Characterization of Acoustic Resonance in a High Pressure Sodium Lamp

With the last decades, the high pressure sodium (HPS) lamp has been supplied in high frequency in order to increase the efficacy of the lamp/ballast system. However, at some given frequencies, standing acoustic waves, namely acoustic resonance (AR), might develop in the burner and cause lamp luminous fluctuation, extinction and destruction in the most serious case. As we seek for a control method to detect and avoid the lamp AR some main characteristics of the acoustic resonances in a 150W HPS lamp are presented in this paper,. The first one is the characteristic of the lamp AR threshold power, the second one is the differences between forward and backward frequency scanning effects during lamp open loop operation. Thirdly, lamp AR behaviour in closed loop operation with an LCC half bridge inverter will be presented and leads to a new point of view and a change in the choice of the AR detection method. These characteristics allow us to further understand the AR and to better control the lamp

2014 Status Report on Organic Light Emitting Diodes (OLED)

Organic light emitting diodes (OLED) are promising candidates for general illumination, since they offer the possibility to realize large area light sources which can even be transparent and flexible. The energy-saving potential of OLEDs is similar to that of LEDs, but the two technologies differ in a number of ways. The present report introduces the basics of the OLED technologies and its latest developments. It also describe the emerging markets, industry landscape and standardisation requirementsJRC.F.7-Renewables and Energy Efficienc

2014 Update on the Status of LED market

Light-emitting diodes (LEDs), a type of solid-state lighting (SSL), are revolutionizing the lighting market. In just the last few years, LED performance has accelerated quickly and a wave of new commercial, industrial and institutional LED fixtures has been introduced. LED technology is fulfilling its promise of offering the market the most efficient means of converting electrons into photons.. The present report contains information on the latest technological developments concerning LED lighting. The report covers also in details the latest development in the LED markets in Europe and other key countries.JRC.F.7-Renewables and Energy Efficienc

Accelerating the deployment of Solid State Lighting (SSL) in Europe

Solid State Lighting, in particular the use of LEDs and OLEDs for general lighting, is a promising technology with high growth potential in Europe. The path for the development of SSL in Europe is sketched out in the Green Paper on SSL of the European Commission. The current study supports the direction taken in the green paper towards deployment of SSL. This paper sketches the lighting consumptions and various applications of SSL, from fully-mature applications till the general lighting sector when mass adoption is expected from 2015, first in the retrofit market then in the new lighting fixtures and luminaires. It focuses on the strengths and weaknesses of the European market for SSL. Distinction can be made between the outdoor lighting sector, where LEDs are more present, and indoor lighting, where the growth rate is still low. The LED industry is rather fragmented. It is usually divided into five segments: materials, equipment, finished lamps and components, luminaires and systems, and finally lighting services and solutions. One of the vulnerability areas is the fact Europe is dependent from China for a variety of semiconductor materials, including various rare earth elements (REE), that are used in the production of LEDs. The European manufacturing base is strong in the downstream segments of the value chain close to the application (40%) but it is weaker in the upstream segments (LED packaging, chips, wafers). Product design and marketing and sales are managed in Europe whereas product manufacturing takes place in Asia. R&D takes place mainly in Japan, the US and Europe. Through patent cross-licensing however the research base becomes broader, including China, Taiwan and South Korea. Europe is suffering from fragmented funding. Asian countries have a high budget for R&D. LED commercialisation channels might face a reshuffle, in particular when the industry will be moving to lighting services. For LEDs to penetrate the market more, end-user information and training, as well as training for installers, would be necessary. LED is still a costly product, in particular in the general lighting segment where alternatives remain cheaper. The price needed for mass adoption has not yet been reached. It is estimated that a price of $8 would allow a 25% market share for LEDs. In Europe, a price of €10 would allow to reach, after some time, a 50% market share for LEDs versus 50% for CFLs in the residential sector. It is to be noted that the price for LED bulbs differs from one country to another, e.g. LED bulbs are cheaper in Japan than they are in the US or Europe. Despite the potential of SSL for energy efficiency and also better lighting, many obstacles to its development remain. Cost and consequently payback time are not yet in the advantage of LED-based general illumination, compared to conventional lighting technologies. Quality is an issue, particularly in the absence of standards, both for testing and for final products. Luminous efficacy and lifetime can still be improved. Last but not least, educational barriers remain, that could be overcome by training of all players in the market, from the designer to the user. As far as the environment is concerned, LEDs do not contain mercury. Life cycle analysis seems to be quite favourable for SSL but further research into environment and health benefits will be required to confirm this. Some of the obstacles to mass adoption in the general lighting segment will disappear as technology evolves to cheaper products with better light quality. But price and energy efficiency might not be the only selling elements for LEDs. Innovation might be an important asset when designing new lighting products. Further legislation and policy initiatives addressing SSL will need to be designed in such a way to reinforce Europe's strategic strengths in the lighting sector, as proposed in the Green paper on SSL of the European Commission.JRC.F.7-Renewable Energ

