Search query: possibility of thermal energy recycling based light emitting diodes grid system

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abstract: Light Emitting Diodes (LED) are highly energy efficient and offer long life times for display applications. Long life and minimal energy consumption are often the most attractive advantages for electronic devices. Because LEDs are based on compound semiconductors, which explore the direct transition between the conduction and valance band edges, thermal energy loss can be minimized during operation. However, even though these types of LEDs are based on direct transition type semiconductors, thermal energy is still emitted during operation owing to forward conduction and reverse leakage currents. This research proposes capturing this energy loss through thermoelectric module based energy recycling methods to improve the energy efficiency of LED applications, achieving savings of up to 18% Additional analysis was performed on high power LED sources resulting in the manufacture of a high power LED light grid system.
author_names: Jae-Hoon Ji

Jinhwan Kim

Gaehun Jo

Min-Young Park

Jihye Kang

Masao Kamiko

J G Ha

S M Koo

Junhee Hong

Jung-Hyuk Koh
title: Possibility of Thermal Energy Recycling Based Light Emitting Diodes Grid System.
venue: Journal of nanoscience and nanotechnology
year: 2020

abstract: In this study, emitted light energy and the recycling of thermal energy from the arrays of a light emitting diode system were investigated. A light grid system is composed of the array of high power LED chips, thermoelement and heat sink. High power LED source has an advantage of high luminous efficiency, which combined with wasted thermal energy. Thermal energy loss can be regarded wasted energy. However, this wasting thermal energy can be effectively converted to the electrical energy from thermoelement and heat sink of a light grid system. By introducing the light grid system, the optical energy and thermal energy can be more effectively managed. In particular, we have intensively studied energy conversion efficiency of light grid system and energy harvesting characteristic through thermal energy.
author_names: Jae-Hoon Ji

Gaehun Jo

Junhee Hong

Jung-Hyuk Koh
title: Energy Harvesting Through Wasted Thermal Energy by Light Grid Sources.
venue: Journal of nanoscience and nanotechnology
year: 2019

abstract: The advantages of light emitting diodes (LEDs) over previous light sources and their continuous spread in lighting applications is now indisputable. Still, proper modelling of their lifespan offers additional design possibilities, enhanced reliability, and additional energy saving opportunities. Accurate and rapid multi physics system level simulations could be performed in Spice compatible environments, revealing the optical, electrical and even the thermal operating parameters, provided, that the compact thermal model of the prevailing luminaire and the appropriate elapsed lifetime dependent multi domain models of the applied LEDs are available. The work described in this article takes steps in this direction in by extending an existing multi domain LED model in order to simulate the major effect of the elapsed operating time of LEDs used. Our approach is based on the LM 80 08 testing method, supplemented by additional specific thermal measurements. A detailed description of the TM 21 11 type extrapolation method is provided in this paper along with an extensive overview of the possible aging models that could be used for practice oriented LED lifetime estimations.
author_names: Janos Hegedus

Gusztav Hantos

Andras Poppe
title: Lifetime Modelling Issues of Power Light Emitting Diodes
year: 2020

abstract: Industrial scale catalytic chemical synthesis demands both high reaction rates and high product yields. In exothermic chemical reactions, these conflicting objectives require a complex balance of optimized catalysts, high temperatures, high pressures, and multiple recycling steps, as in the energy intensive Haber Bosch process for ammonia synthesis. Here we report that illumination of a conventional ruthenium based catalyst produces ammonia with high reaction rates and high conversion yields. Indeed, using continuous wave light emitting diodes that simulate concentrated solar illumination, ammonia is copiously produced without any external heating or elevated pressures. The possibility of nonthermal plasmonic effects are excluded by carefully comparing the catalytic activity under direct and indirect illumination. Instead, thermal gradients, created and controlled by photothermal heating of the illuminated catalyst surface, are shown to be responsible for the high reaction rates and conversion yields. This nonisothermal environment enhances both by balancing the conflicting requirements of kinetics and thermodynamics, heralding the use of optically controlled thermal gradients as a universal, scalable strategy for the catalysis of many exothermic chemical reactions.
author_names: Xueqian Li

