Simulating the global climate in fine granularity is essential in climate science research. Current algorithms for computing climate models are based on mathematical models that are computationally expensive. Climate simulation runs can take days or months to execute on High Performance Computing (HPC) platforms. As such, the amount of computational resources determines the level of resolution for the simulations. If simulation time could be reduced without compromising model fidelity, higher resolution simulations would be possible leading to potentially new insights in climate science research. In this project, broadband radiative transfer modeling is examined, as this is an important part in climate simulators that takes around 30% to 50% time of a typical general circulation model. This thesis project presents a convolutional neural network (CNN) to model this most time consuming component. As a result, swift radiation prediction through the trained deep neural network achieves a 7x speedup compared to the calculation time of the original function. The average prediction error (MSE) is around 0.004 with 98.71% of accuracy. / Högupplösta globala klimatsimuleringar är oumbärliga för klimatforskningen.De algoritmer som i dag används för att beräkna klimatmodeller baserar sig på matematiska modeller som är beräkningsmässigt tunga. Klimatsimuleringar kan ta dagar eller månader att utföra på superdator (HPC). På så vis begränsas detaljnivån av vilka datorresurser som finns tillgängliga. Om simuleringstiden kunde minskas utan att kompromissa på modellens riktighet skulle detaljrikedomen kunna ökas och nya insikter göras möjliga. Detta projekt undersöker Bredband Solstrålning modellering eftersom det är en betydande del av dagens klimatsimulationer och upptar mellan 30-50% av beräkningstiden i en typisk generell cirkulationsmodell (GCM). Denna uppsats presenterar ett neuralt faltningsnätverk som ersätter denna beräkningsintensiva del. Resultatet är en sju gångers uppsnabbning jämfört med den ursprungliga metoden. Genomsnittliga uppskattningsfelet är 0.004 med 98.71 procents noggrannhet.

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[pt] A irradiação solar é vista como uma importante fonte de dano aos cabelos, contudo, medir instrumentalmente as consequências da sua interação com os diferentes constituintes da fibra capilar ainda é um desafio. Neste trabalho, investigou-se o potencial da metodologia de flexabrasão em medir as alterações nas propriedades mecânicas de fibras de cabelo decorrentes dos danos estruturais ocasionados pelas radiações solares. Para isto, desenvolveu-se um experimento in-vitro, no qual amostras de cabelo humano, simulando diferentes níveis de sensibilização química (natural, descolorido, colorido e alisado com formaldeído), foram submetidas a diferentes níveis de radiação emitida por uma lâmpada de xenônio. Após análise estatística dos dados obtidos, observou-se que a metodologia de flexabrasão é capaz de captar a influência da radiação solar na resistência mecânica de fibras de cabelo, sobretudo em cabelos naturais a partir de 60 horas de exposição à lâmpada de xenônio, o que equivale aproximadamente a 5 meses de exposição solar na cidade do Rio de Janeiro, para pessoas que ficam diretamente expostas ao sol por cerca de 1,5 h por dia. Desta forma, concluiu-se que a flexabrasão é uma possível metodologia para avaliação do fator de proteção solar oferecido por produtos cosméticos capilares. / [en] Solar radiation is an important source of damage to hair fibers. However, it is still a huge challenge to instrumentally measure the consequences of its interaction with the fibers constituents. In this work, the flexabrasion methodology has been investigated as a potential tool to quantify the alterations on hair mechanical properties due to structural damages caused by solar radiation. For that, an in-vitro experiment has been developed, in which human hair samples, simulating different levels of chemical sensitization (natural, bleached, dyed and straightened with formaldehyde), were submitted to different levels of radiation from a xenon lamp source. Statistical analysis of the data obtained with the methodology showed that it is able to capture the influence of solar radiation on hair mechanical resistance, especially when using natural fibers from 60 hours of exposure onwards, what would be equivalent to around 5 months of real solar exposure at Rio de Janeiro, on people that are directly exposed to the sun during 1,5 h per day. Thus, one can conclude that flexabrasion is a methodology option to evaluate the photo protection efficacy offered by hair care products.

