through the

membrane. The effect is referred as concentration polarization and, occurring during the filtration, leads to

a reduced transmembrane flow (flux). Concentration polarization is, in principle, reversible by cleaning the

membrane which results in the initial flux being almost totally restored. Using a tangential flow to the

membrane (cross-flow filtration) can also minimize concentration polarization.

[edit]Hydrodynamic model

Transport through pores – in the simplest case – is done convectively. This requires the size of the pores to

be smaller than the diameter of the to separate components. Membranes, which function according to this

principle are used mainly in micro- and ultrafiltration. They are used to

separate macromolecules from solutions, colloids from a dispersion or remove bacteria. During this

process the not passing particles or molecules are forming on the membrane a more or less a pulpy mass

(filter cake). This hampered by the blockage of the membrane the filtration. By the so-called cross-flow

method (cross-flow filtration) this can be reduced. Here, the liquid to be filtered flows along the front of the

membrane and is separated by the pressure difference between the front and back of the fractions

into retentate (the flowing concentrate) and permeate (filtrate). This creates a shear stress that cracks the

filter cake and lower the formation of fouling.

[edit]Membrane operations

According to driving force of the operation it is possible to distinguish:

pressure driven operations

microfiltration

ultrafiltration

nanofiltration

reverse osmosis

gas separation

pervaporation

concentration driven operations

dialysis

osmosis

forward osmosis

operations in electric potential gradient

electrodialysis

membrane electrolysis

electrophoresis

operations in temperature gradient

membrane distillation

[edit]Membrane shapes and flow geometries

Cross-flow geometry.

Dead-end geometry.

There are two main flow configurations of membrane processes: cross-flow and dead-end filtrations. In

cross-flow filtration the feed flow is tangential to the surface of membrane, retentate is removed from the

same side further downstream, whereas the permeate flow is tracked on the other side. In dead-end

filtration the direction of the fluid flow is normal to the membrane surface. Both flow geometries offer some

advantages and disadvantages. The dead-end membranes are relatively easy to fabricate which reduces

the cost of the separation process. The dead-end membrane separation process is easy to implement and

the process is usually cheaper than cross-flow membrane filtration. The dead-end filtration process is

usually abatch-type process, where the filtering solution is loaded (or slowly fed) into membrane device,

which then allows passage of some particles subject to the driving force. The main disadvantage of a dead

end filtration is the extensive membrane fouling andconcentration polarization. The fouling is usually

induced faster at the higher driving forces. Membrane fouling and particle retention in a feed solution also

builds up a concentration gradients and particle backflow (concentration polarization). The tangential flow

devices are more cost and labor intensive, but they are less susceptible to fouling due to the sweeping

effects and high shear rates of the passing flow. The most commonly used synthetic membrane devices

(modules) are flat plates, spiral wounds, and hollow fibers.

Flat plates are usually constructed as circular thin flat membrane surfaces to be used in dead-end

geometry modules. Spiral wounds are constructed from similar flat membranes but in a form of a “pocket”

containing two membrane sheets separated by a highly porous support plate.[2] Several such pockets are

then wound around a tube to create a tangential flow geometry and to reduce membrane fouling.

Hollow fiber modules consist of an assembly of self-supporting fibers with a dense skin separation layers,

and more open matrix helping to withstand pressure gradients and maintain structural integrity.[2] The

hollow fiber modules can contain up to 10,000 fibers ranging from 200 to 2500 μm in diameter; The main

advantage of hollow fiber modules is very large surface area within an enclosed volume, increasing the

efficiency of the separation process.

Spiral wound membrane module.

Hollow fiber membrane module.

 

Separation of air in oxygen and nitrogen through a membrane

[edit]Membrane performance and governing equations

The selection of synthetic membranes for a targeted separation process is usually based on few

requirements. Membranes have to provide enough mass transfer area to process large amounts of feed

stream. The selected membrane has to have highselectivity (rejection[disambiguation needed]) properties for certain

particles; it has to resist fouling and to have high mechanical stability. It also needs to be reproducible and

to have low manufacturing costs. The main modeling equation for the dead-end filtration at

constant pressure drop is represented by Darcy’s law:[2]

where Vp and Q are the volume of the permeate and its volumetric flow rate respectively (proportional to

same characteristics of the feed flow), μ is dynamic viscosity of permeating fluid, A is membrane area,

Rm and R are the respective resistances of membrane and growing deposit of the foulants. Rm can be

interpreted as a membrane resistance to the solvent (water) permeation. This resistance is a

membrane intrinsic property and expected to be fairly constant and independent of the driving force, Δp. R

is related to the type of membrane foulant, its concentration in the filtering solution, and the nature of

foulant-membrane interactions. Darcy’s law allows to calculate the membrane area for a targeted

separation at given conditions. Thesolute sieving coefficient is defined by the equation:[2]

where Cf and Cp are the solute concentrations in feed and permeate respectively. Hydraulic permeability is

defined as the inverse of resistance and is represented by the equation:[2]

where J is the permeate flux which is the volumetric flow rate per unit of membrane area. The solute

sieving coefficient and hydraulic permeability allow the quick assessment of the synthetic membrane

performance.

[edit]Membrane separation processes

Membrane separation processes have very important role in separation industry. Nevertheless, they were

not considered technically important until mid-1970. Membrane separation processes differ based on

separation mechanisms and size of the separated particles. The widely used membrane processes

include microfiltration, ultrafiltration, nanofiltration, reverse

osmosis,electrolysis, dialysis, electrodialysis, gas separation, vapor permeation, pervaporation,

membrane distillation, and membrane contactors.[3] All processes except for pervaporation involve no

phase change. All processes except (electro)dialysis are pressure driven. Microfltration and ultrafiltration is

widely used in food and beverage processing (beer microfiltration, apple juice ultrafiltration),

biotechnological applications and pharmaceutical industry (antibiotic production, protein purification), water

purification and wastewater treatment, microelectronics industry, and others. Nanofiltration and reverse

osmosis membranes are mainly used for water purification purposes. Dense membranes are utilized for

gas separations (removal of CO2 from natural gas, separating N2 from air, organic vapor removal from air or

nitrogen stream) and sometimes in membrane distillation. The later process helps in separating of

azeotropic compositions reducing the costs of distillation processes.

Ranges of membrane based separations.