Reverse Osmosis Desalination Research Articles

Developing an efficient explainable artificial intelligence approach for accurate reverse osmosis desalination plant performance prediction: application of SHAP analysis

In recent decades, securing drinkable water sources has become a pressing concern for populations in various regions worldwide. Therefore, to address the growing need for potable water, contemporary water purification technologies can be employed to convert saline sources into drinkable supplies. Therefore, the prediction of important parameters of desalination plants is a key task for designing and implementing these facilities. In this regard, artificial intelligence techniques have proven to be powerful assets in this field. These methods offer an expedited and effective means of estimating effective parameters, thus catalyzing their implementation in real-world scenarios. In this study, the predictive accuracy of six different machine learning models, including Natural Gradient-based Boosting (NGBoost), Adaptive Boosting (AdaBoost), Categorical Boosting (CatBoost), Support vector regression (SVR), Gaussian Process Regression (GPR), and Extremely Randomized Tree (ERT) was evaluated for modelling the parameter of permeate flow as a key element in system efficiency, energy consumption, and water quality using six various input combinations of feed water salt concentration, condenser inlet temperature, feed flow rate, and evaporator inlet temperature. The next phase of this research employed the SHAP interpretability method to illustrate the impact of individual variables on the model's output. Moreover, the predictive performance of the developed frameworks was evaluated using a set of five dependable statistical measures: RMSE, NS, MAE, MAPE and R 2. These indicators were utilized to provide a robust means of gauging the precision of the model's forecasts. A comparative analysis of the outcomes, as measured by the RMSE criteria, revealed that the SVR technique (RMSE = 0.125 L/(h·m2)) exhibited superior performance compared to NGBoost (RMSE = 0.163 L/(h·m2)), AdaBoost (RMSE = 0.219 L/(h·m2)), CatBoost (RMSE = 0.149 L/(h·m2)), GPR (RMSE = 0.156 L/(h·m2)), and ERT (RMSE = 0.167 L/(h·m2)) methodologies in predicting permeate flow rates. The modelling outcomes obtained during the evaluation stage demonstrated the efficacy of the SVR algorithm in enhancing the precision of permeate flow forecasts, utilizing relevant input variables.

Comprehensive analysis of energy saving and high-quality permeate production strategies for a large-scale seawater reverse osmosis desalination plant with diverse process configurations and external resource utilization

Comprehensive analysis of energy saving and high-quality permeate production strategies for a large-scale seawater reverse osmosis desalination plant with diverse process configurations and external resource utilization

Wastewater desalination for irrigation in inland regions

ABSTRACT Desalination using membrane processes is increasingly being implemented in coastal regions of the world to meet the water needs of the growing population. The use of this water treatment option to meet the growing water needs in inland regions, however, is impeded by the cost and regulatory challenges associated with responsible disposal of the concentrate brine. For inland regions of Australia, the use of evaporation ponds (EPs) is the only available brine management option. The high cost associated with construction and the high land requirements for EPs necessitates low waste brine volume production. This desktop study investigated the feasibility of achieving very high water recoveries and very low waste brine volumes in the reverse osmosis desalination of municipal wastewater for irrigation of crops near the inland town of Horsham, Victoria, Australia. Interstage lime and soda ash softening was selected as the means of removal of the scalants that prevent the achievement of high water recovery. It is hoped that this study will provide valuable information to aid in the planning of water reclamation operations for agricultural applications in inland areas at a time of increasing demand for water for food production and forecasts of population growth and climate change.

A rapid-convergent particle swarm optimization approach for multiscale design of high-permeance seawater reverse osmosis systems

Directly solving sophisticated partial differential equation constrained optimization problems is not only extremely time-consuming, but also very hard to find unique optimal solutions. Here, we propose stable and efficient surrogate models for seawater reverse osmosis desalination processes that enable thorough quantitative description of hydrodynamics and local transport characteristics in narrow flow channels. Without iteratively solving complex multi-physics simulation problem taking several hours, the proposed multi-scale design optimization framework significantly reduces the problem complexity by computing the surrogate models in seconds. Moreover, a fast-converging active subspace particle swarm optimization framework is proposed to address the optimal design problem. Compared to the standard particle swarm optimization algorithm, the proposed method enhances the average optimum by 14% and the standard deviation of optimum results for multiple runs is reduced by no less than ten times. The optimized desalination system achieves 9% reduction on energy consumption and 30% improvement on water production efficiency.

