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Using the previously developed optimization method for an extended light source [Byzov EV, Kravchenko SV, Moiseev MA, Bezus EA, Doskolovich LL. Optimization method for designing double-surface refractive optical elements for an extended light source. Opt Express 2020; 28(17): 24431-24443. DOI: 10.1364/OE.400609], we designed a compact refractive optical element (the ratio of the element height to the light source size being 1.55) providing a uniform illuminance distribution in a shifted rectangular region. An application of the optimization method for calculating the so-called TIR-elements, exploiting the phenomenon of the total internal reflection of rays, is considered. For an extended light source, compact TIR-elements with freeform exit surfaces that generate uniform illuminance distributions in a rectangular region are designed. The results of the work show promise for a wide class of problems of designing compact optical elements for light-emitting diodes.

A new source-target mapping for the design of refractive optical elements generating prescribed 2D intensity distributions is proposed. The calculation of the optical element is reduced to the solution of ordinary explicit differential equations. The simulation results presented demonstrate high performance of the proposed method. While generating uniform rectangular intensity distributions with angular dimensions varying from 80°×1° to 40°×20°, the normalized root-mean-square deviations between the generated and required distributions do not exceed 15 %.

In this work, we demonstrate a simple analytical approach to the problem of surface plasmon polaritons excitation with a metallic nanoantenna placed above a metal surface. The method uses the reciprocity theorem and is similar to the calculation of amplitudes of dielectric waveguide modes excited by a current distribution. To maximize clarity of the demonstration, we formulate the problem in a simple two-dimensional geometry. The analytical results are shown to agree well with the numerical solution obtained by finite elements in frequency domain and finite difference in time domain methods.

• Experimental performance of 45 m2 non-tracking solar thermal array described. • Performance evaluated at 80 °C, 135 °C, and 170 °C in dirty and clean conditions. • Annual thermal generation estimated 1000 kWh/m2 at 100 °C and 700 kWh/m2 at 160 °C. • $300/m2 installed, $6.5/m2 annual O&M, levelized cost of heat 2–4 cents per kWh. • Applications in desalination, evaporation, steam generation, process heating. In this paper, the experimental performance of a 45 m2 solar field of non-tracking external compound parabolic (XCPC) collectors installed at the University of California, Merced is described. The solar field was operated during July-August 2020 in both clean and dirty conditions and at varying operating temperatures (70, 135, 170 °C) while operating an air heater, thermal evaporator, and double effect absorption chiller. Performance data was used to develop an instantaneous solar field performance model which was then incorporated into an annual performance model using TMY3 data to estimate yearly production from the solar field. The model predicts an annual generation of ∼1100 kWh/m2-year at 80 °C, ∼1000 kWh/m2-year at 100 °C, ∼900 kWh/m2-year at 120 °C, ∼800 kWh/m2-year at 140 °C, and ∼700 kWh/m2-year at 160 °C in California. The XCPC technology is currently expected to have an installed cost of $300/m2 and an annual operations and maintenance cost of $6.5/m2-year. Over a 25 year lifetime it provides a levelized cost of heat at 2–4 cents per kWh th delivered. This is below the cost of commercial natural gas in California and at temperatures ≤ 120 °C below the cost of industrial natural gas, which highlights the potential of the XCPC technology for decarbonizing thermal applications such as water and space heating, drying, sterilization, desalination, evaporation, low pressure steam, double effect absorption chilling, process heating, and more. The lifetime cost of emissions reductions is ∼$169 per metric ton of avoided CO 2 when replacing natural gas, ∼$137/MT CO 2 when replacing propane, and ∼$83/MT CO 2 when replacing electric heating. [ABSTRACT FROM AUTHOR]

A method for designing an optical element with two free-form surfaces generating a prescribed illuminance distribution in the case of an extended light source is considered. The method is based on the representation of the optical element surfaces by bicubic splines and on the subsequent optimization of their parameters using a quasi-Newton method implemented in the Matlab software. To calculate the merit function, a version of the ray tracing method is proposed. Using the proposed method, an optical element with record characteristics was designed: the ratio of the element height to the source size is 1.6; luminous efficiency is 89.1 %; uniformity of the generated distribution (the ratio of the minimum and average illuminance) in a given square region is 0.92.

