Adaptive Solar Lighting

Adaptive Solar Lighting and Public Lighting Standards

Does your Solar Lighting Installation Comply with AS/NZS 1158.3.1:2020?

“When Adaptive Lighting is used, each dimming level shall be such that it complies with all the requirements of a relevant lighting category. The control system shall be failsafe in that on a failure of any element of the control system, the luminaires shall revert back to their initial undimmed level.”

– AS/NZS 1158.3.1:2020 3.1 – Light Technical Parameters

Abstract

The use of Solar Powered Lighting Systems in public areas is becoming ever more popular however, not all solar powered lighting products are designed with the same operation characteristics.

Many Solar Powered Lighting Products are designed to make use of lighting control technologies to provide adaptive light output and manage battery consumption which can pose a challenge when it comes to ensuring conformance to standards in public lighting applications.

This technical paper outlines the key factors that should be considered when evaluating adaptive solar lighting systems for the use in public lighting applications, in particular Car Park areas under the Australian Lighting Standard AS/NZS 1158.3.1:2020, however this does apply more broadly to all public lighting applications.

 What is Adaptive Lighting?

Adaptive lighting is the use of lighting controls to adjust or dim the output of lights for varying operation timeframes.

In solar lighting applications, adaptive lighting control is commonly used to conserve battery consumption. It is especially common in solar lighting products with smaller battery systems.

It is also used in applications where a lighting system is only intended to serve for part of the evening due to curfew restrictions.

 Adaptive Lighting and the Australian Public Lighting Standard

The Australian Lighting standard for roads and public spaces (AS/NZS 1158.3.1) sets out minimum performance and design requirements for a variety of public lighting applications such as pathways, car parks and local roads.

Whilst the standard does encourage the use of adaptive lighting in certain public lighting applications in order to provide energy reduction, Clause 3.1 within the standard stipulates that when adaptive lighting is used, each dimming level shall be such that is complies with all the requirements of a relevant lighting category.

This means that solar Powered Lighting Systems that utilize adaptive lighting must still conform to a lighting standard that is relevant to the application.

In order to ensure that the minimum lighting level supplied by the solar powered lighting system is relevant, the designer and car park owner must refer to Table 2.5 of AS/NZS 1158.3.1 which covers the subcategory selection criteria for outdoor car parks.

Example Scenarios:

  1.  The level of activity and fear of crime in the car park between 5pm and 7pm is deemed to be “Medium” – The car park shall meet the minimum illumination requirements of Car Parks – Subcategory PC2 for these hours.
  2. The level of activity and fear of crime in the car park between 5pm and 7pm is deemed to be “Low” – The lights may dim to PC3 Levels for the hours after 7pm
  3. Should the primary illumination level for the car park during the hours of 5pm and 7pm be set to provide PC3 Levels, the lighting must not dim below this standard at all unless the lights are being completely switched off.

It is better to have lights completely switched off when the car park is not intended for use as opposed to having lights dim to a non-compliant illumination level.

Having lights completely switched off when the car park is not intended for use indicates that the facility is not open or is not in operation. It is also best practice to implement signage stating that the car park is closed during the hours that the lighting systems are not in operation.

Where a lighting installation operates at illuminance levels that do not comply to Australian standards, the facility owner or management body may be found liable should an incident occur in the car park when or if light systems are dimmed to a level that does not conform to the Australian standards.

 Outdoor Car Park Lighting Subcategories and Relevancy Selection Criteria

 AS/NZS 1158.3.1:2020 Table 2.5 provides the selection criteria for car park lighting installations.

There are 3 subcategories that apply to the primary car park area referred to as PC1, PC2 and PC3.

Selection Criteria

Activity Level

(Pedestrian/Vehicle Movements)

 Fear of Crime Applicable Lighting Subcategory
High High PC1
Medium Medium PC2
Low Low PC3

The selection criteria must be separately evaluated and the highest level of the selection criteria that is deemed suitable for the car park will determine the required lighting subcategory.

For example, even if the car park activity level is low but the fear of crime is medium, Subcategory PC2 should be the applicable subcategory.

There are also more stringent illumination levels required for disabled access parking areas and areas designated for pedestrian to cross roadways within car parks.

These Subcategories are not subject to the selection criteria and minimum conformance must always be met regardless of whether adaptive lighting systems (dimming) are in use within the car park.

  • Disabled Access Parking Areas – Subcategory PCD
  • Pedestrian Crossings with Car Park Areas – Subcategory PCX

Subcategory Light Technical Parameters (LTP’s)

 LTP’s (Light Technical Parameters) are the minimum or maximum (where applicable) calculation values required to conform to the relevant lighting subcategory.

