The Evaluation of the Energy Performances of a Net Zero Energy Building: an Italian Case Study

The emission saving related to the use of renewable energy sources: The case study of solar thermal collectors

The employment of renewable energy sources can represent a useful way to reduce air emissions released by conventional ones. In this paper we describe the results of a Life Cycle Analysis performed upon one of the most world-wide diffused renewable technologies: the solar thermal collectors for warm sanitary water. Two domestic solar plants have been investigated: mono-familiar plant with a passive flat collector and a large solar plant with forced fluid circulation. The first step has been the evaluation of direct and indirect emissions related to the production and use of plants. The main emissions have been categorised in three of the most important indicators (Global Warming Potential, …

MESSA A PUNTO DI UN SISTEMA SOLARE FOTOVOLTAICO-TERMICO PVT A BASSA CONCENTRAZIONE

Lo sfruttamento intensivo della risorsa solare può contribuire sensibilmente alla riduzione delle emissioni di gas clima alteranti. La crescita e la diffusione di impianti solari dipendono anche dalla capacità dell'industria di costruire e mettere in commercio collettori solari di nuova concezione ad alta efficienza energetica. Il presente lavoro descrive la realizzazione e la messa a punto di un circuito di prove sperimentali, presso il Dipartimento di Ricerche Energetiche ed Ambientali dell'Università di Palermo, relativo ad un impianto solare costituito da collettori solari parabolici lineari a debole concentrazione caratterizzati dal fatto di riunire in un’unica tecnologia chiamata CPVT…

Assessment of the Operating Temperature of Crystalline PV Modules Based on Real Use Conditions

Determining the operating temperatureTcof photovoltaic panelsPVis important in evaluating the actual performance of these systems. In the literature, different correlations exist, in either explicit or implicit forms, which often do not account for the electrical behaviour of panels; in this way, estimatingTcis based only on the passive behaviour of thePV. In this paper, the authors propose a new implicit correlation that takes into account the standard weather variables and the electricity production regimes of aPVpanel in terms of the proximity to the maximum power points. To validate its reliability, the new correlation was tested on two different PV panels (Sanyo and Kyocera panels) and…

To Assess the Validity of the Transfer Function Method: A Neural Model for the Optimal Choice of Conduction Transfer Functions

This paper presents a new mathematical approach applied to the Conduction Transfer Functions (CTFs) of a multilayered wall to predict the reliability of building simula- tions based upon them. Such a procedure can be used to develop a decision support system that identifies the best condition to calculate the best CTFs set. This is a critical point at the core of ASHRAE calculation methodology founded on the Transfer Function Method (TFM). To evaluate the perfor- mance of different CTFs sets, the authors built a large amount of data, subsequently employed to train a Neural Network Classifier (NNC) able to predict the reliability of a simulation without performing it. For this purpose all th…

Obtaining dynamic Norton parameters of a solar panel from manufacturer data

Photovoltaic arrays have been shown to possess significant influence on the dynamic performance of coupled source-converter-load system while its dynamic resistance is the most important parameter, contributing to the overall system dynamics. In this paper, a method of deriving the parameters of linearized photovoltaic equivalent circuit from manufacturer data is proposed. The approach allows predicting the range of dynamic Norton parameters for the expected irradiation and temperature operation conditions thus defining clear bounds required for robust design of the system controller.

Improvement of energy efficiency and quality of street lighting in South Italy as an action of Sustainable Energy Action Plans. The case study of Comiso (RG).

Existing street lighting systems in most of Sicilian cities are often inappropriate due to the obsolescence of light sources and luminaires and of unsuitable light control systems unable to provide efficient on-off and dimming strategies. Improvement of energy efficiency in street lighting systems can be one of the key actions adopted by Public Administration in developing Sustainable Energy Action Plan in the framework of the “Covenant of Majors” activities. As a task of FACTOR 20 project a set of planning options have been analysed and proposed for Sicilian cities. Particularly, street lighting efficiency projects have been studied for representative case studies. A detailed survey of the…

Artificial Neural Networks to Predict the Power Output of a PV Panel

The paper illustrates an adaptive approach based on different topologies of artificial neural networks (ANNs) for the power energy output forecasting of photovoltaic (PV) modules. The analysis of the PV module’s power output needed detailed local climate data, which was collected by a dedicated weather monitoring system. The Department of Energy, Information Engineering, and Mathematical Models of the University of Palermo (Italy) has built up a weather monitoring system that worked together with a data acquisition system. The power output forecast is obtained using three different types of ANNs: a one hidden layer Multilayer perceptron (MLP), a recursive neural network (RNN), and a gamma m…

Life cycle assessment of a solar thermal collector: sensitivity analysis, energy and environmental balances

Abstract Starting from the results of a life cycle assessment of solar thermal collector for sanitary warm water, an energy balance between the employed energy during the collector life cycle and the energy saved thanks to the collector use has been investigated. A sensitivity analysis for estimating the effects of the chosen methods and data on the outcome of the study was carried out. Uncertainties due to the eco-profile of input materials and the initial assumptions have been analysed. Since the study is concerned with a renewable energy system, attention has been focused on the energy indexes and in particular the “global energy consumption”. Following the principles of Kyoto Protocol, …

Studio finalizzato all’ottimizzazione degli impieghi delle risorse energetico-ambientali nel settore agroalimentare siciliano

L’influenza dei sistemi per il condizionamento dell’aria sul consumo di energia elettrica del settore residenziale: un modello neurale

