Thermal performance of a hybrid steel-concrete tank section for thermal energy storage in concentrated solar power plants

Several studies of thermocline molten salt tanks have proven to be suitable for thermal energy storage systems. However, there is a lack of experimental investigations performed. The building of a hybrid section and its assessment operating as a thermocline tank are the main objectives of this research work. The novelty is to prove the performance of the hybrid tank concept made of a thick concrete layer and a thin steel liner. The tank section studied comprises the following layers of materials: a steel liner, an air gap interface, a high thermal concrete layer and insulating materials. The thermal response was monitored using thermocouples located between the layers, at different heights and widths of the whole tank section length. The performance during the commis-sioning (first heat) and the operation (3 heat/cool cycles between 200/500 degrees C) of the tank section is analysed. The thermal appropriateness of using concrete as part of the thermocline tank has demonstrated the suitability and good thermal response up to 425 degrees C showing isolating and thermal inertia. The presence of the air gap interface between the steel liner and the concrete generates a heat convection current with local energy gradients along the section height.