Light Lines Nov/Dec 19

LIGHT LINES

BODY OF EVIDENCE

Circadian lighting: what we know and what we need to know

HEALTHY INTEREST

The new LightBytes on light and wellness

SECRETARY

Brendan Keely FSLL bkeely@cibse.org

SLL COORDINATOR

Juliet Rennie Tel: 020 8772 3685 jrennie@cibse.org

EDITOR

Jill Entwistle jillentwistle@yahoo.com

COMMUNICATIONS

COMMITTEE:

Linda Salamoun MSLL (chair)

Iain Carlile FSLL

Jill Entwistle

Chris Fordham MSLL

Rebecca Hodge

Eliot Horsman MSLL

Stewart Langdown FSLL

Bruce Weil

Gethyn Williams

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 LL1 2020

IS 15 NOVEMBER

PUBLISHED BY

The Society of Light and Lighting

222 Balham High Road

London SW12 9BS

www.sll.org.uk

ISSN 2632-2838

© 2019 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

PRODUCED BY

If there is one theme that pulses through this issue it is that of the relationship between light, and human health and wellbeing. It is the theme of the new LyteBytes series (see Well Aware, p11), crops up in the news (see p4) and most substantially occurs in Karen van Creveld’s examination of the subject (The Right Wavelength, p5), based on her ongoing research. This year’s recipient of the Jean Heap Bursary, van Creveld has laid the ground to her study with a rigorous analysis of just what we mean by ‘circadian lighting’.

FROM THE EDITOR JILL

By now a lot of people have heard about circadian rhythms and, to a greater or lesser degree, have understood that we ought to pay attention to how lighting affects them. The introduction of the WELL standard validated concerns that this was something that should be heeded in working environments. But there has been a tendency to believe that if only everyone had dynamic lighting that changed colour temperature in their

workplace everything would be fine. But as van Creveld points out, this is trampling all over a number of complex considerations and unknowns. ‘Exclusion of some of the constituent wavelengths of full spectrum light, or indeed, preferential doctoring of the light environment to influence certain known biological responses, may result in inadvertent and unwelcome effects elsewhere,’ she says.

‘An additional concern is that there is the danger of creating “unnatural” visual environments that may inadvertently impact other core mechanisms.’ It is far from a simple matter of blue light at the right time equals happy people.

CURRENT SLL LIGHTING GUIDES

SLL Lighting Guide 0: Introduction to Light and Lighting (2017)

SLL Lighting Guide 1: The Industrial Environment (2012)

SLL Lighting Guide 2: Lighting for Healthcare Premises (2019)

SLL Lighting Guide 4: Sports (2006)

SLL Lighting Guide 5: Lighting for Education (2011)

SLL Lighting Guide 6: The Exterior Environment (2016)

SLL Lighting Guide 7: Office Lighting (2015)

SLL Lighting Guide 8: Lighting for Museums and Galleries (2015)

SLL Lighting Guide 9: Lighting for Communal Residential Buildings (2013)

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 Design Guide (2015)

SLL Lighting Guide 13: Places of Worship (2014)

SLL Lighting Guide 14: Control of Electric Lighting (2016)

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)

Guide to Limiting Obtrusive Light (2012)

Code for Lighting (2012)

Commissioning Code L (2018)

SLL Lighting Handbook (2018)

FROM THE SECRETARY

We are delighted to have the new publication LG2: Lighting for Healthcare Premises available to download by members and PDF/hard copy purchases. We would like to take this opportunity to thank the publication’s lead author, Nicholas Bukorovic, and the task group: Andrew Bissell, Jemima Unwin, Nigel Monaghan and Tim Bowes. Mike Ralph, principal engineer at National Health Service Improvement, has kindly written the foreword for the guide.

In September we exhibited at darc rooms at the Old Truman Brewery, London. It was great to see old friends and new, and we even picked up some new members. Paul Ruffles held a workshop on publications, namely the Lighting Handbook, which was well received.

Also in October, Juliet Rennie and I returned to Light Middle East where the SLL exhibited, promoting publications and membership, as well as hosting Ready Steady Light ME for the fourth consecutive year. Many thanks to all who came to visit us at the stand and took part in the competition.

The brand new peer-reviewed LightBytes series is up and running (see p11) with the first event taking place in Birmingham in October. The theme of the day is People Space Time Place, focusing on the issues of light and wellness. While there is still a very apparent need for further research and conclusive evidence concerning circadian lighting or the application of lighting for wellness, there is no substitute for daylight in relation to the stimulation of the circadian system and support of human health.

Each of the LightBytes events is split into four sessions, with speakers delivering bitesized, peer-reviewed presentations. Big thanks to the speakers: Eleanora Brembilla from Loughborough University, Richard Caple from Thorlux, Roger Sexton from Xicato and Graeme Shaw from Zumtobel. LightBytes is also sponsored by Soraa.

The day provides an opportunity to add 4.5 hours of CIBSE-accredited CPD to your record. In the coming months the series will visit Dublin (21 November),

Manchester (30 January), Leeds (13 February), Bristol (26 March), Glasgow (23 April) and London (4 June). We encourage everyone to attend these sessions. At £50, including as much tea and coffee as you can drink and a lovely lunch, it is very good value for money.

We are pleased to confirm that the next Lighting Research and Technology Symposium: Applying Light for Human Health will take place on 18 June 2020 at University College London. We are currently communicating with potential speakers and will confirm the details very soon, but please do block out that day to attend the event, it will be unique of its type.

LuxLive and the Lux Awards are just around the corner, 13-14 November to be specific. We will again be exhibiting in a booth adjacent to the Lightspace Arena (Stand A40d). Please do come along for updates on publications and membership upgrading, or indeed just come along for a chat, our door is always open.

