LCA applicata alle tecnologie alimentate da energia solare: peculiarità e limiti metodologici

La Life Cycle Assessment (LCA) rappresenta una metodologia valida ed affidabile per la valutazione degli impatti energetico-ambientali connessi al ciclo di vita delle tecnologie alimentate da fonti rinnovabili di energia. Il lavoro di seguito presentato focalizza l’attenzione sui sistemi alimentati da energia solare. Gli autori, dopo un’analisi degli studi di letteratura inerenti la LCA applicata ai sistemi solari termici e fotovoltaici, descrivono le principali questioni metodologiche connesse alla valutazione delle prestazioni energetico-ambientali di tali tecnologie

TOWARD A SOLUTION OF ALLOCATION IN LIFE CYCLE INVENTORIES: THE USE OF LEAST SQUARES TECHNIQUES

Purpose: The matrix method for the solution of the so-called inventory problem in LCA generally determines the inventory vector related to a specific system of processes by solving a system of linear equations. The paper proposes a new approach to deal with systems characterized by a rectangular (and thus non-invertible) coefficients matrix. The approach, based on the application of regression techniques, allows solving the system without using computational expedients such as the allocation procedure. Methods: The regression techniques used in the paper are (besides the ordinary least squares, OLS) total least squares (TLS) and data least squares (DLS). In this paper, the authors present the application of TLS and DLS to a case study related to the production of bricks, showing the differences between the results accomplished by the traditional matrix approach and those obtained with these techniques. The system boundaries were chosen such that the resulting technology matrix was not too big and thus easy to display, but at the same time complex enough to provide a valid demonstrative example for analyzing the results of the application of the above-described techniques. Results and discussion: The results obtained for the case study taken into consideration showed an obvious but not overwhelming difference between the inventory vectors obtained by using the least-squares techniques and those obtained with the solutions based upon allocation. The inventory vectors obtained with the DLS and TLS techniques are closer to those obtained with the physical rather than with the economic allocation. However, this finding most probably cannot be generalized to every inventory problem. Conclusions: Since the solution of the inventory problem in life cycle inventory (LCI) is not a standard forecasting problem because the real solution (the real inventory vector related to the investigated functional unit) is unknown, we are not able to compute a proper performance indicator for the implemented algorithms. However, considering that the obtained least squares solutions are unique and their differences from the traditional solutions are not overwhelming, this methodology is worthy of further investigation. Recommendations: In order to make TLS and DLS techniques a valuable alternative to the traditional allocation procedures, there is a need to optimize them for the very particular systems that commonly occur in LCI, i.e., systems with sparse coefficients matrices and a vector of constants whose entries are almost always all null but one. This optimization is crucial for their applicability in the LCI contex

Life-cycle optimization of building performance: a collection of case studies

The building sector is one of the most impacting on the energy demand and on the environment in developed countries, together with industry and transports. The European Union introduced the topic of nearly zero-energy building (nZEB) and promoted a deep renovations in the existing building stock with the aim of reducing the energy consumption and environmental impacts of the building sector. The design of a nZEB, and in general of a low-energy building, involves different aspects like the economic cost, the comfort indoor, the energy consumption, the life cycle environmental impacts, the different points of view of policy makers, investors and inhabitants. Thus, the adoption of a multicriteria approach is often required in the design process to manage some potential conflicting domains. In detail, one of the most suitable approaches is to integrate the preliminary building design (or renovation) phase in a multi-objective optimization problem, allowing to rapidly compare many alternatives and to identify the most adapt interventions

ASSESSMENT OF ENERGY AND ECONOMIC EFFECTIVENESS OF PHOTOVOLTAIC SYSTEMS OPERATING IN A DENSE URBAN CONTEST

A methodology that permits to test the level of integration of the photovoltaic technology in urban areas is presented. The percentage of coverage of the electricity demand and the economic feasibility of grid-connected photovoltaic systems installed on the roofs of buildings were investigated in a district of the city of Palermo (Sicily). After classifying roofs according to their shape, orientation and pitch by means of satellite images provided by Google EarthTM, the ratio of the productivity of the PV systems and the consumption of electricity of the households was analysed considering all economic aspects. As a result, it can be always identified the number of floors in correspondence of which the size of the PV system that may be installed, and the consequent production of electricity, does not recover the costs for installation and maintenance of the system