A geothermal-based freshwater/cooling system assisted by heat recovery sections: 3E analysis and techno-economic optimization using genetic algorithm

The proposed system uses a dual-loop organic Rankine cycle, a reverse osmosis desalination unit, an absorption cooling unit, and a thermoelectric generator to produce electricity and freshwater for urban areas. A thorough assessment of the system's thermodynamic and economic performance has been conducted, with a parameter-based investigation to assess the effect of key variables on the system performance. The parametric study indicates that rising the geothermal mass flow rate enhances the energy efficiency, but lowers the energy efficiency and affects the cooling requirements. Moreover, the optimum inlet temperature in turbine 1 increases the desalination efficiency up to 105.02 kg/s at 115 °C, and higher temperatures reduce the performance and system efficiency. Adjusting the temperature difference at the pinch point at Evaporator1 is crucial for system efficiency, with trade-offs between freshwater output, expenses, and exergy efficiency. The capability of the system to produce up to 6,048,000 L of potable water daily signifies a monumental leap towards meeting the water demands of nearly 42,000 individuals, based on European consumption standards. Lastly, the application of genetic algorithms in the optimization process results in an exergetic efficiency of 32.79 % and a cost rate of 58.05 $/h, demonstrating the system's enhanced operational effectiveness.

Influence of microbubble two-phase feed flow on reverse osmosis desalination using different salt concentrations

This study aims to implement microbubble two-phase flow in the feed stream to improve mass transfer and achieve improved reverse osmosis (RO) process performance. The swirl-flow microbubble generator (MBG), which can effectively generate microbubbles, is integrated into the conventional RO system and has experimentally proven its performance under various operating conditions. To investigate the influence of microbubbles in the feed stream on the RO process depending on the feed concentration, real seawater and two types of artificial brackish water were used as the feed solution. The formation of microbubble two-phase flows in the feed stream had a positive impact on the transmembrane flux and distillate water quality of the RO process; this demonstrates that improved mass transfer due to microbubbles introduced into the feed can effectively attenuate the concentration polarization effect in the RO process. MBG-RO performance using seawater as the feed solution was found to be more pronounced at lower feed pressures and higher airflow rates, with an improvement in permeation flux of up to 16 %. Meanwhile, the MBG contribution to RO performance was lower when using artificial brackish water with relatively low concentration than that when using seawater.

Development and characterization of an asymmetrical flat microfiltration membrane based on natural phengite clay: Application as a pretreatment for raw seawater reverse osmosis desalination

The work focuses on developing a new asymmetric flat microfiltration membrane using an inexpensive geological material, natural Moroccan phengite clay. The optimal porous ceramic support was prepared by applying the paste casting method and sintering at a low temperature of 1050 °C for 2 h. Secondly, the microfiltration layer was developed by the spin coating method. The layer was then dried and sintered at 850 °C/2h. SEM analysis revealed that the morphological structure of the layer is homogeneous and free from cracks. Furthermore, the microfiltration layer has an average pore size of 1.23 μm, a thickness ranging from 30.3 μm to 31.3 μm, a water permeability of 258.1 L/h.m2.bar, and good chemical stability against corrosion. The performance of the manufactured membrane was evaluated by filtering raw seawater (RSW1 and RSW2) as a potential application for seawater pretreatment before desalination by reverse osmosis. The prepared membrane significantly reduced turbidity concentrations by 98.7 % for RSW1 and 96.8 % for RSW2. The fouling and antifouling mechanisms were also examined. Finally, the preparation cost of the phengite membrane was estimated to be 125 $/m2.

Understanding the fouling characteristics in ultrafiltration membrane for marine algae-laden seawater pretreatment: Focus on the role of algal extracellular organic matter

The increasing frequency and extent of harmful algal blooms (HABs) due to global warming and environmental pollution pose significant challenges to the ultrafiltration (UF)-seawater reverse osmosis (SWRO) desalination process. The UF process is a dominant pretreatment method to reduce HAB fouling potential in subsequent SWRO processes. Herein, we systematically evaluate the UF membrane fouling characteristics at different growth phases of HAB algae in terms of reversible/irreversible fouling and pinpoint the fouling mechanisms on UF membranes in the real seawater matrix. We employed Prorocentrum donghaiense as a model marine HAB specie to characterize algal derivatives, including extracellular organic matter (EOM) and granule particles. LC-OCD, MFIs, 3D-EEM, and GPC were used to analyze algae-derived matters. Results from the multiple fouling model revealed that algal solution in both stationary and decline phases exhibit severe membrane fouling, characterized by rapid cake layer formation, swift flux decline, and high membrane resistance. Soluble EOM (S-EOM) was the primary contributor to membrane fouling, linked to its elevated concentrations of dissolved organic matters, polysaccharides, proteins, and humic substances, which are predominantly hydrophobic. Additionally, granule particles mitigated organic membrane fouling, as evidenced by the smaller permeate volume required for S-EOM cake layer formation (<5 mL), resulting in a faster initial flux decline. These results revealed a shift in released organic matter from protein-centric to humic substance-centric during the transition from exponential growth to the decline phase, with correlation analysis further underscoring the substantial contribution of humic substances to membrane resistance. This research highlights the distinct UF membrane fouling characteristics at different marine algal growth stages, offering theoretical support for predicting and managing HABs.

