HomeMagazine ArticleA street lighting case study from a South African municipality

A street lighting case study from a South African municipality

Best practices within the lighting planning department as well as special projects undertaken to enhance and better the performance of public lighting to ensure energy efficiency and increased reliability has been a key focus area for eThekwini municipality, writes lighting planning engineer, Criselda Bisram, BSC Engineering Electrical (PR.Eng).

The Lighting Planning Branch falls under the Medium and Low Voltage (MV/LV) Operations Department and is responsible for the planning, design, specification and procurement, inspection and maintenance planning of the public lighting infrastructure for eThekwini municipality. This includes the planning and design of new installations, upgrading of existing lighting infrastructure, research and investigation into new lighting technologies and bulk replacements. A major responsibility for this branch is the planning and design of capital projects. The annual capital budget for the financial year under review, that being 2015/2016, was ZAR14.2 million (US$920,000) and projects were planned for upgrades from conventional technologies to LED street lighting, major route improvements, new major routes, lighting of parks and sundry lighting.

There are approximately 187,000 street lighting installations, 49 cemeteries, 250 parks, 12 beaches, 17 subway lanes, 31 swimming pools and 93 stadia and sports fields for which the municipality is required to provide lighting.

Municipalities can implement smart lighting systems

eThekwini Electricity is currently researching various street lighting technologies and cost-reduction solutions, and an example of this is the implementation in 2015 of eThekwini’s first smart lighting system. In an effort to improve service delivery, Schreder’s Owlet remote management system, which is capable of reporting the status of individual luminaires whilst saving energy, was implemented. Phase one of this project is a pilot project to assess the feasibility for the use of the system on all major routes and freeways.

According to the South African Electricity Regulation Act (4/2006), there are specific requirements for the adoption of Energy Efficiency practices in public lighting, these being:

  • Street and highway lighting must be energy efficient and the licensee must ensure that it is switched off during the day; and
  • Streetlights must be fitted with systems that allow for remote reduction of power especially during capacity constraints.

eThekwini selected a telemanagement solution designed specifically for the effective, efficient and reliable management of public lighting networks. Phase one of the project consisted of 20 luminaires fitted with an integrated luminaire controller, mounted onto the control gear tray, with external antenna for telemangement-based control and monitoring.

The communication module is based on the industrial standard communication protocol IEEE 802.15.4 (using Zigbee Meshnet [XBee]) to provide a robust and reliable mesh network, ensuring a secure and non-proprietary bidirectional control platform. The system operates in the non-proprietary range of the 2.4GHz ISM band. Each individual luminaire acts as a node in a large mesh network of up to 140 nodes, all controlled from one segment controller. Each luminaire controller has a uniquely identifiable address, to ensure individual monitoring and control. The segment controller then joins a central Web-Management Server to create a single contiguous control environment. The luminaire controller is designed to perform tasks that allow for control, energy saving, monitoring and reporting.

Lighting informal settlements

Another project linked directly to energy efficiency and cost reduction initiatives is the provision of lighting for ablution containers for informal settlements. One of the major challenges faced in eThekwini Municipality is the provision of water and sanitation as well as electricity to informal settlements. Due to a lack of existing infrastructure and the backlog, ablution blocks/containers are provided as an interim measure to cater for the sanitation requirements for these settlements. Ablution blocks are combined water and sanitation facilities consisting of both male and female toilets, showers, basins and laundry facilities. A critical service required is the provision of electricity for lighting both inside and outside of these containers. Various methods to supply electricity to these areas were investigated. After careful consideration, an executive decision was taken to procure and implement the use of solar panel, battery and LED modules to provide lighting in the absence of existing infrastructure. In 2012, eThekwini Municipality’s electricity department was allocated ZAR20 million (US$1.3 million) for streetlight retrofit programmes. The budget was allocated for the retrofit of LED streetlights to replace the standard HID type lamps such as high pressure mercury vapour and high pressure sodium vapour lamps.

The LED luminaires were used to replace 80W HPMV streetlights on the main residential roads, 150W HPS streetlights on the connecting roads and local distributor roads and 250W HPS streetlights on important urban traffic routes.

These roads are classified as B1, A4 and A3 respectively.

A) 2,888 x 80W HPMV luminaires retrofitted with 59W LEDlume LED streetlights with an energy saving of 31% per streetlight. It is important to note that the actual power consumed by an 80W streetlight is 88W.

B) 974 x 150W HPS luminaires retrofitted with 88W LEDlume LED streetlights with an energy saving of 41% per streetlight.

C) 971 x 250W HPS luminaires retrofitted with 148W LEDlume LED streetlights with an energy saving of 41% per streetlight.

Recommendations made in 2013 after the conclusion of the project

“Testing of different lighting technologies should continue until such time as a reliable, affordable and compliant luminaire is found. It would appear as though the LED solution is more feasible from an energy saving perspective, although it is still about seven times the cost of conventional high intensity discharge (HID) luminaires.”

Since these recommendations were made, the cost of LEDs has significantly improved and various funding options are now being evaluated for retrofitting old and existing streetlighting with the equivalent LED alternative. The major challenge of the LED equivalent is the higher capital cost. For example, the cost of the LED equivalent of a 150 Watt High Pressure Sodium Streetlight luminaire is approximately three times the initial cost of the HID. This makes the initial buy in from the executive council challenging even though the energy savings will result in reduced costs. However, with the evolution of technology, LEDs currently provide 55–60% energy savings and these numbers continue to improve. LEDs have become much more cost effective since 2013 and will thus be implemented in the foreseeable future. ESI