Comparison of solar RO and solar thermal desalination systems

In this paper the unit water costs from 100m³/day solar RO and solar distillation plants are compared. RO plants powered by photovoltaic cells are already available, and distillation plants operated from solar collectors are being constructed. For the size chosen and these options it is concluded that distillation is cheaper than RO for salinities above about 6,000ppm.Solar ponds can provide both thermal and electrical energy more cheaply than the above options, but they do not yet have the market penetration of the more accepted systems. If solar ponds are used then distillation is cheaper than RO only for salinities above about 10,000ppm.     

Development of a marine osmotic solar still for sea water desalination

This paper describes the principals of an approach to desalt sea water via exploitation of solar energy and membrane technology. The approach has been under test aimed at commercialization of the process in the near future. The process is a combination of diffusion across a salinity gradient established by evaporation and distillation in the form of a solar still-type arrangement. An osmotic membrane is used to separate the liquids of different solid concentration. In other words, the desalination devise is a hybrid of a solar still and osmosis unit which could operate in an economical and efficient utilization of solar energy.The marine osmotic solar still does not have the complexity of a solar powered reverse osmosis that draws power from an active solar collection system. Solar collectors and associated energy delivery systems, if used with an RO unit, will be rather expensive, and will occupy a large space. Conventional solar stills occupy large space and are rather inefficient in water production. The marine osmotic solar still is a stand alone solar energy system which is capable of providing distilled water of high purity. It can also be constructed offshore or on land near the seashore.The offshore scheme involves floating units in contact with the sea water. Each is capable of producing 150 gallons of water containing less than 50 ppm of dissolved solid. A conceptual design has been developed and described here of a pilot plant that produces 6,000 gpd.Material tests have been conducted in Singapore and Malysia to assure proper selection of structural material that are suitable for the highly corrosive environment. Measurements on flow rate have shown values of 15 to 20 gallones per square foot per day. The measurements have been conducted in Long Island Sound off Southport, Connecticut.In this paper, the actual design of the plant is described and results of material tests and simulation system analysis are reported. A comparison is made with conventional solar stills and solar powered membrane desalination processes. Results of an extensive marketing research are reported for various applications of the process.     

Development of a Membrane Distillation module for solar energy seawater desalination

Membrane Distillation (MD) processes are gaining growing interest among novel desalination technologies, in particular for small scale applications also coupled with non-conventional energy sources. In the present work an original laboratory scale planar geometry Membrane Distillation unit was designed, built and tested for future coupling with solar energy. Though conceptually simple, the original geometry was developed in order to allow for multi-stage arrangement, compactness, internal heat recovery and possible integration with a polymeric heat exchanger for final brine heating by means of solar energy or waste heat. The laboratory scale unit was tested in order to investigate the effect of operating conditions, i.e. hot feed temperature and flow rate, on the process performance, with particular attention paid to parameters relevant to the design of the system coupled with solar energy. Also the effect of different airgap configurations was investigated, namely (i) free airgap, (ii) permeate-gap and (iii) partial vacuum airgap arrangements.     

Wind and solar powered reverse osmosis desalination units - design,start up,operating experience

To demonstrate the operation of RO units with GKSS plate modules coupled with unconventional energy supply systems, two projects are presently carried out by the GKSS research center applying a photovoltaic solar generator and a wind energy converter for a site in the Northern part of Mexico and a small island at the German coast of the North Sea, respectively. The solar generator with a designed peak power of 2.5 kW is developed by AEG and powers a RO unit for the desalination of brackish well water. The plant has been installed in Concepcion del Oro, Zacatecas, in spring 1980 and has been operated by the Mexican company DIGAASES in cooperation with AEG and GKSS since May 1980. The second project is a 6 kw-wind energy converter supplying 3 RO-modules with a total membrane area of 30 m². After comprehensive component tests at the GKSS research center at Geesthacht the plant was installed at the very small island of Sūderoog at the German coast of the North Sea. Test operation was started in December 1980. For both plants a measurement program has been started.     

