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A turbid solar pond is investigated to study how turbidity in the insulating zone affects the optimum dimensions of the pond, that suit a concerned design criterion. Four different criteria for the optimization have been undertaken, namely: minimizing the maturation time period, maximizing the extraction power under no constraint, maximizing the extraction power under constraint of fixed pond volume and maximizing the extraction power while simultaneously minimizing the volume. Transient numerical solution is sought for the first criterion, whereas for remaining three, a steady-state analytical model is employed that assesses the year-round extraction performance. Simplified versions of the respective models have been validated with data obtained experimentally and with theoretical data available in the literature. It is revealed that turbidity in the salinity gradient zone can lead to considerable alterations in the optimal pond dimensions, regardless of what the criterion used for optimization. The maximum errors in the optimal insulating zone and heat storage zone thickness values, arising from neglect of turbidity are observed to be about 125% and 60%, respectively. Hence, either attempts should be made to make solar ponds free of any foreign agents that cause turbidity, or if not, then they should be designed considering this factor into account, for which this work can serve as a guiding study. [Display omitted] • Turbidity effect on optimal zonal thicknesses of solar pond is studied. • Model has been experimentally and theoretically validated. • Simultaneous maximisation of power and minimization of pond volume is done. • Optimal insulating zone thickness always decreases with increase in turbidity. • Storage zone size is governed by exchanger area and absorption of radiant energy. [ABSTRACT FROM AUTHOR]

We consider three experimental small solar ponds (1 m × 1 m × 1 m) each pond contains one of the following salts, namely NaCl, Na 2 CO 3 and CaCl 2 respectively. The thermal behavior of these three ponds is being investigated numerically and experimentally over a period of 28 days. A bi-dimensional heat diffusion equation has been resolved numerically using the finite differences scheme of Crank–Nicholson. The experimental results show a good agreement with those obtained by simulation with an error of less than 1.5%. This study shows that CaCl 2 pond responds thermally more quickly than the two other ponds without reaching saturation. This extends further the applications scope with possible higher temperature despite relatively its higher cost which deserves further investigation. [ABSTRACT FROM AUTHOR]

This paper deals with the experimental investigation of a magnesium chloride saturated solar pond and its performance evaluation through energy and exergy efficiencies. The solar pond system is filled with magnesium chloride containing water to form layers with varying densities. A solar pond generally consists of three zones, and the densities of these zones increase from the top convective zone to the bottom storage zone. The incoming solar radiation is absorbed by salty water (with magnesium chloride) which eventually increases the temperature of the storage zone. The high-temperature salty water at the bottom of the solar pond remains much denser than the salty water in the upper layers. Thus, the convective heat losses are prevented by gradient layers. The experimental temperature changes of the solar pond are measured by using thermocouples from August to November. The densities of the layers are also measured and analysed by taking samples from at the same point of the temperature sensors. The energy and exergy content distributions are determined for the heat storage zone and the non-convective zone. The maximum exergy destructions and losses appear to be 79.05 MJ for the heat storage zone and 175.01 MJ for the non-convective zone in August. The energy and exergy efficiencies of the solar pond are defined as a function of solar radiation and temperatures. As a result, the maximum energy and exergy efficiencies are found to be 27.41% and 26.04% for the heat storage zone, 19.71% and 17.45% for the non-convective zone in August, respectively. [ABSTRACT FROM AUTHOR]

Given their unique resources, the carbonate salt lakes in Tibet offer significant advantages in the extraction of lithium, but some disadvantages are being exposed in production. These disadvantages include the long period of lithium extraction and the low grade of lithium carbonate caused by geographical conditions and climate factors of the Qinghai–Tibet plateau. Based on the above reasons, we rebuilt the traditional solar ponds by introducing a kind of heat exchanger in a bid to speed up the temperature rise of brine, whereby we planned to make use of the high-temperature geothermal resources around the lakes to produce lithium carbonate in large-scale applications. We carried out a small lithium-extraction experiment with hot water as the heat source for the purpose of verifying the feasibility of lithium extraction by geothermal-salinity gradient solar pond (G-SGSP). In the experiment, the contrastive analysis method was employed as a means to study the relationship between ion diffusion and temperature, as well as salinity in G-SGSP and these controllable factors’ impact on the precipitation of lithium carbonate. The results of the experiment show that it is highly feasible to extract lithium through G-SGSP, thus enhancing the efficiency of lithium extraction and generating higher-grade lithium carbonate. Thus, the experiment serves as a dramatic reference for extracting lithium from Dangxiong Tso Salt Lake through the application of geothermal resources. [ABSTRACT FROM AUTHOR]

