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We report two different approaches to isolate neutral and cationic mesocate-type metallosupramolecular architectures derived from coinage monovalent ions. For this purpose, we use a thiocarbohydrazone ligand, H2L (1), conveniently tuned with bulky phosphine groups to stabilize the MI ions and prevent ligand crossing to achieve the selective formation of mesocates. The neutral complexes [Cu2(HL)2] (2), [Ag2(HL)2] (3), and [Au2(HL)2] (4) were prepared by an electrochemical method, while the cationic complexes [Cu2(H2L)2](PF6)2 (5), [Cu2(H2L)2](BF4)2 (6), [Ag2(H2L)2](PF6)2 (7), [Ag4(HL)2](NO3)2 (8), and [Au2(H2L)2]Cl2 (9) were obtained by using a metal salt as the precursor. All of the complexes are neutral or cationic dinuclear mesocates, except the silver nitrate derivative, which exhibits a tetranuclear cluster mesocate architecture. The crystal structures of the neutral and cationic copper(I), silver(I), and gold(I) complexes allow us to analyze the influence of synthetic methodology or the counterion role on both the micro- and macrostructures of the mesocates The research leading to these results received funding from FEDER-cofounded grants from Consellería de Cultura, Educación e Ordenación Universitaria, Xunta de Galicia [Grants 2017GRCGI-1682 (ED431C2017/01), 2018GRCGI-1584 (ED431C2018/13), and MetalBIONetwork (ED431D2017/01)], from Ministerio de Ciencia, Innovación y Universidades, METALBIO (Grant CTQ2017-90802-REDT), and from Ministerio de Ciencia e Innovación, MultiMetDRUGS (Grant RED2018-102471-T) and Project PID2021-127531NB-I00 (AEI/10.13039/501100011033/FEDER, UE) SI

We present the first example of a silver double-tetranuclear cluster helicate [Ag4L2]2 obtained from a bisthiosemicarbazone ligand using electrochemical synthesis. This cluster helicate undergoes a rare desulfurization process in chloroform giving rise to a cationic silver dihelicate [Ag2(H2L)2]SO4. This is the first silver mediated desulfurization reaction., FEDER cofunded-grants: from Consellería de Cultura, Educación e Ordenación Universitaria, Xunta de Galicia, 2017 GRC GI-1682 (ED431C 2017/01), 2018 GRC GI-1584 (ED431C 2018/13), MetalBIO Network (ED431D 2017/01), Ministerio de Ciencia, Innovación y Universidades, METALBIO (CTQ2017-90802-REDT) and MultiMetDrugs (RED2018-102471-T).

The title compound 5-methyl-1,3- bis (3-nitrobenzyl)pyrimidine-2,4(1 H ,3 H )-dione was obtained by reaction of thymine with 3-nitrobenzylbromide in the presence of cesium carbonate. Characterization of the product was achieved by NMR spectroscopy and its stability was probed in basic condition using UV-Visible analysis. Furthermore, the molecular structure was confirmed by X-ray diffraction analysis. The compound crystallizes in orthorhombic Pna 21 space group with unit cell parameters a = 14.9594 (15) A, b = 25.711 (3) A, c = 4.5004 (4) A, V = 1731.0 (3) A 3 and Z = 4. The crystal packing of the title compound is stabilized by intermolecular hydrogen bond, π···π and C−H···π stacking interactions. The intermolecular interactions were furthermore analyzed through the mapping of different Hirshfeld surfaces. The two-dimensional fingerprint revealed that the most important contributions to these surfaces come from O···H (37.1%), H···H (24%) and H···C/C···H (22.6%) interactions. The interaction energies stabilizing the crystal packing were calculated and were presented graphically as framework energy diagrams. Finally, the energy-framework analysis reveals that π···π and C−H···π interactions energies are mainly dispersive and are the most important forces in the crystal.

The pressing problems of water scarcity in many parts of the planet make water desalination one of the technological solutions for guaranteeing the fresh water supply. However, desalination processes require high energy consumption, mainly provided by fossil fuels. The integration of renewable energy sources into desalination processes is a promising option for decarbonizing the desalination sector. As most water-scarce regions with access to seawater frequently have high solar irradiation levels, it seems appropriate to exploit the sun to power the desalination process. This work presents the assessment of two integrated solar power and desalination systems regarding efficiency and water production. Two desalination processes (multi-effect distillation and reverse osmosis) are studied for potential coupling with the combined cycle of a central receiver solar plant to produce electricity and freshwater. In the case of the multi-effect distillation plant, it is integrated by replacing the Rankine cycle condenser of the combined cycle. In the case of the reverse osmosis plant, it is powered by the electricity generated from the combined cycle. For this comparison, the 21st of March has been considered as the design point and Almería (in the Southeast of Spain) as the plant location. The results show that the thermal cogeneration option renders a worse outcome (thermal efficiency of 50.2% for LT-MED case) than the decoupled generation of electricity and water (thermal efficiency of 53.3% for RO case), producing 18% less fresh water than the RO configuration (3831 m3/d vs. 4640 m3/d), due to the 6% penalty in the efficiency of the Rankine power cycle in the MED configuration as a result of increasing the condensation temperature from 42.6 °C to 70 °C.

