High Power Solid State Retrofit Lamp Thermal Characterization and Modeling

Thermal and thermo-mechanical modeling and characterization of solid state lightening (SSL) retrofit LED lamp are presented in this paper. Paramount importance is to design SSL lamps for reliability, in which thermal and thermo-mechanical aspects are key points. The main goal is to get a precise 3D thermal lamp model for further thermal optimization. Simulations are performed with ANSYS and CoventorWare software tools to compere different simulation approaches. Simulated thermal distribution has been validated with thermal measurement on a commercial 8W LED lamp. Materials parametric study has been carried out to discover problematic parts for heat transfer from power LEDs to ambient and future solutions are proposed. The objectives are to predict the thermal management by simulation of LED lamp, get more understanding in the effect of lamp shape and used materials in order to design more effective LED lamps and predict light quality, life time and reliability

Novel system for distributed energy generation from a small scale concentrated solar power

The present work describes the realization of a modular 1-3 kWe, 3-9 kWth micro Combined Heat and Power (m-CHP) system based on innovative Concentrated Solar Power (CSP) and Stirling engine technology. The cogeneration of energy at distributed level is one of leading argument in large part of energy policies related to renewable energy resources and systems. This CSP m-CHP will provide electrical power, heating and cooling for single and multiple domestic dwellings and other small buildings. The developed system integrates small-scale concentrator optics with moving and tracking components, solar absorbers in the form of evacuated tube collectors, a heat transfer fluid, a Stirling engine with generator, and heating and/or cooling systems; it incorporates them into buildings in an architecturally acceptable manner, with low visual impact. Some good results have already been achieved, while developments on several technology subcomponents will be finalized through first part of 2013. Two Cer.Met. have been modelled, realized and tested. The up scaled receiver, in form of Cer.Met. coating based on TiO2 - Nb, has been confirmed an absorptance of 0.94 and emittance of 0.1 (@350°C). A second Cer.Met. coating based on SiO2 - W has demonstrated an absorptance of 0.93 and emittance of 0.09 (@350°C). A full-evacuated solar tube has been designed and realized, with absorber of 12 mm in diameter and length in 2 meters. The system is provided of a concentration ratio 12:1, and a single module is 200 cm long, 40 cm wide and 20-25 cm high. Two or more modules can be combined. The evacuated solar tube, located on the focus, has the selective absorber on a tube of 12 mm in diameter. A very thin glass mirror has been developed (< 1 mm). The overall mirror reflectivity has been measured, the verified value is 0,954. Research has proposed a high energy density, double acting Stirling engine, provided of innovative heat exchangers realized through Selective Laser Melting process. The engine is a low speed (250 RPM), high pressure (130 Bars) and compact solution able to be run at 300°C and generate 3,5 kW nominal power. The solar technology has actually entered the proof-of-concept stage. A solar plant has been installed in Malta, by Arrow Pharm company, supplying the industrial process of generated steam at 180°C and 3.5 absolute pressure. The solar collector's efficiency is close to 47% in presence of 900 W/m2 of direct solar radiation. During 2013, solar evacuated tubes with innovative Cer.Met. coating, together with new thin glass mirrors will upgrade the demonstration site, together with a new and innovative low temperature difference and high energy density Stirling. By end-2013, the system will be demonstrated, with the overall objective to achieve a minimum of 65% in solar collectors' efficiency at 300°C, and 12 - 15% of overall electrical efficiency by the Stirling cycle.peer-reviewe

Electrical, thermal and optical characterization of power LED assemblies

Besides their electrical properties the optical parameters of LEDs also depend on junction temperature. For this reason thermal characterization and thermal management play important role in case of power LEDs, necessitating both physical measurements and simulation tools. The focus of this paper is a combined electrical, thermal and optical characterization of power LED assemblies. In terms of simulation a method for board-level electro-thermal simulation is presented, for measurements a combined thermal and radiometric characterization system of power LEDs and LED assemblies is discussed. Comparison of measurement and simulation results is presented in a case study.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

MIMO Underwater Visible Light Communications: Comprehensive Channel Study, Performance Analysis, and Multiple-Symbol Detection

In this paper, we analytically study the bit error rate (BER) performance of underwater visible light communication (UVLC) systems with binary pulse position modulation (BPPM). We simulate the channel fading-free impulse response (FFIR) based on Monte Carlo numerical method to take into account the absorption and scattering effects. Additionally, to characterize turbulence effects, we multiply the aforementioned FFIR by a fading coefficient which for weak oceanic turbulence can be modeled as a lognormal random variable (RV). Moreover, to mitigate turbulence effects, we employ multiple transmitters and/or receivers, i.e., spatial diversity technique over UVLC links. Closed-form expressions for the system BER are provided, when equal gain combiner (EGC) is employed at the receiver side, thanks to Gauss-Hermite quadrature formula and approximation to the sum of lognormal RVs. We further apply saddle-point approximation, an accurate photon-counting-based method, to evaluate the system BER in the presence of shot noise. Both laser-based collimated and light emitting diode (LED)-based diffusive links are investigated. Since multiple-scattering effect of UVLC channels on the propagating photons causes considerable inter-symbol interference (ISI), especially for diffusive channels, we also obtain the optimum multiple-symbol detection (MSD) algorithm to significantly alleviate ISI effects and improve the system performance. Our numerical analysis indicates good matches between the analytical and photon-counting results implying the negligibility of signal-dependent shot noise, and also between analytical results and numerical simulations confirming the accuracy of our derived closed-form expressions for the system BER. Besides, our results show that spatial diversity significantly mitigates fading impairments while MSD considerably alleviates ISI deteriorations

