Design and Optical Performance of Compound Parabolic Solar Concentrators with Evacuated Tube as Receivers

Compound parabolic concentrating (CPC) collectors have great potential to provide sustainable solar thermal energy for many applications operating in the medium temperature range. This paper presents the design, development and performance evaluation of a modified CPC collector integrated with an evacuated tube receiver. The optical performance of the designed CPC paired with concentric tube receiver is compared with that of a CPC coupled with single flow through evacuated tube receiver for stationary installation in the East-West and North-South directions. Ray tracing simulations of different configurations demonstrate that CPC coupled with single flow through receivers suffer high gap losses, especially at smaller incidence angles which are considerably alleviated by a concentric tube receiver arrangement. East-West installation of CPC paired with concentric tube receiver exhibited superior optical performance than all other configurations. The yearly average optical efficiency of CPC with concentric tube receiver was 5% higher than that of a single flow through receiver within the acceptance angle. A 60% truncated CPC coupled with concentric tube receiver emerged as the most effective design, which was fabricated for experimental testing. The tests conducted under actual outdoor tropical environmental conditions demonstrated that the experimental optical efficiency reached to about 69% in the case of N-S installation and 66.5% in an E-W arrangement. The experimental results closely match the simulation outcomes, which indicate the proposed performance prediction technique as instrumental for selecting the most effective configuration of CPC collectors for medium temperature heat supply.

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“…where 1 − L = gap efficiency and L is the average value of gap loss factor which is determined by following equation [31]:…”

Section: Energy Modelingmentioning

confidence: 99%

Optical Performance Analysis of Single Flow Through and Concentric Tube Receiver Coupled with a Modified CPC Collector Under Different Configurations

et al. 2019

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“…The heat loss of forced convection (wind) through the cavity aperture can be correlated as [37]: (11) where H ap is characteristic length of receiver aperture, λ a is the heat conductivity of air, and Nu f c is the Nusselt number of forced convection thought the cavity aperture, and Equation (11) can be used as wind velocity, where u < 20 m/s [37]. In Equations (8) and (11), the characteristic temperature is (T w + T s )/2. The absorbed energy Q ab transferred by the fluid inside absorber tube is mainly determined by the absorbed heat flux q ab f in the front side of absorber tube and the heat loss flux q lob in the back side of absorber tube, as illustrated in Figure 1.…”

Section: Nonuniform Heat Transfer Model Of Cavity Receivermentioning

confidence: 99%

“…Wang et al [11] considered the optical loss of the receiver with a parabolic solar concentrator. Msaddak et al [12] analyzed combined natural convection and radiation heat losses in an open rectangular solar cavity receiver by the Lattice Boltzmann method.…”

Section: Introductionmentioning

confidence: 99%

Nonuniform Heat Transfer Model and Performance of Molten Salt Cavity Receiver

Wang

Ding

2020

Energies

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The temperature distribution and thermal efficiency of a molten salt cavity receiver are investigated by a nonuniform heat transfer model based on thermal resistance analysis. For the cavity receiver MSEE in Sandia National Laboratories, thermal efficiency in this experiment is about 87.5%, and the calculation value of 86.93–87.79% by a present nonuniform model fits very well with the experimental result. Different from the uniform heat transfer model, the receiver surface temperature in the nonuniform heat transfer model is remarkably higher than the backwall temperature. The incident radiation flux plays a primary role in thermal performance of cavity receiver, and thermal efficiency approaches to maximum under optimal incident radiation flux. In order to increase thermal efficiency, various methods are proposed and studied, including heat convection enhancement by an increase of flow velocity or the decrease of the tube diameter and number of tubes in the panel, and heat loss decline by a decrease of view factor, surface emissivity and insulation conductivity. According to calculation results by different modes of the nonuniform heat transfer model, the thermal efficiency of the cavity receiver is reduced by nonuniform heat transfer caused by variable fluid temperature or variable circumferential temperature, so thermal efficiency calculated by variable fluid temperature and variable circumferential temperature is lower than that calculated by average fluid temperature and bilateral uniform circumferential temperature for 0.86%.

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“…This study also provides the formulae for calculating average reflections within a CPC. For an ideal CPC, only two parameters are required, acceptance angle and receiver diameter; in this way, there is only one parameter to define, the acceptance angle which defines the concentrator´s width and height [4], because a CPC usually requires few or no adjustments to its angular position, for example, seasonal position for few adjustments [4][5][6][7][8]. A CPC system usually has construction imperfections that impact of 19 its efficiency, therefore, a common task is to minimize losses by taking into account the restrictions imposed by the design, material properties and cost considerations [5,9,10].…”

Section: Introductionmentioning

confidence: 99%

Solar Ray Tracing Analysis to Determine Energy Availability in a CPC Designed for Use as a Residential Water Heater

Terrón-Hernández¹,

Peña‐Cruz²,

Carrillo³

et al. 2017

Preprint

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Compound parabolic concentrators are relevant systems used in solar thermal technology. With adequate tailoring, they can be used as an efficient and low-cost alternative in residential water applications. This work presents a simulation study using a ray tracing methodology. With this technique we simulate the interaction between solar rays and solar concentrator to quantify the amount of energy that impinges on the receiver at a particular time. Energy availability is evaluated in a comparison of two configurations: stationary at 21° throughout the year and multi position setup; tilted with respect to the horizontal depending on three seasonal positions: 0° for summer, 16° for spring / autumn and 32° for winter, with the objective of increasing the amount of available energy in each season. The fact that a tracking system can be dispensed with also represents an economical option for the proposed application. The results showed that at 21°, the proposed system works satisfactorily; however, by carrying out the selected angular adjustments, the overall energy availability increased by 22%, resulting in a more efficient option. The methodology developed herein proved to be a valuable tool for prototype design and performance evaluation.

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Design and Optical Performance of Compound Parabolic Solar Concentrators with Evacuated Tube as Receivers

Cited by 19 publications

References 22 publications

Optical Performance Analysis of Single Flow Through and Concentric Tube Receiver Coupled with a Modified CPC Collector Under Different Configurations

Optical Performance Analysis of Single Flow Through and Concentric Tube Receiver Coupled with a Modified CPC Collector Under Different Configurations

Nonuniform Heat Transfer Model and Performance of Molten Salt Cavity Receiver

Solar Ray Tracing Analysis to Determine Energy Availability in a CPC Designed for Use as a Residential Water Heater

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