Solar Desalination Process Research Articles

A Review on Solar Water Distillation Using Sensible and Latent Heat

Energy and water are the two major issues faced by human beings nowadays. Owing to increase in the energy costs and the adverse effect on the environment caused by the burning of fossil fuels, renewable energy sources are being used worldwide to contribute in meeting the energy demand. Renewable energy denotes a clean, nontoxic energy source that cannot be exhausted. The primary renewable energy sources are the sun, wind, biomass, tide, waves and geothermal energy. Harnessing the abundance of solar energy has been one of the most attractive energy alternatives. The development of an efficient and economical solar energy storage system is of major concern. Energy storage plays an important role in conserving available energy and improving its utilization. Electrical energy consumption varies during day time and night time. Solar energy is available only during the day. Hence its applications require efficient thermal energy storage so that the excess heat collected during sunshine hours may be stored for later use during the night time. The main problem while utilizing solar energy is its availability which is often intermittent, variable and unpredictable. These problems can be addressed by the storage of thermal energy. Thermal energy storage (TES) will improve the efficiency and output of solar power.A thermal energy storage system mainly consists of three parts, the storage medium, heat transfer mechanism and containment system. Thermal energy storage (TES) applications have significantly increased because of the increase in the energy prices and environmental regulations. Latent heat storage (LHS) is one of the efficient ways of storing thermal energy. Unlike the sensible heat storage (SHS) method, the latent heat storage method provides much higher storage density with a smaller temperature difference between storing and releasing heat. There are large numbers of phase change materials that melt and solidify at a wide range of temperatures. The reason behind using phase change materials is due to their advantages such as low cost, high storage density and isothermal operation. For the solar desalination process, they are used as a bridge to cross the gap between the energy source, the sun and the desalination unit.

Significance of Transient Exergy Terms in a New Tray Design Solar Desalination Device

An investigation of the transient exergy property term, exergy storage, for a new desalination tray design was performed. It was illustrated that exergy destruction rates provide a means of comparing alternative energy solutions and a measure of their sustainability. To satisfy these objectives one needs accurate calculation of exergy destruction rates. It was confirmed that neglecting the exergy storage term is not a valid approximation for the hourly and daily averaged values of the second law analysis. For a solar desalination system neglecting the exergy storage terms introduced a maximum difference in the exergy destruction rate of 7.4% and a difference of 7.3% in the daily average. In the solar desalination process with energy recovery the second law performance is greater than that for the reverse osmosis (RO) process, the chief competitor, when the exergy storage terms are correctly included in the analysis. The results demonstrate that for variable energy sources such as renewable energy systems, the second law analysis provides a measure of the sustainability of competing system and that the exergy storage terms should be included in the analysis.

Experimental study on a humidification and dehumidification desalination system of solar air heater with evacuated tubes

In this paper, a small scale solar humidification–dehumidification (HDH) experimental setup based on a new kind of solar air heater with all-glass evacuated tubes is designed and tested. Firstly, a new kind of solar air heater with evacuated tubes is designed and tested for the solar HDH desalination process. The test results of solar air heater show that the cut length of efficiency and overall heat loss coefficient is 0.47 and 1.60 respectively, while air flow rate is 140m3/h. Secondly, the humidifier and dehumidifier are designed and optimized by the mathematical design methods. Finally, a desalination pilot plant is designed and built. And then, operation characteristics are tested and analyzed. Test results show that different inlet sprayed water temperature in the pad humidifier from 9°C to 27°C can effectively improve relative humidity of outlet moist air from 89% to 97% and the outlet air temperature from 35°C to 42°C. The results are valuable in the pursuit of the optimal design for a 1000L/day solar HDH desalination system with the new kind of solar air heater.

Dynamic modeling and experimental validation of a water desalination prototype by solar energy using humidification dehumidification process

The present study investigates the dynamic functioning of a new solar desalination process based on the humidification/dehumidification (HD) principle. The design and the principle of working of the desalination system are described. The paper deals with the modeling, simulation aspects, and experimental validation of the main components of the system. Mathematical models were established including the mechanism of heat and mass transfer in the various components. These models use real meteorological data to predict the performance of a thermal solar driven system. Series of experiments were conducted and experimental results were then compared with the simulation results. Our findings showed that the developed models could be used to design and help in predicting the behavior of the installation in various meteorological conditions.

