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Challenge and Research Trends of Solar Concentrators

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A2: Solar Energy and Photovoltaic Systems".

Deadline for manuscript submissions: closed (31 October 2022) | Viewed by 27126

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Dr. Dawei Liang

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Guest Editor

Department of Physics, NOVA University of Lisbon, 2829-516 Caparica, Portugal
Interests: solid-state lasers; solar power concentration; optics and lasers
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Changming Zhao

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Guest Editor

School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China
Interests: solar-pumped lasers; solar concentrators; solar furnace; optics
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

As the most abundant renew energy resource, solar energy has attracted interest from scientists all over the world. In order to increase its efficient use, solar concentrators maximizing sun power density are widely used in solar energy research and applications. New progress in solar concentrators is of vital importance for further breakthroughs in the following and many other research areas:

Solar CPV electricity generation;
Solar fuel production of H2, syngas, liquid, and gas hydrocarbons;
Cycles for chemical storage of solar energy with ZnO, CeO2, iron, and silica;
High added-value material synthesis and/or coating deposits of nanomaterials, new ceramics or metals, foams, catalytic layers;
High-flux photochemistry and photophysics;
Characterization of materials’ behavior and properties under extreme conditions;
Solar pumping of laser for industrial and space applications.

Challenge and research trends of both primary and secondary solar concentrators are key issues for advanced solar energy research. Therefore, the topics of interest include but are not limited to:

Primary solar concentrators

Parabolic solar concentrators, flat Fresnel lenses, dome-shaped Fresnel lenses, ring array concentrators (RACs), and three-dimensional ring array concentrators (3D RACs).

Secondary imaging and non-imaging concentrators

Fused silica aspheric lenses, dielectric totally internally reflecting secondary concentrators (DTIRCs), fused silica liquid light guide lenses, two-dimensional compound parabolic concentrators (2D-CPCs), three-dimensional compound parabolic concentrators (3D-CPCs).

Emerging solar concentrators

Microcompound parabolic concentrators; maximizing the efficiency of luminescent solar concentrators by implanting resonant plasmonic nanostructures; enhancing light conversion efficiency in a luminescent solar concentrator using a prism film; polygonal luminescent waveguides; freeform RXI optics; holographic elements for spectrum-splitting PV systems; 3D-printed concentrators for tracking-integrated CPV modules; freeform waveguides for solar concentrated PV technology; spectrum splitting CSP/CPV collectors with InGaP/GaAs solar cells; new luminescent solar concentrators.

Solar-pumped lasers with secondary and tertiary concentrators.

Nd:YAG solar-pumped lasers, Ce:Nd:YAG solar-pumped lasers; novel solar laser pumping approaches with solar concentrators; solar laser applications.

Prof. Dr. Dawei Liang
Prof. Dr. Changming Zhao
Guest Editors

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Keywords

Primary solar concentrators
Secondary concentrators
High solar flux
Fresnel lens
Solar-pumped lasers

Published Papers (11 papers)

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Research

15 pages, 5656 KiB

Open AccessArticle

Ce:Nd:YAG Solar Laser with 4.5% Solar-to-Laser Conversion Efficiency

by Dário Garcia, Dawei Liang, Cláudia R. Vistas, Hugo Costa, Miguel Catela, Bruno D. Tibúrcio and Joana Almeida

Energies 2022, 15(14), 5292; https://doi.org/10.3390/en15145292 - 21 Jul 2022

Cited by 23 | Viewed by 1975

Abstract

The efficiency potential of a small-size solar-pumped laser is studied here. The solar laser head was composed of a fused silica aspheric lens and a conical pump cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic mirror with an effective collection area of 0.293 m² to end-side pump a Ce (0.1 at%):Nd (1.1 at%):YAG rod of 2.5 mm diameter and 25 mm length. Optimum solar laser design parameters were found through Zemax^© non-sequential ray-tracing and LASCAD™ analysis. The utilization of the Ce:Nd:YAG medium with small diameter pumped by a small-scale solar concentrator was essential to significantly enhance the end-side pump solar laser efficiency and thermal performance. For 249 W incoming solar power at an irradiance of 850 W/m², 11.2 W multimode solar laser power was measured, corresponding to the record solar-to-laser power conversion efficiency of 4.50%, being, to the best of our knowledge, 1.22 times higher than the previous record. Moreover, the highest solar laser collection efficiency of 38.22 W/m² and slope efficiency of 6.8% were obtained, which are 1.18 and 1.02 times, respectively, higher than the previous records. The lowest threshold solar power of a Ce:Nd:YAG solar-pumped laser is also reported here. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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10 pages, 1560 KiB