An efficient synthetic protocol was devised for the preparation of five cationic ruthenium-arene complexes bearing imidazol(in)ium-2-dithiocarboxylate ligands from the [RuCl2(p-cymene)]2 dimer and 2 equiv of an NHC·CS2 zwitterion. The reactions proceeded cleanly and swiftly in dichloromethane at room temperature to afford the expected [RuCl(p-cymene)(S2C·NHC)]Cl products in quantitative yields. When the [RuCl2(p-cymene)]2 dimer was reacted with only 1 equiv of a dithiolate betaine under the same experimental conditions, a set of five bimetallic compounds with the generic formula [RuCl(p-cymene)(S2C·NHC)][RuCl3(p-cymene)] was obtained in quantitative yields. These novel, dual anionic and cationic ruthenium-arene complexes were fully characterized by various analytical techniques. NMR titrations showed that the chelation of the dithiocarboxylate ligands to afford [RuCl(p-cymene)(S2C·NHC)]+ cations was quantitative and irreversible. Conversely, the formation of the [RuCl3(p-cymene)]- anion was limited by an equilibrium, and this species readily dissociated into Cl- anions and the [RuCl2(p-cymene)]2 dimer. The position of the equilibrium was strongly influenced by the nature of the solvent and was rather insensitive to the temperature. Two monometallic and two bimetallic complexes cocrystallized with water, and their molecular structures were solved by X-ray diffraction analysis. Crystallography revealed the existence of strong interactions between the azolium ring protons of the cationic complexes and neighboring donor groups from the anions or the solvent. The various compounds under investigation were highly soluble in water. They were all strongly cytotoxic against K562 cancer cells. Furthermore, with a selectivity index of 32.1, the [RuCl(p-cymene)(S2C·SIDip)]Cl complex remarkably targeted the erythroleukemic cells vs mouse splenocytes., info:eu-repo/semantics/published

The hydrolysis of 2-methyl-2 H -1,2,4-benzothiadiazine 1,1-dioxide (2) during crystallization under humidity (85 %) conditions, lead to N -(2-( N -methylsulfamoyl)phenyl)formamide as second step hydrolysis product, identified in the proposed degradation mechanism. Crystal of N -(2-( N -methylsulfamoyl)phenyl)formamide C 8 H 10 N 2 O 3 S (4), was obtained and characterized. The molecular structure determination was carried out with MoKα X-ray and data measured at 100 K. The compound 4 crystallizes in triclinic P 1 space group with unit cell parameters a = 4.8465(4) A, b = 8.1942(9) A, c = 11.8686(13) A, α = 77.080(4)°, β = 82.069(4)°, γ = 80.648(4)°, V = 450.76 (8) A 3 and Z = 2. The crystal structure is stabilized by intramolecular N-H···O and intermolecular C-H···O and N-H···O hydrogen bonds that extended as infinite 1D chain along [100]. Stabilization is also ensured by oxygen-π stacking interaction between the aromatic ring and oxygen of the sulfonamide group. The analysis of intermolecular interactions through the mapping of d norm and shape-index revel that the most significant contributions to the Hirshfeld surface 40.6 and 33.9% are from H···H and O···H contacts, respectively.

The title compound corresponds to an enaminone E isomer in the solid state. X-ray structure shows that this crystallizes in the orthorrombic system, with space group Pna21 with 2 independent molecules in the asymmetric unit in a non-centrosymmetric setting. The CNNC unit forms dihedral angles of 5.9(3)/2.1(3); 19.7(3)/17.6(3)° with the pyrrole and phenol rings for molecules A and B respectively. The main differences between both molecules is the dihedral torsion between rings, their mean planes form dihedral angles of 25.45(15) and 15.38(15)° for the molecules A and B. In the asymmetric unit, molecules are linked by two weak N – H···O hydrogen bonds with set graph-motif

The self-cooling greenhouse is a concept to enable crop cultivation in adversely hot climates. It sacrifices a fraction γ of the incident solar energy to drive a refrigeration system, thus lowering the internal temperature below ambient. Heat is actively rejected to a stream of coolant such as air or water. To maintain availability of sunlight for photosynthesis, γ should be as small as possible. Nonetheless, the laws of thermodynamics dictate a minimum value of γ. Using the approach of endoreversible thermodynamics and the theory of selective blackbody absorbers, we determine ideal minimum values achievable for cases of both thermal and photovoltaic solar collection with and without solar concentration. To achieve an internal temperature 10 °C below that of the incoming coolant, a minimum γ = 0.056 is needed using multicolour absorption at maximum concentration C = 46300 – representing an absolute minimum for either type of solar collection. Without concentration (C = 1) a selective thermal collector permits minimum γ = 0.089 and a single-junction PV solar collector permits minimum γ = 0.15. We discuss briefly implications for development of a real self-cooling greenhouse to approximate the performance of these ideal cases.