A mathematical programming formulation for temporal flexibility analysis

Realistic chemical processes are often operated in the presence of complex and uncertain dynamics. While an ill designed system may become inoperable due to variations in some process parameters at certain instances, the cumulative effects of temporary disturbances in finite time intervals can also result in serious consequences. The latter issue is studied in the present study on the basis of a novel concept – temporal flexibility. Specifically, the mathematical program used for evaluating the corresponding performance measure is built with a dynamic system model, which usually consists of a set of differential-algebraic equations (DAEs). The numerical technique of differential quadrature (DQ) is adopted to approximate these DAEs with equality constraints. As a result, any solution strategy for the conventional steady-state flexibility analysis is applicable. Two examples, a simple liquid storage tank and a solar thermal driven membrane distillation desalination process, are adopted to demonstrate the usefulness of temporal flexibility analysis. All results obtained in case studies show that the proposed approach is convenient and effective for assessing realistic issues in operating complex dynamic chemical processes.

Study on variation laws of parameters in air bubbling humidification process

ABSTRACT In this paper, the variation laws of parameters in air bubbling humidification of solar desalination process are studied. The experimental system and experimental phenomenon are introduced. The parameters of remaining water quantity, humidifying capacity, and water temperature at any instantaneous time in humidifier are calculated and analyzed under different conditions by differential equations of energy balance and mass balance. The results show that the water temperature and the humidifying capacity are changed significantly with time increased in the initial humidifying stage. The change of these parameters depends on heat supplied to the water in the humidifier, whether the heat is higher or lower than the one absorbed by the water evaporating. If the supplied heat is higher, the water temperature and the humidifying capacity will increase in the initial humidifying stage; otherwise they will decrease or remain unchanged. After a certain time of humidifying, these parameters tend to be stabl...

Modeling, simulation and experimental validation of a pad humidifier used in solar desalination process

Water is an extremely important commodity for the improvement of arid and semi-arid environments. As for the water production technology, desalination techniques based on either thermal or membrane separation methods such as multi-stage flash, multi-effect, vapor compression and reverse osmosis are only reliable for large capacity ranges of 100–50,000 m3/day of freshwater production, inefficient from the view point of energy consumption and generally coupled to fossil fuel sources that have a negative impact on the environment. Hence, for the improvement of these regions it is necessary to shift from fossil fuel usage to some environmentally friendly energy source, such as solar energy, as it is available abundantly in such environments. The aim of the present paper is to study numerically and experimentally a pad humidifier used in a seawater solar desalination unit based on humidification–dehumidification principle. The pad humidifier dynamic modeling is based on various heat and mass balance equations. The effect of operating parameters on the pad humidifier characteristics has been investigated. To validate the computer program, a comparison between the experimental and theoretical results was conducted, and a good agreement had been obtained.

Preliminary thermoeconomic analysis of combined parabolic trough solar power and desalination plant in port Safaga (Egypt)

The development of society is strongly dependent on water and electricity. There is an increasing water and energy demand driven by population growth and rising industrial and agricultural production. The combination of concentrated solar power (CSP) and desalination processes has a huge potential for producing both energy and water in arid regions suffering from fresh water scarcity and facing the current energy challenge. One of the regions is Middle East and North Africa (MENA), where plans are currently under discussion to make possible large CSP plants developments. The integration of desalination (CSP+D) into solar power plants could make CSP technology even more attractive in such regions. The focus of this study is thermodynamic characterization and an economic evaluation of different configurations for coupling parabolic trough solar power plants and desalination facilities at a MENA location in Egypt chosen as reference for its Southern coast (Port Safaga). The desalination technologies considered for the combination with parabolic trough concentrating solar power plants (PT-CSP), are low temperature multi-effect distillation (LT-MED) and reverse osmosis (RO). Moreover, an additional concept of LT-MED has been evaluated: a LT-MED powered by the steam obtained from a thermal vapor compressor (TVC). In this case, unlike the conventional thermal vapor compression process (TVC-MED), the entrained vapor to be used in the ejector comes from the exhaust steam from the low pressure (LP) turbine instead of an effect of the MED unit. In order to optimize this latter concept (LT-MED-TVC), different configuration schemes have been studied. When thermodynamic efficiencies and costs are analyzed comparing the two more efficient configurations (PT-CSP/RO and PT-CSP/LT-MED), considering 58°C/0.18 bar of exhaust turbine steam conditions and 5.5 kWh/m3 of RO power requirements, initial results are very similar.

