Technical Papers

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Fresnel lens solar concentrator derivations and simulations

Arthur Davis
August 2011
Novel Optical Systems Design and Optimization XIV, edited by R. John Koshel, G. Groot Gregory, Proc. of SPIE Vol. 8129, 81290J, (2011). Copyright 2011 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. http://dx.doi.org/10.1117/12.892818

Available Formats: (technical paper)

Abstract: Fresnel lens solar concentrators continue to fulfill a market requirement as a system component in high volume cost effective Concentrating Photovoltaic (CPV) electricity generation. Design and optimization may be performed using comprehensive system simulation tools, but before investing in the effort to build a complete virtual model framework, much insight can be gathered beforehand by generating a parameterized simulation cache and referencing those results.

To investigate the performance space of the Fresnel lens, a fast simulation method which is a hybrid between raytracing and analytical computation is employed to generate a cache of simulation data. This data is post-processed to yield results that are not readily achieved via derivation. Example plots that can be used for look-up purposes will be included.

Lens parameters that will be interrogated include focal length, index of refraction, prism fidelity, aperture, transmission and concentration ratio. In order to compactly represent a large variety of lens configurations, some variables that define the Fresnel lens will be parameterized.

Analysis will be limited to Fresnel lens prisms oriented toward the photovoltaic (PV) cell and the plano surface directed toward the sun. The reverse of this configuration is rarely encountered in solar concentration applications and is omitted.

Prism peak rounding in injection molded Fresnel lens solar concentrators

Arthur Davis, Kevin Levesque, Scot Wilt
May 2011
SPIE Optifab 2011

Available Formats: (summary)

Abstract: The construction of viable solar energy conversion facilities is dominantly driven by economic forces requiring the minimization of cost per unit of electrical energy (e.g. dollars per Watt). As such, high volume injection molded Fresnel lenses are a contending technology in concentrated photovoltaic (CPV) systems.

Injection molding of Fresnel lenses for CPV systems requires particularly sophisticated technology and process control. Innumerable factors affect the quality. One important metric which has a direct impact on concentrator performance and must be controlled in the molding environment is prism facet fidelity. For maximum performance, the tips of the peaks in the finished component should be as sharp as possible. When prism peaks are not perfectly sharp, this is called “peak rounding” and the metric for this is the “peak radius”.

The effect of peak rounding on the performance of Fresnel lens solar concentrators is investigated. A reasonable analytical model is presented. Also, this paper will review the process and production optimization on the inherent PVT (pressure, volume, temperature) relationship of the polymer that must be obeyed in the molding process. Finally, manufacturing data is presented as an example of the excellent quality level that can be achieved in an advanced high volume injection molding process.

Reliabilty of SOG for CPV Primary Optics

Edward Philips, Steve Scott, Stefan Gaebler, Maik Jacob, Juergen Zosel, Martin Bitzer
February 2011
National Renwable Energy Laboratory (NREL), 2011 PV Module Reliability Workshop: http://www.nrel.gov/pv/pvmrw.html

Available Formats: (poster)

Abstract: Silicone on Glass offers outstanding long term performance in commonly used accelerated tests. Its high initial energy transmission is nearly retained after 7500h of XWOM radiation. At the same time no relevant mechanical or chemical degradation such as yellowing, cracking and delamination could be observed. Although testing results cannot yet be correlated directly to lifetime in the field, the testing results create a strong confidence in the long term reliability of SOG primary optics.

Raytrace assisted analytical formulation of Fresnel lens transmission efficiency

Arthur Davis
August 2009
Novel Optical Systems Design and Optimization XII, edited by R. John Koshel, G. Groot Gregory, Proc. SPIE Vol. 7429, 74290D, (2009). Copyright 2009 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. http://dx.doi.org/10.1117/12.823742

Available Formats: (technical paper)

Abstract: In consideration of the broad range of possible Fresnel lens applications, it is desirable to find a fast way of approximating optical performance that is not specific to a particular lens geometry. This is potentially useful for gaining deeper insight into a lens system and affording accelerated development times.

Additionally, a Fresnel lens manufactured using a molded polymer process has limitations on how accurately it can replicate a microstructured prismatic pattern. This is especially true at the prismatic peaks of the part where it is more difficult to completely “fill-out” the moldbase. Inclusion of this effect in performance evaluation is important.

Using transmission efficiency (or transmittance) as the metric, a Fresnel lens model which includes imperfect peak replication is sought. The system description will be parameterized so that the formulations are not specific to a particular geometry and can be generally applied. The parameter space will be explored with raytracing and the results compiled for convenient reference.

Optical Design using Fresnel Lenses

Arthur Davis & Frank Kühnlenz
December 2007

Available Formats: (technical paper)

Abstract: The fresnel lens can be used in a wide variety of applications. The basic principles of the fresnel lens are reviewed and some practical examples are described. There are definite advantages and tradeoffs that should be considered when deciding if a fresnel lens is the appropriate component to use in a design. Some basic optimization rules are presented which may facilitate a first order design or feasibility study.

Large Area Microstructured Optic Applications

Steve Scott
October 2004

Available Formats: (technical paper)

Abstract: Applications where microstructured optics components are required over large areas are increasing. This paper describes optical microstructures, their applications, and the challenges involved in mastering, replicating, and production of these microstructures over large areas.

