Light Lines March/April 2024

The Society of Light and Lighting

VOLUME 17 ISSUE 2 MARCH/APRIL 2024

CALCULATED MOVE

Light and health: the first parametric tool

IN WITH THE OLD

Award-winning CE office scheme

Editorial

March/April 2024

FROM THE EDITOR SECRETARY Brendan Keely FSLL bkeely@cibse.org EDITOR Jill Entwistle jillentwistle@yahoo.com COMMUNICATIONS COMMITTEE: Andrew Bissell FSLL James Buck Iain Carlile FSLL Jill Entwistle Fiona Fanning Debbie-Sue Farrell Chris Fordham MSLL Rebecca Hodge Stewart Langdown FSLL Luke Locke-Wheaton Rory Marples MSLL Linda Salamoun MSLL All contributions are the responsibility of the author, and do not necessarily reflect the views of the society. All contributions are personal, except where attributed to an organisation represented by the author.

COPY DATE FOR LL3 2024 IS 20 MARCH PUBLISHED BY The Society of Light and Lighting 222 Balham High Road London SW12 9BS www.sll.org.uk ISSN 2632-2838 © 2024 THE SOCIETY OF LIGHT AND LIGHTING The Society of Light and Lighting is part of the Chartered Institution of Building Services Engineers, 222 Balham High Road, London SW12 9BS. Charity registration no 278104 Designed and printed in the UK George Eason Design www.georgeeason.design E: hello@georgeeason.design

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With any progress, there is often a fair amount of talking and not a lot of doing before an idea develops real traction. It has felt a little like that with the concept of the circular economy, a term first coined in 1988.

From a manufacturing point of view it is inevitably a slow process. It requires a great deal of research and assessment of the properties of materials and a rethinking of the production process, among many other factors.

Clearly being green in general terms can be achieved very straightforwardly in some respects but there are also complexities and unforeseen consequences. Solar power would seem to be a no-brainer, for instance, but the disposal of photovoltaic panels is an oncoming train.

Where CE in lighting is concerned, practical calculating tools and guidance, such as the SLL's TM65 and TM66 documents, have been key in moving things forward, providing clear navigation for the path to be followed.

Implementation, theory into practice, is also

crucial. Arup has just provided a good working example for its Manchester office with a comprehensive retrofit project (Good as new, p8). What is particularly interesting is that while Arup had clearly embraced CE principles, it needed the proof of the pudding before recommending it confidently to clients.

'Having been through the process, with no disruption to our daily work and validation of the energy and carbon savings,' says Richard Morris, lighting design leader for Arup’s Manchester office, 'we can share our experience with our clients with confidence and promote luminaire refurbishment as a realistic proposal.'

JILL ENTWISTLE JILLENTWISTLE @YAHOO.COM

CURRENT SLL LIGHTING GUIDES SLL Lighting Guide 0: Introduction to Light and Lighting (2017) SLL Lighting Guide 1: The Industrial Environment (2018) SLL Lighting Guide 2: Lighting for Healthcare Premises (2019) SLL Lighting Guide 4: Sports Lighting (2023) SLL Lighting Guide 5: Lighting for Education (2011) SLL Lighting Guide 6: The Exterior Environment (2016) SLL Lighting Guide 7: Office Lighting (2023) SLL Lighting Guide 8: Lighting for Museums and Galleries (2021) SLL Lighting Guide 9: Lighting for Communal Residential Buildings (2022) SLL Lighting Guide 10: Daylighting – a guide for designers (2014) SLL Lighting Guide 11: Surface Reflectance and Colour (2001) SLL Lighting Guide 12: Emergency Lighting (2022) SLL Lighting Guide 13: Places of Worship (2018) SLL Lighting Guide 14: Control of Electric Lighting (2023) SLL Lighting Guide 15: Transport Buildings (2017) SLL Lighting Guide 16: Lighting for Stairs (2017) SLL Lighting Guide 17: Lighting for Retail Premises (2018) SLL Lighting Guide 18: Lighting for Licensed Premises (2018) SLL Lighting Guide 19: Lighting for Extreme Conditions (2019) SLL Lighting Guide 20: Lighting and Facilities Management (2020) SLL Lighting Guide 21: Protecting the Night-time Environment (2021) SLL Lighting Guide 22: Lighting for Control Rooms (2022) Guide to Limiting Obtrusive Light (2012) Code for Lighting (2022) Commissioning Code L (2018) SLL Lighting Handbook (2018) CIBSE TM66: Creating a Circular Economy in the Lighting Industry (2021) CIBSE TM65.2: Embodied Carbon in Building Services – Lighting (2023)

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March/April 2024

Secretary’s column/Contents

Contents

FROM THE SECRETARY

Twitter: @sll100

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To enter SLL Young Lighter 24: www.cibse.org/get-involved/ societies/society-of-lightand-lighting-sll/sll-events/ sll-young-lighter To apply for the Jean Heap Bursary: www.cibse.org/get-involved/ societies/society-of-lightand-lighting-sll/education/ the-jean-heap-bursary

her work and direction during her year as president.

Looking much further ahead, a date for your diary: we hope to see many of you at Light2Perform 24 which will take place at ExCeL, London, on 13-14 November.

The conference programme at last December’s event was excellent and I have no doubt it will be just as good this year. We will also be exhibiting at LiGHT 24 which takes place at the Building Design Centre, London, on 20-21 November. November is clearly going to be a busy month but there is lots to look forward to.