Multi-criteria optimization next to a comparative analysis of a polygeneration layout based on a double-stage gas turbine cycle fueled by biomass and hydrogen

The significance and advantages of utilizing renewable energy sources are widely recognized. Upon examining past studies, it was revealed that there has been a lack of research on harnessing the waste energy from double-stage gas turbines powered by biomass-hydrogen hybrid fuel for polygeneration applications. Thus, a new configuration is proposed in the study for the multi-production of electricity, cooling, heating, and potable water. In the current research, a high-pressure turbine is driven by a combustion chamber fed by a biomass gasifier. Meanwhile, a low-pressure turbine is driven by a post-combustion chamber fed by hydrogen as fuel. The heat loss of the topping gas turbine cycle is recuperated by a supercritical Brayton cycle (SBC), a steam Rankine cycle (SRC), and a water heater. The waste heat of the supercritical Brayton cycle and steam Rankine cycle is recovered through an absorption refrigeration cycle and a thermoelectric generator, respectively. Thus, the heat loss of the topping system is completely recovered. The net power output of the gas turbine cycle is considered the electricity production of the system while the output power of the SBC and SRC is utilized in a reverse osmosis desalination system to produce potable water. The investigations conducted on the system are thermodynamic and exergy-economic assessments and three-objective optimization utilizing 5 gases (i.e., CO2, CO, Nitrogen, Air, and Helium) in the SBC. The final results reveal the superiority of Helium as the supercritical gas, bringing about an exergy efficiency () of 32.11%, a total cost rate () of 103 , a payback period (PP) of 0.159 years, and a specific cost of polygeneration () of 22.03 for the system. Although the levelized cost of products of the configuration is high due to the freshwater production, of the proposed system is higher than the previous systems based on a double-stage gas turbine cycle driven by biomass and hydrogen.

Oil removal using agricultural wastes adsorbents in a fixed bed column as a pretreatment in RO systems

Oil removal from seawater is an essential pre-treatment in Reverse Osmosis desalination plants to mitigate membrane fouling. The present paper investigates the feasibility of oil removal from water using agricultural wastes as low-cost adsorbents. Three wastes, rice husk, sugarcane bagasse, and sawdust were tested using two types of water, oily seawater and oily distilled water. For comparison, activated carbon adsorbent was included in the tests as a reference case. The experiments were conducted in a fixed bed column (10 cm diameter and 55 cm height), at an initial oil concentration of 1000, 3000, and 5000 mg/L, bed height of 10, 15, and 20 cm, and flow rate of 75, 145, and 290 mL/min. The parametric study indicated that the breakthrough time and the percentage of oil removal increased with the decrease in initial oil concentration and flow rate, but the breakthrough time increases with increasing the bed height. The oil removal percentage using rice husk was higher than sawdust and sugar cane bagasse and it was 18.9 % lower than that of activated carbon. Thus, rice husk can be a cheap alternative to activated carbon. The effect of oil type and water type was not significant. Additionally, the 50 % breakthrough time was 1388 min for activated carbon, 912 min for rice husk, 580 min for sawdust and 421 min for sugar cane bagasse. Assessing the dynamics models indicated that the non-linear forms of the Thomas, Bohart-Adams, and Yoon-and-Nelson kinetic models perform better than their linear forms, and the difference in performance among these models was not so big, i.e., any of these models can be used to predict the breakthrough curve.

