Salinity Gradient Solar Pond Research Articles

Temperature and salt concentration behavior of a compact rectangular salinity gradient solar pond

Design of economical and effective solar ponds which are useful thermal energy storage devices, remains a huge challenge. The present work aims at investigating the thermal performance of low cost mini salt gradient solar pond. The portable pond was fabricated as a rectangular configuration having a volume of 0.5m3. Polystyrene and high density polyethylene sheets were employed for insulating the walls. The top of the pond was covered with a slender glass so that the dust accumulation could be prevented without affecting the absorption of solar radiation. Sodium chloride salt was used as the medium and the three salt gradient regions namely lower convective, non-convective, and upper convective regions were established through injection filling technique. The temperature and salt gradient data were observed experimentally for a period of 20 days at Coimbatore, India. The pond could absorb significant amount of available radiation (around 65%) and the maximum temperature of the pond was observed to be 49oC. Frequent washing of the water surface is necessary to maintain stable salt gradient. Nevertheless, portable pond fabricated with low cost materials exhibited good potential of storing solar energy for solar thermal applications.

Augmentation of heat storage capacity of compact salinity gradient solar pond using dragon fruit extract coated magnesium powder and paraffin wax

Compact salinity gradient solar ponds are gaining recognition as a source of heat storage medium in densely populated areas and small residences around the globe. However, their efficiency is limited because of the small capacity of saline water and lower potential. In this study, a compact salinity gradient solar pond was developed to enhance heat storage efficiency. This experimental study investigates the effect of incorporating a novel phase change medium composed of paraffin wax infused with dragon fruit extract-coated magnesium oxide powder to enhance the heat storage capability of the compact salinity gradient solar pond. The dragon fruit extract is utilised as a natural additive to enhance the thermal properties of the magnesium oxide powder. This improves the heat storage capability of the phase change medium and provides eco-friendliness to the system. The experiment allowed heat addition and rejection from the saline water through natural convection mode. After coating the MgO nanopowders, the peak temperature in the lower convective zone of the compact salinity gradient solar pond was 51.2 ℃ on the seventh day. The efficiency of the solar pond increased when the previous day exhibited a drop in solar intensity. It showed a maximum efficiency of 35 %. An optimisation study revealed that the solar pond efficiency can be 28.16%. It is concluded that the heat stored in the compact salinity gradient solar pond increases because of the periodic heating of the saline water and the presence of the heat storage medium.

Study of the optimization of the stereo-crystallization process with enhanced salinity-gradient solar pond for lithium extraction from Zabuye salt lake in Tibet

Study of the optimization of the stereo-crystallization process with enhanced salinity-gradient solar pond for lithium extraction from Zabuye salt lake in Tibet

Enhanced performance and stability of a solar pond using an external heat exchanger filled with nano-phase change material

Salinity gradient solar ponds are a promising technology for harnessing/storing solar thermal energy. The energy storage capacity of solar ponds can be enhanced by incorporating phase change materials (PCMs). However, the low thermal conductivity of PCMs can negatively affect energy charging/discharging rates. In this study, an external energy storage system filled with CuO nanoparticle-enhanced PCM was employed to improve the performance and stability of a solar pond. The results were compared with water and pure PCM (paraffin) as control materials. Energy and exergy analysis was used to assess the effects of nanoparticles and their concentration on the overall solar pond performance. According to the results, the upper convective zone temperature remained consistent across all experiments and varied within the same range throughout the day. A slight temperature variation at specific times indicated the stability of the developed solar pond system. The system's exergy (energy) efficiency was increased from 10.72% (51.83%) for water to 14.71% (70.1%), 22.77% (82.13%), and 25.93% (87.58%) for PCM, PCM with 1 wt% nanoparticles, and PCM with 2 wt% nanoparticles, respectively. Incorporating nanoparticle-enhanced PCMs in external heat exchangers can effectively improve the stability and performance of solar pond systems.

