Design of a small size PTC: computational model for the receiver tube and validation with heat loss test

Salvestroni, Michele; Pierucci, Giacomo; Fagioli, Federico; Pourreza, Atabak; Messeri, Matteo; Taddei, Francesco; Hosouli, Sahand; Rashidi, Hamid; Lucia, Maurizio De

doi:10.1088/1757-899x/556/1/012025

Cited by 4 publications

(4 citation statements)

References 8 publications

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“…A new prototype of micro-PTC was optically designed, realized, and tested [30][31][32][33]. The micro-PTC was successively utilized for the realization of a concentrated solar power plant.…”

Section: Introductionmentioning

confidence: 99%

Laser Profilometry on Micro-PTC

et al. 2022

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Profilometry is useful in detecting surface faults on solar concentrators, which can be imperfectly manufactured, thus affecting system performance. Profilometric analyses are performed on a micro-parabolic trough collector (m-PTC), with reduced sizes and greater mirror curvature than a usual PTC. The peculiar dimensions and shape of this micro-PTC request to develop a specific configuration of laser profilometry. It includes a laser diode with a converging lens placed in front of it, ensuring that the mirror curvature does not affect the beam reflection. A new method to calculate the spot position furnishes the reflected beam center even if it lies outside the target, giving it a virtual expansion. The profile is assessed with an iterative calculation, starting from a first point, physically measured. The results are the 3D profile reconstruction of the parabolic mirror and a map of the slope error for each mirror point. It also estimates the intercept factor, a parameter fundamental to optimize the m-PTC system, whose value is in agreement with a structured light measurement on the same object. This intercept factor was obtained averaging the local intercept factor calculated for each mirror point, which individuates the mirror portions not focusing the sunrays on the tube.

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Section: Introductionmentioning

confidence: 99%

Laser Profilometry on Micro-PTC

et al. 2022

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“…In fact, considering a defect of the same size on the surface of a micro-PTC collector and on a conventional PTC mirror will result in a greater loss of energy on the smaller concentrator, because it affects a larger fraction of the total area of the receiver. In the current testing phase for this technology [14][15][16][17], a fundamental parameter to be experimentally determined and calculated is the optical efficiency of the system. It represents the upper limit that overall efficiency can be reached in the absence of thermal losses.…”

Section: Introductionmentioning

confidence: 99%

“…In the current testing phase for this technology [14][15][16][17], a fundamental parameter to be experimentally determined and calculated is the optical efficiency of the system. It represents the upper limit that overall efficiency can be reached in the absence of thermal losses.…”

Section: Introductionmentioning

confidence: 99%

Structured Light Profilometry on m-PTC

et al. 2020

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In concentrating solar systems, it is essential to study the optical losses of the collectors. A fundamental parameter is the intercept factor, namely, the fraction of sunrays reflected by the concentrator that reaches the receiver. Optical profilometry studies the relationship between the collector profile and the intercept factor, which influences the collection efficiency. Profilometric analyses were performed on a micro-parabolic trough collector (m-PTC), with reduced sizes and greater mirror curvature than a usual PTC. The proposed technique projects a luminous pattern (structured light) both on the collector with an opaque covering and on a flat reference plane. Measurement set-up and calibration technique were developed for m-PTC. A program coded in Python analyzed the images and reconstructs the mirror profile. The tilted reference plane was reconstructed using an original geometric model and a calibration procedure. The focal length of each parabolic section was calculated, providing information on surface defects in the mirror. An important parameter obtained was the displacement of the focus of the parabola with respect to the ideal position. Using this value, the intercept factor was estimated to be 0.89. The proposed technique was validated by comparing the results with an independent profilometric study applied to the same m-PTC.

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“…In the second one [23], the authors study the possibility of realizing a prototype of PTC that has the main features of highly reduced dimensions, compared to standard PTCs, and modularity. An optical analysis allowed for the selection of the optimal values of the parameters for the parabola, aperture and rim angle.…”

mentioning

confidence: 99%

Numerical Modeling and Experimental Validation of Heat Transfer Characteristics in Small PTCs with Nonevacuated Receivers

Ebolese,

Marano,

Copeta

et al. 2023

Solar

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The development of small-sized parabolic trough collectors (PTCs) for processing heat production at medium temperatures (100–250 °C) represents an interesting approach to increase the utilization of solar thermal technologies in industrial applications. Thus, the development of simplified models to analyze and predict their performance under different operative and climatic conditions is crucial for evaluating the application potential of this low-cost technology. In this paper, we present a numerical method that by combining three-dimensional finite element simulations (implemented with COMSOL Multiphysics software version 6.1) with a one-dimensional analysis (based on a MATLAB script) allows for the theoretical determination of the power output of a small-PTC with a nonevacuated tubular receiver operating at a medium temperature. The finite element model considers both the nonuniformity of the concentrated solar flux on the receiver tube (evaluated using Monte Carlo ray-tracing analysis) and the establishment of natural convection in the air gap between the glass envelope and absorber tube. The model calculates, for several values of direct normal irradiance (DNI) and inlet temperatures, the thermal power transferred to the heat transfer fluid (HTF) per unit length. The data are fitted using the multiple linear regression method, obtaining a function that is then used in a one-dimensional multi-nodal model to estimate the temperatures and the heat gains along the receiver tube. The outputs of the model are the outlet temperature and the total thermal power transferred to the HTF. In order to validate the developed methodology for the assessment of the heat transfer characteristics in the small-PTC with a nonevacuated receiver, an experiment at the ENEA Trisaia—Solar Thermal Collector Testing Laboratory was carried out. This work compares the theoretical data with those acquired through experimentation, obtaining a good agreement, with maximum differences of 0.2% and 3.6% for the outlet temperatures and the power outputs, respectively.

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Design of a small size PTC: computational model for the receiver tube and validation with heat loss test

Cited by 4 publications

References 8 publications

Laser Profilometry on Micro-PTC

Laser Profilometry on Micro-PTC

Structured Light Profilometry on m-PTC

Numerical Modeling and Experimental Validation of Heat Transfer Characteristics in Small PTCs with Nonevacuated Receivers

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