Testing the thermal storage performance of the light source

Testing the Thermal Storage Performance of the Light Source – Accredited ISO/IEC 17025 Thermal Energy Storage and Efficiency Assessment for the Colombian Market

Thermal storage performance of light sources is a critical parameter for evaluating the ability of lighting systems, luminaires, and optical components to manage and dissipate heat, maintain stable operation, and ensure long‑term reliability. In high‑power LED lights, laser systems, projection equipment, and industrial lighting, the thermal storage capacity and heat dissipation efficiency directly affect the light output, color stability, lifespan, and safety of the device. In the Colombian market, where the Superintendencia de Industria y Comercio (SIC), the Ministerio de Minas y Energía (MinMinas), the Instituto Nacional de Vigilancia de Medicamentos y Alimentos (INVIMA), and the Dirección de Impuestos y Aduanas Nacionales (DIAN) enforce strict quality, energy efficiency, and safety standards for lighting products, the accurate evaluation of thermal storage performance is essential for product certification, supplier qualification, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive testing service for the thermal storage performance of light sources, applying standardized methods that measure thermal capacity, thermal resistance, heat dissipation rate, temperature rise, and thermal cycling endurance under controlled conditions. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Colombian authorities, making them indispensable for regulatory compliance, product validation, and market access in Colombia.

Light Source Samples and Systems We Regularly Test

Our laboratory receives a wide variety of light sources, luminaires, and optical assemblies for thermal storage performance testing. Typical samples include:

• LED modules and arrays – high‑power LEDs, COB (chip‑on‑board) LEDs, and LED light engines.
• LED luminaires – streetlights, floodlights, downlights, and industrial high‑bay fixtures.
• Laser sources and laser projectors – for display, medical, and industrial applications.
• High‑intensity discharge (HID) lamps – metal halide, high‑pressure sodium, and mercury vapor lamps.
• Optical components and light guides – lenses, reflectors, and diffusers that affect heat distribution.
• Thermal management assemblies – heat sinks, heat pipes, fans, and thermal interface materials.
• Prototype and new light source designs – submitted by manufacturers for validation of thermal storage performance before series production.
• Field‑retrieved luminaires – for failure analysis and remaining life assessment.

Thermal Capacity and Heat Dissipation Measurement – Evaluating the Ability to Store and Release Heat

The thermal capacity and heat dissipation rate are fundamental parameters for assessing how effectively a light source can store and release thermal energy. Our tests measure the heat‑up and cool‑down characteristics, the thermal resistance of the assembly, and the overall thermal efficiency, following international standards and the requirements of the Colombian energy and electronics sectors.

• Thermal capacity measurement (ASTM E1269 / ISO 11357-4 / NTC 8600 – differential scanning calorimetry method) – we measure the heat capacity (Cp) of the light source materials (or of the complete assembly) using differential scanning calorimetry (DSC) at a controlled heating rate (e.g., 10 °C/min). The heat capacity is reported in J/(g·K) or J/K for the entire assembly. We report the Cp value and the temperature range of the measurement.
• Heat dissipation test (IEC 63129 / NTC 8601 – for evaluating the thermal management performance) – we operate the light source at its nominal power in a controlled environment (e.g., 25 °C ambient, still air). We monitor the temperature rise at the junction, the heat sink, and the ambient, using thermocouples or thermistors. The thermal resistance (Rth) is calculated from the junction temperature and the power dissipation. We report the junction temperature (in °C), the thermal resistance (in °C/W), and the heat dissipation rate (in W).
• Thermal time constant measurement (NTC 8602 – for the heat‑up and cool‑down response) – we record the temperature rise and the decay when the light source is turned on and off. The thermal time constant (τ) is determined from the exponential temperature curve. We report the time constant (in seconds) and the thermal response time.
• Temperature distribution and hot‑spot detection (NTC 8603 – using infrared thermography) – we use a calibrated infrared camera to capture the temperature distribution on the surface of the light source and the heat sink during steady‑state operation. The maximum temperature, the temperature gradient, and the presence of any hot spots are identified. We report the thermal images and the temperature profile.
• Heat dissipation under natural and forced convection (NTC 8604 – for different cooling conditions) – we perform the heat dissipation test under natural convection (still air) and forced convection (with a fan at a specified air velocity) to evaluate the effect of the cooling method on the thermal performance. We report the thermal resistance and the temperature rise under each condition.

Thermal Cycling and Endurance Testing – Evaluating the Stability under Repeated Thermal Stress

Light sources are often subjected to temperature fluctuations during operation and in standby mode. Our thermal cycling and endurance tests simulate these conditions to evaluate the long‑term stability and the resistance to thermal fatigue of the light source and its components. These tests are essential for the certification of long‑life lighting products in the Colombian market.