  • Eh – Average Horizontal Illuminance
  • Eh is the average value of all ground level horizontally calculated illuminance points throughout the area of the car park. The average must exceed the Eh value that is applicable to the relevant lighting subcategory.
  • Eph – Point Horizontal Illuminance
  • Eph is defined by the absolute minimum Illumination point within in the lighting calculation grid and the value must exceed the minimum required Eph value that is applicable to the relevant subcategory.
  • Ue2 – Horizontal Illuminance Uniformity
  • The uniformity ratio is calculated using the Maximum and the Average horizontal ground level illuminance values and must NOT exceed the maximum value allowable under the relevant subcategory.
  • Epv – Point Vertical Illuminance
  • Epv is the calculated vertical illuminance measured at 1.5m above the ground level (i.e. typical chest height). The calculation is undertaken with the meter aimed 90° from the horizontal and in two opposite directions throughout all areas within 7.5m from the car parks extents.

NOTE: Point Vertical Illuminance (Epv) is only a requirement where subcategories PC1 and/or PC2 apply. Subcategory PC3 does not required vertical illuminance calculations.

The applicable LTP values for Outdoor Car Park Lighting Applications can be found in AS/NZS 1158.3.1:2020 Table 3.7.

Overview of Control Technologies

There are three commonly utilised control technologies in solar lighting systems that can provide adaptive lighting.

These technologies are illustrated and explained below:

a). PWM Timed Dimming Control
(Pulse Width Modulation)

 b). PIR Motion Detect Sensors
(Passive Infrared) 		 c). Wireless Control Systems
(Zigbee, LoRaWAN, GSM LTE) 

a). PWM Dimming and Timer Functions:

PWM Dimming is often utilized in Solar Powered Lighting Systems primarily to scale light output in lighting systems with smaller batteries.

PWM controllers can be pre-programmed to run lights at high levels for a set number of hours at the beginning of the night and then dim the light down to a lower light level for the remaining night-time hours in to conserve battery consumption.

Caution:

Some solar lighting manufacturers make use of PWM dimming controllers to combat autonomy periods in the event of poor weather conditions.

The result of this is that the lights will still appear to work, however the PWM control will gradually reduce light output as the battery is discharged and may result in a non-compliant lighting scheme.

b). PIR Motion Detect Sensors

PIR (Passive Infrared) Motion Detect Sensors are often integrated with PWM dimming controller devices for use during low level settings to boost light levels back to full output temporarily when motion is detected.

Caution:

For car park lighting applications, it is highly recommended that the use of PIR sensors are carefully considered.

Although AS/NZS 1158.3.1 does not state that PIR motion detect sensors can not be used in outdoor car parks, in most cases is not suitable or practical. This is primarily due to the fact that PIR sensors have limitations in detecing movement at long distances and/or at certain angles.

Additionally, most PIR Sensors have a delay between the time of detection and actual light switching. The delay is often only a few seconds however, in outdoor car park applications where both vehicle and pedestrian movements are to be considered, a delay or failure in detection could have undesireable outcomes.

 c). Wireless Control Systems

Wireless communications devices can be integrated into solar powered lighting systems and utilize the PWM controller in order to schedule dimming scenarios.

These systems are considered the most comprehensive in terms of functionality given that lighting systems can all be controlled, scheduled and monitored from one central location.

 Ensuring your Solar Car Park Lighting Design and Installation complies with the Australian Lighting Standards

To ensure that the car park solar lighting design conforms to the relevant subcategory requirements of the Australian lighting standards, the following steps are recommended:

  1. Confirm with the designer and or supplier of the proposed solar lighting systems if the product needs to make use of adaptive lighting controls and if so, consider whether that is going to suitable for the car park.
  2. If Adaptive Lighting Controls are to be used, ensure that the designer has designed allowing for the lowest dimmed setting to still comply to the relevant subcategory applicable.
  3. Confirm that the subcategories chosen for the design are in fact suitable by referencing AS/1158.3.1:2020 Table 2.5, surveying car park activity and fear of crime.
  4. Check that the lighting design includes all the Light Technical Parameters (LTP’s) applicable to the relevant subcategory.
  5. Verify that the average horizontal illuminance (Eh), point minimum illuminance (Eph) and uniformity ratios meet the requirements of the relevant applicable subcategory.
  6. Where the car park is to meet either subcategories PC1 or PC2, verify that the lighting design includes Epv calculations (Point Vertical Illuminance).
    It is common for inexperienced lighting designers to exclude these calculations and to only provide (Eh) calculations for horizontal illuminance.
  7. Ensure that separate calculation grids are included specifically for any disabled parking spaces (PCD) and car park pedestrian crossings (PCX). Additionally, confirm with the designer that these calculations will be sustained at their minimum required levels regardless of any adaptive lighting controls.
  8. Check that the designer has applied an appropriate maintenance factor to the design that will cover any depreciation of light output over the life of the lighting installation.
  9. Ensure that the supplier of the solar lighting systems provides sufficient evidence to prove that the solar panels will provide enough power and that the battery capacity is sufficient for sustaining the illumination levels required by the relevant lighting subcategory for the timeframes needed with enough autonomy (battery backup) to cover poor weather periods.

A copy of the AS/NZS 1158.3.1:2020 Lighting for roads and public spaces can be obtained from the Standards Australia website – https://infostore.saiglobal.com/en-us/Standards/AS-NZS-1158-3-1-2020-117844_SAIG_AS_AS_2808804/