Nanotechnology Applications for Solar Energy Systems

6 Thermal Management and Performance Enhancement of Parabolic Trough Concentrators Using Nanofluids

Muhammed A. Hassan

Mechanical Power Engineering Department, Faculty of Engineering, Cairo University, Giza 12613, Giza, EgyptUniversite de Pau et des Pays de l’Adour, E2S UPPA, LaTEP, Pau, France

6.1 Introduction

Among the different existing technologies for concentrating direct solar irradiance, parabolic trough concentrators (PTCs) are the fully developed and commonly installed ones. In these concentrators, mirrors, shaped as parabolas, are used to direct the incident rays from the sun towards a receiver located at the mirrors’ focal line. The concentration effect is achieved due to the high ratio between the mirror’s aperture area and the receiver’s projected area. Concentration ratios up to ~82 are obtainable via standard designs, which leads to operating fluid temperatures up to ~400°C. With such elevated temperatures, the absorber is encapsulated in an evacuated cylindrical glass shell to diminish convective thermal losses (Figure 6.1). Special coatings are applied to the surfaces of the mirrors, glass shell, and absorber tube to enhance their reflectivity, transmissivity, and absorptivity, respectively, for maximum energy utilization rates. The heat transfer fluid (HTF) is circulated inside the absorber tube to remove the concentrated heat for use in a wide range of medium-to-high temperature applications such as district heating and cooling, desalination, industrial process ...