Operation experience with solar powered 10 M3 per day MSF-plant in Kuwait and results of upscaling experiments

This paper reports on the progress which was made in the field of solar desalination in order to obtain reliable equipment capable to both operate under the severe requirements associated with the use of solar energy as a variable source of heat and to yield favourable economic conditions in view of larger scale utilisation of the undepletable source of energy for the generation of fresh water.The results of a 2 year experience with a selfregulating solar MSF desalination plant under the extreme environmental conditions in the middle east will be discussed. A new type of a solar selfregulating fluidized bed MSF desalination unit will be presented for the first time. The new development which has been carried to a mass-production-level is the result of the experience gained in this field over the last years.The operation of the Atlantis desalination unit with different types of solar collection systems, in particular the salt gradient solar pond energy collection and storage system, will be discussed from the technical and economical point of view to demonstrate the feasibility of future larger scale solar desalination.     

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.     

Energy and exergy analyses of seawater desalination system integrated in a solar heat transformer

Among the numerous options to improve the energy efficiency of desalination plants stands out the absorption heat transformer. A heat transformer is a device, which can deliver heat at a higher temperature than the temperature of the fluid by which it is fed. Solar thermal energy can be used as heat input for single effect heat transformer while the high grade thermal energy delivered by the heat transformer can be used as heat source for water desalination.In this paper, an attempt has been made to study the combination: flat plate solar collectors, a single effect heat transformer and desalination system (distillation process) used to provide a beach house located in Skikda (East of Algeria; Latitude 36.52°N, Longitude 6.57°E) with drinking water. This system produces about 500 l of drinking water per day in July.Mathematical models of the solar flat plate collectors (FPC), absorption heat transformer (AHT) operating with the water/lithium bromide solution and the overall desalination system (WP) were developed to simulate the performance of this combination system. The energy and exergy analyses are carried out for each component of the system. All exergy losses that exist in this solar desalination system are calculated. Energy and exergy efficiencies are estimated.     

盘式太阳能蒸馏海水淡化研究进展

综述了近年来盘式太阳能蒸馏器海水淡化技术的研究进展,重点介绍了传统盘式太阳能蒸馏器和双斜面盘式太阳能蒸馏器,以及在此基础上演变出的各种主动式盘式太阳能蒸馏器。认为通过增加外置设备可增大热能利用率,从而有效地增大产水量;新型材料也必将成为今后研究的热点。     

Theoretical study on multi-effect solar distillation system driven by tidal energy

Based on an analysis of the characteristics of solar and tidal energy, an innovative, multi-effect solar distillation unit for seawater desalination utilizing solar and tidal energy has been developed. The uniqueness of the system is that without being transferred to electricity, tidal energy is utilized to supply power for water supply and drainage, and vacuum extraction instead of pumps powered by electricity. So the cost can be greatly reduced. The system is based on multi-effect evaporation-condensation processes and operates under vacuum condition, so low grade solar heat can be used with a high thermal efficiency. Hydrodynamic and thermal analysis is carried out for the water supply and drainage system driven by tidal energy. The operating mechanism of the vacuum extraction system driven by tidal energy is presented. A parametric study of the behavior of the solar desalination unit has been performed.     

A solar multiple effect distiller for Jordan

The potential of desalination as a viable alternate water source for Jordan using a multiple effect distiller (MED), evolved to operate using solar energy under Jordanian conditions is discussed. A computer code in C++ was generated in order to simulate the MED process, and to predict the water production at 10 different Jordanian sites, based on available solar radiation data and salinity of the feed water (TDS of 3000, 5000, 7000, and 10,000 mg/L). It was found that Tafila, Queira, H-4, H-5, and Ras Muneef, are the most favorable sites for installing the proposed solar MED system. With a TDS of 7000 mg/L, the annual water production for these sites was 12,342, 10,950, 10,367, 10,262 and 10,063 m³ respectively. Furthermore, in all of these sites about 63% of the daily amount of water produced during a 1-year cycle occurs during the summer months (April to September), when the water consumption is the highest, and water desalination is a necessity.     

Status of solar assisted desalination: A review

The application of solar assisted desalination is expanding impressively during the last years, hence an overview of this evolution is attempted. The various solar devices, for the conversion of the sun's energy onto heat or electric power are described with emphasis to their application in water desalination processes. The status of the solar assisted desalination as developed the last eight years and the installed plants in commercial or semi-commercial size as well as some plant under development are summarized.     

