National Physical Laboratory

The life and light of LEDs

Summary

Luminaz LEDs

NPL worked with UK company Luminanz to help them accurately demonstrate the reliability of their LED products through specialised temperature measurement techniques.

There is a direct relationship between how hot an LED gets, and the LED's lifetime. If you can monitor the LED operating temperature, you can predict how it will perform during its lifetime. This information is essential to lighting manufacturers, such as Luminanz, so that their products can meet their customers' needs and expectations.

About the Customer

Luminanz is a small high technology start up (founded in 2007), based in Bolton, which has pioneered a#160;number of light emitting diode (LED) lighting innovations including edge-lighting, air-gap technology and wave-guiding.

The Challenge

Luminanz needed NPL's help to measure the relationship between the temperature of their solid-state 'light engine' LEDs, and how they perform over their long lifetime. It is particularly important to understand this relationship in their high brightness white LEDs, some of which may need to operate continuously for at least five years. Luminanz have their own perspective on optimum thermal management and measurement within LED lighting fixtures, and they needed NPL's support in confirming the validity of their approach, and certainly in terms of measurement, because of the complexity of some of the available measurement methods they were keen to confirm the reliability of a straightforward method that they could use within their own laboratory. According to Dr Neil Haigh, Technical Director of Luminanz: "In terms of LED junction temperature measurement, there are a number of relatively complex techniques and modelling approaches we could have adopted, but we instead to confirm the usefulness or otherwise of some of the more simpler, practical approaches that can be taken. We are satisfied that we have now established a reliable baseline to this important metric for LED lighting products."

The Solution

Luminanz brought some of their products along to NPL's specialised testing facilities, where a range of LED junction temperature measurement approaches were considered including for example the use of a calibrated thermal camera that can identify the locations of hot spots within the LED fitting. The thermal imaging approach was useful for quickly confirming that the LEDs' temperature was significantly below the upper limit guideline of 80 ºC (needed to help confirm the lifetime of the fitting), and further analysis work at NPL using an alternative approach now allows Luminanz to pinpoint the LED temperature more directly.

The Impact

Following its work with NPL, Luminanz won a Shell Springboard award of £40,000 which recognised its efforts to promote the UK's low carbon economy.

A licence deal worth approximately £5 million was significantly supported by Luminanz' complete confidence in temperature measurement, and therefore the proper lifetime predictions for their products. "We estimate that between 5% and 10% of our licence income can be attributed to our authoritative prediction of lifetimes for our technology"," said Luminanz inventor and managing director, Morton Graham.

Individuals and businesses alike are more likely to use LEDs if they are confident that they will last a long time, and save them money. This confidence could accelerate the adoption of solid-state lighting, which would lead to considerable benefits for the UK consumer and the planet. In 2010 there was around 200 million incandescent and 175 million tungsten halogen lights in UK households. Replacing all these with LED lights would cut household energy usage (and therefore bills) by 3.8 TW hrs and save 1.6 million tonnes of carbon dioxide.

For further information, please contact Paul Miller

Find out more about NPL's work in Optical Radiation & Photonics and Sustainability

Last Updated: 10 Oct 2012
Created: 17 Jan 2011

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