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Tsankov, et al.

(iv) Mercury lamps of 80W, 125W, 250W, and 400W. including outdoor lighting. In compliance with these
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(v) LED modules of 20–150W. standards, the audit included an inventory of all lighting
This period marked the appearance of the first fixtures, measurements of installed and consumed
demonstration projects for outdoor LED lighting. power, nighttime observations of lighting quality, and
After 2010, the rapid increase in efficiency and verification of the system’s conformity with applicable
reduction in the cost of LED technology coincided lighting design criteria.
with the completion of the 15–20-year service life of The audit results revealed that over 90% of the
the luminaries from the previous transition to sodium existing luminaires equipped with HPS lamps had
lamps. This convergence accelerated the widespread reached the end of their technical and operational
adoption of LED lights in outdoor lighting and initiated life cycle. Common problems identified during the
the transition from HPS and CFLs to LED light sources. survey were mechanical failure of fixings, missing
The process was gradual, but all new street lighting or damaged diffusers (Figure 1A-D), and a lack of
systems were implemented with LED luminaires. The moisture protection for the starting and control gear
expansion of LED use in recent years has been highly (Figure 1D). In some cases, LED and CFL lamps were
dynamic across different Bulgarian cities, making it installed in luminaires originally designed for HPS
difficult to establish precise general data. lamps (Figure 1C-F), leading to reduced luminance and
illuminance levels on the roadway.
2. Methodology Steel street and park poles predominate in the
central urban areas of the settlements, while reinforced
This study presents the development, results, and the concrete poles are mostly found in the outlying
associated energy and environmental benefits of a districts and villages. A significant proportion of
project aimed at the energy-efficient modernization of luminaire cantilevers exhibit large tilt angles,
street lighting systems in the Bulgarian municipality of ranging from 30° to 60°, which are inappropriate for
Pavlikeni. the roadway widths, ranging from 4 to 9 m. These
The research methodology consisted of the following angles reduce the effective roadway coverage and
stages: illuminance while increasing glare and causing an
(i) Conducting an energy audit of the existing street unnecessarily large portion of the luminaire’s light
lighting systems. output to be directed onto the opposite sidewalks and
(ii) Optimizing street lighting design through building facades. In some cases, the luminaire bracket
computational modeling using specialized software. was misaligned, either rotated incorrectly around the
(iii) Implementing a modern street lighting management horn axis or oriented in the opposite direction from
and control system. the roadway.
(iv) Assessing energy efficiency, financial savings, Based on a detailed survey of the condition of the
and environmental benefits of the proposed street and park lighting fixtures, the pole network, power
modernization. lines, and the locations of the transformer substations
and street lighting cassettes, a digital graphical model
2.1. Energy audit of the existing street lighting of the existing street lighting system in Pavlikeni was
systems developed. This model integrates the survey data across
Conducting an energy audit of the existing street lighting separate map sheets, on which the collected information
systems is an important initial stage, as confirmed by was plotted. Different types of luminaires, poles, power
several authoritative studies. 16-20 lines, and the positions of the control points and cabinets
The energy audit of the street lighting systems are indicated using appropriate graphic symbols.
in the municipality of Pavlikeni was carried out in Figure 2 presents a section of one such map sheet from
accordance with the applicable Bulgarian legislation, the digital graphical model, which was developed using
specifically Ordinance No. E-RD-04-05/04.10.2016 AutoCAD (Autodesk Inc., USA). The graphic model is
issued by the Ministry of Energy, which regulates the accompanied by detailed information about the existing
structure, content, and methodology for energy audits lighting systems on all streets: The distances between
of industrial systems. The audit also aligns with the the poles; the type and height of the poles; the length
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principles and procedures outlined in EN 16247- and angle of the bracket for mounting the luminaires;
2:2014, which establishes the European standard the type of luminaire and the technology; and the power
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for energy audits of buildings and technical systems, of the light sources.

Volume 22 Issue 6 (2025) 182 doi: 10.36922/AJWEP025310242