Two major themes for the space sector in recent years have been the resurgence of missions to the Moon, facilitating the expansion of human presence into the Solar System, and the rapid growth in CubeSat launches. Lunar missions will play an important role in sustainable space exploration, as discussed in the Global Exploration Roadmap. The Roadmap outlines the next steps for the current and next generation of explorers and reaffirms the interest of 14 space agencies to return to the Moon. Over the past decade, a more daring approach to space innovation and the proliferation of low-cost small satellites have invited commercialization and, subsequently, have accelerated the development of miniaturized technologies and substantially reduced the costs associated with CubeSats. In this context, CubeSats are increasingly being considered as platforms for pioneering missions beyond low-Earth orbit. This paper describes a 3U nanosatellite mission to the Moon, designed as part of the UKSEDS Satellite Design Competition, capable of capturing and analysing details of the lunar environment. To achieve the primary mission objectives, a camera and an infrared spectrometer have been included to relay information about historic lunar landmarks to Earth. The design was developed to be integrated with Open Cosmos' OpenKit and reviewed by experts in the field from SSPI. The paper includes a detailed assessment of the current state of miniaturized instruments and the quality of scientific return which can be achieved by a lunar CubeSat mission. This concludes in an overall feasibility study of lunar CubeSats, a discussion of the current limitations and challenges associated with CubeSat technologies and a framework for future missions.

Desalting brines from Reverse Osmosis (RO) plants is one of the most promising applications of Membrane Distillation (MD) systems. The development of accurate models to predict MD system performances plays a significant role in the design of this kind of industrial applications. In this paper, a commercial-scale Permeate-Gap Membrane Distillation (PGMD) module was modelled by means of two different approaches: Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). Condenser inlet temperature, evaporator inlet temperature, feed flow rate and feed water salt concentration were selected as inputs of the model, while permeate flux and Specific Thermal Energy Consumption (STEC) were chosen as responses. The prediction abilities of both RSM and ANN models were compared with further experimental data by using the Analysis of Variance (ANOVA) and the Root Mean Squared Error (RMSE). The results show that the ANN model is able to predict in a more precise way the behaviour of the module for the whole range of input variables. Thus, ANN model was used to find the optimal operating conditions, for the module operating at feed water salinity of 70 and 105 g/L, concentrations that can be reached when desalting RO brines.

This work presents the evaluation of an innovative system based on vacuum multi-effect membrane distillation modules (V-MEMD) for seawater desalination at pilot scale. This four-effect unit introduces a remarkable modification from previous V-MEMD systems, consisting of the use of the seawater feed flow as cooling in the condenser, rather than a separate circuit. Preheating the feed in the condenser improved heat efficiency (maximum gained output ratio obtained for seawater was 3.2). Maximum distillate fluxes reached 8.5 l h−1 m−2 for hot feed temperature 75 °C and feed flow rate 150 l h−1. Increasing both parameters to raise the productivity was hindered by the inability of the condenser to cope with all the steam generated in previous effects, resulting in overheating and overpressure. Furthermore, a loss of 40% of distillate production was measured due to the increase of seawater cooling temperature by 8 °C along the year. Finally, it was observed that scaling reduced distillate production up to 50%. Acid cleaning successfully removed scaling and restored the performance. Subsequently, the use of an antiscalant as a pre-treatment was sufficient to prevent it.

© 2018 Desalination Publications. All rights reserved. A dual stage PRO process has been proposed for power generation from a salinity gradient across a semi-permeable membrane. Both closed-loop and open-loop dual stage PRO system were evaluated using 2 M NaCl and Dead Sea as draw solutions, whereas the feed solution was either fresh water or seawater. The impact of feed salinity gradient resource and feed pressure on the net power generation and water flux were evaluated. The results showed that power density in stage one reached a maximum amount at ΔP = p/2, but the maximum net power generation occurred at ΔP = p/2. This result was mainly attributed to the variation of net driving pressure in stage one and two of the PRO process. The dual stage PRO process was found to perform better at high osmotic pressure gradient across the PRO membrane, for example when Dead Sea brine or highly concentrated NaCl was the draw solution. Total power generation in the dual stage PRO process was up to 40% higher than that in the conventional PRO process. This outcome was achieved through harvesting the rest of the energy remaining in the diluted draw solution. Therefore, a dual stage PRO process has the potential of maximizing power generation from a salinity gradient resource.

Nine representative [Ru(S2CNEt2)2(diphos)] complexes were prepared in almost quantitative yields (91–97%) from [RuCl2(p-cymene)]2, sodium diethyldithiocarbamate trihydrate, and a diphosphine (dppm, dppe, dppp, dppb, dpppe, dppen, dppbz, dppf, or DPEphos), using a novel, straightforward, one-pot procedure. The recourse to a monomodal microwave reactor was instrumental in reaching the thermodynamic equilibria favoring the targeted monometallic trichelates. All the products were fully characterized by using various analytical techniques and the molecular structures of seven of them were determined by X-ray crystallography. NMR, XRD, and IR spectroscopies evidenced a significant contribution of the thioureide resonance form Et2N+=CS22– to the electronic structure of the 1,1-dithiolate ligand. MS/MS spectrometry showed the formation of phosphine-free [Ru(S2CNEt2)2]+ cations in the gas phase, except when starting from [Ru(S2CNEt2)2(dppbz)]. The activity of the nine complexes was probed in three different catalytic processes, viz., the cyclopropanation of styrene with ethyl diazoacetate, the synthesis of vinyl esters from benzoic acid and 1-hexyne, and the atom transfer radical addition (ATRA) of carbon tetrachloride and methyl methacrylate. In the first two reactions, the saturated trichelates were poorly efficient. This was most likely due to their high stability, which prevented the formation of coordinatively unsaturated species. Contrastingly, with a turnover number of 2000 and an initial turnover frequency of 2080 h–1 for a 0.05 mol% catalyst loading, the [Ru(S2CNEt2)2(dppm)] complex emerged as a very robust, latent ATRA initiator, whose activity matched or outperformed those displayed by the most efficient ruthenium catalysts described so far.

