Search Results (40)

The development of ultrahigh-concentration photovoltaic (UHCPV) systems plays a pivotal role in advancing sustainable solar energy technologies. As the demand for clean energy grows, the need to align concentrated photovoltaic (CPV) system design with high-efficiency solar cell production becomes critical for maximizing energy yield while minimizing resource use. Despite some experimental efforts in UHCPV development, there remains a gap in integrating Fresnel lens-based systems with the comprehensive thermal modeling of key components in improving system sustainability and performance. To bridge this gap and promote more energy-efficient designs, a detailed numerical model was established to evaluate both the thermal and optical performance of a UHCPV system. This model contributes to the sustainable design process by enabling informed decisions on system efficiency, thermal management, and material optimization before physical prototyping. Through COMSOL Multiphysics simulations, the system was assessed under direct normal irradiance (DNI) ranging from 400 to 1000 W/m². Optical simulations indicated a high theoretical optical efficiency of ~93% and a concentration ratio of 1361 suns, underscoring the system’s potential to deliver high solar energy conversion with minimal land and material footprint. Moreover, the integration of thermal and optical modeling ensures a holistic understanding of system behavior under varying ambient temperatures (20–50 °C) and convective cooling conditions (heat transfer coefficients between 4 and 22 W/m².K). The results showed that critical optical components remain within safe temperature thresholds (<54 °C), while the receiver stage operates between 78.5 °C and 157.4 °C. These findings highlight the necessity of an effective cooling mechanism—not only to preserve system longevity and safety but also to maintain high conversion efficiency, thereby supporting the broader goals of sustainable and reliable solar energy generation. Full article

A multirod Ce:Nd:YAG solar laser approach, using a Fresnel lens as a primary concentrator, is here proposed with the aim of considerably increasing the efficiency of solar-pumped lasers. Fresnel lenses are cost-effective, rendering solar lasers more economically competitive. In this work, solar-pumped radiation collected and concentrated using the Fresnel lens is received by a secondary three-dimensional compound parabolic concentrator which transmits and funnels the light toward the Ce:Nd:YAG laser rods within a water-cooled tertiary conical concentrator that enables efficient multipass pumping of the rods. To explore the full potential of the proposed approach, the performance of various multirod configurations is numerically evaluated. Through this study, configurations with three and seven Ce:Nd:YAG rods are identified as being the most efficient. A maximum continuous wave total laser power of 122.8 W is reached with the three-rod configuration, marking the highest value from a Ce:Nd:YAG solar laser, leading to solar-to-laser conversion and collection efficiencies of 7.31% and 69.50 W/m², respectively. These results represent enhancements of 1.88 times and 1.79 times, respectively, over the previous experimental records from a Ce:Nd:YAG/YAG single-rod solar laser with a Fresnel lens. Furthermore, the above results are also 1.58 times and 1.68 times, respectively, greater than those associated with the most effective three-rod Ce:Nd:YAG solar laser utilizing a parabolic mirror as the main concentrator. The present study also shows the great usefulness of the simultaneous pumping of multiple laser rods in terms of reducing the thermal stress effects in active media, being the seven-rod configuration the one that offered the best compromise between maximum efficiency and thermal performance. This is crucial for the applicability of this sustainable technology, especially if we wish to scale our system to higher power laser levels. Full article

This paper aims to compare the thermal performances of the conical solar collector (CSC) system and the spot Fresnel lens system (SFL) using water and CuO nanofluid as the working fluids. The studied CFD models for both systems were validated using experimental data. At an optimal flow rate of 6 L/min, the SFL system showed higher optical and thermal performance in comparison with that of the CSC system. In the case of the SFL system, the availability of a greater amount of solar energy per unit collector area caused an increase in thermal energy. Moreover, in the case of the CSC system, the non-uniform distribution of solar flux on the absorber’s outer surface leads to an increase in temperature gradient and heat losses. As a heating medium, the CuO nanofluid outperformed the water in terms of higher thermal conductivity and heat capacity. The average thermal efficiencies of 64.7% and 61.2% were achieved using SFL with and without CuO nanofluid, respectively, which were 2.4% and 0.5% higher than those of the CSC with and without nanofluid. CFD simulations show a 2.80% deviation for SFL and 2.92% for CSC, indicating acceptable accuracy compared to experimental data. Full article

