Encapsulated PCM Thermal Storage for LED Junction Temperature Control
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Solution Overview
Problem
LED performance is compromised by high ambient temperatures, leading to overheating and potential device failure, especially in applications where adequate heat sinking or cooling is challenging due to size constraints and inefficiencies of conventional thermal management methods.
Innovation Solution
The use of phase change materials (PCMs) in close contact with the LED lighting system for thermal storage, where the PCM's melting point is selected to clamp the LED junction temperature at an optimal operating point, allowing efficient heat absorption and storage without significant temperature increase until phase change, thereby extending LED lifespan and maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If passive thermally conductive materials (e.g., aluminum) are used to absorb heat, then heat storage capacity increases, but the volume and mass required become impractically large
Solution Approach 1:
The patent utilizes phase change materials (PCMs) that undergo phase transition from solid to liquid at a specific melting point temperature. During this phase change, the PCM absorbs large amounts of latent heat while maintaining a constant temperature, enabling compact thermal storage without requiring impractically large volumes of material.
Solution Approach 2:
The invention changes the thermal storage mechanism from relying on specific heat capacity (temperature rise) to utilizing latent heat of fusion (phase change). By selecting PCMs with appropriate melting points and high latent heat values, the system achieves efficient heat storage in a compact form factor suitable for LED lighting applications.
2Power
If aluminum is used for heat convection, then heat transfer efficiency improves, but the thermal capacity required for extended operation becomes excessively large
Solution Approach 1:
The patent employs phase change materials that absorb heat during melting, providing high thermal capacity in a compact volume. This enables the system to handle extended LED operation without requiring excessively large thermal mass, while maintaining efficient heat transfer through the phase change process.
Solution Approach 2:
The PCM acts as an intermediary thermal storage medium between the LED heat source and the external environment. It efficiently absorbs heat during phase change and can subsequently release this stored heat through convection or conduction, providing both high power transfer efficiency and adequate thermal capacity in a compact configuration.
3Productivity
If the LED is driven hard in high ambient temperatures, then light output increases, but overheating occurs leading to poor performance and device failure
Solution Approach 1:
The patent incorporates a thermal storage system with phase change materials that are pre-positioned in thermal contact with the LED package. These PCMs are selected with melting points that correspond to the LED's optimal operating temperature range, enabling them to absorb excess heat before it can cause overheating and damage, thus protecting the LED during high-power operation.
Solution Approach 2:
The invention converts the harmful excess heat that would otherwise cause LED overheating and failure into a useful thermal storage resource. The phase change materials absorb this waste heat during LED operation, and this stored thermal energy can later be dissipated to the environment, transforming a harmful thermal byproduct into a beneficial thermal management mechanism that extends LED lifetime.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively manages temperature fluctuations, maximizing LED output and lifespan while reducing the number of LEDs required, achieving cost savings and improved reliability in temperature-sensitive applications.
Implementation Method 1
When the PCM reaches its melting point, the temperature of the PCM stays at its melting point temperature until the phase of the PCM changes completely from a solid to a liquid. Because a PCM can absorb a large amount of heat during its change of phase from a solid to a liquid, the PCM can store a large amount of heat generated by the lighting system
Implementation Method 2
Because a PCM can absorb a large amount of heat during its change of phase from a solid to a liquid, the PCM can store a large amount of heat generated by the lighting system while maintaining its temperature at its melting point temperature
Implementation Method 3
The PCM is placed in a container in close contact with the lighting system to be cooled. Because the PCM material may have low thermal conductivity, specific PCM containment geometries should be used to provide sufficient thermal coupling to the lighting system in order to efficiently transfer heat to the PCM mass
Data Source
AI summary
A phase change material (PCM) is used as thermal storage for lighting systems. The PCM is placed in a thermally conductive container in close contact with the lighting system. As the PCM absorbs heat, it changes from a solid to a liquid state, but the temperature of the PCM is clamped at its melting point temperature. For LED-based systems, the PCM is selected to have a melting point such that the junction temperatures of the LEDs in the system are maintained at approximately their optimum operating temperature inside the lighting system housing. Because the thermal conductivity of the molten PCM is poor, a low thermal resistance heat flow path is provided from the PCM to the container.