Solar energy is a substantial source of clean and renewable energy. Recently, solar pond technology has made a great progress due to the fact that solar ponds can collect and store heat in the same time which has reduced the cost significantly thus making it an area of interest for the industry and researchers. Several salt gradient solar ponds have been constructed in many regions around the world. This paper reviews the various schemes of solar ponds, in addition to their performance, optimization, heat extraction mode and applications as reported in the literature. The maintenance and cost effect on solar pond have also been discussed. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effect of the sunny area ratios on thermal efficiency of model solar pond for different cases in Adiyaman, Turkey. For this purpose, we modeled the solar ponds to compute theoretical sunny area ratios of the zones and temperature distributions in order to find the performance of the model solar ponds. Incorporating the finite difference approach, one and two dimensional heat balances were written for inner zones and insulation side walls. Through, careful determination of the dimensions, insulation parameter and incoming solar radiation reaching the storage zone increased the efficiency of the solar pond. The efficiencies of the model solar pond were determined for case1a–2a–3a–4a to be maximum 14.93%, 20.42%, 23.51% and 27.84%, and for case1b–2b–3b–4b to be maximum 12.65%, 16.76%, 21.37% and 23.30% in August, respectively. With the increase of the sunny area ratio, the performance of the solar pond significantly increased. However, with the increasing rate of the surface area, performance increase rate decreased gradually. The results provide a strong perspective to determine the dimensions of the solar pond before starting the project of a solar pond. [ABSTRACT FROM AUTHOR]

In this paper we present the energetic and exergetic performance of a solar pond integrated with four flat plate solar collectors. The integrated solar pond system was built and tested at Cukurova University in Adana, Turkey. The solar pond consists of salty water zones to prevent convection heat losses from the heat storage zone (HSZ) of the solar pond. The temperature distributions of the solar pond and the inlet–outlet of the heat exchanger were measured by using thermocouples and a data acquisition device. An energy and exergy models were developed to study the energetic and exergetic performance of the integrated solar pond. The energy and exergy performances were compared for the each zone of the solar pond. The reference environment temperature in the exergy analysis was specified as the average representative temperature of each month of the year. The energetic and exergetic performances of the integrated solar pond for the heat storage zone were found to be maximum 32.55% and 28.69% in August, and to be minimum 9.48% and 5.51% in January, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we present an experimental and theoretical investigation of the energy storage performance of a model solar pond with a surface area of 2.096 m and a depth of 2.0 m which is built in Cukurova University in Adana, Turkey. The system consist of three different densities zones (e.g., upper convective, non-convective and heat storage). During the months of a year, a data acquisition device was used to determine the temperature at various locations vertically within the pond. In the theoretical part, a mathematical model is used based on finite differences. For this system, the heat losses have been analyzed and modelled by using the Heat 2 software. We developed a performance model to determine the efficiencies of the solar pond. As a result, the total heat losses in side walls and inner insulation zones of the system are found. The experimental and the theoretical heat storage performance of the heat storage zone of the solar pond is determined the highest energy efficiency as 28.41 and 30.16 % for August, the lowest energy efficiency as 8.27 and 10.74 % for January, respectively. The results are compared and hence a good agreement is found. [ABSTRACT FROM AUTHOR]

Phase-change materials (PCMs) play an important role in thermal energy management in response to the demand for energy conservation with increasing concerns about environmental pollution. The selection of an optimal PCM is a difficult and critical task because of the immense number of different materials available that have different characteristics. To weigh the influencing factors for a PCM and provide a feasible method to select the best PCM, the VIKOR method was introduced in the field of PCM selection. On the basis of the characteristics of PCMs, an evaluation system of three levels and six different attributes was constructed and a pairwise comparison matrix was established after analysis of the attribute relationships. The relative weights determined by the matrix and the VIKOR method were used to sort out the attributes of alternative PCMs comprehensively. The results show that the method is effective and practical to select PCMs, and stearic acid was determined to be the optimal PCM among the candidates for low-temperature thermal energy storage. [ABSTRACT FROM AUTHOR]