This thesis provides insights to what is peculiar about a solar sail attitude and orbit control system and provides the assessment, in the form of a feasibility study, of the effectiveness of sail tip vanes as a control hardware to escape the Earth sphere of influence. The demonstrator aims to prove the technology for the Sunshade project, a constellation of solar sails located at the Lagrangian point L1 to obscure part of the solar radiation directed towards earth. Solar sailing poses a few fundamental challenges to spaceflight and it is a yet-to-be-proven branch of space engineering. Other tentative design exist but there is no standard to follow or off-the-shelf component that can be straightforward used. Moreover the scalability to the final project has to be accounted for in every step of the project.</p><p>The project is divided in a preliminary dimensioning, followed by a Simulink® based simulation which tests preliminary decisions. The simulation, performed on an orbit on the ecliptic plane, integrates models of Earth’s eclipse and environmental disturbance torques.  The escape time for a 100 m solar sail is found to be 1215 days, with a nonlinear PD control algorithm and sail tip vanes as the only control hardware. Attention is also posed on the consequence of a simplified sail film deformation in terms of centre of pressure to centre of mass off-set. / I detta examensarbete studeras vad som är speciellt med solsegels system för attityd- och bankontroll och ger en bedömning, i form av en möjlighetsstudie, av effektiviteten hos flöjlar som sätts på seglets hörn som kontrollhårdvara för att lämna jordens inflytelsesfär. Demonstratorn syftar till att bevisa tekniken för Sunshade-projektet, en konstellation av solsegel belägen vid lagrangepunkten L1 för att skugga en del av solstrålningen riktad mot jorden. Solsegling innebär några grundläggande utmaningar för rymdfärden och det är en ännu inte bevisad gren av rymdteknik. Annan preliminär design finns, men det finns ingen standard att följa eller standardkomponenter som enkelt kan användas. Dessutom måste skalbarheten till det slutliga projektet redovisas i varje steg i projektet.Projektet är uppdelat i en preliminär dimensionering, följt av en Simulink-baserad simulering som testar preliminära beslut. Simuleringen, utförd på en omloppsbana påekliptikan, integrerar modeller av jordens skugga och störningar av vridmoment från ett antal källor.Flykttiden för ett 100m solsegel blir 1215 dagar, med en icke-linjär PD kontrollalgoritm och segelhörnsflöjlar som den enda styrhårdvaran. Dessutom studeras förskjutningen av tryckcentrum i förhållande till masscentrum under en förenklad modell av segeldeformation.

This master’s thesis is focused on the study of chemical and physical properties of dielectric materials with main focus on epoxy resins. It includes possible processes that can influence the properties of epoxy resins, both processes that improve polymer properties and processes that cause material degradation. Next part of the thesis is a description of diagnostic methods suitable for measurement of basic electrical quantities of material and design of a suitable method for measuring properties of epoxy resins with different additives, influencing the samples by solar radiation. At the end, the work includes an experiment dedicated to the degradation of epoxy resins with various additives by solar radiation and the evaluation of the experiment.