In this study, we proposed an innovative concept of integrating a polarized color-separating backlight with a color-filter-free LC panel for enhancing performance of the curved LCD system. We design a two-level folded backlight to exploit the light sources LEDs with color enhancement by quantum-dot technology to produce color beams emerging at separate angles with a linearly polarizing state. The integrated LC panel focuses the separating color beams onto the corresponding subpixels with no need of the color filter; redirects the color beams at respective angles into the normal and reforms their angular shapes to be identical for attaining good color uniformity in the viewing cone. We established a system model for simulation to evaluate its performance. According to the simulation results, it performs the high optical efficiency of 33.75% that is about four times the traditional LCD, and displays color gamut of 94.1% NTSC (CIE 1931). It also provides the illuminance uniformity of 90% above and good color uniformity in both the spatial space and angular space of the viewing cone with horizontal and vertical angular widths of 100o and 75o, respectively. Furthermore, the simulation results demonstrate that the design can apply to a 55-inch curved LCD and further extend the maximum diagonal size up to 88 inches while keeping slim volume with a minimal thickness of 6.5 mm.

The article deals with a problem of calculating two reflecting surfaces that form a given irradiance distribution with a flat wavefront, provided that a point source of light is used. A notion of a weak solution for the said problem is formulated and the equivalence of this problem and the Monge–Kantorovich mass transfer is proven.

The project team of University of California at Merced (UC-M), Gas Technology Institute, and Dr. Eli Yablonovitch of University of California at Berkeley developed a novel hybrid concentrated solar photovoltaic thermal (PV/T) collector using nonimaging optics and world record single-junction Gallium arsenide (GaAs) PV components integrated with particle laden gas as thermal transfer and storage media, to simultaneously generate electricity and high temperature dispatchable heat. The collector transforms a parabolic trough, commonly used in CSP plants, into an integrated spectrum-splitting device. This places a spectrum-sensitive topping element on a secondary reflector that is registered to the thermal collection loop. The secondary reflector transmits higher energy photons for PV topping while diverting the remaining lower energy photons to the thermal media, achieving temperatures of around 400°C even under partial utilization of the solar spectrum. The collector uses the spectral selectivity property of Gallium arsenide (GaAs) cells to maximize the exergy output of the system, resulting in an estimated exergy efficiency of 48%. The thermal media is composed of fine particles of high melting point material in an inert gas that increases heat transfer and effectively stores excess heat in hot particles for later on-demand use. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

A problem of calculating a refractive surface that forms a required irradiance distribution in the far field in the case of a plane illuminating beam is considered. We show that this problem can be formulated as a mass transportation problem. The specific form of the cost function for this problem is obtained. It is shown that with a certain choice of coordinates, the cost function becomes quadratic. The resulting mass transportation problem also describes a problem of calculating a mirror, which can be considered as a special case of the problem of calculating a refractive surface.

In this letter, an ellipsoid-spherical combined light source structure is presented for the purpose of uniform flux and color mixing, when considering heat dissipation. To allow more rays couple into spherical chamber while keeping illumination uniformity, algebraic equations to estimate light spot size focused by ellipsoidal reflector are derived and then employed to decide input slot size of the chamber. Then Monte Carlo ray tracing simulation suggests that the most preferable output slot size is between 15% and 30% of the chamber radius when considering both uniformity and available test area. A prototype with a 150-W Xenon arc lamp is fabricated to demonstrate heat distribution for the system, and experiment about uniformity indicates that 89.4% of the test circle radius can reach 2% nonuniformity. Color mixing performance for the system is studied by equipped with three ellipsoidal reflectors to collect rays from different color LEDs, and experiment shows that the maximum root-mean-square error of the spectrum across 90% of output circle radius is 1.4%. Results demonstrate it is a structure with simplified design process and having less dependence with light source type.

