A novel approach to CFD analysis of the urban environment

The construction of cities, with their buildings and human activities, not only changes the landscape, but also influences the local climate in a manner that depends on many different factors and parameters: weather conditions, urban thermo-physical and geometrical characteristics, anthropogenic moisture and heat sources. Land-cover and canopy structure play an important role in urban climatology and every environmental assessment and city design face with them. Inside the previous frame, the objective of this study is both to identify both the key design variables that alter the environment surrounding the buildings, and to quantified the extension area of these phenomena. The tool used for this study is a 2D computational fluid dynamics (CFD) numerical simulation considering different heights for buildings, temperature gaps between undisturbed air and building’s walls, velocities of undisturbed air. Results obtained allowed to find a novel approach to study urban canopies, giving a qualitative assessment on the contribution and definition of the total energy of the area surrounding the buildings

Thermophysical parameter estimation of multi-layer walls with stochastic optimization methods

The problem of the estimation of thermal conductivities of multi-layer walls is studied using genetic algorithms and simulated annealing. Parameter estimation is shown for the cases of three- and five- layer walls, comparing the two stochastic approaches and also contrasting them with deterministic gradient-based methods. It is shown how stochastic methods permit better performances than classical ones when initial estimations of parameter values are not available or when the problem becomes complex

A new concept of a thermal network for energy resilience in mountain communities powered by renewable sources

Currently, the technology of the Combined Heat–Power provides about 56% of the heat supply to District Heating in Europe. Many applications of the biomass cogenerators plant/district heating networks were developed, often improving the electrical energy efficiency supply. However, there has been no discussion about a comprehensive approach for developing a thermal network (both thermal and electrical energy supply) provided by the connection of more biomass CHPs-based DHs systems, guaranteeing the energy resilience of local communities. Two resilient energy system configurations were considered increasing the size of the energy systems components. Moving to the results, Case A (oversizing of the cogenerators plants) produces a major amount of electricity (8281 MWh/year of Case A compared to 6625 MWh/year of Case B) that can be sold to companies; however, the energy production of Case B (oversizing of both cogenerators and boilers plants) is well balanced with the mountain village’s needs. The Pay Back Period (4.39 years) and Profitability Index (4.88%) of Case B were also significantly better than those in Case A. This study gives, therefore, a relevant contribution to the definition of a new thermal network adaptable to different environments

Smart technologies: useful tools to assess the exposure to solar ultraviolet radiation for general population and outdoor workers

Beside some documented benefits attributed to ultraviolet solar radiation (solar UVR), a lot of adverse effects are a consequence of a chronic exposure, including the occurrence of photo-induced skin cancer. Improvement in risks perception, due to UVR overexposure, in the case of occupational or recreational exposure, is of great importance for public health. The amount of exposure to UVR has to be assessed as accurately as possible, with the aim to characterize different exposure conditions and, by their appropriate management, to prevent adverse health effects attributed to prolonged exposure to solar radiation (SR). The available technology allows to acquire such information, either using miniaturized and wearable sensors, or through devices who exploit radiative transfer models by integrating satellite-based radiometric data with meteorological data. We proceeded to an intercomparison to evaluate the performance of different devices in three commonly exposure conditions. Applications using satellite data, developed for preventing sunburn during recreational exposure, are adeguate for that purpose, while for a more accurate exposure assessment, only those which evaluate the irradiance in near real-time provide acceptable results. Unlike earlier, the low-cost devices that use wearable sensors showed inadequate performance for our purpose

Non visual effects of light: an overview and an Italian experience

Since the discovery of non-visual effect of light, consequences on human psychology and physiology have been investigated; however, effects on cognition of exposure to different spectral composition have been partially explored. Aim of this paper is an overview on researches developed in this field to compare general approaches and measurements protocols: the scarce knowledge of the physiological mechanisms, as well as the lack of shared methods, techniques, tools and procedures represent the weak point of this research. The impact of different procedures and experimental settings on results is shown, evidencing the need for scientifically consistent and internationally agreed procedures

A Method to Evaluate the Stimulation of a Real World Field of View by Means of a Spectroradiometric Analysis

Stimulation elicited by a real world field of view is related to the color, the intensity and the direction of the information reaching the eye: different spectral power distributions of light trigger different responses. An evaluation of the stimulation provided by the field of view can be performed by measuring the spectral radiance with a spectroradiometer and weighting this data with an efficiency curve. Different weights (physical, physiological and psychological) can lead to different analyses and consequently to different results. The proposed method allows an overall and simplified evaluation of the field of view based on spectral and luminance measures and a script that processes the luminous information. The final aim of this approach is to provide further information about the light stimulation reaching the retina and to supply a qualitative evaluation of the field of view, allowing to know how much stimulation is coming from a certain area within the visual field depending on the type of surface, basing on spectral and directional information. This approach can have practical implications, allowing technicians and designers to take into consideration the possible visual fields, in order to properly shape the features of stimulation throughout the day, hence following a field of view-based dynamic design

A Method to Evaluate the Stimulation of a Real World Field of View by Means of a Spectroradiometric Analysis

