As LED lamps and luminaires have matured and their price fallen over the past few years, their long life, tunable colour and low power consumption have kickstarted a major change in how we think about light inside buildings.

This goes beyond illumination into hygiene, health, wellbeing, data networking as well as using connected lighting systems as infrastructure for other Internet of Things (IoT) sensors.

In the past, lighting accounted for a large proportion of commercial energy bills, with some estimates showing it at almost half of retail energy consumption. So, the regulations for light levels in buildings were set at a minimum – well below the light levels available outdoors – with an eye on energy use and with limited consideration for the needs of people, beyond being able to see their work.

With LEDs, the energy consumption is so much lower that there’s now a good trigger to explore the various other aspects of lighting. Simply replacing existing lights with LED equivalents just to cut costs would be very limiting and a huge missed opportunity. Let’s explore some of the other roles that lighting can play.

UV-C lighting for hygiene 

The COVID-19 pandemic has really raised the profile of using UV-C lamps to neutralise viruses on surfaces, in water and in the air. The technology has been around for more than 30 years, being used to purify municipal drinking water, to help fight tuberculosis in some countries, and to keep air-conditioning systems and agricultural plants free of mould. But its adoption has been patchy.

With the outbreak of COVID-19 came a flurry of UV-C products from many manufacturers to use the technology in chambers to clean smaller items; in offices to clean the upper air continuously using convection to ensure all the air is cleaned, or to do a periodic deep clean when the office is empty; in aircraft to clean the plane between flights; and in hospitals to sterilize a room before a new patient arrives.

LEDs for health and wellbeing

There are many practical examples of how light affects us as humans. They include lamps for Seasonal Affective Disorder (SAD), vitamin D supplements to offset lower levels of sunlight, blue-light filters on mobile phones and PCs, and citizens complaining about cool white streetlamp LEDs. Many scientific studies have highlighted how the quality and quantity of light we receive have an impact on our sleep patterns, our ability to work well, our memory, and how we feel.

With modern jobs and work practices, many people now spend the vast majority of their day indoors, with the US average at 87% in the early 1990s. So, it’s clear that employees will work better, plus feel more awake and happier if their workplace is lit in a sympathetic way.

Lighting designers have got hold of the subject and, since the mid-2010s, the field of ‘circadian lighting’ for buildings has become popular. Natural daylight changes in brightness and colour temperature, so indoor light should mimic changes in the quantity and white colour of outdoor light to respect peoples’ circadian rhythms, which control the sleep-wake cycle. Suppliers are now going beyond circadian lighting into ‘biophilic design’, aiming to bring the fuller benefits of outdoor light indoors. They incorporate circadian lighting but also manage the pattern of emissions across the light spectrum to optimize light for cognitive function, mood, memory, and production of hormones such as serotonin, cortisol and melatonin.

An example is Signify’s NatureConnect system for offices, launched in May 2020. It offers higher brightness for the main lighting that adjusts during the day and goes further by providing a sky-coloured panel in the centre of a lighting system, as well as subtle colour variations projected onto walls to mimic the colour changes people would receive in nature from movement in trees and changing landscapes.

One of the interesting aspects of this approach to lighting is that it doesn’t only apply to humans, but also to animals and plants. Since the mid-2010s, there have been several scientific studies into the effects of light on fish in aquaculture settings, on poultry farms and on pig farms. Lighting companies started rolling out new products, and it’s now possible to have a lighting system that brings higher yield of healthy animals and costs less to run than existing alternative lighting.

There’s a similar shift happening in horticulture. This is partly being led by start-ups running vertical farms, where crops grow in stacks of trays, each with its light recipe to control the spectrum and intensity, and their microclimate carefully controlled by a central system. But intelligent lighting systems are also available for regular greenhouses to mimic nature’s dusk or dawn and have plants start and close the day. Russian supermarket and farming chain Riat is doing pioneering work in partnership with Signify, growing salad plants in indoor farms all year around without natural light and without the use of pesticides. It has found crop yields for cucumbers and tomatoes are similar to those produced under traditional farming practices, but with much lower wastage, giving a payback period of about two years.

The world is at an early stage in the task of exploring these issues and there’s plenty of learning still to come. New lighting systems being installed today need flexibility, programmability and control built into them so that they can be configured in line with what we know and can be updated later if the use of an area changes, or if science provides better answers than we have now. This means that modern lighting systems are now IoT systems with sophisticated controls.

Lighting as IoT infrastructure 

Once the lighting is connected and controlled by an IoT platform, the economics of other IoT applications start to improve. It’s attractive and relatively easy to use the lighting system as an infrastructure for other sensors to get data about things like occupancy, people movement and social distancing, levels of humidity, noise and light, as well as for connecting Bluetooth beacons.

With suitable luminaires in use, it costs less and is far easier to install these sensors to run over the lighting network, than to install a separate system with its own cabling. There’s a parallel here with the option to use connected streetlights as a more general smart city infrastructure.

LiFi, or lighting for data networking

We’re also starting to see the option of using lighting as a data network in its own right, with Light Fidelity, or LiFi. This modulates LEDs at high speed, so that people can’t see any flicker, in order to send data to and from devices in the room using infrared or visible light. This is a younger technology: though not yet as universal as Wi-Fi is today, it offers interesting advantages in security, bandwidth, congestion, and in environments where radio-based communication is not allowed, or is difficult, such as in factories or oil and gas plants.

Finally, because of the history of lighting, many owners and managers of buildings and offices tend to think of lighting as a necessary overhead, but one that should be minimized. So light fittings, once installed, stay there for a long time and are only changed out during a refit or when they become faulty. However, advances in lighting technology show there’s a strong argument for rethinking this approach, as there are now multiple business cases with attractive payback periods for upgrading earlier.

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