Membrane distillation (MD) is an emerging thermal-based membrane technology that has the capacity to treat a wide range of feed waters, including high salinity brines and wastewater. Compared with pressure-driven processes, MD has the following advantages: low electrical energy consumption, complete removal of non-volatile solutes and ambient operating pressures. On the other hand, membrane fouling and pore wetting remain a challenge holding back its wider industrial implementation. To manage this issue, effective pretreatment and cleaning strategies are essential, as with other membrane processes. Despite the importance of these aspects for achieving a stable and reliable water treatment process, far too little attention has been paid to them in the MD literature. Evidence of this is that a comprehensive review on both membrane cleaning and pretreatment in MD is still lacking, despite the large and growing number of publications related to the technology. In this work, we first provide an overview of the three main types of fouling present in MD: inorganic, organic and biological fouling. After this we review, in detail, the use of pretreatment protocols in a range of MD applications, highlighting their efficacy in preventing fouling and ensuring stable performance. Next, we review the use of state-of-the-art chemical and physical cleaning strategies and discuss the development of ‘self-cleaning’ membranes that are superhydrophobic or omniphobic. Finally, future research directions are suggested, with the aim of helping researchers working in this field to develop membrane distillation technology towards wider commercial implementation.

The feasibility of pressure-retarded osmosis (PRO) for power generation was evaluated with consideration of the energy inputs and losses in the process. The effects of the concentration polarization, reverse salt diffusion, and external resistance at the membrane porous layer were quantified, for the first time, along the membrane module to determine their contributions to the energy loss in the PRO process. Concentration polarization was responsible for up to 40% of the energy loss during the PRO process. However, increasing the PRO membrane modules from 1 to 4 resulted in a variable increase of the energy output depending on the salinity gradient. The energy requirements for draw and feed solution pretreatment were estimated to be over 38% of the total energy inputs. Results showed that coupling seawater (SW) with river water (RW) was unable to generate sufficient energy to compensate for the energy inputs and losses during the PRO process. With 0.39 kwh/m 3 maximum specific energy in the PRO process, the energy yield of reverse osmosis brine (ROB)-wastewater (WW) salinity gradient was slightly greater than the total energy inputs, although using Dead Sea-SW/ROB salinity gradient was more promising. Overall, the primary current limitation is the lack of suitable PRO membranes that can withstand a high hydraulic pressure.

© 2017 Elsevier Ltd This work proposes an analysis of conventional (single stage) and dual stage Closed-Loop Pressure Retarded Osmosis (CLPRO) for power generation from a salinity gradient resource. Model calculations were performed taking into account the influence of operating parameters such as the draw solution concentration, membrane area, and draw solution pressure on the performance of the CLPRO process. Modeling results showed that the dual stage CLPRO process outperformed the conventional CLPRO process and power generation increased 18% by adding a second stage of PRO membrane. Multi-Effect Distillation (MED) was selected for the regeneration of the draw solution taking advantage of an available source of waste heat energy. The performance of MED process has been assessed by investigating two key parameters: the specific thermal consumption and the specific heat transfer area. The model calculations showed that the power generation by the single and dual stage CLPRO was higher than the electrical power consumption by the MED plant. In the case of the power generation obtained by the dual stage CLPRO, it was 95% higher than the electrical power consumption by the MED plant, proving the possibility of using low-grade heat for producing electricity from a salinity gradient resource.