Das drahtlose Sensornetzwerk (WSN) ist eine Technologie, die Umgebungsbedingungen oder physikalische Parameter misst, weiterleitet und per Fernüberwachung zur Verfügung stellt. Normalerweise werden die Sensorknoten, die diese Netzwerke bilden, von Batterien gespeist. Diese sollen aus verschiedenen Gründen nicht mehr verwendet werden, sondern es wird auf eine eigenständige Stromversorgung gesetzt. Dies soll den aufwendigen Austausch und die Wartung minimieren. Energy Harvesting kann mit den Knoten verwendet werden, um die Batterien zu unterstützen und die Lebensdauer der Netzwerke zu verlängern. Aufgrund der hohen Leistungsdichte der Solarenergie im Vergleich zu verschiedenen anderen Umweltenergien sind Solarzellen die am häufigsten eingesetzten Wandler, allerdings stellt die schwankende und intermittierende Natur der Solarenergie eine Herausforderung dar, einen funktionalen und zuverlässigen Sensorknoten zu versorgen. Um den Sensorknoten effektiv zu betreiben, sollte sein Energieverbrauch sinnvoll gesteuert werden. Ein interessanter Ansatz zu diesem Zweck ist die Steuerung der Aktivitäten des Knotens in Abhängigkeit von der zukünftig verfügbaren Energie. Dies erfordert eine Vorhersage der wandelbaren Sonnenenergie für die kommenden Betriebszeiten einschließlich der freien Zeiten der Sonne. Einige Vorhersagealgorithmen wurden mit stochastischen und statistischen Prinzipien sowie mit Methoden der künstlichen Intelligenz (KI) erstellt. Durch diese Algorithmen bleibt ein erheblicher Vorhersagefehler von 5-70%, der den zuverlässigen Betrieb der Knoten beeinträchtigt. Beispielsweise verwenden die stochastischen Methoden einen diskreten Energiezustand, der meist nicht zu den tatsächlichen Messwerten passt. Die statistischen Methoden verwenden einen Gewichtungsfaktor für die zuvor registrierten Messwerte. Daher sind sie nur geeignet, um Energieprofile bei konstanten Wetterbedingungen vorherzusagen. KI-Methoden erfordern große Beobachtungen im Trainingsprozess, die den benötigten Speicherplatz erhöhen. Dementsprechend ist die Leistung hinsichtlich der Vorhersagegenauigkeit dieser Algorithmen nicht ausreichend. In dieser Arbeit wird ein Vorhersagealgorithmus mit einem neuronalen Netzwerk entwickelt und eingebunden in einen Mikrocontroller, um die Verwaltung des Energieverbrauchs von solarzellengesteuerten Sensorknoten zu optimieren. Das verwendete neuronale Netzwerk wurde mit einer Kombination aus meteorologischen und statistischen Eingangsparametern realisiert. Dies hat zum Ziel, die erforderlichen Designkriterien für Sensorknoten zu erfüllen und eine Leistung zu erreichen, die in ihrer Genauigkeit die Leistung der oben genannten traditionellen Algorithmen übersteigt. Die Vorhersagegenauigkeit die durch den Korrelationskoeffizienten repräsentiert wird, wurde für das entwickelte neuronale Netzwerk auf 0,992 bestimmt. Das genaueste traditionelle Netzwerk erreicht nur einen Wert von 0,963. Das entwickelte neuronale Netzwerk wurde in einen Prototyp eines Sensorknotens integriert, um die Betriebszustände oder -modi über einen Simulationszeitraum von einer Woche anzupassen. Während dieser Zeit hat der Sensorknoten 6 Stunden zusätzlich im Normalbetrieb gearbeitet. Dies trug dazu bei, eine effektive Nutzung der verfügbaren Energie um ca. 3,6% besser zu erfüllen als das genaueste traditionelle Netz. Dadurch wird eine längere Lebensdauer und Zuverlässigkeit des Sensorknotens erreicht. / Wireless Sensor Network (WSN) is a technology that measures an environmental or physical parameters in order to use them by decision makers with a possibility of remote monitoring. Normally, sensor nodes that compose these networks are powered by batteries which are no longer feasible, especially when they used as fixed and standalone power source. This is due to the costly replacement and maintenance. Ambient energy harvesting systems can be used with these nodes to support the batteries and to prolong the lifetime of these networks. Due to the high power density of solar energy in comparison with different environmental energies, solar cells are the most utilized harvesting systems. Although that, the fluctuating and intermittent nature of solar energy causes a real challenge against fulfilling a functional and reliable sensor node. In order to operate the sensor node effectively, its energy consumption should be well managed. One interesting approach for this purpose is to control the future node’s activities according to the prospective energy available. This requires performing a prior prediction of the harvestable solar energy for the upcoming operation periods