A carbon footprint and energy consumption assessment methodology for UHI-affected lighting systems in built areas

• Assessment of the carbon footprint as a function of the urban heat island effect.
• LED lamps performance depends upon the temperature variation produced by UHI.
• A 3.3 °C temperature increase (UHI) can raise the CF from public lighting of 1%.
• A mitigation of the UHI of 1 °C can save up to 230 tCO2eq/yr for the city of Rome.

This paper investigates the effects of urban heat island (UHI) on outdoor lighting systems in terms of GHG emissions: a novel methodology is proposed to assess the carbon footprint (CF) change of lighting services in built areas caused by UHI-induced ΔT with particular focus on the evaluation of the energy consumption. The methodology can be applied also to other activities affected by the UHI, such as HVAC and transport systems. In particular, ΔCF was introduced by a two-fold approach: the quantification of the CF change due to UHI (as difference between CF in an UHI-affected case and CF for an UHI-less case) and the CF change produced by a 1 °C temperature change. A focus on LED lamps was developed: the lifetime of LEDs exponentially decreases with increasing temperature and the luminous flux exponentially decays with operation time. UHI (i.e. the increase in ambient temperature) affects the lifetime and the luminous flux of lamps producing higher energy consumption and higher replacement rates. Results showed that a positive ΔT due to UHI produces a positive ΔCF, which also becomes economically relevant in long-term scenarios. A case study was analyzed by applying the proposed methodology to Rome outdoor public lighting.