The present study evaluates the feasibility of applying forward osmosis (FO) process for the pretreatment of feed solution to a Multi Stage Flash (MSF) desalination plant. For the first time, real brine reject and real seawater were used as the draw solution and the feed solution, respectively in the FO process. The FO pretreatment is expected to dilute the brine reject and reduce the concentration of divalent ions, which are responsible for scale formation on the surface of heat exchanger in the MSF evaporator unit. The FO experiments were performed at different draw solution temperatures ranging between 25 and 40 °C, different draw and feed solutions flowrates and different membrane orientations. A maximum average membrane flux of 22.3 L/m2·h was reported at a draw solution temperature of 40 °C and 0.8 and 2.0 LPM flow rate of draw and feed solutions, respectively. The experimental results also revealed the process sensitivity to the feed solution temperature. It was found that the average membrane flux in the FO process operating at 0.8 and 2 LPM draw and feed solution flow rates, respectively was 16.9 L/m2·h at 25 °C brine temperature but increased to 22.3 L/m2·h at 40 °C brine temperature. These membrane fluxes resulted in 3% and 8.5% dilution of the draw solution at 25 °C and 40 °C temperatures, respectively. The average membrane flux in the FO mode was equal to that in the PRO mode at low flow rates but it was lower than that in the PRO mode at high flow rates of the feed and draw solutions. The outcomes of the study are very promising with regard to membrane flux and dilution of draw solution. This research is made possible by NPRP award (NPRP10-0117-170176) from Qatar National Research Fund (QNRF). The statements made herein are solely the responsibility of the authors. In addition, the authors wish to thank Qatar Foundation for the financial support provided to one of the co-authors through a graduate sponsorship research award ( GSRA4-2-0402-17013 ). The authors also wish to thank Qatar Electricity and Water Company (QEWC) for the supply of brine. Scopus

In this work, the salinity of permeate obtained with membrane distillation (MD) in pilot scale systems was analyzed. Experiments were performed with three different spiral-wound commercial modules, one from Solar Spring with 10 m2 surface membrane area and two from Aquastill with 7.2 and 24 m2. Intermittent operation meant that high permeate conductivity was measured in the beginning of each experiment, which was gradually decreasing until reaching a constant value (3&ndash, 143 &micro, S&middot, cm&minus, 1 for seawater feed). The final quality reached did not depend on operating conditions, only the time it took to reach it. This can be because the permeate flux dilutes the minimal feed leak taking place through pinholes in the membranes. Larger feed leak through the membrane was observed when operating in vacuum-enhanced air-gap MD configuration (V-AGMD), which is compatible with this explanation. However, for the increase of feed leak with salinity (up to 1.8 M), a conclusive explanation cannot be given. Pore wetting due to crystallization is discarded because the high permeate quality was recovered after washing with distilled water. More studies at higher salinities and also at membrane level are required to investigate this.

A 72 m3/d pilot low-temperature multi-effect distillation plant located at the Plataforma Solar de Almeria has been experimentally characterized at steady state to study the influence of the variation in certain parameters that control the process (the hot water inlet temperature as external thermal energy source and the last effect vapor temperature) on the distillate production, the thermal consumption, and the thermal energy efficiency of the plant. Results allowed characterizing the increase in the water production and the thermal consumption with the increase in the hot water inlet temperature and with the decrease in the last effect vapor temperature. The performance ratio reached its maximum when the last effect vapor temperature ranged from 25 to 35°C, since the temperature difference between effects was lower. The preliminary characterization of this plant provides useful experimental information for design criteria and for the analysis of control strategies of other large-scale MED plant...

© 2016 Balaban Desalination Publications. All rights reserved. Novel desalination approaches are required to provide both drinking and agricultural water as there is ever increasing stress upon precious freshwater resources. It was our hypothesis that a modified Forward Osmosis (FO) process had the potential for production of irrigation water comprising of appropriate concentrations of fertilizers from a seawater feed. Four agents, KNO3, Na2SO4, CaNO3, and MgCl2, plus 35 g/L seawater were used as the draw and feed solutions of the FO process. Net Driving Pressure in the FO process was manipulated either by increasing the concentration of draw solution (FO process) or by increasing feed pressure (Pressure Assisted FO (PAFO) process). A series of nanofiltration (NF) and reverse osmosis (RO) membranes were used for the regeneration of draw solution. The results suggested that a PAFO process was more energy efficient than simple FO, provided the energy relating to the brine flow from the NF/RO membrane for pressurizing the feed solution of PAFO process was used. Furthermore, this study suggested using a mixture of a primary draw solution, MgCl2, and a secondary draw solution, KNO3, for NO3 supply into the irrigation water was preferable. As such, MgCl2 provided the driving force for fresh water extraction while KNO3 was the source of fertilizer in the irrigation water. Results showed that water quality provided by application of a MgCl2 + KNO3 draw solution was better than that from KNO3 or Ca(NO3)2. The concentrations of NO3 and SO4 in irrigation water were within recommended levels when the diluted draw solution was regenerated by a dual stage low-pressure RO process.

Forward Osmosis (FO) has been proposed as an alternative method for seawater desalination, wherein Reverse Osmosis (RO) membrane technology is used for regeneration of the draw solution. Previous studies have indicated that a standalone Reverse Osmosis unit is more energy efficient than a Forward Osmosis-Reverse Osmosis system and as such it was recommended that an FO-RO system was best employed only for the desalination of high salinity seawaters. This study examined FO-RO applicability in more detail by examining the impact of seawater salinity, impact of an Energy Recovery Device (ERD), and the effect of membrane fouling. For comparison purposes, the performance of the FO process was improved to minimize the impact of concentration polarization and optimize the concentration of draw solution. Model calculations revealed that FO-RO was more energy efficient than RO when no Energy Recovery Device was employed. However, results showed there was no significant difference in the power consumption between the FO-RO system and the RO unit at high seawater salinities, particularly when a high efficiency ERD was installed. Moreover, the FO-RO system required more membrane area than conventional a RO unit which may further compromise the FO-RO desalination cost.