Journal of Solid State Lighting

International audienc

Photostability of β-carotene/modified kaolinite

β-carotene (BC), a natural organic compound, is very highly sensitive to light. The stability of BC can be improved by various methods. The aim of this study was to propose a simple method for improving the photostability of BC with modified kaolinite (MK). MK was produced by kaolin modification, through calcination and interaction with ZnCl2. The characteristics of the MK were determined by using scanning electron microscope–energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), infrared spectroscopy (IR), and surface area analyzer. The photostability of BC was measured with a UV-spectrophotometer. The XRD patterns of the kaolinite showed layer disruption during calcination at 600°C, leading to metakaolinite production. Surface area analysis and IR-spectroscopy revealed an increase in mean pore volume in the MK and a shift of the signal for the –OH group, respectively. MK decreased the photodegradation of BC, and increased the half-life of this molecule by almost 15-fold than the only BC 1.44 h. The amount of BC photostabilized by MK expressed as percentage of photostability, at five hours it was 61.87%. The amount of BC adsorbed onto the kaolinite was related to the photostability of BC

High Power Discharge Lamps and Their Photochemical Applications: An Evaluation of Pulsed Radiation

International audienc

Acoustic Resonance Characterization and Numerical Model Including Acoustic Streaming in an HPS Lamp

This paper presents a numerical model of High Pressure Sodium (HPS) lamps including the acoustic streaming. The model is implemented in COMSOL and based on the finite elements method using a 2D axi-symmetric geometry. Moreover, a revision concerning AR experimental characterizations of HPS lamps will also be provided. The results presented in this paper will contribute to the understanding of AR phenomena and help in the electronic ballast design methods for AR avoidance

OLED ageing signature characterization under combined thermal and electrical stresses

OLED are appearing at the industrial scale for purposes such as decorative lighting as well as LCD screen back-lighting. One of their main advantages compared to LED is their reduced light intensity: the luminous flux is produced by a much greater surface. Nevertheless there are a number of strong constraints on their allowable operating conditions, which may otherwise dramatically reduce their lifetime. This aspect of OLEDs is up to now not well understood and generally requires the knowledge of the layers and the chemical compounds used to build the device. In this study we submitted commercial OLEDs to limit conditions with respect to their maximum current and temperature. Complete electrical, optical, photometric and thermic characterization was performed on new devices, and repeated at regular intervals during the ageing process. Electrical parameters were measured with a Solartron impedance analyzer and a Keithley Source meter applying current and voltage steps. By the analysis of the indicial response elements of the equivalent linear circuit were extracted. We will illustrate which parameters change the most with the ageing process. The purpose is to predict and quantify the useful lifetime of OLED under electrical and/or thermal stress. Another outcome of importance is related to OLED driver design, namely specifying the end-of-life electrical characteristics. The operating point's significantly drifted from their original values leading sometimes to a doubling of the operating voltage at the same current level

Estimation of the light output power and efficiency of a XeCl dielectric barrier discharge exciplex lamp using one dimensional drift-diffusion model for various voltage waveforms

A XeCl dielectric barrier discharge (DBD) excilamp applied by pulsed and sinusoidal voltage waveforms is simulated using a 1-D drift–diffusion model. In both waveforms, the light output power depends not only on the gas mixture composition but also on the electrical parameters of each voltage waveform such as the frequency, the duty cycle, etc. At the same amplitude of the applied voltage and frequency, the light ultraviolet output efficiency of a pulsed voltage is higher than that of a sine voltage. These results obtained in this paper permit us to find out an appropriate power supply for a DBD excilamp