Xiao Zhang

Henry O Everitt

Jie Liu
title: Light Induced Thermal Gradients in Ruthenium Catalysts Significantly Enhance Ammonia Production.
venue: Nano letters
year: 2019

abstract: An LED cooling system that uses a micro tube water cooling device is studied experimentally and a heat transfer model that uses a finite element method is numerically analyzed. In this experiment, the micro screw tube system achieves better thermal management and the heat created by the LEDs is effectively dissipated. It is experimentally found that the effect of thermal dissipation occurs by recycling water in the LEDs' light assemblies are in reasonable agreement. Introduction High power light emitting diodes (LEDs) which depend on the semiconductor material to emit the light have been extensively studied in recent years. LEDs with greatly improved energy efficiency are used not only as low energy indicators, but also as replacements for traditional light sources, in general lighting and automotive lighting [1 3] Recently, numerous reports have concerned heat removal from LEDs to allow better LED thermal management, especially with reference to package configuration and the materials used for substrates and heat sinks. There have been trials with an ultra bright LED module, a LED based spot module, multi walled carbon nanotubes, interface thermal materials, carbon black and a piezoelectric fan, as well as a thermal resistance model [4 6] To further investigate an effective cooling system and obtain optimum cooling performance in a LED array system, the natural convection in such a system requires special consideration, and a numerical model is considered. In this study, a cooling system with a micro screw tube and LED arrays uses red, green and blue LED in the white LED source. A new heat cooling system that uses a micro screw tube water cooling device is considered and finite element analysis (FEM) is implemented to solve the problem of thermal management in high power LED lighting experiments and to determine the ideal spectral power distribution of white LED lamps, in order to improve the color. This study also determines the feasibility of a micro tube water cooling system, using FEM algorithms for the thermal management of high power LED's.
author_names: Ming-der Jean

Guofu Lian
title: Prediction and Thermal Management Analysis of LED Light Assemblies Using Finite Element Method
year: 2017

abstract: Organic light emitting diodes (OLEDs) have been the focus of intense study since the late 1980s, when the low voltage organic electroluminescence in small organic molecules such as Alq3, and large organic molecules such as polymers (PPV) was reported. Since that time, research has continued to demonstrate the potential of OLEDs as viable systems for displays and eco friendly lighting applications. OLEDs offer full colour display, reduced manufacturing cost, larger viewing angle, more flexible, lower power consumption, better contrast, slimmer, etc. which help in replacing the other technologies such as LCD. The operation of OLEDs involves injection of charge carriers into organic semiconducting layers, recombination of charge carriers, formation of singlet and triplet excitons, and emission of light during decay of excitons. The maximum internal quantum efficiency of fluorescent OLEDs consisting of the emissive layer of fluorescent organic material is 25% because in this case only the 25% singlet excitons can emit light. The maximum internal quantum efficiency of phosphorescent OLEDs consisting of the emissive layer of fluorescent organic material mixed with phosphorescent material of heavy metal complexes such as platinum complexes, iridium complexes, etc. is nearly 100% because in this case both the 25% singlet excitons and 75% triplet excitons emit light. Recently, a new class of OLEDs based on thermally activated delayed fluorescence (TADF) has been reported, in which the energy gap between the singlet and triplet excited states is minimized by design, thereby promoting highly efficient spin up conversion from non radiative triplet states to radiative singlet states while maintaining high radiative decay rates of more than 106 decays per second. These molecules harness both singlet and triplet excitons for light emission through fluorescence decay channels and provides an intrinsic fluorescence efficiency in excess of 90 per cent and a very high external electroluminescence efficiency of more than 19 per cent, which is comparable to that achieved in high efficiency phosphorescence based OLEDs.The OLED technology can be used to make screens large enough for laptop, cell phones, desktop computers, televisions, etc. OLED materials could someday be applied to plastic and other materials to create wall size video panels, roll up screens for laptops, automotive displays, and even head wearable displays. Presently, the OLEDs are opening up completely new design possibilities for lighting in the world of tomorrow whereby the offices and living rooms could be illuminated by lighting panels on the ceiling. The present paper describes the salient features of OLEDs and discusses the applications of OLEDs in displays and solid state lighting devices. Finally, the challenges in the field of OLEDs are explored. Contents of Paper
author_names: Vivek Kumar Chandra

Belani P Chandra

Piyush Jha
title: Organic Light Emitting Diodes and their Applications
year: 2014

abstract: Abstract Nocturnal lighting systems account for 20% of the total global electricity consumption. The aim of this paper is to investigate and compare the following two street lighting technologies in Lebanon from an environmental perspective: i) traditional grid connected system and ii) solar stand alone system. Life Cycle Assessment (LCA) is the methodology used to assess and compare the potential environmental impacts of the two systems from cradle to grave, i.e. from the raw material extraction until the end of life product stages. Two end of life scenarios are modeled: landfilling and recycling. The SimaPro software is used for modeling the Life Cycle Inventory and the IMPACT 2002 method is used for the Life Cycle Impact Assessment. The traditional system includes a steel pole, a High Pressure Sodium lamp, and aluminum cables. The stand alone solar system includes a steel pole, a Light Emitting Diode lamp, a photovoltaic panel, a valve regulated acid battery, a controller, a dimmer, and copper cables. Results show that the traditional system has less environmental impacts than the solar stand alone system when considering the life cycle stages from the raw material extraction to the production phase only. This is mainly due to the important environmental impacts of the lead and electronics used in the solar system. However, this difference is compensated during the entire life cycle from the raw material extraction to the end of life because the traditional system consumes a significant amount of energy from the Lebanese electricity grid during the use phase. The grid mostly relies on thermal power plants, imported fuel, and diesel generators. The results show that the solar system has less overall environmental impacts than the traditional system for both landfilling and recycling scenarios. In particular, it is shown that the recycling scenario for the solar system results in positive impacts on the environment.
author_names: Scarlett Tannous