We consider a version of the supporting quadric method for designing freeform mirrors that generate prescribed irradiance distributions in the near field. The method is derived for a general case of an incident beam with an arbitrary wavefront. As an example, for a practically important special case of a plane incident wavefront, we design a freeform mirror that generates a complex-shaped uniform irradiance distribution in the form of the abbreviation “IPSI” on a zero background. The designed mirror is fabricated and qualitatively investigated in a proof-of-concept optical experiment. The experimental results confirm the correctness of the proposed approach and demonstrate the manufacturability of the mirrors designed using the considered method.

The problem of calculation of the light field eikonal defined on a certain surface from the condition of generating a prescribed irradiance distribution on another surface is formulated as a Monge-Kantorovich mass transportation problem. We show that the cost function in this mass transportation problem corresponds to the distance between a point on the initial surface (on which the eikonal function is defined) and a point on the target surface, where the prescribed irradiance distribution is to be generated. An analytical expression for the gradient of a “cost functional” describing the mass transportation problem is derived. It enables using gradient descent methods for the calculation of the eikonal function.

To enhance the concentration ratio and reduce the illumination system dimension in solar indoor illumination system, a planar solar concentrator is first applied in the solar illumination system and shows considerable concentration ratio and optical efficiency. The proposed planar solar concentrator can make adjustment of the number of collectors according to different concentration needs, which promotes the design freedom of solar illumination systems. Simulation results show that the optical efficiency of the system reaches 84.69% at a geometric concentration ratio of 250×. Experimental results show that when the geometric concentration ratios of the planar solar concentrators are 10, 20, 30 and 40, the optical efficiencies are 80.87%, 81.12%, 81.21% and 81.13%, respectively. The proposed design provides a new insight into possible designs of novel solar illumination system. • A novel design method of a planar illumination system is proposed. • The sunlight is split into two parts to improve the utilization of solar energy. • The proposed mathematical model can help the concentrator to achieve high efficiency. [ABSTRACT FROM AUTHOR]

In this manuscript, performance of a novel concentrated solar thermal collector with evacuated tube is studied. The focus is the optimization of cost and performance in respect to commercially available medium temperature collectors (100–300 °C) using thermal and economic index of heat generation system also known as Levelized Cost of Heat. In this project, Levelized Cost of Heat is optimized with material cost reduction while maintaining high thermal performance using economical aluminum fin (instead of copper), a glass cover and highly truncated aluminum reflector. The reflector is truncated using the nonimaging optics methods in order to maximize the optical efficiency while minimizing the material consumption. Also, in order to predict the thermal performance of the proposed collector, analytical and numerical simulation are studied. Finally, the collector is experimentally tested in three stages to measure maximum temperature, maximum efficiency and thermal efficiency at various temperature of heat transfer fluid. The mathematical, numerical and experimental results were found to have good agreement. The results indicate that the collector can operate with optical efficiency of 60%, maximum temperature of 350 °C, thermal efficiency of 51% and 42% at 100 °C and 200 °C respectively while the cost of energy is as low as 2.9 cents/kWh. • Low cost all glass evacuated tube collector with shallow CPC reflectors (Cx = 1.45X). • Derived expression for thermal efficiency including the concentration term (Cx). • Analytically and Numerically obtained the thermal efficiency of 42% at 200 °C. • Validated the efficiency results with real world experiment in thermal test loop. • Low cost material selection yields LCOH of 2.9 ₵/kWh, payback period of 5.6 years. [ABSTRACT FROM AUTHOR]

In this study, we proposed an innovative concept of integrating a polarized color-separating backlight with a color-filter-free LC panel for enhancing performance of the curved LCD system. We design a two-level folded backlight to exploit the light sources LEDs with color enhancement by quantum-dot technology to produce color beams emerging at separate angles with a linearly polarizing state. The integrated LC panel focuses the separating color beams onto the corresponding subpixels with no need of the color filter; redirects the color beams at respective angles into the normal and reforms their angular shapes to be identical for attaining good color uniformity in the viewing cone. We established a system model for simulation to evaluate its performance. According to the simulation results, it performs the high optical efficiency of 33.75% that is about four times the traditional LCD, and displays color gamut of 94.1% NTSC (CIE 1931). It also provides the illuminance uniformity of 90% above and good color uniformity in both the spatial space and angular space of the viewing cone with horizontal and vertical angular widths of 100o and 75o, respectively. Furthermore, the simulation results demonstrate that the design can apply to a 55-inch curved LCD and further extend the maximum diagonal size up to 88 inches while keeping slim volume with a minimal thickness of 6.5 mm. [ABSTRACT FROM AUTHOR]