The Young Lighter 2019 final will take place in the Lightspace Arena in the afternoon of 14 November so please do come and support the presenters. The winner of the competition will be presented with their trophy and cash prize at the Lux Awards on the evening of 14 November.

Finally, CIBSE Build2Perform Live will take place at Olympia, London, on 26-27 November. A number of lighting papers have been received and we think the lighting session at the event will be superb. We hope to see you there.

‘There is no substitute for daylight in relation to the stimulation of the circadian system and support of human health’

SECRETARY’S COLUMN

THE RIGHT WAVELENGTH

Karen van Creveld, this year’s recipient of the Jean Heap Bursary, highlights both the limitations of some claims for ‘circadian lighting’ and identifies areas vital for further study

ONLY CONNECT

What does open lighting control really mean? Francesco Anselmo explains and analyses the different wireless technologies

WELL AWARE

The latest SLL LightBytes series focuses on light and wellness. Two of the speakers, Roger Sexton and Richard Caple, take one of the themes each to give a flavour of the issues covered

AROUND THE CLOCK

Iain Carlile singles out three of the latest Lighting Research and Technology papers whose themes range from night lighting to daylight

NEW SLL HEALTHCARE GUIDE AVOIDS PROMOTION OF ‘HUMAN-CENTRIC’ LIGHTING

The SLL has released new guidance for the healthcare environment. The latest version of Lighting Guide 2: Lighting for Healthcare Premises (LG2) replaces the 2008 edition. As well as updates to ensure it conforms to current practice, it also illustrates various ways of lighting the modern hospital and other clinical premises. The publication purposely does not offer guidance on biodynamic lighting which has been used experimentally in this type of environment.

‘The lighting industry has seen an increase in marketing related to lighting for health and productivity – ‘human-centric lighting’, ‘circadian lighting’ and so on – with products claiming to enhance performance and productivity, and to avoid disrupting sleep patterns,’ says Nicholas Bukorovic, chair of the LG2 task group. ‘This edition does not detail or promote these techniques, which will disappoint some, but these claims should be taken with caution and all such products should be carefully evaluated.’

The SLL Code for Lighting and BS EN 12464-1 acknowledge the importance of non-visual effects of light on health and wellbeing, but the SLL warns that research in this area is still very limited. The existence of beneficial effects due to changing the colour and level of electric light during the course of a day has yet to be unequivocally demonstrated, it says.

• The society has also released Factfile 15: the Importance of Glare and Calculating UGR. The free-download publication defines different types of glare and also looks at how it is quantified. It also examines whether UGR is still relevant.

For Lighting Guide 2: Lighting for Healthcare Premises (LG2): www.cibse.org/knowledge/knowledge-items/detail?id=a0q3Y00000GzaAJQAZ

For Fact File 15: www.cibse.org/society-of-light-and-lighting-sll/lightingpublications/free-downloads

ON THE LIGHTER SIDE...

If you thought that the idea of making a light out of a dried fish was pretty gross (see May/June 2017), it gets worse. Danish designer Kathrine Barbro Bendixen, founder of Studio KBB, creates intricate lighting installations using cow intestines. She cleans and reinflates them, creating translucent tubes that naturally curl around an LED lighting fixture.

POLLARD RECEIVES CIE AWARD

Nigel Pollard, FSLL, former chair of CIE-UK, has received the CIE’s Waldram Gold Pin Award at the 2019 CIE Quadrennial Session in Washington DC. The award is for ‘exceptional and outstanding contribution in applied llluminating engineering’. Among his many recognised achievements, Pollard’s Technical Report (No 150) has been seen as pivotal in the worldwide Dark Skies campaigns against light pollution.

Her latest piece is on show at Designmuseum Danmark until March 2020.

‘The Inuit used the intestines of seals to make anoraks, because the outside of the material is waterproof, and the inside is breathable,’ Barbro Bendixe told Dezeen.

‘The material GoreTex is also inspired by intestines.’ Nope, still not convinced.

RECORD-BREAKING GRANT FOR CIRCADIAN LIGHTING RESEARCH

The US-based National Institute on Aging is giving a record £3.1m to Dr Mariana Figueiro (pictured), professor and director at New York’s Lighting Research Center (LRC), to investigate if installing so-called ‘circadian lighting’ for elderly people can improve their sleep, perception and memory.

The NIA particularly wants to see if it helps individuals with mild cognitive impairment, a potential early stage of dementia. Sleep-wake disturbances are evident in 60 per cent of individuals with cognitive impairment. Figueiro will collaborate with Dr Sara Mednick, associate professor in the Department of Cognitive Sciences at University College Irvine, whose research focuses on the relationship between sleep and memory.

Disruption of sleep-wake and rest-activity rhythms are not only consequences of Alzheimer’s disease but may also drive the disease, says LRC. Recent research suggests a link between sleep disruption and the deposit in the brain of amyloid beta protein, which is associated with Alzheimer’s disease.

Dr Figueiro’s previous research has shown that tailored lighting delivering a high circadian stimulus significantly improved sleep, and reduced depression and agitation in people living with Alzheimer’s, compared to baseline and to the inactive condition.

‘Tailored lighting, when properly designed to deliver the correct amount of light at the right time, can positively impact health and wellbeing,’ said Figueiro. ‘We have seen firsthand the many benefits of lighting, but it’s important to get the right lighting to see the positive effects.’

THE RIGHT WAVELENGTH

The relationship of light to our health and wellbeing is now a key area of interest. Karen van Creveld highlights both the limitations of some claims and identifies areas vital for further study

Over millions of years of evolution, humans have adapted and thrived under a regular daily rhythm of bright daylight and true darkness. We have developed complex and fine-tuned biological mechanisms that allow us to anticipate and prepare for the varying demands of our environment over 24 hours, optimising our survival.