Rima Manneh

Hassan A Harajli

Henri El Zakhem
title: Comparative cradle to grave life cycle assessment of traditional grid connected and solar stand alone street light systems: A case study for rural areas in Lebanon
year: 2018

abstract: Author(s) Chou, Shu Yu Advisor(s) Pei, Qibing Abstract: According to recent research reports, the global market for display and lighting products is expected to grow to 169.17 billion USD by the year 2022. Display technologies include the light emitting diode (LED) liquid crystal display (LCD) organic light emitting diode (OLED) quantum dot light emitting diode (QDLED) and electronic paper display (EPD) whereas LEDs have been the dominant lighting solution in the past two decades due to their long lifetime and use of non hazardous materials. However, the growth in revenue for LED technology is predicted to slow down due to the advancement in OLED technology. OLEDs are known to be more energy efficient, have higher picture quality, and are more lightweight than LEDs. The bottleneck for OLEDs is their high production cost, which restrains it from the mass market. Fortunately, the development of conjugated polymer emitters shifts the manufacturing process from vacuum thermal evaporation to a solution processed methodology (i.e. ink jet printing, roll to roll printing, screen printing, etc. which is much more cost effective. The resulting OLED, also referred to as a polymer light emitting diode (PLED) shows enormous potential in the future of display technologies. Alongside the PLED, a new class of solution processable emitters, the organometal halide perovskite, has also shown promising performance in lighting applications. Despite their advantages, solution processed emitters have also shown lower device performance when compared to thermal vapor evaporated OLEDs. Due to the limitation of solution processed materials to withstand the solvent attack from advancing layers, solution processed light emitting devices usually have overly simple structures; this results in poor device performance, which can be attributed to the imbalance of charge injection. This dissertation focuses on improving the efficiency and stability of light emitting devices based on conjugated polymer emitters and organometal halide perovskite emitters by employing novel device architectures. In addition, based on the beneficial characteristics of the perovskite and polymer blend film, multifunctional devices including light emitting touch responsive devices and stretchable perovskite light emitting diodes are also demonstrated here. To begin, a white conjugated polymer emitter was applied on a flexible silver nanowire (AgNW) nanoparticle composite electrode, which resulted in a high out coupling efficiency with a 95% enhancement. The flexible nanocomposite electrode was made with silver nanowire electrode and barium strontium titanate (BST) nanoparticles. The high out coupling efficiency is achieved by replacing the ITO electrode with AgNW and by incorporating BST nanoparticles. Replacement of the ITO avoids light trapping inside the ITO caused by the mismatch of the refractive index, and the BST nanoparticles serve as the light scattering center that changed the path of the trapped light inside the substrate. The use of white conjugated polymer emitters on the light extraction substrate demonstrates a means to fabricate high efficiency flexible PLEDs with low fabrication cost. The white PLED achieved an external quantum efficiency of 27.3% The white conjugated polymer emitter was also used in a new type of optoelectronic device, the organic light emitting transistor (OLET) The white OLET combines both phosphorescent PLED and a transistor with a highly capacitive electrolyte dielectric material. By varying the gate potential, the luminance of the white OLET could be modified from 0.1 to 10,000 cd/m2. This work reveals the possibility of achieving a cost effective active matrix display based on solution processed materials and a simple device structure. Next, the organometal halide perovskite emitter is introduced. In one application, it was used to demonstrate a light emitting touch responsive device (LETD) which could provide instantaneous visualization of pressure mapping. The new LETD incorporates perovskite polymer composite film as the emitter and a flexible AgNW polyurethane as the top electrode. The perovskite LETD emitted an intense green luminescence when a local pressure was applied on the AgNW polyurethane due to the formation of a Schottky contact between the AgNW and the perovskite emissive layer. The fabrication of the perovskite LETD was simple and based on an all solution processed procedure.I also used the perovskite emitter to achieve a stretchable perovskite light emitting diode (PeLED) The PeLED integrates an intrinsically stretchable perovskite emissive layer and a stretchable AgNW polyurethane composite electrode. The stretchable perovskite emissive layer incorporates polyethylene glycol diacrylate (PEG) siliconized acrylate (PDMS) and methylammonium lead bromide. The PEG polymer helps to control the perovskite grain size and achieve a uniform perovskite grain film, while the PDMS polymer serves as the elastic connection that holds the film together and provides stretchability to the film. The composite electrode, AgNW polyurethane, provides high transparency, high conductivity, and high stretchability. With these elements combined, the PeLED could be stretched up to 60% strain while displaying a green electroluminescence. Both conjugated polymer emitters and organometal halide perovskite emitters have been successfully demonstrated in various light applications as a proof of concept. A highly efficient PLED was achieved by employing nanoparticles in the substrate to scatter the trapped light into the air. In addition, by adjusting the three terminal system to a suitable bias condition, the device luminance increased drastically due to the balance of electrons and holes in the OLET device. A robust and stable perovskite emissive layer was achieved by incorporating a PEO polymer, and an LETD was created that enables instantaneous pressure mapping. By adding an elastic polymer into the perovskite, a stretchable PeLED was also demonstrated. The results verify the potential of both conjugated polymer emitters and perovskite emitters for large scale, low cost lighting applications and for commercial use.
author_names: Shu-Yu Chou
title: Solution Processed Polymer and Perovskite Emitters for Novel Light Emitting Applications
year: 2017