Design, Fabrication, and Performance Evaluation of Double Slope Active Solar Still under Forced Circulation Mode

Water is fundamental to human life on earth for survival and good health. Access to safe water is a major challenge in many communities in developing countries. As world population and social-economic growth, societies are challenged to provide fresh water to meet those needs for all of their people. Growing demands of freshwater resources are creating an urgent need to develop self sustained system to meet the demand of fresh water. Among the available purification technologies, solar desalination process proves to be a suitable solution for resolving this existing crisis. This renewable energy technology operates on a basic principle of solar water distillation. The sun’s energy heat increases the rate of evaporation. As the water evaporates, water vapor rises and condenses on the glass surface for collection. This process removes impurities such as salts and heavy metals as well as eliminates microbiological organisms. In this study, a basin type double slope active solar still under forced circulation mode was designed and fabricated, and a performance evaluation were carried out for different water depths viz 0.03 m, 0.04 m and 0.05 m. The distillate output is maximum 4.82 kg for water depth 0.03 m and minimum 4.36 kg for water depth 0.05 m. The maximum instantaneous thermal efficiency is 46.96 at water depth of 0.04 m.

Solar power-driven humidification–dehumidification (HDH) process for desalination of brackish water

In this study, a photovoltaic (PV) panel-driven humidification–dehumidification (HDH) treatment process was studied for desalination of brackish water under a free or forced convection mode. A bench scale reactor was performed to purify sodium chloride (NaCl)-simulated brackish water. Primary factors affecting the evaporation and condensation rates were evaluated. The water evaporation and condensation mass flow rates were increased with the increasing evaporative brackish water temperature. And the decreasing cooling water temperature increased the water condensation rate. Under their respective optimal conditions, the forced convection mode accomplished a higher freshwater yield than the free convection mode. With the forced convection, the highest freshwater yield was 0.873kg⋅m−2⋅d−1 achieved at the evaporative temperature T0=64.3°C. A preliminary cost analysis showed that the water produced (free convection) from the solar power-driven HDH desalination process had a cost similar to that of drinking water from traditional water treatment plants. This study demonstrated that the HDH treatment was technically and economically feasible for desalination of brackish water.

Thermo-Economic Comparisons of Different Types of Solar Desalination Processes

Many types of desalination technologies are widely used around the worldwide. Thermal and membrane types dominated the market share among the other technologies (freezing, electrodialysis, and ion-exchange). Currently, multistage flash considered the power house of desalination technologies; however, in the last few decades, multi effect distillation and reverse osmosis (RO) technologies were proven as reliable and cost efficient processes. But comparing and electing the most efficient type between conventional desalination technologies is still under scope. It is very hard to decide which type or technique is reliable and thermo-economically efficient. Also, it becomes harder to decide which type is thermo-economically efficient when desalination process is combined with solar energy. In this work, different types of solar desalination processes are thermo-economically compared and analyzed. Results revel that RO and multi effect distillation-thermal vapor compression are recommended according to specific solar area (SSA m2/(m3/d)), total water price (TWP $/m3), thermo-economic product cost (cp $/GJ), and the gain ratio (GR). The comparisons were performed based on two scenarios: (1) different operating conditions due to each individual technology and (2) uniform operating conditions.

