Increasing the storage capacity of a solar pond by using solar thermal collectors: Heat extraction and heat supply processes using in-pond heat exchangers

• Published in: Solar energy Vol. 171; pp. 112 - 121
• Main Authors: Alcaraz, A., Montalà, M., Valderrama, C., Cortina, J.L., Akbarzadeh, A., Farran, A.
• Format: Journal Article Publication
• Language: English
• Published: New York Elsevier Ltd 01-09-2018; Pergamon Press Inc
• Subjects: Cold season; Cylindrical tanks; Efficiency; Emmagatzematge; Energia; Energies; Energy storage; Heat; Heat exchangers; Heat extraction/supply; Heat transfer; Heat treatment; Pilot plant; Pilot plants; Ponds; Power supply; Radiació solar; Salinity gradient solar pond; Salinity gradient solar pond Energy storage Pilot plant Solar radiation Solar collectors Heat extraction/supply Efficiency; Solar collectors; Solar energy; Solar heating; Solar ponds (heat storage); Solar radiation; Storage capacity; Temperature; Water storage; Àrees temàtiques de la UPC; Pilot plant; Efficiency; Solar collectors; Solar radiation; Heat extraction/supply; Salinity gradient solar pond; Energy storage
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2018.06.061

•An experimental solar pond integrating solar collectors is presented.•Heat extraction/supply experiments are performed using heat exchangers.•Solar collectors increases efficiency of solar pond during the cold season.•Large amount of heat extracted allows a greater storage capacity of the solar pond.
In this study, an experimental investigation of the performance of a salinity gradient solar pond (SGSP) integrating solar collectors is presented. The SGSP is located in Barcelona (Spain) and has a cylindrical tank 3 m in height and 8 m in diameter with a total area of 50 m2. For this purpose, four solar thermal collectors (10 m2) are integrated, as an external source of heat, with the solar pond pilot plant in order to increase the storage capacity and its overall efficiency. The aim of this study is to evaluate heat extraction and heat supply processes from and to the SGSP under different seasonal conditions. Two in-pond heat exchangers are used, a conventional one situated on the bottom of the pond and a second one covering the lateral wall area of the pond. Heat extraction and supply experiments are performed using both heat exchangers individually or both at the same time. The experiments are conducted under two different seasonal temperature conditions: winter (February and March) and summer (July). The variations of the temperature inside the pond during the heat extraction/supply tests are monitored and analyzed. The results have indicated that the use of solar collectors as an extra source of heat for the solar pond led to a 50% increase in the daily efficiency during the cold season tests, while heat extraction only appeared as the best option during the warm season tests. Higher daily efficiency and heat supply results can only be obtained if large amounts of heat are extracted, otherwise, the daily efficiency of the solar pond could decrease. Finally, the solar collectors can be considered a good alternative for avoiding a significant decrease in solar pond temperatures (especially during the cold season), which would not only result in a significant energy storage efficiency improvement but also increase the capacity of the solar pond to supply heat to an external application.