abstract: This paper highlights the benefits and possible drawbacks of a DC based lighting infrastructure for powering Light Emitting Diode (LED) lamps. It also evaluates the efforts needed for integrating the so called smart lighting and other sensor/actuator based control systems, and compares existing and emerging solutions. It reviews and discusses published work in this field with special focus on the intelligent DC based infrastructure named EDISON that is primarily dedicated to lighting, but is applicable to building automation in general. The EDISON "PowerLAN" consists of a DC based infrastructure that offers telecommunication abilities and can be applied to lighting retrofitting scenarios for buildings. Its infrastructure allows simple and efficient powering of DC oriented devices like LED lamps, sensors and microcontrollers, while offering a wired communication channel. This paper motivates the design choices for organizing DC lighting grids and their associated communication possibilities. It also shows how the EDISON based smart lighting solution is evolving today to include new communication technologies and to further integrate other parts of building management solutions through the OneM2M (Machine to Machine) service bus.
author_names: P Ramya

M Praveen Kumar
title: An Energy Efficient Dc Lighting Grid Using IOT
year: 2018

abstract: Rising population numbers place ever increasing demands on energy resources. A large percentage of the worldwide energy production is reserved for the generation of electricity and a significant portion of the electrical energy generation is used for illumination purposes. At the same time, people demand brighter light sources that provide better light quality. The luminaire of today is not just a simple lamp, but a complex, intelligent piece of technology designed for a specific purpose. This doctoral dissertation aims to provide a link between the theoretical universe surrounding the physics of electromagnetic radiation and the practical illumination world. A theoretical framework presents the physical properties of light and connects, through the human visual system, to a number of perceptual models. Based on these perceptual models, the colourimetric qualities of an illumination spectrum are analysed and a theoretical framework that aims to optimise the balance between colour fidelity and energy efficiency is proposed. The result of this optimisation is a spectrum that needs to be implemented into a light source. Recent advancements in semiconductor technology led to the development of highly efficient light emitting diodes. The monochromatic nature of these light sources offers the possibility of creating a spectrally tuneable luminaire that is able to reproduce these optimised illumination spectra. A fully integrated spectrally tuneable light engine combines knowledge on characterising and driving LEDs, optical design and thermal management. Each group of monochromatic LEDs needs a variable current source that ensures predictable behaviour regardless of their dimming level or temperature. An advanced optical solution enables efficient light extraction from the LEDs, provides excellent luminance and chroma homogenisation and, finally, delivers a suitable beam pattern for the intended illumination application. Proper thermal management establishes sufficient heat extraction to guarantee low semiconductor temperatures. Finally, the LED light engines created during this doctoral research are incorporated into three spectrally tuneable illumination devices, each designed for a specific purpose. A set of spectrally tuneable downlights installed in the laboratories of the lighting group of the Catalonia Institute for Energy Research (IREC) in Barcelona, Spain and the department of neuroscience of the University of Newcastle in the United Kingdom serves as a valuable tool for experiments that evaluate both physical and psychovisual properties of selected illumination spectra. A compact spotlight, used during the "Making Colour" exhibition of the National Gallery in London, is optimised to provide a set of specific illumination spectra to illuminate art reproductions. Lastly, a high power luminaire was designed to generate specialised spectra to irradiate greenhouse plants, steering their morphology and the production of plant specific compounds.
author_names: Wim Hertog
title: The design and implementation of a spectrally tuneable led based light sourde: towards a new era of intelligent illumination
year: 2017