including the sun’s free times. A few prediction algorithms have been created using stochastic and statistical principles as well as artificial intelligence (AI) methods. A considerable prediction error of 5-70% is realized by these algorithms affecting the reliable operation of the nodes. For example, the stochastic ones use a discrete energy states which are mostly do not fit the actual readings. The statistical methods use a weighting factors for the previous registered readings. Thus, they are convenient only to predict energy profiles under consistent weather conditions. AI methods require large observations to be used in the training process which increase the memory space needed. Accordingly, the performance concerning the prediction accuracy of these algorithms is not sufficient. In this thesis, a prediction algorithm using a neural network has been proposed and implemented in a microcontroller for managing energy consumption of solar cell driven sensor nodes. The utilized neural network has been developed using a combination of meteorological and statistical input parameters. This is to meet a required design criteria for the sensor nodes and to fulfill a performance exceeds in its accuracy the performance of aforementioned traditional algorithms. The prediction accuracy represented by the correlation coefficient has been registered for the developed neural network to be 0.992, which increases the most accurate traditional network which has a value 0.963. The developed neural network has been embedded into a sensor node prototype to adjust the operating states or modes over a simulation period of one week. During this period, the sensor node has worked 6 hours more towards normal operation mode. This in its role helped to fulfill an effective use of available energy approximately 3.6% better than the most accurate traditional network. Thus, longer lifetime and more reliable sensor node.

L'objectif de ce travail est d’évaluer le positionnement et le potentiel des récepteurs à lit fluidisé à changement de section par rapport aux autres méthodes de chauffage de gaz à haute température par voie solaire. A cette fin, une connaissance approfondie des phénomènes thermiques et hydrodynamiques du récepteur est nécessaire. Pour acquérir cette connaissance, nous avons modélisé les transferts thermiques dans le récepteur en portant une attention particulière sur les transferts radiatifs en prenant en compte les diffusions multiples de la lumière dans le milieu particulaire, les effets de parois sur les transferts radiatifs et la directionnalité du rayonnement solaire concentré. La détermination précise de la distribution de particules dans le ciel du lit fluidisé s'est avérée un paramètre critique pour le calcul des transferts thermiques. Ces modèles, plus tard affinés par une confrontation avec des références expérimentales, nous ont permis d'explorer l'effet de la géométrie sur les transferts thermiques dans le récepteur. Il ont permis entre autres de mettre en évidence l'intérêt d'utiliser une colonne de fluidisation à changement de section et l'importance de l'optimisation du couple concentrateur solaire / récepteur afin d'éviter d'éventuelles surchauffes au niveau des parois du récepteur. De même, il semble que l'homogénéisation de la température dans le lit fluidisé contenu dans le récepteur soit favorable à son rendement. / The aim of this work is to evaluate the position and the potential of solar fluidized bed receivers compared to other methods for the solar heating of gases at high temperature. To this end, a thorough knowledge of the heat transfer and hydrodynamic of the receiver is necessary. To acquire this knowledge, we modeled the heat transfer in the receiver with a focus on the radiative transfer by taking into account the multiple scattering of light in the particle medium, the effect of walls on radiative heat transfer and the directionality of the concentrated solar radiation. The accurate determination of the distribution of particles within the fluidized bed has been a critical parameter for the calculation of heat transfer. With these models, later refined by a confrontation with experimental references, we have studied the effect of geometry on heat transfer in the receiver. This study highlighted the necessity to use a switching section fluidization column and the importance to optimize the pair : solar concentrator / receiver to avoid any overheating at the walls of the receiver. Moreover, it appears that the homogenization of the temperature in the fluidized bed of the receiver increase its performance.

