However, the construction of this mirror was expensive because the more accurate the curved geometry is, the higher is its production cost. The parabolic trough can be considered the main part of the system, in which a curved glass mirror was widely used due to its high efficiency. For these two components (absorber tube and reflective surface) to function properly, it is necessary to implement auxiliary systems such as a system to control the flow, temperature, and operating conditions of the PTSC a tracking system, responsible for the parabolic trough movement and solar tracking and finally, a circulation and storage system for the heat transport fluid. As previously mentioned, the solar rays concentrated on the curved surface are directed to the absorber tube, which basically consists of a metallic tube with an absorber surface that receives solar radiation and conducts the absorbed heat to a heat transport fluid. However, low-cost alternatives seeking to improve the constructive process of this component are constantly proposed. In constructive terms, this component is considered expensive and complex. This surface must have mechanical strength and good quality optical properties for its application. PTSCs have a reflective film adhered to the surface of their parabolic trough, which is manufactured in curved glass mirrors. Representation of a PTSC: (i) absorber tube, (ii) solar rays, (iii) parabolic trough, (iv) fluid outlet temperature, and (v) fluid inlet temperature. It was concluded that the proposed solar collector obtained lower efficiency when compared with other collectors in the literature, which was assumed to be due to the diffusion losses of the parabolic trough reflector and thermal losses by convection in the parabolic trough absorber tube (optical efficiency, removal factor, and heat loss coefficient). Yet, the efficiency in function of the flow became optimal when the flow regime became turbulent. Thus, the proposed collector obtained an efficiency as a function of the temperature represented by the expression η = 0.324–2.47443 c′, where c′ is a parameter that relates the inlet temperature to the ambient temperature as a function of the solar radiation available. The second one evaluated the collector efficiency for different flows, subjecting the collector to flows from 0.002 to 0.030 kg/s. Thus, the inlet temperature varied, between 30 and 70☌, presenting a flow of 0.020 kg/s. The first test condition analyzed the efficiency of the collector at different temperatures. Laboratory tests were performed with deionized water as a transport fluid, establishing two testing conditions. The monitoring system was developed through an interactive panel to visualize the operating parameters of the sensing elements, thermocouples that measure the inlet and outlet temperature in the absorber tube, and the flow sensor to measure the flow of the heat transport fluid. The solar tracking system is one of the active types with two axes containing photoresistive sensors, which are used to determine the solar position and electric actuators to correct the positioning of the gutter. The gutter structure is composed of wooden sheets cut in a parabolic shape, where a 1.2 mm-thick galvanized steel sheet coated with a reflective film is supported, thus functioning as the reflective surface of the PTSC. The PTSC was built with an edge angle of 120°, an opening area of 2.2 m 2, and a copper absorber tube of 42 mm in outer diameter without a glass envelope. Thus, the present work describes the development of a low-cost PTSC for academic and research purposes. However, more research and development (R&D) has been done to improve its performance, using new materials, absorber tube geometries, solar tracking systems, and work (thermal oils, nanofluids). One of the most mature and internationally known technologies is the parabolic trough solar collector (PTSC), which has several applications, such as electricity generation, desalination, steam generation, and refrigeration systems, among others. Several technologies of solar concentrating systems, known internationally as CSP (concentrated solar power), are found in the industrial and scientific environment. It is also of great interest as an option for energy generation and CO 2 emissions reduction. ![]() Solar energy found abundantly in nature is considered a renewable energy source.
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