EXPERIMENTAL EFFICIENCY INVESTIGATION ON HEAT RECOVERY SYSTEM USED IN A SOLAR-POWERED DESALINATION PROCESS

The aim of this work is to experimentally study, the effect of the heat recovery on water production in a solar desalination process that is working with multiple stage humidification technique. The water production, the temperature and the humidity were tested for such a pilot plant, which operates without and with a heat recovery system. The humidifier efficiency increases with the number of the operating heat exchangers and cannot normally exceed 45% when the system operates without heat exchangers. The air temperature in the heat exchangers decreases by 41.1, 39.2 and 36°C respectively when the system operates with three heat exchangers, tow heat exchangers in the and only one heat exchanger. The number of the heat exchanger use for heat recovery system in such desalination pilot plant has a significant influence on the water productivity. In short, results show that such a pilot plant working without the use of a heat recovery system (heat exchangers) is unable to deliver the desirable minimal amount distilled water at the exit of the condenser. Furthermore, the optimum number of heat exchangers that should be used to upgrade the overall efficiency of the desalination plant is two.

Performances Comparison of Different Solar Desalination Processes by Bubbling Humidification

Basing on the experiment and design data of the two solar desalination systems by bubbling humidification, the GOR (gain output ratio), R (electric power consumption of unit freshwater output) and C (freshwater production cost) are calculated and compared. It's obtained when the humidifying temperature is increased, GOR is increased, while R and C are decreased; if the humidifying temperature increased by 10°C, C would be reduced by half. The electric power consumptions of the systems mainly depend on the blower’s consumption, while the electric power consumed by seawater pumps is little. It is the guide and basis for reducing the freshwater production cost and further improving the rationality of process.

Modeling and experimental validation of a humidification–dehumidification desalination unit solar part

This paper presents the modeling and the experimental validation of air and water solar collectors used in humidification–dehumidification (HDH) solar desalination unit. The solar desalination process is currently operating under the climatological conditions of Sfax (34 N, 10 E), Tunisia. To numerically simulate the air and water solar collectors, we have developed dynamic mathematical models of the solar collectors. The resulting distributed parametric systems of equations are transformed into a system of ordinary differential equations (ODEs) using the orthogonal collocation method (OCM). A comparison between numerical and experimental data was conducted. It was found that the two-temperature mathematical model describes more precisely the real behaviour of the water solar collector than the one-temperature mathematical model. It was also shown that the developed mathematical models are able to predict accurately the trends of the thermal characteristic of the water and air solar collectors. As a result, the proposed models can be used to size and test the behaviour of such a type of water and air solar collectors.

Thermo-economic analysis of a combined solar organic Rankine cycle-reverse osmosis desalination process with different energy recovery configurations

Thermo-economy is a useful and powerful tool that combines thermodynamics and economics. It can evaluate how irreversibility and costs of any process affect the exergoeconomic cost of the product. In this work, a number of comparisons for solar thermal-powered different recovery units for reverse osmosis desalination system are performed using thermo-economic analysis. Three different configurations are used for this comparison (Basic, Pelton Wheel Turbine, and the Pressure Exchanger) with Sharm El-Shiekh RO desalination plant for a total productivity about 145.8 m 3/h (40.5 kg/s). As a result of this analysis, the unit product cost of Pelton Wheel Turbine (PWT) and Pressure Exchanger (PEX) configurations are 24% and 24.2% respectively less than that of the basic configuration. Thermo-economic analysis shows that the minimum investment and operating & maintenance costs are obtained by PEX configuration. Also, it achieves minimum exergy destruction against the two other configurations (Pelton Wheel and Basic systems). Therefore, the final conclusion of this work is that the PEX configuration is more economical than either stand alone or PWT configurations.

A new visual library for design and simulation of solar desalination systems (SDS)

Process simulation has become an accepted tool for the performance, design, and optimization calculations of solar desalination process units. Solving the mathematical models representing these units and systems is a tedious and repetitive problem. Nested iterative procedures are usually needed to solve these models. Also, the process configurations are characterized by existence of a number of recycle streams. To tackle these problems, several researchers have developed different methods, techniques, and computer programs for the simulation of a very wide range of variety of solar desalination process units and systems. It is of interest in this work to show and demonstrate a new program working under Matlab/SimuLink environments for solar desalination processes calculation and modeling. Using these environments a visual design and simulation for different types and configurations of standalone (common) and solar desalination processes can be performed. Embedded user block programming with SimuLink is implemented to construct a flexible reliable and friendly user-interface package. The solar heating systems and desalination plant components (named here as blocks), such as heat exchangers, flash chambers, evaporators, pumps, steam ejector, compressor, reverse osmosis membrane, pipes, etc., are stored as icons in a visual library. This library enables the user to construct different configurations by just clicking the mouse over the required units (blocks). The interface aids designers, and operators to perform different analyses and calculations such as energy, exergy, and thermoeconomics. Typical desalination processes such as multi stage flash, and reverse osmosis are presented to show the wide scope and the validity, reliability, and capability of the developed package.

