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

Optimization of trigeneration systems by Mathematical Programming: Influence of plant scheme and boundary conditions

Abstract The large potential for energy saving by cogeneration and trigeneration in the building sector is scarcely exploited due to a number of obstacles in making the investments attractive. The analyst often encounters difficulties in identifying optimal design and operation strategies, since a number of factors, either endogenous (i.e. related with the energy load profiles) and exogenous (i.e. related with external conditions like energy prices and support mechanisms), influence the economic viability. In this paper a decision tool is adopted, which represents an upgrade of a software analyzed in previous papers; the tool simultaneously optimizes the plant lay-out, the sizes of the main…

Assessing the feasibility of cogeneration retrofit and district heating/cooling networks in small Italian islands

Sustainability of energy supply strategies in small islands has been emerging as a severe issue, due to the large margins for improvement and rationalization of the most frequently adopted solutions. In most of the European islands, large amounts of heat are wasted by the operation of engine-based power plants; conversely, heat is produced by boilers (supplied by liquid fuels) or by electric equipment for a number of different uses, like domestic hot water production or space heating in winter. In this paper a techno-economic analysis is proposed to assess the feasibility of CHP-retrofit of the existing power plants and the possible utilization of the recovered heat to supply, via a distric…

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…

Building energy performance forecasting: A multiple linear regression approach

Abstract Different ways to evaluate the building energy balance can be found in literature, including comprehensive techniques, statistical and machine-learning methods and hybrid approaches. The identification of the most suitable approach is important to accelerate the preliminary energy assessment. In the first category, several numerical methods have been developed and implemented in specialised software using different mathematical languages. However, these tools require an expert user and a model calibration. The authors, in order to overcome these limitations, have developed an alternative, reliable linear regression model to determine building energy needs. Starting from a detailed …

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…

Building energy demand assessment through heating degree days: the importance of a climatic dataset

Abstract The weather is one of the main factors to consider when designing a building because it represents the most important boundary condition to affect the dynamic behaviour of the building. In the literature, many studies use the degree day to predict building energy demand. However, linking the results obtained from a generic building simulation tool with defined degree days, will not give reliable energy evaluation. The goal of this study is to demonstrate that the assessment of building energy demand through the use of the degree day is correct only if the determination of the climate index is a function of the same weather data. The relationship between Heating Degree-Day and heati…

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…

Artificial Neural Networks to assess energy and environmental performance of buildings: An Italian case study

Abstract Approximately 40% of the European energy consumption and a large proportion of environmental impacts are related to the building sector. However, the selection of adequate and correct designs can provide considerable energy savings and reduce environmental impacts. To achieve this objective, a simultaneous energy and environmental assessment of a building's life cycle is necessary. To date, the resolution of this complex problem is entrusted to numerous software and calculation algorithms that are often complex to use. They involve long diagnosis phases and are characterised by the lack of a common language. Despite the efforts by the scientific community in the building sector, th…

Regression analysis to design a solar thermal collector for occasional use

Abstract Optimal design of a solar thermal system is necessary to minimize payback time and to diffuse renewable energy use for Domestic Hot Water production in residential areas. More accurate design is crucial in the case of seasonal or occasional use of the system; indeed, the standard criteria generally applied to a design system for continuous use, can lead to considerable over-sizing. To speed up the design phase and to help the planner in the identification of the best solution without any complex evaluation or long computational time, it would be interesting to have available a simpler method than the standard procedures, but one that is reliable and accurate for the evaluation of t…

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…

An overview of energy retrofit actions feasibility on Italian historical buildings

Abstract Italian energy policy has determined important keystones in building energy efficiency regulations and their application throughout the country. However, there is still much work to be done in order to make sustainable societies and territories, especially in historical contexts that have the greatest potentiality of energy saving. In detail, in the framework of conservation, restoration, refurbishment, and retrofit actions, the debate among scientists, administrators and skilled people is still open due to the many aspects yet to be considered and solved. In this paper, the state of the art of Italian residential building heritage has been reviewed, while energy retrofit issues an…

Application of optimized artificial intelligence algorithm to evaluate the heating energy demand of non-residential buildings at European level