While for many years we have acknowledged that environmental light may exert influence over and above our visual system, scientific research is now beginning to decipher some of the physiological and neural mechanisms that lie behind these processes, aiding our understanding of the significance of light for our health and wellbeing. Areas where light is known to impact human biology include the circadian system, the arousal system (arousal being the physiological and psychological state of being alert, awake and attentive) and the affective (emotional) system.

Furthermore, the introduction of functional electric lighting around 100 years ago initiated a fundamental transformation in the design of our built environments and hence in our relationship to daylight. Nowadays we spend increasingly less time in bright, dynamic, exterior-lit daytime environments and instead occupy relatively low brightness, artificial and static indoor environments for much of the day. The impact of this change in behaviour on our health and wellbeing is receiving close attention, particularly following recent seminal discoveries about the physiology of the human eye and brain.

Around 20 years ago, scientists discovered the existence of a third class of photoreceptor cell in the human retina, termed the intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells contain the photopigment melanopsin which is distinct from the photopigments found within the rods and three types of cones.1 Melanopsin, when extracted, is maximally sensitive to electromagnetic radiation within the blue portion of the spectrum, with peak sensitivity around 480nm. 2 The ipRGCs are less sensitive than the rods and cones, and they respond at a slower pace, requiring

Nicolas Jossi

brighter light and longer exposure times to produce a response. 3

IpRGCs are a specialised type of ganglion cell and absorb light directly, in addition to serving as a conduit for light information travelling from the rods and cones to the brain via the primary optic tract (POT). IpRGC axons form a separate pathway, the retino-hypothalamic tract (RHT), linking the retina to several sites within the brain. The brain area that has so far been explored in relation to the circadian timing system is the suprachiasmatic nuclei (SCN) located within the hypothalamus.1

Importantly, more recent studies have agreed that all three classes of retinal photoreceptors (rods , cones and ipRGCs) are involved in both visual and circadian phototransduction. 4 However, as yet, the relative contributions of these various photoreceptors to stimulate diverse areas of the human brain under varying conditions, remains unknown.

Some areas where light affects our non-image-forming processes are better understood than others and thus have given rise to certain recommendations (from both academic and application practitioners) for types of lighting needed to maximise these impacts. In particular, the effect of shortwavelength blue light on aspects of our circadian system has received considerable attention. This rationale is based on the association between the ipRGCs (containing blue-sensitive melanopsin) and the hormone melatonin. Because of the relative ease of collecting and measuring circulating levels of melatonin in the human body, this measure is often used, in addition to providing information about the phase of the circadian system, as a proxy for the functioning of

the circadian system as a whole.

Light information signals reaching the SCN are conveyed to the pineal gland, where melatonin is synthesised from the neurotransmitter serotonin. Melatonin is released into the bloodstream when ambient light levels fade in preparation for sleep. This is the means by which time-ofday messages are conveyed to peripheral clocks throughout the body. Melatonin is also associated with other vital processes including growth and puberty. Manipulation of melatonin levels has been shown in animal studies to affect the growth of different cancer types, especially hormone-dependent breast cancer. 5,6

Exposure to light at night (LAN) suppresses the production of melatonin. Research into the threshold and spectral qualities of light needed for this effect have demonstrated that exposure to light in the blue portion of the spectrum, specifically at a wavelength of around 460nm, results in more effective suppression of melatonin, compared with polychromatic white light of the same intensity.7

Another area of interest is the impact on light on measures of alertness. Earlier studies showed that night-time exposure to white light over a wide range of illuminance levels, impacted measures of alertness, as assessed by subjective ratings, quantification of slow

eye movements (SEMS) and EEG analysis. All measures of alertness correlated highly with the degree of melatonin suppression and, furthermore, the extent of the alerting response was determined by the intensity of the light stimulus. 8

Since the spectral sensitivity of the circadian system as measured by melatonin suppression has since been shown to peak in the blue region of the spectrum, more recent studies have investigated the impact of blue light on alertness at night.7 One of the outcomes from this work is the claim that lower levels of short wavelength blue light will illicit the same alerting effects as significantly higher levels of polychromatic white light because of the underlying sensitivity of the ipRGCs to blue light.

However, these studies were conducted at night when melatonin levels are high. Studies by Vandewalle et al, using functional magnetic resonance imaging (fMR), looked at the impact of light on measures of alertness in rodents, conducted during the daytime, when melatonin levels are naturally low.9

The results indicated that the light signals from the ipRGCs project to various areas of the hypothalamus including the SCN, and from there to different parts of the brain associated with arousal (alertness), clearly suggesting that the impact of light on daytime alertness appears to be influenced by brain mechanisms other than melatonin suppression. 7

‘It seems counterproductive, and possibly even harmful, to exclude certain wavelengths of light when considering optimal illumination for overall health and wellbeing effects’

As yet, neither the pathways linking brain areas (that result eventually in cognition) nor their true impact on downstream functioning is clear. Importantly, the spectral qualities of light most efficient for eliciting a response from most of these mechanisms are currently unknown. Therefore, it seems counterproductive and possibly

p While we evolved as a diurnal species, daylight availability is no longer a defining condition for human activity

even harmful, to exclude certain wavelengths of light when considering optimal illumination for overall health and wellbeing effects.

Moreover, recent studies have shown that exposure to red light of 630nm can also increase objective and subjective measures of alertness, both at night and during the daytime.7,10 As the ipRGCs are insensitive to light in this region of the spectrum, it is suggested that the alerting effect of light may be due to the involvement of cone receptors sensitive to long-wavelength light. This work supports the view that in addition to the ipRGCs, rods and cones are also involved in non-image forming functions and, secondly, neural pathways other than those associated with melatonin suppression are directly involved in measures of alertness.

