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Imaging concentrators like the parabolic trough solar concentrators have been widely employed for energy production in solar power plants. The conventional imaging solar concentrators form a non-uniform Gaussian distribution on receiving absorbers yielding the highest temperatures. The traditional CSP system normally truncated a peripheral region of heat flux to better use the central part. CPV/T systems using the waste heat recovery method can largely improve the total efficiency. However, for the CPV module, the coolant temperature was usually below 80 °C, which limited the applications of the thermal cycle such as the ORC system. In this article, a novel trough-type free-form secondary solar concentrator (TFSC) for PV/Thermal hybrid application has been proposed. Different from other CPV/T concepts using a combined PV panel and cooling tunnel/tube, the current concept separates the receiver in two parts. The secondary free-form reflector is generated by the geometric construction method, resulting in uniform heat flux in the edge region and high concentration in the central region. Through the ray tracing method, the optical properties have been verified. Sensitivity analysis of the concentrating structure is also conducted. The results provide supports for the design and applications of novel CPV/T systems. [ABSTRACT FROM AUTHOR]

A vector based freeform approach is proposed for the geometrical reverse design of reflecting solar concentrators. The effect of solar cone angle of incident vectors is taken into consideration in the method based on three-dimensional freeform optics. The method developed is a closed-loop program and did not need any other commercial software. According to the transmission pattern of solar concentrators, the source-target mapping should be initially established prior to constructing an initial geometry formed by discrete points using the Geometric Construction Method. The freeform surface is generated by connecting several triangular flat elements defined by these points and then the Monte-Carlo ray tracing was conducted. The freeform surface can then be further optimized through feedback modifications. Finally, the optimal shape is obtained when the design examples are the off-axis freeform reflectors with target circular/rectangular receivers for the use of Concentrated Photovoltaic. This method provides a practical approach for improving the optical performance of solar concentrators. [ABSTRACT FROM AUTHOR]

The optical transmitting characteristics of curved quartz window fitted with a Volumetric Solar Receiver (VSR) are studied. The VSR adopts a cup-shaped alumina ceramics as the receiver for modeling and testing. The transmission model of window assembled with VSR is established considering multiple reflections, refraction, and absorptions. The flux distribution on the receiving surface is simulated by Monte-Carlo ray tracing method (MCRTM). When the relative positions of the focal point, glass window and porous are changed, not only the 2-D flux distribution, but also the total energy of input and central porous are compared. The experimental system for the high-temperature VSR is established based on the sixteen dish concentrator (SDC). Through experimental studies, the highest temperatures of central porous and the time spent at different parameters are tested, instead of testing the optical flux distribution inside VSR which is hardly to be obtained. The results can provide important reference and practical value for the design and construction of high-temperature VSR in future. [ABSTRACT FROM AUTHOR]

In this article, a newly designed volumetric solar receiver (VSR) using cup-shaped Al 2 O 3 porous absorber is studied through numerical simulations and experimental verification. The absorber achieves several advantages including lower heat loss and higher uniformity of heat flux. The ray tracing method is adopted to obtain the external radiation source. The inner radiative exchange within the cavity is solved with the aid of User Defined Function (UDF). The heat transfer performance has been compared based on different parameters including window reflectivity, porosity and mass flow rate. The theoretical advantages of using cup-shaped Al 2 O 3 absorber are presented. The experimental verification is adopted based on sixteen-dish concentrator (SDC) platform. [ABSTRACT FROM AUTHOR]

With the increase of combustion temperatures, the thermal radiation effect for hot components in the new generation of aero-engines has become a key factor in the combustion process, cooling structure design, and thermal protection. A radiation loading system can be used as an external heat source to simulate the real thermal environment of hot components in aero-engines. Total receiving power, as well as 3-D heat flux distribution, should better coincide with real conditions. With the aid of freeform optics and the feedback optimization method, the current study develops a concentrating-type radiation heating system fit for the leading-edge surface of a C3X turbine vane. A xenon lamp combined with a freeform reflector was optimized for controllable heat flux. A design method in the area of illumination engineering was innovatively extended for the current model. Considering the effect of polar angular radiative flux distribution of a xenon lamp, a Monte Carlo ray tracing (MCRT) method was adopted to evaluate the optical performance. Feedback modifications based on Bayesian theory were adopted to obtain the optimal shape of the FFS for target heat flux. The current study seeks a feasible way to generate 3-D heat flux distribution for complex curved surfaces, such as turbine vane surfaces, and helps to simulate the real thermal environment of hot components in aero-engines. [ABSTRACT FROM AUTHOR]