A Finite Difference Model of a PV-PCM System

Abstract The performances of a photovoltaic panel (PV) are defined according to the “peak power” that identifies the maximum electric power supplied by the panel when it receives an insolation of 1 kW/m2 and the temperature of the cell is maintained at 25 °C. These conditions are only nominal since the solar radiation has a variable intensity and also the panel is subjected to thermal excursions; due to these reasons the real power efficiency of the panel is considerably lower than that obtainable in the nominal conditions. The study focused on assessing a method to reduce the peak temperatures of PV systems using Phase Change Materials (PCM). To this aim it was created a numerical model ca…

Valutazione energetica degli edifici – il bilancio energetico nel ciclo di vita

On the Efficacy of PCM to Shave Peak Temperature of Crystalline Photovoltaic Panels: An FDM Model and Field Validation

The exploitation of renewable energy sources and specifically photovoltaic (PV) devices have been showing significant growth; however, for a more effective development of this technology it is essential to have higher energy conversion performances. PV producers often declare a higher efficiency respect to real conditions and this deviation is mainly due to the difference between nominal and real temperature conditions of the PV. In order to improve the solar cell energy conversion efficiency many authors have proposed a methodology to keep the temperature of a PV system lower: a modified crystalline PV system built with a normal PV panel coupled with a Phase Change Material (PCM) heat stor…

LA SIMULAZIONE TERMICA DEGLI EDIFICI IN REGIME DINAMICO: UN CASO STUDIO PER LA VALIDAZIONE DEL SOFTWARE ESP-R

UN MODELLO ALLE DIFFERENZE FINITE DI UN PANNELLO FOTOVOLTAICO ACCOPPIATO A MATERIALE A CAMBIAMENTO DI FASE

La diffusione commerciale dei dispositivi fotovoltaici presenta negli ultimi anni un trend di crescita significativa a livello internazionale. Numerose ricerche sono state svolte al fine di incrementare l’efficienza di conversione elettrica dei pannelli fotovoltaici e tra le soluzioni indagate è stato sperimentato l’impiego di materiali a cambiamento di fase (MCF) per ridurre i picchi di temperatura di funzionamento. Nel lavoro è stato sviluppato un algoritmo di calcolo in grado di fornire l’andamento temporale della temperatura di un pannello fotovoltaico accoppiato a materiale a cambiamento di fase (Sistema PV-MCF). La determinazione della distribuzione di temperature che interessano un s…

Energy performances and life cycle assessment of an Italian wind farm

Abstract Renewable energy sources are often presented as “ clean ”. A more correct definition is that they are “cleaner” than ones based on fossil fuel conversion. When the energy consumption and the environmental impacts related to the plant's life-cycle are considered, a more comprehensive assessment of these technologies can be carried out. This paper aims to evaluate the energy and the environmental performances of the electricity production of a wind farm. The impacts related to all the phases of the wind farm construction and operation have been compared to the environmental benefits due to the “green” electricity generation during its useful life. In other terms, the goal is to trace…

A numerical solution that determines the temperature field inside phase change materials: application in buildings

The use of novel building materials that contain active thermal components would be a major advancement in achieving significant heating and cooling energy savings. In the last 40 years, Phase Change Materials or PCMs have been tested as thermal mass components in buildings, and most studies have found that PCMs enhance the building energy performance. The use of PCMs as an energy storage device is due to their relatively high fusion latent heat; during the melting and/or solidification phase, a PCM is capable of storing or releasing a large amount of energy. PCMs in a wall layer store solar energy during the warmer hours of the day and release it during the night, thereby decreasing and sh…

La certificazione energetica – Analisi della direttiva europea

The Evaluation of Energy Performances of a Net Zero Energy Building: An Italian Case Study

Over the past decades the impact of construction on the primary energy consumption and greenhouse gas emissions has highlighted [1]. The interest of the international scientific community has therefore focused on the concept of a Net Zero Energy Solar Building (NZESB), which is generally defined as a building that produces all primary energy it needs during a year [2]. Among the many research activities focused on these buildings, it should be mentioned the case study developed within the IEA SHC Task 40/ECBS Annex 52 "Towards Net Zero Energy Solar Buildings". The paper shows a case study of a Net Zero Energy Building (NZEB) located in Ancona (Italy):“Life Energy And Future (Leaf) House” (L…

Artificial neural network decision support tool for assessment of the energy performance and the refurbishment actions for the non-residential building stock in Southern Italy

The public buildings sector represents one of the most intensive items of EU energy consumption; the application of retrofit solutions in existing buildings is a crucial way to reduce its impact. To facilitate the knowledge of the energy performance of existing non-residential buildings and the choice of the more adequate actions, Public Administrations (PA) should have the availability of proper tools. Within the Italian project "POI 2007-13", a database and a decision support tool, for easy use, even to a non-technical user, have been developed. A large set of data, obtained from the energy audits of 151 existing public buildings located in four regions of South Italy have been analysed, …

Forecasting household electricity consumption with a neural network-based approach

Building energy certification in Italy

A novel implicit correlation for the operative temperature of a PV panel

Abstract The operating temperature of a commercial PV panel strongly affects the electric power output of the devices. The prediction of the operating temperature therefore plays a central role in the economic and energy assessment of PV systems. The authors propose a new implicit correlation that takes into account the standard weather variables but also the regimen of PV panel in terms of the proximity to the maximum power points. Data coming from an experimental setup were processed by using the least squares technique. To validate the reliability of the correlation, a comparison between expected values and data from other common correlations were done. The results show that the regimen …

Analisi energetico-ambientale di impianti ibridi di micro-cogenerazione a energia solare

Annual heating energy requirements of office buildings in a European climate

Abstract The concept of implementing energy savings to reduce greenhouse gas emissions has become a key element of energy policies of any industrialized country. In the civil sector and specifically, energy savings for office buildings, there are still opportunities for further enhancements related to correctly determining the air conditioning thermal requirements. However, there is a lack of simple correlations that allow a preliminary assessment for a single building or correlations that can be quickly applied at the district level. This paper proposes several simple correlations that determine the heating loads of a typical office building by only knowing the Degree-Days of a specific Eu…

