scholarly journals Modeling and Optimization of Membrane Process for Salinity Gradient Energy Production

Separations ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 64
Author(s):  
Lianfa Song
Keyword(s):  
Osmotic Pressure ◽  
Energy Production ◽  
Salinity Gradient ◽  
Water Flux ◽  
Hydraulic Pressure ◽  
Semipermeable Membranes ◽  
Pressure Retarded Osmosis ◽  
Higher Power ◽  
Gradient Energy ◽  
Breakeven Point

When hydraulic pressure was added on the feed side of the membrane in the otherwise conventional pressure retarded osmosis (PRO) process, the production rate of the salinity gradient energy could be significantly increased by manipulating the hydraulic pressures on both sides of the membrane. With hydraulic pressure added on the feed side of the membrane, much higher water flux could be obtained than that under the osmotic pressure of the same value. The osmotic pressure of the draw solution, instead of drawing water through the membrane, was mainly reserved to increase the hydraulic pressure of the permeate. In this way, orders of magnitude higher power density than that in the conventional PRO can be obtained with the same salinity gradient. At the optimal conditions, it was demonstrated that the energy production rates that were much higher than the economical breakeven point could be obtained from the pair of seawater and freshwater with the currently available semipermeable membranes.

scholarly journals Metastable State of Water and Performance of Osmotically Driven Membrane Processes

Membranes ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 43 ◽  
Author(s):  
Haifeng Zhang ◽  
Jie Wang ◽  
Ken Rainwater ◽  
Lianfa Song
Keyword(s):  
Osmotic Pressure ◽  
Metastable State ◽  
Necessary Condition ◽  
Hydraulic Pressure ◽  
Membrane Thickness ◽  
Semipermeable Membranes ◽  
Membrane Processes ◽  
State Of Water ◽  
Fundamental Reason ◽  
And Performance

Semipermeable membranes play critical roles in many natural and engineering systems. The osmotic pressure is found experimentally much less effective than the hydraulic pressure to drive water through the membrane, which is commonly attributed to the internal concentration polarization (ICP) in the porous layer of the membrane. In this study, it has been shown that a necessary condition for the osmotic pressure to be effective is water continuity across the entire membrane thickness under negative pressure, i.e., the water inside the membrane remains in a metastable state. However, the metastable state of water cannot be maintained indefinitely, and cavitation will undoubtedly occur in the osmotically driven processes. Collapse of the water metastable state was suggested for the first time to be a more important and fundamental reason for the low water fluxes in the osmotically driven membrane processes.

Determining the Potential of Salinity Gradient Energy Source Using an Exergy Analysis

2016 ◽  
Author(s):  
Arash Emdadi ◽  
Mansour Zenouzi ◽  
Gregory J. Kowalski
Keyword(s):  
Sodium Chloride ◽  
Power Density ◽  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Exergy Analysis ◽  
Salinity Gradient ◽  
Chloride Concentration ◽  
Semipermeable Membranes ◽  
Dead State ◽  
Gradient Energy

Mixing of fresh (river) water and salty water (seawater or saline brine) in a control fashion would produces an electrical energy known as salinity gradient energy (SGE). Two main conversion technologies of SGE are membrane-based processes; pressure retarded osmosis (PRO) and reverse electrodialysis (RED). In PRO, semipermeable membranes placed between the two streams of solutions allow the transport of water from low-pressure diluted solution to high-pressure concentrated solution. RED requires two alternating semipermeable membranes that allow the diffusion of the ions but not the flow of H2O. Lifetime and power density of the semipermeable membrane are two main factors affecting on deployment of PRO and RED. Semipermeable membranes with lifetime greater than 10 years and power density higher than 5 W/m2 would lead to faster development of this conversion technology. An exergy analysis of an SGE system of sea-river can be applied to calculate the maximum potential power for electricity generation. Seawater is taken as reference environment (global dead state) for calculating the exergy of water since the seawater is the final reservoir. Once the fresh water is mixed with water of the sea or lake it becomes unuseful for human, agricultural or industrial uses loses all its exergy. Aqueous sodium chloride solution model is used in this study to calculate the thermodynamic properties of seawater. This model does not consider seawater as an ideal model and provides accurate thermodynamics properties of sodium chloride solution. As a case study, exergy calculation of Iran’s Urmia Lake-GadarChay River system. The chemical exergy analysis considers sodium chloride (NaCl) as main salt in the water of Lake Urmia. The sodium chloride concentration is more than 200 g/L in recent years. Based on the exergy results the potential power of this system is 329 MW. This results indicates a high potential for constructing power plant for salinity gradient energy conversion.

