Investigation of thermal performance of a parabolic trough solar collector using different heat transfer fluids

Abstract

ABSTRACT Parabolic trough solar collectors (PTSCs) are the most versatile and reliable solar collectors that could achieve higher temperatures, making them employed over diversified areas like industrial and domestic applications. Understanding the working principle of PTSC as well as enhancing their performance and efficiency for better reliability is highly relevant at present, as we are in dire need of a shift toward reliable renewable sources of energy. A non-tracking, feasible, and locally scalable simple PTSC with moderate performance and temperature output has been used in this experiment. The receiver is a significant part of the collector system, carrying the heat transfer fluid (HTF), and determines the performance and output of the PTSC to a great extent. In this study, two receiver configurations, one being an evacuated tube and another a simple copper tube with a glass cover, are employed, and a comparative analysis is performed. Two different blends of water and thermal oils as HTF are also employed, and their influence on the performance of the PTSC under both receiver configurations is evaluated. Initially, water is used as the HTF, and gradually, 0.5% of Hytherm 600 thermal oil is blended in every hour, and the results are monitored. Similarly, Therminol 55 is also blended with water at a similar rate as the HTF and output readings are observed. The experimental results confirmed that the evacuated tube configuration yielded the best overall system efficiency of 55.4% in the case of both HTFs. Comparing the performance of different oil and water blend as HTF, Hytherm 600 exhibits better performance than Therminol 55, up to 32% higher efficiency in evacuated tube configuration. The best efficiency of the system was exhibited during the noon when the solar incidence angle was close to zero and the optical efficiency reached up to 71.6%.