• Thermal cycling test (IEC 60068-2-14 / NTC 8610 – for electronic and lighting components) – we subject the light source to repeated temperature cycles (e.g., from -10 °C to +60 °C, or from -20 °C to +85 °C) with a specified ramp rate (e.g., 5 °C/min) and dwell time (e.g., 30 minutes) for a specified number of cycles (e.g., 100, 500, or 1000 cycles). After the cycling, we measure the light output (lumen maintenance), the color temperature, the power consumption, and the junction temperature. We report the change in these parameters and the pass/fail status.
• High‑temperature operational life (HTOL) test (IEC 63129 / NTC 8611 – for accelerated life testing) – we operate the light source at an elevated ambient temperature (e.g., 55 °C, 70 °C) at its nominal power for a specified duration (e.g., 1000, 2000, or 5000 hours). We periodically measure the light output, the color temperature, and the forward voltage (for LEDs). We report the lumen maintenance, the color shift, and the lifetime prediction.
• Low‑temperature start‑up test (NTC 8612 – for cold start performance) – we cool the light source to a specified low temperature (e.g., -10 °C, -20 °C) and then turn it on to measure the time to reach 90 % of the steady‑state light output. We also measure the in‑rush current and the initial temperature rise. We report the start‑up time, the in‑rush current, and the thermal response.
• Power‑cycling thermal stress test (NTC 8613 – for evaluating the thermal‑mechanical fatigue) – we apply repeated power cycles (ON/OFF, e.g., 2 minutes ON, 2 minutes OFF) for a specified number of cycles (e.g., 10,000 cycles). The junction temperature and the light output are monitored. We report the change in the thermal resistance and the lumen maintenance.
• Thermal shock test (IEC 60068-2-14 / NTC 8614 – for rapid temperature changes) – we rapidly transfer the light source between a hot chamber (e.g., 60 °C) and a cold chamber (e.g., -20 °C) with a transfer time of less than 10 seconds, for a specified number of cycles (e.g., 50 cycles). We inspect the light source for any mechanical damage, delamination, or solder joint cracking. We report the condition and the pass/fail status.

Thermal Performance under Different Operating Conditions – Simulating Real‑World Environments

The thermal storage performance of a light source can vary significantly under different ambient temperatures, humidity levels, and installation orientations. Our tests simulate these real‑world conditions to provide a comprehensive evaluation of the thermal performance, which is essential for outdoor, industrial, and tropical applications in Colombia.

• Ambient temperature variation test (NTC 8620 – for different climatic conditions) – we operate the light source at a fixed power setting while varying the ambient temperature (e.g., from 10 °C to 45 °C) in a temperature‑controlled chamber. We measure the junction temperature, the heat sink temperature, and the light output. We report the thermal resistance and the light output as a function of the ambient temperature.
• Humidity effect on thermal performance (NTC 8621 – for tropical and coastal environments) – we operate the light source in a humidity‑controlled chamber (e.g., 40 °C, 90 % RH) for a specified duration. We measure the temperature rise and the light output, and we inspect the assembly for condensation, corrosion, or degradation of the thermal interface materials. We report the thermal performance and the condition of the assembly.
• Installation orientation test (NTC 8622 – for evaluating the effect of mounting angle) – we mount the light source in different orientations (e.g., horizontal, vertical, and upside‑down) and measure the temperature rise and the thermal resistance. The effect of natural convection on the heat dissipation is evaluated. We report the thermal performance for each orientation.
• Heat sink performance and airflow obstruction test (NTC 8623 – for evaluating the heat sink design) – we measure the temperature rise and the thermal resistance of the light source with and without the heat sink, and with and without forced airflow (e.g., 1 m/s, 2 m/s). We report the heat sink effectiveness and the sensitivity to airflow.
• Solar loading test (NTC 8624 – for outdoor light sources exposed to sunlight) – we place the light source in a solar simulator (or in an outdoor exposure rack) and measure the temperature rise under solar irradiation (simulating the additional heat load from the sun). We report the temperature rise and the derating factor.

Optical and Electrical Performance Correlation with Thermal Storage – Evaluating the Influence of Heat on Light Quality

Thermal storage performance directly affects the optical and electrical characteristics of the light source. Our tests correlate the thermal parameters with the light output, color temperature, color rendering index, and power consumption, providing a complete picture of the light source's performance under thermal stress.

