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Low Energy Desalination with Pressure-Retarded Osmosis

Low Energy Desalination with Pressure-Retarded Osmosis. Amy E. Childress, Professor Department of Civil and Environmental Engineering University of Southern California. CalDesal San Diego, CA October 3, 2013. Why the Interest in PRO?. Sustainability. Water for Energy.

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Low Energy Desalination with Pressure-Retarded Osmosis

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  1. Low Energy Desalination withPressure-Retarded Osmosis Amy E. Childress, Professor Department of Civil and Environmental Engineering University of Southern California CalDesal San Diego, CA October 3, 2013

  2. Why the Interest in PRO? Sustainability Water for Energy Extraction & Refining Hydropower Fuel Production Thermo Electric Cooling Wastewater Treatment Drinking Water Treatment Energy Associated with Uses of Water Extraction and Transmission Energy for Water

  3. PRO in the NewsStatkraft – Norwegian state-owned electric company First experimental (10 kW) installation November 24, 2009 Investing in and inspiring PRO and FO membrane and module development Power density: 1.5 W/m2 Target: 5 W/m2

  4. River-to-Sea Pressure-Retarded Osmosis • A means for capturing solar energy EVAPORATION CONDENSATION PRECIPITATION PRO SALINATION Freshwater Seawater Energy Global energy production from mixing in estuaries: 2,000 TWh/y Current global energy production from all renewable sources: 10,000 TWh/y

  5. River-to-Sea Pressure-Retarded Osmosis • A means for capturing solar energy • A process of capturing the energy released from the mixing of freshwater with saltwater River Ocean

  6. River-to-Sea Pressure-Retarded Osmosis • A means for capturing solar energy • A process of capturing the energy released from the mixing of freshwater with saltwater Δπ=340 psi (2383 KPa) River Ocean

  7. River-to-Sea Pressure-Retarded Osmosis • A means for capturing solar energy • A process of capturing the energy released from the mixing of freshwater with saltwater River 225 m Ocean

  8. River-to-Sea Pressure-Retarded Osmosis • A means for capturing solar energy • A process of capturing the energy released from the mixing of freshwater with saltwater • Transformation of chemical potential to hydraulic potential Norman, 1974

  9. Power Generation with PRO Diluted seawater Seawater Low pressure pump Pressure exchanger L H Circulation pump Seawater Hydroturbine and generator Diluted seawater Draw solution side Diluted seawater W=-JΔP Low pressure pump J=A(Δπ-ΔP) Membrane Feed solution side Net power Pumps Flushing solution Fresh water Achilli, Cath, Childress, 2009; Adapted from Loeb, 2002

  10. Coastal Water System Drinking Water Wastewater Wastewater Treatment Facility Desalination Facility (RO) High-Salinity Brine Treated Wastewater Seawater slide by Andrea Achilli

  11. Coastal Water System Drinking Water Wastewater Wastewater Treatment Facility PRO Desalination Facility (RO) Energy Recovery Facility Seawater Higher Δπ (750 psi) than river-to-sea PRO slide by Andrea Achilli

  12. Current Practice: Seawater Desalination Drinking water Concentrate RO Pressurized feed High pressure Feed

  13. Current Practice: Seawater Desalination Drinking water Concentrate RO Pressurized feed High pressure Pressure PX Feed Low pressure

  14. Current Practice: Seawater Desalination Drinking water Concentrate RO Pressurized feed High Salinity PX Environmental Concern (CA Regulatory/Permitting Issue) Feed

  15. RO-PRO System Drinking water Impaired water RO Pressurized feed Osmotic pump High pressure PRO 1 PX 2 Feed 1 - Energy generation 2 - Concentrate dilution

  16. Project Objectives • Evaluate energy requirements of ideal and model RO-PRO system • Evaluate energy requirements of experimental RO-PRO system • Design and construct a system that would, for the first time, pre-pressurize RO feed water using PRO • Test RO, RO-PX, and RO-PRO and compare results

