Giorgio Baldinelli

Detection of thermal bridges from thermographic images by means of image processing approximation algorithms

In this paper, we develop a procedure for the detection of the contours of thermal bridges from thermographic images, in order to study the energy performance of buildings. Two main steps of the above method are: the enhancement of the thermographic images by an optimized version of the mathematical algorithm for digital image processing based on the theory of sampling Kantorovich operators, and the application of a suitable thresholding based on the analysis of the histogram of the enhanced thermographic images. Finally, an improvement of the parameter defining the thermal bridge is obtained.

Albedo Retrieval From Multispectral Landsat 8 Observation in Urban Environment: Algorithm Validation by in situ Measurements

The surface albedo in urban environment represents one of the most influencing parameters in the formation of the Urban Heat Island (UHI). Its assessment is therefore strategic to undertake actions for the UHI mitigation: the increase of urban surface reflectivity is an example of cooling strategies increasingly proposed and developed. Spaceborne observations could give a significant contribution supplying albedo maps, and different retrieval algorithms estimating broadband albedo from narrow band reflectivities provided by satellite sensors were proposed and validated in literature. In this study, the accuracy of two well-known retrieval algorithms applied to Landsat 8 OLI reflectivities was assessed in a city of Central Italy (Perugia), selecting test sites having different land cover types. Since the root mean square error of the estimated albedo was quite high (0.07–0.08), a custom retrieval algorithm was developed to evaluate the potential improvement in the narrowband reflectivity-broadband albedo conversion for the case study. This analysis was made possible thanks to an in situ measurement campaign, carried out during the summer months of 2016. The selected sites, having quite homogenous features inside the urban environment, also demonstrated that the albedo values are not significantly affected by the hour of the day, if measurements are taken near noon (variation less than 7%). Spaceborne observations showed once again a powerful tool for monitoring large areas with a quite good spatial resolution (30 m), even if an improvement of the literature albedo retrieval algorithms is required and possible in an urban context.

Transient Heat Transfer in Radiant Floors: A Comparative Analysis between the Lumped Capacitance Method and Infrared Thermography Measurements

The paper presents a simplified mathematical model to describe the transient heat transfer of a radiant floor heating system. A purpose-built test room has been realized to investigate the actual thermal response of a concrete radiant floor in unsteady-state conditions. Beyond the temperature sensors needed for the standard thermal analysis of the heat transfer inside the chamber, the floor temperature was retrieved by means of an infrared thermography camera, in order to validate more precisely the proposed analytical model. The infrared thermography analysis gives interesting information on the floor temperature distribution during the transient, highlighting the pipes’ layout and, if present, inhomogeneous floor zones. The thermal images have been elaborated in order to set and tune the colour map. A portion of the image has been defined for measuring the surface floor temperatures with a previous evaluation of the parameters dealing with the thermographic technique, in order to perform the quantitative survey. The comparison results show that the calculated air and floor temperatures substantially agree with the temperatures measured by infrared thermography and thermocouples, provided that the boundary conditions obtained by the field measurements are strictly reproduced in the lumped capacitance mathematical model. The difference between the two approaches results in values lower than 4 °C during the entire monitoring period: a satisfactory outcome, considering the approximations of the analytical method. The proposed model and its infrared thermography measurements validation represent a useful tool to understand at first sight the floor radiant panels behaviour in the start-up and switch off period, at the aim of gather useful information for the difficult task of their regulation.

Thermal and optical characterization of natural and artificial marble for roof and external floor installations

Some types of buildings need to use certain materials for aesthetic reasons, like churches or mosques. Marble is one of the most common materials usually installed on roofs and floors. The measurement of the thermal and optical characteristics can be useful to understand its behaviour when it is subjected to thermal loads such as solar radiation or high temperature winds. The paper shows a comparison study between natural and artificial types of marble, to investigate the thermal characteristics both in steady-state and transient conditions. Optical properties and surface emissivity were evaluated, in order to calculate the Solar Reflectance Index (SRI); the specific heat, the thermal conductivity and the density were measured to define the thermophysical properties useful for the dynamic analysis. Finally, a test bench was created to check the marble behaviour under known artificial irradiation.

