The Challenges of Smart Lighting for Sustainable Cities

Last year, Angers Loire Métropole launched its “smart city” program aimed at making the capital of Maine et Loire one of the most connected cities in France.

In this project, particular attention is paid to public lighting, which is being completely renovated to become more economical and efficient. 30,000 streetlights will be equipped with LEDs. At the same time, 10,000 poles and 5,000 electrical cabinets will become connected and ready to host various third-party applications.

The same is true further east, in Dijon Métropole, where the OnDijon smart city project plans to update 34,000 light points, also equipped with LEDs, as well as the Citybox system, which allows each streetlight to be equipped with additional services: wifi terminals, video surveillance, environmental sensors to measure air quality, public address systems, etc.

In both cases, local authorities are looking for a dual objective: to save energy and improve the daily lives of residents. “The replacement of lighting with LEDs alone should generate more than 65% energy savings over 12 years,” says Dijon City Council on its project website. This model is now being used by many cities, including Toulouse, Bordeaux, Nantes, Chartres and Macon, as well as Copenhagen and Oslo. Many cities are rethinking their public lighting based on this model.

Lighting 2.0 to reduce local authorities’ electricity bills

This is what smart lighting is all about. It can enable a streetlight to switch on only when a car or pedestrian passes by, or to modulate the lighting around certain areas according to the time of day. Thanks to LEDs and technology, the new generation of public lighting offers two environmental guarantees: better consumption and reduced light pollution.

It is also a non-negligible economic gain for communities. Public lighting represents on average 40% of the electricity bill of French municipalities. This annual expenditure on urban lighting amounts to nearly 2 billion euros throughout the country, and the ADEME estimates that between 30% and 40% of this consumption is wasted on unnecessary or inefficient lighting.

France does not skimp on this issue. According to the French Lighting Association, there are an estimated 9.5 million lights in French cities. However, 50% of these streetlights are more than 25 years old and 10% of them are still mercury vapor lights (which were banned from the market in 2012 because of their energy-consuming and environmentally harmful nature). Moreover, orders and amendments to the environmental code published in December 2018 require local authorities to replace obsolete and energy-intensive lighting.

And in the bosom of this lighting modernization, the idea is to reduce consumption, fight against light pollution but also to improve the daily lives of residents without cutting back on their safety. In a report published in March 2021, the Court of Auditors warned about the state of French public lighting, and in particular the management it is done by the communities. “Some do not renovate their stock due to lack of resources or interest, others limit their interventions to the maintenance of existing facilities and do not seek to improve the performance of equipment,” points out the report, which adds that operations to reduce the environmental impact of lighting “remain marginal” and that the fight against light pollution is “a secondary objective.

“At least, the community can achieve 20 to 30% savings through LED with a return on investment in 7 to 8 years”

Joel Lavergne

French Lighting Association (AFE)

Modulating light intensity, the grail of lighting?

In the vast majority of French municipalities, lights are switched on at nightfall and off at sunrise. A great waste that can be avoided in different ways. The main one being to modulate the light intensity. Or to clearly switch off the streetlights. Moreover, 14,000 municipalities in France, out of 35,756 in Metropolitan France, have decided to cut their public lighting between one and six o’clock in the morning.

Less radical, the management of light intensity is at the heart of the problem for urban public lighting. In fact, long before connected lighting, solutions were tested and proposed to reduce the intensity of streetlights at night. Thus, with a simple voltage dimmer at the level of the electrical cabinet that supplies a group of streetlights, it is already possible to make savings.

But with LEDs, it is now possible to go even further, since they can be reduced to 10% of their nominal power and then be restored to 100% in an instant. In addition, LEDs consume half as much as traditional lighting and generally have a longer lifespan. “At least, the community can achieve 20 to 30% savings with LEDs with a return on investment in 7 to 8 years,” said Joel Lavergne, of the French Lighting Association (AFE), to our colleagues of Smart City Mag.