In many emerging countries over the past few years some phenomena, such as a better welfare state, industrial growth and a development in agriculture, led to a significant increasing of the demand concerning fresh water. In order to face this ever-growing demand, one of the possible solutions to counterbalance the lack of water resources, is the desalination of sea water. For this specific goal solar energy, as a resource, is the process which has more reliance since it allows a low-cost production of desalted water (without using any valuable energy resources such as fossil fuels) and in a complete respect of the environment. This first study has the purpose to analyze from an energetic perspective whether it is possible or not to reach process temperatures over 100 °C, through the use of solar ponds and heat transformers, in order to produce desalinated water. The final aim of this work is to quantify the surface of solar ponds needed to a production (expressed in cubic meters) of desalinated water. An absorption heat transformer is a thermal machine that while extracting heat from a source (at an available temperature) is able to ennoble a portion of the heat collected/obtained, making it available at higher temperatures. This process occurs at the expenses of the remaining portion of heat whose temperature degrades by lowering its values. The portion of heat will be then transferred to a thermal well. Hence an absorption heat transformer can use the solar energy stored in solar ponds as an energy source at an average temperature. Process temperatures which are higher than 100 °C for a whole year can take place only under certain chained conditions such as: source temperature with steady values during the entire season obtainable through solar ponds; condensation process occurring at sufficiently low temperatures through the use of sea water; exertion of heat transformers. The heat which is usually available at these temperatures could be used for common thermal processes during the desalination of seawater. In this work we want to demonstrate that it is possible, energetically speaking, to produce desalinated water by exploiting the solar energy stored in solar ponds and the technology of absorption heat transformers. We can notice how for every m 3 of desalinated water produced in one day we need ponds with an area ranging between 1000 and 4000 m 2 , this depends on the amount of heat flux drawn. The analysis we carried out represents a first attempt to face this kind of problem. In future studies we will examine both technical and economic feasibility. [ABSTRACT FROM AUTHOR]

A higher Low Convective Zone (LCZ) temperature is important for the Salt Gradient Solar Pond (SGSP) thermal engineering application, which is bound to bring a more extensive application. For this purpose, we studied on adding a layer of coal cinder at bottom of LCZ of solar pond, here coal cinder is the burning residues of coal. Temperature development of adding coal cinder at bottom of SGSP has been experimentally and theoretically studied. One dimensional transient numerical model was used to estimate the temperature development in SGSP. The outdoor experiments were used to qualitatively study the temperature evolution of different bottom treatments and porous materials influence, and also used to validate the mathematics model present in this paper. The results show that adding coal cinder at bottom of SGSP leads to a higher LCZ temperature than the traditional bottom treatment. Good consistency has been achieved in the simulation results and the experimental results. Finally, in order to estimate the effect of coal cinder used in large-scale solar pond, a numerical simulation was given and compared to the similar research. The results of this paper show that it can obviously increase LCZ temperature by adding coal cinder at bottom of LCZ, and as a cheap material with perfect thermal performance, it is suitable to be applied in practical SGSP. [ABSTRACT FROM AUTHOR]

The present paper undertakes a study on the exergetic performance assessment of a solar pond and experimental investigation of turbidity effect on the system performance. There are various types of solar energy applications including solar ponds. One of significant parameters to consider in the assessment of solar pond performance is turbidity which is caused by dirty over time (e.g., insects, leaf, dust and wind bringing parts fall down). Thus, the turbidity in the salty water decreases solar energy transmission through the zones. In this study, the samples are taken from the three zones of the solar pond and analyzed using a spectrometer for three months. The transmission aspects of the solar pond are investigated under calm and turbidity currents to help distinguish the efficiencies. Furthermore, the maximum exergy efficiencies are found to be 28.40% for the calm case and 22.27% with turbidity effects for the month of August, respectively. As a result, it is confirmed that the solar pond performance is greatly affected by the turbidity effect. [ABSTRACT FROM AUTHOR]

An experimental scale desalination pond which utilizes solar energy as a heat source is studied in this paper. The marked solar desalination pond is considered as one of the main stages in a proposed zero discharge desalination process. The effluent waste water of the desalination unit of the petrochemical complex is treated in the proposed zero discharge desalination process to produce potable water and salt. Evaporation distillation method is used in the studied solar desalination pond. Basically, this solar desalination pond is working as batch stage. At the first, the solar-powered desalination pond is introduced then the used method for distillation is discussed and the experimental results are represented in this paper, finally. The results show the feasibility of using the proposed solar-powered pond. The rate of gained distilled water by the proposed solar powered pond is compared with conventional solar pond, finally. [ABSTRACT FROM AUTHOR]