Open AccessArticle

40 W Continuous Wave Ce:Nd:YAG Solar Laser through a Fused Silica Light Guide

by Joana Almeida, Dawei Liang, Dário Garcia, Bruno D. Tibúrcio, Hugo Costa, Miguel Catela, Emmanuel Guillot and Cláudia R. Vistas

Energies 2022, 15(11), 3998; https://doi.org/10.3390/en15113998 - 29 May 2022

Cited by 18 | Viewed by 2216

Abstract

The solar laser power scaling potential of a side-pumped Ce:Nd:YAG solar laser through a rectangular fused silica light guide was investigated by using a 2 m diameter parabolic concentrator. The laser head was formed by the light guide and a V-shaped pump cavity to efficiently couple and redistribute the concentrated solar radiation from the parabolic mirror to a 4 mm diameter, 35 mm length Ce(0.1 at.%):Nd(1.1 at.%):YAG laser rod. The rectangular light guide ensured a homogeneous distribution of the solar radiation along the laser rod, allowing it to withstand highly concentrated solar energy. With the full collection area of the parabolic mirror, the maximum continuous wave (cw) solar laser power of 40 W was measured. This, to the best of our knowledge, corresponds to the highest cw laser power obtained from a Ce:Nd:YAG medium pumped by solar radiation, representing an enhancement of two times over that of the previous side-pumped Ce:Nd:YAG solar laser and 1.19 times over the highest Cr:Nd:YAG solar laser power with a rectangular light-guide. This research proved that, with an appropriate pumping configuration, the Ce:Nd:YAG medium is very promising for scaling solar laser output power to a higher level. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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12 pages, 3948 KiB

Open AccessArticle

Uniform and Non-Uniform Pumping Effect on Ce:Nd:YAG Side-Pumped Solar Laser Output Performance

by Cláudia R. Vistas, Dawei Liang, Dário Garcia, Miguel Catela, Bruno D. Tibúrcio, Hugo Costa, Emmanuel Guillot and Joana Almeida

Energies 2022, 15(10), 3577; https://doi.org/10.3390/en15103577 - 13 May 2022

Cited by 20 | Viewed by 1822

Abstract

The Ce:Nd:YAG is a recent active medium in solar-pumped lasers with great potential. This study focuses on the influence of two secondary concentrators: a fused silica aspherical lens and a rectangular fused silica light guide; and consequent pump light distribution on the output performance of a Ce:Nd:YAG side-pumped solar laser. The solar laser head with the aspherical lens concentrated the incident pump light on the central region of the rod, producing the highest continuous-wave 1064 nm solar laser power of 19.6 W from the Ce:Nd:YAG medium. However, the non-uniformity of the absorbed pump profile produced by the aspherical lens led to the rod fracture because of the high thermal load, limiting the maximum laser power. Nevertheless, the solar laser head with the light guide uniformly spread the pump light along the laser rod, minimizing the thermal load issues and producing a maximum laser power of 17.4 W. Despite the slight decrease in laser power, the use of the light guide avoided the laser rod fracture, demonstrating its potential to scale to higher laser power. Therefore, the pumping distribution on the rod may play a fundamental role for Ce:Nd:YAG solar laser systems design. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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12 pages, 3756 KiB

Open AccessArticle

Thermo-Economic Performance Evaluation of a Conical Solar Concentrating System Using Coil-Based Absorber

by Haedr Abdalha Mahmood Alsalame, Muhammad Imtiaz Hussain, Waseem Amjad, Asma Ali and Gwi Hyun Lee