O objetivo principal deste trabalho foi desenvolver um equipamento capaz de expor as lentes de óculos de sol de maneira automática, de forma que simule o uso do acessório pelas pessoas, por um período equivalente ao tempo de uso de um mesmo modelo pela população brasileira e, através das medidas realizadas nas lentes após a exposição prolongada ao sol, verificar o comportamento da transmitância dos raios pela lente, principalmente dos raios UV, e assim, determinar se as lentes se degradam com o tempo. A partir dos resultados, espera-se complementar os estudos teóricos em desenvolvimento pelos pesquisadores do LIO sobre a equivalência entre os testes em simuladores solares e a exposição real ao sol, colaborando para a adequação dos parâmetros apresentados na norma nacional (NBR ISO 12312-1:2015) e internacional (ISO 12312-1:2013). Os parâmetros utilizados nos testes de certificação da norma nacional são os mesmos dos utilizados na internacional e que foram criados para representar as condições de radiação solar na Europa. Tendo conhecimento dos fatores que influenciam os níveis de radiação UV que atingem a Terra fica evidenciado que estes níveis são maiores nas regiões mais próximas do Brasil do que da Europa. Segundo estudos, uma otimização geográfica da norma brasileira deve ser considerada, levando-se em conta as diferenças nos índices UV do Brasil e da Europa. Além disso, os parâmetros para o teste de resistência à radiação em óculos de sol utilizados no Brasil, devem ser revistos para garantir que as condições simuladas sejam suficientes para garantir a proteção UV para as exposições típicas dos óculos ao Sol. A metodologia consistiu no desenvolvimento do protótipo para exposição automática de lentes de óculos de sol, além do desenvolvimento do sistema de medição do índice UV. Por fim, é descrito o teste realizado com uma miniatura de painel para exposição não controlada das lentes e a técnica e equipamentos utilizados para medição da transmitância luminosa e UV das lentes antes e depois da exposição ao Sol. Este protótipo consiste de uma caixa para proteção dos sistemas mecânicos e eletrônicos, uma tampa automática e um painel de acrílico, o qual acomoda 100 lentes posicionadas na posição de uso, as quais são irradiadas pelo Sol desde o nascer até o seu pôr. A tampa é aberta automaticamente, o painel ejetado, através do sistema mecânico, de dentro da caixa e rotaciona no sentido do Sol, de forma que as lentes sejam sempre irradiadas pela frente. A cada intervalo de 15 minutos, o sistema calcula a posição do Sol a ajusta a direção do painel. Sensores de variáveis climáticas avisam o sistema para fechar a tampa e proteger os óculos de condições indesejáveis. Os resultados deste trabalho consistam na apresentação do protótipo finalizado e funcionando, análise das informação obtidas dos sensores e análise preliminar sobre a variação da transmitância UV e luminosa das lentes de óculos de sol após 150 horas de exposição. É concluído que o período de 150 h não é suficiente para provocar mudanças significativas na características das lentes, portanto o protótipo do painel automatizado será utilizado para exposição a longo prazo e os resultados de pesquisas futuras poderão contribuir para as normas e melhor proteção da saúde ocular da população. / The aim of this work is to develop a device capable of exposing the lenses of sunglasses automatically, so that simulates the use of the accessory for people, for a period equivalent to the time of use of the same model by the Brazilian population and through measurements performed on the lenses after prolonged sun exposure, check the behavior of the transmittance of the rays by the lens, mainly from UV rays, and thus determine if the lenses degrade over time. From the results, it is expected to complement the theoretical studies being developed by LIO researchers on the equivalence in solar simulators tests and actual exposure to the sun, helping to adapt the parameters of the national standard (NBR ISO 12312-1:2015) and international (ISO 12312-1:2013). The parameters used in the certification tests of the national standard are the same as used in international and those were created to represent the solar radiation conditions in Europe. Knowing the factors that influence UV radiation levels reaching the earth is evident that these levels are higher in the nearby regions of Brazil than in Europe. According to studies, a geographical optimization of the Brazilian standard should be considered, taking into account differences in UV indices of Brazil and Europe. Also, the parameters for the radiation resistance test in sunglasses used in Brazil, should be reviewed to ensure that the simulated conditions are sufficient to ensure UV protection for typical exposures of glasses in the sun. The methodology is the development of the prototype for automatic exposure sunglass lenses, and the development of the UV index measuring system. Finally, it is described the test conducted with a miniature panel to expose lens and the technique and equipment used for measuring luminous and UV transmittance of the lenses before and after exposure to the sun. This prototype consists of a box for protection mechanical and electronic systems, automatic cover and an acrylic panel, which accommodates 100 lenses positioned in the use position, which will be irradiated by the sun from sunrise to sunset. The lid will automatically open the panel is ejected through the mechanical system out of the box, and must rotate in the direction of the sun, so that the lens is always irradiated from the front. Every 15-minute interval, the system calculates the position of the sun to set the direction of the panel. Climatic variables sensors alert the system to close the cover and protect the glasses undesirable conditions. The results of this project are to report the finished prototype and running, analysis of the obtained information from the sensors and preliminary analysis of the variation of UV transmittance and light lens sun glasses after 150 hours of exposure. It is concluded that the period of 150 hours is not sufficient to cause significant changes in the characteristics of the lenses, so the automated panel prototype will be used for long-term exposure and the results of future research will contribute to the standards and better protection of eye health of population.