The Boston University Photonics Center annual report 2016-2017

This repository item contains an annual report that summarizes activities of the Boston University Photonics Center in the 2016-2017 academic year. The report provides quantitative and descriptive information regarding photonics programs in education, interdisciplinary research, business innovation, and technology development. The Boston University Photonics Center (BUPC) is an interdisciplinary hub for education, research, scholarship, innovation, and technology development associated with practical uses of light.This has undoubtedly been the Photonics Center’s best year since I became Director 10 years ago. In the following pages, you will see highlights of the Center’s activities in the past year, including more than 100 notable scholarly publications in the leading journals in our field, and the attraction of more than 22 million dollars in new research grants/contracts. Last year I had the honor to lead an international search for the first recipient of the Moustakas Endowed Professorship in Optics and Photonics, in collaboration with ECE Department Chair Clem Karl. This professorship honors the Center’s most impactful scholar and one of the Center’s founding visionaries, Professor Theodore Moustakas. We are delighted to haveawarded this professorship to Professor Ji-Xin Cheng, who joined our faculty this year.The past year also marked the launch of Boston University’s Neurophotonics Center, which will be allied closely with the Photonics Center. Leading that Center will be a distinguished new faculty member, Professor David Boas. David and I are together leading a new Neurophotonics NSF Research Traineeship Program that will provide $3M to promote graduate traineeships in this emerging new field. We had a busy summer hosting NSF Sites for Research Experiences for Undergraduates, Research Experiences for Teachers, and the BU Student Satellite Program. As a community, we emphasized the theme of “Optics of Cancer Imaging” at our annual symposium, hosted by Darren Roblyer. We entered a five-year second phase of NSF funding in our Industry/University Collaborative Research Center on Biophotonic Sensors and Systems, which has become the centerpiece of our translational biophotonics program. That I/UCRC continues to focus on advancing the health care and medical device industries

Characterization, Modeling and Analysis of Organic Light-Emitting Diodes With Different Structures

This paper demonstrates that organic light-emitting diodes (OLED) of different structures can characterized and modeled using a combination of the photo-electro-thermal (PET) theory and spectral power distribution modeling. The photometric, electrical, thermal and chromatic properties of OLED devices are incorporated into a model framework so that the performance of OLED of different structures can be compared. A concept of luminance uniformity over the OLED surfaces is also introduced for comparing OLED with large surface areas. Experimental results are included to verify the OLED models and compare the characteristics of two different OLED samples. Based on the same PET framework, some differences of OLEDs and inorganic LEDs are addressed and discussed.published_or_final_versio

Ion-Exchanged Glass Waveguide Technology: A Review

We review the history and current status of ion exchanged glass waveguide technology. The background of ion exchange in glass and key developments in the first years of research are briefly described. An overview of fabrication, characterization and modeling of waveguides is given and the most important waveguide devices and their applications are discussed. Ion exchanged waveguide technology has served as an available platform for studies of general waveguide properties, integrated optics structures and devices, as well as applications. It is also a commercial fabrication technology for both passive and active waveguide components

Electricity from photovoltaic solar cells: Flat-Plate Solar Array Project final report. Volume VII: Module encapsulation

The Flat-Plate Solar Array (FSA) Project, funded by the U.S. Government and managed by the Jet Propulsion Laboratory, was formed in 1975 to develop the module/array technology needed to attain widespread terrestrial use of photovoltaics by 1985. To accomplish this, the FSA Project established and managed an Industry, University, and Federal Government Team to perform the needed research and development. The objective of the Encapsulation Task was to develop, demonstrate, and qualify photovoltaic (PV) module encapsulation systems that would provide 20-year (later increased to 30-year) life expectancies in terrestrial environments, and which would be compatible with the cost and performance goals of the FSA Project. The scope of the Encapsulation Task included the identification, development, and evaluation of material systems and configurations required to support and protect the optically and electrically active solar cell circuit components in the PV module operating environment. Encapsulation material technologies summarized in this report include the development of low-cost ultraviolet protection techniques, stable low-cost pottants, soiling resistant coatings, electrical isolation criteria, processes for optimum interface bonding, and analytical and experimental tools for evaluating the long-term durability and structural adequacy of encapsulated modules. Field testing, accelerated stress testing, and design studies have demonstrated that encapsulation materials, processes, and configurations are available that will meet the FSA cost and performance goals. Thirty-year module life expectancies are anticipated based on accelerated stress testing results and on extrapolation of real-time field exposures in excess of 9 years