scholarly journals Feasibility of Pressure-Retarded Osmosis for Electricity Generation at Low Temperatures

Membranes ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 556
Author(s):  
Elham Abbasi-Garravand ◽  
Catherine N. Mulligan
Keyword(s):  
Power Density ◽  
Membrane Fouling ◽  
Low Temperatures ◽  
Sea Water ◽  
Salinity Gradient ◽  
Operating Conditions ◽  
Pressure Retarded Osmosis ◽  
Water Transportation ◽  
Gradient Energy ◽  
Temperature Impact

A membrane-based technique for production of pressure-retarded osmosis (PRO) is salinity gradient energy. This sustainable energy is formed by combining salt and fresh waters. The membrane of the PRO process has a significant effect on controlling the salinity gradient energy or osmotic energy generation. Membrane fouling and operating conditions such as temperature have an extreme influence on the efficiency of the PRO processes because of their roles in salt and water transportation through the PRO membranes. In this study, the temperature impact on the power density and the fouling of two industrial semi-permeable membranes in the PRO system was investigated using river and synthetic sea water. Based on the findings, the power densities were 17.1 and 14.2 W/m2 at 5 °C for flat sheet and hollow fiber membranes, respectively. This is the first time that research indicates that power density at low temperature is feasible for generating electricity using PRO processes. These results can be promising for regions with high PRO potential that experience low temperatures most of the year.

scholarly journals Environmental Assessment of the Impacts and Benefits of a Salinity Gradient Energy Pilot Plant

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3252
Author(s):  
Etzaguery Marin-Coria ◽  
Rodolfo Silva ◽  
Cecilia Enriquez ◽  
M. Luisa Martínez ◽  
Edgar Mendoza
Keyword(s):  
Environmental Impacts ◽  
Salinity Gradient ◽  
Small Scale ◽  
Ecosystem Responses ◽  
Pressure Retarded Osmosis ◽  
Stage Scheme ◽  
Gradient Energy ◽  
Inducing Factors ◽  
Local Impacts ◽  
Construction Operation

Although the technologies involved in converting saline gradient energy (SGE) are rapidly developing, few studies have focused on evaluating possible environmental impacts. In this work, the environmental impacts of a hypothetical 50 kW RED plant installed in La Carbonera Lagoon, Yucatan, Mexico, are addressed. The theoretical support was taken from a literature review and analysis of the components involved in the pressure retarded osmosis (PRO) and reverse electrodialysis (RED) technologies. The study was performed under a three-stage scheme (construction, operation, and dismantling) for which the stress-inducing factors that can drive changes in environmental elements (receptors) were determined. In turn, the possible modifications to the dynamics of the ecosystem (responses) were assessed. Since it is a small-scale energy plant, only local impacts are expected. This study shows that a well-designed SGE plant can have a low environmental impact and also be of benefit to local ecotourism and ecosystem conservation while contributing to a clean, renewable energy supply. Moreover, the same plant in another location in the same system could lead to huge modifications to the flows and resident times of the coastal lagoon water, causing great damage to the biotic and abiotic environment.

scholarly journals Analysis of the Intake Locations of Salinity Gradient Plants Using Hydrodynamic and Membrane Models

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1133
Author(s):  
Jacobo M. Salamanca ◽  
Oscar Álvarez-Silva ◽  
Aldemar Higgins ◽  
Fernando Tadeo
Keyword(s):  
Salinity Gradient ◽  
Water Discharge ◽  
River Mouth ◽  
Power Production ◽  
Discharge Data ◽  
Pressure Retarded Osmosis ◽  
Higher Power ◽  
Magdalena River ◽  
River Mouths

The gain in net power produced by Salinity Gradient plants in river mouths due to the optimal location of water intakes is analysed in this paper. More precisely, this work focuses on stratified river mouths and the membrane-based technology of Pressure-Retarded Osmosis. A methodology for this analysis is proposed and then applied to a case study in Colombia. Temperature, salinity and water discharge data were gathered at the Magdalena river mouth to develop a hydrodynamic model that represents the salinity profile along the river channel. The net power production of a pressure-retarded osmosis plant is then estimated based on the power produced at membrane level, considering different locations for the saltwater and freshwater intakes. The most adequate locations for the intakes are then deduced by balancing higher power production (due to higher salinity differences between the water intakes) with lower pumping costs (due to shorter pumping distances from the intakes). For the case study analysed, a gain of 14% can be achieved by carefully selecting the water intakes.

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