1,721,008 research outputs found
Benessere termoigrometrico in ambiente esterno ed interno: sviluppo di modelli predittivi, analisi di materiali innovativi e ripercussioni sui consumi energetici
Full text linkNell’ambito del presente lavoro di tesi sono stati investigati differenti aspetti legati al thermal comfort in ambiente interno ed esterno. Per quanto concerne gli ambienti aperti, sono stati sviluppati modelli predittivi della percezione termoigrometrica, è stata valutata l’influenza sul microclima di materiali innovativi e di varie strategie di mitigazione e si è proceduto a mappare, attraverso opportuni indici, il territorio italiano e globale in relazione anche ai flussi turistici nazionali ed intercontinentali. Per gli spazi indoor è stata invece valutata la relazione intercorrente tra sensazione termica e temperatura di colore della luce con l’obiettivo di ridurre i consumi energetici.
La tesi è stata quindi suddivisa in cinque sezioni. Nella prima sono stati individuati, con riferimento all’area mediterranea, i valori della Physiological Equivalent Temperature (PET) neutrale e preferita, della temperatura dell’aria neutrale, del Physiological Equivalent Temperature (PET) comfort range ed è stato ricavato un nuovo indice empirico in grado di predire, sulla base dell’ASHRAE 7-point scale, la sensazione termica della popolazione mediterranea in ambienti aperti. Questo indice, denominato MOCI (Mediterranean Outdoor Comfort Index), predice però un voto medio ed è per tale ragione che è stata anche riadattata alla popolazione mediterranea la relazione della PPD (Predicted Percentage of Dissatisfied) proposta nell’ISO 7730.
Le prestazioni del MOCI sono state poi confrontate numericamente con quelle di Actual Sensation Vote Europe (ASVEUROPE), Effective Temperature (ET), Physiological Equivalent Temperature (PET) e Predicted Mean Vote.
È stato inoltre proposto e validato il Global Outdoor Comfort Index (GOCI), un indice empirico in grado di predire la percezione termica a livello globale.
Nella seconda sezione sono state invece analizzate differenti strategie di mitigazione del microclima urbano. I siti analizzati sono il campus dell’Università degli Studi Sapienza di Roma, il chiostro di San Pietro in Vincoli (sede della Facoltà di Ingegneria del medesimo Ateneo) ed il canyon urbano di via delle Carrozze, anch’esso sito in Roma. Oltre ad un aumento dello urban greening, sono state implementate configurazioni caratterizzate dall’uso di materiali ad elevato coefficiente di albedo. L’analisi dei valori assunti dalle variabili micrometeorologiche e dagli indici di comfort termico è stata possibile grazie a modelli validati sperimentalmente ed elaborati attraverso il software ENVI-met. Per quest’ultimo, è stato inoltre proposto un nuovo approccio simulativo basato su dati provenienti da radiosondaggi.
Nella terza sezione è stata valutata, con riferimento al territorio italiano e mondiale, la percezione termica di un individuo afferente all’area mediterranea (mediante il MOCI) e quella di un normotipo globale (mediante il PMV). I risultati, relazionati ai flussi turistici, sono stati elaborati in termini di andamenti orari annuali, valori medi settimanali e relativi picchi, diagrammi di frequenza, variazioni dei percentili e mappe spaziali.
Nella quarta sezione, differentemente rispetto a quanto fatto in precedenza, vengono discussi aspetti legati al benessere termoigrometrico in ambiente interno. In particolare, si è cercato di valutare se la temperatura di colore della luce è in grado o meno di influenzare la percezione termica. Questo studio è stato effettuato in collaborazione con la “Escuela Técnica Superior de Ingeniería de Caminos, Canales y Puertos de la Universidad de Granada” e mira a ridurre i consumi energetici degli edifici. Per esempio, la temperatura di uno spazio confinato potrebbe essere inferiore in presenza di una luce con bassa temperatura di colore durante la stagione di riscaldamento e viceversa durante quella di raffrescamento. È stata quindi organizzata, all’interno di una test room, una field survey in cui sono state esaminate la percezione e preferenza termica, la tolleranza e l’accettabilità personale e la confortevolezza nello svolgere un dato compito in presenza di luce calda, neutrale e fredda.
