Lighting System Modernization as a Source of Green Energy

The use of formal methods and artificial intelligence has made it possible to automatically design outdoor lighting. Quick design for large cities, in a matter of hours instead of weeks, and analysis of various optimization criteria enables to save energy and tune profit stream from lighting retrofit. Since outdoor lighting is of a large scale, having luminaires on every street in urban areas, and since it needs to be retrofitted every 10 to 15 years, choosing proper parameters and light sources leads to significant energy savings. This paper presents the concept and calculations of Levelized Cost of Electricity for outdoor lighting retrofit. It is understood as cost of energy savings, it is in the range from 23.06 to 54.64 EUR/MWh, based on real-world cases. This makes street and road lighting modernization process the best green “energy source” if compared with the 2018 Fraunhofer Institute cost of electricity renewable energy technologies ranking. This indicates that investment in lighting retrofit is more economically and ecologically viable than investment in new renewable energy sources.

Rational Basis for Light Emitting Diode Street Lighting Retrofit Luminaire Selection

Many municipalities are beginning to undertake efforts to retrofit their existing high pressure sodium (HPS) street lighting with LED (light emitting diode) luminaires. Unlike HPS lighting systems, which are available in a limited range of standard wattages and configurations, LED street lighting systems vary widely in wattage and physical configuration. Moreover, the technological performance of LED lighting continues to improve, whereas HPS is a mature technology with substantial improvements unlikely in the future. To develop a sound basis for selecting LED lighting systems for retrofit street lighting, photometric simulation calculations under a range of pole spacing, road width and luminaire wattage were performed. The results indicated that LED luminaires can have substantially lower wattage than HPS luminaires to produce the same light levels on the road. Further, LED luminaires tend to direct more of their output onto the road compared with HPS luminaires. As a result, LED luminaires can be used that produce substantially fewer lumens overall than HPS systems. Because the white light from LED sources makes illuminated street scenes appear brighter than the yellowish light from HPS lamps, even further reductions in light output can be accomplished with LED street lighting systems to match the same visual effect under HPS.

A case study of lighting retrofit to improve building energy efficiency and lighting quality by using luminaires with nano optical coating

Lighting retrofit is a common technique to reduce lighting energy use and to improve lighting quality. It is usually performed by replacing the lamps in the existing luminaires with more efficient lamps. Despite the high potential to enhance lighting performance by improving other parts of the luminaires such as reflectors, lighting retrofits usually keep their designs unchanged and focus on the change of the lamps. In this case study, an alternative lighting retrofit method - the replacement of reflectors using a nano optical coating - was tested in a typical office in Hong Kong. The case study used a luminaire with a highly reflective nano optical coating. The pre- and post-retrofit illuminance level, illuminance uniformity, glare and lighting energy use were measured. The results show that the use of the nano optical coating enables the reduction of light tubes in the office and thus the lighting energy consumption without lowering the lighting quality. The lighting retrofit enhances the illuminance uniformity in the office by 14.6% while keeping the illuminance level and discomfort glare within the satisfactory level. It also lowers the lighting energy use of the office by 37.5%.