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The absence of meteorological data to identify the energy resources and the available energy potential represented a major obstacle in some areas in Djibouti. To solve this data problem, in this paper, wind and solar potential were assessed by collecting daily and monthly wind and solar data for the period from 1 January to 31 December 2020, for Herkalou and Lake Assal site. This study highlights that the wind resources in the Lake Assal location are falling into class 7 with high wind speed value of 16 m.s-1 and the wind energy reaching1700 kWh/m2 at 100 m height above ground level. While the Herkalou site shows a lower potential with value of 7.5 m.s-1 and 160 kWh/m2. The solar potential shows a similar distribution and a constantly high level of solar radiation throughout the year, with the monthly maximum global radiation peaks of around 900 W/m² between 11.00 and 14.00 pm for both sites. The highest monthly average of global solar irradiation values was 5.29 kWh/m2 day-1 and 6.90 kWh/m2 day-1 in March for Herkalou and Lake Assal, respectively. Results obtained in this study are favorable to deploying the solar and wind technologies for the studied sites.

Djibouti has an ambitious program to develop and expand its energy demand to satisfy local demand and increase the energy access in rural and urban areas. The renewable energy development is vital in Djibouti’s strategy including 2020’s vision. To increase investment in clean energy by reducing dependence on oil and derivative products, Djibouti want to be the first sub-Saharan African nation using 100% clean energy. This paper examines, for the first time, wind energy potential at Djibouti-city using 5-years (2014–2018) wind speed data collected at 10 m height of wind power using Weibull parameters. Such a study was not feasible before due to the lack of data in this urban area. The results showed the possibility to implement and develop urban wind energy sector in Djibouti-city for domestic applications. The statistical wind speed, the wind rose, and the power density were computed. This study is also part of the implementation project of five micro wind turbines of 1–25 kW in different height areas. The strong wind flows are Eastern and Western over the considered period.The Polaris P12-25 wind turbine provided the best capacity factor (CF = 9.629%) and energy output (AEP = 2.1 × 104 MWh) comparing to the others technologies because the study site having low monthly wind speeds. Finally, according to the analysis of wind power production, Djibouti-city needs to install the wind turbines with high hub height greater than 30.5 m for efficient harvesting. Keywords: Wind speed, Weibull distribution, Wind power density, Wind turbine, Capacity factor, Urban, Djibouti

International audience; The current challenge is to reduce the building energy consumption, in hot and humid climates, for which air conditioning is widespread. Up to now, the lack of criteria that identify the available cooling resources and the level of performance of technical solution has represented the major obstacle. To address these issues, the authors propose a new set of indicators to fully inform the decision-making process of the bioclimatic design of fully space-conditioned buildings in a hot and humid climate. This set of indicators provides an overview of the exploitable environmental resource (external air through external convection, natural ventilation and sky radiation cooling) referred as the Environmental Resource Indicators and of the capacity of the building to exploit those resources referred as the Building Performance Indicators. The indicators are implemented for a very basic two-story residential building in the hot, humid climate of Djibouti. The case study shows not only the ability of the indicators to reflect the bioclimatic performances of the buildings but also their ability to give an overview of the building heat exchanges, from which the implication of improper bioclimatic solutions on building cooling consumptions can easily be identified. These indicators are a means to help choose which technical solutions are most suited to the local climate, which is very useful for designers and architects in the early stages of building design.

International audience; In the Sub-Saharan African countries like Djibouti, the energy situation, the high rate of urban areas growth and the inadequate techniques of construction offer an exciting potential for the bioclimatic approach and sustainable construction. However, this poorly explored potential requires an investigation of different construction types in Djibouti and a good knowledge of the behavior of buildings components. Further a low energy building can be obtained because of the good realization of all its components. In fact, roofs call for attention as they represent a large part of a building's total surface area and amount of absorbed solar radiation. The goal of this paper is to investigate the benefit of using double skin-ventilated roofs for reducing cooling load under the Djiboutian climate. It is a first step towards ideas that will transform local construction practices to make them effective in energy, economic and functional dimensions. During investigation, we compared a ventilated roof assembly with traditional configuration after that the consistency of our model was validated with experiment of the literature findings. The computational fluid dynamics (CFD) model has been used for the characterization of the airflow and heat transfer phenomena in the ventilation cavity and provide fundamental information about the thermal performance of the roof. The results show the amount of the energy saving obtainable by the double-skin ventilated roof.

The aim of this thesis is to elaborate efficient optical nanoantennas (NAs) as innovative tools for probing the electromagnetic optical field in the neighbourhood of the structures used in nano-optics (photnics crystals, plasmonic devices, etc). A NA considered here consists of a metal nanostructure positioned onto the apex of a conventional near-field fiber probe used in collection mode (Photon Scanning Tunneling Microscopy configuration). Such a nano-structure acts as a key connection between the electromagnetic field at the sample surface and the local probe, giving to the probe a specific sensitivity to the vectorial electromagnetic field. NAs will be designed to provide optical information still inaccessible with conventional near-field optical microscopy for responding to the present and future needs of the growing nano-optics community. In the first part, we propose a bowtie nano-aperture (BNA) is recently proposed as an alternative solution to bowtie nano-antenna for concentrating light to the nanoscale and we explain the fabrication of a BNA with specific size at the extremity of a polymer optical fiber. In the second part, we propose a near-field imaging concept for obtaining a complete experimental description of the structure of light in three dimensions around nano-devices. Our approach is based on a near-field microscope able to simultaneously and independently map the phase and amplitude distributions of two orthogonal electric-field components at the sample surface. In last section, we present a theoretical study of the bowtie nano-aperture in order to elucidate the spectral behavior and the origin of its resonance mode in the gap of a BNA.; L'objectif de cette thèse est de concevoir et élaborer des outils innovants, baptisés nano-antennes (NAs), pour sonder le champ électromagnétique optique au voisinage des structures de la nanooptique. Une NA est ici une nanostructure métallique placée à l'extrémité d'une sonde locale fonctionnant en mode collection. Une telle structure joue le rôle de relais entre le champ électromagnétique optique à la surface de l'échantillon et la sonde locale, attribuant à la sonde une sensibilité spécifique vis-à-vis du champ électromagnétique vectoriel. Les nano-antennes seront conçues de manière à fournir une information optique encore inaccessible par le biais de la microscopie en champ proche conventionnelle, pour répondre aux besoins actuels et futurs de la nano-optique. Dans la première partie, nous proposons une nouvelle configuration de sonde locale la nano-ouverture papillon complément d'une nano-antenne papillon et nous exposons sa fabrication aux dimensions spécifiques, à l'extrémité d'une fibre optique en polymère. Dans la deuxième partie, nous présentons une nouvelle configuration de microscopie en champ proche permettant l'accès aux lignes de champs électriques et magnétiques optiques 3D au dessus d'un échantillon, avec une résolution sub-longueur d'onde. Le microscope proposé permet de cartographier simultanément et indépendamment les distributions des amplitudes complexes des deux composantes du champ électrique transverse. La dernière partie est consacrée à l'application d'une méthode numérique dite FDTD afin d'étudier le comportement spectral et l'origine de l'exaltation au niveau de la partie centrale d'une nano-ouverture papillon.