Energies 2022, 15(9), 3369; https://doi.org/10.3390/en15093369 - 05 May 2022

Cited by 1 | Viewed by 1317

Abstract

Pollution and the increase in greenhouse gas (GHG) emissions have long been linked to the world’s increasing need for fossil fuels to generate energy. Every day, the energy consumption is increasing; therefore, it is important to improve technologies that use renewable energy sources. With the abundant availability of sustainable energy, solar power is becoming a necessity. However, solar energy has a low energy density and therefore requires a large installation area, which requires heat collection and heat storage technology. Much research is now being done on the conical solar systems to improve efficiency including calculating an optimal cone angle, finding the best flow ratio and the best absorber design, etc. Therefore, in this study, thermal performance of a conical solar collector (CSC) was assessed with a new design of concentric tube absorber (addition of a coil) and compared to the existing circular tube absorber. It was found that 6 L/min flow rate of heating medium (distilled water and CuO nanofluid) gave lower payback period and higher solar fraction of the system in both cases of absorber tube, i.e., without coil and with coil. However, comparatively, thermal efficiency of CSC with coil-based absorber was almost 10–12% higher than conventional system (without coil) regardless of type of heating medium used. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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13 pages, 3599 KiB

Open AccessArticle

Highly Efficient Solar Laser Pumping Using a Solar Concentrator Combining a Fresnel Lens and Modified Parabolic Mirror

by Zitao Cai, Changming Zhao, Ziyin Zhao, Xingyu Yao, Haiyang Zhang and Zilong Zhang

Energies 2022, 15(5), 1792; https://doi.org/10.3390/en15051792 - 28 Feb 2022

Cited by 4 | Viewed by 3300

Abstract

Solar-pumped lasers (SPLs) allow direct solar-to-laser power conversion, and hence, provide an opportunity to harness a renewable energy source. Herein, we report significant improvements in end-side-pumped solar laser collection efficiency and beam brightness using a novel 1.5-m-diameter compound solar concentrator combining a Fresnel lens and modified parabolic mirror. A key component of this scheme is the off-axis-focused parabolic mirror. An original dual-parabolic pump cavity is another feature. To determine the dependence of the SPL performance on the distance between the focus and central axis of the modified parabolic mirror, several systems with different distances were optimized using TracePro and ASLD software. It was numerically calculated that end-side pumping a 5-mm-diameter, 22-mm-long Nd:YAG crystal rod would generate 74.6 W of continuous-wave solar laser power at a collection efficiency of 42.2 W/m², i.e., 1.1 times greater than the previous record value. Considering the laser beam quality, a brightness figure of 0.063 W was obtained, which is higher than that of other multimode SPL designs with end-side pumping. Thus, our SPL concentrator offers the possibility of achieving a beam quality as high as that obtainable via side pumping, alongside highly efficient energy conversion, which is characteristic to end-side pumping. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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16 pages, 8600 KiB

Open AccessFeature PaperArticle

Fixed Fiber Light Guide System with Concave Outlet Concentrators

by Bangdi Zhou, Kaiyan He, Ziqian Chen and Shuiku Zhong

Energies 2022, 15(3), 982; https://doi.org/10.3390/en15030982 - 28 Jan 2022

Cited by 1 | Viewed by 2525

Abstract

Because a traditional optical fiber light guiding system includes a tracking device, it also inevitably has a complex structure, high construction and maintenance costs, short life span and low reliability. Although several types have been developed for decades, there are no successful products on the market. The biggest cause of the problem is that all traditional optical fiber light guiding systems must have a tracking device. This paper studies a solar fiber optic guide system without a tracking device, hoping to solve this problem. A fixed fiber light guide system using concave outlet concentrators as its receiving unit is proposed. The structure and working principle of the concave outlet concentrator, the receiving unit and the light guide system are introduced. With optical simulation software and the actual sunlight experimental method, this paper first discusses the conceptual design of the concentrator, then studies the transmission efficiency curve of the receiving unit with different angles of incident light, and finally tests the output illuminance of the whole system in actual sunlight. Field test results show that when the average sunshine intensity is about 800 W/m², the system has an output of nearly 300 lux at 0.4 m in front of the outlet end of the fiber bundle with only

3.11 \times 10^{- 2} m^{2}

receiving area. This illumination has been able to meet people’s daily lighting requirements. The results of computer simulation and actual sunlight experiments show that this fixed optical fiber light guide system with non-tracing structure is feasible. The absence of a tracking structure means that all moving parts of the system are completely discarded. This greatly improves the working reliability and operation life of the light guide system, and greatly reduces the maintenance and operating costs. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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21 pages, 6651 KiB

Open AccessArticle

Elliptical-Shaped Fresnel Lens Design through Gaussian Source Distribution

by Dário Garcia, Dawei Liang, Joana Almeida, Bruno D. Tibúrcio, Hugo Costa, Miguel Catela and Cláudia R. Vistas

