| Popis: |
One of the primary European Union’s “Europe 2020” energy strategies is the reduction of the total energy consumption by means of energy efficiency improvements. In the European Union (EU) the building sector is responsible of about the 40% of the total final energy consumption and of the 36% of the Europe global CO2 emissions. During the last decade the European Commission released the first legislative instrument aimed to improve the energy performance of buildings: the “Energy Performance of Building Directive (EPBD) was introduced in 2002 and updated in 2010. The first edition of the document focused the analysis on new buildings, in order to promote the diffusion of energy efficient buildings, characterized by very low energy demand, possibly almost zero energy buildings. The recast of the document introduces the important topic of the existing building stock. It presents and discusses the recommendations that the European Commission released so far and focused on the possibilities of increasing the energy efficiency of buildings according to feasible retrofit strategies. The renovation of the existing building stock and the improvement of the energy performance are expected to have a key role in the increasing of European energy efficiency as well, considering that the 75% of the future stock has already been built. This thesis aims to investigate the possibilities of energy saving existing in the residential building sector. Some case studies will be presented with integrated HVAC systems based on different sources (multi-energy systems) combined to operate in the most suitable conditions to achieve higher efficiency performance as a whole. This type of system will be referred as IMES (Integrated Multi-Energy Systems). IMES performance will be evaluated according to new and retrofitted buildings, in order to investigate different plant configurations performances and to determine the extension of their applicability domain. The first chapter provides an overview of the European building stock, in order to comprehend the magnitude of the issue. The composition and the age of the existent buildings are analyzed as well as the actual energy consumption according to the final uses. Based on the described situation, the requirements introduced by the EPBD are analyzed according to new and existent buildings. The second chapter presents an analysis carried out to assess the effectiveness, in terms of reduction of primary energy demand, of the retrofit of the building envelope and of the HVAC system in a single dwelling house. The analysis has been realized by the means of dynamic simulations carried out by means of the commercial transient code TRNSYS. A model of the building and of the thermal system has been implemented according to the situation before the retrofit, and several redevelopment actions have been evaluated in order to achieve the maximum energy saving. The third chapter presents an activity which aimed to esteem the performance analysis of an IMES conceived to serve a multi-residential building. The main purposes are: to identify the configuration of the system that maximize the contribution of the renewable energy resources, i.e. solar energy and the renewable share due to the use of an heat pump; to set the mathematical model of the thermal storage by the means of experimental measurements, in order to better replicate the behaviors of real storages; to investigate the possibility of extending the applicability domain of the IMES to traditional buildings, equipped with non-insulated envelopes and radiators as emissions devices. The fourth chapter presents an analysis on the energy saving possibilities according to the retrofit of the European building stock. The work has considered the composition of the dwellings around Europe, identifying a general classification of the existent buildings. The analysis has been conducted on the basis of four case studies which have been subjected to an energy performance analysis, according to the status before and after a major renovation of the building envelope and of the HVAC system. The energy performance has been evaluated by means of dynamic simulations carried out with the commercial software TRNSYS. The work aims to evaluate the possible energy savings due to the renovation of the buildings into low energy buildings; to achieve this goal 20 simulation have been carried out on the buildings models, and 80 simulations have been necessary to conclude the analysis on the performance of the HVAC system. Four cities have been considered in the study to assess the effects of the redevelopment in different European climate conditions: Budapest, Venice, Athens and Helsinki |
