Gradient-Zone Erosion by Extraction in Solar Ponds

1995 ◽  
Vol 117 (2) ◽  
pp. 144-150 ◽  
Author(s):  
J. Estevadeordal ◽  
S. J. Kleis
Keyword(s):  
Steady State ◽  
Salinity Gradient ◽  
Operating Conditions ◽  
Density Difference ◽  
Finite Density ◽  
Gradient Zone ◽  
Solar Ponds ◽  
Solar Pond ◽  
Flow Parameters ◽  
Storage Zone

The erosion the dynamically stable gradient zone of a salinity-gradient solar pond, due to the extraction of fluid from the storage zone, is numerically investigated. The effects of fluid withdrawal rate, density stratification level, pond and diffuser geometries, and diffuser placement are considered. It is found, for a typical salinity-gradient solar pond with uniform salinity in the storage zone and a continuous salinity gradient above that a finite amount of fluid entrainment from the gradient zone is inevitable. That is, a finite density difference across the interface is always required for a finite extraction rate under steady-state conditions. The magnitude of the density difference is predicted as function of the geometric and flow parameters. From the results, it is possible to predict the total amount of fluid entrained from the gradient zone as the pond reaches steady-state for prescribed operating conditions.

Effect of Water Distribution Ways on the Operation of Solar Pond

2013 ◽  
Vol 805-806 ◽  
pp. 74-77
Author(s):  
Chun Juan Gao ◽  
Qi Zhang ◽  
Liang Wang ◽  
Ying Wang ◽  
Xi Ping Huang
Keyword(s):  
Water Distribution ◽  
Salinity Gradient ◽  
Convective Zone ◽  
The Body ◽  
Solar Ponds ◽  
Solar Pond ◽  
Storage Zone ◽  
Small Model ◽  
Laboratory Tank ◽  
Salt Diffusion

An experimental study on the evolution of the salinity profiles in the salinity gradient solar ponds was executed using a small model pond. The body of the simulated pond is a cylindrical plastic tank, with 50 cm height and 45 cm diameter. The salinity gradient was established in the laboratory tank by using the salinity redistribution technique. The measurements were taken during a period of 20 days of experimentation. This period of time allowed the existence of salt diffusion from the storage zone to the surface. Results obtained from this study show that when the ratio of brine/water is 1/1, the salinity gradient layer can sustain a longer time and the lower convective zone is thicker, which is benefit to store solar energy.

Gradient Zone Constraints in a Salt-Stratified Solar Pond

1982 ◽  
Vol 104 (4) ◽  
pp. 280-285 ◽  
Author(s):  
T. A. Newell ◽  
R. F. Boehm
Keyword(s):  
Steady State ◽  
Sodium Chloride ◽  
Energy Performance ◽  
Operating Conditions ◽  
Temperature Gradients ◽  
Gradient Zone ◽  
Solar Pond ◽  
Temperature Operating ◽  
Concentration Levels ◽  
Specific Amount

An operational condition is defined for a salt-stratified solar pond. A criterion based on empirical evidence is formulated which shows a limit is approached as steady operating conditions are attained. For sodium chloride ponds, the criterion indicates a dependence between salt and temperature gradients during steady-state conditions. At the present time, appropriate data for explaining the physical basis of this relationship are not available. Significant results are found as a result of the gradient zone criterion. First, the gradient zone criterion leads to an explanation for the formation of an upper convecting zone. Results obtained with the gradient zone criterion relate to salt maintenance in a pond. Depending on the temperature operating conditions of a pond, a specific amount of salt must be in the pond. Also, salt concentration levels maintained in the upper and lower convecting zones are shown to significantly affect a pond’s thermal energy performance.

Assessing the Maximum Stability of the Nonconvective Zone in a Salinity-Gradient Solar Pond

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
A. A. Abdullah ◽  
K. A. Lindsay
Keyword(s):  
Salinity Gradient ◽  
Fluid Velocity ◽  
Weather Conditions ◽  
Convective Zone ◽  
Heat Extraction ◽  
Solar Pond ◽  
Maximum Stability ◽  
Storage Zone ◽  
The Stability

The quality of the stability of the nonconvective zone of a salinity-gradient solar pond (SGSP) is investigated for an operating protocol in which the flushing procedure exactly compensates for evaporation losses from the solar pond and its associated evaporation pond. The mathematical model of the pond uses simplified, but accurate, constitutive expressions for the physical properties of aqueous sodium chloride. Also, realistic boundary conditions are used for the behaviors of the upper and lower convective zones (LCZs). The performance of a salinity-gradient solar pond is investigated in the context of the weather conditions at Makkah, Saudi Arabia, for several thickness of upper convective zone (UCZ) and operating temperature of the storage zone. Spectral collocation based on Chebyshev polynomials is used to assess the quality of the stability of the pond throughout the year in terms of the time scale for the restoration of disturbances in temperature, salinity, and fluid velocity underlying the critical eigenstate. The critical eigenvalue is found to be real and negative at all times of year indicating that the steady-state configuration of the pond is always stable, and suggesting that stationary instability would be the anticipated mechanism of instability. Annual profiles of surface temperature, salinity, and heat extraction are constructed for various combinations for the thickness of the upper convective zone and storage zone temperature.