An experimental investigation on winter heat storage in compact salinity gradient solar ponds with silicon dioxide particulates infused paraffin wax

Silicon dioxide particulate which is also called silica, owing to its cost-effective synthesis, abundant availability, and high heat transfer capabilities, present an eco-friendly solution with immense potential for diverse applications, including solar heating systems. This novel study explores the integration of silica microparticles infused in paraffin wax in a compact salinity gradient solar pond for enhanced heat storage during the winter season. Leveraging their biocompatibility, facile functionalization, and expansive surface area, silica microparticles exhibit outstanding attributes such as photoconductivity, optimal thermal expansion, corrosion resistance, and enduring durability, all of which synergistically contribute to system efficiency. During the first day, without any heat storage medium, the three distinctive zones of the compact salinity gradient solar pond exhibited temperatures of 31.2 °C in the upper convective zone, 32.8 °C neutral convective zone, and 35.7 °C in the lower convective zone respectively. Experimental investigations are conducted, employing both paraffin wax and silicon dioxide microparticles as augmenting agents to amplify heat storage capacity within the compact solar pond setup. While using paraffin wax without silica particulates the lower convective zone temperature was 4.2 % lower because of heat storage. The incorporation of trace amounts of silicon dioxide microparticles within paraffin wax establishes a novel hybrid approach. The outcomes highlight the profound impact of this hybridization on thermal characteristics, resulting in a discernible improvement in the compact salinity gradient solar pond's heat behavior. Notably, the phase change material introduces a temperature enhancement of approximately 1.5 %, and the amalgamation further elevates the temperature retained to 56 °C within the lower convective zone. An optimization analysis underscores the pivotal role of the solar pond configuration in dictating temperature changes, surpassing the influence of time considerations. This research underscores the transformative role of silicon microparticles in optimizing thermal performance within compact salinity gradient solar ponds, unlocking avenues for enhanced winter energy utilization.

Experimental study on a novel waterless solar collector

This study is an endeavour to introduce a novel approach to enhance the performance of solar collectors. The sun emits sufficient power of solar radiation to meet the demand of en-ergy. Harvesting the renewable solar energy needs advanced technologies and requirements. Solar ponds including salinity gradient solar ponds (SGSPs) are common solar collectors. These ponds are one of the solar energy applications used for many industrial and domestic purposes. However, challenges of the conventional SGSPs such as evaporation, salt diffusion, temperature discrepancy, and layer mixing profoundly and significantly affected their expan-sion globally. A novel experimental solar collector configuration to overcome the challenges of the conventional solar ponds (solar collectors) is investigated, there is no water body and no salinity gradient to build; it is entirely a collector with no water body. The experimental unit was constructed in an arid area. It is basically a cylindrical tank with a total depth of 1.4 m with three zones or layers to store heat namely, paraffin wax layer (10 cm thickness). The paraffin layer was covered with a layer of coal with a thickness of 30 cm. On the top of coal layer, an air gap with a thickness of 80 cm was left. A clear plastic cover with a thickness of 0.2 cm was utilized to cover the constructed layers and making the air gap. The experimental unit was monitored, and temperature measurements were collected for the period of 17/7/2021- 30/9/2021. The results demonstrated that temperature of the paraffin wax layer reached more than 48 °C in a short period and with a small day and night discrepancy (1 °C). Temperature of the paraffin layer remained constant around 43 °C even in night-time during the period of the study. Furthermore, the results showed that temperatures of coal layer and air gap reached the maximum at the daytime of 53 °C and 71 °C respectively with a clear discrepancy between day and night. The results of the present study are encouraging for more investigations in this new direction of solar collectors.