Active solar distillation system integrated with solar pond is the green energy system for desalination without negative environmental impact. This clean technology has potential to contribute a lot to water security, sustainable development, and world stability. In this article, results of the energy as well as exergy analysis performed on this novel system integrated with solar pond are presented. This theoretical analysis is carried out in the climatic conditions of New Delhi (India) during a typical summer day. The model and procedures can be helpful in the design, and performance investigation of the actual system anywhere in the world. The daily productivity, energy, and exergy efficiency of the passive solar still are found to be 5 L/m, 38.63 %, and 2.71 %, respectively, corresponding to a sum total of 24.436 MJ/m day solar energy input in passive mode. With the integration of solar pond in the active solar still, the daily productivity, energy, and exergy efficiency rises to about 9.5 L/m, 46 %, and 14.81 % respectively, for thermal energy input from 100 to 500 W/m during off-sunshine hours. The further improvement in the performance of the same system is observed if the thermal energy is supplied continuously (24 h) to the solar still in addition to incident solar radiation. The proposed system will meet the demand of freshwater in both rural and urban areas and help in reducing the load of CO emission on the environment, saving high grade energy consumed for desalination through conventional devices and technologies. [ABSTRACT FROM AUTHOR]

Abstract: A novel two-layer nanofluid solar pond is introduced. A mathematical model that describes the thermal performance of the pond has been developed and solved. The upper layer of the pond is made of mineral oil and the lower layer is made of nanofluid. Nanofluid is known to be an excellent solar radiation absorber, and this has been tested and verified using the mathematical model. Using nanofluid will increase the extinction coefficient of the lower layer and consequently will improve the thermal efficiency and the storage capacity of the pond. The effects of other parameters have been also investigated. [Copyright &y& Elsevier]

Abstract: Solar energy technologies and their applications are as relevant today as they were in 1950s. A comprehensive review of the most recent studies having numerous references to the past research works on the thermodynamic and economic feasibility of solar ponds is presented in this communication. Thermodynamic models for the performance analysis of solar ponds and its validation with the experimental results by a number of researchers are highlighted. Expressions for estimation of energy and exergy efficiencies of all three zones of salt-gradient solar pond are presented. Need of the evaluation and revival of solar pond technology for continuous supply of large quantity of solar thermal energy for low temperature applications has been advocated. Some of these applications are domestic and industrial process heating, heating of building and greenhouse, refrigeration and air-conditioning, desalination and salt production, agriculture and aquaculture, and power generation. Usefulness of the alternative technology of salt-gradient solar ponds such as solar gel ponds, equilibrium solar ponds, and shallow solar ponds has also been incorporated. It has been explored that solar ponds have a great potential of saving a large quantity of energy from degradation as well as exergy destruction due to the use of ‘energy based on fossil fuels and electricity’ for the purpose of usual low temperature applications. In this way, solar ponds will prove to be helpful in minimizing the present alarming ecological problems and energy shortage by substituting a large fraction of high grade energy consumption. [Copyright &y& Elsevier]

The effect of the transparent covers (glass, polycarbonate, and mica) on the small cylindrical solar pond performance is studied. The temperature and density distributions are measured to evaluate the performance of the covered cylindrical solar pond. The pond covers provide a significant potential for energy savings and storage by insulating upper convective zone. Thus, such transparent covers are used for reducing the thermal energy losses from the top surface of the cylindrical solar pond. The transmission, reflection, and absorption coefficients of the covers are calculated to determine the monthly solar energy contents of the solar pond. The energy efficiencies of the solar pond are found for each type of covers from November 2008 to March 2009. As a result, the highest efficiency is determined to be 17.86% for glass cover in March, while the efficiencies of polycarbonate and mica become 16.95% and 15.86%, respectively. In this regard, the glass cover appears to be the best option for the solar ponds. [ABSTRACT FROM AUTHOR]

