News

Researchers developed highly accurate method for measuring luminous efficacy of LEDs

The method helps discovering the most efficient lamps, which may save billions in lighting costs in the future.

 

PQED consists of a Brewster window (left) protecting the detector elements from impurities, adjustable bellows and the detector chamber itself. In order to further decrease uncertainties in measurement, the window was removed and the detector was protected from impurities using nitrogen flow.

Researchers at Aalto University and VTT Technical Research Centre of Finland have succeeded in developing a method which helps to improve the relative uncertainty in measuring the luminous efficacy of LEDs from the approximate five percent of today to one per cent in the future. The results were just published in the distinguished Light: Science & Applications journal.

­– Thus far, solutions based on incandescent lamps have been used in photometry, i.e. in measuring light detected by the human eye, explains Tomi Pulli, a doctoral student at Aalto University.

– The photometers that lamp manufacturers use for calibrating their devices have been produced and calibrated for incandescent lamps, which results in errors when measuring the efficacy of LEDs. In our research, we used a LED lamp with a well-defined spectrum and a PQED detector, which we developed together with VTT MIKES Metrology and European partners, and whose spectral responsivity can be determined highly accurately.  Therefore, there was no need for the problematic optical filters used in applications based on incandescent lamps. Indeed, accurately determining and analysing the spectrum of the LED was the most challenging and crucial part of the research, he reveals.

Doctoral students Timo Dönsberg (back) and Tomi Pulli measuring the illuminance of LEDs.

From a dot to a sphere

The detector used in measurements by Pulli and his co-researchers measures the illuminance of LEDs in a very small area. According to Professor Erkki Ikonen, the head of research, the next step will be to move onto measurements corresponding to real-life conditions for lighting.

– LED lamps emit light to all directions. In order to measure the luminous efficacy, we thus use a device called an integrated sphere, which takes into account light coming from different directions, he specifies and reminds us that the history of LEDs is still short when compared to incandescent and fluorescent lamps. Therefore, there is still little information available on their actual efficacy and ageing properties. Indeed, it is essential to determine luminous efficacy as accurately as possible so that such lamps can be introduced in the market that transform as much electrical energy into light useful to the human eye as possible.

– So far, the portion of LEDs has been merely around ten per cent globally, but the amount is increasing at a rapid pace, Ikonen explains.

– Lighting amounts to approximately 20 per cent of the electricity consumption in the world. Once the share of LEDs increases close to 50 per cent, an improvement of as little as one percent in the accuracy of measuring the luminous efficacy of the lamps introduced in the market will mean saving billions of euros each year.

More information:

Doctoral Student Tomi Pulli

Aalto University, School of Electrical Engineering

tel. +358 50 408 2782
[email protected]

Professor Erkki Ikonen

Aalto University, School of Electrical Engineering

tel. +358 50 550 2283
[email protected]

Light: Science & Applications journal

  • Published:
  • Updated:
Share
URL copied!

Related news

Aallon 3D-logo niityllä. Kuva: Anni Kääriä / Aalto-yliopisto
Honoured, Research & Art Published:

Service Manager of doctoral education Minna Söderqvist received a Best Reviewer Award

Academy of International Business (AIB) named several winners in the field.
dried seaweed displayed in reds, yellows and greens
Research & Art, University Published:

Engaging with materiality and colour through biocolourants

The BioColour project organizes a broad audience event on Monday 17.8, concentrating on different points of view on materiality and colour. Julia Lohmann, designer and Professor of Practice in Aalto University, is one of the project’s researchers and a speaker in the event.
TUTA Open positions
Research & Art Published:

Open position for PhD student or post-doc with skills in structural equation modeling

6 month project on self-organizing and work engagement seeking for data analyst
valoanturi
Press releases, Research & Art Published:

Black silicon photodetector breaks the 100% efficiency limit

The efficiency was so high that at first the researchers had a hard time believing the result. Now Aalto University spin-off company ElFys Inc. already supplies the record detectors for several industry sectors.