Stimulation elicited by a real world field of view is related to the color, the intensity and the direction of the information reaching the eye: different spectral power distributions of light trigger different responses. An evaluation of the stimulation provided by the field of view can be performed by measuring the spectral radiance with a spectroradiometer and weighting this data with an efficiency curve. Different weights (physical, physiological and psychological) can lead to different analyses and consequently to different results. The proposed method allows an overall and simplified evaluation of the field of view based on spectral and luminance measures and a script that processes the luminous information. The final aim of this approach is to provide further information about the light stimulation reaching the retina and to supply a qualitative evaluation of the field of view, allowing to know how much stimulation is coming from a certain area within the visual field depending on the type of surface, basing on spectral and directional information. This approach can have practical implications, allowing technicians and designers to take into consideration the possible visual fields, in order to properly shape the features of stimulation throughout the day, hence following a field of view-based dynamic design

Approfondimento sperimentale sulla capacità delle nuove sorgenti di illuminazione artificiale di influenzare le performance, la qualità e la quantità del sonno

Negli ultimi anni la ricerca internazionale ha dimostrato che esiste una stretta relazione tra radiazione luminosa e ritmi circadiani, influenza del comportamento umano e stimolazione del funzionamento cerebrale; tali effetti non-visivi sembrano dipendere principalmente dall’intensità luminosa, dalla composizione spettrale, dalla durata dell’esposizione e dall’ora del giorno in cui essa avviene, ma ad oggi non sono ancora chiari gli effetti su specifiche funzioni cognitive, né si può considerare sufficientemente nota l’influenza delle nuova tecnologia LED. In quest’ambito, precedenti studi svolti dallo stesso gruppo hanno evidenziato che, rispetto all’illuminazione prodotta con sorgenti alogene, un’illuminazione LED con temperatura correlata di colore (CCT) neutra (4000K), produce effetti positivi su alcuni aspetti dell’attenzione, quali le funzioni esecutive e la vigilanza visiva: con l’illuminazione LED è stata riscontrata la capacità di produrre molteplici rappresentazioni mentali contemporaneamente e di incrementare il livello di vigilanza durante l’esecuzione di un compito di attenzione. La presente attività approfondisce gli studi svolti precedentemente considerando sorgenti con differente composizione spettrale e temperatura di colore: in un primo esperimento sono state confrontate le stesse lampade utilizzate nei lavori precedenti, alogene e LED neutro, ed in un secondo esperimento lo studio è stato ripetuto con due scenari luminosi LED, con temperatura correlata di colore calda (3000 K) e fredda (6800), per investigare la differente influenza che tali sorgenti hanno a livello psicofisiologico. In entrambi gli esperimenti sono stati analizzati sia gli effetti immediati sulle capacità attentive in un compito di vigilanza cross-modale, sia gli effetti conseguenti sul sonno. I risultati di questo studio mostrano un effetto positivo delle illuminazioni sperimentali (LED 4000 K e LED 6800 K) sulle prestazioni di vigilanza visiva, ma non sulla vigilanza acustica, se paragonato alle illuminazioni calde (alogena 2800 K e LED 3000 K), e l’assenza di effetti significativi dell’illuminazione, sia alogena sia LED, sul sonno dei soggetti partecipanti. La conoscenza approfondita dell’influenza che la luce ha sulla mente umana a livello cognitivo apre la strada ad una nuova tipologia di progettazione illuminotecnica, finalizzata tanto al comfort visivo quanto al benessere fisiologico e all’efficienza cognitiva

Computational Fluid Dynamic Modelling of Thermal Periodic Stabilized Regime in Passive Buildings

The periodic stabilized regime is the condition where the temperature of each point of a certain environment varies following a periodic law. This phenomenon occurs in many practical applications, such as passive or ancient buildings not equipped with Heating, Ventilating and Air Conditioning HVAC systems and located in latitudes where the temperature greatly varies with Earth's daily cycles. Despite that, the study of transient phenomena is often simplified, i.e., considering negligible the thermal response of the indoor microclimate. An exact solution to enclosures whose microclimate is free to evolve under a periodic stabilized regime does not exist nowadays, also from an analytical point of view. The aim of this study is to parametrically analyze the thermal variations inside a room when a transient periodic temperature is applied on one side. The phenomenon has been numerically studied through Computational Fluid Dynamics (CFD) and analytically validated using a function that reproduces the daily variation of the outdoor temperature. The results of this research would lay the groundwork to develop analytical correlations to solve and predict the thermal behavior of environments subject to a periodic stabilized regime

Influence of insulating materials on green building rating system results

This paper analyzes the impact of a change in the thermal insulating material on both the energy and environmental performance of a building, evaluated through two different green building assessment methods: Leadership in Energy and Environmental Design (LEED) and Istituto per l'innovazione e Trasparenza degli Appalti e la Compatibilità Ambientale (ITACA). LEED is one of the most qualified rating systems at an international level; it assesses building sustainability thanks to a point-based system where credits are divided into six different categories. One of these is fully related to building materials. The ITACA procedure derives from the international evaluation system Sustainable Building Tool (SBTool), modified according to the Italian context. In the region of Umbria, ITACA certification is composed of 20 technical sheets, which are classified into five macro-areas. The analysis was developed on a residential building located in the central Italy. It was built taking into account the principles of sustainability as far as both structural and technical solutions are concerned. In order to evaluate the influence of thermal insulating material, different configurations of the envelope were considered, replacing the original material (glass wool) with a synthetic one (expanded polystyrene, EPS) and two natural materials (wood fiber and kenaf). The study aims to highlight how the materials characteristics can affect building energy and environmental performance and to point out the different approaches of the analyzed protocols