Design and simulation of a novel solar photovoltaic system assisted single-slope solar still distillation unit

Water is an essential component of our lives. Conventional seawater desalination, based on fossil fuel energy, is primary in meeting freshwater demands. Thus, solar desalination still emerged as an alternative technology that employs environmentally friendly renewable energy. Here, we aim to design and simulate a novel hybrid solar photovoltaic (PV) system coupled with a single-slope solar still unit for freshwater production. Various design techniques were utilized to fine-tune the model towards producing 3–4.6 kg/m² · day of distillate water, thereby calculating the design aspects such as tank size, energy, and cost. The results revealed that a conventional solar desalination system had 22% lower efficiency than the proposed novel still distillation unit assisted with a solar PV system (connected to a heating element). The maximum efficiency of 45% has been recorded at the peak solar insolation due to the combination of the solar PV system. According to our design constraints, only a 3 m² basin area was required to achieve a productivity of ${\mathit{P}}_{\mathit{st}}$ = 1–5 kg/day. Design analysis showed that the total capital cost of a conventional still can be significantly reduced from 2600 to 1500 $/unit with PV system integration at the specified productivity and optimal solar radiation of ~17 MJ/m² · day at peak time (02.00 PM). This work paves the way towards maximizing solar energy utilization from PV integration with solar desalination to achieve high freshwater productivity in single-basin solar still systems.     

Experimental study of forced circulation evaporator in zero discharge desalination process

Zero discharge desalination process is the most promising technology to prevent salinity and thermal shocks to ecosystem by effluent streams of desalination unit drained into the sea. Pretreatment, solar pond and forced circulation crystallizer are the major steps of one option to provide the purposes of zero discharge desalination process. Reduction of total hardness of wastewater occurs in pretreatment unit and the solar pond is proposed for effluent concentrated brine wastewater of pretreatment unit which seeks production of potable water and concentrated brine.The effluent stream from solar pond is conveyed to one forced circulation evaporator in order to produce salt and distilled water. This work presents the effective optimum parameters of one forced circulation evaporator such as occupied capacity of crystallizer main body, residence time, optimum temperature of heat exchanger, flow rate of cooling water, color and size distribution of salt crystals, amount of distilled water and energy consumption. Results show that the suitable range of crystal growth (700–830 μm) occurs when the occupied capacity of crystallizer is 70%. Also, the flow rate of cooling water in condenser is 10 kg/min and the efficient residence time is 4 h.     

Solar thermal desalination technologies

The use of solar energy in thermal desalination processes is one of the most promising applications of the renewable energies. Solar desalination can either be direct; use solar energy to produce distillate directly in the solar collector, or indirect; combining conventional desalination techniques, such as multistage flash desalination (MSF), vapor compression (VC), reverse osmosis (RO), membrane distillation (MD) and electrodialysis, with solar collectors for heat generation. Direct solar desalination compared with the indirect technologies requires large land areas and has a relatively low productivity. It is however competitive to the indirect desalination plants in small-scale production due to its relatively low cost and simplicity. This paper describes several desalination technologies in commercial and pilot stages of development. The primary focus is on those technologies suitable for use in remote areas, especially those which could be integrated into solar thermal energy systems.     

Solar distillation: the solar-assisted case

We consider here the case where a solar collector system, without storage, is linked to an otherwise stand-alone, fuel-driven desalination plant. The choices involved in selecting the type of solar collector and the design constrains on other components of the thermal source loop are outlined. A rationale is outlined for determining the most economic collector area for Such a situation and the proportion of the plant's energy requirement that can be provided by solar energy is discussed. Results for a specific collector/ desalination plant system, which include the effect of solar collector cost and fuel oil price on the economics, are presented. The decisions and constraints involved in selecting an optimum solar-assisted desalination system for a particular application are outlined.     

膜蒸馏技术研究及应用进展

膜蒸馏作为一种新型分离技术,具有操作温度低、设备简单、脱盐率高等特点,在海水淡化、苦咸水脱盐、果汁浓缩等过程具有良好的应用前景。本文简述了膜蒸馏的工作原理、特点和膜材料的制备方法,指出当前膜材料的研究方向。综述了直接接触式、气隙式、真空式和气扫式4种基本膜蒸馏形式和几种改进的膜蒸馏形式的传热传质原理、研究现状和发展方向。重点介绍了可再生能源以及工业低温余热驱动膜蒸馏的技术特点、研究现状和应用,包括太阳能光伏/光热驱动膜蒸馏技术、太阳能热泵耦合驱动膜蒸馏技术、太阳池膜蒸馏技术、地热能梯级利用驱动膜蒸馏技术和低温余热驱动膜蒸馏技术等,并指出其发展方向。最后,探讨了膜蒸馏技术亟待研究和解决的问题,为该技术的进一步发展提供参考。     

Solar ponds as heat source for low-temperature multi-effect distillation plants

Non-convecting solar ponds have the potential of providing low-temperature heat well below current fuel prices. The development of multi-effect distillation plants operating below 100°C allows solar ponds to be considered as the heat source. The paper discusses optimization of the size of the pond and the number of effects used, taking into account the large variation of pond heat output between summer and winter. One result is that, for current cost data, it pays to oversize the pond—leading to some rejection of heat in the summer (which is referred to as peak clipping)—because this leads to a better utilization of the desalination plant and a reduction in the summer-winter yield ratio. For Israel conditions, the peak clipping reduces the summer-winter output ratio from 4:1 to approximately 2:1 with the summer output maintained for 200–230 days in the year.Taking the pond cost at an upper figure of $7 × 10⁶ per km², and using costs for a locally produced desalination plant, the system competes with fuel at $42 a ton or reduces the cost of desalinated water by 18 cents per m³ when compared with a fuel system using fuel at $80 a ton.     