Studies on a single-stage solar desalination system for domestic applications

In this paper, an attempt has been made to study a single stage solar desalination system to get a daily yield of 10 1 of potable water. The experimental system consists of a flat plate collector, an evaporator, a single stage vacuum pump and a condenser. The input parameters such as solar irradiance and vacuum pressure in the flash evaporator are varied to find its influence on the performance output viz., system efficiency and yield per day. Efficiency of this plant is found to vary from 15% to 26% for the variation in beam solar radiation from 400 W/m² to 900 W/m². A maximum distillate yield of 8.5 1/d is obtained with collector area of 2 m². The frequency of operation of the vacuum pump and the yield of desalinated water for various beam solar radiations is carried out from which the cost of water is determined. The cost of desalinated water is found to be 0.9 e/l. The desalinated water is tested for various parameters and the results indicate that the quality of water is satisfactory and well below the permissible limits.     

A modeling framework for design of nonlinear renewable energy systems through integrated simulation modeling and metaheuristic optimization: Applications to biorefineries

This study presents the development and implementation of a novel framework for optimal design of new and emerging renewable energy production systems by considering an iterative strategy which integrates the Net Present Value optimization along with detailed mechanistic modeling, simulation, and process optimization which yields optimal capacity plan, and operating conditions for the process. Due to the non-linear nature of process conversion mechanisms, metaheuristic algorithms are implemented in the framework to optimize operating conditions of process. Further, to apply complex kinetics in the process, we have made a linkage between process simulator (Aspen Plus) and Matlab. To demonstrate the effectiveness of the proposed methodology, a hypothetical case study of a lignocellulosic biorefinery is utilized. The proposed framework results reveal a deviation in optimal process yields and production capacities from initial literature estimates. These results indicate the importance of developing a multi-layered framework to optimally design a renewable energy production system.     

A multi-paradigm modeling framework for energy systems simulation and analysis

The modern world energy system is highly complex and interconnected and the effects of energy policies may have unintended consequences. Modeling and analysis tools can therefore be crucial to gaining insight into the interactions between system components and formulating policies that will shape the future energy system. We present in this work a multi-paradigm modeling framework that allows for the continual adjustment and refinement of energy system models as the understanding of the system under study increases. This flexible and open framework allows for the consideration of different levels of model aggregation, timescales and geographic considerations within the same model through the use of different modeling formalisms. We also present a case study of the combined California natural gas and electricity systems that illustrates how the framework may be used to account for the significant uncertainty that exists within the system.     

Experimental study of a multiple-effect humidification solar desalination technique

The object of this research is to experimentally investigate the principal operating parameters of a new desalination process working with an air multiple-effect humidification-dehumidification method. A test set-up was designed and constructed to carry out and optimize this technique. The main parts of the present set-up consist of a heat equipment device (heat exchanger), a spray humidifier and a dehumidifier system. This equipment was used to simulate the seawater desalination process experimentally with an eight-stage air solar collector heating-humidifying system. The outlet temperature of the air solar collector was correlated for use in the desalination process as a solar heating device. The operating conditions studied were: ratio of water to dry air mass flow rate through the system, humidifier inlet absolute humidity, dry air mass flow rate through the system and solar irradiation or humidifier inlet air temperature. The experimental results obtained were used to put stress and correlate the influence of the different operating conditions on the behavior of the eight-stage air heating-humidifying desalination process. The ratio of water to dry air mass flow rates was optimized, precisely 45%. The value of dry air mass flow rate through the system can be also varied with solar radiation in order to have a maximum of humidity content at the end of the system and though working in an adiabatic humidification process.     

