Design and Thermal Analysis of Nanofluid-Based Compound Parabolic Concentrator

Given the enormous demand for intermediate temperature applications such as heating, cooling, desalination and process industry; it is imperative to develop efficient low-cost solar thermal systems. Although, non-concentrating collectors are ubiquitous, these are limited by the maximum achievable temperatures. To enhance the existing efficiencies and temperatures without the requirements for diurnal tracking of the sun; volumetric absorption-based receivers employing non-imaging concentrators hold promise. In the present work, we are proposing a nanofluid based volumetrically absorbing receiver housed in a novel compound parabolic concentrator (NCPC). Herein, we synergize the benefits of volumetric absorption and non-imaging concentrators for enhancing the output temperatures without increasing the collector area. Detailed analysis reveals that 6.5 °C higher temperature rise has been achieved with CPC as compared to non-concentrating collector under similar operating conditions and for a given collector surface area. Furthermore, it has been found that the performance of the nanofluid based CPC depends mainly on the volume fraction of nanoparticles and mass flow rate. Finally, the benefit of using two glass tubes receiver with vacuum over the single glass tube receiver has also been quantified; 18 °C higher temperature could be achieved with the two-glass tube receiver design.