Solar public lighting and autonomy

Solar public lighting appeals to more and more municipalities: no connection to the grid, no trenching, zero electricity consumption in use. But its effectiveness depends on rigorous sizing of the panel, the battery and energy management. This article explains how an autonomous solar column works, its advantages, its limits and its use cases for local authorities.

How does a solar light point work?

A solar public lighting column is an autonomous system that produces, stores and returns its own energy. It is built around four components:

The photovoltaic panel captures solar energy during the day and converts it into electricity.
The charge controller, adapted to the characteristics of the panel and the battery, manages the transfer of energy without overcharging or damaging discharge.
The battery stores the energy to return it at night. Current models favour lithium iron phosphate (LiFePO4) chemistry.
The LED luminaire, often combined with a presence detector and dimming management, returns the light at night.

The whole is controlled by electronics that programme the night profiles: full intensity when someone passes, reduced level in the absence of detection, dimming in the middle of the night. This fine management is the key to autonomy.

The LiFePO4 battery, the heart of the system

The battery is the component that determines the reliability and lifetime of the installation. LiFePO4 (lithium iron phosphate) technology has become established for solar lighting for several reasons:

High longevity: these batteries withstand a very large number of charge/discharge cycles, which gives them a much longer lifetime than older chemistries, over many years of operation.
Safety: they are not subject to thermal runaway and do not use cobalt, which makes them a safer solution.
Reduced maintenance and good resistance to temperature variations.

A BMS (Battery Management System) permanently monitors the battery: it prevents overvoltage and undervoltage and preserves the longevity of the cell. The energy performance of the luminaire also plays a part: the more efficient the LED (high lm/W), the less it draws on the battery for the same illuminance, and the more comfortable the autonomy. We develop this point in our article on the luminous efficacy of luminaires.

The advantages for local authorities

No trenching, no connection: no civil engineering or grid cabling, which reduces installation costs and lead times, particularly on isolated sites.
Zero grid consumption: the energy is free in use and the installation is unaffected by variations in the price of electricity.
Flexibility of location: outlying car parks, paths, car-sharing areas, surroundings of facilities, areas without a nearby grid.
Sufficiency: presence detection and dimming reduce lighting to actual needs and limit light pollution.

The limits to anticipate

Solar lighting is not a universal solution. Several factors must be studied before any deployment:

Local sunshine: autonomy depends directly on the energy captured. A region with little sunshine or a shaded site requires oversizing of the panel and battery.
Seasonal sizing: autonomy must be guaranteed during unfavourable periods (short days, overcast weather), often by providing several days of reserve.
The usage profile: permanent lighting all night is more demanding than operation with detection and dimming. The night scenario must be calibrated to the actual need.
The location: orientation and tilt of the panel, and the absence of shading (trees, buildings), determine production.

That is why a sizing study is essential: it cross-references the illuminance requirement, the night profile, local sunshine and target autonomy to guarantee reliable operation all year round.

Use cases and place in an overall strategy

Solar is fully relevant on sites that are poorly served by the grid or difficult to connect: remote parking areas, pedestrian paths and cycle tracks, surroundings of business parks and sports complexes (car parks and paths of gymnasiums or stadiums), street furniture. On main roads with high illuminance levels · such as the sports pitches themselves, which are very power-hungry · wired lighting often remains more suitable; the two approaches complement each other within a municipal lighting plan.

Solar is thus part of the wider approach of modernising the installation, alongside replacing old sources and LED renovation. For the regulatory and financial context, see our articles on the end of discharge lamps and on the renovation of public lighting.

Discover our solutions in the solar, solar public lighting and solar floodlights ranges.

FAQ

What autonomy for solar public lighting?

Autonomy depends on the sizing (panel, battery), local sunshine and the night profile. A well-designed system provides a reserve for periods with little sunshine. Only a sizing study guarantees operation all year round.

Why a LiFePO4 battery rather than another?

LiFePO4 chemistry offers a long lifetime (many cycles), increased safety (no thermal runaway, no cobalt) and reduced maintenance, which makes it the current reference for solar public lighting.

Does solar suit all municipalities?

It is particularly suited to isolated or unconnected sites. Its effectiveness depends on local sunshine and the illuminance requirement. On very brightly lit roads or in regions with little sunshine, wired lighting may remain preferable: a study decides according to the site.

Is civil engineering needed to install a solar column?

No, that is one of its main advantages: no trenching or connection to the grid. Only the foundation of the column is needed, which reduces costs and lead times.

Need a photometric study? Sizing your solar public lighting is the work of a lighting design office: we recommend the expertise of the Luminance Consulting agency, the lighting design office that contributes to developing our ranges of luminaires based on an in-depth analysis of the needs of the most demanding customers. Rexylum supplies you with the prescribed solar luminaires: contact us.