Abstract A reliable preliminary forecast of heating energy demand of a building by using a detailed dynamic simulation software typically requires an in-depth knowledge of the thermal balance, several input data and a very skilled user. The authors will describe how to use Artificial Neural Networks to predict the demand for thermal energy linked to the winter climatization of non-residential buildings. To train the neural network it was necessary to develop an accurate energy database that represents the basis of the training of a specific Artificial Neural Networks. Data came from detailed dynamic simulations performed in the TRNSYS environment. The models were built according to the stan…

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

Multi-Energy School System for Seasonal Use in the Mediterranean Area

School buildings represent an energy-consuming sector of real estate where different efficiency actions are necessary. The literature shows how the design of a multi-energy system offers numerous advantages, however, there are problems related to the integration of cogeneration units with renewable energy sources due to the low flexibility of the first one and the high degree of uncertainty of the latter. The authors provide an alternative solution through the analysis of a case study consisting of a multiple energy system in three Sicilian schools, focusing on the system&rsquo

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…

A Procedure for the Producibility Curve Identification of a Dish-Stirling Plant, Starting from Experimental Data

This article presents a procedure for the producibility curve identification of a dish-Stirling plant, starting from experimental data. The producibility data was measured, recorded, analysed, filtered and monthly aggregated. Moreover, the incidence of the ambient temperature and of the mirrors cleaning on producibility data is highlighted and a procedure to normalize the measured data in temperature and cleaning level was developed. To provide a validation of the developed procedure the producibility curves at 25 °C have been obtained and compared with the one issued by the manufacturer. The two curves are in good agreement, presenting a maximum deviation of the 7 %.

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…

A device for PV modules I-V characteristic detection

In this paper an electronic load suitable for the PV module I-V characteristic curve fast detection is presented. This device is designed in agreement with the IEC 82 Techinical Committee Standard since it allows the detection of the characteristic starting from voltage values even lower than 3% of the PV module open circuit voltage. The device main features are short time characteristc detection (2 s), limited ripple of the detected characteristic and low cost. Its validation is carried out by comparing measured data with data from simulations. Simulations are carried out considering two different commercial PV modules and by implementing in Matlab-Simulink environment the four lumped para…

A solar assisted seasonal borehole thermal energy system for a non-residential building in the Mediterranean area

Abstract Solar heating and cooling systems are reliable and feasible solutions among renewable energy technologies. Indeed, solar thermal devices help reduce primary energy consumption and can reduce electricity demand, thus representing one of the best options for satisfying heating and/or cooling energy supply. The Borehole Thermal Energy Storage (BTES) represents one of the best promising option among the various storage technologies, because the size of the storage can be easily extended by drilling additional boreholes and simply connecting the pipes to the existing boreholes; the overall energy efficiency of this system is about 40–60%. In this paper, the authors present an applicatio…

Modelling and analysis of real-world wind turbine power curves: Assessing deviations from nominal curve by neural networks

Abstract The power curve of a wind turbine describes the generated power versus instantaneous wind speed. Assessing wind turbine performance under laboratory ideal conditions will always tend to be optimistic and rarely reflects how the turbine actually behaves in a real situation. Occasionally, some aerogenerators produce significantly different from nominal power curve, causing economic losses to the promoters of the investment. Our research aims to model actual wind turbine power curve and its variation from nominal power curve. The study was carried out in three different phases starting from wind speed and related power production data of a Senvion MM92 aero-generator with a rated powe…

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, …

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 …

A methodology for optimisation of solar dish-Stirling systems size, based on the local frequency distribution of direct normal irradiance

Abstract In geographical areas where direct solar irradiation levels are relatively high, concentrated solar energy systems are one of the most promising green energy technologies. Dish-Stirling systems are those that achieve the highest levels of solar-to-electric conversion efficiency, and yet they are still among the least common commercially available technologies. This paper focuses on a strategy aimed at promoting greater diffusion of dish-Stirling systems, which involves optimizing the size of the collector aperture area based on the hourly frequency distributions of beam irradiance and defining a new incentive scheme with a feed-in tariff that is variable with the installed costs of…

