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

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

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

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

L'applicazione della Direttiva ErP presso le piccole e medie imprese: punti di forza e criticità

La Direttiva ErP sulla progettazione ecocompatibile dei prodotti connessi all’energia richiede che le imprese applichino dei criteri di eco-design orientati alla riduzione degli impatti energetico-ambientali lungo tutte le fasi del ciclo di vita dei loro prodotti. In tale contesto la Life Cycle Assessment (LCA) rappresenta uno strumento di fondamentale importanza per individuare le “key issues” energetico-ambientali connesse ai processi produttivi. L’articolo presenta i risultati di una LCA applicata ad una caldaia a biomassa prodotta in Sicilia, evidenziando i punti di forza e le criticità connessi all’attuazione della Direttiva da parte delle piccole e medie imprese

Life Cycle Environmental Assessment of Energy Valorization of the Residual Agro-Food Industry

This study assesses the potential environmental impacts related to the energy valorization of agro-food industry waste thought the Life Cycle Assessment methodology (ISO 14040). The system examined consists of a real anaerobic digester coupled with a combined anaerobic digester and heat and power plant (AD-CHP) operating in Sicily. The analysis accounts for all the impacts occurring from the delivery of the biomass to the AD-CHP plant up to the electricity generation in the CHP. The main outcomes of the study include the eco-profile of the energy system providing electricity and the assessment of the contribution of each life cycle phase aimed at identifying the potential improvement area. The obtained results highlight that the direct emissions associated with the biogas combustion process in the CHP account for 66% of the impact on climate change, and feedstock transport contributes 64% to the impact on mineral, fossil fuels, and renewable depletion. The contribution to the impacts caused by the electricity consumption is relevant in many of the environmental categories examined. It ranges from a minimum of about 22% for climate change up to 82% for freshwater ecotoxicity. Then actions aimed at reducing electricity consumption can significantly improve the environmental performances of the energy system examined