  17. Theoretical RO Energy Requirement Thermodynamic limit ROp RO ROb Actual energy ROf RO Recovery = ROp/ROf

  18. PRO as Opposite of RO PROp PRO PROD,in Thermodynamic limit Actual energy PROD,out PRO Dilution = PROp/PROD,out

  19. RO-PRO Desalination System PROp ROp PRO RO ROb = PROD,in ROf PROD,out

  20. RO-PRO Energy Requirements “ideal” case RO-PRO 30% specific energy reduction model results RO-PX

  21. Experimental BGNDRF, Bureau of Reclamation Alamogordo, NM Summer 2012 UNR Fluids Lab Fall 2012 - Spring 2013

  22. Experimental Setup • PX: Custom-made from Isobaric Strategies, Inc. • RO membranes: three Dow FilmTec SW30-2540 in series • PRO membrane: Seawater Basin Seawater Pump RO Pump Vds,ex PX Vf Booster Pump Vb= Vds,en Vp,RO Vf,ex Vp,PRO Needle Valve Drain RO PRO Vf,en Needle Valve Fresh Water to Drain PRO Feed Pump Fresh Water

  23. “Current” Generation Membrane • Cellulose triacetate (CTA) from Hydration Technology Innovations (HTI) • A = 1.87 E-9 m/s/kPa • B = 1.11 E-7 m/s • S = 6.78 E-4 m Achilli et al. 2009 Newer Generation Membrane • Thin film composite (TFC) membrane from Oasys Water • A = 1.42 E-8 m/s/kPa • B = 2.41 E-8 m/s • S = 3.10 E-4 m Operation Challenges! unable to operate at high flowrates and fully utilize PRO membranes

  24. Specific Energy Consumption Summary • Proved that the energy from a volume of water transferred from atmospheric pressure to elevated pressure across a semi-permeable membrane can be utilized to pre-pressurize RO feed water. • Published the first experimental PRO power density data for a RO-PRO system (1.1 to 2.3 W/m2). • But not able to achieve projected energy reductions… ≅15%

  25. Specific Energy Consumption Summary Gen-2 Pilot System • Operation at 50% RO recovery • simulates full scale applications • increases draw solution concentration • Operation at higher flowrates • fully utilizes PRO membranes • Implementation of 2nd pressure exchanger • Completes system design to recover all waste energy • Selection of efficient and stable pumps

  26. Considering Pretreatment in System Drinking water Feed Pretreatment 0.2-0.3 KWh/m3 ? Impaired water RO Osmoticpump High pressure PRO PX DS Pretreatment

  27. Footprint of a PRO power plant http://www.water-technology.net/projects/israel/israel1.html Ashkelon desalination plant in Israel is approximately 17.3 acres (70,000 m2) Identically sized PRO power plant could reduce energy consumption by up to 30%

  28. Compared to other renewable energy 1110 Acres 100 Acres 25 Acres http://gotpowered.com/2011/e-on-says-there-will-be-800000-mw-of-wind-energy-by-2025/ http://www.water-technology.net/projects/israel/israel1.html http://www.wired.com/wiredenterprise/2012/09/apple-doubles-down-on-maiden/ Steel Park Wind Farm Arizona (Proposed) 15 MW Apple Solar Farm Maiden, North Carolina 20 MW PRO Power Plant 14 MW

  29. Final Remarks • A subsidized renewable energy market, such as currently exists in the EU, may be needed until membrane and module technology gaps can be filled • Higher salinity gradient in RO-PRO system is likely to make RO-PRO a more promising component of an alternative energy portfolio than river-to-sea PRO systems; RO-PRO system also provides concentrate dilution • PRO membranes have improved an order of magnitude over past 3 years, but still need: • Commercial competition for membranes • New membrane modules / packing

  30. Acknowledgements • US Bureau of Reclamation • Oasys Water • Hydration Technology Innovations • Isobarix • Dr. Andrea Achilli, Jeri Prante, and Dr. Sage Hiibel

  31. amyec@usc.edu

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