دراسة بركة شمسية لتسخين المياه في كربلاء المقدسة

Investigation of Performance of Solar Pond for Water Heating in Holly Karbala

Abstract

Solar energy is considered a clean, free and easily obtainable source, therefore, It has widely used in recent years to solve the problems of energy shortages in many countries of the world. There are many techniques that can be adopted to use solar energy such as solar collectors, solar ponds and photocells for water heating system.
In the present work, A three-tiered solar pond with different salt concentrations was built, and depth is 1 m, with a surface area of 7.29 m2. Gradient salt solar pond was used to collect and store solar energy. The stored energy was extracted from the solar pond by using a heat exchanger. Thermal characteristics of the solar pond such as brine temperature, useful energy and thermal efficiency were experimentally and theoretically investigated. Modifications were done to improve these characteristics. The modifications concerned of using the three different concentration of the sodium chloride NaCl mixed with potassium chloride KCl. Also, reflective mirrors connected with a solar tracking system were installed on sides of the solar pond. These modifications were experimentally conducted for individual case. Moreover, the flowrate of water inside the heat exchanger was investigated. The current modifications were done to show their effect on the solar pond efficiency in term of the amount of the obtain energy .
To optimize each case, MATLAB software was used. This case is the use of NaCl salt at a concentration of 26% with the presence of both the reflective mirrors and the solar tracking system. Compare the experimental results with the theoretical results to show the difference percentage between them. The results showed that the sodium chloride salt is better than the potassium chloride salt and the 26% is the best concentration compared to the concentrations of 11% and 19%. The results also showed that using the reflective mirrors with and without the solar tracker can enhance these characteristics. Also, the results indicated that reducing the flowrate of water through the heat exchanger improve the solar pond efficiency.
The improvement in the solar pond efficiency was obtained from the experimental and theoretical work. Experimentally, it was demonstrated that using the sodium chloride salt at a concentration of 26% with the controlled tracking reflective mirrors increased the solar pond temperature by about 11% as compared with potassium chloride. Also, the useful energy and the thermal efficiency of the solar pond were increased by approximately 20% and 11%, respectively. Water flowrate inside the heat exchanger of 0.5 L/min provided best results for the solar pond efficiency and the extracted energy as compared with the flowrates of 1L/min and 0.75 L/min.
Theoretically, The data entered into the program included ambient temperatures, thickness of layers, brine properties, and other factors for calculating temperatures using the finite difference method.
The agreement between the experimental and theoretical results were acceptable, not exceed 9%.