Finite difference thermal model of a latent heat storage system coupled with a photovoltaic device: Description and experimental validation

Abstract The use of photovoltaic (PV) systems has been showing a significant growth trend but for a more effective development of this technology it is essential to have higher energy conversion performances. Producers of PV often declare an higher efficiency respect to real conditions and this deviation is mainly due to the difference between nominal and real temperature conditions of the PV. To improve the solar cell energy conversion efficiency many authors have proposed a methodology to keep lower the temperature of a PV system: a modified PV system built with a normal PV panel coupled with a Phase Change Material (PCM) heat storage device. In this paper is described a thermal model ana…

A Multifunctional Public Lighting Infrastructure, Design and Experimental Test

Nowadays, the installation of efficient lighting sources and Information and Communications Technologies can provide economic benefits, energy efficiency, and visual comfort requirements. More advantages can be derived if the public lighting infrastructure integrates a smart grid. This study presents an experimental multifunctional infrastructure for public lighting, installed in Palermo. The system is able to provide smart lighting functions (hotspot Wi-Fi, video-surveillances, car and pedestrian access control, car parking monitoring and support for environmental monitoring). A remote control and monitoring platform called “Centro Servizi” processes the information coming from…

Development of Neural Network Prediction Models for the Energy Producibility of a Parabolic Dish: A Comparison with the Analytical Approach

Solar energy is one of the most widely exploited renewable/sustainable resources for electricity generation, with photovoltaic and concentrating solar power technologies at the forefront of research. This study focuses on the development of a neural network prediction model aimed at assessing the energy producibility of dish–Stirling systems, testing the methodology and offering a useful tool to support the design and sizing phases of the system at different installation sites. Employing the open-source platform TensorFlow, two different classes of feedforward neural networks were developed and validated (multilayer perceptron and radial basis function). The absolute novelty of this approac…

Application of adaptive models for the determination of the thermal behaviour of a photovoltaic panel

The use of reliable forecasting models for the PV temperature is necessary for a more correct evaluation of energy and economic performances. Climatic conditions certainly have a remarkable influence on thermo-electric behaviour of the PV panel but the physical system is too complex for an analytical representation. A neural-network-based approach for solar panel temperature modelling is here presented. The models were trained using a set of data collected from a test facility. Simulation results of the trained neural networks are presented and compared with those obtained with an empirical correlation.

An efficient analytical approach for obtaining a five parameters model of photovoltaic modules using only reference data

Exploiting the equivalent one-diode circuit of a photovoltaic (PV) module, this paper proposes a novel and fully analytical model to predict the electrical performance upon solar irradiance intensity and PV module temperature. The model refers essentially to an equivalent circuit governed by five parameters and the extraction of them permits to describe the current–voltage curve of the PV panel and consequently permits to assess the energy output of PV modules. The proposed model extracts the five characteristic parameters using only exact analytical relationship and tabular data always available such as short-circuit current, open circuit voltage and the Maximum Power Point (MPP). The diff…

LIFE CYCLE ASSESSMENT-DRIVEN SELECTION OF INDUSTRIAL ECOLOGY STRATEGIES

The paper presents an application of the Life-Cycle Assessment (LCA) to the planning and environmental management of an ‘‘eco-industrial cluster.’’ A feasibility study of industrial symbiosis in southern Italy is carried out, where interlinked companies share subproducts and scraps, services, structures, and plants to reduce the related environmental impact. In particular, the research focuses on new recycling solutions to create open recycling loops in which plastic subproducts and scraps are transferred to external production systems. The main environmental benefits are the reduction of resource depletion, air emissions, and landfilled wastes. The proposed strategies are also economically…

Assessing the Energy-Saving Potential of a Dish-Stirling Concentrator Integrated into Energy Plants in the Tertiary Sector

Energy consumed for air conditioning in residential and tertiary sectors accounts for a large share of global use. To reduce the environmental impacts burdening the covering of such demands, the adoption of renewable energy technologies is increasing. In this regard, this paper evaluates the energy and environmental benefits achievable by integrating a dish-Stirling concentrator into energy systems used for meeting the air conditioning demand of an office building. Two typical reference energy plants are assumed: (i) a natural gas boiler for heating purposes and air-cooled chillers for the cooling periods, and (ii) a reversible heat pump for both heating and cooling. For both systems, a dis…

A Web-based Weather Monitoring Network in the city of Palermo

Monitoring Results and Energy Performances Evaluation of Freescoo Solar DEC Systems

Abstract This work addresses the energy saving performances of some solar Desiccant and Evaporative Cooling (DEC) systems working with the freescoo technology. The innovative freescoo concept is based on the use two fixed and cooled adsorption beds and advanced indirect evaporative cooling processes. The main feature of this new adsorption bed concept is to allow the simultaneous dehumidification and cooling of air. The systems analyzed have been installed in Italy last here and results based on field monitoring data are here presented. A description of the monitored systems and comparisons between the energy performances based on the main performance indicators such as EER, thermal COP, co…

The influence of air conditioning systems on the residential electricity consumptions: a neural network application

La Life Cycle Assessment come strumento di supporto per le piccole e medie imprese: un caso studio siciliano

