The importance of reliable climatic data in the urban energy policy

In the last years, more and more attention has been focused on energy issues, in particular at urban level, as it is pointed out by the Directive 2002/91/EC on the Energy Performance of Buildings. In fact, the building sector encompasses nearly 30% of the energy whole consumptions. To try to limit such consumptions, both central and local governments should plan effective policies, such as promoting the use of renewable sources and of more energy efficient buildings (e.g. by means of green coverings). But in order to do that, local administrations should provide reliable tools for engineers and technicians to plan such systems. Nowadays, several software are available; the weak point is the availability of reliable climatic data and, above all, the ones referring to solar radiation. In this work, after a short overview of the world climatic databases, a description of three statistical methods for the elaboration of a climatic reduced set of data is reported. Then, referring to the climatic station of Palermo, Italy, we compare the results obtained evaluating the energy consumptions of a simple building and the energy produced by a photovoltaic (PV) system providing as input these different sets of data.