Siting Analysis of a Solar-Nuclear-Desalination Integrated Energy System

Nuclear power is typically deployed as a baseload generator. Increased penetration of variable renewables motivates combining nuclear and renewable technologies into Integrated Energy Systems (IES) to improve dispatchability, component synergies and, through cogeneration, address multiple markets. However, combining multiple energy resources heavily depends on the proper selection of each system’s location and design limitations. In this paper, co-siting options for IES that couple nuclear and concentrating solar power (CSP) with thermal desalination are investigated. A comprehensive siting analysis is performed that utilizes global information survey data to determine possible co-siting options for nuclear and solar thermal generation in the United States. Viable co-siting options are distributed across the Southwestern U.S., with the greatest concentration of siting options in the southern Great Plains, although siting with higher solar direct normal irradiance is possible in other states such as Arizona and New Mexico. Brackish water desalination is also attractive across the southwest U.S. due to high water stress, but for brackish water desalination reverse osmosis (an electricity driven process) is most cost- and energy-efficient, which does not require co-siting with the thermal generator. The most attractive state for nuclear and thermal desalination (which is more attractive when using seawater) is Texas, although other areas may become attractive as water stress increases over the coming decades. Co-siting of all CSP and thermal desalination is challenging as attractive CSP sites are not coastal.

Optimized multi-criteria performance of a poly-generation layout including a Stirling engine and a supercritical Brayton cycle using biogas and methane as two potential fuels of a topping gas turbine cycle

The combination of a supercritical Brayton cycle, an absorption chiller, a Stirling engine, a reverse osmosis desalination system, and a proton exchange membrane electrolyzer is investigated for waste heat recovery of a topping gas turbine cycle. The required electricity for hydrogen and freshwater production is supplied by the Stirling engine and supercritical Brayton cycle, respectively. In addition, the output power is provided by the gas turbine cycle, and the exiting cold stream of the Stirling engine is considered hot water for domestic utilization. A comparison is made between biogas and pure methane as two possible fuels for the system. Energy and exergy analyses, economic analysis using the specific exergy costing approach, and environmental analysis considering the carbon dioxide emissions are employed in the study. The three-objective optimization of the configuration discloses an exergy efficiency (ηex) of 39.49 % and 39.85 % in the cases of biogas and methane, respectively. The proposed system can improve ηex by 6.18 % points compared to the stand-alone GTC. The specific cost of poly-generation (cpoly) and the total cost rate (C˙tot) are obtained as 25.92 $GJ−1 and 249.5 $h−1 in the biogas mode, while these values are calculated as 36.75 $GJ−1 and 336.7 $h−1 in the methane case. The environmental cost rate (C˙env) of the system is 24.78 $h−1 in the case of biogas and 17.47 $h−1 in the methane mode. The results confirm the superiority of the methane case from the environmental viewpoint over biogas. However, the low values of cpoly and C˙tot in the biogas case indicate that biogas is superior to methane from a general standpoint. The utilization of the present setup for waste heat recovery of biogas-driven GTCs is recommended due to the higher ηex than the previous layouts.

Mechanisms of electromagnetic field control on mineral scaling in brackish water reverse osmosis: Combined homogenous and heterogeneous nucleation

Electromagnetic field (EMF) treatment has emerged as a promising approach for scaling control due to its cost-effectiveness, simplicity, and low energy consumption. However, there is a limited understanding of the mechanisms by which applied EMF impacts mineral scaling in reverse osmosis (RO) systems. This has led to inconclusive and varied results and uncertainties regarding its effectiveness. This study elucidates the impacts of EMF on homogenous and heterogeneous nucleation and membrane performance during RO desalination of different feedwaters. Our results reveal that EMF exhibits greater efficacy in treating near-saturated water (SI∼0), especially when coupled with extended hydraulic flushing (HF). For saturated brackish water desalination, heterogeneous scaling predominantly occurs on membrane surfaces, with the effectiveness of EMF in inhibiting scaling primarily attributed to the hydration effect. In supersaturated solutions, EMF promotes bulk precipitation due to the magnetohydrodynamic effect, quickly blocking membrane pores. Thus, when the saturation reaches a certain high level during RO desalination, magnetohydrodynamic EMF effects can accelerate flux decline caused by homogeneous scaling. This work provides an efficient method for predicting EMF efficiency, emphasizing the importance of saturation conditions and HF cleaning duration in determining membrane performance, suggesting these show promise for improving undersaturated or near-saturated feedwater desalination via RO.

