Solar energy indices in urban enviroment

D. Sotirxos, Solar energy indices in urban enviroment, Postgraduate Thesis, 70 pages, Athens, May 2010.



The first satellite images and space missions have made us realize that our planet, as a system, receives its exclusive inflow of energy from the sun. Undeniably, the solar radiation that reaches our planet’s surface prompts, either directly or indirectly, many natural and biological activities. We can characteristically mention wind movement, the water circle and the circles of other elements (e.g. the carbon circle), fossil fuels, food production for the living organisms through the photosynthesis process, etc. The knowledge of incoming solar radiation is a very useful piece of information to man, both for planning and accomplishing a number of activities. The following could be mentioned as such: applications in agriculture, in real estate, in building (for example, bioclimatic buildings, reservoirs), in sports activities (ski resorts etc) and in investments on the generation of energy (PV systems, boilers, etc). The plants, through the fundamental process of photosynthesis, are responsible for the conversion of solar energy into organic matter. However, intensive light conditions harm the plants, which adopt various strategies (e.g. resistivity) to ensure their survival. The lighting of a certain area can not, in itself, become a factor that defines plant biodiversity, as the minimum lighting levels are found in almost every part of the planet. The potential incoming solar radiation, which depends on the latitude, the day of year and the time of day, differs significantly from that which, in reality, reaches the surface, as location and climatic factors intervene and diminish it. With the help of Geographic Information Systems (GIS), we have created maps that provide information about the incoming solar radiation, with reference, however, to extended areas. This information can not be reliable in regions where the area topography presents great variations, as in urban environments. Undoubtedly, apartment buildings and other tall buildings cause intense shading in neighboring spots. The amount of radiation that these spots are submitted to is a fraction of the incoming radiation. Indeed, the measurements that were conducted on the spot that the present study discusses, as well as further calculations, showed that this spot is submitted to merely a 77% of the incoming radiation in a yearly basis.

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