The SLL Young Lighter 24 competition is now open for entry. We invite anyone who is under 30 on the Stage 1 deadline day (26 April 2024) to enter. The competition is open to all whether you are a photographer, product designer, engineer, lighting designer, student, researcher or you just like light.

There are no boundaries, it does not matter where you are located or what your role is, if you have an idea and it incorporates light then we are interested.

The SLL Jean Heap Bursary 24 is also open. The bursary encourages people to develop research that will benefit the public, members and industry at large.

The deadline for entry is 17 May 2024.

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EDITORIAL

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SECRETARY'S COLUMN

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NEWS

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WELL CONNECTED

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GOOD AS NEW

Teresa Aguilar Carrasco, SLL Young Lighter 2023, summarises her winning paper on the first parametric tool to quantify the effect of light on health

Arup's green award-winning office refurbishment proves an exemplar of collaboration and carbon reduction

10 SMALL WONDER

MicroLEDs: two new reports assess their future and their potential

13 ORCHESTRATED SPACES

Jill Entwistle on the Finnish architect Juha Leiviskä, master of geometry and light, who died at the end of 2023

14 PUBLIC EYE

Iain Carlile singles out three papers in the recent special early career research edition of LR&T, all on the exterior urban environment

15 COUNTIES SET

Top 5: Chris Dicks, winner of the 2023 SLL's Regional Award, looks to his home turf for his inspiration

16 EVENTS COVER: Delta, by local studio Void, is both embedded light sculpture and wayfinding device that flows through an area of Oslo. It won Gold in the Digital Installations category at the European Design Awards and was shortlisted in the architectural lighting design category of the Dezeen Awards 2023

BRENDAN KEELY BKEELY @CIBSE.ORG

Einar Aslaksen

We had a great start to the year exhibiting at Light+Intelligent Building Middle East in Dubai in January. Joining me on the exhibition stand was Andrew Bissell, SLL immediate past president, and I'd like to thank him for making everything so much easier. He pulled many shifts helping me on the stand, as well as speaking at the conference and participating in a panel discussion. I think he was busier than me...

We met some old friends in the UAE region and made many new friends as well, and also gained some new members over the three days. The conference that ran alongside the exhibition was very well received and it will be interesting to see what Light+Intelligent Building Middle East 25 will look like. I really appreciated the opportunity to be there.

I’ll be heading to Light+Building, Frankfurt, in early March to visit the SLL Sustaining Members who are exhibiting and will arrange meetings with them. I also intend to meet with the sponsors who are visiting the exhibition. No doubt, as usual I will bump into a few of you in the halls and corridors of Messe Frankfurt.

We're delighted to say that the Pockets Of Light event at Light Night Leeds, organised by the SLL and held last October (see Light Lines Jan/Feb), has been shortlisted for the events category. SLL members worked with two schools, Alder Tree Primary and Leeds West Academy, to create a lighting installation for Leeds Minster. Good luck to all of you who have entered and look forward to seeing you at the awards night on 27 March.

The SLL AGM Notification and Nominations have been shared with the membership and we look forward to welcoming many of you to the SLL Awards and President’s Address, which takes place at Leeds Art Gallery on the evening of Tuesday 14 May 2024.

It is the second time in recent years that we have taken the AGM, Awards and President's Address outside of London and we're looking forward to joining the Yorkshire Region in celebrating the great and the good in lighting. We will be welcoming Dan Lister to his presidential year and thanking Helen Loomes for

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News

March/April 2024

THE LATEST NEWS AND STORIES

News NEW STUDY REVEALS WHY MOTHS FLY TO THE FLAME Researchers at Imperial College London may have answered a key question concerning the effect of artificial light on nocturnal insects. While flying insects have always been attracted to street lamps and other sources, little has been known about what drives the behaviour.

However, a new study published in the journal Nature Communications reveals that they are using light to work out which way is up by sensing that the sky is light and the ground is dark. Under natural sky light, tilting the dorsum, or back, towards the brightest visual hemisphere helps maintain proper flight attitude and control.

Artificial sources confuse them, and rather than being attracted to and steering directly toward the source, insects are actually turning their dorsum toward the light.

Insects do not fly directly into a light source, but actually 'tilt their backs toward the light,' Sam Fabian, entomologist and co-author of the new study, told Sky News.

This response can produce continuous steering around the light and trap an insect, says the study.

Insect flight was least disrupted by bright lights that shine straight downward, the researchers found.

The study involved high-resolution motion capture in the laboratory and stereo-videography in the field to reconstruct the 3D kinematics of insect flights around artificial lights. www.nature.com/articles/s41467-024-44785-3

ON THE LIGHTER SIDE… It's been a while since we've had a bonkers lamp. There have been more outré examples, but this qualifies by being inspired by the human body – the design resembles the vascular system through which blood cells move – and something about aliens.

'The Dif Lamp is made from terrestrial cells sent to our planet by the hero Thymus in order to protect it from infectious agents, Viroids and Bagds,' says Bangkok-based designer Taras Yoom, originally a medical professional, which explains something.

'It symbolically serves as significant

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guide and support, illuminating the nocturnal abyss, and extends physical protection, banishing the irrational fears that unite humanity,' he adds helpfully. So there you are. https://yoomoota.com/

SAD CONCLUSIONS The LIA Laboratory has helped the BBC with a programme investigating the effectiveness of SAD (seasonal affective disorder) lamps.