Techno-economic assessment of vertical axis wind turbine driven RO desalination with compressed air energy storage for remote communities

Renewable energy desalination is gaining much attention in remote off-grid communities facing challenges in accessing clean water. Typically, batteries ensure the continuous operation of small-scale renewable reverse osmosis (RO) desalination systems; however, they are expensive and have relatively shorter lifespans. This study investigates the implementation of a compressed air energy storage (CAES) system coupled with a vertical axis wind turbine (VAWT) to directly drive small-scale RO desalination, potentially replacing batteries and reducing energy conversions. A Simulink model was developed to simulate the performance of a VAWT-driven CAES operating RO units, adaptable for both technical and economic assessments. Parametric studies have identified the optimal configuration. The most cost-effective configuration, utilising eleven VAWTs and a pressure exchanger (PX), achieves a levelised cost of water (LCOW) of 1.63 US$/m3 and an annual water production of 9400 m3. The normalised daily water production per square metre of turbine swept area at the study site is 0.19 m3/m2/day at an average wind speed of 5 m/s. While this configuration has a higher initial capital cost, it yields the lowest LCOW. The CAES system effectively addresses the intermittency challenges of wind energy. This study presents a novel, battery-free VAWT-CAES-RO system as a sustainable desalination solution for remote communities, offering a promising approach to address water scarcity in an environmentally friendly manner.

Development and modeling of power, hydrogen and freshwater production based on a novel double-flash geothermal power plant

In this article, a novel geothermal energy-assisted multigeneration plant is proposed and analyzed from the thermodynamic, economic, and environmental perspectives. In the design of the geothermal power system, a transcritical Rankine cycle, which employs CO2 as the working fluid (tCO2-RC), a Kalina cycle (KC), a hydrogen generation sub-plant, and a desalination unit are considered. The reverse osmosis (RO) desalination process is used for freshwater production, while the proton exchanger membrane (PEM) electrolyzer is utilized for hydrogen generation. In addition, parametric analyses are conducted to ascertain the impacts of the temperature of the geothermal source, mass flow rate, and flash chamber pressure on system performance. According to the results, the plant's overall energetic and exergetic efficiencies are determined to be 8.6 % and 34.9 %, respectively where the net power production is calculated as 3317.94 kW, and the system's total irreversibility is found to be 5852.88 kW. Furthermore, the hourly H2, O2, and freshwater generation amounts are 8.5 kg, 49.1 kg, and 9.3 m3, respectively. Finally, the levelized energy cost (LEC) and sustainability index of the system are found to be 0.128 USD/kWh and 0.215.

Production of boric acid by bipolar membrane electrodialysis: Evaluation of commercial and polyelectrolyte multilayers-coated ion exchange membranes

Boron is an essential element for many industrial sectors, but the European Union (EU) is entirely dependent on imports for its boron supply. To ensure a sustainable supply of boron for the EU, developing recovery strategies from secondary sources is essential. Thus, boron recovery from seawater reverse osmosis (SWRO) desalination brines using bipolar membrane electrodialysis (BMED) as part of a multi-mineral brine mining process is proposed. BMED experiments were conducted with 35 triplets of commercial membranes (100 cm2), using sodium borate solution (92.5 mM) as feed, at three different pHs (2, 9 and 12), identifying pH 12 as the best option. Moreover, commercial ion exchange membranes from PCA GmbH and Mega a.s. were coated with polyelectrolyte multilayers using layer-by-layer technique. Characterization of the coated membranes included zeta potential, contact angle, ATR-FTIR, transport number and ion exchange capacity analyses. Subsequent BMED experiments with three triplets comparing virgin and modified membranes (100 cm2), using sodium borate solution (92.5 mM) as feed, demonstrated that the coating with 4 bilayers increased the selectivity of membranes. Although the coated RALEX membranes presented the highest selectivity (7.2 for B(OH)4-/Na+ in the acid compartment), uncoated PCA membranes were the optimal choice for H3BO3 and NaOH production due to higher Na and B removal (97 %), higher concentration factors (2.5 for the acid and 4.3 for the base), and higher current efficiency for H3BO3 production (78 %).

Assessing RO and NF Desalination Technologies for Irrigation-Grade Water

In this work, the performance of a Reverse Osmosis (RO) process using different types of reverse osmosis (RO) and nanofiltration (NF) membranes is evaluated for brackish water desalination for producing irrigation-grade water. The proposed desalination system is a single-stage system, where three types of RO and two NF membranes were examined. The different desalination systems were simulated using ROSA72 software. In order to validate the theoretical model, the results obtained from the simulation were compared to those obtained from the experiment conducted in this work. The El-Moghra aquifer of Egypt is considered the test bed due to a considerable amount of data being available for this aquifer. The El-Moghra aquifer has 79 wells, and the available water data, when checked against several quality parameters, show that none of the investigated wells are suitable for direct irrigation without treatment due to problems of salinity, the sodium adsorption ratio, and low water quality according to the irrigation water quality index values. The obtained results show that nanofiltration membranes exhibited superior energy efficiency compared to reverse osmosis membranes. However, what sets the nanofiltration membranes apart is their ability to elevate water quality in 89.9% of the total investigated wells to an acceptable level for agricultural purposes. This underscores the nanofiltration membranes as a highly effective alternative to reverse osmosis membranes, demonstrating the capability to produce water suitable for irrigation while concurrently reducing operational costs due to the lower energy consumption in nanofiltration-based systems.