While targeted blue light exposure has been shown to be effective in some studies conducted under laboratory conditions,7 the problem that emerges is that this constitutes only a very small portion of the electromagnetic spectrum. Although daylight conditions vary with time of day, season and latitude, all daylight conditions contain varying proportions of all the wavelengths of the visible spectrum plus others. Exclusion of some of the constituent wavelengths of full spectrum light, or indeed, preferential doctoring of the light environment to influence certain known biological responses, may result in inadvertent and unwelcome effects elsewhere. An additional concern is that there is the danger of creating ‘unnatural’ visual environments that may inadvertently impact other core mechanisms.

My preferred approach is the application of full spectrum lighting, especially daylight wherever possible, as it satisfies known

mechanisms without adversely impacting others. In many respects, daylight is the ideal light source, but to date no comprehensive research has been undertaken to understand how much daylight we experience inside our built environments. It seems imperative that we focus attention on addressing this gap in our knowledge.

Further work I am undertaking will make a start in this direction, aiming to clarify the extent of any deficiencies afforded by various building types having different daylight typologies. In doing so, this research will contribute to establishing criteria for the type of daylight ingress needed inside our buildings, to meet both our visual and nonimage forming needs.

‘Measuring real daylight exposure afforded by various architectural environments and the implications for our health and wellbeing’. Her research is being conducted through the Bartlett. Her presentation, Lighting for Health, will form part of the programme (27 November) at CIBSE’s Build2Perform event at Olympia (www.build2perform.co.uk)

References

1 Hattar S, Liao HW, Takao M DMB et al. Melanopsin-containing retinal ganglion cells: Architecture, projections, and intrinsic photosensitivity. Science 2002; 295(5557):1065– 1070.

2 Lucas RJ, Peirson SN, Berson DM et al. Measuring and using light in the melanopsin age. Trends Neurosci 2014; 37(1):1– 9.

3 Boyce P. Human factors in lighting. Boca Raton: CRC Press, 2014, p.92.

4 Figueiro MG. Disruption of circadian rhythms by light during day and night. Curr Sleep Medicine Rep 2017; 3:76–84.

5 Stevens R and Rea M. Light in the built environment: potential role of circadian disruption in endocrine disruption and breast cancer. Cancer Causes and Control 2001; 12: 279–287

6 Schernhammer E and Schulmeister K. Light at Night and Cancer Risk. Photochemistry and Photobiology 2004; 79(4): 316–318.

7 Figueiro MG, Nagare R and Price LLA. Non-visual effects of light: How to use light to promote circadian entrainment and elicit alertness. LR&T 2018; 50(1):38–62.

8 Cajochen C, Zeitzer J, Czeisler C et al. Dose-response relationship for light intensity and ocular and electroencephalographic correlates of human alertness. Behavioural Brain Research 2000; 115(1): 75–83.

9 Vandewalle G,Balteau E, Phillips C et al. Daytime Light Exposure Dynamically Enhances Brain Responses. Current Biology 2006; 16: 1616-1621.

10 Figueiro M, Bierman A, Plitnick B et al. Preliminary evidence that both blue and red light can induce alertness at night. BMC Neuroscience 2009; 10:105

p Future work undertaken in the study will examine actual daylight received in a range of architecturally diverse office environments

Lighting designer Karen van Creveld, who has her own practice, has been awarded the £4000 Jean Heap Bursary for 2019. Her research topic is

ONLY CONNECT

What does open lighting control really mean? Francesco Anselmo explains and analyses the different wireless technologies, while looking to future possibilities

It’s 6:37am on a warm September day and Maia opens her eyes, prompted by the morning sunlight filtering in through the gaps in the window blinds. With a stretch of the arms, she thinks the blinds should open up a little to see if the sky is clear. This thought is met by the automatic movement of the blinds that quietly respond to her subliminal wish. She sees the sky is blue.

It’s a lovely morning, so what to wear today? This thought triggers a little scan to check the weather for the rest of the day. She sees it’s going to rain in the afternoon, and makes a mental note to take the hooded jacket and avoid the sandals. When she leaves the bedroom, the corridor light starts to glow gently, to the level she thought would not cause her eyes to experience any glare. She keeps walking to the kitchen to drink a glass of water.

Since Telepathy was introduced a couple

of years ago, screens have started to disappear from people’s lives. No more displays at work, no more mobile phones or tablets. Communication happens naturally, at the speed of thought.

The blinds motors, the lights, the wireless router, all the appliances at home and the devices at work trust Maia to tell them what to do. They’ve learned the shape of her thoughts and have been paired to respect her wishes.

FUTURE POSSIBILITIES TODAY

This vision of a possible future might seem very far away, but the building blocks are already around us. This year the team at Neuralink, Elon Musk’s neurotechnology company, has been busy working on an integrated brain-machine interface1 which promises to interface our thoughts to computing devices. But even more interestingly, humanity has been immersed in the wireless communication systems

Francesco Anselmo, MSLL, is associate director, IoT, Interaction and Lighting at Arup. The joint SLL/Arup event on lighting controls took place in September at the company’s London office

that have already transformed our lives since 1894, when Guglielmo Marconi demonstrated wireless communication to his mother at home by ringing a bell without wires. In the space of around 100 years, each one of us can now reach anyone else wirelessly thanks to the internet and cellular communication.

So we might not be too far from this fragment of potential future interaction with the control of our lighting systems. We are in fact already familiar with a plethora of wireless lighting control technologies that are becoming increasingly pervasive. It looks a bit like this Telepathy system is not too much science fiction after all.

