Enhanced energy generation and membrane performance by two-stage pressure retarded osmosis (PRO)

Abstract

Power density, extractable energy and average power density are introduced.• Four different configurations of the proposed TwoPRO are proposed and analyzed.• CDCF, CDDF and DDCF have advantageous osmotic energy capacity.• At high dimensionless flow rate, CDCF and CDDF have high average power density. a b s t r a c tA systematic model of a salinity power plant involving two PRO (TwoPRO) modules is presented in this paper. The results clearly indicate that the performance of a PRO plant can be improved with a two-stage configuration. For comparison purposes, a single-stage PRO (SinglePRO) is first analyzed and optimized with respect to three key concepts, power density, extractable energy and average power density. The two-stage configuration of the TwoPRO is then studied using two schemes: continuous scheme in which the stream is treated as a continuous flow between the two stages and divided scheme in which the flow is divided first and separately treated in each stage. Accordingly, four different configurations are proposed, namely continuous draw and continuous feed solution (CDCF), divided draw and divided feed solution (DDDF), continuous draw and divided feed solution (CDDF), and divided draw and continuous feed solution (DDCF). The results indicate that the configurations CDCF, CDDF and DDCF have advantageous capacity in salinity energy harvesting. Configurations CDCF and CDDF also perform better than the single-stage PRO in terms of average power density with a higher feed solution flow ratio. Additionally, the membrane performance of the TwoPRO strengthens with higher level of membrane usage.Crown

Modeling and simulation of the dual stage pressure retarded osmosis systems

“…Shaheed et al [25] introduced dual stage PRO system and conducted a thermodynamic analysis on it. In another study, they proposed four configurations of CDCF, DDDF, CDDF, and DDCF, either with the continuous or divided flow (C or D) of the draw and feed solution (D and F) ( Figure 2.16) [129]. All configurations utilize energy recovery systems and pump-turbine (PT) pairs.…”

Evaluation the potential and energy efficiency of dual stage pressure retarded osmosis process

“…Practically, this reduces the efficiency of PRO process and makes its application less productive. Recent research has suggested adding a second stage PRO process to capture the rest of osmotic energy from the diluted draw solution before discharge [25][26][27], hence maximizing the energy efficiency of PRO process. The diluted draw solution from the first stage and a raw feed solution are coupled to form the salinity gradient of the second stage [ Figure 1]; this will rebuild the chemical potential difference across the PRO membrane.…”

Recent Advances in Osmotic Energy Generation via Pressure-Retarded Osmosis (PRO): A Review

“…In addition, an energy and thermodynamic analysis of the single-stage PRO process was conducted by He et al [62], and further, the performance of the dual-stage PRO process under four different configurations was identified [63]. It was found that the configurations of the continuous draw and continuous feed solution (CDCF) and the continuous draw and divided feed solution (CDDF) were more beneficial than for single-stage PRO processes.…”