Abstract

Energy has been identified as one of the most important problems during the last few years. One of energy efficient technologies may reduce consumed energy in buildings from 20 percent to less than 5 percent. A novel lighting technology has recently been evolved as light emitting diodes (LEDs) that can be over 7–10 times more efficient than conventional-old incandescent lamps. Therefore, LED lighting systems have been rapidly replacing conventional energy-hungry lighting products like incandescent lamps and more recently environmentally hazardous fluorescent lamps. While LEDs may produce large amounts of lumens, they are solid state based technologies similar to computer chips so they have to be kept cool at certain chip junction temperature. The demand for high light output LED systems lead to significant heat generation rates, so that higher heat fluxes result in elevated junction temperatures on LED chips in SSL lighting systems. Moreover, the changes on the junction temperature strongly impact the reliability, lifetime, light output and quality of the light. Because of their simplicity, reliability, low cost and silent operation, passive air-cooling systems are preferred in LED lamps. Passive metal based heat sinks are the main cooling components of typical LED lamps serves for both LEDs and driver electronics. Heat is dissipated generally from finned surfaces to ambient air with primarily convection mechanism and partially radiation. But it requires a large surface area and weight under the limitations of the standardized lamps. Thus, the optimization of the heat sink in an LED system is crucial. Developing figure of merits (FOM) is very important for designers and researchers to find the most optimal solution accounting for critical metrics such as size, weight, cost and performance. In the present study, thermal, electrical and optical experimental results of various commercial A-line LED lamps are investigated and a number of FOMs are proposed based on the performance, size and weight. Proposed FOMs aim to evaluate different aspects by combining a number of performance metrics. Results show that one can combine and analyze multi-purpose design parameters for thermal, electrical and optical performances and manufacturing for engineers and consumers.

Highlights

  • Energy is one of the top 10 challenges for human being as cited by Nobel prize laureate Richard Errett Smalley in 2001 [1]

  • This study offers several figure of merits (FOM) to enable the interpretation for the desired issues

  • Low thermal resistance alone may not be enough to select for a heat sink because of the unacceptable time and energy consumption required during manufacturing or the manufacturing capability requirements

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Summary

Introduction

Energy is one of the top 10 challenges for human being as cited by Nobel prize laureate Richard Errett Smalley in 2001 [1]. Lighting represents approximately 16% of residential and 20% of commercial building electricity consumption [2] Researchers developed technologies such as fluorescent lamps that has over four times of comparable incandescent lamps, and they have been widely used during the last four decades. While LEDs can provide superior optical performances at low energy consumptions, they pose significant thermal challenges due to inherit solid-state device technology based on light-generating active layers. Besides the simplicity of fabrication without the requirement of a high-tech manufacturing facility, mature industrial utilities keep heat sink production low priced on this long-experienced field. This was driven by the electronics industry while the performance has been increasing, size and cost has been shrinking.

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