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…

Thermal characterization of insulating materials

Abstract The strict energy saving standards are based on the declared values of the materials, i.e. U-value, thermal conductivity or thermal capacity. To this end, proper knowledge of the thermophysical properties of the wall components is needed, especially with regard to new lightweight technologies that are being used in building construction/refurbishment, under the dynamic conditions of the Mediterranean climate, where one of most important parameters of building materials is their heat capacity because of the influence of solar radiation energy. With this regard, the actual heat capacity value, obtained in laboratory tests, is typically quite different from the nominal one. So, this p…

Energy saving and user satisfaction for a new advanced public lighting system

Abstract The retrofit of urban lighting systems is often an advantageous means of achieving notable energy savings and improvements in the quality of light. User habits, expectations and lifestyle can contribute to the design of these systems, for example in deciding on the most appropriate control strategies or the light quality. The influence of such variables can be extended to the overall system performance. This paper presents a method of street lighting design based on two kinds of analysis carried out in a defined test area: measurements (by means of a monitoring study) and user preferences (by means of a survey). The results of this data analysis create the basis for the final desig…

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…

Multiple criteria assessment of methods for forecasting building thermal energy demand

Abstract Nowadays worldwide directives have focused the attention on improving energy efficiency in the building sector. The research of models able to predict the energy consumption from the first design and energy planning phase is conducted to improve building sustainability. Use of traditional forecasting tools for building thermal energy demand tends to encounter difficulties relevant to the amount of data required, implementation of the models, computational costs and inability to generalize the output. Therefore, many studies focused on the research and development of alternative resolution methods, but the choice of the most convenient is not clear and simple. Single comparison of s…

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).

Dynamic thermal simulation of buildings: a case study to validate ESP-r software

Energy aspects and environmental problems have a key role in the definition of building’s design, management and maintenance. The energy saving and the decrease of environmental impact throughout the life cycle assessment of buildings maintaining an high level of comfort are Key points for a modern and sustainable construction (total quality of the building). In fact, the building’s design has to be considered the result of a multi-objective problem. Furthermore the European Directive 2002/91/EC issues the sustainable themes on the energy performance of buildings [1], and include the energy certification of new buildings with effect from 2006

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…

Evaluation of equilibrium moisture content in ligno-cellulosic residues of olive culture

The use of ligno-cellulosic residuals from agriculture as means for renewable energy production is well known; nonetheless significant problems still exist on development of bioenergy value chains. Moisture content and hygroscopicity are among these problems. Higher moisture content of the biomass means lower calorific value and higher perishability, hence storage difficulties. For this reason it is important to evaluate how the moisture content of the material varies while it is stored and how the calorific value of the feedstock is affected by it. The purpose of this study is to determine the variation of moisture content and its influence on lower calorific value (LCV) of four types of s…

Assessment of indoor illuminance and study on best photosensors' position for design and commissioning of Daylight Linked Control Systems. A new method based on Artificial Neural Networks

Abstract Artificial lighting systems have to ensure appropriate illuminance with high energy efficiency according to best design practice and technical standards. These aims can be tackled, by incorporating a Daylight linked control system. However, the system behaviour is strongly influenced by several factors and, in particular, by the sensors' position. Indeed, very often the illuminance on work-plane is not fully correlated with illuminance measured by the photo-sensor used to control the luminaires. This fact leads to wrong information for the Daylight linked control systems affecting its efficacy. The artificial intelligence of Neural Networks can be exploited to provide a method for …

Redesign of a Rural Building in a Heritage Site in Italy: Towards the Net Zero Energy Target

In order to achieve the ambitious objective of decarbonising the economy, it is mandatory, especially in Europe and in Italy, to include the retrofitting of existing buildings. In a country where a large share of existing buildings have heritage value, it is important to design effective retrofit solutions also in historical buildings. In this context, the paper describes the experience of re-design of an existing rural building located in Sicily, inside the ancient Greeks' “Valley of the Temples”. An energy audit was performed on the building, and its energy uses were thoroughly investigated. A building model was developed in the TRNSYS environment and its performances validated. The valid…