An innovative sustainable multi-generation energy system (electricity, heat, cold, and potable water) based on green hydrogen-fueled engine and dryer

Increasing renewables' portion in energy matrix around the world has made the scientists to propose innovative techniques for recovering the available waste heat of energy systems to produce excess energies in the Waste-to-X framework. This study proposes a green sustainable multi-generation energy system (MES), producing power, heat, cold, and potable water, driven by a hydrogen-fueled gas engine. The engine's heating potential is recovered to run some bottoming systems comprising proton exchange membrane electrolyzer (PEME), absorption/electrical chiller cycles (ACC/ECC), organic Rankine cycle (ORC), dryer unit, heat pump cycle (HPC), and reverse osmosis desalination unit. The combination of ACC with dryer and HPC is an innovative idea which utilized to produce heating load in this study. A detailed sustainability evaluation framework (technical and eco-environment) is derived to approve performance of the MES. The construction feasibility of the MES in different climatic conditions is sought by considering 5 case study cities around the world. Afterwards, best working fluid of the ECC/HPC and ORC is selected and then the sensitivity of the MES performance to design variables is investigated trough a comprehensive parametric study. Results illustrated that the MES shows the best performance in the city of Willington in which the emission of 84.8 tons of CO2 is prevented annually which is equivalent to saving of 16,291.6 m3 natural gas. The working fluid selection outputs proved that considering R22 and R123 for ECC/HPC and ORC leads the best techno-economic performance. The sensitivity study demonstrated that the highest and lowest influence of the MES's techno-economic performance is related to the ECC evaporator and ORC turbine temperatures, respectively. So that, increasing ECC evaporator temperature led to a relative variation of 8.2%, 4.5%, and 7.5% in energy recovery factor, exergy efficiency, and levelized cost of productions, respectively.

Renewable energy-driven desalination for sustainable water production in the Middle East

ABSTRACT Despite significant advancement in conventional desalination technologies, their widespread application is still constrained by high energy demands, high capital costs, and the associated greenhouse gas (GHG) emissions. The main objective of this study is to evaluate the potential and challenges of renewable energy desalination in the Middle East. The study also compared the production of energy and water, and emissions reductions of hypothetical 100 MW renewable energy plants in Kuwait, coupled with reverse osmosis (RO) desalination units. The wind-RO plant is estimated to produce 68 million cubic metres on an annual basis, while the CSP-RO and PV-RO plants produced 44 and 37 million cubic metres of fresh water, respectively. These estimates, however, only account for 5% to 9% of the annual fresh water demand in the reference case. Meeting 100% of the fresh water demand would require a 1000 MW to 2000 MW renewable energy capacity. Overall, the intermittent nature of renewable energy sources is a fundamental barrier to the large-scale transition to renewable energies for desalination. The results of this study indicate that the CSP’s relatively small footprint (compared to wind plants) and higher capacity factor make it an ideal compromise among the proposed plants.

Elucidating the use of pressure-recovery diagrams for analyzing energy consumption in reverse osmosis desalination

The pressure-recovery (PY) diagram used in reverse osmosis (RO) literature to compare energy consumptions in different RO configurations has a flaw of not holding the design flux constant. In this work, the PY diagrams are constructed with the aid of transport models. It is shown that the area underneath the PY curve represents the specific energy consumption (SEC) imposed by design flux and thermodynamics, which may be reduced by improving spatial uniformity in flux. The trend generally observes the equipartition of entropy production theorem. For seawater RO (SWRO) in which pressure drop relative to feed osmotic pressure is small and operation is near the thermodynamic limit, staged designs with interstage booster pumps enable a more uniform flux, thus reducing the SEC. However, for low-salinity brackish water RO (BWRO), improving flux uniformity may lead to a higher SEC as the increased friction loss often outweighs the reduced energy requirement imposed by system flux.