• The specific derivation process of the concentrator module is given. • The designed concentrator can meet the needs of different degrees of concentration. • The system improves the utilization efficiency of light energy. • The system provides a guarantee for stable lighting energy output. This paper presents a design method of a natural light indoor illumination system using a planar solar concentrator as a daylighting module which can obtain high optical concentration ratios. In this design, the concentrator is composed of lens arrays, hemisphere-coupling structures, a lightguide, plate of beam splitters (PBS) and photovoltaic cells. The concentrated rays are divided into two parts by PBS, the visible rays for indoor illumination and the invisible rays for energy store. The converted electrical energy from invisible rays can drive the light emitting diodes (LEDs) at the entrance of the lightguide for illumination compensation in the condition of overcast and raining. Simulation results show that the proposed natural illumination system can achieve the illuminance more than 500 lx, which meets the commercial illumination requirement. In addition, the effects of collector width and parabolic coefficient on optical concentration ratio and concentration-acceptance product are discussed in detail. Finally, a prototype concentrator is constructed to demonstrate the viability of the proposed natural illumination system. The experimental measurements are in close agreement with simulation results. To the best of our knowledge, this is the first time that planar solar concentrators have been applied in the indoor illumination system, and our results can provide new insight into possible designs of novel natural illumination. [ABSTRACT FROM AUTHOR]

Lorentz geometry represents the mathematical foundation of Einstein's general relativity. From the concept of the cone of edge rays, it was introduced successfully in the study of homogeneous media nonimaging optics, Gutiérrez et al. (1996), Winston et al. (2005). In this paper we present a new Lorentzian geometry formalism to analyze optical systems with refractive elements. We have obtained the general system of partial differential equations and the integrability conditions to be fulfilled. This new mathematical formalism is the basis for a new optical technique to analyze the irradiance pattern produced by refractive optical systems. We apply this Lorentzian formalism to an optical media with exponential refraction index. Comparisons between irradiance patterns obtained by this formalism and by raytrace simulations are also presented. [ABSTRACT FROM AUTHOR]

We present a fast step-by-step method to design double free-form LED lens quickly; tiny rectangular light field with high efficiency can be achieved. Lens construction just need to derive two contour lines according to geometrical optics analysis. Lenses with different design angles are constructed according to the method, tiny rectangular light field from 2.3° × 1.2° to 6° × 10° can be achieved for a 1 mm × 1 mm LED source, optical simulation efficiency is higher than 83%, besides uniformity is higher than 79%. A manufactured lens proves the validity of the method. [ABSTRACT FROM AUTHOR]

In this letter, an ellipsoid–spherical combined light source structure is presented for the purpose of uniform flux and color mixing, when considering heat dissipation. To allow more rays couple into spherical chamber while keeping illumination uniformity, algebraic equations to estimate light spot size focused by ellipsoidal reflector are derived and then employed to decide input slot size of the chamber. Then Monte Carlo ray tracing simulation suggests that the most preferable output slot size is between 15% and 30% of the chamber radius when considering both uniformity and available test area. A prototype with a 150-W Xenon arc lamp is fabricated to demonstrate heat distribution for the system, and experiment about uniformity indicates that 89.4% of the test circle radius can reach 2% nonuniformity. Color mixing performance for the system is studied by equipped with three ellipsoidal reflectors to collect rays from different color LEDs, and experiment shows that the maximum root-mean-square error of the spectrum across 90% of output circle radius is 1.4%. Results demonstrate it is a structure with simplified design process and having less dependence with light source type. [ABSTRACT FROM AUTHOR]