Experiments were conducted with a commercial membrane distillation module, which has an air-gap membrane distillation (AGMD) and spiral-wound configuration. Tests were performed simulating the salinity and temperature of the water using as a case study the Albian aquifer in Algeria. Solar thermal energy from a field of stationary flat-plate solar collectors was supplied to the module. The total productivity of the AGMD system was analyzed for different operational conditions and compared with that from the RO system. The effect of brackish water temperature on the energy consumption was scrutinized, and the energy requirements assessed toward the design of a pilot unit for decentralized autonomous solar desalination. Results showed that for producing a higher volume of distillate, module with less surface area is better. Also, it was found that recovery ratio increases linearly with the temperature difference in both modules. The maximum value was 6% for the highest feed flow rate operated in modu...

The coupling of Reverse Electrodialysis with Membrane Distillation is a promising option for the conversion of waste heat into electricity. This study evaluates the performances of the integrated system under different operating conditions, employing validated model and correlations. This work provides a detailed description of the behaviour of a real RED-MD heat engine and indicates the set of inlet concentrations, velocities and equipment size which returns the highest cycle exergy efficiency. These operating conditions were selected for the pilot plant developed within the EU-funded project RED Heat to Power. For the first time, a perspective analysis was also included, considering highly performing RED membranes and future MD module. Relevant results indicate that technological improvements may lead to interesting system performance enhancement, up to an exergy efficiency of 16.5%, which is considerably higher than the values reported in literature so far.

Thermal energy storage tanks are habitually combined with solar thermal fields to improve the dispatchability of these facilities. From the dynamical point of view, the start-up phase is relevant since if the storage device is unloaded in terms of energy or widely stratified, the transitory regime can take long time until reaching the operating point. In this paper, an optimal real-time procedure based on a hierarchical controller for improving the start-up phase is proposed. The hierarchical controller is composed of two layers based on a Model Predictive Control (MPC) technique and Proportional Integer Derivative (PID) controllers. Real experimental tests were performed in a pilot facility located at Plataforma Solar de Almeria (Almeria, Spain). In addition, a comparison in simulation with the typical manual procedure and with two techniques proposed previously in the literature for the same plant is provided. The results demonstrate the benefits obtained by using the proposed method; since it reduces the start-up phase in 34 [min] in comparison with the manual operation, and in 26 and 6 [min] with respect to the two previous techniques.

A performance analysis of a salinity gradient heat engine (SGP-HE) is presented for the conversion of low temperature heat into power via a closed-loop Reverse Electrodialysis (RED) coupled with Multi-Effect Distillation (MED). Mathematical models for the RED and MED systems have been purposely developed in order to investigate the performance of both processes and have been then coupled to analyze the efficiency of the overall integrated system. The influence of the main operating conditions (i.e., solutions concentration and velocity) has been quantified, looking at the power density and conversion efficiency of the RED unit, MED Specific Thermal Consumption (STC) and at the overall system exergy efficiency. Results show how the membrane properties (i.e., electrical resistance, permselectivity, water and salt permeability) dramatically affect the performance of the RED process. In particular, the power density achievable using membranes with optimized features (ideal membranes) can be more than three times higher than that obtained with current reference ion exchange membranes. On the other hand, MED STC is strongly influenced by the available waste heat temperature, feed salinity and recovery ratio to be achieved. Lowest values of STC below 25 kWh/m3 can be reached at 100 °C and 27 effects. Increasing the feed salinity also increases the STC, while an increase in the recovery ratio is beneficial for the thermal efficiency of the system. For the integrated system, a more complex influence of operating parameters has been found, leading to the identification of some favorable operating conditions in which exergy efficiency close to 7% (1.4% thermal) can be achieved for the case of current membranes, and up to almost 31% (6.6% thermal) assuming ideal membrane properties.

Membrane distillation is an attractive technology for solar-powered decentralized desalination that has not yet reached commercial breakthrough on a large scale. The main barriers are energy consumption and cost. Since the latter are mostly related to the former, thermal energy efficiency is key to assessing the potential of the different available membrane distillation systems at a commercial scale. As discussed here, existing membrane distillation technologies use mostly flat sheet membranes in plate and frame and spiral-wound modules. Modules based on hollow fibre membranes are also considered, as well as the concept of multi-effect vacuum membrane distillation for improved heat recovery. The heat efficiency of each system is analysed based on available experimental results. Better internal heat recovery and capacity for upscaling are found to be important elements of distinction which make multi-channelled spiral-wound modules working in air-gap configuration stand out currently, with the lowest heat consumption of all large scale modules. Potential for improvement of this and other technologies is also discussed, and an estimation based on the associated costs for solar energy is used for establishing boundary conditions towards the implementation of membrane distillation for solar desalination.

