Impact of heliostat curvature on optical performance of Linear Fresnel solar concentrators

Benyakhlef, Sara; Mers, Ahmed Al; Merroun, Ossama; Bouatem, Abdelfattah; Boutammachte, Noureddine; Alj, Soukaina El; Ajdad, Hamid; Erregueragui, Zineb; Zemmouri, El Moukhtar

doi:10.1016/j.renene.2015.12.018

Cited by 43 publications

(11 citation statements)

References 23 publications

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“…18 It has been found that curvature impact on LFR efficiency is inversely proportional to receiver height and that deflection coefficient varying between 1 and 2 mm is sufficient enough to achieve high concentration ratio. 18 It has been found that curvature impact on LFR efficiency is inversely proportional to receiver height and that deflection coefficient varying between 1 and 2 mm is sufficient enough to achieve high concentration ratio.…”

Section: Discussionmentioning

confidence: 99%

“…Benyakhlef et al have numerically investigated the impact of mirror curvature on optical performances of an LFC through the use of a Monte Carlo-ray tracing simulation tool. 18 It has been found that curvature impact on LFR efficiency is inversely proportional to receiver height and that deflection coefficient varying between 1 and 2 mm is sufficient enough to achieve high concentration ratio. Mokhtar et al developed a mathematical model for the estimation of the thermal efficiency of a small-scale LFC, assuming that the optical efficiencies of the collector are a function of declination angle and sun altitude.…”

Section: Discussionmentioning

confidence: 99%

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Optical performance and instantaneous efficiency calculation of linear Fresnel solar collectors

2017

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Summary The main objective of this study is the investigation of the effect of the optical path of incident beam solar radiation on the performance of a linear Fresnel concentrating solar collector. The requirements regarding the kinematics of the reflectors are examined, allowing the effective focus of the reflected radiation on the receiver cover. A methodology for the calculation of the reflection angles of the sun rays incident on the mirrors, as well as of the incidence angles of the reflected rays on the cover, as a function of the sun position and the geometry of the collector is proposed. Specific scenarios, describing the effect of the solar radiation optical path on the collected heat, are formulated, each of them leading to a different form for the instantaneous efficiency equation. The evaluation and analysis of these scenarios, on the basis of actual operation conditions, has shown that the effect of the reflection and incidence angles throughout the modeling of the collector and the calculation of the useful thermal power cannot be neglected.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Optical performance and instantaneous efficiency calculation of linear Fresnel solar collectors

2017

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“…The annual energy losses due to cosine effect from the East-West-oriented LFR field is about 30 % higher than that of North-South-oriented field for Murcia (38.2°N, 1.6°W), Spain (Sharma et al 2015b). Benyakhlef et al (2016) investigated the impact of curved mirrors for LFR field using a Monte Carlo-ray tracing simulation tool and concluded that the curved mirrors lead to better optical performance and flux density onto the receiver than the flat mirrors. It was also reported that the curvature impact on the LFR efficiency is inversely proportional to the receiver height, and therefore, in case of the higher receiver height, the optical efficiency is less affected by the mirror curvature.…”

Section: Linear Fresnel Reflectormentioning

confidence: 99%

“…In case of flat mirrors, changing the receiver height from 2 to 6 m increases the optical efficiency of the system up to 10 %. Moreover, deflections in the mirrors of about 3 mm allow decrease in the size of the receiver (Benyakhlef et al 2016). If the mirror curvatures are designed with the sun as specific reference, an increase in the power output of about 1.2 %, compared to the same solar collector aperture area with flat mirrors, can be achieved .…”