Any lamp can be marketed as a SAD light, and there is no requirement for them to be registered as medical devices. The three lamps selected by the BBC team and trialled by the LIA Laboratory were at low, middle and high price points.

They were tested for their UV output, colour temperature (to confirm they were within one per cent of their claims of being close to natural light) and lux levels, and also how far users need to be from the lamp to benefit from the effects. It is recommended that SAD lamps have a brightness level of 10,000 lux to mimic outdoor light.

All three lamps passed the tests, but LIA CEO Ayça Donaghy told viewers that the lowest price point product actually performed best.

The NHS estimates that SAD affects around 2m people in the UK and more than 12m people across northern Europe.

T&P APPOINTMENT

Neethu Susan George has been appointed as the new technical secretary for the SLL’s technical and publications committee.

Neethu is a specification manager and wellness advocate for Middle East North Africa and India at Lamp Worktitude for Light (Spain). She has an MSc Energy from Heriot-Watt University, and WELL AP and LEED Green Associate credentials.

'With Neethu joining the T&P committee we are bringing an international dimension to our published work,' said T&P chair Sophie Parry. 'This will help develop SLL recognition outside of the UK, as we do have a significant international regional membership.'

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March/April 2024

SLL Young Lighter 2023

WELL CONNECTED Teresa Aguilar Carrasco, SLL Young Lighter 2023, summarises her winning paper on the first parametric tool to quantify the effect of light on human health ight not only affects vision but also human health due to its influence on circadian rhythms, endogenous cycles through which humans have adapted to the light and darkness phases that are caused by the movement of the Earth.

Circadian rhythms have a slightly longer than 24-hour period so, due to the lag with the Earth's light and darkness cycles of 24 hours, they must be synchronised through external signals called Zeitgebers, the most important of which is natural light. However, due to our current way of life, people spend most of their time inside buildings, where the exposure to natural light is insufficient, and electric light is necessary.

For this reason, an adequate design of lighting conditions, both natural and electric, is essential in architectural conception. But for that, we need to know how light, both natural and electric, affects our health. Light doesn’t affect vision and the circadian system

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Fig 1: CircaLight plugin for Grasshopper

in the same way, as both systems have different spectral sensitivities. Therefore, the metrics that quantify the influence of light on both systems are also different.

There are several metrics that quantify the effect of light on human health such as circadian stimulus (CS), equivalent melanopic

� Fig 2: available lighting plugins for Grasshopper focus on visual comfort and energy efficiency, hence the need for a new plugin to assess the effect of light on circadian rhythm

Twitter: @sll100

lux (EML) or melanopic/photopic ratio (M/P ratio or MR). Although there are different types of software that calculate them, they are separate from the rest of lighting simulation or energy performance tools, analysing the different metrics independently, so the integration of all these metrics into a single software is essential.

In contrast, a major development is being observed in the field of software focused on the influence of light solely on visual comfort. One of the main advances is the increase in lighting parametric tools.

The advantage of parametrisation is that it allows multivariate complex analyses to be carried out taking into account a considerable number of parameters.

Among parametric tools, Grasshopper is a plugin within Rhinoceros, a threedimensional modelling software used in industrial design or architecture. It is a visual programming language for generative algorithms and one of the main benchmark tools for parametric design. Grasshopper enables lighting parametric workflows incorporated from different calculation engines, allowing complex and accurate calculations to be processed in a more efficient way.

There are different lighting plugins for Grasshopper such as Climate Studio or Ladybug Tools but all of these are focused on visual comfort and energy efficiency.

There is no parametric tool that quantifies the effect of light on human health. Hence the need to create CircaLight, a new plugin for Grasshopper which assesses the effect of light on circadian rhythms (Fig 1 and 2).

It has been developed using Visual Studio and the C programming language. It incorporates tasks ranging from modelling a specific space to calculating and visualising different metrics that quantify the effect of light on circadian rhythms.

First, it enables the creation of the calculation model based on defining

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SLL Young Lighter 2023

March/April 2024

parameters such as room dimensions, window locations and dimensions, furniture, and the colours of different surfaces. With the built model, and in order to calculate the various metrics related to circadian stimulus, it is necessary to know two variables: illuminance levels and the spectral power distribution (SPD) of the lighting source.

Regarding the first variable, illuminance levels, it must be noted that this plugin is not a lighting simulation tool. Therefore, it is necessary to turn to other plugins that are, and have incorporated a calculation engine like Radiance, such as Ladybug Tools or Climate Studio. The advantage of this plugin is that it allows the integration of these tools into a single workflow, eliminating the need to use different software simultaneously.

As for the second variable, the spectrum, the plugin enables the calculation of the SPD for different natural and electric light sources, as well as for surface reflectance.

One of the advantages or innovations of this tool is that it allows the calculation of the resulting spectrum received by our eyes through the combination of natural and electric light, considering the influence of surface reflectance.

With these variables, it is possible to calculate various metrics related to circadian rhythms. There are different theories and mathematical models to determine the effect of light on circadian rhythms, depending on the retinal photoreceptors taken into account: the circadian stimulus, the equivalent melanopic lux, or the M/P ratio mentioned above. There is no consensus on which one should be used, so this tool therefore allows the calculation of all of them in the same process, without resorting to different tools. Finally, the plugin allows the visualisation of the results.

This workflow (Fig 3) translates into the development of components to carry it out.

