###### Abstract
The receiver is one of the most critical components of a parabolic trough concentrator. When optimizing a parabolic trough solar collector, one of the essential parameters of the receiver is the concentration ratio (CR), defined as the ratio of the area of the light collection region to the location of the light absorption region [16], and also, the concentration ratio is inversely related to the efficiency loss caused by thermal losses [17]. The relatively high concentration ratio design allows the parabolic trough system to operate at a higher temperature. Since the heat loss per unit area of the receiver is large, and the tube receiver has a large heat dissipation area and a low concentration ratio, the efficiency loss caused by heat loss is large. Compared with traditional receivers, cavity receivers have lower heat loss and higher efficiency and can operate at higher temperatures, improving the efficiency of the thermoelectric system and the overall system efficiency [18; 19]. The main methods for analyzing and optimizing trough solar collectors include the cone optics method [20; 21; 22], the ray-tracing method [23; 24] and the semi-infinite method [25]. The cone optics method treats the sunlight beam as a cone with the incident point as the vertex, and to calculate the energy absorbed at each point on the receiver, the entire surface of the reflector must be integrated. The semi-infinite method has accurate physical characteristics, but due to its complex formulas, it still requires a large amount of computation. The ray-tracing method is a widely used microscopic approach that is easy to code, but because it involves the calculation of a large number of rays, it brings a significant computational burden. This method simulates the process of sunlight being incident on the solar collector and then reflected onto the receiver, with each ray representing a portion of the energy incident on the receiver [23; 26]. [PERSON] proposed a reverse ray-tracing method to calculate the performance of parabolic trough systems [23], which was later improved by several researchers. [PERSON] developed a three-dimensional model based on a recursive ray-tracing algorithm [26]. [PERSON] and others proposed a parabolic trough hybrid photovoltaic/thermal system and used the ray-tracing method to establish a three-dimensional optical model for the system [24]. [PERSON] and others considered the impact of ray escape on parabolic trough systems, studying the system using the Monte Carlo ray-tracing method and theoretical analysis [27]. [PERSON] [28] proposed a detailed calculation method based on ray tracing, called Ray Tracing 3 Dimensions-4 Rays (RT3D-4R) and studied the total intercepted solar energy and daily solar gain for parabolic trough solar collector systems under different concentration ratios and rim angles, using different tracking systems. One of the main drawbacks of the traditional ray-tracing method is the large computational demand, making it difficult to use for performance optimization analysis. This paper proposes a new spliced cylindrical mirror trough solar thermal collection system, which is similar to the conventional trough solar system but uses multiple cylindrical mirrors to form a reflector to simulate a parabolic reflector, which is similar to the successful use of a sphere mirror in a parabolic dish. This paper also proposes a new line-focusing ray-tracing method that can be used to calculate the performance of various line-focusing solar systems. We use this model to analyze the performance of a cylindrical spliced solar system, including the performance under different error conditions, and propose an optimized design. We also combine the trough reflector and the cylindrical mirror-spliced reflector with the cavity receiver and the tube receiver, respectively, and calculate and compare the performance of these types of trough systems.