L’Unione Europea mira ad orientare il mercato verso una crescente domanda di prodotti e servizi ecoefficienti ed eco-sostenibili. Le PMI, per essere competitive sul mercato, hanno la necessità di superare il gap tecnologico e di competenze che spesso le caratterizza ed avviare processi produttivi eco-orientati. In tale contesto nasce il Centro di Ricerca Italo-Maltese per la Sostenibilità Ambientale e le Fonti Rinnovabili (CRIM-SAFRI), che si propone di offrire una significativa opportunità di crescita e sviluppo per il tessuto produttivo dell’area del Mediterraneo, contribuire a ridurre i consumi energetici, le emissioni di gas serra e di altre sostanze inquinanti connessi ai processi prod…

A survey on energy performance of the non-residential public building stock in Southern Italy; toward a decision support tool for refurbishment actions

The public buildings sector represents one of the most intensive items of EU energy consumption; the application of retrofit solutions in existing buildings is a crucial way to reduce its impact. To facilitate the knowledge of the energy performance of the existing non-residential buildings and the choice of the more adequate actions, Public Administrations (PA) should have the availability of proper tools. Within the Italian project “POI 2007-13”, a database and a decision support tool, for easy use, even to a non-technical user, have been developed. A large set of data, obtained from the energy audits of 151 existing public buildings located in four regions of South of Italy have been ana…

Mini Wind Plant to Power Telecommunication Systems: A Case Study in Sicily

The ever increasing problems related to air pollution and the difficulties for power lines to reach inaccessible areas are pushing to find new solutions for powering telecommunications equipments (TLC). The renewable energy systems, although relatively expensive, have the required characteristics. The purpose of this work is to find a solution based on a low power wind turbine to serve a real telecommunication site located near Palermo, the main city of Sicily (Italy).

An improved five-parameter model for photovoltaic modules

This paper presents a new five-parameter model capable of analytically describing the I–V characteristic of a photovoltaic module for each generic condition of operative temperature and solar irradiance. The parameters of the equivalent electrical circuit are extracted by solving a system of equations based on data commonly issued by manufacturers in standard rating conditions with a trial and error process. The procedure, which does not require any special equations solver, can be easily coded into a short software routine using simple languages and finds the solution of the system of equations with the desired accuracy without needing to be guided towards solutions starting from fitted in…

Life cycle assessment of a solar thermal collector

Abstract The renewable energy sources are often presented as ‘clean’ sources, not considering the environmental impacts related to their manufacture. The production of the renewable plants, like every production process, entails a consumption of energy and raw materials as well as the release of pollutants. Furthermore, the impacts related to some life cycle phases (as maintenance or installation) are sometimes neglected or not adequately investigated. The energy and the environmental performances of one of the most common renewable technologies have been studied: the solar thermal collector for sanitary warm water demand. A life cycle assessment (LCA) has been performed following the inter…

An improved algorithm for thermal dynamic simulation of walls using Z-transform coefficients

The Transfer Function Method (TFM), recommended by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), is one of the most modern tools available to solve heat transfer problems in building envelopes and environments. TFM utilises Z-transform to solve the equations system that describes the heat transfer in a multi-layered wall. Due to an analogy with an electric circuit, it is possible to write the equations system in a matrix suitable to be solved by computer. Authors carried out an analysis on an historical building placed in the south of Italy to test the reliability and the quality of the thermal dynamic simulation using TFM. The analysis is performed usi…

Numerical Assessment of Heating Energy Demand for Office Buildings in Italy

Abstract Buildings energy consumption depends on several parameters, such as climate, envelope typologies, occupant behavior, intended use, etc.; assessment of the energy performance of a building requires substantial input data describing constructions, environmental contexts, thermo-physical properties, geometry, control strategies and several other parameters influencing the thermal balance. In the last years, several numerical approaches dedicated to building simulation have been tested developing specialized software. On the other hand, simplified building models permit the evaluation of indoor conditions and heating/cooling loads with a good level of accuracy and without excessive com…

Life cycle assessment of a solar PV/T concentrator system

The paper shows the energy and environmental analysis of a solar low Concentrating Photovoltaic-Thermal (CPVT) system, installed on the roof of the Energy Department building at University of Palermo (Italy). LCA methodology was applied to assess the whole life-cycle of the selected Functional Unit. Data survey from the producing company regarding the consumption of energy sources and of materials were developed. The assessment allowed to identify the steps and the system components addressing the highest energy and environmental impacts. Energy and environmental benefits and drawbacks related to the CPVT system. The research was developed within the National Relevant Research Programme (PR…

Uno strumento di supporto alla decisione nel campo dei software per la simulazione termica degli edifici in regime vario

Analisi della correlazione clima consumi elettrici tramite rete neurale artificiale

MIGLIORAMENTO DELLA RESA ENERGETICA DI UN PANNELLO FOTOVOLTAICO PER MEZZO DI MATERIALE A CAMBIAMENTO DI FASE

Energy and economic assessment of a small domestic wind turbine in Palermo

The cost effectiveness of micro-wind technology is closely linked to the annual energy production plants, which strongly depends on the wind characteristics and on the morphological properties of the installation site. The power curve of a wind turbine, supplied by manufacturers, characterizes the theoretical energy performance that it should have at a particular site. The behavior of a wind turbine in the field is affected by the speed but also by wind direction variations. At each change of direction and speed, the turbine will try to adapt to new conditions and the phase transition negatively influences the energy production. In order to experimentally confirm what above mentioned, the a…

Is the transfer function method reliable in a European building context? A theoretical analysis and a case study in the South of Italy

Abstract The available tools for dynamic simulation of the buildings thermal behaviour are manifold, and the most modern ones, known as TRNSYS, are founded upon the use of the Z-transform (ZT) set also called transfer function method (TFM). The transfer function method (TFM), recommended by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), is one of the most modern tools available to solve heat transfer problems in building envelopes and environments. TFM utilises Z-transforms to solve the equation system that describes the heat transfer in a multi-layered wall. Due to an analogy with an electric circuit, it is possible to write the equation system in a mat…

Short term wind speed prediction using Multi Layer Perceptron

Among renewable energy sources wind energy is having an increasing influence on the supply of energy power. However wind energy is not a stationary power, depending on the fluctuations of the wind, so that is necessary to cope with these fluctuations that may cause problems the electricity grid stability. The ability to predict short-term wind speed and consequent production patterns becomes critical for the all the operators of wind energy. This paper studies several configurations of Artificial Neural Networks (ANN), a well-known tool able to estimate wind speed starting from measured data. The presented ANNs, t have been tested through data gathered in the area of Trapani (Sicily). Diffe…

A neural classifier for the optimal selection of conduction transfer functions

Sistema di rilevazione e pubblicazione dati meteo per la città di Palermo.