Grasshopper plugins are composed of components. CircaLight has been created using 21 components (Fig 4). Six of them are for the model creation, while 10 are for defining the resulting spectrum received by the eyes: some focus on defining the reflectance spectrum, others on defining the spectra of both natural and electric light sources, and the others on the combination of all spectra. In addition,

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Fig 3: workflow developed

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Fig 4: components of CircaLight

three components are dedicated to calculating the three metrics mentioned before, and two of them are used for the visualisation of the results.

The CircaLight plugin allows for model building in a parametric way. The parametric model creation is part of a single workflow, unlike other software where the model is created separately and then imported. This ensures a speedier calculation of circadian rhythm metrics as they are measured based on specific parameters which can be changed easily without the need to build a new model, involving, say, the alteration of dimensions, position and orientation of windows, or furniture position.

As mentioned earlier, CircaLight is not a lighting calculation tool; daylight and electric light simulations tools are required. The components seen before and used for model creation directly connect with these components, which in this example are from

Ladybug Tools, but could be from any other lighting calculation plugin. The illuminance results from both natural and electric light connecting directly with CircaLight components. This connection is necessary for calculating the resulting spectral power distribution from the combination of natural and electric light, and the influence of surface reflectance, and for calculating the different circadian metrics.

To assess the applicability of this tool, it has been used in an intensive care unit (ICU) at a hospital in Seville (Fig 5). The healthcare staff in the ICU work rotating 12-hour shifts, which can disrupt their circadian rhythms and lead to various health issues. Therefore, controlling electric lighting to promote synchronisation is crucial.

The ICU consists of a central area where the healthcare personnel work, surrounded by patient rooms or boxes. This tool allows for the calculation of different configurations of electric lighting in combination with natural light to assess their impact on health throughout the day. Once the circadian metrics are calculated, these results can be displayed on the architectural floor plan for better interpretation, along with the illuminance results obtained from other plugins.

CircaLight enables the visualisation of values obtained at each calculation point using colour scales

'The advantage of this plugin is that it allows the integration of these tools into a single workflow, eliminating the need to use different software simultaneously'

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March/April 2024

SLL Young Lighter 2023

� Fig 5: 3D model of the ICU in a Seville hospital and visualisation of the circadian stimulus results

customisable in colours and ranges.

Different lighting schedules for the intensive care unit have been created using CircaLight (Fig 6). They display both the levels of horizontal illuminance throughout the 24 hours of the day and the colour temperature of the light source.

The first graph corresponds to the schedule of a dimmable system. The second represents a tunable white system with two channels: warm white and cool white.

The third corresponds to a multispectral or multichannel system that includes an additional blue and amber channel. The schedules have been created considering two 12-hour work shifts: from 8am to 8pm and another from 8pm to 8am.

These schedules are created taking into account the established minimum thresholds for both horizontal illuminances, to ensure adequate visibility, and circadian stimulus to promote proper synchronisation. Although the thresholds are not always reached due to the need to consider the users' needs and satisfaction, it is observed that the achieved circadian stimulus closely resembles the recommended values throughout the day.

Therefore, the capability to calculate various circadian metrics within the same workflow used for illuminance calculations, along with the option to visualise any of the results, provides significant assistance in achieving compliance established LEAD and WELL certifications. This feature allows for both a visual and quantitative assessment of whether the minimum or maximum levels set by the standards are achieved.

Twitter: @sll100

� Fig 6: different electric lighting configurations for the unit

� Fig 7: tunable white electric lighting implemented in the ICU

The configuration of the electrical lighting in the ICU created by the tool has been implemented in reality and is now in operation (Fig 7). Three different times of day are shown with different spectra and possible intensities, using a biodynamic lighting system. Therefore, the plugin becomes a useful tool for designing healthy spaces, spaces that take care of us all.

Teresa Aguilar Carrasco is an architect, graduating from the University of Seville in 2019. She is now a researcher at the Department of Architectural Construction at the Higher Technical School of Architecture of Seville, and studying for a PhD in architecture

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Circular economy

March/April 2024

GOOD AS NEW Arup's green award-winning office refurbishment proves an exemplar of collaboration and carbon reduction he refurbishment of Arup's sixth floor office at Piccadilly Place, Manchester, also involved an expansion to the seventh floor. A key objective was to reduce embodied carbon by renovating or repurposing furniture and equipment on both levels to provide an exemplar for clients. The project recently won both Platinum and Green Build Back Better Awards.

The scheme involved upgrading the existing TC-L luminaires to LED, so Arup approached The Regen Initiative, which specialises in lighting remanufacture. Conceived by F Mark and Coco Lighting, and founded in 2021, The Regen Initiative mainly uses TM65 to assess the carbon avoidance associated with remanufacturing existing lighting instead of replacing with new.

F Mark designs and engineers the solutions, Coco manufactures, tests, warrants and sells the solution to the client.

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'It came about as a result of seeing that individual OEMs were creating their own strategy for remanufacturing their own luminaires and realising that there were no companies offering this at a holistic, project level,' says Simon Fisher of F Mark/ Regen. 'Our process is open and collaborative, and we welcome project opportunities with multiple lighting OEMs and installers to deliver sustainable, circular solutions. We will always seek to approach the original OEM to see if they wish to be involved in a remanufacturing project.'

Arup collaborated with Regen on the design, prototyping and testing on-site of the retrofit solution to ensure the optical performance could be maintained, to define a specification for light quality, and to integrate smart wireless lighting controls to replace the existing DALI system which was unfit for purpose.