All these different wireless technologies are designed to solve different problems, and can be classified in terms of connection type,

frequency, data speed and range. An attempt to categorise these technologies is shown in Table 1 and Fig 1.

Four connectivity types of wireless network technologies can be identified:

1 WPAN (wireless personal area network): this type of wireless network is designed to deliver low data bandwidth and speed at extremely short distances, using low power. In Fig 1 the WPAN technologies are located in the bottom-left part of the diagram (see overleaf).

2 W-Mesh (wireless mesh): this type of wireless network expands the distance of those WPAN networks by creating a mesh of WPAN nodes that can deliver information at longer distances.

3 WLAN (wireless local area network):

this type of wireless network is designed to deliver high data bandwidth and speed at short distances (up to approximately 100m) with high power demand. In Fig 1, the WLAN technologies are located in the bottom-right part of the diagram.

4 LPWAN (low power wide area network): this type of wireless network is designed to deliver low data bandwidth and speed at long distances using low power. In Fig 1 the LPWAN technologies are located in the top-left part of the diagram.

5 WWAN (wireless wide area network): this type of wireless network is able to deliver data at high speed at long distances using high power, and is usually identified with cellular communication technologies such as 3G and 4G. In Fig 1, the WWAN technologies are located in the top-right part of the diagram.

While for large-scale applications such as street lighting, WWAN and LPWAN systems can be the ones that can cater for the most relevant use cases, for interior lighting control applications the W-Mesh technologies including ZigBee, Thread and Bluetooth Mesh have proven to be the most appropriate. In fact they solve the issue of providing low-to-medium data bandwidth and communication speed at low power levels and at distances that are compatible with building spaces.

EXPLORING THE DIFFERENCES

But what makes these technologies different from each other, now that we have understood that they have similar frequency, bandwidth, speed, power and range attributes? To explore what their differences are, it is useful to extend the comparison to the ways that their communication protocols are actually implemented.

Like language and the mail system for humans, standardised communication protocols between electronic devices and between software applications are necessary to enable a message to be sent, received and understood. For this reason the Open Systems Interconnection (OSI) model has been standardised to allow the interoperability of different communication systems with a commonly agreed communication protocols architecture. The model subdivides a communication system into abstraction layers, and the original version of the model has seven layers, as shown in the diagram in Fig 2.

From left to right, the diagram shows the

p Table 1: Comparison of different wireless technologies

seven OSI layers from the lowest level one, the physical layer, to the highest level one, the application layer:

1 The physical layer allows the physical transmission and reception of raw data between a device and a physical transmission medium (a wire, the air, and so on) by converting the digital bits of information into electrical, radio, or optical signals.

2 The data link layer provides a data transfer mechanism between two communication nodes, defining the protocol to control the flow of information, and to establish and terminate a connection between two physically connected devices.

3 The network layer provides the means of transferring variable length data sequences (data packets) from one node to another that are connected in different networks.

4 The transport layer provides the means of transferring data packets from a source to a destination host, while maintaining the quality of the service (for instance, not missing data packets during the communication).

5 The session layer controls the connections between communication devices or applications by establishing, managing and terminating the connections between the local and remote application.

6 The presentation layer provides abstraction from data representation by translating between the application and network protocols.

7 The application layer is the OSI layer that is closest to the end user, interacting with software applications that implement data communication.

Keeping the analogy with language and the mail system, these layers can be thought of as envelopes contained into each other, with the application layer being the actual message that needs to be communicated.

Each ‘envelope’ adds an information layer aimed at making sure the message is delivered: the physical layer could be thought of as the outer envelope, the data link layer like the names of the sender and recipient, the network layer like the addresses of sender and recipient, and the transport, session and presentation layers like the mail system itself with the postman finally going through the town to present the message (the application layer) to the recipient.

Therefore, all the layers between physical and presentation are aimed at making sure that the transport of the message can actually happen and that the message can be delivered from the sender to the recipient. However, for the recipient to interpret the message, the application layer needs to be written in a language that can be understood by both sender and receiver. Furthermore if this language is not understood by both, if their grammar and vocabulary are not openly shared, then it cannot be used. It remains a sectarian slang that cannot find a wider audience.

This analogy can help when trying to understand the role that all the different wireless lighting control technologies play and where they position themselves.

In the simplified diagram in Fig 2 we have superimposed to the OSI layers the place that the main lighting wireless communication protocols occupy in this network communication architecture. By looking at it, the following comments can be made:

• The ZigBee and Thread technologies are based on the same physical and data link layer provided by the IEEE 802.15.4 standard governing LR-WPANS.

• Thread technology is also based on the 6LoWPAN standard.

• Bluetooth Mesh and Casambi are based on the same physical and data link layer provided by the Bluetooth Low Energy/ Bluetooth Smart standard. Both of them can therefore connect to Bluetoothenabled devices such as mobile phones and laptop computers.

• The EnOcean and ZWave standards provide common standards for all the network layers, including the application layer.

• Casambi provides a proprietary, single manufacturer stack that includes the application layer.

• Bluetooth Mesh includes device models, which provide a common application layer for products from different manufacturers.

• Both the ZigBee and Thread standards focus on providing network meshing capabilities and allow the use of different application layers, which can either be proprietary or open, and also across multiple manufacturers such as KNX IoT and dotdot.

The separation between application layer and other layers has been designed from the start for Thread as a way to replicate the success of WiFi, providing a standard for network interoperability that is agnostic to the application layer protocol. This means that any application protocol can be implemented using Thread as the mesh network infrastructure layer and allowing the

Figure 1: Comparison of different wireless technologies

use of third party Thread network routers. This approach is particularly interesting for companies that look into implementing their proprietary protocols on wireless mesh hardware that can be provided by third parties. This is the approach chosen by companies like Tridonic with its net4more product ecosystem. KNX IoT has also chosen Thread as the network layer standard to connect KNX devices in a lowenergy wireless mesh network.

