Presentation Title

Systematic Analysis and Optimization of Power Generation in Pressure Retarded Osmosis: Effect of Multi-Stage Design

Faculty Mentor

Mingheng Li

Start Date

18-11-2017 10:45 AM

End Date

18-11-2017 11:00 AM

Location

9-245

Session

Engineering/CS 2

Type of Presentation

Oral Talk

Subject Area

engineering_computer_science

Abstract

This work presents a systematic method for analysis and optimization of specific energy production (SEP) of PRO systems employing single-stage configuration as well as multi-stage design with inter-stage hydro-turbines. It is shown that the SEP normalized by the draw solution feed osmotic pressure increases with the number of stages as well as a dimensionless parameter. As compared to the single-stage PRO, the multi-stage arrangement not only increases flux and volume gain, but also allows a stage-dependent, progressively decreasing hydraulic pressure, both of which contribute to enhanced SEP and power density. At the thermodynamic limit where the dimensionless parameter goes to infinity, the theoretical maximum SEP that can be recovered by an N-stage PRO system is N(1 − qtot-1/N)*(PI0), where qtot is the ratio of the draw solution flow rate at the outlet to the inlet of the whole system. For single-stage PRO, it is no more than PI0. For an infinite number of stages, the theoretical limit becomes (lnqtot)*PI0. The effect of pump, turbine and PRO efficiency on SEP are discussed.

Keywords: pressure retarded osmosis; specific energy production; modeling; system-level analysis; optimization

Summary of research results to be presented

The NSEP of PRO systems increases with both the dimensionless membrane area and number of stages. Multi-stage design also improves power density, especially when osmotic pressure or membrane permeability is large. This is due to increased flux and a gradually reducing hydraulic pressure profile along the entire process. At the thermodynamic limit, the maximum power that can be recovered by an N-stage PRO system is N*(1-qtot-1/N)*Q0*PI0. For single-stage, it is always less than Q0PI0. For an infinite number of stages, it becomes (ln(qtot))*Q0*PI0 which is equivalent to the power delivered by an ideal, fully reversible PRO system.

This document is currently not available here.

Share

COinS
 
Nov 18th, 10:45 AM Nov 18th, 11:00 AM

Systematic Analysis and Optimization of Power Generation in Pressure Retarded Osmosis: Effect of Multi-Stage Design

9-245

This work presents a systematic method for analysis and optimization of specific energy production (SEP) of PRO systems employing single-stage configuration as well as multi-stage design with inter-stage hydro-turbines. It is shown that the SEP normalized by the draw solution feed osmotic pressure increases with the number of stages as well as a dimensionless parameter. As compared to the single-stage PRO, the multi-stage arrangement not only increases flux and volume gain, but also allows a stage-dependent, progressively decreasing hydraulic pressure, both of which contribute to enhanced SEP and power density. At the thermodynamic limit where the dimensionless parameter goes to infinity, the theoretical maximum SEP that can be recovered by an N-stage PRO system is N(1 − qtot-1/N)*(PI0), where qtot is the ratio of the draw solution flow rate at the outlet to the inlet of the whole system. For single-stage PRO, it is no more than PI0. For an infinite number of stages, the theoretical limit becomes (lnqtot)*PI0. The effect of pump, turbine and PRO efficiency on SEP are discussed.

Keywords: pressure retarded osmosis; specific energy production; modeling; system-level analysis; optimization