As part of a turnkey solution, the LED retrofit upgrade of the 214 existing TC-L fluorescent lighting was completed out of hours by Regen associates Challenger Lighting Services to minimise disruption to Arup’s daily operations in the office. Along with the rebuilt LED retrofits, which were remanufactured offsite, the lighting levels were balanced to meet the client’s exact specification. The emergency lighting provision was also upgraded to be compliant with regulation and the whole project was fitted with wireless controls from Tridonic UK. Overall, 85 per cent of the original product was retained. The remanufacturing and retrofit of the fixtures has resulted in a 72 per cent energy reduction and the avoidance of 5554kg of CO2e being produced in comparison with the replacement of existing luminaires with new. The reduction in power density resulted in 5W/sqm for LED, compared to the fluorescent density at 13W/sqm.

The Tridonic/Casambi wireless upgrades also meant that PIRs and meeting room switch plates have been replaced. Regen

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Circular economy

'The collaboration between The Regen Initiative and Arup has really moved the dial on the amount of carbon and money saved'

engaged the services of Atrium to supply these components and commission all wireless lighting towards the end of the project. The emergency lighting provision has also been upgraded to be fully DALI auto-test compliant.

'The resulting green credentials for this project really speak for themselves,' says Fisher. 'We knew what we could do to remanufacture the old fittings to make them LED-ready, and using technology from Tridonic UK and Casambi to provide wireless controls, dimming and emergency lighting compliance, were all key parts of the project deliverables for us.

'But what has been truly inspiring about this project is the collaboration between The Regen Initiative and Arup to evolve the scope of work so that we could really move the dial on the amount of carbon and money saved as a result of these innovative

Twitter: @sll100

green techniques being deployed.'

The carbon avoidance calculated was only direct embodied carbon related to material retention and eliminating waste, adds Fisher.

'As we used daylight linking and PIR sensing, there will be operational carbon benefits over and above those which we have calculated and published.'

'We have been promoting the lighting and circularity agenda for some time,' says Richard

Morris, lighting design leader for Arup’s Manchester office. 'We were keen to put this into practice and working with The Regen Initiative gave us the opportunity. Now, having been through the process, with no disruption to our daily work and validation of the energy and carbon savings, we can share our experience with our clients with confidence and promote luminaire refurbishment as a realistic proposal.'

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Technology

March/April 2024

SMALL WONDER MicroLEDs: two new reports assess their future hile microLEDs are not new (they were invented in 2000 and the first viable format was realised in 2009) they remain a nascent technology. However, two recent reports, a book and a forthcoming event all indicate their potential significance.

Primarily viewed as a possible replacement for LCD and OLEDs, microLEDs are a flat-panel display technology consisting of arrays of microscopic LEDs forming individual pixel elements. Each pixel consists of individual red, green and blue LEDs as independently controllable sub-pixels.

'MicroLEDs today have an edge length of about 50µm,' says Julia Halasz, managing director of ams-OSRAM International. 'We don’t think that this size will have a disruptive market effect, so we are focusing on chip edge lengths of 10µm and less. Just to give you an idea, there is enough space on a one-euro coin for more than four million microLEDs, that’s four million separate functioning LEDs.'

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MicroLEDs are regarded as offering improved performance – mainly in terms of efficiency, lifetime and brightness – and the key applications envisaged for them are display (small and large scale), wearable technology (smartwatches) and automotive applications.

However, microLED displays do more than cater to existing applications, says the IDTechEx report, Micro-LED Displays 2024-2034: Technology, Commercialization, Opportunity, Market and Players – they unlock new possibilities.

'With features like seamless tiling, these displays enable standard microLED modules to form larger, customised shapes with even more flexible features. The integration of sensors adds an interactive dimension to displays, paving the way for a future of immersive experiences,' according to the report.

'It promises to combine some of the really important features such as high image quality, brilliant colours and good readability even in bright sunlight,' says Halasz. 'For this you need a technology that offers a wide colour gamut, high contrast, wide viewing angles, high pixel density and fast refresh rates. That is exactly what microLEDs can provide, and better even than incumbent technologies.'

However, it is very early days and cost remains prohibitive to widespread adoption, continues the IDTechEx report. 'Achieving extremely high resolutions with small microLEDs remains technically demanding and costly... While the promises of microLEDs are remarkable, there are challenges to overcome on the path to their widespread adoption.'

Reminiscent of the early-days flagship installations of OLEDs, there has been an application in the W Hotel in Taipei. An old Philips OLED installation (You Fade to Light by rAndom International creative studio) comprised 2000 modules, each lighting up as a response to people moving in front of it. The installation had started to fail and fade (somewhat ironically) and Taiwanese microLEDs specialist PlayNitride collaborated with the hotel to replace the OLED panels with microLED versions.

Each single module included more than 14,000 microLEDs, with a total of over 30 million microLEDs. 'The main challenge was to recreate the look of the OLED panels, the light output and the uniformity,' according to PlayNitride.

'The microLEDs achieved this and even achieved better performance.'

A second report from the MicroLED Industry Association (a collaborative consortium of companies, academia and other organisations sharing information, resources and tools) agrees though that in spite of billions of dollars already invested in R&D in recent years, 'mass production is still years away with several unsolved challenges to overcome... It remains to be seen which processes and technologies will ultimately become prevalent. The number of displays currently being sold is very small, as high manufacturing costs and low production capacity limit the use of microLEDs in most markets.'