Performance study on solar still with enhanced condensation

Water scarcity and pollution pose critical situation in all walks of life especially in the developing countries. Among the available purification technologies, solar desalination process proves to be a suitable solution for resolving this existing crisis. This renewable energy technology operates on a basic principle of which the solar radiation enters through the glass surface inside a closed chamber touching the black surface generating heat energy, which gets trapped inside. This gradually raises the temperature of the liquid resulting in evaporation process and further condensation, which is drained out for use. In this connection, a basin type solar still (0.5 m 2) with improved condensation technique was designed and built, and a performance study was carried out with different samples such as tap water, seawater and dairy industry effluent. The condensation occurs due to the temperature difference not only on the glass surface but also on the four sidewalls, which can be cooled by water circulation through tubes attached on the wall surface for efficiency enhancement. The maximum daily production of the solar still was about 1.4 L/m 2.d, and its efficiency was about 30%. The condensate water quality was analysed and compared with water quality standards, which was found to be comparable with rainwater and mineral water. Efficiency of the still was calculated for all the samples and compared with each other. The reasons for the findings and their implications for the design of the system are discussed. Some design features that would further enhance the thermal performance of the still were also identified from this present investigation and highlighted.

Two-stage solar multi-effect humidification dehumidification desalination process plotted from pinch analysis

This paper presents a two-stage solar multi-effect humidification dehumidification desalination process plotted from pinch analysis. The sketch of two-stage solar multi-effect humidification dehumidification desalination process is given. The solar vacuated tube collector is employed in the desalination system, multi-effect humidification dehumidification desalination (HDD) process are plotted two different temperature range according to pinch technology. The higher temperature range is from 60 to 80°C, and the lower is from 30 to 60°C. The mass flow rates of dry air in the two stage desalination units are different. The pinch analysis chart is given. According to the pinch chart, the energy recover rate could get higher according to working temperature range. The research proves that the multi-effect HDD has much room to be improved.

Performance optimization of solar multi-stage flash desalination process using Pinch technology

This paper presents a performance optimization of solar multi-stage flash (MSF) desalination process using Pinch technology. Three different situations were studied by using pinch analysis in this paper, respectively. Firstly, the distilled water is not discharged in each middle stage. Secondly, the distilled water is discharged in each stage. Thirdly, the distilled water is discharged every 5 stages. Pinch charts at different situations are given. At the same stage temperature difference (2 k) and pinch point temperature difference (2 k), the first situation has a higher gain output rate (GOR), about 17.5, and the second and third have lower GOR, around 9. However, GOR is easily influenced by abnormal stage temperature difference at the first situation, and but not in the second and third. The GOR rests on the working temperature range of MSF and the sum of both the maximum stage temperature difference and pinch point temperature difference. To enhance the GOR, it is suggested that we should use the wide working temperature range of MSF, not pumped out the distilled water at middle stages, and keep the same stage temperature difference without fluctuate.

A hybrid solar desalination process of the multi-effect humidification dehumidification and basin-type unit

This paper presents a hybrid solar desalination process of the multi-effect humidification dehumidification and the basin-type unit. The sketch of the hybrid solar desalination process is given. The solar vacuated tube collector is employed in the desalination system, multi-effect humidification dehumidification desalination (HDD) process is plotted according to pinch technology, and then the water rejected from multi-effect HDD process is reused to desalinate in a basin-type unit further. The gain output ratio (GOR) of this system will rise by 2–3 at least through reusing the rejected water. The research proves that the multi-effect HDD has much room to be improved. A hybrid solar desalination process of the multi-effect humidification dehumidification and the basin-type unit should be noticed.