• A three-dimensional compound parabolic concentrator (CPC) is designed for a high-temperature solar chemical reactor. • The optical design is guided by Monte Carlo ray-tracing simulations. • A cooling system is designed using engineering heat transfer correlations. • The CPC increases the concentration ratio, reduces spillage loss and reduces flux non-uniformity. A three-dimensional compound parabolic concentrator (CPC) is designed for high-temperature solar thermochemical applications driven by radiation from a multi-source high-flux solar simulator. The basic geometrical parameters of the CPC including the acceptance angle and the entry aperture radius are determined using optical simulations. A cooling system for overheating protection is designed using engineering heat transfer correlations. A prototype CPC is manufactured using additive manufacturing and single point diamond turning techniques. The optical simulations show that the CPC increases the concentration ratio by a factor of 4.1 at an optical efficiency of 85.4%, reduces spillage loss from 78.9% to 32.1%, and reduces the flux non-uniformity on the target surface. [ABSTRACT FROM AUTHOR]

• Two-stage optics generate 50× geometric concentration on thermal absorber. • Experimentally operated at 650 °C receiver outlet with particulate HTF. • Prototype demonstrates 63% optical efficiency, 40% thermal efficiency at 650 °C. A two-stage high-concentration collector has been developed which pairs a 45° half rim angle parabolic trough with a secondary compound parabolic concentrator to achieve 50× concentration on the thermal absorber. An experimental prototype fabricated and installed at the University of California, Merced was tested on-sun up to 650 °C using a suspended particulate heat transfer fluid (HTF). The prototype collector demonstrated 63% optical efficiency and 40% thermal efficiency at 650 °C. This prototype demonstrates the feasibility of a two-stage linear trough collector at generating high flux and high absorber temperatures, and the ability of the particulate HTF to operate under these conditions. [ABSTRACT FROM AUTHOR]

Highlights • Spectrum splitting hybrid CSP/CPV collector designed, simulated, tested. • Double-junction InGaP/GaAs solar cells incorporated as spectral reflectors. • Hybrid collector developed into working prototype and experimentally tested. • Tested up to 600 °C using suspended solid particulate (alumina based) heat transfer fluid. Abstract A hybrid concentrating photovoltaic/concentrating solar power spectrum splitting collector has been designed, developed, and experimentally tested. The two-stage optical system pairs a parabolic trough with a compound parabolic concentrating secondary, generating 50X geometric concentration on the thermal absorber. Double-junction indium gallium phosphide/gallium arsenide solar cells integrated into the secondary reflector generate electricity from photons with energy greater than ∼1.4 eV and reflect the remaining lower energy infrared photons to the thermal absorber for optimal spectral utilization. Simulations predict an optical efficiency of 64%, thermal efficiency of 52% at 600 °C, and efficiency of the back-reflecting concentrating photovoltaic subsystem of 6%. The collector has been developed into a working prototype and tested on-sun up to 600 °C using suspended solid particulate (alumina based) heat transfer fluid. The prototype demonstrates an optical efficiency of 63% and a net solar-to-electric efficiency of the concentrating photovoltaic subsystem of 4%. Thermal efficiency is much lower in the prototype collector and the potential causes have been examined. Overall, this work demonstrates a two-stage collector design, the ability of back-reflecting solar cells to operate as spectrum splitting devices, and the feasibility of an internally circulated solid particulate heat transfer fluid which enables high temperature operation beyond what is currently achievable with existing heat transfer fluids. [ABSTRACT FROM AUTHOR]