利用钾石盐太阳池制备氯化钾实验研究

以钾石盐为原料,以降低回收低品位钾资源能耗为目的,采用三层水平灌注的方法进行了钾石盐太阳池的构建实验,模拟15 ℃环境温度进行了太阳池运行实验,以及利用太阳池下对流层溶液制备氯化钾实验。结果表明：钾石盐太阳池能有效聚集太阳能,运行稳定时下对流层最高温度达到43 ℃,将钾石盐太阳池底部温度和密度较高的溶液取出,冷却结晶制得工业级氯化钾。     

Solar multistage flash evaporation (smsf) as a solar energy application on desalination processes

The application of solar energy on desalination constitutes one of the activities of the research and development program of digases. Within this philosophy a project is being developed in cooperation with the Federal Republic of Germany. The objective of the project is to test and prove the feasibility of the solar energy utilization as the source of the thermal energy required for a multistage flash evaporation plant.

The plant is composed of three systems:

1. Desalination system. Multistage flash evaporation plant with 10m³/d production capacity, 5.0 in performance ratio and 10 stages.

2. Solar energy captation. Composed of one low temperature subsystem of double pipe flat collectors with 670m² of effective captation surface, and a high temperature subsystem composed of parabolic concentrators with 320m² of captation surface.

3. Storage of energy. System designed with such capacity which allows continuous operation of desalination unit.

The poject is separated into two phases. The first includes the design manufacturing and tests for the three systems. The second phase comprises the installation and integration of the systems which compose the plant, the start-up operation and evaluation of plant performance.

At the present time, the first phase of the project is under development and it is expected to finish it at the end of June. The second phase will start in August with system start-up scheduled for the end of October.     

Concentrating solar power for seawater desalination in the Middle East and North Africa

The paper presents a long-term scenario for the demand of freshwater in the Middle East and North Africa (MENA) and shows how it may be covered by a better use of the existing renewable water sources and by sea water desalination powered with solar energy. Growth of population and economy, increasing urbanization and industrialization, and the rather limited natural resources of potable water in MENA are leading to serious deficits of freshwater in many parts of MENA. Modern infrastructure for water distribution, enhanced efficiency of use and better water management are to be established as soon as possible. However, even the change to best practice would leave considerable deficits, which are poorly covered by over-exploiting groundwater resources. Increased use of desalted seawater is therefore unavoidable in order to maintain a reasonable level of water supply. The desalination of seawater based on fossil fuels is neither sustainable nor economically feasible in a long-term perspective, as fuels are increasingly becoming expensive and scarce. Concentrating solar power (CSP) offers a sustainable alternative to fossil fuels for large scale seawater desalination. CSP can help to solve the problem, but market introduction must start immediately in order to achieve the necessary freshwater production rates in time.     

基于Cu/TiO2/C-Wood复合材料的聚光太阳能驱动自漂浮高效海水汽化催化分解制氢体系

利用储量丰富且易获得的太阳能和海水资源为人类提供可持续的清洁能源是一项具有深远影响的探索。在本工作中，设计合成了一种自漂浮复合材料（Cu/TiO₂/C-Wood），该材料具有高效的毛细输液、全光谱太阳能光热转化及光-热协同催化能力，可通过快速的界面相转移过程实现太阳能驱动海水汽化与水蒸气催化分解制氢的一步协同增效反应。其中，具有大量微通道和极轻质量的碳化木（C-Wood）作为漂浮载体，通过毛细作用将液态水快速输送至局部升温的C-Wood表面，借助高效光热转化过程使海水汽化脱盐，同时负载等离子金属Cu的TiO₂纳米粒子作为催化活性组分触发水蒸气光-热协同催化分解制氢反应，从而实现太阳能驱动高效海水汽化催化分解制氢。实验结果表明：该复合材料在15 kW·m^-2的光照条件下，产氢速率达到179 μmol·h^-1·cm^-2（35.8 mmol·h^-1·g^-1），且在循环利用5次后产氢速率仍基本保持不变。更重要的是，通过聚光太阳能和自漂浮毛细输液条件的共同作用，可以获得海水中主要成分氯化钠对产氢性能的显著促进，从而打破了海水制氢技术一直以来面临的氯离子副作用瓶颈问题，证实了聚光太阳能驱动自漂浮高效光热协同催化体系在规模化、绿色、可持续太阳能海水制氢中的应用潜力。     

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.