In this paper, an expert-guided kinodynamic RRT algorithm (EGK-RRT) is presented. It aims to consider how a human pilot would navigate a kinodynamic robot. One of the characteristics of this algorithm is the fact that, unlike the original RRT for kinodynamic systems, it generates deterministic control sequences which can be reproduced as long as the sequence of references (sampled states) are known. Here, the performance of the proposed algorithm is tested against the basic RRT, showing that the EGK-RRT greatly improves in terms of execution speed. In addition to this, the influence of using a visibility check and an inertia estimation in order to select the nearest neighbor is also analyzed, demonstrating that a combination of both factors leads to a better overall performance, both in execution speed and in quality of the generated path.

A dual stage pressure retarded osmosis (PRO) process was investigated for power generation using different types of membranes. Polyamide (PA) and cellulose triacetate (CTA) membranes were used in the first and second stage of the PRO process to improve the process performance due to the high water permeability of PA membranes. A comparison between dual stage PA–CTA and CTA–CTA membrane systems were carried out using seawater as a draw solution, while fresh water and wastewater effluent were the feed solution in the first and second stage of the process. The impact of draw solution flow rate on the process performance was evaluated. The performance of first and second stage of the PRO process increased by 11.5 and 28.6%, respectively, when the draw solution flow rate increased by a factor of 2.5. In return, there was a negligible increase in the total specific power consumption of the PRO process. In general, power consumption of the dual stage PRO process was as low as 0.3 kWh/m3. Furthermore, the...

Two-stage forward osmosis (FO)–reverse osmosis (RO)/BWRO and conventional RO/BWRO processes were evaluated for saline water treatment. Three different salts, NaCl, MgCl2 and MgSO4, were used as a draw solution. The performance of FO, RO and BWRO regeneration processes was simulated using predeveloped software. The simulation results showed that the water and solute flux across the FO membrane decreased with increasing the FO recovery rate. The highest water flux was in case of 1.2 mol NaCl draw solution for seawater desalination. The total power consumption for seawater desalination was lower in the RO process than in the FO–RO process. However, as the RO recovery rate increased, the difference in total power consumption between the conventional RO process and 0.65 mol MgCl2 FO–RO processes was insignificant. In case of brackish water desalination, the lowest specific power consumption and permeate TDS were in case of the conventional BWRO process and then followed by 0.32 mol MgSO4, 0.22 mol MgCl...

This work presents the development of a feedback control system for a pilot membrane distillation facility powered with solar energy located at Plataforma Solar de Almeria (PSA), Spain. The control system allows to fix a suitable operating temperature at the inlet of the distillation system, improving the operation quality. Four direct control schemes based on Proportional Integral (PI) controllers and Feedforward (FF) are designed as well as a reference governor which generates temperature references for the heat generation circuit direct control layer. Simulations and experimental tests are shown to demonstrate the effectiveness of the proposed scheme.

This paper presents an optimal operation strategy in terms of thermal efficiency and distillate flux production for a Solar Membrane Distillation (SMD) system. Firstly, a study of the Membrane Distillation (MD) module is presented, revealing the optimal operation strategy. Secondly, a hierarchical control system with two layers is developed and tested. The upper layer consists on a Nonlinear Model Predictive Control (NMPC) scheme which allows us to obtain the maximum temperature at the inlet of the MD module, by optimizing the use of solar energy. The lower layer is composed by a direct control system that is in charge of reaching the setpoint calculated by the upper layer. Simulation results are shown in order to demonstrate the effectiveness of this control approach.

Although Membrane Distillation (MD) has been extensively studied for desalination, it has other applications like removing all kinds of solutes from water and concentrating non-volatile substances. MD offers the possibility of producing a clean stream while concentrating valuable compounds from waste streams towards their recovery, or emerging contaminants and pathogens present in wastewater in order to facilitate their chemical elimination. This paper analyses the elimination of bacterial spores from contaminated water with MD and the role of MD in the subsequent treatment of the concentrate with photo-Fenton process. The experiments were performed at Plataforma Solar de Almeria (PSA) using a plate and frame bench module with a Permeate Gap Membrane Distillation (PGMD) configuration. Tests were done for two different kinds of spores in two different water matrixes: distilled water with 3.5wt% of sea salts contaminated with spores of Bacillus subtilis (B. subtilis) and wastewater after a secondary treatment and still contaminated with Clostridium sp. spores. An analysis of the permeate was performed in all cases to determine its purity, as well as the concentrated stream and its further treatment in order to assess the benefits of using MD. Results showed a permeate free of spores in all the cases, demonstrating the viability of MD to treat biological contaminated wastewater for further use in agriculture. Moreover, the results obtained after treating the concentrate with photo-Fenton showed a shorter treatment time for the reduction of the spore concentration in the water than that when only photo-Fenton was used.

The evaluation of a novel solar seawater desalination system implemented at the University of Almeria (Spain) is presented. It integrates a solar thermal field based on static collectors and a thermal desalination system based on the vacuum multi-effect membrane distillation technology. The distillation unit has a particular innovation to increase its thermal performance, using a seawater flow to condense the steam and preheat the feed. Experiments were made under different environmental conditions to assess the role of the thermal storage system for minimizing the effect of disturbances in solar radiation. Thermal energy could be delivered at a stable temperature to the distillation module, even with variable solar radiation. A simulation analysis based on a quasi-dynamic model was also performed to evaluate the distillate production profile and the operating time during a typical year considering different temperature setpoints at the inlet of the membrane module (60, 70, and 80 °C). The simulated volume of distilled water generated annually ranged from 41.7 to 70.5 m3, depending on the setpoint. The membrane distillation unit produced water almost uniformly along the year, with an average flux of (5.5 ± 1) l h−1 m−2 at the maximum setpoint, which was proved the most favourable.