Thermal Heat Storage Gain of Salinity Gradient Solar Pond Using Evacuated Tube Solar Collectors

2015 ◽  
Vol 1113 ◽  
pp. 800-805 ◽  
Author(s):  
Baljit Singh ◽  
Muhammad Fairuz Remeli ◽  
Alex Pedemont ◽  
Amandeep Oberoi ◽  
Abhijit Date ◽  
...  
Keyword(s):  
Large Scale ◽  
Heat Storage ◽  
Salinity Gradient ◽  
Heat Energy ◽  
Working Fluid ◽  
The Sun ◽  
Solar Ponds ◽  
Solar Pond ◽  
Evacuated Tube Collectors ◽  
Evacuated Tube

This paper investigates the capability of running a system which uses hot fluid from solar evacuated tube collectors to boost the temperature and overall heat storage of the solar pond. The system is circulated by a solar powered pump, producing heat energy entirely from the incoming solar radiation from the sun. Solar evacuated tube collectors use a renewable source of power directly from the sun to heat the working fluid to very high temperatures. Solar ponds are emerging on the renewable energy scene with the capacity to provide a simple and inexpensive thermal storage for the production of heat on a large scale. The results of the performance of the system show a significant heat energy increase into the solar ponds lower convective region, increasing the overall performance of the solar pond.

The Influence of Height of LCZ on the Salinity Diffusion of Solar Pond

2013 ◽  
Vol 448-453 ◽  
pp. 1521-1524
Author(s):  
Chun Juan Gao ◽  
Qi Zhang ◽  
Hai Hong Wu ◽  
Liang Wang ◽  
Xi Ping Huang
Keyword(s):  
Solar Energy ◽  
Fresh Water ◽  
Salt Water ◽  
Salinity Gradient ◽  
Good Method ◽  
Convective Zone ◽  
Solar Ponds ◽  
Solar Pond ◽  
Salt Gradient ◽  
And Diffusion

The solar ponds with a surface of 0.3m2were filled with different concentration salt water and fresh water. The three layer’s structure of solar ponds was formed in the laboratory ponds by using the salinity redistribution. The performance and diffusion of salinity were xperimentally in the solar pond. The measurements were taken and recorded daily at various locations in the salt-gradient solar pond during a period of 30 days of experimentation. The experimental results showed that the salinity gradient layer can sustain a longer time when the lower convective zone is thicker, which is benefit to store solar energy. Therefore, properly increasing the height of LCZ is a good method to enhance the solar pond performance.

scholarly journals Investigation of saturation temperature in solar pond for different sizes

2020 ◽  
Vol 24 (5 Part A) ◽  
pp. 2905-2914 ◽  
Author(s):  
Haci Sogukpinar ◽  
Ismail Bozkurt
Keyword(s):  
Saturation Temperature ◽  
Side Wall ◽  
Equilibrium Temperature ◽  
Convective Zone ◽  
Discrete Ordinates ◽  
Solar Ponds ◽  
Solar Pond ◽  
Storage Zone ◽  
Zone Depth ◽  
Depth Ranges

This paper deals with the modelling of solar ponds for different sizes to calculate saturation time and temperature by using discrete ordinates method. The modeled solar pond is a subsoil type and aimed to minimize the heat losses by isolating side wall and ground with foam with the thickness of 10 cm in all cases. In the model, upper convective zone is 10 cm deep and non-convective zone consists of five layer and each layer is 10 cm deep and storage zone depth ranges from 40-400 cm. Therefore, the solar pond totally consists of seven layers. The saturation temperature was found to be about 322 K for 12 different solar pond. For a depth of 40 cm, the equilibrium temperature was reached in 1000 hours, 1300 hours for 60 cm, 1400 hours for 80 cm, 1500 hours for 100 cm, 1600 hours for 120 cm, 1750 hours for 1140 cm, 1800 hours for 180 cm, 2700 hours for 200 cm, 1800 hours for 250 cm, 3400 hours for 300 cm, and 6000 hours have passed for 400 cm. As the depth increases, time to reach to the equilibrium temperature increases but increment amount of water and time to reach equilibrium temperature shows a proportional increase. At the same time we calculated that, when we increase the width of the pond by keeping the depth constant, the saturation temperature and the time did not changed for the seven different cases.

