This document outlines osmotic power, which generates energy from the difference in salt concentration between seawater and freshwater. It works via pressure retarded osmosis (PRO) where freshwater naturally moves through a semi-permeable membrane into higher salinity seawater, increasing pressure. This pressure powers a turbine to generate electricity. Key components include membrane modules to separate the waters, filters to optimize membrane performance, and a turbine/generator. Experimental results showed a prototype achieving over 90% efficiency and the potential to scale installations by adding more membrane modules.
3. MOTIVATION
Non conventional power in
various sources is effected
predominantly by climatic
conditions and cannot be
operated throughout the
year.
Need for development of
new type of non
conventional power that can
be operated 24/7 and that is
osmotic power.
First osmotic power plant is
built in Tofte, Norway in
2009.
4. INTRODUCTION
Osmotic power is energy available from difference
in salt concentration between sea water and river
water.
It is huge and unique energy source.
Renewable energy source that converts pressure
differential between water with high salinity and
water with lower or no salinity in to hydraulic
pressure.
Fresh water moves by osmosis through membrane
in to sea water.
5. OSMOSIS
Physical process in
which solvent moves
across semi permeable
membrane separating
solutions of different
concentrations.
Osmosis is vital
process in biological
systems as biological
membranes are semi
permeable.
Before Osmosis After Osmosis
6. Osmotic pressure:
Minimum pressure that should be applied to a
solution to prevent inward flow of water across semi
permeable membrane.
Measure of tendency of solution to take in water by
osmosis.
Potential osmotic pressure:
Maximum osmotic pressure that can be developed
in a solution if it were separated from fresh water by
a selective permeable membrane.
8. PRINCIPLE
Osmotic power is
generated by pressure
retarded osmosis
(PRO).
Technique to separate
solvent (fresh water)
from a solution that is
more concentrated
(sea water) and also
pressurized.
Turbine
9. PRESSURE RETARDED OSMOSIS
It relies on water molecules moving through a semi
permeable membrane.
Semi permeable membrane allows solvent (fresh
water) to pass to the concentrated solution (sea
water) side by osmosis.
This technique can be used to generate power from
salinity gradient energy resulting from the difference
in salt concentration between sea water and river
water.
Output is proportional to the salinity.
11. COMPONENTS
1. A semi permeable membrane contained in
modules.
2. Fresh water and sea water filters that optimize
membrane performance.
3. A turbine that generates a driving force based on
osmotic pressure and permeation flow rate.
4. A pressure exchanger that pressurizes sea water
feed required to maintain high salinity levels
downstream from membrane.
13. OPERATION
Fresh water and sea water sent into two different
modules.
The two modules are separated by a semi-
permeable membrane.
The Fresh water seeps through the semi-
permeable membrane to the Salt water side.
This increases pressure on the salt water module.
14. OPERATION
The salt water flows
through the turbine which
in turn generates
electricity.
The brackish water is sent
out to the sea.
The high pressure salt
water is again sent to the
modules through a
pressure exchanger.Fig:Francis Turbine
(Cortesy: www.Google.com)
18. EFFICIENCY
The efficiency of this Osmotic power is 91.0%.
The Efficiency(Npx) of the Osmotic power is given by
the above expression.
Emech,salt is the energy potential of salt water.
Emech,brackish is the energy potential of fresh water.
19. ADVANTAGES
Steady, predictable output.
Adaptable for small or large generating stations.
Scalable or modular design (membrane modules
added as required), making it possible to increase
installed capacity.
Generating sites near load centers, limiting power
transmission needs.
Good potential for power plant sites.
20. ADVANTAGES & DISADVANTAGES
Technology similar and complementary to that of
hydro-electric power, with osmotic power plants
able to be built on already-harnessed rivers.
High risk of clogging and gradual degradation of
semi-permeable membranes, necessitating
pressure-filtering pretreatment of fresh water and
periodic membrane re-placement (every 5 to 7
years)
21. CONCLUSION
An analysis of the PRO processes for energy
production from mixing of freshwater and seawater
has been performed at realistic conditions for
physical plant operation.
A freshwater utilization efficiency of 40% of the
maximum mixing energy of freshwater with sea
water.