Abstract We proposed a method for the design of a freeform lens for light emitting diode (LED) light source based on intensity distribution curve. The energy mapping rules are considered in this design. The freeform lens achieves the optical requirements of the element and the geometrical requirements of the surface continuity. The method simplifies the design process of the freedom surface to avoid the repetitive optimization design and increase the design efficiency. In this paper, the modeling and optical simulation of freeform lenses for LED light source with 45°and 30°intensity distribution curves are performed. The simulation results prove the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract A general and simple method for constructing a proportional source-target energy mapping in order to design a continuous freeform lens for an extended LED light source is proposed. This mapping has the characteristic that we can directly obtain the relationship between the angles of the emitted and incident rays in both the longitudinal and latitudinal directions. By applying this angular function in turn to the normal vector, the lighting situation on the target plane can be quickly determined. Simulation results motivate the proposal of a feedback optimization algorithm to compensate for the deterioration near the diagonal on the target surface caused by surface construction errors and the finite extent of a real source. Based on energy conservation theory and the edge-ray principle, the optimization algorithm is divided into three steps. Finally, the illumination effect on the irradiated surface is consistent with our expectations for an extended LED light source with dimensions of 4 mm × 4 mm. Simulation results show that the energy efficiency η of the freeform lens on the target surface is approximately 0.85 and that the uniformity exceeds 90%. We subsequently analyze the error tolerance of the designed freeform lens from two perspectives: translation and rotation. The minimum translational and rotational error tolerances are 0.3 mm 0.3 m m and 4°, respectively, and the rotational error tolerance around the z-axis are greater than those around the x- and y-axes. [ABSTRACT FROM AUTHOR]

An illumination design method that incorporates the entire 3-D geometry between the optical surface and target plane into the ray mapping calculation has been developed. The resulting mapping relationship is integrable along the specific contours of the optical surface instead of a 2-D plane. The method is capable of creating extremely high performance, off-axis designs (97% uniformity at 54-deg off-axis), and since it explicitly accounts for system geometry, appears to be easily generalizable. [ABSTRACT FROM AUTHOR]

A device for detecting the microorganisms in water with a freeform lens is developed. The main components of the device include a water channel, a light-emitting diode (LED) light source, and a freeform lens. The freeform lens which plays a key role in the device is designed with a predefined light intensity distribution using a double freeform surface design method. Different from the traditional methods, during the construction of the lens, the mapping is established by an incident-emergent angle relation. As an example, a model of the device is designed. Monte Carlo ray tracing simulations are implemented to verify optical performance of the device. Installation error analyses on the LED source are also conducted. The results demonstrate that the device can generate a uniform illumination pattern at the arbitrary depth of the water and is feasible for the microorganism detection in water. Additionally, the results also show that the lens can achieve the uniform illumination without the influence of the illumination distance. An optical efficiency greater than 82% is obtained for the designed model. [ABSTRACT FROM AUTHOR]

Different designs have been presented to achieve high concentration and uniformity for the concentrated photovoltaic (CPV) system. Most of the designs have issues of low efficiency in terms of irradiance uniformity. To this end, we present a design methodology to increase irradiance uniformity over solar cell. The system consists of an eight-fold Fresnel lens as a primary optical element (POE) and an optical lens, which consists of eight parts, as a secondary optical element (SOE). Sunlight is focused through the POE and then light is spread over cell through the SOE. In the design, maximum sunlight is passed over cell by minimizing losses. Results have shown that the proposed CPV design gives good irradiance uniformity. The concentration module based on this novel design is a promising option for the development of a cost-effective photovoltaic solar energy generation.

In this paper we propose a method realizes the uniform distribution of both correlated color temperature (CCT) and illumination on the target plane. A lens with a flat bottom surface and a freeform top surface is designed. The simulation run by optical software shows that the lens designed in the new method has a better uniformity of CCT than the lens designed in conventional method, and the uniformity of illumination and the efficiency of energy are also quite good. This lens is much easier and more economical to manufacture comparing the lenses with double freeform surfaces or the systems with several lenses which are also used to improve the uniformity of CCT distribution. [ABSTRACT FROM AUTHOR]

A two-stage high-concentration collector is designed which pairs a 45° half rim angle parabolic trough with a compound parabolic concentrator (CPC) secondary to achieve 50X concentration on the thermal absorber. An experimental prototype fabricated & installed at the University of California in Merced is tested on-sun up to 650 °C using a suspended particulate (alumina) heat transfer fluid (HTF). Early deformation of the secondary reflector was fixed by implementing a passive cooling technique. The prototype collector demonstrates 63% optical efficiency and 40% thermal efficiency at 650 °C and pathways towards improving both optical and thermal efficiency have been identified. Obstacles encountered during testing are discussed, which highlight the need for further investigation into the heat transfer mechanisms within the fluidized particulate stream. This prototype demonstrates the feasibility of the two-stage linear trough collector at generating high flux, high temperatures, and the ability of the particulate alumina HTF to operate under these conditions. [ABSTRACT FROM AUTHOR]