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…

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

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…

Supporting public decision process in buildings energy retrofitting operations: the application of a Multiple Criteria Decision Aiding model to a case study in Southern Italy

Abstract The challenge of promoting sustainable cities and reaching the objectives developed by the European Green Deal includes the renovation of the building sector, as it is responsible for 40% of energy consumption in Europe. Regional or local public administrations have to allocate their financial resources for improving the energy performances of their building stock and to face a multidimensional problem, where different aspects – such as energy efficiency, financial-economic feasibility and environmental protection – have to be harmonized. The present study proposes a Multiple Criteria Decision Aiding model, which includes the ELECTRE TRI-nC method, for supporting the public decisio…

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

ANALISI DEL CICLO DI VITA DEL MICROELICO: UN CASO STUDIO IN SICILIA

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…

Concrete thermal energy storage for linear Fresnel collectors: Exploiting the South Mediterranean’s solar potential for agri-food processes

Abstract Italy is celebrated in the world for its agri-food industries while the process of production of pasta is highly energy demanding and requires both electrical and thermal energy simultaneously. Because most of the Italian factories producing pasta are located in the Southern part of the country, the direct use of thermal energy generated from the sun would be particularly profitable. In this study, the authors examine the possibility of generating by a Solar Industrial Process Heating plant the thermal energy required annually by an existing factory that produces durum wheat pasta located in Sicily (Italy). The hypothesized plant scheme consists of an array of Fresnel linear solar …

Energy and economic analysis and feasibility of retrofit actions in Italian residential historical buildings

Abstract The application of retrofit actions to existing building stocks can improve the energy performance of the residential sector. In this context, particular attention should be given to historical buildings, which represent a large part of the Italian building stock. To improve the energy performance of them, adequate retrofit actions must be applied. Many studies and regulations have focused on identifying the best refurbishment measures. However, the selection of these measures is difficult due to restrictive regulations, which are dictated by the Ministry of Cultural Heritage and Activities, high retrofit costs, and variable climate zones. Thus, energy renovations in Italian buildi…

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…

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…

Realization of an Energetic Hub Based on a High-Performance Dish Stirling Plant

In this work the realization of an energetic hub based on a high-performances dish Stirling system, at the DEIM of the University of Palermo, is presented. The realized system is the first top rated solar thermodynamic plant directly connected to the national electric grid. The connection permits the electricity injection into the grid and allows to access to national renewable energy incentives regime. The system realization was possible thanks to an international cooperation between the University of Palermo and the private company Horizon S.r.l., official partner of Ripasso Energy AB, owner of this technology. Initial data of the plant energy production and the foreseen improvements for …

The Energy System of Sicilian Region, Italy: 2014 situation and evolutionary trends

The development of reliable energy scenarios are become increasingly more important and crucial due to scientific interest but also because it is essential for the deployment of effective energy policies in the territory. The depletion of Fossil Fuels and the need for the most industrialized countries to achieve the target of a sustainable development have induced important national, European and global initiatives. These actions have led to major changes on each energy system of countries and regions, contributing to the evolution of new local energy systems. In this paper, the Authors have collected, processed and analyzed the data concerning the evolution and changes of the Sicilian ener…

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…

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.

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…

sistemi di gestione ambientale applicati al prodotto: un caso studio viti-vinicolo

I Sistemi di Gestione Ambientale (SGA) Orientati al Prodotto (POEMS – Product Oriented Environmental Management System) rappresentano un’evoluzione dei SGA già diffusi nel contesto nazionale ed internazionale. I POEMS combinano elementi consolidati dei SGA con aspetti di ciclo di vita dei prodotti, permettendo alle aziende di sviluppare e promuovere nel mercato prodotti che si contraddistinguano per la loro qualità ecologica. L’articolo presenta un’analisi delle peculiarità metodologiche dei POEMS e descrive un’applicazione sperimentale ad un’azienda vitivinicola siciliana.

Exergoeconomic analysis as a tool for supporting the design and operation of multiple chiller systems in air conditioning applications.

