DEVELOPMENT OF AN EFFICIENT LATENT HEAT THERMAL ENERGY STORAGE FOR SOLAR THERMAL POWER PLANT

Abstract

The continuous increase in the level of greenhouse gas emissions and the climb in fuel prices are the main driving forces behind efforts to more effectively utilize various sources of renewable energy. In many parts of the world, direct solar radiation is considered to be one of the most prospective sources of energy. However, the large-scale utilization of this form of energy is possible only if the effective technology for its storage can be developed with acceptable capital and running costs. One of prospective techniques of storing solar energy is the application of phase change materials (PCMs). Using PCMs based thermal energy storage (TES) reduces the gap between the period of thermal availability and its period of usage. Using PCMs it has been found that more solar energy now can be stored using the same device and efficiency and reliability is also improved. In the present study, a shell and multiple tubes type thermal energy storage has been designed and fabricated using phase change material paraffin wax. The melting temperature and the solidification temperature range are found as 53oC and 34oC respectively. The results have been obtained by using differential scanning calorimetry (DSC) analysis. The mass flow rate and inlet temperature of the heat transfer fluid (HTF) were selected as operating parameters. The temperature distribution in both axial and radial directions is determined during heat charging and discharging process of PCM. The temperature profile shows that the considered operating parameters are found to have more effect on melting time than solidification time due to increased natural convection during melting process. The melting time of PCM is found to decrease as a result of increasing the inlet temperature and the mass flow rate of heat transfer fluid. Amount of heat energy stored during charging process and released during discharging of PCM are computed based on the data collected experimentally. Further efficiency of the system is determined for the process. Finally, it is concluded from the results obtained that the technical grade paraffin wax which is less costly, encapsulated between multiple tubes and the shell has better heat transfer rate. It is therefore, the performance of the developed storage is improved.