ANALISI DELLA PRODUCIBILITA’ ENERGETICA DI IMPIANTI FOTOVOLTAICI IN CONTESTI URBANI

L’obiettivo del lavoro proposto è la definizione di una metodologia che consenta di testare il livello di integrazione della tecnologia fotovoltaica in contesti urbani ad alta densità edilizia. Il criterio adottato mira all’analisi contestuale dell’aspetto energetico, mediante valutazione della percentuale di copertura del fabbisogno di energia elettrica richiesto, e della convenienza economica degli impianti fotovoltaici installati sulle coperture degli edifici. A tal fine, per un quartiere della città di Palermo, sono state poste in relazione le superfici effettivamente disponibili all’installazione dei pannelli e il numero di utenze presenti. Le coperture, censite grazie all’ausilio delle immagini satellitari fornite da Google MapsTM e Google EarthTM, sono state classificate secondo la forma, l’orientamento e l’inclinazione. Esiste un numero di piani degli edifici per il quale la taglia dell’impianto a disposizione del singolo proprietario e la conseguente produzione di elettricità non riescono ad ammortizzare i costi per l’installazione e la manutenzione dell’impianto, anche alla luce dell’eventuale surplus di energia venduto alla rete e degli incentivi erogati dal Conto energia recentemente rinnovato. In ragione di ciò, è stato indagato il fattore della resa derivante dal confronto della produttività degli impianti installabili con i consumi di energia elettrica e ulteriormente approfondito alla luce degli aspetti di natura stringatamente finanziaria. Di questo parametro ne è stata esaminata anche la sua sensibilità alla variazione dei fattori che condizionano l’esito dell’analisi, quali il mismatch e l’ombreggiamento delle superfici

Life Cycle Assessment of electricity production from refuse derived fuel: A case study in Italy

Biomasses and bio-waste have an important role in decarbonizing the European energy mix, the latter contributing to the transition towards a circular economy. In particular, Refuse Derived Fuel (RFD) - a biofuel obtained from dry residue of waste – appears a really interesting energy option. In this framework this study aims at assessing the environmental profile of electricity generation from RDF in Italy, comparing two different kinds of RDF production and combustion plants. The functional unit is 1 kWh of net electricity from RDF delivered to the grid. Two Italian plants are examined: one located in Ravenna (RDF is produced in a direct flow treatment plant) and the other one in Bergamo (RDF is produced in a unique flow treatment plant and electricity is generated in a cogenerator). Results show that, comparing the plants, it is not possible to identify an option for RDF production or electricity generation characterized by lowest impacts for all the examined impact categories. However, cogeneration process and the avoided burdens due to the valorisation of ferrous metals and dry fractions during RDF production can reduce most of the environmental impacts. A dominance analysis reveals that chimney direct emissions generated during RDF combustion significantly contribute to some impact categories, as well as electricity consumption during RDF production. Furthermore, disposal of incineration wastes is a relevant contributor to human toxicity and freshwater eutrophication. The eco-profile of electricity from RDF is compared with electricity from the Italian grid and from multi-Si PV. The comparison highlights that electricity from RDF performs worse for relevant environmental impact categories such as climate change, human toxicity and photochemical oxidant formation. On the other hand, electricity from RDF performs better than electricity from the grid and from photovoltaic for resource depletion, an impact category of growing importance in the framework of circular economy

Assessment of Energy and Economic Effectiveness of Photovoltaic Systems Operating in a Dense Urban Context