First-principles modeling for optimal design,operation, and integration of energy conversion and storage systems

Energy and electricity consumption is expected to increase in the foreseeable future. Concurrently, sustainability concerns of fossil-based energy resources have motivated the use of renewable and reusable energy resources, and the use of more efficient energy-converting and energy-consuming systems. Consequently, for the past decade, there have been major theoretical and experimental advances in (1) energy generation from renewable and reusable resources and (2) energy-consuming and energy-converting devices. This review article focuses on the recent theoretical advances in renewable energy conversion devices such as photovoltaic and fuel cells, and in energy storage devices such as rechargeable batteries, flow batteries, and supercapacitors. Due to similar chemistry, electrochemistry, and physics of these systems, modeling similarities between different energy systems are highlighted. This review puts into perspective how first-principles mathematical modeling has contributed to systematic advances in the optimal design, operation, and integration of these systems. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16482 2019     

Application of a design computer code to determine the off-design characteristics of the Gibraltar vertical tube evaporator desalination plant

A technique has been developed to use the computer program MULT-EFFECT to assess the performance of an evaporator desalination plant under conditions other than those for which it was designed. As an example of the method, a detailed study of the predicted behaviour of the Gibraltar VTE plant has been made for a variety of off-design conditions.This report discusses the philosophy underlying the technique, and presents the results obtained for the Gibraltar study.     

太阳能海水淡化与空调装置控制系统研究

阐述了太阳能海水淡化与组合式空调系统的原理,该系统具有高效的海水淡化功能和空调除湿能力.比较了多个现有的控制器,对该装置的控制系统做出了初步设计并进行了实验验证.最终的实验结果证实该控制器完全可行.     

基于热力蒸汽压缩蒸发的油田污水淡化系统及分析

针对油田污水污染物成分复杂、污染性强不适合膜法脱盐的特点和淡水消耗与余热资源共存的实际,提出用热力蒸汽压缩（TVC）蒸发技术对油田污水进行集中脱盐处理的技术方案。建立了基于TVC的油田污水脱盐系统的工艺流程设计计算模型,系统分析了蒸发温度等主要运行参数的影响。结果表明：系统性能系数随蒸发温度的降低而增大,降低蒸发温度有助于减少主蒸汽消耗,但所付出的代价是总传热面积和污水泵流量的增大;TVC系统的热力学完善度相对较低,与多效蒸发系统联合使用是改善系统性能的基本途径之一。尽管如此,对于油田生产来说,当存在合适的余热资源时,简单的单效TVC系统仍不失为合理的技术方案。     

基于机械蒸汽压缩蒸发的油田污水脱盐系统及分析

针对油田污水污染物成分复杂、污染性强不适合膜法脱盐的特点,提出用机械蒸汽压缩蒸发（MVC）技术对油田污水进行脱盐处理的技术方案。建立了基于MVC的油田污水脱盐系统的工艺流程设计计算模型,系统分析了降膜蒸发器传热温差、油田污水温度和蒸发温度的影响。结果表明：传热温差是影响系统装置规模和运行电耗的控制因素,减小传热温差可以明显降低压缩机比电耗,付出的代价是系统比传热面积的增大;MVC系统的热力完善度高,无废热排放,油田污水温度越高,系统比传热面积减小;在其他条件允许的条件下,提高系统的运行温度有利于改善系统的性能。     

Mathematical modeling and simulation studies of scale-down fermentation systems

In this study, a scale-down approach has been used for the simulation of the imperfect mixing on the growth processes by considering several configurations of continuous stirred tank reactor (CSTR, aerated) and plug flow tubular reactor (PFTR, not aerated). The steady-state concentrations of biomass and enzyme in a continuous culture were calculated as a function of dilution rate using modified Monod growth kinetics. A mathematical model for each combination of two bioreactors was developed to account for growth, substrate utilization (oxygen and glucose) and enzyme synthesis and decay. The model was then used to investigate biomass production and enzyme expression in relation to the volumetric fraction U_f = V_PFTR /(V_CSTR + V_PFTR ) and the recirculation ratio R = f_r/(f + f_r) of the fermentation system. These two mixing parameters were found to be significant factors in the biomass and enzyme production from the fermentation system. This model was also compared with some of the existing models.     

Comparison of solar thermal technologies for applications in seawater desalination

This paper deals with a global analysis of the use of solar energy in seawater distillation under Spanish climatic conditions. Static solar technologies as well as one-axis sun tracking were compared. Different temperature ranges of the thermal energy supply required for a desalination process were considered. At each temperature range, suitable solar collectors were compared in some aspects as: (1) fresh water production from a given desalination plant; (2) attainable fresh water production if a heat pump is coupled to the solar desalination system; (3) area of solar collector required for equivalent energy production. Results showed that direct steam generation (DSG) parabolic troughs are a promising technology for solar-assisted seawater desalination.     