Ultrasonic focusing transducers have broad prospects in advanced ultrasonic non-destructive testing fields. However, conventional focusing methods that use acoustic concave lenses can disrupt the acoustic impedance matching condition, thereby adversely affecting the sensitivity of the transducers. In this paper, an active focusing planar ultrasonic transducer is designed and presented to achieve a focusing effect with a higher sensitivity. An electrode pattern consisting of multiple concentric rings is designed, which is inspired by the structure of Fresnel Zone Plates (FZP). The structural parameters are optimized using finite element simulation methods. A prototype of the transducer is manufactured with electrode patterns made of conductive silver paste using silk screen-printing technology. Conventional focusing transducers using an acoustic lens and an FZP baffle are also manufactured, and their focusing performances are comparatively tested. The experimental results show that our novel transducer has a focal length of 16 mm and a center frequency of 1.16 MHz, and that the sensitivity is improved by 23.3% compared with the conventional focusing transducers. This research provides a new approach for the design of focusing transducers. Full article

This study proposes a rectangular-shaped optical module capable of simultaneously implementing crop cultivation and solar power generation. By employing a cylindrical Fresnel lens (CFL) array plate with a size of 100 × 100 mm², multiple focal lines are formed, where some of the incident light transmits through the module while the rest is guided laterally through the rectangular lightguide structure. This guided sunlight is then concentrated by a cylindrical compound parabolic concentrator (CCPC) structure, resulting in a 20-fold concentration ratio, onto a 5 × 100 mm² Si photovoltaic (PV) cell. To experimentally verify feasibility, both the CFL array plate and the lightguide plate were fabricated with three-axis machine tooling equipment and assembled. The power generated experimentally by the 5 × 100 mm² Si PV cell was 54% of the expected value from the simulation results on the light-concentrated efficiency considering experimental conditions, while the results on experimental transmittance along with rotation angles were very close to the simulation results. However, overall, the tendency of the generated power along the rotation angles is close to the tendency of the light-concentrated efficiency along the rotation angles from the simulation. Additionally, this study dealt with further consideration to enhance light-concentrated efficiency, introducing a means to adjust the trade-off relationship between transmittance and light-concentrated efficiency. Full article

We propose a new vortex lens for producing multiple focused coaxial vortices with approximately equal intensities along the optical axis, termed equal-intensity multi-focus composite spiral zone plates (EMCSZPs). In this typical methodology, two concentric conventional spiral zone plates (SZPs) of different focal lengths were composited together and the alternate transparent and opaque zones were arranged with specific m-bonacci sequence. Based on the Fresnel–Kirchhoff diffraction theory, the focusing properties of the EMCSZPs were calculated in detail and the corresponding demonstration experiment was been carried out to verify our proposal. The investigations indicate that the EMCSZPs indeed exhibit superior performance, which accords well with our physical design. In addition, the topological charges (TCs) of the multi-focus vortices can be flexibly selected and controlled by optimizing the parameters of the zone plates. These findings which were demonstrated by the performed experiment may open new avenues towards improving the performance of biomedical imaging, quantum computation and optical manipulation. Full article

Concentration of solar energy may be obtained by reflection, refraction, or a combination of the two. The collectors of a reflection system are designed to concentrate the sun’s rays onto a photovoltaic cell or steam tube. Refractive lenses concentrate light by having it travel through the lens. The sun’s rays are partially reflected and then refracted via a hybrid technique. Hybrid focus techniques have the potential to maximize power output. Fresnel lenses are an efficient tool for concentrating solar energy, which may then be used in a variety of applications. Development of both imaging and non-imaging devices is occurring at this time. Larger acceptance angles, better concentration ratios with less volume and shorter focal length, greater optical efficiency, etc., are only some of the advantages of non-imaging systems over imaging ones. This study encompasses numerical, experimental, and numerical and experimental studies on the use of Fresnel lenses in various solar energy systems to present a comprehensive picture of current scientific achievements in this field. The framework, design criteria, progress, and difficulties are all dissected in detail. Accordingly, some recommendations for further studies are suggested. Full article

The Fresnel lens is an optical system consisting of a series of concentric diamond grooves. One surface of the lens is smooth, while the other is engraved with concentric circles of increasing size. Optical interference, diffraction, and sensitivity to the angle of incidence are used to design the microstructure on the lens surface. The imaging of the optical surface depends on its curvature. By reducing the thickness of the lens, light can still be focused at the same focal point as with a thicker lens. Previously, lenses, including Fresnel lenses, were made of glass due to material limitations. However, the traditional grinding and polishing methods for making Fresnel lenses were not only time-consuming, but also labour-intensive. As a result, costs were high. Later, a thermal pressing process using metal moulds was invented. However, the high surface tension of glass caused some detailed parts to be deformed during the pressing process, resulting in unsatisfactory Fresnel lens performance. In addition, the complex manufacturing process and unstable processing accuracy hindered mass production. This resulted in high prices and limited applications for Fresnel lenses. These factors prevented the widespread use of early Fresnel lenses. In contrast, polymer materials offer advantages, such as low density, light weight, high strength-to-weight ratios, and corrosion resistance. They are also cost effective and available in a wide range of grades. Polymer materials have gradually replaced optical glass and other materials in the manufacture of micro-optical lenses and other miniaturised devices. Therefore, this study focuses on investigating the manufacturing parameters of Fresnel lenses in the injection moulding process. We compare the quality of products obtained by two-stage injection moulding, injection compression moulding, and IMD (in-mould decoration) techniques. The results show that the optimal method is IMD, which reduces the nodal displacement on the Fresnel lens surface and improves the transmission performance. To achieve this, we first establish a Kriging model to correlate the process parameters with optimisation objectives, mapping the design parameters and optimisation objectives. Based on the Kriging model, we integrate the NSGA-II algorithm with the predictive model to obtain the Pareto optimal solutions. By analysing the Pareto frontier, we identify the best process parameters. Finally, it is determined that the average nodal displacement on the Fresnel surface is 0.393 mm, at a holding pressure of 320.35 MPa and a melt temperature of 251.40 °C. Combined with IMD technology, product testing shows a transmittance of 95.43% and an optimisation rate of 59.64%. Full article

