Second law analysis and simulation techniques for the energy optimization of buildings

The research activity described in this thesis is focused mainly on the study of finite-element techniques applied to thermo-fluid dynamic problems of plant components and on the study of dynamic simulation techniques applied to integrated building design in order to enhance the energy performance of the building. The first part of this doctorate thesis is a broad dissertation on second law analysis of thermodynamic processes with the purpose of including the issue of the energy efficiency of buildings within a wider cultural context which is usually not considered by professionals in the energy sector. In particular, the first chapter includes, a rigorous scheme for the deduction of the expressions for molar exergy and molar flow exergy of pure chemical fuels. The study shows that molar exergy and molar flow exergy coincide when the temperature and pressure of the fuel are equal to those of the environment in which the combustion reaction takes place. A simple method to determine the Gibbs free energy for non-standard values of the temperature and pressure of the environment is then clarified. For hydrogen, carbon dioxide, and several hydrocarbons, the dependence of the molar exergy on the temperature and relative humidity of the environment is reported, together with an evaluation of molar exergy and molar flow exergy when the temperature and pressure of the fuel are different from those of the environment. As an application of second law analysis, a comparison of the thermodynamic efficiency of a condensing boiler and of a heat pump is also reported. The second chapter presents a study of borehole heat exchangers, that is, a polyethylene piping network buried in the soil which allows a ground-coupled heat pump to exchange heat with the ground. After a brief overview of low-enthalpy geothermal plants, an apparatus designed and assembled by the author to carry out thermal response tests is presented. Data obtained by means of in situ thermal response tests are reported and evaluated by means of a finite-element simulation method, implemented through the software package COMSOL Multyphysics. The simulation method allows the determination of the precise value of the effective thermal properties of the ground and of the grout, which are essential for the design of borehole heat exchangers. In addition to the study of a single plant component, namely the borehole heat exchanger, in the third chapter is presented a thorough process for the plant design of a zero carbon building complex. The plant is composed of: 1) a ground-coupled heat pump system for space heating and cooling, with electricity supplied by photovoltaic solar collectors; 2) air dehumidifiers; 3) thermal solar collectors to match 70% of domestic hot water energy use, and a wood pellet boiler for the remaining domestic hot water energy use and for exceptional winter peaks. This chapter includes the design methodology adopted: 1) dynamic simulation of the building complex with the software package TRNSYS for evaluating the energy requirements of the building complex; 2) ground-coupled heat pumps modelled by means of TRNSYS; and 3) evaluation of the total length of the borehole heat exchanger by an iterative method developed by the author. An economic feasibility and an exergy analysis of the proposed plant, compared with two other plants, are reported. The exergy analysis was performed by considering the embodied energy of the components of each plant and the exergy loss during the functioning of the plants.

Stone architecture in Carso plateau. Settlement patterns and construction techniques of historic buildings

The use of stone and its types of processing have been very important in the vernacular architecture of the cross-border Carso. In Carso this represents an important legacy of centuries and has a uniform typological characteristic to a great extent. The stone was the main constituent of the local architecture, setting and shaping the human environment, incorporating the history of places through their specific symbolic and constructive language. The primary aim of this research is the recognition of the constructive rules and the values embedded in the Carso rural architecture by use and processing of stone. Central to this investigation is the typological reading, aimed to analyze the constructive language expressed by this legacy, through the analysis of the relationship between type, technique and material.

Performance Analysis and Improvements for the Future Aeronautical Mobile Airport Communications System (AeroMACS)

This thesis deals with the development of the upcoming aeronautical mobile airport communications system (AeroMACS) system. We analyzed the performance of AeroMACS and we investigated potential solutions for enhancing its performance. Since the most critical results correspond to the channel scenario having less diversity1, we tackled this problem investigating potential solutions for increasing the diversity of the system and therefore improving its performance. We accounted different forms of diversity as space diversity and time diversity. More specifically, space (antenna and cooperative) diversity and time diversity are analyzed as countermeasures for the harsh fading conditions that are typical of airport environments. Among the analyzed techniques, two novel concepts are introduced, namely unequal diversity coding and flexible packet level codes. The proposed techniques have been analyzed on a novel airport channel model, derived from a measurement campaign at the airport of Munich (Germany). The introduced techniques largely improve the performance of the conventional AeroMACS link; representing thus appealing solutions for the long term evolution of the system.