O governo do Estado de São Paulo, na década de 60, realizou um programa de introdução de florestas do gênero Pinus para consolidar esta cultura no estado. Algumas destas florestas foram implantadas em áreas do Cerrado, que estavam degradadas devido à utilização para pastagens. Com a intenção de contribuir para um melhor entendimento das características hidrometeorológicas em uma floresta de P. elliotii, os objetivos desta pesquisa foram analisar a repartição da precipitação, o balanço de radiação acima do dossel, o perfil da temperatura do ar e comparar algumas características hidrometeorológicas desta floresta com as características em uma área aberta (gramado) e em uma área campestre de cerrado (pastagem). Na floresta foram instaladas estações meteorológicas automáticas no alto de uma torre e no interior. A repartição da precipitação resultou, pela medição manual, em uma precipitação interna de 75,2%, um escoamento pelo tronco de 0,5% e uma interceptação de 24,3% na floresta. Pela medição automática obteve-se uma precipitação interna de 78,7%. O albedo da floresta apresentou um valor médio de 12,8% e a radiação líquida variou de 6,0 MJm-2dia-1 a 14,2 MJm-2dia-1\'. A diferença da temperatura média do ar, no dossel e no interior da floresta, foi de 0,4ºC. Esta pesquisa apresenta uma grande contribuição para o cenário nacional na área de monitoramento hidrometeorológico de florestas. / The government of São Paulo State, Brazil, forty years ago, carried out a program of introduction of forest species with the main objective to consolidate the Pinus culture in the State. Some of these forests were implanted in areas of the Cerrado that were degraded due their use for grassland. The aim of the present work was to verify the hydrometeorologycal characteristics of Pinus elliottii forest, located in Cerrado, in the central region of São Paulo State, and to compare some characteristics among forest, grassland and lawn. In the forest were installed two automatic meteorological stations, one on the tower top and other inside of the forest. The partitionings of the precipitation by manual measurement were 75.2% for throughfall, 0.5% for stemflow and 24.3% for forest interception. By automatic measurement it was obtained 78.7% for throughfall. Forest\'s albedo presented an average value of 12.8% and net radiation ranged from 6.0 MJm-2day-1 to 14.2 MJm-2day-1. The diference of average air temperature between the canopy and the interior of the forest was 0.4ºC. This study presents a great contribuition to the national ambit of the hydrometeorologycal monitoring in forests.