Similarly to Thread, the ZigBee Alliance has opted for allowing different manufacturers to implement their proprietary protocols in the application layer. Examples of manufacturers using ZigBee for lighting devices communication are Enlighted, IKEA with their TRÅDFRI range, and Philips Hue. These solutions only allow you to network devices from a single manufacturer, however ZigBee also provides device models and will allow the dotdot application layer protocol to be used as an interoperability protocol for devices from different manufacturers.

Bluetooth Mesh is based on Bluetooth Low Energy (also known as Bluetooth Smart) and

has taken a different approach to Thread and ZigBee. In fact, it implements a common model for describing lighting devices across manufacturers and this is directly available to all. 2 This means that devices are able to communicate on the same wireless network.

Casambi has developed a proprietary wireless mesh protocol based on Bluetooth Low Energy, and taken the approach of creating an ecosystem of drivers from different manufacturers that are able to interface to their proprietary mesh communication modules.

WHAT DOES THE TERM ‘OPEN’ REALLY MEAN?

All of these lighting control standards and protocols have been claimed to be open. So what does open lighting control really mean, now that we’ve seen their differences? If open means being able to have access to the specifications, only Bluetooth Mesh allows direct access to the specification document. However Thread has an open implementation called OpenThread that is publicly available. 3

‘Like language and the mail system for humans, standardised protocols between electronic devices and between software applications enable a message to be sent, received and understood’

If open means interoperability across multiple wireless chips vendors,

control gear vendors and luminaire manufacturers to achieve consistent control, it is clear that interoperability cannot stop at the network layers, but it must also be at the application layer. For Bluetooth Mesh, this is achieved by providing a consistent model for lighting equipment (including sensors, drivers and emergency gear, for instance) that describes with completeness each system component and its behaviour. For Thread and Zigbee, this can only happen if the application layers are provided by common protocols such as dotdot and KNX IoT that are shared across lighting hardware vendors. Adding a proprietary application protocol clearly defeats the point of openness and interoperability.

As the wireless lighting controls and Internet of Things industries mature, network equipment manufacturers have started to develop chips and router devices that include multiple network layer protocols – for instance the D-Link border router 4 which supports Thread, ZigBee, Bluetooth BLE and Bluetooth Mesh to avoid choosing one system and keep on living with the necessary evil of having to deal with multiple standards.

But true interoperability can only be achieved if the application layer protocol and the device models are open to all and used by all.

This is where we should all aim to be, by improving our designs and specifications, and by selecting lighting control solutions that don’t lock our clients into single manufacturers and proprietary systems.

References

1 An integrated brain-machine interface platform with thousands of channels, Elon Musk, Neuralink, 2019 (www.biorxiv.org/ content/10.1101/703801v2)

2 www.bluetooth.com/ specifications/mesh-specifications

3 www.openthread.io

4 www.eu.dlink.com/uk/en/ products/dsh-g300-threadborder-router

p Figure 2: OSI communication model and wireless lighting control protocols

WELL AWARE

The latest SLL LightBytes series focuses on light and wellness, splitting into four themes: People Space Time Place. Each speaker addresses all the themes in a series of short presentations. Here two of the speakers, Roger Sexton and Richard Caple, take one of those themes each to give a flavour of the issues covered

PLACE: LIGHTING CONTROL AT ILLUMINATE, THE SCIENCE

MUSEUM – ROGER SEXTON

For the Place section of the 2019-20 Light Bytes Series we focus on a case study for an events space, Illuminate, the London Science Museum’s new venue which opened earlier this year. Incorporating two floors, level four (338sqm) and level five (651sqm), it is designed for private events such as dinners, dances and conferences.

The challenge of lighting these spaces went to lighting consultant Sutton Vane Associates. The brief for the controls system included the following requirements:

• Customisable scene setting for dedicated events/branding

• Recall of the standard scenes by:

traditional push buttons, app on phone or tablet

• Full control from external event consoles

The luminaires used in the main level five spaces were custom designed and included functional pendants and RGBW decorative ‘halo’ pendants, each with Bluetooth control –the former using spot modules with integrated Bluetooth chip sets and the latter using a four channel-dimming driver with Bluetooth control. These same drivers were used to operate RGBW strips of LED lighting beneath a stretched ceiling forming a feature stair light or ‘planet light’ connecting the two levels.

In the main level four space the same functional downlights were installed in conjunction with a grid of decorative strips

Roger Sexton is VP specifier service for Sponsor in Partnership Xicato

p The bespoke decorative halo pendants on level five each has Bluetooth control Images on both pages Sutton Vane Associates

of RGBW tape controlled by a Lighting Playback Control (LPC) system.

Using a combination of these light layers all manner of scene sets are possible from functional, such as presentation mode, to flamboyant, for instance, for dances, while also allowing branding with a subtle predominance of clients’ specific company colours.

The scene setting was carried out using Bluetooth-based Control Panel software. This communicates directly with the individual light points (each becoming a Bluetooth network ‘node’ once configured). Each node was assigned a unique identifier and aligned to a secure network. Relay nodes were added to ensure ubiquitous Bluetooth coverage throughout the space and repeater nodes were configured to provide robustness. The result

was a series of around 530 lighting nodes that are all capable of communicating with other devices on the same physical level. The next phase was to assign logical groups based on location and functions, for example, lighting on level four was separated from that on level five. Lighting for the hallway and restroom areas was identified separately to that in the event space, and designations were assigned between functional, decorative and the ‘planet light’ lighting.

