Utilization of renewable energy sources, as an approach to reduce greenhouse
gas (GHG) emissions, have been globally popular in the last few decades. Among
renewable energy sources, pressure retarded osmosis (PRO) has been scrutinized by
scientists since the mid 70's. However, even today, the existing river-sea PRO systems
can only marginally meet the generally approved criterion of 5 W/m2 power density,
a threshold for an economically feasible PRO system. As an approach to increase the
performance of PRO systems, multi-staging of PRO modules are investigated.
A mathematical model of the scaled up PRO process is proposed with consideration
for internal and external concentration polarization, reverse salt flux, and spatial
variations along the membrane. A thermodynamic model is also developed with consideration
for entropy generation and losses in the process. It predicts the percentile
of each work loss source compared to the net work in the system. Several confi gurations
of dual stage PRO system are presented and compared to single stage PRO.
The comparison is based on three proposed target functions of power density (PD),
specifi c energy (SE), and work per drawn freshwater (Wdrawn). Applied hydraulic
pressures and flow rates of draw and feed solutions are optimized for maximizing the
target functions. The results indicate that overall performance of the system could
be improved by up to 8 % with a dual stage PRO in the case of SE. The system performance is not improved by depressurizing the draw solution before the second
module in cases of SE and Wdrawn. The thermodynamic analysis demonstrate the
contribution of each work loss and justify the reason of diminishing the net work over
the losses. The effect of membrane area and membrane characteristics on the SE target
function is also investigated. The distribution of membrane area in each module
depends on the selected con figuration and inlet draw solution. In the dual stage systems,
the SE value increases up to 14% by improving the membrane characteristics.
Reducing the salt rejection coefficient (B) is the most e ective membrane characteristic
in our con figurations. Replacing seawater with RO brine in draw solution results
in a signifi cant improvement in SE values. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/10907 |
| Date | 31 May 2019 |
| Creators | Soltani, Roghayeh |
| Contributors | Struchtrup, Henning |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
Page generated in 0.0021 seconds