Energies 2022, 15(2), 668; https://doi.org/10.3390/en15020668 - 17 Jan 2022

Cited by 2 | Viewed by 2908

Abstract

A novel three-dimensional elliptical-shaped Fresnel lens (ESFL) analytical model is presented to evaluate and maximize the solar energy concentration of Fresnel-lens-based solar concentrators. AutoCAD, Zemax and Ansys software were used for the ESFL design, performance evaluation and temperature calculation, respectively. Contrary to the previous modeling processes, based on the edge-ray principle with an acceptance half-angle of ±0.27° as the key defining parameter, the present model uses, instead, a Gaussian distribution to define the solar source in Zemax. The results were validated through the numerical analysis of published experimental data from a flat Fresnel lens. An in-depth study of the influence of several ESFL factors, such as focal length, arch height and aspect ratio, on its output performance is carried out. Moreover, the evaluation of the ESFL output performance as a function of the number/size of the grooves is also analyzed. Compared to the typical 1–16 grooves per millimeter reported in the previous literature, this mathematical parametric modeling allowed a substantial reduction in grooves/mm to 0.3–0.4, which may enable an easy mass production of ESFL. The concentrated solar distribution of the optimal ESFL configuration was then compared to that of the best flat Fresnel lens configuration, under the same focusing conditions. Due to the elliptical shape of the lens, the chromatic aberration effect was largely reduced, resulting in higher concentrated solar flux and temperature. Over 2360 K and 1360 K maximum temperatures were found for ESFL and flat Fresnel lenses, respectively, demonstrating the great potential of the three-dimensional curved-shaped Fresnel lens on renewable solar energy applications that require high concentrations of solar fluxes and temperatures. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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10 pages, 1768 KiB

Open AccessArticle

Effects of Nanofluids in Improving the Efficiency of the Conical Concentrator System

by Alsalame Haedr Abdalha Mahmood, Muhammad Imtiaz Hussain and Gwi-Hyun Lee

Energies 2022, 15(1), 28; https://doi.org/10.3390/en15010028 - 21 Dec 2021

Cited by 3 | Viewed by 2071

Abstract

Fossil fuels are being depleted, resulting in increasing environmental pollution due to greenhouse gases and, consequently, emerging detrimental environmental problems. Therefore, renewable energy is becoming more important; hence, significant research is in progress to increase efficient uses of solar energy. In this paper, the thermal performance of a conical concentrating system with different heat transfer fluids at varied flow rates was studied. The conical-shaped concentrator reflects the incoming solar radiation onto the absorber surface, which is located at the focal axis, where the collected heat is transported through heating mediums or heat transfer fluids. Distilled water and nanofluids (Al₂O₃, CuO) were used in this study as the heat transfer fluids and were circulated through the absorber and the heat storage tank in a closed loop by a pump to absorb the solar radiation. The efficiency of the conical concentrating system was measured during solar noon hours under a clear sky. The collector efficiency was analyzed at different flow rates of 2, 4, and 6 L/min. The thermal efficiency, calculated using different heat transfer fluids, were 72.5% for Al₂O₃, 65% for CuO, and 62.8% for distilled water. Comparing the thermal efficiency at different flow rates, Al₂O₃ at 6 L/min, CuO at 6 L/min, and distilled water at 4 L/min showed high efficiencies; these results indicate that the Al₂O₃ nanofluid is the better choice for use as a heating medium for practical applications. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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18 pages, 9708 KiB

Open AccessArticle

Doughnut-Shaped and Top Hat Solar Laser Beams Numerical Analysis

by Miguel Catela, Dawei Liang, Cláudia R. Vistas, Dário Garcia, Bruno D. Tibúrcio, Hugo Costa and Joana Almeida