However, it points out that the display industry is a large one, estimated at tens of billions of dollars a year, and producing billions of panels annually.

'Historically, every new technology has taken a long time to mature, and it is no surprise that microLED technology is no exception' it concludes.

• Micro-LED Displays 2024-2034: Technology, Commercialization, Opportunity, Market and Players was published in December by IDTechEx and authored by IDTechEx research director Dr Xiaoxi He (www.

IDTechEx.com) • MicroLEDs 2023: State of the industry and future roadmap was published in December by the MicroLED Industry Association (MIA) • The MicroLED Handbook 2024 has recently been published by Metalgrass (MicroLEDInfo.com) • The MicroLED-Connect exhibition and conference will take place in Eindhoven, The Netherlands, on September 24-26, 2024 (www.microledassociation.com/)

What are microLEDs? MicroLEDs are a display technology based on tiny LED devices that are used to directly create colour pixels. Inorganic semiconductor microLED (μLED) technology was first invented in 2000 by the research group of Hongxing Jiang and Jingyu Lin of Texas Tech University while at Kansas State University. The first highresolution and video-capable InGaN microLED microdisplay in VGA format (high resolution video standard) was realised in 2009 by Hongxing Jiang and Jingyu Lin, and III-N Technology.

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Tribute

ORCHESTRATED ‘L SPACES Jill Entwistle on the Finnish architect Juha Leiviskä, master of geometry and light, who died at the end of 2023, aged 87 Twitter: @sll100

eiviskä’s light is an oblique light that both hits vertical surfaces directly and is reflected to create experiences of layered light with a distinct feeling of depth,' said the judges of the Daylight Awards, of which he was a laureate in 2020. 'His light does not only illuminate surfaces, it appears to originate and exist vibrantly in the architectural space itself.'

According to Richard Weston, architectural author and former professor of architecture at Cardiff University, Leiviskä’s fascination with light

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Arno de la Chapelle

was triggered during a month-long history studyvisit to southern Germany and Italy during which he experienced the interiors of key rococo churches. 'The wealth of decoration can easily blind us to the sophistication of the complex, three-dimensional interplay of and from light, and it was here, Leiviskä says, that he first fully understood the idea of an interior as "an instrument for light to play on".'

While still a student Leiviskä toured the work of fellow Finnish architect Alvar Aalto on his bicycle and developed his admiration for Aalto's handling of light, with its complex layering and use of hidden sources of daylight.

His architectural style combines that sensitivity to the drama of natural light in German Baroque churches with the principles of composition of Dutch De Stijl architecture of the 1920s (part of a more general artistic and philosophical modernist movement that included artist Piet Mondrian and architect Gerrit Rietveld).

Born in 1936, the son of an engineer and teacher, Leiviskä studied architecture at Helsinki University of Technology, qualifying as an architect in 1963. Choosing architecture over a potential career as a concert pianist, he established his own office in 1964, while also working as a teaching assistant at the university. He had been in partnership with fellow architect and academic Vilhelm Helander since 1978.

He received his first critical attention when he and architect Bertel Saarnio won the architectural competition for the Kouvola Town Hall (1964–68), considered one of the most significant public buildings in Finland during the 1960s. His international reputation grew during the subsequent decades with designs for churches in different parts of Finland, notably in 1984 with the completion of a new church and parish centre in Myyrmäki in the city of Vantaa, part of the Helsinki Metropolitan Area.

'Leiviskä’s is a Lutheran not Gothic light – no stained glass or overt symbolism,' says Weston of Myyrmäki church. 'The light is uniformly white and the only hints of colour, save for the muted greys and buffs of pews and floors, and gleam of brass in the light fittings, is an ethereal blue like liquid air that is materialised and intensified in the banding of the fabrics above the altar.'

An integral part of the architecture of Leiviskä's churches are the lamps designed by the architect himself, based on the principles developed by Danish designer Poul Henningsen for his iconic PH-lamps. At Myyrmäki, says Weston, they are 'suspended in clusters at various levels throughout the interior to form an aerial archipelago

March/April 2024

Jussi Tiainen

Tribute

� Top: Mannisto Church, Kuopio. Above: Myyrmaki Church, Vantaa

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March/April 2024

Tribute

'An especially delicate effect in his light articulations is the use of reflected colour, which makes colour a constantly changing, kinetic and pulsating phenomenon. The colours strengthen and weaken, appear and disappear according to the intensity and direction of sunlight, like breathing'

Arno de la Chapelle

– Daylight Awards judges, 2020

� Vallila Library, Helsinki: arguably Leiviskä's finest secular project

that adds voluptuous, organic notes'.

Myyrmäki was the building through which William JR Curtis, who has written seminal texts on Finnish modernism, 'discovered' Leiviskä’s work in 1991. He included the church in his book Modern Architecture Since 1900 (Phaidon), considered a classic.

'Genuine architecture communicates before it is understood,' wrote Curtis in his obituary of Leiviskä. 'It touches the mind and the senses at levels beyond words and out of range of theoretical justifications. I was overwhelmed immediately by the sublime light, vibrant space, and “musical” rhythms of floating planes. I was convinced that I was in the presence of a masterpiece.'

Other major buildings include Männistö Church at Kuopio (1986–92) – like Myyrmaki, says Curtis,

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'distinguished by [its] sublime fusion of light, sacred space and geometry' – the German Embassy in Helsinki (1995), the Dar al-Kalima Academy in Bethlehem (2002), Villa Lepola at Espoo (1998), and the Swedish School of Social Sciences in Helsinki (2009).