Multiple-Chillers systems represent viable solutions for medium/large-scale air conditioning applications. In these systems, however, design and energy savings are highly affected by the configuration and operation strategies adopted. For instance, when considering multiple chillers of same size, “symmetric” or “sequential” load sharing strategies are two viable options. Conversely, when considering chillers of different sizes, a wide combination of chillers cooling capacities may be adopted. It is apparent that an integrated analysis of the design and operation of these systems should be carried out in order to achieve profitable energy saving. With this respect, Exergoeconomics, which res…

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…

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…

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

Energy retrofit actions on Italian historical buildings: energy efficiency and feasibility. A review study.

Today in EU, the growth in global primary energy consumption is decreasing. In 2014, Italy contributed with a global reduction of 17.1%, thanks to the application of EU measures on different areas. However, there is still much work to be done in order to make sustainable societies and territories, especially in buildings sector that has the greatest potentiality of energy saving. In particular, in the framework of Conservation, Restoration, Refurbishment, and Retrofit actions, the debate is still open, because many aspects must be considered and solved yet. In this paper, the state of the art of the Italian residential building heritage has been reviewed, applicable energy retrofit issues a…

Road Thermal Collector for Building Heating in South Europe: Numerical Modeling and Design of an Experimental Set-Up

The combination/integration of renewable energy and storage systems appears to have significant potential, achieving high-energy results with lower costs and emissions. One way to cover the thermal needs of a building is through solar energy and its seasonal storage in the ground. The SMARTEP project aims to create an experimental area that provides for the construction of a road solar thermal collector directly connected to a seasonal low-temperature geothermal storage with vertical boreholes. The storage can be connected to a ground-to-water heat pump for building acclimatization. This system will meet the requirements of visual impact and reduction of the occupied area. Nevertheless, sev…

Exergoeconomic analysis as support in decision-making for the design and operation of multiple chiller systems in air conditioning applications

Abstract Multiple-chillers systems represent viable solutions for medium/large-scale air conditioning applications characterized by variable cooling demand. The energy efficiency of such systems is influenced by the number of chillers, the combination of cooling capacities, and the load-sharing among the units. Large efforts have been devoted to developing efficient operation strategies for these systems, but rules of thumb are usually adopted for selecting cooling capacities thus leaving room for energy and economic savings. In this paper, exergoeconomic analysis is proposed as a promising method to identify near-optimal design and operation strategies, due to the capability of exergoecono…

Deep learning strategies for automatic fault diagnosis in photovoltaic systems by thermographic images

Abstract Losses of electricity production in photovoltaic systems are mainly caused by the presence of faults that affect the efficiency of the systems. The identification of any overheating in a photovoltaic module, through the thermographic non-destructive test, may be essential to maintain the correct functioning of the photovoltaic system quickly and cost-effectively, without interrupting its normal operation. This work proposes a system for the automatic classification of thermographic images using a convolutional neural network, developed via open-source libraries. To reduce image noise, various pre-processing strategies were evaluated, including normalization and homogenization of pi…

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 …

Effects of the air density value on a wind generator electricity production capability

The paper main issue is the evaluation of the influence of the air density value on the electricity production capability of a wind generator. Two different density air mathematical models, where the density has not a constant value, are here taken into account and compared in terms of reliability, accuracy and computational burden. Evaluations are carried out thanks to a horizontal axis wind generator full model built by the Authors in Matlab/Simulink environment. Simulation results are compared with real data.

Uno strumento virtuale per il monitoraggio e il controllo di un impianto fotovoltaico a concentrazione

In questa memoria si presenta una sintesi delle attività condotte nell'ambito del progetto SERPICO ("Sviluppo E Realizzazione di Prototipi di Inverter per impianti fotovoltaici a Concentrazione", PO-FESR Sicilia 2007-2013, Misura 4.1.1.2). Il progetto ha riguardato lo sviluppo di un prototipo di impianto fotovoltaico-termico a concentrazione e del relativo sistema di monitoraggio e controllo. Tale sistema permette di acquisire le quantità sia elettriche che termiche. Inoltre esso implementa un algoritmo per l'inseguimento solare utilizzato per ottimizzare la produzione di potenza.

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…