Blogs
The support of Earth Observation for energy transition and climate mitigation in the urban environment and conditions of Cairo, Egypt
Article editors: Eleni Athanasopoulou, Stavros Bigkos and Panagiotis Kosmopoulos, National Observatory of Athens, Greece
Introduction
This study emphasizes how Earth Observation (EO) datasets and derived products can inform and accelerate Cairo’s solar energy transition for climate mitigation. Satellite-derived aerosol (AOD) and cloud products, combined with urban footprint mapping and photo-voltaic (PV) simulation tools, quantify the attenuation of solar irradiance in Cairo and enable rooftop PV potential estimates and operational planning. The study finds substantial aerosol-induced attenuation and a trend of increasing aerosols during 2010–2019. Concerning PV production, the percentage of energy sufficiency that on-roof solar panels in Cairo would lead to, are not negligible and could contribute to the transformation into a green, autonomous smart city.
Materials and Methods
The data & EO products used include the Copernicus Atmosphere Monitoring Service (CAMS) total AOD at 550 nm (MODIS assimilation used for correction) and the EUMETSAT SAFNWC cloud optical retrievals and products. The solar radiation is estimated through climatological radiative simulations (SODAPRO) and the PVGIS outputs are used for PV energy conversion. The exploitable rooftop area is estimated from the OpenStreetMap building footprints processed with QGIS (and Urban Atlas where applicable).
The metrics calculated are the:
Aerosol Modification Factor (AMF = GHI0 / GHI00) and the
Cloud Modification Factor (CMF = GHI / GHI0) [1].
These metrics range 0–1 (1 = no attenuation).
[1] to separate aerosol and cloud attenuation effects on Global Horizontal Irradiance (GHI)
Results
3.1 Aerosol & Cloud attenuation (Cairo specifics)
The monthly average sums of energy losses due to aerosols and clouds show that the aerosol signal dominates over cloud losses in most months, due to frequent dust events from the Western Desert (monthly sums peak sharply in spring). The annual trend (2010–2019) of AMF tends to decrease (i.e., aerosol influence increases over the decade; Figure 1), implying growing aerosol burden and increasing negative impact on PV potential.
Figure 1. The annual AMF (left) and CMF (right) trends (2010–2019) for Cairo, Egypt.
The study has constructed an idealized scenario of maximum rooftop PV exploitation. The high rooftop availability for Cairo, plus the high solar resources are partially offset by aerosol attenuation. Realistic energy security estimates must therefore account for aerosol losses quantified via EO.
Discussion
Satellite AOD and cloud products allow planners to correct clear-sky PV yield estimates to observed all-sky yields (AMF/CMF). This produces realistic energy production forecasts necessary for investment appraisal and policy targets. Combining (OSM/Urban Atlas) building footprints with high-resolution solar climatology (PVGIS) yields maps of exploitable rooftop area. According to the ideal energy planning scenario, Cairo has a high adequacy percentage, with rooftop solar panels able to produce energy just over a quarter of the city’s consumption.
Conclusion
EO products are essential to produce realistic PV potential assessments and to operationally support rooftop PV deployment in Cairo. This is due to aerosol (primarily dust) attenuation, which is the dominant atmospheric loss term for Cairo. Aerosol impacts have increased over 2010–2019, reducing the effective PV yields. Still, the city could benefit from an upgraded urban design that will take into consideration the exploitation of solar energy through the roofs of its buildings to cover a part of the daily energy demands.
This article is a synopsis of the recently published scientific article in the Journal of Environmental Sciences Proceedings: Vigkos, Stavros, Panagiotis G. Kosmopoulos, and Alexandros Papayannis. 2023. “Solar Photovoltaic Energy Production Conditions in the Urban Environment of Athens, Cairo, Granada and Vienna” Environmental Sciences Proceedings 26, no. 1: 24. https://doi.org/10.3390/environsciproc2023026024