Although less grand, the design of the library and nursery in suburban Vallila (1984-91) remains, arguably, Leiviskä’s finest ‘secular’ project, according to Weston: 'Externally the building is modest in scale and almost recedes into its setting; internally, however, the library is unexpectedly grand, its multiple spaces unified by a play of light every bit as masterly as that in Myyrmäki.'

Among numerous awards and accolades, Leiviskä was made a member of the Royal Swedish Academy of Fine Arts in 1991, and in 1994 he was made an honorary fellow of the American

Institute of Architects. In 1997 he followed Alvar Aalto and Reima Pietilä in becoming the architecture Member of the Academy of Finland, and in 2008 he was awarded the international Antonio Feltrinelli Prize by the prestigious Accademia Nazionale dei Lincei in Rome, as well as a RIBA International Fellowship.

'Architecture is closer to music than to the visual arts,' wrote Leiviskä in Architecture and Urbanism (April 1995). 'To qualify as architecture, buildings together with their internal spaces and their details, must be an organic part of the environment, of its grand drama, of its movement and its spatial sequences. To me a building as it stands "as a piece of architecture" is nothing. Its meaning comes only in counterpoint with its surroundings, with life and with light.'

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LR&T essentials

March/April 2024

PUBLIC EYE Iain Carlile looks at three papers in the recent special early career research edition of Lighting Research and Technology, all focusing on the exterior urban environment owards the end of 2023, a special edition of Lighting Research and Technology (LR&T Vol 55 no 7-8) was published, showcasing the work of early career researchers in lighting. All of the lead authors were PhD candidates at the time of submission of their papers. The following looks at the first three of the 10 papers published in this edition, investigating different aspects of public realm lighting.

Flores-Villa et al’s paper examines the relationships between the soundscape and lighting in the urban environment. During an exploratory field study, a soundscape and lightscape protocol was implemented to gather both objective and subjective data. A total of 46 people participated in the sound/light walk (26 female, 20 male; age range: 19-52 years; median age: 23). The walk took place around the historical sites of the Colosseum

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� Luminance recording of Colosseum in daytime conditions. Image (a) is the result obtained from the photometer; image (c) is for illustration purposes, showing how equipment was used to record measurements (Flores-Villa et al)

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and Fori Imperiali in Rome, Italy.

The participants assessed the quality of both the soundscape and lightscape immediately before and after sunset on 22 April 2021, recording their responses via a questionnaire. Separate measurements were taken of acoustic parameters (A-weighted equivalent sound level, loudness, sharpness, roughness) and lighting parameters (luminance, colour rendering index and correlated colour temperature).

The results of the study revealed that there was little variation in the acoustic parameters measured before and after sunset. However, from the participants' perceptual data, changes were observed. This suggests that the visual changes observed through the changing lit environment before and after sunset influenced soundscape perception. The authors propose that if the limitations of the study are addressed, this procedure could provide greater insight into people’s perception in cultural locations, improving urban design and enhancing visitor experience.

Also looking at the public realm, Henning et al studied the change in social interactions in public squares under daylight and electric light during the hours of darkness. A field study was conducted in two local public squares in different neighbourhoods within Malmö, Sweden. Each square had a different electric lighting scheme, one with asymmetric luminaires using metal halide lamps (2800K) and the other with omnidirectional fittings with high-pressure sodium lamps (2000K).

Observations were made of people's movements and stationary activities, recorded at the same times of day in the weeks before and after clock changes due to daylight savings, thereby allowing a comparison of activity in both daylight and after dark. In addition, lighting conditions were captured with HDR and aerial photography.

It was found that the square lit by the asymmetric metal halide luminaires had a decrease in stationary activity after dark, while the square illuminated by omnidirectional HPS luminaires had an increase in stationary activity after dark. These results suggest that the patterns of user behaviour

were influenced differently by the different electric lighting schemes, identifying a need to further understand users’ experiences after dark.

Investigating a different aspect of public realm lighting, Hamoodh et al present a study into interpersonal safety evaluations during night-time.

Following on from a pilot study that showed the ability to see an approaching person’s face and hands was important in the personal evaluation of safety, an experiment was conducted to identify whether the face or hands was the most important identifier.

The experiment consisted of 44 participants (22 female, 22 male; age range: 18-34 years) evaluating their sense of safety when shown photos of approaching people in a night-time scene. The evaluation was undertaken while walking a treadmill to simulate the cognitive task. The photographs used showed varying exposure and concealment of the approaching person's face and hands. Category rating and paired comparison procedures were used to record results.

From the results, the authors conclude that the face is more important than hands for evaluating the intent of other pedestrians at night.

Iain Carlile, FSLL, is a past president of the SLL and a senior associate at dpa lighting consultants Lighting Research and Technology: OnlineFirst In advance of being published in the print version of Lighting Research and Technology (LR&T), all papers accepted for publishing are available online.

SLL members can gain access to these papers via the SLL website (www.sll.org.uk) Exploring relationships between soundscape and lightscape perception: A case study around the Colosseum and Fori Imperiali in Rome L Flores-Villa, T Oberman, C Guattari, F Asdrubali, M Frascarolo, GE Puglisi, A Astolfi and F Aletta User behaviour in public squares after dark VKR Hennig, N Gentile, S Fotios, C Sternudd, and M Johansson Visual cues to interpersonal evaluations for pedestrians K Hamoodh, S Fotios and C Cheal

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March/April 2024

Top five

COUNTIES SET ost of my life I have lived in either London or Oxfordshire, and I’ve spent plenty of hours travelling around and between the two. So it seems appropriate in my role as the SLL regional representative for Home Counties North West (HCNW) to consider my top five for the region.