© 2014 . A dual stage PRO process is proposed here for power generation using osmotic energy. The process is able to handle a wide range of feed water salinities with different pretreatment requirements in order to reduce the membrane fouling problems. In the current study, the salinity gradient resource consisted of seawater at standard TDS, 35. g/L, while the first stage feed water was brackish water or fresh water and the second stage feed water was wastewater effluent. The diluted seawater from the first stage of PRO process was the draw solution in the second stage of PRO process. The performance of dual stage PRO process was evaluated for a number of brackish water salinities ranged from 1. g/L to 5. g/L. The TDS of wastewater and freshwater was assumed 0.2. g/L. The results showed that a better PRO performance was achieved when the brackish water and the wastewater were introduced in the first stage and the second stage respectively. In case when wastewater and brackish water were introduced in the first and second stage respectively there was about 28% decrease in the second stage permeate flow. The results also showed a decrease in the first stage permeate flow with increasing the feed salinity but the second stage permeate flow increased with increasing the feed salinity. Furthermore the results showed that the first stage maximum power density was achieved at δP=. δπ/2 while the second stage maximum power density was achieved at δP=. δπ/1.5. Unlike the conventional PRO process, it has been found that the impact of feed salinity increase on the performance of dual stage PRO process was insignificant. Finally, the power generation in the dual stage PRO process was higher than that in the conventional PRO process. The difference was equal to the entire amount of power generated in the second stage of PRO process.

In this work, we first show the findings of autopsy performed on the membranes used in the Scarab AB® membrane distillation (MD) system at the solar MD pilot plant in Plataforma Solar de Almeria (PSA) in Spain. The fouling and the damage endured by the MD membranes during intermittent long-term (2010–2013) solar-powered operation in the pilot plant were assessed and characterized. Different cleaning strategies were used to remove the fouling layer and restore the membrane properties. Data regarding relevant membrane characteristics for the MD process, such as contact angle, gas permeability, porosity, liquid entry pressure, mechanical strength, etc., and their relationship with the membrane performance under MD operation were discussed and analyzed. Scanning electron microscopy (SEM) was employed to study the morphology of the fouled and cleaned membranes and characterize the membrane damage. The identified best cleaning procedure was then applied in the MD plant system at PSA. Results suggested that cleaning effectively removed a great part of the fouling and reduced the wetting of the membranes. However, this improvement was offset by the effect of inactive periods during which wetting processes were favored.

The demand of freshwater has surpassed the renewable limit and new water sources are associated with an intensive use of energy. Coincidence between scarcity of water and availability of solar radiation makes solar energy the most suitable option to mitigate the water deficit. This paper analyzes the use of energy for decentralized water production using membrane desalination systems fed with solar energy. An analysis is performed based on experimental results from the most advanced commercial prototypes of different technologies of membrane distillation using various configurations, i.e., air-gap, permeate-gap and vacuum; with flat-plate and spiral-wound membranes. The systems operate with thermal energy, although there is some electrical consumption for pumping and in some cases for sustaining vacuum. The thermal energy requirements per unit volume of water produced are assessed in each case, considering the effect of different operational conditions like the temperature regime and the salinity of the input water.

Together with desalination, reuse of wastewater is considered as a solution to mitigate the water deficit in many areas. Membrane distillation (MD) is a technology increasingly proposed for desalination and water treatment. The process is supposed to produce pure distillate, and this is what this paper evaluates. Biologically contaminated water was used in a commercial prototype of spiral-wound liquid-gap MD coupled with solar thermal energy to assess the suitability of the process for removing pathogens. Tests were done during several hours for different operating conditions. The produced distillate, the rejected concentrated solution and the feed water were monitored through time and samples were taken for microbiological analysis. Results proved the efficiency of solar MD to produce a contaminant-free distillate when Escherichia coli, Fusarium solani and Clostridium sp spores were present in the feed water. Furthermore, in the first two cases the population of biological contaminants in the con...

The use of solar energy to feed the MD desalination process is being evaluated at Plataforma Solar de Almeria, the largest European facility for solar energy research, located in SE Spain. A test bed for the evaluation of membrane distillation modules is under operation coupled to a field of static solar collectors. Different commercial modules and real-scale prototypes are tested in continuous operation and coupled with a solar thermal source, in order to obtain data in conditions closer to real applications than the tests performed at laboratory scale. This particular study shows an evaluation of two different modules using spiral-wound membranes, one with a liquid-gap configuration (built by Solar Spring) and the other with an air-gap configuration (built by Aquastill). An assessment of the influence of the operational parameters in the performance was done within the allowed ranges of operation of each prototype, with special attention to the temperatures and the feed flow rate. Also, the infl...