But the grail of intelligent lighting is to couple the LED street lamp with presence sensors that allow to reduce the lighting to 10% or 20% of its power during the whole night – or even to turn it off completely in some areas – and to turn it on again only when a movement is detected in a perimeter of a few meters around the street lamp. This could be the passage of a cat, a cyclist or a car. The idea here is to preserve the safety potential of lighting while reducing light pollution and electricity waste to a minimum.

Improving the daily life of residents

Connected street lamps also mean monitoring and remote management of this urban furniture. The aim is to be able to remotely monitor the activity and consumption of each streetlight, to track breakdowns or malfunctions in real time and thus improve the maintenance of the equipment. Here again, remote management of equipment reduces maintenance costs while improving the quality of service.

Another objective sought by communities regarding lighting is the improvement of services to residents and the use of streetlights as auxiliaries for the creation of new services. In this sense, it is a first step towards the development of connected cities. Streetlights become relays for Wi-Fi, video surveillance, furniture capable of launching sound alerts or simply playing music. They can also be used to receive the sensors needed to measure air quality, for example.

This is a market that has been developing since the early 2010s, driven by Engie (Ineo), EDF (Citelum), Bouygues Construction (Citybox) and the Vinci group (Citeos), which manage projects in French cities in partnership with local companies and technology firms such as CapGemini. In the field of embedded electronics, several structures are also specializing in this promising market and some are even dreaming of a large-scale deployment of Li-Fi, the Internet that is obtained through light.

However, is this search for technological optimization absolutely necessary when the primary objective – the reduction of consumption, and its corollary on the budget of cities, could be amply satisfactory. Because the desire of “smart cities” to connect and supervise everything remotely also questions our way of seeing the future of the city.

“Today, the growth of our digital systems already requires an additional consumption of about 9% of energy per year”

The Shift Project

An environmental limit to the all-technological city?

At the end of January 2021, and a few months after announcing that it wanted to become the most connected city in France, the metropolis of Angers fell victim to ransomware, i.e. malicious software that paralyzed many of the community’s services and computers. “The system went down and we no longer had access to anything. The Internet site, the library site, the services provided to the population, the software, the computers… Everything was out of order,” explained an elected official contacted by RTL on this subject.

In recent months, several French cities have been victims of cyberattacks: Annecy, Aix-Marseille, Vincennes, Besançon and La Rochelle are among them. But tomorrow, if we consider that all urban furniture, street lamps, billboards, bus stops, and even garbage cans are to be connected, this security constraint is an issue that is not insignificant.

It is also linked to an environmental issue. Just as there is no guarantee that the benefits of 5G will match the environmental costs it entails, what about the exponential multiplication of sensors and connected objects to govern the city of tomorrow? Today, the growth of our digital systems already requires an additional consumption of about 9% of energy per year, according to the Shift Project. An increase that could be exponential with the development of connected cities… bearing in mind that we must also take into account the materials needed to design these objects, but also their potential reuse or recycling.

Will tomorrow’s cities be able to deal with this issue? The fact is that some connected innovations have the potential for environmental gains, which seems to be the case with smart street lamps. But other services associated with these streetlights do not have the structural capacity to do so. This raises the question of the energy relevance of the solutions, i.e. the difference between the direct gain in terms of consumption and what it costs in production and use. As well as what it brings in societal comfort for the community.

And tomorrow, autonomous street lamps?

As far as connected lighting is concerned, the environmental gains (reduction of consumption and light pollution) as well as the economic gains are obviously very interesting. Another market could also develop in this niche, thanks to autonomous street lamps, which produce the energy they need themselves.

This promising niche is called “solar lighting as a service” in the United States. A concept that is beginning to develop in France thanks to the efforts of young innovative structures, including the Bordeaux startup Sunna Design. It offers street lamps equipped with solar panels that produce and consume their own energy and, when possible, reinject the surplus into the electrical networks.

This practice is mainly aimed at municipalities, but also at real estate developers and shopping centers, which can at least reduce their costs and, in some cases, generate additional income from the sale of electricity from their street furniture.

To go further, we could also bet on the development of bioluminescence in order to propose a softer and more economical urban lighting, at least at night. But this, even if some companies are starting to explore it today, it is not for the moment.