Highlights: [•] Experiments and numerical models were analyzed to understand solar pond efficiency. [•] Boundary effects typically reduce the efficiency of small-scale solar ponds. [•] Artificial lighting affects the energy that reaches the lower convective zone. [•] Turbidity is more important in large-scale solar ponds and decreases its efficiency. [•] Large-scale solar ponds collect more energy than small-scale solar ponds. [ABSTRACT FROM AUTHOR]

Highlights: [•] Numerical study is conducted. [•] Transient evolution of velocity, temperature and concentration fields is analyzed. [•] Effect of aspect ratio on the temperature and velocity fields is studied. [•] Average temperature and concentration profiles are obtained in transient regime. [Copyright &y& Elsevier]

Water is one of the earth's most abundant resources, covering about three-quarters of the planet's surface. Yet, there is an acute shortage of potable water in many countries, especially in Africa and the Middle East region. The reason for this apparent contradiction is, of course, that ∼97.5% of the earth's water is salt water in the oceans and only 2.5% is fresh water in ground water, lakes and rivers and this supplies most human and animal needs. Tackling the water scarcity problem must involve better and more economic ways of desalinating seawater. This article presents a comprehensive review of water desalination systems, whether operated by conventional energy or renewable energy, to convert saline water into fresh water. These systems comprise the thermal phase change and membrane processes, in addition to some alternative processes. Thermal processes include the multistage flash, multiple effects boiling and vapour compression, cogeneration and solar distillation, while the membrane processes include reverse osmosis, electrodialysis and membrane distillation. It also covers the integration into desalination systems of potential renewable energy resources, including solar energy, wind and geothermal energy. Such systems are increasingly attractive in the Middle East and Africa, areas suffering from shortages of fresh water but where solar energy is plentiful and where operational and maintenance costs are low. The advantages and disadvantages, including the economic and environmental aspects, of these desalination systems are presented. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Evaporation, temperature, and heat content for a covered solar pond were monitored. [•] Floating discs decrease evaporation and increase temperature and heat content. [•] Reduced evaporation enables operation where water supply is limited. [•] Increased heat content significantly improves solar pond thermal efficiencies. [•] A buoyant, transparent disc is recommended for large scale solar ponds. [ABSTRACT FROM AUTHOR]

Highlights: [•] A model to describe and simulate the performance of solar pond was developed. [•] It was validated with experimental data collected during 20months in 50m2 solar pond. [•] Temperature profiles were properly described, mainly at lower subzones of NCZ and LCZ. [•] Model was used to predict the thermal performance of 500m2 pre-industrial solar pond. [•] A maximum temperature of 75°C and 12–25% energy efficiency at LCZ were predicted. [ABSTRACT FROM AUTHOR]

Highlights: [•] Proposed transient thermal performance model for heat extraction from NCZ and LCZ. [•] Estimated instantaneous efficiency and average annual efficiency of the solar pond. [•] Predicted optimum mass flux for limiting heat extraction condition. [•] Transient analysis showed 47% improvement in the efficiency of solar pond. [Copyright &y& Elsevier]

Highlights: [•] Energetic and exergetic performance of two circular and square solar ponds are studied. [•] Solar ponds may be used as effective thermal storage in Yazd with a desired efficiency. [•] Circular solar pond shows superior thermal performance than the square one. [•] Energy efficiencies are higher than exergy efficiencies for both solar ponds. [Copyright &y& Elsevier]

Highlights: [•] The linear instability of a solar pond with porous material in the LCZ is explored. [•] In general, the presence of porous material causes the solar pond to be more stable. [•] The percentage of porous material does not stabilise the system in a linear fashion. [•] Solar pond instability is affected by the proportion of heat flux extracted. [ABSTRACT FROM AUTHOR]

ABSTRACT: The risk of geosynthetic clay liner (GCL) desiccation in low stress applications such as solar ponds was investigated using a fully coupled thermo-hydro-mechanical model. Parameters were developed and verified by comparison with previously reported laboratory data. A parametric study was performed to establish recommendations for future investigation. The water retention curve of the GCL was found to have a significant effect on the conditions that are expected to cause desiccation. The temperature coefficient of the water retention curve was also found to have a significant effect, yet this parameter is not well defined. Poisson's ratio was found to affect the risk of desiccation in proportion to the applied stress. As reported by previous researchers, the initial degree of saturation of a GCL was found to influence desiccation; however, the effect was diminished at low applied stress. The magnitude of the increase in liner temperature, above groundwater temperature, was found to have the potential to cause desiccation of a GCL in a composite liner. [ABSTRACT FROM AUTHOR]