HCNW is one of the four CIBSE regions covering London. It starts roughly at Trafalgar Square, covering a wide segment from the Thames Valley through the Cotswolds, Chilterns and right round to St Albans. From London’s West End, 1960s Milton Keynes, the science and industry clustered along the Oxford-Cambridge Arc, and many historic towns in between, the built environment varies immensely.

And yet there are also beautiful pockets of rural darkness, where perhaps just a lonely sodium streetlight casts its soft glow on a forgotten stone wall. For variety in lighting, it is hard to beat.

Chris Dicks, winner of the 2023 SLL's Regional Award, looks to his home turf

3 The Thames Lido, Reading This lido dates from 1902, when the borough constructed an open-air ladies bathing pool, fed straight from the Thames.

From the 1970s the site was derelict, until its renovation in 2017 by the team behind Bristol’s successful Clifton Lido, and architects Marshall and Kendon. It now boasts a heated outdoor pool, steam rooms, saunas, spa and restaurant. The beautiful lighting was designed by Connected Light, Bristol. And happily the pools are no longer directly fed from the river.

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Thames Lido

Chris Dicks, CEng MSLL, is an associate director at CBG Consultants, and the SLL Home Counties North West regional representative

4 Unity Place, Milton Keynes Designed by LOM Architecture, this BREEAM Outstanding office for 3500 workers, with public food court, opened in September 2023.

Designer Lightivity has created a spectacular external dynamic facade lighting scheme, a new landmark for the city. Internally, lighting helps create distinct zones throughout. But what really stands out to me is the impressive harnessing of daylight: there are big statement atriums coupled with great attention to detail. User groups provided input into the window blind design, with nine iterations before the final version. Detail like this matters.

Morley von Sternberg

The Hoover Building For those arriving into London by road, the 1930s Hoover Building factory on the A40 signals the approach of the city. Its fine Art Deco-inspired illumination is a welcome beacon on this otherwise dreary stretch of dual carriageway. After manufacturing ceased in the 1980s, the building was granted a Grade II* Listing to protect it. Several changes of use and vacant periods followed (and Imagination's famously acid green lighting). In 2018 Interrobang Architects oversaw its conversion into 66 apartments, with a striking new lighting scheme delivered

by Swann Lighting.

Chris Dicks

Paddington Station, London Could there be a more impressive gateway to the west than Brunel’s masterpiece of Paddington Station? Its construction long predates the use of electric lighting, and by day the platforms are bathed in daylight.

At night it sparkles subtly, thanks to a recent upgrade of the four train sheds by WSP, Oxford Architects and iGuzzini.

Should your train be delayed, simply retreat up to the Mad Bishop and Bear for a pint and some people-watching on the concourse below.

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Chris Dicks

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Chris Dicks

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5 The Radcliffe Camera, Oxford One of Britain’s most iconic sights, the Radcliffe Camera was finished in 1749, and forms part of the university’s Bodleian Library. Briefly lit one night by DPA for Oxford’s SLL Night of Heritage Light in 2017, it has otherwise been left in darkness on the outside, with only gentle light spill from its windows and the street. It is all the more beautiful and mysterious for that; seeing it shrouded in mist late on a winter evening is a timeless experience.

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Events

2024

For details of all upcoming webinars, go to: www.cibse.org/societyof-light-and-lighting-sll/sll-events/upcoming-webinars-and-onlinecontent For previously recorded CPD webinars (including regional webinars), go to: https://www.cibse.org/get-involved/societies/society-of-lightand-lighting-sll/sll-events/on-demand-webinars-past-presentations

EVENTS LIGHT + BUILDING Date: 3-8 March Venue: Messe Frankfurt https://light-building.messefrankfurt.com DARC AWARDS Date: 27 March Venue: Fabric, London EC1 https://darcawards.com/ SLL AGM, AWARDS AND PRESIDENT'S ADDRESS Date: 14 May Venue: Leeds Art Gallery sll@cibse.org DESIGN LONDON Date: 21-23 May Location: Clerkenwell www.designlondon.co.uk/ GUANGZHOU INTERNATIONAL LIGHTING EXHIBITION (GILE) Date: 9-12 June Venue: China Import and Export Fair Complex https://light.cn.messefrankfurt.com/china/en.html IALD ENLIGHTEN EUROPE 24 Date: 21-22 June Location: London www.iald.org LIGHT2PERFORM 24 Date: 13-14 November Venue: ExCeL, London www.build2perform.co.uk/light2perform

AVAILABLE WEBINARS INCLUDE DIFFUSE CONVERGENCE Speaker: Guinter Parschalk, Studioix, Brazil Lighting designer Guinter Parschalk talks about his professional trajectory through visual communication, fashion, packaging design and product design, culminating with lighting design, which in his view is the area that unites all the previous ones EVIDENCE-BASED LIGHTING DESIGN FOR PEOPLE IN SMART CITIES Speaker: Dr Navaz Davoodian, senior lighting researcher at UCL. Hosted by Guy Kornetzki The importance of evidence-based lighting design that prioritises the wellbeing of people in creating smart cities

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