Abstract

One of the major challenges with the use of solar thermal energy is the intermittent nature. As such, present day research is geared towards energy storage systems in which thermal energy is stored during the day for later use. However, in many engineering applications there is a continuous steady demand for energy. Experiments were conducted using concrete mix of 1: 1.2: 1.1 of cement, sharp-sand and limestone, respectively, plus 20g of 5cm length steel fibers which has a thermal conductivity of 2.46 W/mK and storage capacity of 3.24 x 106 J/m3 K. A laboratory packed bed prototype was built and test conducted for simultaneous charging, storage and discharging for an intermittent energy input. From the experimental results, the energy transfer of the packed bed system was analyzed and it was discovered that energy stored, charged and discharged increases with airflow rates. Spherical shaped concrete of diameter 0.11m exhibited the highest thermal energy storage efficiency of 60.5% at airflow rate of 0.013 m3/s.