Development of a multi-scale simulation method for design of novel multiphase reactors

In this paper a multi-scale simulation method for modelling dispersions in a novel multiphase reactor is presented. This novel reactor is a continuous reactor which consists of repeated identical small mixing elements. The reactor is excellent for studying the effect of turbulence on drop size distributions since turbulence is continuously produced and dissipated along the reactor. Furthermore the energy dissipation within each element is very homogeneous. In addition it allows optical access at all positions along the reactor.Simulations were performed for a wide range of turbulence intensities for different dispersed phase hold-up. Each simulation was validated with measurements of the size distribution along the reactor. Good quantitative agreement was obtained at low hold-up in terms of prediction of the breakage rates and prediction of the size distributions. At higher hold-up the model gave reasonable predictions at low turbulence intensity however too large drops were predicted at high turbulence intensity. This can be a result of turbulence modulation and shows that reliable turbulence models for multiphase flows are necessary in this simulation method. The results show that physical models describing breakup and coalescence combined with CFD provide a good tool for efficient development and optimisation of novel multiphase reactors.     

Development of a new asymmetric alloy membrane for water desalination

The preparation of a novel asymmetric membrane cast from a poly (4-vinylpyridine) and cellulose acetate homogeneous mixture is discussed. The two polymers were found to be miscible in concentrated solutions. Asymmetric membranes were cast from a sexted dope mixture containing: chloroform, methanol, acetone and formamide. The as-cast solution, when coagulated in water at ambient temperature, yields a highly plasticized asymmetric matrix which, upon slow diffusion of the chloroform into the water, solidifies into a glassy state. The membranes following this stage, do not require annealing and yield high fluxes and salt rejection when tested in reverse osmosis. The asymmetric morphology was confirmed by scanning electron microscopy studies which revealed a dense skin resting upon a highly porous, open-celled, foam-like structure. This structure retains its original wet dimensions upon drying. Brief attempts to quaternize the matrix are also reported.     

甲基异丙基甲酮-苯酚-对苯二酚-水的液液相平衡数据测定、模型关联及萃取过程模拟

液液相平衡测定为溶剂萃取及回收的准确模拟、设计和过程开发提供基础数据。以甲基异丙基甲酮为萃取剂,在处理高浓煤化工含酚废水的三元液液相平衡萃取基础上,选定其中典型单元酚苯酚和多元酚对苯二酚为代表物,测定甲基异丙基甲酮-苯酚-对苯二酚-水在常压40℃下的液液相平衡数据。采用NRTL和UNIQUAC活度系数模型对实验数据进行热力学关联,回归得到该四元体系的二元交互作用参数。结果表明该模型可以很好地关联实验数据,两种模型的相对均方根偏差分别小于0.190%和0.266%。进一步将得到的二元交互参数导入流程模拟系统,对萃取单元模块进行计算。当萃取温度40℃、萃取级数5级、相比1：7.72时,甲基异丙基甲酮能将总酚12700 mg×L^-1,多元酚4250 mg×L^-1的含酚废水的酚浓度分别降低至300 mg×L^-1和299 mg×L^-1以下。     

Numerical simulation and analysis of a patented desalination and power co-generation cycle

A patented cycle for water desalination and power generation was evaluated with regard to thermal efficiency and water production. The inventor of the patent claimed that the patented cycle provides a thermal efficiency of 41 %, which is higher than current combined water and power generation steam plants. A simulation program was developed to evaluate the thermal efficiency and water productivity of this cycle. Simulation parameters were selected from data provided by the patent as well as data generally used in the design of combined power and desalination plants. Results of the simulation were compared with a simulation of the Jubail-II combined plant. The simulation proved that the patented cycle is far inferior to current dual-purpose MSF desalination plants in terms ofwater production. In addition, the patent was found to have a much lower efficiency than what was claimed by the inventor.