Scenes were then defined within the Control Panel software and each light point associated with one or more scenes with specific light levels and fade times.

Additional scenes were programmed to the DMX grid located on level four via IO Modules. These plug-in software modules allow for integration with thirdparty products, protocols and web resources, as well as providing automation for complex triggering requirements. In this instance a Playback Controller (LPC) was used for dynamic lighting control over DMX for the RGBW pixel grid, show control and scheduling, and – via a gateway and module plug-in – the ability to send and receive commands, button presses, scheduled events and more to and from the static white system.

Individually controllable and independently running timelines allow for 10 dynamic, pre-programmed lighting effects, with real-time manual overrides via switches or an iOS app. The AV system enables eDMX pass-through triggering with the LPC acting as a gateway – allowing external event consoles full control of the lighting grid and passing relevant commands to trigger scenes on the luminaires.

Scene recall can be performed using synchronised switches at various points on the two floors or through a dedicated IOS App that was developed by Sutton Vane Associates and War Face.

Each contact switch results in a different scene recall command. In the case of the Bluetooth nodes this is a direct command, while for DMX devices the call is first issued to a Bluetooth Gateway before being forwarded over Ethernet to the LPC. This process is carried out in reverse when Illuminate’s in-house production company uses a DMX board and freestanding DMXcontrolled lighting, thus scenes with audio and additional visual triggers are possible.

The IOS App can be used to recall pre-defined scenes as well as control individual luminaires which are depicted on a lighting plan in their real-time locations.

Commands from the App are sent via WiFi to a Bluetooth Gateway which in turn issues a Bluetooth instruction to a lighting group or groups to recall scenes or raise/lower lighting intensities on individual nodes.

‘Using a combination of these light layers all manner of scene sets are possible from functional to flamboyant’

p Top: the feature ‘planet light’ on the stairs between the two levels.

Below: DMX grid scenes on level four

PEOPLE: OUR RESPONSE TO LIGHT – RICHARD CAPLE

Light is fundamentally important to all humans, but most of us take it for granted unless the light in our surroundings is not desirable. Too much, too little, too glaring, too directional. Light plays a significant role in our lives, and it’s more than just about being able to see. Light affects us mentally, physically and in our behaviour.

Our visual system is complex: interestingly, 80 per cent of the information our brain

receives is from our eyes. But our eyes not only help us to see, they also send vital signals to our brain which help control the release of hormones in our body. Work in the late 1990s discovered the so-called third photo receptor, the intrinsically photosensitive retinal ganglion cells, or ipRGCs. These non-visual receptors were found to send information to our in-built body clock which then controls hormone release in our body, in particular melatonin and cortisol, our ‘sleep’ and ‘awake’ hormones.

Humans have a circadian rhythm, a 24hour wake-sleep cycle. While this rhythm is inbuilt, it needs entrainment or adjustment to keep it consistent. Light plays a significant role in this, and can advance or delay our circadian rhythm based on the time, and amount and wavelength of light received. IpRGC stimulation, at the right time, is crucial as it helps keep our circadian rhythm entrained. Our natural wake-sleep pattern is important, a disrupted circadian rhythm can lead to fatigue and poor health.

WHERE AND WHEN:

Dublin (21 November)

Manchester (30 January)

Leeds (13 February)

Bristol (26 March)

‘‘Our visual system is complex: interestingly, 80 per cent of the information our brain receives is from our eyes’’

Why does this matter? Humans have been evolving for 200,000 years. During the majority of this time, daylight played a significant role in defining our active hours. It’s only in recent times that artificial lighting was invented. Daylight, and importantly the absence of daylight, would have been a significant factor in entraining our circadian rhythms. Today, however, for millions of workers across the planet, daylight often no longer plays this significant role. Today we exist in a world no longer dominated by sunrise and sunset. We are surrounded by artificial light of fixed output and wavelength.

Many people travel to work under artificial light, spend a significant proportion of the day under artificial light, and then travel home under artificial light. Many may have very little exposure to daylight. Cheap and widespread use of artificial light has lengthened our active time and changed our social behaviour resulting in an elongation of our functioning day. Technological advances and the increasing demands of modern day life mean that we can no longer be bound to just daylight hours.

While getting access to daylight should always be championed above all else, is there more that we can be doing to improve the wellbeing of people living under artificial lighting? Does it really matter? The latest SLL LightBytes series looks at the issues involved and aims to answer some of these questions.

Glasgow (23 April)

London (4 June)

For more details: www.cibse.org/societyof-light-and-lighting-sll/sll-lightbytes-series

To book: sll@cibse.org or 0208 772 3685

Watch CPD presentations from the 201819 SLL LightBytes series: www.cibse.org/ Society-of-Light-and-Lighting-SLL/SLLLightBytes-Series/SLL-LightBytes-201819-Presentations

The LightBytes series is made possible by the Sponsors in Partnership: Soraa, Thorlux Lighting, Xicato and Zumtobel

Speakers:

• Eleanora Brembilla, research associate in Advanced Building Daylight Modelling, Loughborough University

• Richard Caple, marketing and lighting applications director, Thorlux Lighting

• Roger Sexton, VP specifier service, Xicato

• Graeme Shaw, technical application manager, Zumtobel Group Lighting (UK)

Richard Caple is marketing and lighting applications director for Sponsor in Partnership Thorlux Lighting

p Whether at home, at work or commuting between the two, many people currently spend most of their time in artificially lit conditions

AROUND THE CLOCK

Iain Carlile singles out three of the latest Lighting Research and Technology papers whose themes range from night lighting to daylight

Raynham et al’s paper presents a novel method to analyse road traffic collision data to determine if a collision occurred during the daytime or night-time. The developed method involves analysing solar altitude to establish cut-off points of daylight based on a study of daylight availability in England, Scotland and Wales. Using a set of data (STATS19) for a one-week period of time either side of the change between Greenwich Mean Time and British Summer Time in the UK, the authors were able to isolate road traffic collisions that occurred one week in darkness and the other week in daytime.