Nella quinta ed ultima sezione vengono infine riportati i risultati ottenuti
Parameters affecting the efficiency of a heat transformer with a particular focus on the heat solution
Full text linkThe heat transformer is a reverse cycle absorption machine, suitable for the direct exploitation of heat wastes and solar energy. Part of these wastes are “transformed” into thermal energy at a higher temperature than the one provided. Hence some studies concern the evaluation of the performances of the working fluids used. They must ensure a high level of efficiency which, as for the conventional absorption machines, depends on several parameters. One of these parameters is the heat solution: it is defined as the heat absorbed when a mole of a given component is mixed with the amount of the other component required to generate the desired solution at a certain temperature and pressure. This is the reason why the decision was to examine its influence with respect to machines exerting two different fluids which are generally used. The first one is NH3-H2O, whereas the second is H2O-LiBr; they used as refrigerating substances ammonia and water respectively and as absorption substances water and lithium bromide. Through an analytical modeling and the processing of experimental data provided by the bibliography, it was possible to show how, for these fluids, the terms of the sensible heat represent a moderate fraction of the global energy balance, at one condition though: highly efficient recovery exchangers must be present. Moreover there were reported values of the refrigeration effect of the order of thousands of kJ/kg with satisfying responses energetically speaking. Then a high stability of the fluid NH3-H2O was revealed, as testified by the high value of the difference between the concentration of the refrigerator in the absorber and the concentration of the refrigerator in the generato
Lighting project for Basilica of San Francesco in Assisi
No full textThe Basilica of San Francesco in Assisi, an UNESCO World Heritage Site thanks to its ancient frescoes of worldwide preciousness made by several artists including Giotto, is also one of the most important places of Christian pilgrimage. The biggest challenge in achieving these goals is to find a strong common theme to illuminate the three very dif-ferent parts of which the basilica consists: Crypt, Lower Basilica, and Upper Basilica. For the first part, the Crypt, we are dealing with the replacement of a simple system of graz-ing light whose difficulty lies mainly in maintenance aspects: it stays turned on 24/7 and therefore needs stable and energy saving luminaires. On the contrary the existing system of the other two parts, Lower and Upper Basilica, is inadequate and needs to be com-pletely redesigned, following an a univocal philosophy into two environments with diverse morphological characteristics. The upper Basilica stands out against the sky, its bright and spacious interior develops a significant height, while the lower Basilica was designed as an enormous crypt with ribbed vaults and dark frescoes and represents thus a compressed and gloomy space. The main unifying element between the two is the division of the nave into four bays with cross-vaulted ceiling, a transept and a polygonal apse, starting from this we chose, for the new lighting, a common typological element: a central, suspended chandelier dedicated to each section
Decrease of the Maximum Speed in Highway Tunnels as a Measure to Foster Energy Savings and Sustainability
Full text linkThe high energy consumption of the lighting installations in highway tunnels has become
a hot topic in the last few years due to the high figures in terms of money, consumed energy, use of raw
materials, emissions of greenhouse gases due to the remarkable number of manufactured elements,
and maintenance, among others. In spite of the different strategies proposed up to date and their
savings, the potential benefits of decreasing the maximum speed allowed in tunnels have not been
considered in depth as a complementary measure yet. In this work, the impact of such a decrease in
terms of energy consumption, number projectors, carbon dioxide (CO2) emissions, and yearly costs
in energy is analyzed and discussed. The results strongly suggest the convenience of introducing
maximum speed reduction in traffic regulations which, in addition, could create positive synergies
with traffic safety.This work was supported by the Spanish Ministry of Economy and Competitiveness as part of the
Research Project ENE2015-67031-R (MINECO/FEDER)
How high albedo and traditional buildings’ materials and vegetation affect the quality of urban microclimate. A case study
No full textThe wellbeing and life quality also depend on the climatic conditions of the surrounding environment. In this case study the focus is on those interventions that can be performed, especially on enclosed urban contexts, to control the thermal environment. It pays attention on the effect of the vegetation and high albedo materials characterizing horizontal and vertical boundaries of the site and the Cloister by Giuliano da Sangallo, a historical site in Rome, is taken as case study. The model of the site was simulated with the software ENVI-met and it was verified thanks to a measurement campaign in situ. Five scenarios with different vertical and horizontal materials of the present buildings were simulated together with an analysis of the variations of physical quantities (air temperature, mean radiant temperature, relative humidity, wind speed) affecting the perception of environmental comfort (calculated through the Predicted Mean Vote).