Section: Linear Fresnel Reflectormentioning

confidence: 99%

Line-focusing concentrating solar collector-based power plants: a review

Desai

Bandyopadhyay

2016

Clean Techn Environ Policy

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Concentrated solar power (CSP) plant is an emerging technology among different renewable energy sources. Parabolic trough collector (PTC)-based CSP plant, using synthetic or organic oil as a heat-transfer fluid, is the most advanced technology. About 87 % of the operational capacities of CSP plants worldwide are based on PTC technology. Direct steam-generating linear Fresnel reflector (LFR) systems have been developed as a cost-effective alternative to PTC systems. Line-focusing concentrating solar collectors (PTC and LFR), with single-axis tracking, are simple in design and easy to operate. Prior to the detailed design of a CSP plant, it is necessary to finalize type of the solar field, type of the power-generating cycle, overall plant configuration, sizing of the solar field and the power block, etc. The optimal design of a CSP plant minimizes the levelized cost of energy for a given site. In this paper, a detailed review of important design parameters which affect the design of line-focusing concentrating solar collector-based power plants is presented. This includes parameters for solar collector field design, receiver, heat-transfer fluid, thermal energy storage, powergenerating cycle, sizing and configuration of the plant, etc. This review may provide a reference for designing CSP plants. Future research directions are also identified.

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“…Balaji et al (2016) employed the combination of multi-stage focusing and multiple reflectors to increase the concentration ratio and also to improve the flux distribution over the circumference of the absorber [18]. Benyakhlef et al (2016) used multiple rotating curved heliostats instead of flat ones to reflect the sun-rays onto the linear receiver at a fixed position. Primary focusing heliostats were arranged in rows whereas the secondary reflector was only one reflector.…”

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confidence: 99%

Solar Concentrator Consisting of Multiple Aspheric Reflectors

Cao¹,

Qin

Rajan

et al. 2019

Energies

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This paper presents an off-axis-focused solar concentrator system consisting of 190 aspheric reflectors, where the aperture radius of each reflector is 10 cm, and vertices of all reflectors are orderly arranged in the same plane. The aspheric parameters controlling the curvature of the reflectors are determined using coordinate transformations and the particle swarm optimization (PSO) algorithm. Based on these aspheric parameters, the light distribution of focal plane was calculated by the ray tracing method. The analyses show that the designed concentrator system has a spot radius of less than 1 cm and the concentration ratio over 3300:1 is achieved using only one reflection. The design results have been verified with the optical design software Zemax.Most of the important developments of solar concentrators have been done in the solar thermal and PV systems. In the solar thermal system, the most common method is to increase focusing stages and reflectors. Rodriguez-Sanchez et al. (2015) employed secondary devices to optimize the focusing position and the incidence angle of sunlight [17]. Balaji et al. (2016) employed the combination of multi-stage focusing and multiple reflectors to increase the concentration ratio and also to improve the flux distribution over the circumference of the absorber [18]. Benyakhlef et al. (2016) used multiple rotating curved heliostats instead of flat ones to reflect the sun-rays onto the linear receiver at a fixed position. Primary focusing heliostats were arranged in rows whereas the secondary reflector was only one reflector. Interestingly, the curvature allowed the heliostats to be more precise than in flat ones and offered a higher concentration capacity [19]. Sharma et al. (2015) utilized the line Fresnel reflector (LFR) field consisting of parallel rows of collectors in which each collector-row was composed of parallel rows of reflectors that direct the sun-rays toward linear receivers [20]. Qin et al. (2013) raised the concentration ratio of a trough concentrator to 285:1 in case of off-axis focus by adopting reflective aspheric surfaces [14]. Recently, a prototype of two-stage non-imaging solar concentrator showed a higher concentration ratio at the receiver plane [21]. However, improving the spatial uniformity can efficiently increase the concentration ratio. A new concept of high-flux non-coaxial concentrating solar simulator was introduced to the typical ellipsoidal reflectors [22]. In some cases, multiple reflectors were used to focus the solar beam on the same small area in order to increase the temperature of the focus area [23][24][25][26]. Loni et al. (2016) used parabolic dish concentrators to focus the sun-rays on the receiver for obtaining a high temperature of work fluid. Furthermore, they designed a cylindrical closed-tube open-cavity solar receiver in such a way to absorb the solar energy to the maximum extent [27]. Other methods have also been applied to achieve high concentration ratio. Liang et al. (2015) investigated solar concentrator based on the off-ax...

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Impact of heliostat curvature on optical performance of Linear Fresnel solar concentrators

Cited by 43 publications

References 23 publications

Optical performance and instantaneous efficiency calculation of linear Fresnel solar collectors

Optical performance and instantaneous efficiency calculation of linear Fresnel solar collectors

Line-focusing concentrating solar collector-based power plants: a review

Solar Concentrator Consisting of Multiple Aspheric Reflectors

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