Light Emitting Diode Source Modeling for Optical Design

Arthur Davis
October 2004

Available Formats: (presentation)

Abstract: Presentation slides from short course describing the fundamentals of LED source modeling. Topics covered include Photometry, LED Specification, LED Optics, Source Approximation and Fresnel Lenses.

Microstructured Optics for LED Applications

Arthur Davis
October 2002

Available Formats: (paper)

Abstract: Optics for use with Light Emitting Diodes are described. Microstructured optics are available and customizable for a wide variety of applications. A few of these will be touched on. A methodology of designing these optics and the photometrics of the typical technology is overviewed.

Fresnel Lenses in Rear Projection Displays

Arthur Davis, Robert C. Bush, John C. Harvey & Michael F. Foley
June 2001

Available Formats: (technical paper)

Abstract: A plastic Fresnel lens positioned just before the diffusion screen in a projection system can provide significantly superior corner illumination, enhancing overall display luminance uniformity. Fresnel lenses are also used within the light engine to collimate light through the LCD panel and focus light through the projection lens. Disadvantages include the added cost of the lenses, ghosting, printout of the Fresnel rings and moiré patterns. Birefringence is important to control polarization-sensitive applications.

Without reduction of ghosting artifacts, Fresnel lenses will have limited application in text-based RP systems. Ghosting is described in some detail including how it is caused, quantified and reduced. Efforts to reduce cost and birefringence will all be discussed.

Microstructured Optical Components for Waveguide-based Luminaires

Michael F. Foley
May 2001

Available Formats: (technical paper)

Abstract: Precision microstructured optical components made from polymers are the enabling technology in a new generation of office lighting designed to reduce eyestrain for computer users. New products which utilize waveguide technology and precision microprisms are now available which manage light from Luminaires powered by high output T5 lamps. The optical system design can be optimized to control glare in office lighting, while maintaining exceptional photometrics and aesthetics. Design considerations such as efficiency, proportion of uplight versus downlight, and cutoff angles will be discussed and quantified. Manufacturing challenges such as tight tolerances and component and system cost will be detailed. Photometric output (analytical models from TracePro and empirical data from a goniophotometer) will be presented. Reduction to practice and examples drawn from the successful market introduction of the technology will be discussed. Next generation designs, which feature similar performance at a lower price point, will also be revealed. This revolutionary optical technology is changing the way lighting designers approach luminaire design in applications which demand glare control and specified photometrics.

Rear Projection Screens for Different Applications

Robert C. Bush
October 2000

Available Formats: (technical paper)

Abstract: Fresnel Optics has been awarded a development contract with the United States Display Consortium (USDC) to produce rear projection screens and Fresnel lenses to be used in Rear Projection Monitors. The USDC program is broken into two sections: production of 2 different prototype screens using customer input; and large volume production. Screens up to 32 inch diagonal will be developed as part of the USDC program.

The distinctive requirements of projection monitors demand unique screens that have different technical specifications from screens used in rear-projection televisions. Specifications of the screens being designed include: Viewing Angles, Contrast, Speckle Contrast, Gain, Color Shift, Resolution, Luminance, Uniformity and Display Artifacts. How these specifications interact with the projection engine will be discussed. Fresnel lenses are used in most rear projection systems. The attributes of using a Fresnel lens in this application will also be discussed. Preliminary screen specifications will be presented.

Polymer Fly's Eye Light Integrator Lens Arrays for Digital Projectors

Michael F. Foley & James Munro
May 2000

Available Formats: (technical paper)

Abstract: Polymer Fly's Eye light integrators are now available as an alternative to glass. While the appropriate material is highly dependent on the specifics of the applications, plastic integrators offer measurable advantages in certain situations. Key design considerations include weight, performance, cost, birefringence, and temperature resistance. This paper explores each of these design considerations, and presents some guidelines to aid optical engineers in material selection.

Technical Advances in Microstructured Optics for Display Applications

Michael F. Foley
May 1999

Available Formats: (technical paper)

Abstract: This paper will present recent technological advances in the field of replicated, microstructured plastic optics, and their applications in display optics. A number of technology areas will be discussed, including moth-eye Antireflective Microstructure™, High Precision Molding (HPM), high temperature polymers, and one-piece, diffusive imaging screens. Applications discussed will include field lenses, condenser lenses, microlens arrays, and light integrators for LCD Projection systems, specialized optics for microdisplay applications, and imaging screens for photographic and rear projection systems.

Manufacturing Methods for Large Microstructured Optical Components for Non-Imaging Applications

John R. Egger
October 1995

Available Formats: (technical paper)

Abstract: Various methods of manufacturing are reviewed for large area (6 inch diameter and greater) microstructured optical components (MOC's) that are used for light management in non-imaging applications. All of the manufacturing methods discussed will relate to the processing of various optical grade polymers. This paper will start with a review of the traditional methods used to make plastic Fresnel lenses over the past forty or more years. The evolution of precision compression molding will be analyzed. Quality / cost trade-offs of the various methods currently used to produce large-area, thin cross-section, microstructured optical components will be discussed. Examples of products made by compression molding, transfer molding, hot stamping, thermal and UV casting and other various processing methods will be discussed. The paper will conclude with a look into the future. Where is non-traditional, non-glass optical component manufacturing technology headed?