Salinity-gradient solar pond: History and progress review

A salinity gradient solar pond (SGSP) is a large and deep artificial basin of layered brine, which collects and stores-simultaneously-solar energy for use in various applications. Experimental and theoretical studies have been launched to understand the thermal behavior of SGSPs, under different operating conditions. This article then traces the history of SGSPs, from their natural discovery to their current artificial applications and the progress of studies and research, according to their chronological sequence, in terms of determining their physical and dynamic aspects, their operation, management and maintenance. It has extensively covered the theoretical and experimental studies, as well as the direct and laboratory applications of this technology, especially the most famous and influential in this field, classified according to the aspect covered by the study, with a comparison between the different results obtained. In addition, it highlighted the latest methods to improve the performance of an SGSP and facilitate its operation, such as the use of a magnetic field and the adoption of remote data acquisition, in the aim of expanding research and enhancing the benefit of this technology.

The effect of porous media on the thermal storage performance of salinity-gradient solar pond

A solar pond is a system that uses a salt concentration gradient to store heat. The application of the system is conducive to solving the problems of long production cycles, low brine temperature, and salt algae in the solar pond lithium extraction process and the solar pond potassium enrichment process. Based on this, our research group laid porous media at the bottom of the solar pond and utilized the heat storage and adsorption capacity of porous media to improve the thermal storage performance of the solar pond. The experimental results show that foam ceramics have good thermal storage performance and the ability to reduce turbidity. Laying foam ceramics on the bottom of the solar pond can not only increase the thermal storage performance of LCZ but also help reduce the turbidity of the pool water. After adding porous media, the heat extraction position of the solar pool moves from the junction of LCZ and NCZ to the bottom of LCZ. In addition, adding transparent film on the upper surface of the solar pond is also conducive to improving the thermal storage performance of the solar pond and reducing the turbidity of the solar pond.

Benefits of an innovative polygeneration system integrated with salinity gradient solar pond and desalination unit

Solar energy accumulation, low-temperature thermal heat stockpiling, and more sustained performance are the attractive specifications of a salinity-gradient solar pond (SGSP). Extracted low-grade heat from these components can be employed for various residential applications such as electric power, cooling load, and freshwater production. An innovative energy generation system consisting of a flat plate collector (FPC), single-stage absorption chiller (SSAC), thermoelectric generator (TEG), desalination unit, NaClO plant, SGSP, and a wind turbine farm is proposed. The theoretical investigations demonstrate the multidimensional benefits of the system throughout the year. A comprehensive thermodynamic, economic, and exergoenvironmental assessments of the annual operation of the system is conducted. For a comparative evaluation of the system performance, the individual scenarios are outlined. Results from energy and exergy studies show that the associated efficiencies are 27.3 % and 19 %, respectively. Also, the system has the capability to supply a cooling load capacity of 2391 kW, net electricity power of 583.9 kW, hydrogen of 1.48 m3/s, freshwater of 0.01445 m3/s, and sodium hypochlorite of 0.001416 kg/s. Moreover, the payback period and the factor of environmental damage effectiveness for the system are 3.2 years and 2.223, respectively.

Experimental investigation of salinity gradient solar pond with nano-based phase change materials

ABSTRACT Heat energy storage is pivotal in modern times. However, the technology to efficiently stored heat energy is still in the research stage. Heat energy storage is possible through phase change material, exothermic chemical reactions, and solar ponds. The latter uses a natural phenomenon that relies on solar Energy and convective heat transfer. Solar ponds can store more heat energy throughout the day than other processes and meet higher energy demands. The working principle of a typical solar pond can be adopted to develop a compact setup that can store sufficient heat energy to meet the heat energy demand of a small family. Salinity gradient solar ponds are used for heat storage to meet the demand of rural and urban communities in arid and semiarid zones around the globe. Often the solar ponds are constructed on the ground by storing a large volume of salt water. The performance of the solar pond is affected by the intensity of solar radiation. In this study, a compact solar pond is constructed using aluminum plates and a glass cover. Sea water was used to store solar radiation in this experiment. The experiment was carried out in South India during the winter season when the intensity of solar radiation was minimum. The study aims to determine the performance of the solar pond and its thermal properties under low sunshine. Heat storage mediums comprising paraffin wax and additives of nanoparticles of graphene and carbon nanotubes were used to enhance the heat storage capacity of the solar pond. It was found that compared to the simple salinity gradient solar pond, the heat storage medium with carbon nanotube nanoparticles increased the maximum temperature attained by 26.5%. The carbon nano tubes infused phase change material increased the heat transfer, heat transfer coefficient, and the heat stored in the saline water by 244%, 713%, and 83.3%, respectively. It is concluded that the carbon nano tubes and phase change material augmented the performance of the solar pond even while the intensity of solar radiation was low.

