Ngai Yin YIP

Ph.D. Candidate, Chemical and Environmental Engineering, Yale University
M.S. and M.Phil. Chemical and Environmental Engineering, Yale University, 2011
B. Eng (First Class Honors) Civil and Environmental Engineering, Nanyang Technological University (Singapore), 2004

E-mail: ngaiyin.yip@yale.edu

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Ngai Yin is a PhD student advised by Professor Menachem Elimelech in the Environmental Engineering Program at Yale University. His research interests are in the general area of membrane technology for sustainable water supply and energy production. His research focuses on high performance polymeric membranes for osmotically-driven membrane processes (ODMPs).

Forward osmosis (FO), a subset of ODMPs, has demonstrated the potential for application in sea and brackish water desalination, wastewater reclamation and industrial wastewater treatment. FO exploits the natural phenomenon of osmosis, which occurs when two solutions of different concentration are placed on opposite sides of a semi-permeable membrane. The osmotic pressure difference drives the permeation of water across the membrane from the dilute solution to the concentrated solution, while the selective property of the membrane retains the solutes in their respective sides.

The ammonia-carbon dioxide FO desalination system, developed here at Yale, enables low-grade geothermal or waste heat from industrial facilities to be utilized as an energy source to drive the separation process. The potential advantage of the technology lies in the production of fresh drinking water with relatively lesser electricity consumption and, hence, at a lower cost.

Pressure retarded osmosis (PRO), the other subset of ODMPs, holds the promise to produce renewable energy from natural and anthropogenic salinity gradients. PRO exploits the same osmotic pressure difference that develops when a semi-permeable membrane separates two solutions of different concentrations, except that a hydraulic pressure is applied on the more concentrated draw solution. As water permeates across the membrane into the pressurized draw solution, a hydroturbine extracts work from the expanding draw solution volume.

Natural salinity gradients, for example those arising from the mixing of freshwater rivers flowing into oceans, have the potential to produce electricity for over half a billion people. Additionally, PRO can use anthropogenic waste streams, such as concentrated brine from a desalination plant, as draw solutions. As such, PRO power generation has the potential to be an alternative source of sustainable energy, and contribute to the alleviation of the energy crisis facing us today.  

Prior to his PhD studies, Yip (a name he habitually goes by) completed his Bachelor of Engineering degree in Nanyang Technological University in Singapore, with his research thesis focusing on nanofiltration processes. After graduation he worked for the Singapore government in the National Environment Agency, formulating and implementing policies for the country.

An avid outdoor and sports person, he recently scaled the Dolomites of the Eastern Alps in Italy. Next, he is planning to SCUBA dive among the pelagic fishes in the seas of Belize.

Cath, T.Y., Elimelech, M., McCutcheon, J.R., McGinnis, R.L., Achilli, A., Anastasio, D., Brady, A.R., Childress, A.E., Farr, I.V., Hancock, N.T., Lampi, J., Nghiem, L.D., Xie, M., Yip, N.Y. "Standard Methodology for Evaluating Membrane Performance in Osmotically Driven Membrane Processes", Desalination, Volume 312, March 2013, pages 31–38.  PDF File.

Mo, Y.H., Tiraferri, A., Yip, N.Y., Adout, A., Huang, X., and Elimelech, M. "Improved Antifouling Properties of Polyamide Nanofiltration Membranes by Reducing the Density of Surface Carboxyl Groups", Environmental Science & Technology, Volume 46, December 2012, pages 13253–13261.  PDF File.  Supporting Information.

Shaffer, D.L., Yip, N.Y., Gilron J., and Elimelech, M. "Seawater Desalination for Agriculture by Integrated Forward and Reverse Osmosis: Improved Product Water Quality for Potentially Less Energy", Journal of Membrane Science, Volume 415–416, October 2012, pages 1 –8.  PDF File. 

Yip, N.Y. and Elimelech, M. "Thermodynamic and Energy Efficiency Analysis of Power Generation from Natural Salinity Gradients by Pressure Retarded Osmosis", Environmental Science & Technology, Volume 46, May 2012, pages 5230–5239.  PDF File.  Supporting Information.

Yip, N.Y. and Elimelech, M. "Performance Limiting Effects in Power Generation from Salinity Gradients by Pressure Retarded Osmosis", Environmental Science & Technology, Volume 45, December 2011, pages 10273–10282.  PDF File.  Supporting Information.

Hoover, L.A., Phillip, W.A., Tiraferri, A., Yip, N.Y., and Elimelech, M. "Forward with Osmosis: Emerging Applications for Greater Sustainability", Environmental Science & Technology, Volume 45, December 2011, pages 9824–9830.  PDF File.

Ang, W.S., Yip, N.Y., Tiraferri, A., and Elimelech, M. "Chemical Cleaning of RO Membranes Fouled by Wastewater Effluent: Achieving Higher Efficiency with Dual-step Cleaning", Journal of Membrane Science, Volume 382, October 2011, pages 100-106.  PDF File.

Yip, N.Y., Tiraferri, A., Phillip, W.A., Hoover, L.A., Schiffman, J.D., Kim, Y.C., and Elimelech, M. "Thin-Film Composite Pressure Retarded Osmosis Membranes for Sustainable Power Generation from Salinity Gradients", Environmental Science & Technology, Volume 45, May 2011, pages 4360–4369.  PDF File.  Supporting Information.

Tiraferri, A., Yip, N.Y., Phillip, W.A., Schiffman, J.D., Elimelech, M. "Relating Performance of Thin-Film Composite Forward Osmosis Membranes to Support Layer Formation and Structure", Journal of Membrane Science, Volume 367, February 2011,  pages 340-352.  PDF File.

Yip, N.Y., Tiraferri, A., Phillip, W.A., Schiffman, J.D., and Elimelech, M., "High Performance Thin-Film Composite Forward Osmosis Membrane", Environmental Science & Technology, Volume 44, May 2010, pages 3812–3818.  PDF File.  Supporting Information.