Reducing lighting electricity use in underground metro stations

Abstract

Lighting systems are usually one of the largest electrical end-uses in underground metro stations. Taking into account that budget restrictions in publicly owned companies hinder energy efficiency retrofit projects that require high initial investments, affordable energy saving strategies are needed. This paper presents a low-cost approach for reducing lighting electricity use in underground stations, without affecting passengers' comfort or the metro operator's service. For this purpose, an adaptive lighting strategy of dimming the illuminance levels of artificial light sources has been developed. Dimming controls are based on the occupancy of the station, and the preventive maintenance and cleaning cycles of the luminaires. The stations' monthly occupancy patterns are defined through the k-means clustering technique. To illustrate its effectiveness, the method was applied to 115 underground stations of the Barcelona metro network. The results revealed overall electricity savings of 255.47 MW h on a biannual basis, which represents 36.22% of the stations' baseline lighting consumption. Individual energy savings were found to range from 25 to 87.5 MW h/year in the stations of the Barcelona metro network, depending on the number and profile of station users. The research findings will undoubtedly be useful for the future energy efficiency project plans of worldwide metro operators and managers of other underground spaces.Peer ReviewedPostprint (author's final draft

Technical–Economic Analysis of the Solutions for the Modernization of Lighting Systems

“…Other solutions that help reduce electricity consumption are the use of light dimming systems within lighting sources. A study carried out in 115 metro stations in Barcelona found that by using intelligent lighting control systems, depending on the occupancy of the stations, a reduction of 36.22% in the basic consumption of lighting systems was achieved [32]. A similar percentage reduction in electricity (30%) was also identified in the case of street lighting that uses an adaptive lighting system depending on traffic conditions [33].…”

Literature review - Energy saving potential of user-centered integrated lighting solutions

“…This dimming strategy is meant to mainly offset the dirt accumulation on the luminaires; and luminaires are dimmed at the beginning of their maintenance period (and after they are cleaned) to ensure that minimum level requirements are met, but upper limits are not exceeded. This approach becomes very effective with low maintenance installations and dirt environments, such as metro stations, where energy saving can be up to 33% of the stations' baseline lighting consumption (Casals, Gangolells, Forcada and Macarulla, 2016) . Moreover, this strategy needs minimum investment, since the only extra equipment needed is a digital addressable lighting interface (DALI) controller.…”

Characteristics and assessment of the electricity consumption of metro systems: A case study of Tianjin, China

“…First, the variable outdoor climate influences the energy consumption of the VAC system 28,29 . Second, the floor area determines the setting of lighting and other facilities 30 . Third, ridership can affect the energy consumption of ventilation fans and escalators and lifts (elevators) when these devices are running at variable frequencies.…”