Design and performance analysis of salinity gradient solar pond under different climatic and soil conditions.

A salinity gradient solar pond (SGSP) is capable of storing a significant quantity of heat for an extended period of time. It is a great option for providing hot water at a reduced energy cost. Additionally, SGSP is used in low-temperature industrial applications such as saltwater desalination, space heating, and power generation. Solar pond thermal performance is dependent on a variety of operational variables, including the soil conditions, the climate of the particular site, the thickness of the solar pond layers, the depth of the water table, and the salt content of the pond. As such, this study examines the thermal performance of a solar pond under a variety of operational conditions. The solar pond model is used to test the thermal performance by simulating two-dimensional heat and mass transport equations. The equations are solved using the finite difference technique utilizing MATLAB® scripts. Salt distributions and temperature profiles are computed for a variety of factors influencing SGSP's thermal performance. The main distinguishing variables influencing the thermal performance of SGSP are soil conditions, such as soil texture, types, the moisture level in soil, and water table depth. The final findings indicated that the fine sand dry soil performed better than the other soil types owing to its poor heat conductivity. The economic results indicated that the period of return (POR) of the intended system is around 2 years. The solar pond construction costs such as excavation, transportation, salt and lining, were considered based on the local prices. This modeled study extracted the greatest possible energy is 110W/m2, with the fine sand dry at 62.48°C lowest temperature. This study suggested that the climatic conditions of Lahore is better than climatic conditions of Islamabad. Additionally, deeper water tables are suggested for improved thermal performance of the pond.

Transient behavior of a salinity gradient solar pond under Mediterranean climate

Abstract This paper aims to investigate the transient behavior of a salinity gradient solar pond(SGSP) under Mediterranean climate. For this propose, a 2D numerical model is developed in which the absorption of solar radiation by different layers of saline water, the wind effect at free surface, the heat losses and the development of the double-diffusive convection in the lower and upper convective zones are considered. The governing equations of continuity, momentum, thermal energy and diffusion are solved using the finite volume method with SIMPLE algorithm. The validity of the numerical model developed in Fortran95 is achieved through the comparisons of the results computed with the available numerical and experimental results obtained by literature studies. Results show that the developed numerical model can predict transient behavior of the SGSPs with a good accuracy. As an application of this model, temperature, salt concentration, energy stored and storage efficiency variations of a proposed SGSP are analyzed under Mediterranean climate. The results show that the lower convective zone(LCZ) temperature increases from 15 °C to around 95 °C whereas the temperature of the upper convective zone(UCZ) varies sinusoidally depending on that of the ambient air. Furthermore, the salt concentration of the LCZ decreases from 250kg/m3 to around 248kg/m3 while that of the UCZ increases from50 kg/m3 to about 52kg/m3. Additionally, the thermal energy stored is around 135MJ with an efficiency of about 38% which confirms the capacity of the SGSP to store thermal energy as sensible heat.