Ultra-Low Power and Non-intrusive Wireless Monitoring for Smart Buildings

Wireless Sensor Networks (WSNs) offer a new solution for distributed monitoring, processing and communication. First of all, the stringent energy constraints to which sensing nodes are typically subjected. WSNs are often battery powered and placed where it is not possible to recharge or replace batteries. Energy can be harvested from the external environment but it is a limited resource that must be used efficiently. Energy efficiency is a key requirement for a credible WSNs design. From the power source's perspective, aggressive energy management techniques remain the most effective way to prolong the lifetime of a WSN. A new adaptive algorithm will be presented, which minimizes the consumption of wireless sensor nodes in sleep mode, when the power source has to be regulated using DC-DC converters. Another important aspect addressed is the time synchronisation in WSNs. WSNs are used for real-world applications where physical time plays an important role. An innovative low-overhead synchronisation approach will be presented, based on a Temperature Compensation Algorithm (TCA). The last aspect addressed is related to self-powered WSNs with Energy Harvesting (EH) solutions. Wireless sensor nodes with EH require some form of energy storage, which enables systems to continue operating during periods of insufficient environmental energy. However, the size of the energy storage strongly restricts the use of WSNs with EH in real-world applications. A new approach will be presented, which enables computation to be sustained during intermittent power supply. The discussed approaches will be used for real-world WSN applications. The first presented scenario is related to the experience gathered during an European Project (3ENCULT Project), regarding the design and implementation of an innovative network for monitoring heritage buildings. The second scenario is related to the experience with Telecom Italia, regarding the design of smart energy meters for monitoring the usage of household's appliances.

Seismic fragility assessment of unreiforced masonry aggregate buildings

Aggregate masonry buildings have been generated over the years, allowing the interaction of different aggregated structural units under seismic action. The first part of this work is focused on the seismic vulnerability and fragility assessment of clay brick masonry buildings, sited in Bologna (Italy), with reference, at first, to single isolated structural units, by means of the Response Surface statistical method, taking into account some variabilities and uncertainties involved in the problem. The seismic action was defined by means of a group of selected registered accelerograms, in order to analyse the effect of the variability of the earthquakes. Identical and different structural units chosen by the Response Surface generated simulations are then aggregated in row, in order to compare the collapse PGA referred to the isolated structural unit and the one referred to the aggregate structure. The second part is focused on the seismic vulnerability and fragility assessment of stone masonry structures, sited in Seixal (Portugal), applying a methodology similar to that used for the buildings sited in Bologna. Since the availability of several information, the analyses involved the assessment of the most prevalent structural typologies in the area, considering the variability of a set of structural and geometrical parameters. The results highlighted the importance of the statistic procedures as method able to consider the variabilities and the uncertainties involved in the problem of the fragility of unreinforced masonry structures, in absence of accurate investigations on the structural typologies, as in the Seixal case study. Furthermore, it was showed that the structural units along the unreinforced clay brick or stone masonry aggregates cannot be analysed as isolated, as they are affected by the effect of the aggregation with adjacent structural units, according to the different directions of the seismic action considered and to their different position along the row aggregate.

How to cope with air transport disruptions: airport airside resilience and vulnerability

The efficiency of airport airside operations is often compromised by unplanned disruptive events of different kinds, such as bad weather, strikes or technical failures, which negatively influence the punctuality and regularity of operations, causing serious delays and unexpected congestion. They may provoke important impacts and economic losses on passengers, airlines and airport operators, and consequences may propagate in the air network throughout different airports. In order to identify strategies to cope with such events and minimize their impacts, it is crucial to understand how disruptive events affect airports’ performance. The research field related with the risk of severe air transport network disruptions and their impact on society is related to the concepts of vulnerability and resilience. The main objective of this project is to provide a framework that allows to evaluate performance losses and consequences due to unexpected disruptions affecting airport airside operations, supporting the development of a methodology for estimating vulnerability and resilience indicators for airport airside operations. The methodology proposed comprises three phases. In the first phase, airside operations are modelled in both the baseline and disrupted scenarios. The model includes all main airside processes and takes into consideration the uncertainties and dynamics of the system. In the second phase, the model is implemented by using a generic simulation software, AnyLogic. Vulnerability is evaluated by taking into consideration the costs related to flight delays, cancellations and diversions; resilience is determined as a function of the loss of capacity during the entire period of disruption. In the third phase, a Bayesian Network is built in which uncertain variables refer to airport characteristics and disruption type. The Bayesian Network expresses the conditional dependence among these variables and allows to predict the impacts of disruptions on an airside system, determining the elements which influence the system resilience the most.

