Diagnosi Energetica dell’Azienda Ospedaliera “G.Brotzu”

Health care facilities, particularly hospitals, are known to be among the most energy intensive. The cause lies in the large amount of energy needed to cope with the demands of medical equipment and to provide the best quality of air conditioning. Therefore, energy efficiency measures could allow achieving important economic benefits and improving environmental impact of these types of facilities. The purpose of the research was the energy audit of the AOB (Azienda Ospedaliera Brotzu), the most important hospital in Sardinia (Italy). The work has been developed around the following topics: preliminary audit; thermal analysis via dynamic modeling; technical-economic feasibility analysis of the energy efficiency measures. Through the preliminary energy audit we aimed to achieve a realistic description, by the point of view of the energy, of the current status of the structure. The main objective of this phase was the identification of the characteristics of the building-plant system, its use, hence the definition of the energy balance of the hospital. Much time and efforts were required to gather all the information needed to determine the current status of the structure and its systems, particularly to the collection both of historical data of energy purchase (fuel and electricity) and the survey and validation of the hourly consumption recorded by the monitoring systems already present in the structure. Following this phase, that enabled us to provide an updated and realistic view of the energy behavior of the building-plant system, we drew up the AOB’s energy balance, considering the energy flows entering the plant, the historical analysis of consumption and their economic impact. Finally, through the reconstruction of the energy flows within the hospital and the performance evaluation of the systems, it was possible to determine the energy required by the users, and their hourly loads (Heating, Cooling, Domestic Hot Water, Electricity, etc.). The preliminary energy audit was integrated with the analysis and comparison of the AOB’s benchmark indicators with those of other hospitals in the national context. The second phase of the work involved the thermo physics analysis of the hospital via a virtual dynamic model implemented with the code TRNSYS-TRNBUILD. After the validation and the calibration of the code, we developed a virtual reproduction of the entire building that was used to perform several hourly simulations in dynamic conditions, aiming to study the thermal behavior of the structure depending on boundary conditions, such as weather, HVAC set-up, etc. With the virtual model it has been possible to achieve the following targets: verification of consumptions in compliance with applicable regulations; analysis and comparison between numerical results and data collected, with the aim of identifying the main causes of energy consumption and directing the selection of energy-saving strategies to be implemented; simulation of some energy efficiency measures by means of a numerical model more accurate and realistic of the common stationary codes. Starting from considerations arising from the preliminary audit and the dynamic simulations, in the third and final phase of the work we analyzed some energy-saving proposals that would allow achieving important economic benefits, improving at the same time the environmental sustainability of building-plant system. Aiming to ensure a better agreement with reality, the analysis of interventions were not carried out with numerical methods based on steady monthly calculation, but using more complex methods such as dynamic modeling (TRNSYS) or quasi-stationary codes which work on hourly loads. At first we contemplated the possibility of improving the performance of the building envelope by means of isolation of the facade, later we have examined the possible improvements by regarding the energy monitoring systems already installed in the hospital. Finally we carried out the technical and economic feasibility analysis on the possibility of using alternative systems for energy production, renewable energy technologies (solar thermal and photovoltaic), CHP (combined heat and power) and CCHP (combined cooling, heating and power) systems were examined. A multi scenario analysis was carried out to select the best technology possible in order to fulfill the energy demand of the AOB. The methodology and tools developed during the Ph.D. are not only applicable to the case under examination (AOB). The generality and flexibility of application allows the extension in several fields of application beyond health care facilities, such as civil, commercial and industrial buildings