Solar Energy Driven Membrane Desalination: Experimental Heat Transfer Analysis

In the direct contact membrane distillation (DCMD) system, the temperature polarization due to boundary layer formation limits the system performance. This study presents the experimental results and heat transfer analysis of a DCMD module coupled with a salinity gradient solar pond (SGSP) under three different flow channel configurations. In the first case, the feed and permeate channels were both empty, while in the next two cases, the feed and permeate channels were filled with a porous spacer material. Two different spacer geometries are examined: 1.5 mm thick with a filament angle of 65°, and 2 mm thick with a filament angle of 90°. The study considers only the heat transfer due to conduction by replacing the hydrophobic membrane normally used in a DCMD module with a thin polypropylene sheet so that no mass transfer can occur between the feed and permeate channels. The Reynolds number for all three configurations was found to be between 1000 and 2000, indicating the flow regime was laminar. The flow rate through both the feed and permeate sides was the same, and experiments were conducted for flow rates of 5 L/min and 3 L/min. It has been found that the highest overall heat transfer coefficient was obtained with the spacer of 2 mm thickness and filament angle of 90°.

Comparing and optimizing the potential advantages of a salinity-gradient solar pond for either absorption-based or ejector-based refrigeration cycles combined with thermoelectric generators

This study compares the applicability of two popular refrigeration cycles for air-conditioning, i.e., absorption-based (Model 1) and ejector-based (Model 2), combined with a salinity-gradient solar pond. Indeed, there exists a gap in comparing the performance of solar pond-based refrigeration cycles to which this study intends to respond. In addition, utilizing zeotropic mixtures in an ejector refrigeration cycle integrated with a solar pond and selecting the most suitable zeotropic for such a framework has not been regarded in the literature. Both models are boosted using thermoelectric generators for low-temperature waste heat recovery and electricity generation. Energy, exergy, economic, and environmental investigations with a net present value analysis are implemented, and multi-objective optimization using non-dominated sorting genetic algorithm-II is conducted. As another principal point, this paper performs a case study to illustrate the performance of models regarding an actual climate condition. Results show that using Butane-R143a zeotropic increases the advantages of Model 1; however, Model 2 is the most suitable selection for the solar pond. According to the optimum state, Model 1 possesses exergy efficiency and Levelized cost of products of 17.93% and 0.12 $/kWh, which are 0.84 percentage points and 83% better than Model 2. But Model 2 has a better environmental performance by mitigating 22% further carbon dioxide than Model 1.

Expert systems and the prospects of artificial intelligence for the automatic supervisory control of salinity gradient solar ponds

Salt Gradient Solar Ponds (SGSPs) are conventionally operated wholly manually. They hence suffer from a loss of efficiency for substantial durations when disturbed by natural diffusion and environmental elements such as temperature variation, solar radiation, and wind. They also impose considerable operational costs and time when a repair is unavoidable. Here, a Zero-Discharge Closed Cycle (ZDClC) is proposed for sustainable implementation of control architectures. We then define the SGSP as a control system and propose an automatic approach that uses Artificial Intelligence (AI) to mimic experts’ actions during repair operations. More specifically, an Automatic Supervisory Controller (ASC-SGSP) is proposed that decomposes the pond into several uniform sublayers according to their thicknesses and salt concentrations. The automated supervisor then uses a decision tree analysis of pond stability to determine the sequences of injection/suction actions to guarantee the pond stability and prevent layer overturning. An on–off subcontroller then directs the chosen sublayer’s salt density to its desired value. The supervisory structure is general and can operate with either the proposed open-loop or closed-loop configurations. Results indicate the potential utility of AI and expert systems as a successful paradigm for SGSP control. Specifically, the proposed approach is examined in a simulated pond under several scenarios challenging its efficiency, adaptivity, robustness, and constraint handling properties. The ASC-SGSP fulfills the automatic control requirements during either open/closed-loop configurations and regulates the desired salinity levels under parameter constraints and uncertainties, even when the SGSP parameters are perturbed by as much as 50%.

