Evaluation of a concrete–graphite hybrid mixture for low-cost thermal energy storage material

Abstract

The intermittent nature of solar energy is a drawback to its wide use in the absence of solar radiation. Therefore, there is the need for some forms of thermal storage. The objective of this study is to develop a hybrid mixture of a thermal storage material, which can be employed in medium-temperature-concentrated solar power plants. A concrete-graphite mixture sensible thermal storage material for applications up to 400°C for use with solar collectors was evaluated. Comparisons were made to determine the charging and discharging characteristics, thermal storage capabilities as well as costs between concrete only and a mixture of concrete and graphite. A mixture of expanded graphite and concrete was prepared and tested. The hybrid material exhibited fast charging and slow discharging for the same volumeof thermal storage. The hybrid material showed an improved thermal storage capacity in a ratio of 1.625:1 to concrete and thus reduces the space requirements. Also, results from the study revealed that when the costs of space requirements and the costs of using a hybrid material are compared, the hybrid material is expensive and only desirable in cases where there are space limitations.

Keywords

• cost analysis
• evaluation
• hybrid mixture
• solar energy
• thermal storage