Comparative life cycle assessment of an innovative CSP air-cooled system and conventional condensers

PurposeIn this paper, a first prototype of the innovative modular air-cooled condenser (MACC) proposed under the EU-funded MACCSol research project (Development and verification of a novel modular air cooled condenser for enhanced concentrated solar power generation) is compared with a water-cooled condenser (WCC) and an air-cooled condenser (ACC) in a reference concentrated solar power (CSP) plant. The aim is to evaluate the complete environmental profile of each cooling option and to highlight the differences in terms of impacts.MethodsThe life cycle assessment (LCA) methodology is being used in order to evaluate the life cycle impacts of the three condensers. Firstly, the life cycle impacts are evaluated through the most used methods International Panel on Climate Change (IPCC) 2007 and Ecoindicator 99, using the SimaPro 7.3 software. Secondly, the Ecological Scarcity 2006 approach is used, since it takes into account the main issue of CSP plants: freshwater consumption.Results and discussionResults show that the impact of the MACC is comparable with the ACC one and, in particular, it results quite lower according to all the methods used. Evaluating the severity of local impact through the Ecological Scarcity 2006 method, since the site of operation of the condensers is characterized by medium water stress conditions, the WCC is the cooling option with the highest impact. The best cooling solution, instead, is represented by the MACC: its impact, in fact, results halved compared to WCC. The impact of MACC results significantly affected by the transport activity; therefore, the choice of the transport modes represents a key issue to optimize its life cycle impact.ConclusionsThe LCA analysis carried out definitely shows that the MACC condenser represents a valid alternative to the conventional cooling solutions in regions suitable for CSP plants. In particular, the environmental benefits achievable with the MACC result more evident with the increase of the direct normal irradiance (DNI). The transport activity planning resulted a key issue to further optimize the MACC life cycle impact.

Reflecting panels for radiators in residential buildings: Theoretical analysis of energy performance

The paper deals with the analytical evaluation of energy advantages that could be obtained by inserting a panel made of reflecting material between the wall and radiators used for central heating. As a consequence of the panel installation, a higher percentage of the heat emitted by the radiator remains inside the room to be warmed, diminishing the heat loss through the external wall, thus improving the global efficiency of the entire heating system. The analysis is based on equations that describe the heat exchange by irradiation between the three surfaces: radiator, reflecting panel and inner surface of the external wall; the natural convection with interior room air flow is also taken into account. The study covers three different wall types, with the aim of investigating the influence of the enclosure on the panel performance, and three different climatic zones in Italy (North, Centre and South), to take into account the variation with the external temperature. Results show how the performance of the reflecting panel depends strictly on the insulation level of the external wall facing the radiator; more specifically, efficiency increases when the thermal resistance decreases, reaching energy savings of up to 8.8% in worst insulation conditions. The variability with external temperature conditions is negligible, showing similar values for all the investigated zones.

Albedo and surface temperature relation in urban areas: Analysis with different sensors

Urban areas exhibit a variable land surface temperature (LST) pattern that can be linked to albedo variations. In this work, different spaceborne and airborne sensors have been considered to infer the albedo-LST relation in two urban areas (the cities of Perugia and Aprilia, in Central Italy), in July. Also, an in situ campaign for the measurement of albedo and LST values was carried out in Perugia. The study reveals the expected “inverse” relation albedo-LST (growing LST with decreasing albedo), with surfaces having albedo around 0.10 that can produce an average surface heating greater than 60 °C in July. The observations provide an indication of the global variability of these parameters and their relation in space and time. Furthermore, an analysis at different times can point out an average albedo variation for the same built-up area that could be ascribed to the materials used for new settlements and for existing construction refurbishment

Analysis of Albedo Influence on Surface Urban Heat Island by Spaceborne Detection and Airborne Thermography

Urban environment overheating is gaining growing importance for its consequences on citizens comfort and energy consumption. The surface albedo represents one of the most influencing parameters on the local temperature, therefore, its punctual and large scale detection could give a significant contribution to the urban microclimate assessment. A comparison of satellite data with airborne infrared thermography images is proposed for the city of Florence, starting from temperature analyses and moving to surface albedo assessments. It is shown that, despite the aircraft surveys higher resolution, their area covering limitation, sporadic availability, and high cost make the satellite retrieved data competitive, considering that the current 30 m pixel size of the Landsat images seems to be already suitable for the construction material classification.

A Methodology For Impact Assessment And Acoustic Monitoring Of QuarryActivities

The work presents a methodology to assess the acoustic impact around extractive areas, the validation of which was made through the study of a quarry situated in Perugia (Italy). A preliminary analysis was conducted to locate sensitive areas, to characterize all the various noise sources in the quarry and to determine their contribution to the global acoustic climate. Afterwards, a simulation model for the noise sources in the quarry was implemented: through noise measurements, its reliability was verified. A detailed study on the quarry was therefore carried out, simulating different exercise conditions, corresponding to different noise sources at work in the quarry or to different morphologies during all the quarry life. The model allowed allowed the individualisation of the specific contribution of each source to the global noise, to create different noise maps, to assess the effectiveness of the acoustic mitigation. The reliability of the model was also assessed by a one-year noise monitoring of the area of the quarry.