On the use of the exoskeleton for seismic improvement and integrated efficient technologies in existing buildings

The aim of this work is to investigate the seismic improvement obtained through external strengthening structures applied on existing reinforced concrete buildings. An innovative integration with pre-assembled technological envelope components is also presented with the aim of achieving a holistic renovation. Particular attention was paid to the timber solution with an innovative post-tensioned connection between cross-laminated timber panels, which was the subject of an experimental campaign

Evaluation of seismic losses of RC buildings: the case of the industrial areas after the 2012 Emilia Earthquake

The topic of seismic loss assessment not only incorporates many aspects of the earthquake engineering, but also entails social factors, public policies and business interests. Because of its multidisciplinary character, this process may be complex to challenge, and sound discouraging to neophytes. In this context, there is an increasing need of deriving simplified methodologies to streamline the process and provide tools for decision-makers and practitioners. This dissertation investigates different possible applications both in the area of modelling of seismic losses, both in the analysis of observational seismic data. Regarding the first topic, the PRESSAFE-disp method is proposed for the fast evaluation of the fragility curves of precast reinforced-concrete (RC) structures. Hence, a direct application of the method to the productive area of San Felice is studied to assess the number of collapses under a specific seismic scenario. In particular, with reference to the 2012 events, two large-scale stochastic models are outlined. The outcomes of the framework are promising, in good agreement with the observed damage scenario. Furthermore, a simplified displacement-based methodology is outlined to estimate different loss performance metrics for the decision-making phase of the seismic retrofit of a single RC building. The aim is to evaluate the seismic performance of different retrofit options, for a comparative analysis of their effectiveness and the convenience. Finally, a contribution to the analysis of the observational data is presented in the last part of the dissertation. A specific database of losses of precast RC buildings damaged by the 2012 Earthquake is created. A statistical analysis is performed, allowing deriving several consequence functions. The outcomes presented may be implemented in probabilistic seismic risk assessments to forecast the losses at the large scale. Furthermore, these may be adopted to establish retrofit policies to prevent and reduce the consequences of future earthquakes in industrial areas.

Sustainability in buildings and waste sector: metrics, challanges, and opportunities

Nowadays, the scientific community has devoted a consistent effort to the sustainable development of the waste management sector and resource efficiency in building infrastructures. Waste is the fourth largest source sector of emissions and the municipal solid waste management system is considered as the most complex system to manage, due to its diverse composition and fragmentation of producers and responsibilities. Nevertheless, given the deep complexity that characterize the waste management sector, sustainability is still a challenging task. Interestingly, open issues arise when dealing with the sustainability of the waste sector. In this thesis, some recent advances in the waste management sector have been presented. Specifically, through the analysis of four author publications this thesis attempted to fill the gap in the following open issues: (i) the waste collection and generation of waste considering the pillars of sustainability; (ii) the environmental and social analysis in designing building infrastructures; (iv) the role of the waste collection in boosting sustainable systems of waste management; (v) the ergonomics impacts of waste collection. For this purpose, four author publications in international peer – reviewed journals were selected among the wholly author's contributions (i.e., final publication stage).

Study of low grade temperature CCHP systems for the realization of zero power buildings

Combined Cooling Heat and Power Generation (CCHP) or trigeneration has been considered worldwide as a suitable alternative to traditional energy systems in terms of significant energy saving and environmental conservation. The development and evaluation of a solar driven micro-CCHP system based on a ORC cogenerator and an Adsorption Chiller (AC) experimental prototypes has been the focus of this PhD research. The specific objectives of the overall project are: • To design, construct and evaluate an innovative Adsorption Chiller in order to improve the performances of the AC technology. • To thermodynamically model the proposed micro-scale solar driven CHP system and to prove that the concept of trigeneration through solar energy combined with an organic Rankine turbine cycle (ORC) and an adsorption chiller (AC) is suitable for residential applications.

Seismic vulnerability of buildings and non-structural elements: insights from the 2011 Lorca earthquake

This PhD dissertation presents a profound study of the vulnerability of buildings and non-structural elements stemming from the investigation of the Mw 5.2 Lorca 2011 earthquake; which constitutes one of the most significant earthquakes in Spain. It left nine fatalities due to falling debris from reinforced concrete buildings, 394 injured and material damage valued at 800 million euros. Within this framework, the most relevant initiatives concerning the vulnerability of buildings and the exposure of Lorca are studied. This work revealed two lines of research: the elaboration of a rational method to determine the adequacy of a specific fragility curve for the particular seismic risk study of a region; and the relevance of researching the seismic performance of non-structural elements. As a consequence, firstly, a method to assess and select fragility curves for seismic risk studies from the catalogue of those available in the literature is elaborated and calibrated by means of a case study. The said methodology is based on a multidimensional index and provides a ranking that classifies the curves in terms of adequacy. Its results for the case of Lorca led to the elaboration of new fragility curves for unreinforced masonry buildings. Moreover, a simplified method to account for the unpredictable directionality of the seism in the creation of fragility curves is contributed. Secondly, the characterisation of the seismic capacity and demand of the non-structural elements that caused most of the human losses is studied. Concerning the capacity, an analytical approach derived from theoretical considerations to characterise the complete out-of-plane seismic response curve of unreinforced masonry cantilever walls is provided; as well as a simplified and more practical trilinear version of it. Concerning the demand, several methods for characterising the Floor Response Spectra of reinforced concrete buildings are tested through case studies.