VALIDAZIONE SPERIMENTALE DI UN MODELLO DI SIMULAZIONE DEL COMPORTAMENTO TERMICO ED ELETTRICO DI PANNELLI FOTOVOLTAICI PIANI

A web-based autonomous weather monitoring system of the town of Palermo and its utilization for temperature nowcasting

Weather data are crucial to correctly design buildings and their heating and cooling systems and to assess their energy performances. In the intensely urbanized towns the effect of climatic parameters is further emphasized by the "urban heat island" phenomenon, known as the increase in the air temperature of urban areas, compared to the conditions measured in the extra-urban areas. The analysis of the heat island needs detailed local climate data which can be collected only by a dedicated weather monitoring system. The Department of Energy and Environmental Researches of the University of Palermo has built up a weather monitoring system that works 24 hours per day and makes data available i…

A dish-stirling solar concentrator coupled to a seasonal thermal energy storage system in the southern mediterranean basin: A cogenerative layout hypothesis

Abstract In the future, renewable energy sources will increasingly represent an efficient energy source capable of meeting the demands of residential and industrial buildings avoiding the emissions of greenhouse gases into the atmosphere. In this paper, a heat and electric power cogeneration plant implementing a field of dish-Stirling collectors, a seasonal geothermal storage and a system of water-to-water heat pumps is proposed for the first time. The cogeneration plant has been designed both to supply thermal energy to the heating system of Building 9 of the Department of Engineering in Palermo and to produce electricity. The operation of the plant has been tested by means of hourly-based…

Mini Wind Plant to Power Telecommunication Systems: a Case Study in Sicily

The ever increasing problems related to air pollution and the difficulties for power lines to reach inaccessible areas are pushing to find new solutions for powering telecommunications equipments (TLC). The renewable energy systems, although relatively expensive, have the required characteristics. The purpose of this work is to find a solution based on a low power wind turbine to serve a real telecommunication site located near Palermo, the main city of Sicily (Italy).

On the experimental validation of an improved five-parameter model for silicon photovoltaic modules

Abstract This paper presents the experimental validation of a new five-parameter model capable of analytically describing the I–V characteristic of a silicon photovoltaic module for each generic condition of operative temperature and solar irradiance. The operating current calculated with the model was validated on the basis of a series of experimental measurements performed in the field on two commercial silicon photovoltaic panels connected to a set of nine constant values of the electrical load. In order to examine the panels working in almost steady-state conditions only the data-sets of the sunniest days from sunrise to sunset were used. Unfortunately the production spread of photovolt…

Valutazione mediante tecnica fotografica dell'oscuramento della radiazione solare dovuto alle ostruzioni

Si propone un nuovo metodo che consente di utilizzare l’immagine fotografica di ostacoli ombreggianti per valutarne l’effetto oscurante nei confronti della radiazione solare diretta incidente su di una superficie. Il metodo proposto è simile a quello che prevede l’impiego del diagramma cilindrico dei percorsi solari, calcolati in funzione dell’azimuth e dell’altezza solare, e la sovrapposizione su di esso del poligono raffigurante l’oggetto ostruente costruito in base alle coordinate cilindriche dei suoi punti più significativi. La nuova procedura prevede invece la sovrapposizione sulla fotografia del percorso solare opportunamente trasformato secondo le regole della prospettiva. E’ così po…

A criterion for the assessment of the reliability of ASHRAE conduction transfer function coefficients

This paper presents a new mathematical approach, which, when applied to conduction transfer functions (CTFs) of a multi-layered wall, is able to predict the reliability of building simulations. This new procedure can be used to identify the best set of CTF coefficients, which are a critical point at the core of the ASHRAE calculation methodology founded on the transfer function method. To evaluate the performance of different CTF coefficient sets, the authors performed a large number of thermal simulations on the multi-layered walls included in the ASHRAE Handbook, volume fundamentals, and on other walls typical of Mediterranean building heritage. Those data were employed to test an algorit…

Environmental and energy performances of a newly installed Dish-Stirling Concentrating Solar Power plant based in Palermo

n the last decade there has been a significant increase globally in solar based electricity production, like those produced from Concentrating Solar Power (CSP) plants. One of the most efficient CSP technologies today is the Dish-Stirling characterized by an efficiency greater than 30%, which may become highly competitive by 2030 according to the International Energy Agency. On one hand, the Dish-Stirling is responsible for high environmental impacts, caused during its production and installation due to their energy consumption and use of energy intensive raw material. On the other hand, no direct emissions are released during its use phase. However, only a careful analysis of the entire li…

Electrochemical energy storage mitigating impact of electric vehicle on the electric grid: Two Italian case studies

In the framework of the Italian R&D project i-Next two pilots plants were realized aiming at demonstrate benefits coming from the adoption of electrochemical energy storages (Lithium ion batteries and hydrogen) integrated with renewable energy sources. In the present study the preliminary results coming from the demo sites operations are reported paying attention to the impacts to the grid.