The result is that in those areas characterized by a Mediterranean climate, where the summer months with high temperatures must be mitigated, the vegetation can be a significant benefit to the environment, and high albedo materials can ease the thermal load of the buildings with a higher thermal stress for the pedestrians
Future energy demands of European buildings in the framework of climate change: A scoping study
Full text linkClimate change is considered an important global threat, with a significant impact on the energy performance, since buildings will be subjected to higher average outdoor temperatures. This paper explores the relative impact of global warming across the different regional climates of Europe comparing present and estimated future energy needs of a hypothetical residential house located in 19 cities characterized by different latitude and Köppen-Geiger class. Building performance simulations with EnergyPlus are performed in order to simulate the heating and cooling needs of the building and the associated CO2 emissions in the present and in the future. The progressive increase in average temperatures in 2050 and 2080 leads to a general decrease of thermal energy request for heating and to an increase in the demand for electricity for cooling especially in the southern Europe, where high carbon intensity coefficients cause large CO2 emissions. The resulting vicious circle can be interrupted by increasing the energy efficiency of buildings and properly converting thermoelectric power plants
A first approach to natural thermoventilation of residential buildings through solar chimneys supplied by solar ponds
No full textThe exploitation of natural ventilation is a good solution to improve buildings from an energetic point of view and to fulfill the requirements demanded by the thermoigrometric comfort and the air quality in enclosed spaces. Some past researches demonstrated how some devices, useful to this purpose, follow the principles of solar chimneys and are able to move air masses while exploiting the Archimedes thrust. The natural ventilation must be supplied by a flow moving upward generated by a heat source performing at temperatures slightly higher than the one present in the environment. To have a minimum energetic effect, the heat can be extracted from solar ponds; solar ponds are able to collect and store solar energy in the geographical regions characterized by sufficient values of solar radiation. Thus it is possible, in summer, to provoke a nocturnal natural ventilation useful for the air change in indoor spaces (in those climatic areas where, during the night, there is a temperature gradient)
Implications of climate and outdoor thermal comfort on tourism: the case of Italy
No full textWhether a journey is pleasant or not usually depends on the climatic conditions which permit to perform outdoor activities. The perception of climatic conditions, determined by physiological and psychological factors, can vary according to different adaptation phenomena related to the person involved and the weather conditions of the place where they live. Studying the bioclimatology of a country characterized by a high flux of tourism, as e.g. Italy, can provide some important information about where and when is it better to visit a place. Some differences have to be specified though, like the local tourism, which is used to that type of climate, and international tourism, which is formed by people coming from countries with different types of climates. Therefore this paper examined the climatic conditions and outdoor thermal comfort through the Mediterranean Outdoor Comfort Index (MOCI) for local tourism and through the predicted mean vote (PMV) for international tourism. The cities examined were three (Venice, Rome and Palermo located in the North, Centre and South of Italy, respectively), where average information were collected every week for an entire year. Finally, a map of the entire Italian territory reporting the seasonal average values of these indexes was also reported
Relating microclimate, human thermal comfort and health during heat waves: An analysis of heat island mitigation strategies through a case study in an urban outdoor environment
No full textOver the past years the concern of the international scientific community towards the study of the Urban Heat Island (UHI) phenomenon has been growing. Such issue is particularly important in cities as Rome, where it is possible to experience intense heat stress conditions especially when heat waves intensify this phenomenon. Therefore this study wants to examine different mitigation strategies of the urban microclimate by taking into consideration the campus of the Sapienza University of Rome. It was carried out through the software ENVI-met V 3.1 which gave the possibility to reproduce the model of the site (experimentally calibrated) and examine, in terms of MOCI (Mediterranean Outdoor Comfort Index), the different mitigation strategies implemented. This index was also related to the Apparent Temperature and to the health risk. Among the main results provided through this study, it is possible to notice how the solution combining cool roofs, urban vegetation and cool pavement leads, with respect to the current configuration of the site, to a mean and maximum decrease in the MOCI of −2.5 and −3.5. Finally it is able to determine a decrease of about 60% in the health risk for those who are exposed
Outdoor thermal comfort conditions during summer in a cold semi-arid climate. A transversal field survey in Central Anatolia (Turkey)
No full textIn the present study the outdoor thermal comfort conditions in Konya (Central Anatolia, Turkey) were examined during summer. This is why a transversal field survey was carried out and over 300 questionnaires were filled by randomly chosen participants. Moreover, environmental variables as air temperature, wind speed, relative humidity and globe temperature were constantly measured. This allowed to relate the thermal perception and preference votes given by the interviewees to the morphological and furniture characteristics of the surveyed sites. Then, taking into account at the same time all the obtained data, a regression line between the thermal perception votes and the corresponding PET (Physiological Equivalent Temperature) values was obtained and a neutral PET value of 26.8 °C was calculated. Based on a logistic curve model with the probit function, a preferred PET value of 19.2 °C was determined. On the other hand, the PET comfort range of (21.6)–(32.0) °C was obtained by considering, as thermal comfort interval, the range (−0.5)-(+0.5) of the ASHRAE 7-point scale. Finally, two outdoor thermal comfort indexes were introduced. The first one, called Turkish Outdoor Comfort Index (TOCI), is able to predict the thermal perception of the considered population in hot conditions. In the second case, the Predicted Percentage of Dissatisfied (PPD) relation was modified based on the surveyed data and outdoor sites
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