Practical design and construction of solar ponds

Over the last four decades, salinity gradient solar pond (SGSP) science and technologies have advanced in practical projects. In this work, we show that understanding a salinity gradient solar pond's purpose provides the focus for preparing a preliminary design and physical configuration. This paper aims to share lessons learned in designing and constructing the El Paso Solar Pond. Features, factors, and facets of solar pond design and construction are presented straightforwardly to inform and guide planning for future work. Emphasis is on sodium chloride-based ponds, the base salt used for the El Paso Solar Pond. However, lessons learned are pertinent to additional salt source configurations. Reference to solar ponds operating in Australia and Israel provides design and construction insights. Careful design and planning prior to construction ensure the solar pond operates reliably and sustainably.

Soret and Dufour effects on double-diffusive convection in a salinity gradient solar pond

A mathematical model for multi-diffusive convection with Soret and Dufour effects is developed to simulate the behavior of a salinity gradient solar pond (SGSP) in this study. The influence of Soret and Dufour effects on the double-diffusive natural convection of the SGSP and also the distribution of velocity, temperature and salt concentration fields are discussed using distribution functions of the lattice Boltzmann method. The results show that the Soret effect plays a role in promoting temperature and concentration diffusion, while the Dufour effect has a certain suppression influence on temperature diffusion and improves the concentration diffusion. Moreover, the influence of the Soret effect in the SGSP is more obvious than the Dufour effect on double diffusion. Simultaneously, the relationship between the buoyancy ratio and the Soret and Dufour effects is also discussed.

Integration of a solar pond in a salt work in Sabzevar in Northeast Iran

The process of salt manufacture in a salt work in Sabzevar in Northeast Iran is presented. A multi-faceted application to integrate a salinity gradient solar pond as part of the salt work process is presented addressing the reduction of parasitic energy losses such as the energy used for salt rock crushing and saving the amount of fossil fuel (natural gas) needed for brine heating. The solar pond with an area of 100 × 100 m2 and depth of 3 m is proposed to be constructed on the site of salt work. A partitioning wall with some opening heights equal to the desired position of the interface of lower convective (LCZ) and non-convective zones (NCZ) in its lower section, divides part of the area of this pond, say 5 percent or 500 m2. The separated area is designated to act as a salt charger and salt storage. The rock salt deposited in the salt charger dissolves into the LCZ of the pond and produces hot saturated brine solution. Results indicate that 100 tons of pure salt may be obtained from the extraction of 320 m3 of hot saturated brine consisting of 73 wt% water and 27 wt% salt. This is the nominated daily salt production of the factory. The proposed system will help to streamline the process of salt manufacture and reduce the environmental footprint.Using locally available meteorological data of Sabzevar, it is shown that such a pond may produce hot brine at an average temperature of 65 °C in summer and 37 °C in wintertime with a loading of 20% of the input irradiation. The gradient zone of the pond may be setup by placing a layer of low salinity water over saturated brine, allowing for salt diffusion to take place. Formation of large amplitude surface waves increases the salt diffusion and a salinity profile will develop in few months.A parametric study was performed to assess the enviro and economic effects of the proposed 10,000 m2 solar pond. The amount of fresh water to be injected to the solar pond is calculated to compensate for evaporation of pond surface as well as production of concentrated brine containing 100 tons of salt per day. Computer simulation shows that about 59,000 MJ/day thermal energy may be extracted from the pond in June. This is equal to a saving of about 1,576 kg/day of methane. Considering the price of methane this would be a financial saving of 283 $/day. The rate of reduction in CO2 emission is estimated to be 4,335 kg/day in June. Considering a carbon price of 30 $/ton, the above reduction in CO2 will be equivalent to savings of 130 $/day related to the environment. These calculations are extended to all months of the year and results presented.For demonstration, feasibility of using an existing old cylindrical fuel storage tank (2,000 m3, 3.3 m deep) as a container for a 600 m2 outdoor solar pond nearby the factory buildings, is proposed for pilot study. The shading effect is examined by scaling down a 3D model of the reservoir and its adjacent buildings for different months of the year, using Helidon device available at RMIT University of Australia. According to the simulation performed, it seems that the presence of buildings around the fuel tank does not have a significant shading effect on the surface of the demonstration solar pond.

