Abstract
Because of the absence of lighting calculation tools at the initial stage of tunnel design, the lighting systems are usually over-dimensioned, leading to over illumination and increased energy consumption. For this reason, a fine-tuning method for switching lighting stages according to the traffic weighted L20 luminance is proposed at no additional cost. The method was applied in a real –case scenario, where L20 luminance of the access zone at eleven (11) existing tunnels was calculated. The traffic weighted method of CR14380 was used in order to calculate the actual luminance levels for the entrance zone. The new transition zone, which decreases luminance curves, was produced and compared with the existing ones. Thus, a new switching control was proposed and programed for the Supervisory Control and Data Acquisition (SCADA) system of the tunnel. The signals of the corresponding eleven L20 meters for a period of eight days were used and the corresponding annual energy consumptions were calculated using the proposed switching program for each tunnel. The results were compared with a number of scenarios in which the existing lighting system was retrofitted with Lighting Emitting Diodes (LED) luminaires. In these scenarios, the new luminaire arrangement was based not only on the existing luminance demand value for the threshold zone, but also on the newly proposed one with two different control techniques (continuous dimming and 10% step dimming). The fine-tuning method for switching resulted in energy savings between 11% and 54% depending on the tunnel when the scenario of the existing installation at no extra cost was used. Energy savings, when LED luminaires were installed, varied between 57% (for the scenario with existing luminance demand value for the threshold zone and 10% step dimming) and 85% (for the scenario with the new calculated luminance demand and continuous dimming).
Highlights
Artificial lighting corresponds to more than 20% of the world’s electricity consumption [1].In Europe (EU28) there are more than 1.6 million km of illuminated streets that annually consume approximately 35 TWh) at a cost of $4 billion euro for the public authorities [2]
During the last decade there has been ongoing research activity focused on energy management using various types of renewable energy sources [3,4,5], on recycling [6], on safety [7,8,9,10], and a concentrated effort has been made for making street lighting systems sustainable [11,12,13,14,15,16,17,18,19] and environmentally friendly [20,21,22]
The scope of this paper is to propose a control strategy according to the new luminance level requirements based on the traffic weighted L20 method (CR14380, [31]) in existing tunnels
Summary
Artificial lighting corresponds to more than 20% of the world’s electricity consumption [1].In Europe (EU28) there are more than 1.6 million km of illuminated streets that annually consume approximately 35 TWh) at a cost of $4 billion euro for the public authorities [2]. Unlike buildings, where daylight minimizes lighting needs [33,34,35], in tunnels it results in an increased number of installed luminaires as well as in increased power consumption for each luminaire [31,32] This design approach increases energy consumption during the day, since the threshold luminance (Lth) is directly linked to the access zone luminance, which is represented by L20. The latter is defined as the luminance of the tunnel entrance surrounding areas within a conical field of view of 20◦ , within stopping distance of design speed. The control of the active lighting stages of the tunnel is crucial for minimizing energy consumption during the day
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