Abstract: Freeform optics constitutes a new technology that is currently driving substantial changes in illumination design. It liberates designers and engineers from restrictions of optical surface geometry, enabling them to achieve compact, lightweight, and efficient illumination systems with excellent optical performance. Freeform optics is currently used widely for both fundamental research and practical applications. This Review focuses on the design of freeform illumination optics, which is a key factor in advancing the development of illumination engineering. The design methods of freeform illumination optics can be divided into two groups: zero‐étendue algorithms based on ideal source assumption and design algorithms for extended light sources. The zero‐étendue algorithms include ray mapping method, Monge–Ampère equation method, and supporting quadric method. The algorithms for extended sources include illumination optimization, feedback design, and simultaneous multiple surfaces method. The characteristics and limitations of these design methods are illustrated and a summary of these methods with future outlooks is also given. [ABSTRACT FROM AUTHOR]

A thorough investigation into the efficiency and performance of off-axis, freeform illumination systems has been conducted, and a method for arriving at the optimal tilt is established for both reflective and refractive designs. The optimal tilt for refractive designs is determined by minimizing the total light lost due to Fresnel reflections across the lens, while the optimal tilt for reflective designs ensures the source is not obstructing the reflected ray bundle. For uncoated lenses, utilizing the proposed tilt can improve efficiency by more than 150%. [ABSTRACT FROM AUTHOR]

We present a method of transmitter lens design dedicated for light distribution shaping on a curved and asymmetric target. In this context, target is understood as a surface determined by hypothetical optical detectors locations. In the proposed method, ribbon-like surfaces of arbitrary shape are considered. The designed lens has the task to transform collimated and generally non-uniform input beam into desired irradiance distribution on such irregular targets. Desired irradiance is associated with space-dependant efficiency of power flow between the source and receivers distributed on the target surface. This unconventional nonimaging task is different from most illumination or beam shaping objectives, where constant or prescribed irradiance has to be produced on a flat target screen. The discussed optical challenge comes from the applications where single transmitter cooperates with multitude of receivers located in various positions in space and oriented in various directions. The proposed approach is not limited to optical networks, but can be applied in a variety of other applications where nonconventional irradiance distribution has to be engineered. The described method of lens design is based on geometrical optics, radiometry and ray mapping philosophy. Rays are processed as a vector field, each of them carrying a certain amount of power. Having the target surface shape and orientation of receivers distribution, the rays-surface crossings map is calculated. It corresponds to the output rays vector field, which is referred to the calculated input rays spatial distribution on the designed optical surface. The application of Snell’s law in a vector form allows one to obtain surface local normal vector and calculate lens profile. In the paper, we also present the case study dealing with exemplary optical network. The designed freeform lens is implemented in commercially available optical design software and irradiance three-dimensional spatial distribution is examined, showing perfect agreement with expectations. [ABSTRACT FROM AUTHOR]

A novel hybrid concentrating solar power/concentrating photovoltaic (CSP/CPV) collector is designed, simulated, and optimized for the purpose of power generation. The two-stage concentrator combines a primary parabolic trough with a secondary compound parabolic concentrator (CPC). Single junction Indium Gallium Phosphide (InGaP) and dual junction (InGaP)/Gallium Arsenide (GaAs) solar cells are examined as spectrally reflective beam splitting solar cells. The secondary CPC profile is optimized to guarantee geometric efficiency despite a non-continuous (i.e. segmented) profile and the final two-stage design achieves a geometric concentration ratio of 50× on the thermal absorber. Optical, thermal, and cell performance models are used to determine net electric production for different configurations of the hybrid collector and combined with cost estimates to calculate $/ W exergy and $/ W electric . The down-selected design incorporates dual junction InGaP/GaAs cells, achieves 40% solar-to-exergy efficiency and 23% solar-to electric-efficiency at 600 °C, with a thermal fraction of 73% and installs for an estimated $2.15/ W electric . [ABSTRACT FROM AUTHOR]