The application of an enhanced salinity-gradient solar pond with nucleation matrix in lithium extraction from Zabuye salt lake in Tibet

The utilization of salinity-gradient solar ponds (SGSPs) to extract lithium from salt lake brine is one of the most direct and effective uses of solar energy. The Qinghai-Tibet Plateau in China is rich in unique solar energy resources, as well as various types of salt lakes with abundant lithium resources. Among them, Zabuye salt lake in Tibet is a typical lithium-rich carbonate salt lake, and it has successfully realized the industrialization of lithium extraction from brine for the first time by using the SGSP. In recent years, with the continuous improvement of lithium resource market, the demand for lithium has further grown. There are some bottleneck problems restricting the lithium carbonate production in the lithium extraction technology with traditional SGSPs, which must be overcome, such as the slower heating rate, smaller heating amplitude, longer production cycle, lower crystallization efficiency and so on. From the angle of green environmental protection and high-efficiency technology, this research focused on the temperature field and salinity field distribution of the traditional SGSP and the special crystallization behavior of lithium carbonate, and carried out experimental research on process optimization in Zabuye mining area. Based on the heterogeneous nucleation theory, the use of an enhanced SGSP with a nucleation matrix for assisting the crystallization of lithium carbonate was proposed. The change of crystallization behavior of lithium carbonate, the influence of matrix materials and the spatial distribution on the crystallization effect were investigated. The results show that the enhanced SGSP with the nucleation matrix has a significant effect of increasing the production of lithium carbonate, and the lithium mixed salt attached to the nucleation matrix is of a higher grade and a lower moisture content. The yield per unit area of lithium carbonate on the nucleation matrix made of the gauze and plastic net is equivalent to that on the slope and bottom of the solar pond, and the grade of lithium carbonate approaches 80 %. The yield per unit area of lithium carbonate on the nucleation matrix made of tumbleweed is about four times as much as is achieved with other materials and the crystallization exceeds expectations. It is concluded that the application of the enhanced SGSP with the nucleation matrix can improve the crystallization efficiency, the output and the grade of lithium carbonate to a certain extent and this optimization technique will provide an important theoretical basis and application support for green, efficient development of lithium resources from salt lake brine.

MATHEMATICAL MODELING AND 3D NUMERICAL SIMULATION OF A SOLAR POND EXPOSED TO TWO SOLAR REFLECTORS

The salinity gradient solar pond is simply a pool of water with different mass percentages of salt that collects and stores solar thermal energy. When solar radiation comes into contact with the water in the basin, it will become the site of two opposing actions, namely the effect of temperature which expands the liquid in its lower parts, thus reducing their density and favoring ascending currents coming from Archimedes' buoyancy and the effect of salinity which increases this density and prevents the liquid from rising. As a result, the converted thermal energy is trapped in the bottom of the basin. The more the temperature of the water increases, the more the fields of application in different uses of this thermal energy widen. As it is also important to indicate that the high temperature of the storage area allows ponds located in cold areas to save their operating temperatures during the winter period. In an attempt to increase the temperature of the bottom water, we have installed 2 solar reflectors on both sides of the pond which have the role of reflecting solar radiation and returning it to the surface of the pond. This has a positive influence on its thermal performance. The mathematical model governing the pond dynamics is based on the special 3-direction heat equation with an initial condition and 6 boundary conditions. The finite volume discretization method in 3D was used, the Camsol software was applied for finer steps. The numerical results showed that the pond with reflectors recorded a temperature exceeding $ 13\degree\text{C} $ compared to the pond without reflectors. Convergence, consistency and stability were discussed. %and stability were discussed.‏