• The ICP process shows separation of ions based on electrophoretic mobility. • Reduction of Mg2+:Li+ is demonstrated with standard divalent ion exchange membrane. • The technical feasibility is compared with well-established electrodialysis platforms. The surge of electric vehicle deployment in response to the global climate crisis has marked tremendous increase in the demand of lithium-ion batteries. Lithium brine has gained much attention as a critical primary lithium resource over mineral sources due to cheaper processing and greater abundance. However, reducing the Mg2+:Li+ ratio of brines remains a challenge, as magnesium contaminates lithium precipitates. Solar evaporation ponds are traditionally employed to concentrate Li and reduce Mg content to tackle this issue, but typically require 1–2 years to process a batch of feed solution, and require much land area disturbing the local environment near brine resources. Here we present a continuous, scalable ion separation technique for reducing the Mg2+:Li+ ratio of brine as an alternative to solar evaporation. The device utilizes ion concentration polarization to induce a locally amplified electric field. The amplified electric field separates ions into streams according to electrophoretic mobility. We demonstrate reduction of a 25:1 Mg2+:Li+ lab brine to below 10:1 Mg2+:Li+, which is an acceptable lithium production purity by industrial standards. Reduction of a 60:1 Mg2+:Li+ to ∼ 10:1 and a 100:1 Mg2+:Li+ brine to approximately 20:1 are also demonstrated. The system suffers a high specific energy consumption (8.804 kWh/g Li+ for 25:1 reduction to 9:1) due to low lithium recovery (9.9%) and microfluidic system size. However, an economic scaling analysis shows that this work is within an order of magnitude of the state-of-the-art separation technologies in the literature after various process parameters are normalized. Ultimately, this work demonstrates a potential novel process for continuous lithium extraction from brines, which is a generalizable ion separation tool utilizing differences in electrophoretic mobility. [ABSTRACT FROM AUTHOR]

The present research deals with a novel hybrid system that comprises of a salinity gradient solar pond (SGSP) integrated with a proton exchange membrane fuel cell (PEMFC) and a thermoelectric generator (TEG). The key novelty of this research is the use of PEMFC waste heat to increase the performance of the low-temperature heat source (solar pond). Also, a thermoelectric generator is employed in the proposed setup for complete waste energy recovery. In this paper, the proposed system's energy, exergy, and economic (3E) performance are investigated, as well as compared with two additional systems that were modelled by excluding TEG and PEMFC to showcase the benefits of the sub-systems in the final configuration. A parametric study is also conducted to investigate the effect of significant parameters on the overall system performance. The simulation results indicated that the integrated system's net output power is 2288.8 kW at a base case operating condition, with energy and exergy efficiency of 11.26% and 13.17%, respectively, and a system cost rate of 394 $/h. In comparison to other components in the integrated system, SGSP alone accounts for 75% of total exergy degradation and has the highest investment cost rate of 66.70 $/h. Further, to achieve the best system performance, a multi-criteria optimization is performed for the suggested system with net output power, energy efficiency, exergy efficiency, and system cost rate as objective functions. Besides, the multi-criteria decision analysis (MCDA) is also carried out on the obtained Pareto front using TOPSIS decision-maker to select the best operating condition that improves the output power, energy, and exergy efficiency by 52.6%, 49.6%, and 61.8%, respectively, at the expense of 5.2% increase in the system cost rate. The current investigation demonstrates how an appropriate optimized design of an integrated energy system using SGSP, PEMFC, and TEG can improve the overall performance with reasonable cost increment. [Display omitted] • Solar pond integrated system with fuel cell and thermoelectric generator is proposed. • 3E based multi-criteria optimization and decision analyses are presented. • Solar pond alone accounts for 75% of total exergy degradation in the integrated system. • Optimization improved the exergy efficiency of the integrated system by 61.8%. [ABSTRACT FROM AUTHOR]