Energies 2021, 14(21), 7102; https://doi.org/10.3390/en14217102 - 31 Oct 2021

Cited by 6 | Viewed by 2247

Abstract

Aside from the industry-standard Gaussian intensity profile, top hat and non-conventional laser beam shapes, such as doughnut-shaped profile, are ever more required. The top hat laser beam profile is well-known for uniformly irradiating the target material, significantly reducing the heat-affected zones, typical of Gaussian laser irradiation, whereas the doughnut-shaped laser beam has attracted much interest for its use in trapping particles at the nanoscale and improving mechanical performance during laser-based 3D metal printing. Solar-pumped lasers can be a cost-effective and more sustainable alternative to accomplish these useful laser beam distributions. The sunlight was collected and concentrated by six primary Fresnel lenses, six folding mirror collectors, further compressed with six secondary fused silica concentrators, and symmetrically distributed by six twisted light guides around a 5.5 mm diameter, 35 mm length Nd:YAG rod inside a cylindrical cavity. A top hat laser beam profile (M_x² = 1.25, M_y² = 1.00) was computed through both ZEMAX^® and LASCAD^® analysis, with 9.4 W/m² TEM₀₀ mode laser power collection and 0.99% solar-to-TEM₀₀ mode power conversion efficiencies. By using a 5.8 mm laser rod diameter, a doughnut-shaped solar laser beam profile (M_x² = 1.90, M_y² = 1.00) was observed. The 9.8 W/m² TEM₀₀ mode laser power collection and 1.03% solar-to-TEM₀₀ mode power conversion efficiencies were also attained, corresponding to an increase of 2.2 and 1.9 times, respectively, compared to the state-of-the-art experimental records. As far as we know, the first numerical simulation of doughnut-shaped and top hat solar laser beam profiles is reported here, significantly contributing to the understanding of the formation of such beam profiles. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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16 pages, 6471 KiB

Open AccessArticle

Zigzag Multirod Laser Beam Merging Approach for Brighter TEM₀₀-Mode Solar Laser Emission from a Megawatt Solar Furnace

by Hugo Costa, Joana Almeida, Dawei Liang, Miguel Catela, Dário Garcia, Bruno D. Tibúrcio and Cláudia R. Vistas

Energies 2021, 14(17), 5437; https://doi.org/10.3390/en14175437 - 01 Sep 2021

Cited by 5 | Viewed by 2365

Abstract

An alternative multirod solar laser end-side-pumping concept, based on the megawatt solar furnace in France, is proposed to significantly improve the TEM₀₀-mode solar laser output power level and its beam brightness through a novel zigzag beam merging technique. A solar flux homogenizer was used to deliver nearly the same pump power to multiple core-doped Nd:YAG laser rods within a water-cooled pump cavity through a fused silica window. Compared to the previous multibeam solar laser station concepts for the same solar furnace, the present approach can allow the production of high-power TEM₀₀-mode solar laser beams with high beam brightness. An average of 1.06 W TEM₀₀-mode laser power was numerically extracted from each of 1657 rods, resulting in a total of 1.8 kW. More importantly, by mounting 399 rods at a 30° angle of inclination and employing the beam merging technique, a maximum of 5.2 kW total TEM₀₀-mode laser power was numerically extracted from 37 laser beams, averaging 141 W from each merged beam. The highest solar laser beam brightness figure of merit achieved was 148 W, corresponding to an improvement of 23 times in relation to the previous experimental record. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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20 pages, 6877 KiB

Open AccessArticle

Elliptic Array Luminescent Solar Concentrators for Combined Power Generation and Microalgae Growth

by Nima Talebzadeh and Paul G. O’Brien

Energies 2021, 14(17), 5229; https://doi.org/10.3390/en14175229 - 24 Aug 2021

Cited by 3 | Viewed by 1754

Abstract

The full utilization of broadband solar irradiance is becoming increasingly useful for applications such as long-term space missions, wherein power generation from external sources and regenerative life support systems are essential. Luminescent solar concentrators (LSCs) can be designed to separate sunlight into photosynthetically active radiation (PAR) and non-PAR to simultaneously provide for algae cultivation and electric power generation. However, the efficiency of LSCs suffers from high emission losses. In this work, we show that by shaping the LSC in the form of an elliptic array, rather than the conventional planar configuration, emission losses can be drastically reduced to the point that they are almost eliminated. Numerical results, considering the combined effects of emission, transmission and surface scattering losses show the optical efficiency of the elliptic array LSC is 63%, whereas, in comparison, the optical efficiency for conventional planar LSCs is 47.2%. Further, results from numerical simulations show that elliptic array luminescent solar concentrators can convert non-PAR and green-PAR to electric power with a conversion efficiency of ~17% for AM1.5 and 17.6% for AM0, while transmitting PAR to an underlying photobioreactor to support algae cultivation. Full article

(This article belongs to the Special Issue Challenge and Research Trends of Solar Concentrators)

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