Fengwu Bai

Concentrating solar power (CSP) tower plants using molten salt as the heat transfer fluid are currently the predominant technology used globally, and have experienced rapid development in recent years. The molten salt receiver, as the core piece of equipment for converting solar energy into thermal energy, directly determines the system efficiency, while its safety affects the plant’s operating hours. This paper reviews the details and operational status of commercial-scale CSP tower plants worldwide as of the end of 2023. It systematically summarizes the typical thermal models for mainstream tubular molten salt receivers by reviewing 37 models, including 11 three-dimensional (3D) numerical models, 8 two-dimensional (2D) semi-empirical models, and 18 one-dimensional (1D) semi-empirical models. By comparing and analyzing the key features of each model, the study concludes that detailed 3D numerical models are effective for monitoring overheating during operation, 2D semi-empirical models enable the rapid evaluation of receiver configurations, and 1D semi-empirical models support transient mass flow calculations and annual power generation estimations. Additionally, the paper outlines the current applications of receiver thermal models in system integration, particularly in combining CSP tower systems with other energy systems.

Planar light concentrators are potential applications for solar thermal conversion, in which the intensity of the electric field will exhibit strongly non-uniform characteristics. However, previous research has long ignored the solar absorption performance of plasmonic nanoparticles in the focused electric field. In this work, we use the finite element method (FEM) to study the optical behaviors of a single nanoparticle and multiple nanoparticles in the focused electric field formed by vertically and inwardly imposing the initial incident light on a quarter cylindrical surface. The results show that the focused electric field can significantly improve the solar absorption abilities compared with the parallel one for all the nanoparticles due to the local near-electric field enhancement caused by the aggregation of the free electrons on the smaller zone. Further studies on the focused electric field reveal that the plasmon heating behavior of Au spheres presents a rising trend with the decrease in inter-particle spacing, as the gap is less than the radius of Au spheres. As the number of nanoparticles increases along the focal line, the absorption power of the center nanoparticles gradually tends to be stable, and it is much lower than that of a single nanoparticle. As the nanoparticles are arranged along the y and z directions, the heterogeneity of the electric field makes the optical properties uneven. Notably, the strongest electric field appears slightly close to the incident surface rather than on the focal line.

Solid particles are generally considered to be the most suitable heat transfer fluid (HTF) and thermal energy storage (TES) materials for the next‐generation concentrated solar power (CSP) plant. The operating temperature of the solar receiver can be raised to exceed 800°C by the application of appropriate solid particles. In this way, power conversion efficiencies greater than 50% can be achieved with the supercritical carbon dioxide (sCO₂) Brayton cycle. Solid particle solar receiver (SPSR) is the key equipment to absorb the concentrated solar flux, and its thermal performance is remarkably affected by receiver system designs, particle flow characteristics, and properties of solid particulate materials. This paper provides an in‐depth review of various SPSR technologies, as well as pertinent solid particle selections, optimization of the receiver system structures, particle flow characteristics, and heat transfer characteristics. The technical drawbacks, the large‐scale development prospects, and the potential optimization strategies of the various SPSR designs are highlighted by the comparative analysis of multiple parameters. image

A high-flux solar simulator is essential for evaluating solar thermal components under controlled and adjustable flux input conditions. This study presents a newly built high-flux solar simulator composed of 19 individual units. Each unit includes a xenon short-arc lamp (each consuming up to 6 kW electricity power) coupled with a truncated ellipsoidal reflector, a cooling blower, and a power module. The power module yields a current in the range of 50∼160 Ampere. The number of lamps in use is flexible, which allows for a wide range of radiation flux (10%∼100%) on the focal plane. The radiation power, peak value, flux distribution on the circular target plane, and conversion efficiency are evaluated based on a flux mapping method. The results indicate that the proposed solar simulator is capable of achieving thermal power of 23.3 kW, peak flux in excess of 1.78 MW/m², a stagnation temperature exceeding 2360 °C, and average irradiance of 773.4 kW/m² on the focal plane (diameter of 260 mm). The electro-thermal conversion efficiency of the simulator is 35.7%. A ray-tracing method was employed, and the simulation results were found to be in good agreement with those in the experiments. An experimental test of a volumetric ceramic receiver was conducted, and the results indicate the availability and applicability of the high-flux solar simulator when carrying out studies about solar receivers.

In this paper, an optical structure design for a solar furnace is described. Based on this configuration, Monte Carlo ray tracing simulations are carried out to analyze the influences of four optical factors on the concentrated solar heat flux distribution. According to the practical mirror shape adjustment approach, the curved surface of concentrator facet is obtained by using the finite element method. Due to the faceted reflector structure, the gaps between the adjacent mirror arrays and the orientations of facets are also considered in the simulation model. It gives the allowable error ranges or restrictions corresponding to the optical factors which individually effect the system in Beijing: The tilt error of heliostat should be less than 4 mrad; the tilt error of the concentrator in the orthogonal directions should be both less than 2 mrad; the concentrator facets with the shape most approaching paraboloid would greatly resolve slope error and layout errors arising in the concentrator. Besides, by comparing the experimentally measured irradiance with the simulated results, the optical performance of the facility is evaluated to investigate their comprehensive influence. The results are useful to help constructors have a better understanding of the solar furnace’s optical behavior under conditions of multiple manufacture restrictions.