In order to address the issue of a solar utilization system with low efficiency, this paper designs a new solar conversion system based on photovoltaic concentration and spectral splitting. The system concentrates sunlight through a Fresnel lens and uses a hollow concave cavity to evenly distribute the incident energy flow. The spectral splitting medium separates the useful irradiance for the PV cell from those wavelengths that are more suited to heat generation. By considering the available wavelength of photovoltaic cells, the GaAs cell and a ZnO nanofluid were selected for this paper. It was found that installing the hollow concave cavity improved the spot uniformity of the PV cell surface by 17%. The output efficiency of the system under various circumstances was analyzed. The results show that at a concentration ratio of 50 and a light intensity of 1000 W/m², photoelectric conversion efficiency increased by 0.81%. When compared to direct concentration, the photoelectric conversion efficiency increased by at least 7%. Meanwhile, the comprehensive electrical efficiency was 36.7%, which is higher than that of the normal concentration PV and comprehensive thermal system. Full article

Significant numerical improvements in Fresnel lens Nd:YAG solar laser collection efficiency, laser quality factors and tracking error compensation capacity by two Fresnel lenses as primary solar concentrators are reported here. A Nd:YAG four-rod side-pumping configuration was investigated. The four-rod side-pumping scheme consisted of two large aspherical lenses and four semi-cylindrical pump cavities, where the Nd:YAG laser rods were placed, enabling an efficient solar pumping of the laser crystals. A 104.4 W continuous-wave multimode solar laser power was achieved, corresponding to 29.7 W/m² collection efficiency, which is 1.68 times that of the most efficient experimental Nd:YAG side-pumped solar laser scheme with heliostat–parabolic mirror systems. End-side-pumped configuration has led to the most efficient multimode solar lasers, but it may cause more prejudicial thermal effects, poor beam quality factors and a lack of access to both rod end-faces to optimize the resonant cavity parameters. In the present work, an eight-folding-mirror laser beam merging technique was applied, aiming to attain one laser emission from the four laser rods that consist of the four-rod side-pumping scheme with a higher brightness figure of merit. A 79.8 W multimode laser output power was achieved with this arrangement, corresponding to 22.7 W/m². The brightness figure of merit was 0.14 W, being 1.6, 21.9 and 15.7 times that of previous experimental Nd:YAG solar lasers pumped by Fresnel lenses. A significant advance in tracking error tolerance was also numerically attained, leading to a 1.5 times enhancement in tracking error width at 10% laser power loss (TEW_10%) compared to previous experimental results. Full article

The glass cover is often situated at the aperture of a cavity receiver in concentrating collectors to reduce heat dissipation. However, the decrease in optical efficiency due to the reflection loss on the surface of the glass cover will directly reduce the thermal efficiency of a collector, especially for a fixed-focus solar concentrator, whose optical axis is generally not coincident with the central axis of the receiver. To fundamentally evaluate the effect of a glass cover on the efficiency of a fixed-focus Fresnel lens solar concentrator/conical cavity receiver system, its performances with and without a glass cover considered under different incidence angles were comparatively investigated. To obtain the optical performance, optical models of the system were first built with TracePro^® 7.0 software. An experimental setup was then constructed to test the thermal performance of the system. The results show that the optical efficiency of a system without a glass cover is much higher than that with a glass cover. The difference between them remains unchanged for incidence angle at a range of 0–20°. The time constant of the system with a glass cover is much less than that without a glass cover, in the ranges of 29–33 s and 48–59 s, respectively. The system with a glass cover for a wide range of higher temperature differences also has better thermal efficiency. Full article