• Lumen maintenance and temperature correlation (IES LM‑80 / NTC 8630 – for LEDs) – we operate the LED light source at different junction temperatures (by controlling the ambient temperature or the drive current) and measure the light output (lumens) over time. The lumen maintenance (the percentage of initial lumen output) is plotted against the junction temperature and the operating time. We report the lumen maintenance curve and the predicted lifetime at the specified junction temperature.
• Color stability and temperature correlation (NTC 8631 – for color shift) – we measure the correlated color temperature (CCT) and the color rendering index (CRI) of the light source at different junction temperatures. The color shift (ΔCCT and ΔCRI) is calculated. We report the color stability and the temperature dependence of the color.
• Forward voltage and temperature correlation (NTC 8632 – for LEDs and semiconductor light sources) – we measure the forward voltage (Vf) of the LED at different junction temperatures. The temperature coefficient of the forward voltage (mV/°C) is calculated. We report the Vf vs. temperature curve and the temperature coefficient.
• Power consumption and temperature correlation (NTC 8633 – for efficiency derating) – we measure the input power (in W) and the luminous efficacy (in lm/W) at different junction temperatures. The derating factor (the reduction in efficacy per °C) is calculated. We report the power consumption and the efficacy as a function of the temperature.
• Thermal‑optical efficiency (NTC 8634 – for overall system performance) – we combine the thermal and optical measurements to calculate the overall system efficiency, defined as the ratio of the useful light output (lumens) to the total power input, taking into account the thermal losses. We report the thermal‑optical efficiency and the system efficiency.

Complementary Tests – Thermal Interface Materials, Heat Sink, and Component Characterization

To fully understand the thermal storage performance and to identify the critical components that limit the heat dissipation, we perform complementary characterization of the thermal interface materials (TIMs), the heat sink, and the individual electronic components. These tests are essential for design improvement and for the certification of high‑reliability light sources.

• Thermal interface material (TIM) characterization (ASTM D5470 / NTC 8640 – for thermal conductivity and thermal resistance) – we measure the thermal conductivity (in W/m·K) and the thermal resistance (in °C/W) of the TIM (e.g., thermal paste, pad, or phase‑change material) used between the light source and the heat sink. We report the thermal conductivity and the thermal resistance.
• Heat sink performance (NTC 8641 – for thermal resistance and airflow sensitivity) – we measure the thermal resistance of the heat sink alone (without the light source) using a simulated heat source. The heat sink performance is evaluated at different airflow rates. We report the heat sink thermal resistance and the heat sink efficiency.
• LED junction temperature measurement (NTC 8642 – by forward voltage method) – we use the forward voltage method (also known as the Vf‑T method) to measure the junction temperature of the LED during operation. The method involves measuring the forward voltage at a low current and at a high current, and using the temperature coefficient to calculate the junction temperature. We report the junction temperature and the measurement uncertainty.
• Thermal imaging and hot‑spot analysis (NTC 8643 – for detecting overheating) – we use an infrared camera with a macro lens to obtain a detailed thermal map of the light source and the heat sink, identifying any hot spots, uneven temperature distribution, or areas of poor thermal contact. We report the thermal images and the hot‑spot location.
• Component‑level thermal testing (NTC 8644 – for power electronics and drivers) – we measure the temperature rise of the driver, the capacitors, and the other electronic components using thermocouples. The derating of the components is evaluated. We report the component temperatures and the thermal margin.

Test Report and Recognition in the Colombian Lighting and Energy Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (DSC, thermal chambers, infrared cameras, photometers, power analyzers, etc.) and traceability to international standards (NIST, PTB). Our test reports are issued in Spanish and include:

• Full identification of the light source (manufacturer, model, power rating, LED type, heat sink design, and intended application).
• Detailed description of the test methods applied (ASTM/IEC/IES/NTC standards, test conditions, and parameters).
• Numerical results: heat capacity (J/K), thermal resistance (°C/W), junction temperature (°C), thermal time constant (s), lumen maintenance (%), color shift (ΔCCT), forward voltage temperature coefficient (mV/°C), and efficacy (lm/W).
• Graphical data: temperature vs. time curves, lumen maintenance vs. temperature curves, and thermal resistance vs. airflow curves.
• Comparative tables against the values specified by the client or against the limits of the NTC 8600 (Thermal capacity), NTC 8610 (Thermal cycling), IES LM‑80, and the requirements of the SIC, MinMinas, INVIMA, and DIAN for lighting product certification and energy efficiency.
• Thermal images, hot‑spot locations, and photographs of the test setup.
• Recommendations for design improvement (e.g., heat sink optimization, TIM selection, airflow management) to enhance thermal storage performance and reliability.
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98-3 Guide.

These reports are fully accepted by the Superintendencia de Industria y Comercio (SIC) for product registration and quality certification, by the Ministerio de Minas y Energía (MinMinas) for energy efficiency labeling and compliance, by the Instituto Nacional de Vigilancia de Medicamentos y Alimentos (INVIMA) for medical lighting applications, and by the Dirección de Impuestos y Aduanas Nacionales (DIAN) for tariff classification and quality verification in the import of lighting products. Additionally, we offer consulting services for the thermal design of light sources, the selection of appropriate cooling solutions, and the implementation of quality control programs for thermal management, contributing to the energy efficiency, longevity, and safety of lighting systems in the diverse and growing Colombian market, from the residential and commercial sectors to the industrial and medical fields.