The thermal performance of a solar pond is affected by the amount of heat lost to the ground through the lower convective zone (LCZ) in which the heat is stored. Studies are focused on decreasing the heat losses, to maximize the energy stored and guarantee the stability of the thermohaline system over time. Phase change materials (PCMs) can help to achieve all these goals, since they work as thermal energy storage (TES), exploiting the latent heat absorbed during the solid-liquid phase change. This paper presents an experimental application of PCMs in the LCZ of a small solar pond. The paraffin wax was enclosed in aluminium cylinders which have been arranged on the bottom. The temperature of the solution in deep is monitored both with and without the PCM. The stability of the pond is analyzed through a laser shadowgraph technique, to visualize the effect of the thermal convection on the interfaces. Results show that the LCZ of the solar pond with PCM is around 3 °C colder than the reference case after a 6-h heating period. The shadowgraph analysis proves that the thermal convection in the reference case is stronger and damage the interface until break. The monitoring of the solar pond with PCM shows an improved stability. • A solar pond integrated with PCM has been designed and built. • After the heating period, the system with PCM results colder in the LCZ. • PCM stabilized the LCZ-NCZ interfaces, as proved with the shadowgraph technique. [ABSTRACT FROM AUTHOR]

In the field of desalination powered by renewable energies, the use of solar power cycles exhibits some favorable characteristics, such as the possibility of implementing thermal energy storage systems or a multi-generation scheme (e.g., electricity, water, cooling, hydrogen). This article presents a review of the latest design proposals in which two power cycles of great potential are considered: the organic Rankine cycle and the supercritical CO2 power cycle, the latter of growing interest in recent years. The designs found in the literature are grouped into three main types of systems. In the case of solar ORC-based systems, the option of reverse osmosis as a desalination technology is considered in medium-temperature solar systems with storage but also with low-temperature using solar ponds. In the first case, it is also common to incorporate single-effect absorption systems for cooling production. The use of thermal desalination processes is also found in many proposals based on solar ORC. In this case, the usual configuration implies the cycle's cooling by the own desalination process. This option is also common in systems based on the supercritical CO2 power cycle where MED technology is usually selected. Designs proposals are reviewed and assessed to point out design recommendations. [ABSTRACT FROM AUTHOR]

The knowledge of steady-state temperature distribution is known a priori for natural convection stability analysis. The present study determines the temperature profiles in an infinite horizontal layer of fluid filled with saturated porous medium confined between two convective surfaces subjected to external radiative incidence and imposed downward convection. The investigation concentrates on the influences of the thermal boundary condition (Biot number), internal and external Rayleigh numbers, Peclet number, optical thickness, and surface reflectivities. The implications of these factors on fluid stability are addressed in detail. [DOI: 10.1115/1.1564078] Keywords: Porous Medium, Solar Pond, Fluid Instability, Temperature Distribution

Highlights: [•] Analytical models were developed for the SSP under open and closed cycle modes. [•] The models predicted the pond performance with excellent accuracy. [•] The daily efficiency of the pond equals 59% and 33% under the closed and open cycle modes. [•] The present solar pond could be used as a heat source all year-round. [Copyright &y& Elsevier]

The article presents a study on the enhanced solar pond and its thermal characteristics. Noted is the construction of two min-solar ponds with surface dimensions of 2.4 meters (m) x 2.4 m and a depth of 1.2 m. Results indicated that the addition of porous medium can save heat and reduce turbidity of solar ponds while covering of plastic films can reduce turbidity and surface heat loss.

Abstract: The linear instability of the gradient zone of a solar pond containing a fluid-porous interface is investigated. It is found that the gradient zone can retain the same stability for lower values of the solute Rayleigh number with the introduction of a porous material compared with a purely fluid layer, whilst maintaining the same lower convective zone temperature. Interestingly, it is also shown that for certain parameter values the penetration of a porous medium into the gradient zone can cause the temperature of the lower convective zone to rise. However, for certain parameter ranges, when the fluid-porous interface is towards the top of the gradient zone, the solar pond can become highly unstable. [Copyright &y& Elsevier]

Abstract: Solar ponds are large-scale energy collectors with integral heat storage for supplying thermal energy. In the present work, both experimental and numerical parts of solar pond performance under Jordanian climate conditions have been investigated. In the experimental part, an insulated solar pond with a surface area of 3.5m2 and a depth of 1.0m was built at the University of Jordan to investigate the performance of solar pond under Jordanian climate conditions. The three salty water zones (upper convective, non-convective and heat storage) were formed by filling the pond with salty water of various densities. 16 thermocouples (type T) were used to measure the temperature profile within the pond. In the theoretical part, a MatLAB code was developed to predict the temperature distribution along the solar pond. A maximum temperature of 47°C was recorded in the heat storage zone in spring time (April 2010). The results obtained from the numerical simulation are compared with the experimental results and it has been found that they are in a good agreement. [Copyright &y& Elsevier]

