Modeling and Characteristic Analysis of a Solar Parabolic Trough System: Thermal Oil as the Heat Transfer Fluid

The thermal oil is applied as the heat transfer fluid in a solar parabolic trough collector system. Firstly, the system dynamic model was established and validated by the real operating data in typical summer and spring days in references. Secondly, the alteration characteristics of different solar radiation, inlet water temperature and flow rate, and collectors’ area and length are analyzed and compared with the normal working condition. The model can be used for studying, system designing, and better understanding of the performance of parabolic trough systems. 1. Introduction Parabolic trough solar collector is a kind of line-focus concentrating solar utilizations for industry, with medium temperature, maximum working temperature 400–500°C. According to the heat transfer fluid types in the absorber, thermal oil and water/steam are the basic sorts. Both the two systems are wildly used in generating or heating in modern industry in recent years. The solar energy generating system with thermal oil as the heat transfer fluid, called SEGS, has been developed in several countries, especially in the USA. Therefore, the generated green electricity has increased the impetus of future research and development. Some of the published papers have studied the modeling and analysis of the heat transfer process of the thermal oil in parabolic trough collector systems. The one-dimension parabolic trough collector model had been developed by Odeh et al. [5], including synthetic oil and water/steam as the working fluid. The created model can be used to predict the performance of the collector. Rolim et al. [6] introduced an analytic model for a solar thermal electric generating system with parabolic trough collectors. The energy conversion of solar radiation into thermal power along the absorber tube of the parabolic collector is studied, taking into account the nonlinearity of heat losses and its dependence on the local temperature. The simulated results have been compared with experimental data. García-Valladares and Velázquez [7] developed detailed numerical simulations of thermal and fluid-dynamic behaviors of a single-pass and double-pass solar parabolic trough collector. The single-pass solar device numerical model has been carefully validated by experimental data. The parabolic trough collector and the main generating systems of the SEGS VI solar thermal oil power plant in California have been modeled by Stuetzle et al. [1, 2]; the control algorithms were established in MATLAB to control outlet temperature and flow rate. The one-dimension and two-dimension