DUTCH DEBATES

Stuart Mucklejohn reports from IEEE’s Sustainable Smart Lighting Conference held in November in Eindhoven in the Netherlands.

The Institute of Electrical and Electronic Engineers (IEEE) Sustainable Smart Lighting Conference, also known as LS2024, was held from 12-14 November, hosted by Eindhoven University of Technology. The meeting was preceded by the annual ‘ILIAD’ event organised by the Intelligent Lighting Institute of the university.

ILIAD opened with a wide-ranging review of what makes healthy buildings by Sywert Bongersma. Lighting certainly plays an important role, ideally with indistinguishable combinations of natural and artificial light.

However, Sywert argued, it is essential to strike the appropriate balance of lighting, ventilation, noise and the thermal environment to make a building comfortable for its occupants.

Reliable, energy-efficient sensors are vital to ensure healthy buildings are also economically affordable to run. Yvonne de Kort, in her presentation ‘Could there be more to light than lux and mEDI?’ (mEDI = melanopic equivalent daylight illuminance) stressed the links between light, mood and mental health.

Substitution of natural light by artificial light does not always produce the same health benefits perhaps because the latter usually lacks contributions from UV-B and the near-IR, she highlighted. Many in the audience were surprised to learn radiation between 810 nm and 830 nm penetrates the skin and the skull.

After an introduction from Georges Zissis, chair of the IEEE Smart Lighting Steering Committee, LS2024 began with three fascinating contributions.

DAYLIGHT AND NATURAL LIGHT

First, Marilyne Andersen reviewed the importance of both the variability in intensity and SPD (spectral power distribution) in natural light. These changes should ideally be reflected in indoor lighting. Our ‘spectral diet’ should be close to that we would experience outdoors, Marilyne argued.

John Mardaljievic then gave an account of the history of the measurement of daylight from Socrates to modern-day satellites.

Peter Thorns went into great detail about the derivations of the candela, one of the seven SI base units and the only one that depends on a human response. Peter also surveyed the measurements that led to the current value of V(l), picking up on his recent article in Lighting Journal (‘One hundred years of V(λ)’, October 2024, vol 89 no 9) and presentation to last year’s ILP Centenary Lighting Summit.

The value most commonly used is that for a 2o observer but there is a growing view that for many applications, especially driving, the 10o values would be more suitable.

One of the limitations of V(l) is that it disregards the impact of age-on-vision perception. The future will almost certainly see V(l) and all photometry based on cone fundamentals, for example see ‘Cone fundamentals and CIE standards’ by Andrew Stockman, Current Opinion in Behavioral Sciences, Vol. 30, p. 87-89, 2019.

The late afternoon sessions were a choice between either the ‘Play with light workshop’ (TU/e Innovation Space) or a visit to the Signify Lighting Application Centre.

Signify was very generous in accepting 70 guests into its application centre. Two tour parties were invited into warehouse, retail, supermarket and office layouts displaying numerous lighting solutions. A great deal of thought and engineering had gone into being able to show the differing appearances of various lighting designs.

Anne Skeldon from the University of Surrey gave a detailed account of her research into the impact of light-dark cycles on human sleep and circadian timings. Sleep timing is determined by physiology but is strongly influenced by light exposure and social constraints, she highlighted.

IMPACTS OF LIGHT POLLUTION

The impacts on ecological systems of the worldwide increase in light pollution were stressed by Annika Jagerbrand. There is a pressing need for changes to international obtrusive light thresholds, this is in part being addressed by CIE Technical Committee 2-95 Measurement of Obtrusive Light and Sky Glow.

Norman Bardsley, chief analyst for the International Solid-State Lighting Alliance, outlined his team’s vision of how to secure additional energy savings from solid-state lighting.

They estimate the current average efficacy of commercially available LED-based light sources is approximately 83 lm/W; this has risen from ~48 lm/W in recent years.

However, the higher efficacy has been offset by greater demand and so the electric power consumed per annum remains at approximately 2900 TWh. Reducing the total energy consumption for lighting will require involvement from governments.

A target of an average efficacy of ~140 lm/W by 2030 seems to be achievable but the longer-term target of 300 lm/W requires major improvements in phosphors, control of light distribution and manufacturing processes.

Erkki Ikonen described detailed TLM measurements on 60 LED lamps with E27 bases, 40 of which were purchased prior to 2017 with the remainder from 2021.

Between these dates EU regulations for TLM limits had changed to Pstlm  >1 and SVM <0.4. All lamps satisfied the Pstlm limit but half of the pre-2017 lamps did not meet the new SVM limits. All of the newer lamps were within both limits, a good example of manufacturers following the regulations. Lighting Research & Technology Vol. 56(7) published in November 2024 is devoted to TLM. 

Melissa Handa introduced the attendees to the IEEE DataPort (https://ieee-dataport.org/), a research data platform designed to make scientific data openly accessible to all and help researchers and institutions share research, manage their data, and collaborate with peers. IEEE membership is not required to use this tool, there is no charge for uploading datasets but access to some datasets is chargeable.

The conference closed with two contrasting presentations. The first was by Sylvia Pont from the Technical University of Delft on ‘Interaction of light with materials – lighting materials and materializing light’. The second by Christian Tenhumberg, from Signify, on ‘Manage, monitor and control lighting with connected and integrated solutions’.

The former concentrated on the human perception of light reflected by materials and the way various spectra appear to change the visual appearance of objects. One telling comment: ‘Perception is not physics!’.

The latter highlighted that turning lights off is not a realistic solution for reducing energy consumption, a far better approach is the extensive use of sensors and controls. The increase in the number of lighting-related connected nodes is staggering, from ~80,000 in 2012 to ~139 million in 2023.

The central themes of this meeting were: the measurement and impact of TLM; light pollution and the importance of darkness for humans as well as ecosystems; the need to extend lighting education for those involved in the industry as well as the public, the definition of the right light.

Congratulations go the local organising committee under the leadership of Jean-Paul Linnartz for arranging such a stimulating meeting with a warm and welcoming atmosphere.

The programme for LS2024 can be downloaded from: https://www.ssleindhoven.com/program. Papers from the conference will be available via IEEE Xplore.

GLOW LIGHT FESTIVAL

Finally, the conference coincided with the GLOW light festival (pictured above), which was a free-to-attend event with displays stretching throughout much of Eindhoven city centre.

The festival encourages the promotion of light artworks where artists, businesses, residents and students can work together by combining technology with creativity to generate fascinating displays together with a visually exciting atmosphere.

The festival attracts thousands of visitors to the city each of the eight days of the event. Students kindly led tours of the displays for the LS2024 participants.

The next conference in this series will be held in Monastir, Tunisia during early December later this year.

This will mark the 50th anniversary of the first symposium in the LS series, which began as the ‘Symposium on Incoherent Light Sources’ held at Loughborough all the way back in April 1975.

Stuart Mucklejohn is secretary of the LS2024 International Scientific Committee

This is an abridged version of the article that appears in February’s edition of Lighting Journal. To read the whole article, simply click on the page-turner opposite.

Image courtesy of Stuart Mucklejohn

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