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OSMOTIC POWER
AvailabilityThe globally available power has been estimated to be between 1.4 and 2.6TWMi i f i i h f K Mixing 1m3 of river water with 1m3 of sea water at 293K gives 1.4MJBut mixing 1m3 of river water with ”infinite” m3 of sea But mixing 1m3 of river water with infinite m3 of sea water gives 2.3MJMississippi with an average discharge of 17000 m3/s Mississippi with an average discharge of 17000 m /s has a potential of 40 GW of which 9.8GW is technically possible to convert to electricity
[2]
HistoryOne first mentions of this was done in 1954 by R.E. Pattle [8]D i h i d h During the 1970s osmotic power made progress as the membrane technology was developed by Loeb S. [6]Has again become more popular as the price of energy Has again become more popular as the price of energy has gone up and the demand for green energy has increasedThe properties of the membrane has been and still are the problem for a successful deployment of the concept
[2]
Work from a salt power plantWork from a salt power plantThe mixing of sea water ith f h t i with fresh water gives a
(mixing) exergy effectthat can be exploitedOsmosis leads to transport of water across the membraneacross the membranefrom the fresh to salt side solution
[7]
Work from a salt power plantThis gives a hydrostatic pressure differenceI t lli b t
Work from a salt power plant
Installing a membrane system at 120‐150 m below fresh water intake allows for a significant
h d ffextra hydro power effect
[7]
Work from a salt power plantThe fresh water will go through the membrane,
i t diff
Work from a salt power plant
against a pressure difference; the pressure on the sea water side is not high enough to prevent to fresh water movement.
[7]
Work from a salt power plantIn reality, only part of the potential energy is recovered; the
it ’t b l 6 b l
Work from a salt power plant
unit can’t be as low as 163 m belowthe fresh water intake. Entropy production in the py pmembrane (combined heat and mass transfer) is important
[7]
A schematic view of a membrane[5]
Time evolution of solution pressure in a rigid container [1]An ideal membrane is compared to a membrane with a small leakage. t1 can be of the order of a
l f i t t f d
•The membrane consists of a support structure and of the “active component”, the skin. The concentration difference between C4 and C3 drives the system•The membrane material can be biological or
couple of minutes to a few daysg
synthetic, cellulose acetate has been for instance used
Efficiency of the membrane [1]
The power efficiency of the membrane
The efficiency has increased from y0.1W/m2 to 3 during the research at Statkraft [4]
Schematic view of a osmotic powerosmotic power plant [3]•This plant can be run at the surface of the earth due to the surface of the earth due to the pressure exchanger•The pressure exchanger uses 2/3 of the pressurized water•The pressure exchanger could be The pressure exchanger could be swapped for a pump but that is even a worse of an idea•How to run the pressure exchanger is important for the production of electricity•An average 25 MW plant is calculated to need 5 million m2 of membranes
Prototype by Statkraft
•Was started the 24 of November in Tofte outside Oslo, Norway•The plant is equipped with 2000m2 of membranes•The design capacity is 10kW, but that is not yet the production
The development of the concept of osmotic power at Statkraft [6]p p p [ ]
References:[1] Thermodynamic studies of osmotic flows and their applications to energy conversion
systems, Seppälä A., (2007), Doctoral dissertation, Helsinki University of Technology, pp.46
[2] Blue Energy: Electricity production from salinity gradients by reverse electrodialysis, Post J. W., (2009) , Doctoral dissertation, Wageningen University, Wageningen, NL, pp. Post J. W., (2009) , Doctoral dissertation, Wageningen University, Wageningen, NL, pp. 224
[3] Unleashing renewable energies from the ocean: Statkraft’s experience in developing business opportunities in imature technologies and markets, The force of osmosis and Tidal Curents, Sandvik Ø. S., Herslecht P., Seelos K.,(2009) HYDRO2009, pp.9
[ ]St t f t h l i f h i S li it P d th t O ti [4]Status of technologies for harnessing Salinity Power and the current Osmotic power activities, Sandvik Ø. S., Skillhagen S. E., (2008), Annual Report of the IEA‐OES, pp.4
[5]Power Production based on Osmotic Pressure, Sandvik Ø. S., Skillhagen S. E., Nielsen W. K., (2009), Waterpower XVI, pp.9
[6]Osmotic Power brought 9.2.2009 from [6]Osmotic Power brought 9.2.2009 from http://www.statkraft.com/Images/Osmotic%2009%20ENG_tcm9‐4591.pdf, pp 2
[7] Process engineering thermodynamics , Zevehoven R., 2008, course 424304, Chapter 4[8] Production of Electric Power by mixing Fresh and Salt Water in the Hydroelectric Pile,
Pattle R.E., 1954, Nature 174, 660 (2 October 1954)