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Pressure Retarded Osmosis


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Discusses the mode of power generation using Pressure Retarded Osmosis, based on the salinity gradient concept.

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Pressure Retarded Osmosis

  1. 1. PRESSURE RETARDED OSMOSIS By: Matthew Fenech Subject: Alternative Power Generation Lecturer: Ing.T. Darmanin
  2. 2. Ocean Technology • Tidal Energy; Abundant but Untameable! – Unpredictable – Requires large control effort • CalmerWaters are also abundant in energy – Osmosis is the key! – Dealing with forward osmosis (not reverse)
  3. 3. Theory of Operation • Osmotic Power, “A pressure that must be applied to the solution (sea water) to just prevent osmotic flow” • Harnessing energy where river freshwater and seawater meet • Seawater is pumped into a pressure exchanger where the osmotic pressure is less than that of the freshwater pressure
  4. 4. Theory of Operation • Freshwater(solvent) flows through the semi-permeable membrane towards the seawater (solute) chamber and increases the mass and volume (Δh) – ButWhy? Water flows from a lower concentration to a higher concentration to equalize the concentration levels – Semi-permeable inhibiting salts to pass through the fresh water side • The head that is generated where generally heads of 120 - 270m (26Bar) are reached • Compared to a waterfall head, for hydro- power generation (Fernanda Helfer, N/D)
  5. 5. History of Pressure Retarded Osmosis • 1954, Pattle published free-energy acquisition via freshwater and saltwater mixing • 1973, interest in technology reemerged due to oil crisis • 1975, PRO was first invented by Prof. Sidney Loeb & Osmotic Heat Engine • 2006, Starkraft (Norway) developed the first PRO powerplant generating 10KW (Andrea Achilli, 2010)
  6. 6. Pressure Retarded Osmosis Technology • “The Energy Released from the mixing of freshwater with saltwater” • Salinity gradient power is the energy created from the difference in salt concentration between two fluids, fresh & salt water. • Applications: – Standalone power plants – Hybrid power plants
  7. 7. Pressure Retarded Osmosis Technology • Main Components – Pumps – Stacks of Semi-permeable membrane, Hollow Fibre Membranes, generating 4.4W/m2 – Pressure Exchanger, energy recovery system – Piping Network – Hydro-Turbine – Generator
  8. 8. Geographical Power Generation (Irena, 2014)
  9. 9. Economics • Membranes account up to 80% of capital costs – EUR10/m2 -> EUR30/m2 – To be competitive (with other renewables) must be dropped down to EUR2/m2 -> EUR5/m2 • For a 2MW plant, 2million m2 of membranes are required • Cost projections for 2020 EUR0.08/KWh to EUR0.15/KWhr (Irena, 2014)
  10. 10. Drivers and Barriers + Emission Free power generation + It is alternative and sustainable ‒ Biological Fouling due to microorganisms ‒ Excessive capital costs ‒ Membrane lifetime, 5 years ‒ Ecological Aspects; River deviations ‒ Environmentalists unrest
  11. 11. Conclusion • Infant technology • Other SalinityGradientTechnology – Reversed Electro Dialysis (RED) – Osmotic Heat Engine • Future trends…
  12. 12. Questions?
  13. 13. References • Andrea Achilli, A. E. (2010). Pressure retarded osmosis: From the vision of Sidney Loeb to the first prototype. Nevada: Elsevier. • Fernanda Helfer, C. L. (N/D). Osmotic Power with Pressure Retarded Osmosis: Theory, Performance and Trends – a Review. Southport. • Irena. (2014). Salinity Gradient Energy, Technology Brief. IRENA (International Renewable Energy Agency).