The results revealed that 19.3 per cent more collisions happen during dark periods, and that there was an increase of 31.7 per cent in pedestrian injuries, indicating that risk to pedestrians is much higher during the dark, especially given that previous studies had shown walking and cycling is less common at night.

Also looking at an application of lighting at night, Bullough et al conducted experiments to study car park illumination, investigating the relationship between scene brightness, light levels, spectral distribution and uniformity of electric lighting, with respect to a person’s perceived feeling

of safety and security. Two laboratory experiments were conducted using a scale model of a car park with controllable LED lighting, allowing parametric variations in lighting levels, spectrum and uniformity of light.

From the experimental results, a mathematical model of overall brightness and perceived safety was developed, which can be used to predict a person’s perception of different lighting schemes. The authors propose that the model can be used to assist designers to balance perception of personal safety with energy usage and budgets.

Knoop et al present a paper which describes the current knowledge on the characteristics of daylight. The authors examine factors such as intensity, spectral power distribution, and spatial direction and diffuseness of daylight, as well as non-image forming effects. These include dynamic changes in intensity and colour of daylight supporting circadian entrainment, mood and alertness, and how in many cases daylight can often perform these functions better than the conventional application of electric lighting.

With respect to daylight, the authors note that some human responses are well defined, for example, sunlight and vitamin D production, while many others are less established and cannot be explained so straightforwardly, such as the benefit of

Daylight:Whatmakesthedifference? 5

manyinterlinkedaspectsincludingduration andtimingofdaylightexposure,wavelength andintensity.Excessivenear-workmayalso damagechildren’seyesight;eventhoughevidenceforthisisinconsistent,arecentreviewof

windows. In addition, other responses to light are mediated through both visual and non-image-forming pathways. The authors note that many of these require further research and set out their suggested priorities.

Iain Carlile FSLL is the immediate 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)

Daylight: What makes the difference?

M Knoop, O Stefani, B Bueno, B Matusiak, R Hobday, A WirzJustice, K Martiny, T Kantermann, MPJ Aarts, N Zemmouri, S Appeltk and B Norton

The role of lighting in road traffic collisions

P Raynham, J Unwin, M Khazova and S Tolia

Impacts of average illuminance, spectral distribution, and uniformity on brightness and safety perceptions under parking lot lighting

JD Bullough, JD Snyder and K Kiefer

Figure3 Rangeofapproximatehorizontalilluminancelevelsindoors(blue)andoutdoors(black)inexample situationsduringwintertimeinBerlin,Germany(left:evening;middle:clearskycondition,afternoon;right:overcast skycondition,afternoon).

p Horizontal illuminance levels indoors (blue) and outdoors (black) in example situations during winter time in Berlin (Daylight: What makes the difference?)

Events

2019

UNTIL DECEMBER

Illuminated River (continuing programme of Unescoendorsed events to celebrate first four London bridges to be lit)

Venues: River Thames, assorted starting points https://illuminatedriver.london/whatson

6 NOVEMBER

Fundamental Lighting Course (organised by the ILP)

Venue: ILP, Regent House, Rugby jo@theilp.org.uk

8 NOVEMBER

CIBSE training: Lighting –Legislation and Efficiency

Venue: CIBSE, Balham, SW12 training@cibse.org

13-14 NOVEMBER

LuxLive

Venue: ExCeL London http://luxlive.co.uk

14 NOVEMBER

SLL Young Lighter 2019 final

Venue: LuxLive, ExCeL London www.cibse.org/society-of-light-andlighting-sll/sll-young-lighter-2019

14 NOVEMBER

Lux Awards

Venue: London Hilton, Park Lane

https://luxawards.co.uk/location-2/

19 NOVEMBER

Perfect Light and the Perfect Light Experience

SLL and CIBSE North West

Venue: Arup, Manchester sll@cibse.org

21 NOVEMBER

SLL LightBytes: light and wellness

Venue: The Chocolate Factory, Dublin sll@cibse.org

25 NOVEMBER

DIALux Lighting Software: Foundation Level

(Lighting Industry Academy)

Tutor: Liz Peck

Venue: Marriott Hotel, Slough www.thelia.org.uk

26-27 NOVEMBER

Build2Perform

(organised by CIBSE)

Venue: Olympia London www.build2perform.co.uk

11 DECEMBER

CIBSE training: Lighting Design –Principles and Application

Lecturer: Liz Peck

Venue: CIBSE, Balham, SW12 training@cibse.org

2020

30 JANUARY

SLL LightBytes: light and wellness

Venue: Castlefield Rooms, Manchester sll@cibse.org

13 FEBRUARY

SLL LightBytes: light and wellness

Venue: The Tetley, Leeds sll@cibse.org

8-13 MARCH

Light and Building

Venue: Messe Frankfurt

https://light-building.messefrankfurt.com

LightBytes

The LightBytes Series is kindly sponsored by Soraa, Thorlux Lighting, Xicato and Zumtobel. For venues and booking details: www.sll.org.uk

LET Diploma: advanced qualification by distance learning. Details from www.lightingeducationtrust.org or email LET@cibse.org

CIBSE Training: various courses across the whole spectrum of lighting and at sites across the UK. Full details at cibse.org/training-events/cibse-training

13-14 NOVEMBER: LUXLIVE (INCLUDING YOUNG LIGHTER 2019 FINAL) AT EXCEL LONDON