Numerical assessment of heating energy demand for office buildings in Italy

Buildings energy consumption depends on several parameters, such as climate, envelope typologies, occupant behavior, intended use, etc.; assessment of the energy performance of a building requires substantial input data describing constructions, environmental contexts, thermo-physical properties, geometry, control strategies and several other parameters influencing the thermal balance. In the last years, several numerical approaches dedicated to building simulation have been tested developing specialized software. On the other hand, simplified building models permit the evaluation of indoor conditions and heating/cooling loads with a good level of accuracy and without excessive computationa…

Single thermal zone balance solved by Transfer Function Method

We present an algorithm that uses the Z-transform operator to face the problem of heat transmission in a single thermal zone composed by multilayered walls. The method is very flexible and could be adopted to calculate the transfer function coefficients able to simulate the thermal behaviour of a room in free floating. Knowing the transfer function coefficients, it is possible to simulate the dynamic profile of each inner surfaces temperature and furthermore of the inner air temperature. The proposed algorithm is fully described granting maximum clarity. The explicitness of all steps of the calculus make possible the definition of a method that is able to vary all of the calculus parameters…

An Approach to Rank Noise Pollution in Workplaces

In this paper, we describe a method for classifying the workplaces as regards the noise risk. This method provides an univocal classification of work area and allows to correctly implement the control measures in accordance with a suitable priority scale. Finally, this method can be easily adjusted to respect various national standards.

Calculation of Energy Performance Indices of Daylight Linked Control Systems by Monitored Data

The actual performances of Building Automation systems are often lower than the ideal ones. In order to investigate the actual performance of a Building Automation system for lighting control, a large stock of collected data, including indoor illuminance and absorbed electric power, have been presented and analysed in this paper. The measures have been taken during one year, in a laboratory located at the University of Palermo, where different lighting control systems, produced by two different manufacture companies, have been installed. As demonstrated in literature, many factors affecting energy savings’ evaluation in lighting control systems are the position and the typology of the senso…

A comparison of different one-diode models for the representation of I–V characteristic of a PV cell

Predictive performance tools are an important factor in the success of any new technology because they permit demonstration of whether a system will be efficient and economically feasible. A reliable predictive tool should allow the designer to optimise system performance and to maximise the cost effectiveness of a system prior to installation. This article discusses the five main parametric models for photovoltaic (PV) systems available in the literature. The current–voltage characteristics of a photovoltaic module can be reproduced modelling the PV panel as an equivalent electrical circuit made of linear and non-linear components. The parameters describing such components are directly rel…

Energy and Environmental Assessment of a Hybrid Dish-Stirling Concentrating Solar Power Plant

Although the 2019 global pandemic slowed the growing trend of CO2 concentrations in the atmosphere, it has since resumed its rise, prompting world leaders to accelerate the generation of electricity from renewable sources. The study presented in this paper is focused on the evaluation of the energy and environmental benefits corresponding to the hypothesis of hybridizing a dish-Stirling plant installed on the university campus of Palermo (Italy). These analyses were carried out by means of dynamic simulations based on an accurate energy model validated with the experimental data collected during the measurement campaign that occurred during the period of operation of the reference plant. As…

A validated energy model of a solar dish-Stirling system considering the cleanliness of mirrors

Solar systems based on the coupling of parabolic concentrating collectors and thermal engines (i.e. dish-Stirling systems) are among the most efficient generators of solar power currently available. This study focuses on the modelling of functioning data from a 32 kWe dish-Stirling solar plant installed at a facility test site on the University of Palermo campus, in Southern Italy. The proposed model, based on real monitored data, the energy balance of the collector and the partial load efficiency of the Stirling engine, can be used easily to simulate the annual energy production of such systems, making use of the solar radiation database, with the aim of encouraging a greater commercialisa…

Improvement of energy efficiency and quality of street lighting in South Italy as an action of Sustainable Energy Action Plans. The case study of Comiso (RG)

Abstract Existing street lighting systems, in most of South Italy cities, are often inefficient due to the obsolescence of lamps and luminaires and of ineffective light control systems unable to implement efficient on-off and dimming strategies. Energy efficiency improvement, in street lighting systems, is often one of the key actions to be adopted by Public Administration in their Sustainable Energy Action Plan in the framework of the “Covenant of Majors” activities. As a task of FACTOR 20 project, a set of planning options has been analysed and proposed. Particularly, street lighting efficiency projects have been studied for representative case studies. A detailed survey of the public lig…

Modelling relationship among energy demand, climate and office building features: A cluster analysis at European level

Abstract More than one-third of the energy demand of industrialised countries is due to achieving acceptable conditions of thermal comfort and lighting in buildings. Energy demand in buildings depends on a combination of several parameters, such as climate, envelope typologies, occupant behaviour, and intended use. Indeed, assessing a building’s energy performance requires substantial input data describing constructions, environmental conditions, envelope thermo-physical properties, geometry, control strategies, and several other parameters. This has been a very active area of research in recent years, and several numerical approaches have been developed for building simulation; furthermore…

Quality of wind speed fitting distributions for the urban area of Palermo, Italy

Abstract This study investigates the wind speed characteristics recorded in the urban area of Palermo, in the south of Italy, by a monitoring network composed by four weather stations. This article has two main objectives: the first one, to describe with clarity and simplicity the numerical procedures adopted to perform a preliminary statistical analysis of wind speed data, providing at the same time, the necessary mathematical tools useful to perform this analysis also without special software. The second objective is to verify if there are more suitable probability distributions able to better represent the original data respect the traditional ones. After a preliminary statistical analys…

