How Efficient Is Solar Street Lighting?

Solar street lighting has gained significant momentum as a sustainable and cost-effective lighting solution for urban and rural areas in the last 5 years. Utilising solar energy to illuminate streets, pathways, and public spaces cutting electricity costs, minimises carbon emissions, eliminates the requirement for any infrastructure such as cable laying and provides lighting even during power cuts. But how efficient are these solutions, and what factors influence their performance?

In this article, we explore the key factors that determine the efficiency of solar street lighting solutions, focusing on battery storage, photovoltaic (PV) panel quality, and lumen output. Whether you're a Lighting Designer, Streetlighting Officer, Highways Manager, Facilities Manager etc, understanding these factors will help you make informed decisions when investing in solar lighting.

1. Battery Storage

Batteries play a crucial role in solar street lighting, as they store the electricity generated by solar panels during the day for use at night. The balance between light head output and battery stored is very important, as you may set a light up to use all its battery within a few hours! Generous battery storage ensures consistent lighting, even on overcast days or during extended periods of low sunlight.

Key Points for Battery Efficiency:

•    Battery Type - Lithium-ion batteries steal the show for their longer lifespan, faster charging, and greater energy density compared to regular lead-acid batteries, steer away from L-A B's!

•    Storage Capacity - Ensure the battery has enough capacity to power the light for multiple nights, especially in environments like the UK. We recommend a minimum of a 461wh battery, this is the smallest battery we will sell to our clients and avoid anything lower than this if you intend to have ample lighting all year round.

•    Depth of Discharge (DoD) - A battery's DoD indicates how much energy can be used before recharging. Higher DoD means better utilisation without damaging the battery. Our batteries have a DoD at 50%.

•    Charge Controller - Solar street lights with smart controllers prevent over charging and prolong the life of a battery.

2. Photovoltaic Panel Quality (Maximising Energy Capture)

Solar panels are responsible for converting sunlight into electricity. The efficiency of solar street lighting largely depends on the quality of the photovoltaic panels used.

Key Points for Panel Efficiency:

•    Panel Type - Monocrystalline panels are more efficient than Polycrystalline panels, converting a greater percentage of sunlight into electricity. For this reason Mono panels are more expensive but also last longer totalling up to 40 years.

•    Solar Conversion Efficiency - High-quality panels typically offer 20-23% efficiency, meaning they can convert more sunlight into usable energy.

•    Positioning and Cleaning - Proper alignment towards the sun ensures maximum energy capture. Vertical SOLARWRAP® on street lights will always provide better yields due to debris not being able to accumulate on the panel which almost guarantees charge throughout the day. On flat solar panels it is more common to see leaves, dust, dirt, snow and other residue sit on the panel and then effect the efficiency of the solar. We always suggest people look at our ASTRAL solar street light which utilises the vertical and hexagonal SOLARWRAP®. If you choose a flat panel, you are more likely to require a maintenance agreement for regular cleaning and inspections. 

3. Lumen Output

 

The brightness of streetlights is measured in lumens, representing the amount of visible light emitted. Efficient solar street lighting systems strike the right balance between brightness, energy consumption, and battery capacity.

Key Points for Lumen Output Efficiency:

•    LED Light Source - Light-emitting diodes (LEDs) are the most energy-efficient lighting option, consuming less power while providing brighter illumination compared to traditional bulbs (DO NOT buy a solar street light with any other light head than LED).

•    Luminous Efficacy - This refers to the number of lumens produced per watt of energy consumed. High-quality LEDs typically offer 120-150 lumens per watt.

•    Lighting Design - Proper light distribution ensures uniform illumination, reducing dark spots and enhancing safety. Adjustable lighting angles and motion sensors can optimise energy use.

•    Dimming Capabilities - Most solar street lights come with smart sensors that adjust brightness based on activity or time of day, further conserving energy. We suggest you choose solar street lights with programmable dimming schedules for maximum energy efficiency.

•    Lighting Classifications - In the UK we have lighting classifications which indicate lighting levels with P1 being the highest and P6 the lowest. P1 is for busy traffic routes and P6 would be for cycle routes and occasional traffic. We suggest before purchasing and installing any street lights, you find out what classification you require for your area and then decide on the specification of your solar light.

Additional Comments

 

•    Location and Sunlight Availability - Assess the geographic location and ensure the solar panels receive consistent sunlight throughout the day and consider bad weather.

•    Weather Resistance - Opt for lights with IP65 or higher ratings to withstand rain, dust, and other environmental factors.

•    Maintenance Requirements - Low-maintenance systems with long-lasting components can significantly improve the overall cost-efficiency of solar street lighting.

Conclusion

When evaluating solar street lighting for your project, consider the following checklist:

•    Long-lasting batteries with optimised charge controllers.

•    LED lights with high lumen output and smart dimming features.

•    Sensors like motion sensors which trigger dimming periods and dusk to dawn sensors.

•    Weatherproofing for reliable operation in all conditions.

•    Manufacturer Warranty and post-installation support.

Investing in solar street lighting can lead to long-term savings, improved safety, and a reduced carbon footprint. By understanding the efficiency factors outlined above, you’ll be well-equipped to select the best system for your needs.

Thinking about switching to solar street lighting? Evaluate your options based on the information above and take a step toward a sustainable future!

Call our team for guidance or support and a specialist will be happy to help you. 01923 726150