A methodology that permits testing the level of integration of the photovoltaic technology in urban areas is presented. The percentage of coverage of the electricity demand of grid-connected photovoltaic systems installed on the roofs of buildings were investigated in a district of the city of Palermo (Sicily). After classifying roofs according to their shape, orientation and pitch by means of satellite images provided by Google Earth, the ratio of the productivity of the PV systems and the consumption of electricity of the households was analysed. The results of the energy assessment have been screened considering the economic feasibility of grid-connected photovoltaic systems: the energy produced by the PV systems whose economic analysis showed disadvantageous values of NPV or IRR was rejected. As a result, it can be concluded that the size of the PV system that may be installed corresponding to the number of floors, and the consequent production of electricity, does not recover the costs for installation and maintenance of the system

Construction of a webgis tool based on a gis semiautomated processing for the localization of p2g plants in sicily (Italy)

The recent diffusion of RES (Renewable Energy Sources), considering the electric energy produced by photovoltaic and wind plants, brought to light the problem of the unpredictable nature of wind and solar energy. P2G (Power to Gas) implementation seems to be the right solution, trans-forming curtailed energy in hydrogen. The choice of the settlement of P2G plants is linked to many factors like the distances between the gas grid and the settlement of RES plants, the transportation networks, the energy production, and population distribution. In light of this, the implementation of a Multi-Criteria Analysis (MCA) into a Geographic Information System (GIS) processing represents a good strategy to achieve the goal in a specific territorial asset. In this work, this method has been applied to the case of study of Sicily (Italy). The paper shows in detail the geomatic semi-automated processing that allows to find the set of possible solutions and further to choose the best localization for new P2G plants, connected to a Relational Database Management System (RDBMS) and integrated with a WebGIS visualization for real-time analysis. This system is useful for the management, the development, and the study of hydrogen technologies, in order to link the electri-cal network and the gas network datasets with economical and infrastructural assets through GIS processing. In the future new factors will join in the process as policies on hydrogen take shape

Assessment of Energy and Economic Effectiveness of Photovoltaic Systems Operating in a Dense Urban Context

A methodology that permits testing the level of integration of the photovoltaic technology in urban areas is presented. The percentage of coverage of the electricity demand of grid-connected photovoltaic systems installed on the roofs of buildings were investigated in a district of the city of Palermo (Sicily). After classifying roofs according to their shape, orientation and pitch by means of satellite images provided by Google Earth, the ratio of the productivity of the PV systems and the consumption of electricity of the households was analysed. The results of the energy assessment have been screened considering the economic feasibility of grid-connected photovoltaic systems: the energy produced by the PV systems whose economic analysis showed disadvantageous values of NPV or IRR was rejected. As a result, it can be concluded that the size of the PV system that may be installed corresponding to the number of floors, and the consequent production of electricity, does not recover the costs for installation and maintenance of the system

An innovative approach to manage uncertainties and stock diversity in the EPBD cost-optimal methodology

The EU Energy Performance of Buildings Directive (EPBD) 2010/31/EU is a step in the right direction to promote near zero energy buildings (NZEB) in a step-wise manner, starting with minimum energy performance and cost optimal thresholds for “reference buildings” (RBs) for each category. Nevertheless, a standard method for defining RBs does not exist, which led to a great divergence between MS in the level of detail used to define RBs for the EPBD cost-optimal analysis. Such lack of harmonisation between MS is further evident given the resulting large discrepancies in energy performance indicators even between countries having similar climate. Furthermore, discrepancies of 30% or higher between measured energy performance and that derived from the EPBD software induces uncertainty in the actual operational savings of measures leading to cost-optimality or NZEB in the simulated environment. This research proposes a robust and innovative framework to better handle uncertainties in the EPBD cost-optimal method both in the building software input parameters and in the global Life Cycle Costings (LCC), making the EPBD more useful for policy makers and ensuring a more harmonised approach among MS. The concept behind the proposed framework is the combination of a stochastic EPBD cost-optimal approach with Bayesian bottom-up calibrated stock-modelling. A new concept of “reference zoning” versus the “reference buildings” approach is also introduced in this research, which aims at providing a simpler and more flexible aggregation of energy performance for the more complex commercial building stock.peer-reviewe