In light-emitting diode (LED) array illumination (e.g. LED backlighting), obtainment of high uniformity in the harsh condition of the large distance height ratio (DHR), extended source and near field is a key as well as challenging issue. In this study, we present a new reversing freeform lens design algorithm based on the illuminance distribution function (IDF) instead of the traditional light intensity distribution, which allows uniform LED illumination in the above mentioned harsh conditions. IDF of freeform lens can be obtained by the proposed mathematical method, considering the effects of large DHR, extended source and near field target at the same time. In order to prove the claims, a slim direct-lit LED backlighting with DHR equal to 4 is designed. In comparison with the traditional lenses, illuminance uniformity of LED backlighting with the new lens increases significantly from 0.45 to 0.84, and CV(RMSE) decreases dramatically from 0.24 to 0.03 in the harsh condition. Meanwhile, luminance uniformity of LED backlighting with the new lens is obtained as high as 0.92 at the condition of extended source and near field. This new method provides a practical and effective way to solve the problem of large DHR, extended source and near field for LED array illumination. [ABSTRACT FROM AUTHOR]

For high concentration ratio of the planar concentrator which is mainly used for photovoltaic or solar-thermal applications, the ray-leakage must be prevented during rays propagated in the lightguide. In this paper, the design of a ray-leakage-free discal solar concentrator is proposed which provides a high concentration ratio while acquiring a high optical efficiency. The design structure of the coupling structure is a straightforward hemisphere instead of complicated structure in other concentrators because the emergent rays from the hybrid collectors have any tilt angle, which prompts the ray-leakage-free propagating length can be raised greatly. A mathematical model between geometrical concentration ratio, reflection times and the corresponding parameters is established, where the corresponding parameters include the parabola coefficient, outermost collector width, collector height, the expanding angle and the collector quantity. Numerical simulation results show that more than 1200x geometrical concentration ratio of the proposed concentrator is achieved without any leakage from the lightguide. [ABSTRACT FROM AUTHOR]

We present a linear Fresnel lens design for light-emitting diode (LED) uniform illumination applications. The LED source is an array of LEDs. An array of collimating lens is applied to collimate output from the LED array. Two linear Fresnel lenses are used to redistribute the collimated beam along two dimensions in the illumination area. Collimating lens and linear Fresnel lens surfaces are calculated by geometrical optics and nonimaging optics. The collimated beam output from the collimating lens array is divided into many fragments. Each fragment is refracted by a segment of Fresnel lens and distributed over the illumination area, so that the total beam can be distributed to the illumination target uniformly. The simulation results show that this design has a compact structure, high optical efficiency of 82% and good uniformity of 76.9%. Some consideration of the energy savings and optical performance are discussed by comparison with other typical light sources. The results show that our proposed LED lighting system can reduce energy consumption five-times in comparison to using a conventional fluorescent lamp. Our research is a strong candidate for low cost, energy savings for indoor and outdoor lighting applications. [ABSTRACT FROM AUTHOR]

We present a freeform lens for application to light-emitting diodes (LED) road lighting. We propose a simple source-target luminous intensity mapping method based on Snell's law and geometric-optics analysis. We calculated different contours of cross-sections to construct a freeform lens with a smooth surface. The computer simulation results show that the lighting performance of a single freeform lens is not sufficient for road lighting. For the road lamp simulation, we adopted an oval arrangement of freeform lenses on a printed circuit board. In addition, we performed tolerance analysis to determine the tolerance limits of manufacturing and installation errors. A road lamp at a height of 12 m can create rectangular illumination with an area of 40 m × 12 m, 69.7% uniformity, and average illuminance of 24.6 lux. This lighting performance can fully comply with the urban road lighting design standard. [ABSTRACT FROM AUTHOR]