A decision support system to compare different strategies for achieving the Italian Kyoto Protocol commitment

Abstract: In order to meet the Italian Kyoto Protocol commitment, in 2002 the Interministerial Committee for Economic Planning (CIPE) approved the national allocation plan for the reduction of Greenhouse Gases (GHGs), envisioning various alternative scenarios. In this paper an extended impact assessment of the plan is accomplished and some further options are conceived and analysed in order to find an optimal trade-off among the different economic, environmental and social items at stake. After the selection of a set of independent indicators, nine different scenarios for the GHG reductions were evaluated and they were sorted according to the principles of the multicriteria analysis. The re…

Degree Days and Building Energy Demand

Degree-days (DD) are a climatic indicator that can be used in the assessment and analysis of weather related to energy consumption of buildings. Essentially, degree-days are a summation of the differences between the outdoor temperature and some reference (or base) temperature over a specific time period. In literature, different method can be used for determining the DD value and generally the choice depends on the availability of climatic data of each location. In this paper, after a review and comparison of the most common approaches used to determine DD, the Italian procedure was deeply analyzed. The application of Italian technical rules is based on weather data calculated on a monthly…

The new building regulation plan schema in the town of Castelbuono (Sicily): the experience of FACTOR20- LIFE+ project

The LIFE+ Programme is the European Union’s funding instrument for the environment. The general objective of LIFE+ is to contribute to the implementation, updating and development of EU environmental policy and legislation by co-financing pilot or demonstration projects with European added value. In the framework of LIFE+, the project “Forwarding demonstrative ACTions On a Regional and local scale (FACTOR20) to reach EU targets of the European Plan 20/20/20” was founded by European Commission. FACTOR20 is aimed to define a set of tools to support the planning of regional and national policies for the reduction of greenhouse gas emissions and for the reduction of energy consumption. The know…

Improving the thermal performance of the transparent building envelope: finite element analysis of possible techniques to reduce the U-value of the glassblocks

U-value of glazed elements is often a critical issue because these components, due to their small thickness and to the poor resistance of the glass and frame materials, cause very relevant heat fluxes. This paper presents an investigation on the thermal properties of a particular glazed component: the glassblock. Generally standard glassblocks have high U- values in comparison to the maximum values allowed by energy efficiency standards for glazed surfaces. This paper reports a summary of possible solutions that could improve the performances of the glassblock. A set of new configurations of the glassblock has been defined by schematic models and their overall thermal resistance has been as…

Multidiscipline LCA application to an experience of industrial symbiosis in South of Italy

The paper presents an application of the Life-Cycle Assessment (LCA) to the planning and environmental management of an “eco-industrial cluster.” A feasibility study of industrial symbiosis in southern Italy is carried out, where interlinked companies share subproducts and scraps, services, structures, and plants to reduce the related environmental impact. In particular, the research focuses on new recycling solutions to create open recycling loops in which plastic subproducts and scraps are transferred to external production systems. The main environmental benefits are the reduction of resource depletion, air emissions, and landfilled wastes. The proposed strategies are also economically v…

Analisi del regime anemometrico a scala urbana della città di Palermo

Allo scopo di valutare la possibilità di sfruttare l’energia eolica anche in zone fortemente urbanizzate recentemente la Comunità Europea ha posto tra le sue priorità scientifiche la redazione di atlanti eolici a piccola scala. Al fine di fornire dati che possano condurre ad una corretta valutazione eolica di centri urbani, nel seguente lavoro vengono analizzate le caratteristiche del regime anemometrico dell'area urbana di Palermo, registrate da un rete di monitoraggio automatica afferente al Dipartimento di Ricerche Energetiche ed Ambientali (DREAM) e composta da quattro stazioni meteo. Dopo un esame statistico preliminare, in cui le serie temporali della velocità del vento sono state div…

EDIFICI AD ENERGIA NETTA ZERO: UN CASO STUDIO ITALIANO

L’industria, il sistema dei trasporti e l’edilizia sono i tre principali macro settori economici che più determinano un consumo di energia: In Italia, in particolare, ben il 30% dell’energia elettrica e il 40% di quella termica vengono impiegate nel settore civile d’utenza [1]. La necessità di ridurre i consumi energetici, determinata da sempre più restrittivi vincoli di natura ambientale e dal crescente costo dell’energia, gioca un ruolo importante nel modificare i canoni di progettazione e le modalità di manutenzione energetica degli edifici. Da ciò discende anche la crescente attenzione della comunità scientifica internazionale verso il concetto di Edificio ad Energia Netta Zero (EENZ), …

A NEW FIVE-PARAMETER MODEL FOR PHOTOVOLTAIC PANELS- DETERMINATION OF COMMERCIAL MODULES I-V CHARACTERISTICS

Il metodo delle funzioni di trasferimento applicato ad un singola zona termica

Nel lavoro viene presentato un algoritmo basato sull’utilizzo dell’operatore Z-Trasformata per lo studio della trasmissione del calore all’interno di una singola zona termica costituita da pareti multistrato. L’algoritmo utilizzato è molto versatile e potrebbe venire utilizzato per il calcolo dei coefficienti delle funzioni di trasferimento nella simulazione del comportamento termico di un ambiente in free floating. Noti i coefficienti delle funzioni di trasferimento è possibile simulare in regime dinamico il profilo della temperatura di ciascuna superficie interna e dell’aria interna all’ambiente analizzato. L’algoritmo viene descritto in maniera completa in tutte le sue parti. Per valutar…

Nonlinear black-box models for short-term forecasting of air temperature in the town of Palermo