Les variations du rayonnement solaire en surface (SSR) peuvent avoir un impact significatif sur divers aspects du système climatique, et notamment sur le développement socio-économique d’un pays. Pour identifier les impacts possibles du changement climatique sur le rayonnement solaire en surface à l'échelle régionale (~ 50 km) en Afrique australe jusqu'à la fin du 21ème siècle, on a analysé les données mensuelles produites dans le cadre du projet CORDEX-Afrique sur la période 1979-2099. Ces données sont issues des sorties de 5 modèles régionaux de climat (RCM) forcés par 10 modèles globaux de climat (GCM) CMIP5, pour deux scénarios d’émissions, RCP4.5 et RCP8.5, en Afrique australe (SA) et sur une partie du SWIO (0-40°S ; 0- 60°E). Pour contribuer au projet futur proposé qui vise à approfondir l'étude des changements de SSR à l'échelle locale (~ 1 km de résolution horizontale) à l'île de la Réunion et à l'île Maurice, situées dans le Sud-ouest de l'océan Indien (SWIO), près du bord d’Est du domaine CORDEX-Afrique, des simulations climatiques ont été réalisées sur trois fenêtres temporelles de 10 ans : a) le passé 1996-2005 ; et b) le futur 2046-2055 et 2090-2099, en utilisant la version 4 du RCM RegCM (RegCM4), forcé par : 1) les réanalyses climatiques ERA-Interim (ERAINT) du centre européen pour les prévisions météorologiques à moyen terme (ECMWF) pour simuler un passé récent seulement ; et 2) deux GCMs (HadGEM2-ES et GFDL-ESM2M) de l’exercice CMIP5 de simulations du climat passé et futur pour le scénario d’émissions RCP8.5 à l’échelle régionale de 50km en Afrique australe et dans le sud-ouest de l’océan Indien (0-40°S ; 0- 100°E). L’analyse de l’impact du changement climatique sur le SSR sur la base de ces simulations reste cependant limitée, à cause de leur couverture temporelle (3 périodes de 10 ans) et du nombre de modèles (2 GCMs, 1 RCM) et de scénarios (1 RCP) utilisés. Il ressort de l’analyse des simulations de l’ensemble CORDEX-Afrique que : 1) sur la période passée récente, les GCMs forceurs surestiment généralement SSR d'environ 1 W/m2 en été austral (DJF : Décembre-Janvier-Février), et de 7,5 W/m2 en hiver austral (JJA : Juin-Juillet-Août), tandis que les RCMs, forcés par ces GCMs, sous-estiment SSR d'environ -32 W/m2 et de -14 W/m2 en été et en hiver, respectivement. 2) Les projections multi-modèles de changement de SSR simulées par les RCMs et leurs GCMs forceurs sont assez cohérentes. Les GCMs prévoient, en moyenne multi-modèles, une augmentation statistiquement significative de SSR d'environ 8 W/m2 en 2099 selon le scénario RCP4.5 et de 12 W/m2 en 2099 selon le scénario RCP8.5 sur le Centre de l’Afrique australe (SA-C), et une diminution de SSR, avec un degré de confiance élevé, d'environ -5 W/m2 en 2099 selon le scénario RCP4.5 et de -10 W/m2 en 2099 selon le scénario RCP8.5, pendant la saison DJF, en Afrique équatoriale (EA-E). Dans ces deux régions, les RCMs produisent, en moyenne multi-modèles, des tendances similaires (avec un degré de confiance élevé) à celles des GCMs, mais sur des zones d’extension spatiale plus faible que celle des GCMs. Cependant, pour la saison JJA, une augmentation de SSR, d'amplitude similaire dans les simulations GCMs et RCMs (~5 W/m2 en 2099 selon le scénario RCP4.5 et 10 W/m2 selon le scénario RCP8.5), est attendue dans la région EA-E. 3). Une diminution significative de la nébulosité (environ -6% en 2099) est attendue sur le continent sud-africain pour les GCMs comme pour les RCMs. 4) Le scénario RCP8.5 produit des changements d’amplitude supérieure de 2.5W/m2 pour les GCMs forceurs et de 5W/m2 pour les RCMs en 2099 à celle pour le scénario RCP4.5. 