Abstract: In this study, we present an experimental investigation of energy distribution, energy efficiency and ratios of the energy efficiency with respect to shading effect on each zones of a small rectangular solar pond. The system is filled with salty water in order to form upper convective, non-convective and lower convective zones. A data acquisition device is used to measure and record the hourly temperatures at various locations in different solar pond zones (distributed vertically within and at the bottom of the pond, and horizontally and vertically within the insulated side-walls). A shading model is developed to gain a more profound understanding of the energy performance of the pond. The model results of the each zone are compared with and without shading effect, based on the corresponding energy efficiencies. The shading surface area of the zones does not contribute to the thermal performance of the pond but it takes place non-sunny area in the zones by shading. Thus, the efficiency of the solar pond decreases with increasing the shading area. The energy efficiencies of the inner zones with and without the shading effect for each zone in the energy analysis are specified as the average representative solar energy for each month of the year. The highest energy efficiencies for the cases of with and without shading area are found for the month of August to be: 4.22% and 4.30% for the upper convective zone, 13.79% and 16.58% for the non-convective zone, and 28.11% and 37.25% for the lower convective zone, respectively. The results confirm that the solar pond storage efficiency can be increased by eliminating the effect of shading area. Moreover, the ratios of shading effect are found to be: 0.651 at the lower convective zone, 0.279 at the non-convective zone and 0.068 at the upper convective zone. [Copyright &y& Elsevier]

Abstract: This paper examines the concept of using the trilateral flash cycle for combined desalination and power generation from salinity gradient solar ponds in the salt affected areas of Australia. Firstly causes of the high salinity in the ground waters of northern Victoria, Australia are discussed. Existing salinity mitigation schemes are introduced and the integration of solar ponds with those schemes is discussed. Further the basic working principle of the combined desalination and power generation system is discussed followed by discussion of the governing equation and thermodynamics used in the desalination and power generation process. Experimental setup and the test results are briefly explained to give an idea of the performance of the present system. Later it is shown how a combined desalination and power generation system can be coupled with a solar pond for fresh water production and power generation. Following the introduction of this concept the preliminary design is presented for a demonstration of a combined desalination and power plant coupled with a solar pond of 10000m2 surface area and a depth of 3m located in the northern region of Victoria. The performance, including fresh water output, power output and efficiency of the proposed plant operating in northern Victoria is analysed and the results are discussed. [Copyright &y& Elsevier]

In order to design and analyse natural or artificial system, where instable stratified layer occurs (such as solar pound and storage tanks), understanding of double diffusive behaviour is necessary. When an initially isothermal, salt stratified-system is heated uniformly from below, a convecting, growing layer is first formed whose sizes depend on the stabilizing salinity distribution. A quantitative description of such problem showed that a convective motion first produces layer at the bottom. This layer, separated by an oscillatory interface, continues to deepen with time until achieving a critical depth. The mechanisms responsible for the growth of the first mixed layer are poorly understood until now. A laboratory study is made to well understand the mechanism of transfer in an instable stratified system. A transparent cavity with free surface is filled with stratified-salt water and it is heated from below at constant temperature. The convective motion is visualized by (a) shadowgraph to obtain more information on density exchange through the interface and (b) particle image velocimetry to measure the time evolution of speed fields. [ABSTRACT FROM AUTHOR]

Solar Ponds collects the solar energy and the collected solar energy will be carried by a flowing fluid. Low Temperature Energy Storage System (LTES) stores the thermal energy from solar pond and increases the period of operation of the solar pond. In this paper, the solar energy collected by the simulated solar pond was stored in a LTES and the medium adopted was paraffin phase change material (PCM). PCM is preferred because of its higher storage density, with less volume. However the disadvantage of PCM for using as LTES is its poor thermal conductivity and requires more time period and more surface area for charging and discharging of thermal energy. To overcome this problem, an attempt was made by dispersing CuO nano particles within the PCM. The thermal conductivity of LTES is determined both analytically and experimentally. From the experimental investigation carried out, it was observed that, the thermal conductivity of PCM and the charging and discharging time of LTES has also been reduced significantly by introducing CuO nano-particles [ABSTRACT FROM AUTHOR]