Weather data are crucial to correctly design buildings and their heating and cooling systems and to assess their energy performances. In the intensely urbanized towns the effect of climatic parameters is further emphasized by the Urban Heat Island (UHI) phenomenon, known as the increase in the air temperature of urban areas, compared to the one measured in the extra-urban areas. The analysis of the heat island needs detailed local climate data which can be collected only by a dedicated weather monitoring system. The Department of Energy and Environmental Researches of the University of Palermo (Italy) has built up a weather monitoring system that works 24 hours per day and makes data availa…

Evaluation of building heating loads with dimensional analysis: Application of the Buckingham π theorem

Abstract A detailed assessment of building energy performance requires a large amount of input data concerning building typology, environmental conditions, envelope thermophysical properties, geometry, control strategies, and several other parameters. Notwithstanding, the use of specialized software tools poses many challenges in regards to the retrieval of reliable and detailed information, setting a steep learning curve for engineers and energy managers. To speed up the preliminary assessment phase, it might be more convenient to resort to a simplified model that allows the evaluation of heating energy demand with a good level of accuracy and without excessive computational cost or user e…

A NEW FIVE-PARAMETER MODEL FOR PV PANELS-EXPERIMENTAL VALIDATION ON A POLYCRYSTALLINE MODULE

A new five-parameters model to describe the relation between the electric current and the voltage for a photovoltaic module is experimentally validated on the field, with variable conditions of operative temperature and solar irradiance. The electrical parameters of the one diode equivalent circuit are found by solving an equations system based on the data commonly issued by manufacturers in standard test conditions. To verify the capability of the new model to fit PV panel characteristics, the model was tested on two different panels comparing the results both with the data issued by manufacturers and with the results obtained using the five- parameters model already proposed by other Auth…

Forecasting the Cell Temperature of PV Modules with an Adaptive System

The need to reduce energy consumptions and to optimize the processes of energy production has pushed the technology towards the implementation of hybrid systems for combined production of electric and thermal energy. In particular, recent researches look with interest at the installation of hybrid system PV/T. To improve the energy performance of these systems, it is necessary to know the operating temperature of the photovoltaic modules. Furthermore, when photovoltaic (PV) systems replace the traditional building envelope materials and they are fully integrated (building integrated photovoltaic (BIPV)), it is very important to correctly assess their thermal behaviour. The determination of …

Life cycle assessment of a solar thermal collector

A Neural Network Model to Forecast Urban Electricity Consumptions from Weather Data

Design di edifici a energia netta zero alla luce della Direttiva Europea 2010/31/CE (EPBD recast) sulla prestazione energetica nell'edilizia [GU europea del 18 giugno 2010 (L 153)]

Il presente lavoro descrive dettagliatamente gli studi e le attività svolte in seno al progetto di ricerca “Design di edifici a energia netta zero alla luce della direttiva europea 2010/31/CE (EPBD Recast) sulla prestazione energetica nell’edilizia GU Europea del 18 giugno 2010 (L153)”. L’attività di approfondimento sull’edificio oggetto di studio, la Leaf House, è stata svolta nell’ambito dei diversi filoni di ricerca di seguito elencati: 1. Analisi dei dati dell’edificio esistente, 2. Redesign dell’edificio esistente, 3. Embodied energy dell’edificio esistente. 4. Partecipazione a gruppi di lavoro internazionali in seno alla task 40 dell’IEA. Gli indicatori sviluppati nel corso dei lavori…

Le caratteristiche termofisiche del patrimonio edilizio della città di Palermo

Un ambiente confinato è un rapporto continuo con il contesto bioclimatico esterno attraverso l'involucro edilizio, che notoriamente svolge una funzione di protezione e di filtro rispetto agli input esterni. Una corretta ottimizzazione della interfaccia edificio clima è legata, fra gli altri fattori, anche alla selezione di materiali le cui carayyeristiche termofisiche siano tali da agevolare il conseguimento della suddetta ottimizzazione. In particolare, la conoscenza del tempo di ritardo fra l'onda termica incidente e quella emergente all'interno dello spazio confinato, associata alla stima del fattore di attenuazione del flusso di calore, è presupposto di base per una corretta progettazio…

Catalogo tipologico degli elementi della architettura mediterranea - "Le caratteristiche termofisiche del patrimonio edilizio della città di Palermo"

Studio e progettazione di un sistema di smaltimento statico del calore

Nell’ambito di questa attività sono stati svolti lo studio e la progettazione di un sistema di smaltimento statico del calore da adottare in accoppiamento con sistemi solari termici per evitare il rischio di stagnazione dovuto al mancato utilizzo dell’energia termica prodotta (bassa richiesta di energia termica, assenza dell’alimentazione elettrica). I componenti idraulici comunemente installati negli impianti solari ovvero vaso di espansione, valvole di sicurezza, sfiati e valvole di scarico termico garantiscono l’incolumità degli utilizzatori dai possibili problemi che nascono dall’aumento incontrollato di pressione e temperatura all’interno dell’impianto, ma possono portare ad un parzial…

Test funzionali ed ottimizzazione delle performance di due prototipi di condizionatore d’aria compatti Solar DEC

Nell’ambito di questo lavoro di ricerca è stata svolta una estesa campagna di monitoraggio per il sistema Solar DEC freescoo residential installato nell’estate del 2014 presso il Dipartimento DEIM dell’Università di Palermo. In una prima fase dello studio sono state svolte delle prove preliminari volte ad identificare problematiche al funzionamento di alcuni dei componenti interni. In particolare è stata posta attenzione al miglioramento del funzionamento dello scambiatore evaporativo e dei componenti coinvolti nel processo di deumidificazione dell’aria. E’stato aggiornato il sistema di monitoraggio e migliorata la logica di controllo dei letti adsorbenti. Relativamente alle prestazioni ene…