5). Comme pour les sorties du modèle RegCM4, les structures des biais ou des changements de SSR issu des RCMs du programme CORDEX-Afrique sont globalement corrélées avec celles de couverture nuageuse totale des RCMs. L’analyse des sorties du modèle RegCM4 indique que : ..... / Changes in Surface Solar Radiation (SSR) have the potential to significantly impact diverse aspects of the climate system, and notably the socio-economic development of any nation. To identify the possible impacts of climate change on SSR at regional scales (~50 km) over Southern Africa and the South West Indian Ocean (SA-SWIO; 0-40°S ; 0- 100°E) up to the end of the 21st century, a slice downscaling experiment consisting of simulations covering three temporal windows: a) the present 1996-2005; b) the future 2046-2055 and 2090-2099 conducted with the Regional Climate Model (RCM) RegCM version 4, driven by the European Center for Medium-range Weather Forecasting (ECMWF) ERA-Interim reanalysis (ERAINT, only present) and 2 Global Climate Model (GCMs: HadGEM2-ES and GFDL-ESM2M) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) under RCP8.5 scenario, are performed and evaluated. Since the slice simulation is of limited temporal coverage, number of regional and driven global models and climate change forcings, mainly because of the limit of available computational resources, the study towards a comprehensive knowledge of SSR changes in context of climate change is thus extended: an ensemble consisting of outputs from 20 regional climate downscaling realisations based on 5 RCMs that participated in the Coordinated Regional Downscaling Experiment (CORDEX) program (CORDEX-Africa) along with their 10 driving GCMs from CMIP5 covering southern Africa (0-40°S; 0- 100°E) during the period of 1990-2099 is analyzed under RCP4.5 and RCP8.5 up to 2099.The slice experiment indicates that 1) RegCM4 simulates present-day seasonal climatology, (surface air temperature, precipitation and SSR) quite well, but has a negative total cloud cover bias (about -20% in absolute percentage) when forced by the ERAINT and the two GCMs. 2) Internal variability of RegCM4-simulated annual means SSR (about 0.2 W/m2) is of one order smaller than the model bias compared with reference data. 3) RegCM4 simulates SSR changes in opposite signs when driven by the different GCMs under RCP8.5 scenario. 4) Electricity potential calculated using first-order estimation based on the RegCM simulations indicates a change less then 2% to 2099 with respect on present level.It is also found from the ensemble study that: 1) GCMs ensemble generally overestimates SSR by about 1 W/m2 in austral summer (December, January, and February, short as DJF) and 7.5 W/m2 in austral winter (June, July and August, short as JJA), while RCMs ensemble mean shows underestimations of SSR by about -32 W/m2 and -14 W/m2 in summer and winter seasons respectively when driven by GCMs. 2) Multi-model mean projections of SSR change patterns simulated by the GCMs and their embedded RCMs are fairly consistent. 3) GCMs project, in their multi-model means, a statistically significant increase of SSR of about 8 W/m2 in RCP4.5 and 12 W/m2 in RCP8.5 by 2099 over Centre Southern Africa (SA-C) and a highly confident decreasing SSR over Eastern Equatorial Africa (EA-E) of about -5 W/m2 in RCP4.5 and -10 W/m2 in RCP8.5 during the DJF season. RCMs simulate SSR change with statistical confidence over SA-C and EA-E area as well with a little spatial extension compared to GCMs. However, in the JJA season, an increase of SSR is found over EA-E of about 5 W/m2 by 2099 under RCP4.5 and 10 W/m2 under RCP8.5, of similar amplitudes in both the GCMs and RCMs simulations. 4) Significant cloudiness decrease (about -6 % to 2099) is found over continent of SA for GCMs and also shown in RCMs. 5) Larger SSR changes are found in the RCP8.5 scenario than in the RCP4.5 scenario in 2099, with about 2.5 W/m2 enhanced changes in GCMs and about 5 W/m2 in RCMs. 6) Either the biases or the changes pattern of SSR are overall correlated with the patterns of total cloud cover from RCMs in CORDEX-Africa program (for RegCM4 as well). The slice experiment indicates that ...