A multirod solar laser approach is here proposed to attain uniform and stable multibeam emission under non-continuous solar tracking. A Fresnel lens was used as the primary concentrator. The laser head was composed of a second-stage aspherical lens with a light-guide homogenizer and a third-stage conical pump cavity with six Nd:YAG rods. The solar laser system was optimized through numerical analysis in both Zemax^® and LASCAD™ software to obtain six 1064 nm laser beams of similar multimode power. To investigate the effect of the homogenizer on the laser performance, the laser head was compared with a similar one that only used the aspherical lens in the second stage. The approach with the light guide attained a slightly lower efficiency than the one without the light guide; however, the tracking error width at 10% laser power loss was higher and, most importantly, only a 2.17% coefficient of variation of the laser power emitted by the six rods at the tracking error angle of ±0.5° was obtained. This is 4.2 times better than the 52.31% obtained with the laser head without the homogenizer and 76 times better than that of the previous numerical work. The light guide is thus essential to ensure uniform and stable solar laser power extraction from all rods even under non-continuous solar tracking, making this prototype the ideal for multibeam laser applications where uniformity and stability of the laser power are indispensable. This renewable multibeam solar laser may replace the classical lamp- and diode-pumped lasers, therefore ensuring a sustainable laser power production pattern for both space and terrestrial applications. Full article

This work aims to create a web-based real-time monitoring system for electrical energy consumption inside a specific residence. This electrical energy is generated from a micro-CPV system lying on the roof of this residence. The micro-CPV is composed of a Fresnel lens as the main optical element, a spherical lens as the secondary optical element, and a multi-junction solar cell. A tiny photovoltaic concentrator system with a geometric concentration ratio of 100× is analyzed in the first part of this study, while the second part is designed to monitor the electricity generated by the micro-CPV system. An ESP8266 controller chipset is used to build the sensing peripheral node, which controls a relay and a PZEM-004T current sensor. As a result, the optical element used has approximately 83% optical efficiency, with an acceptance angle of 1.5°. Regarding the monitoring system, the architecture demonstrates the ability of the system to monitor current and energy consumption in real time using a computer or smartphone and a web server specially designed to continuously update the power consumption profile in a specific smart home environment. The whole electric power consumption monitoring system generally worked well. The monitoring system is configured to provide excellent accuracy for a 0.6% hit. Full article

The materials used to manufacture solar receivers for tower power plants must withstand high fluxes of concentrated solar radiation (from $0.1$ to even $1.5$ MWm${}^{-2}$) and operate at high operating temperatures (>800 °C). Durability is a key aspect in these systems, which must be ensured under these demanding operating conditions, which also include daily heating–cooling cycles throughout the lifetime of these power plants. So far, to the authors’ knowledge, which wavelengths of concentrated solar radiation have the greatest influence on the mechanisms and speed of aging of materials used in solar receivers has not been analyzed. Yet, such an analysis is pertinent in order to implement strategies that delay or inhibit such phenomena, and, thus, increase the durability of central tower systems’ receivers. To perform such analyses, a new solar furnace was recently designed and installed at the Plataforma de Almería (Spain). This paper describes the components of this new solar furnace. The components are as follows: a heliostat to redirect the direct solar radiation towards a Fresnel lens that concentrates the solar radiation on the material under study, a shutter that allows varying the amount of concentrated solar radiation incident on the Fresnel lens, and reflective filters with selective reflectance that are placed between the Fresnel lens and the material. This paper also describes the procedure and the first results of the energetic and spectral characterization of this new solar furnace. The first experimental results of the characterization of this new test bed using the heliostat and the Fresnel lens showed that concentration ratios of up to 1000 suns (1 sun = 1000 Wm${}^{-2}$) could be achieved. Furthermore, the paper presents the results of the spectral characterization of the test system, using selective reflectance mirrors in the near-visible–IR wavelength range (400–1125 nm) and in the visible–IR red region (700–2500 nm). Full article

The energy efficiency of a small-scale solar concentrating thermal device is investigated, based on Monte-Carlo Ray-Tracing (MCRT) and Computational Fluid Dynamics (CFD) modeling. The device consists of a Fresnel lens collector—engraved on a 1 m rectangular plate—and a 10 cm sized plate receiver, with drilled cylindrical channels with a diameter of 10 mm. Inlet velocities and heat transfer fluid (HTF) temperatures lie within the range of 0.25–1 m/s and 100–200 °C, respectively. The configurations examined involve the utilization of a selective coating on the absorbing surface of the receiver, increasing the channel diameter to 15 mm and the receiver size to 20 cm, and insertion of a glass envelope in front of the absorbing surface. Energy efficiency increases with increasing fluid velocity up to 80%, a level beyond which no further improvement is observed. The coating contributes to a reduction in heat losses; it brings substantial benefits for the lower velocities examined. The increase in channels diameter also contributes to an increase in the energy efficiency, while the increase in receiver dimensions leads to the opposite effect. The glass cover does not improve the performance of the collector, due to substantial optical losses. Full article