scholarly journals Performance comparison of aboveground and underground solar ponds

2018 ◽  
Vol 22 (2) ◽  
pp. 953-961 ◽  
Author(s):  
Haci Sogukpinar ◽  
Ismail Bozkurt ◽  
Mehmet Karakilcik
Keyword(s):  
Performance Evaluation ◽  
Density Distribution ◽  
Structural Parameters ◽  
Performance Comparison ◽  
Underground Construction ◽  
Gradient Zone ◽  
Solar Ponds ◽  
Convective Heat Loss ◽  
Solar Pond ◽  
Temperature Distributions

This paper deals with the modeling of two different solar ponds which has some different structural parameters such as aboveground and underground, and its performance evaluation. The solar pond system generally consists of three zones, and the densities of these zones decrease from the bottom of the pond to the surface. The most significant decrease in the density distribution of the salt between bottom and up of the pond is the gradient zone. The convective heat loss in the solar pond is prevented with this zone. In this study, aboveground and underground solar ponds were modeled at the same dimensions, but different structural parameters in the same conditions. In this model, the temperature distributions of the solar pond were obtained during a year. The thermal performances of the solar pond were calculated and the results were compared with an experiment. This study shows that the efficiency of the aboveground solar pond is observed to be a maximum of 25.93% in July, a minimum of 4.53% in January. Furthermore, the efficiency of the underground solar pond is observed to be a maximum of 21.49% in July, a minimum of 6.55% in January. This study indicates that the underground construction of solar ponds, designed to be insulated using appropriate insulation materials, is found to be more efficient with respect to the aboveground pond.

Revisiting Gradient Layer Heat Extraction in Solar Ponds Through a Realistic Approach

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Sunirmit Verma ◽  
Ranjan Das
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Diffusion Rate ◽  
Heat Extraction ◽  
Gradient Zone ◽  
Solar Ponds ◽  
Storage Zone ◽  
Salt Diffusion ◽  
The Ideal

Abstract In this paper, the concept of heat extraction from the gradient zone (GZ) in solar ponds has been analyzed in a more realistic manner to overcome the drawbacks of previously conducted studies. For this purpose, a net heat transfer coefficient has been invoked to investigate the heat transfer occurring from the GZ to the exchanger installed in this zone, in addition to the storage zone (SZ). Analytical solutions for temperature profiles in the GZ and the corresponding exchanger have been obtained which are further used to investigate various aspects of the thermal performance of the pond. The consideration of realistic heat transfer across the GZ exchanger reveals that the ideal thickness of GZ yielding maximum power output is always under-predicted by the idealized assumption of the literature. Unlike intuitive perception, the conventional assumption of an infinite heat transfer coefficient does not affect the pond stability because, for all practical purposes, the critical salt diffusion rate predicted by it is always larger than the actual critical value required for ensuring stable pond operation. However, as expected, the rate of exergy destruction caused by the pond’s operation is found to be underestimated by the idealized assumption. This study provides a useful analytical tool to make more realistic predictions on various performance parameters of solar ponds utilizing the heat stored in their GZ.

Gradient-Zone Erosion in Seawater Solar Ponds

1997 ◽  
Vol 119 (1) ◽  
pp. 2-7 ◽  
Author(s):  
J. Shi ◽  
R. A. Hart ◽  
S. J. Kleis ◽  
R. B. Bannerot
Keyword(s):  
Gulf Coast ◽  
Operating Conditions ◽  
Experimental Program ◽  
Entrainment Rate ◽  
Laboratory Studies ◽  
Cold Temperatures ◽  
Gradient Zone ◽  
Solar Ponds ◽  
Texas Gulf Coast ◽  
Thermal Refuge

An experimental program has been conducted to examine the feasibility of using seawater solar ponds in mariculture operations along the Texas gulf coast to protect fish crops from the potentially lethal, cold temperatures experienced in outdoor ponds. Seawater solar ponds in the form of floating thermal refuge areas are proposed as a method for reducing the loss of heat from small sections of a pond. Gradient zone erosion under various ambient and operating conditions is examined. Comparisons with previous laboratory studies show a much lower entrainment rate in the natural environment. For conditions which are typical of those encountered in mariculture pond operation, the entrainment rate was found to depend only weakly on the Richardson number. For these conditions, a simple (linear) correlation of entrainment rate with wind speed was developed.

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