Use of diffusers materials to improve the homogeneity of sunlight under pergolas installed in road tunnels portals for energy savings

• Shifting a tunnel threshold zone with a pergola allows remarkable energy savings.
• However, the lighting uniformity on the road is poor.
• Introducing diffusers between the pergola beams solves this lack of uniformity.
• Mock-ups, computational simulations and theoretical models yield very good results.
• Future research with other materials must be carried out.

In spite of the benefits of shifting the threshold zone of road tunnels by means of pergolas, installed before their portal to save energy in the electrical lighting, the lack of uniformity in the road under these structures makes them a non accurate solution in terms of visual performance and, hence, road safety. In this work, a new solution, consisting on the introduction of a diffuser material in the spaces between beams of the pergola is proposed. The measurements and results in a scale mock-up, a computational simulation and the comparison with a theoretical model, as well as the potential impact in real tunnels are presented and analyzed.

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