Photovoltaics Noise Barrier: Acoustic and Energetic Study

AbstractIn the light of global warming, renewables such as solar photovoltaics (PV) are important to decrease greenhouse gas emissions. An important issue regarding implementation of solar panels on large scale, is the limited available area. Therefore, it can be interesting to combine PV with alternative applications, as a ways of not requiring “additional” space. One example is a photovoltaic noise barrier (PVNB), where a noise barrier located along a highway or railway is used as substructure for PV modules. Even though PVNB is not a novel concept, in this paper it is studied the best shape of the barrier to optimize the acoustic and energy properties

A model for the evaluation of heat loss from underground cables in non-uniform soil to optimize the system design

With the proliferation of technologies and underground systems, analysis of thermal fields in soil has become a topic of great interest in the developing technology of buried structures. In this work, we have investigated the steady state temperature field (from linear heat sources - buried cable -) in a different type of soil and excavation geometry. In a laboratory, a physical model was built on scale, which reproduces an "undisturbed" area containing a linear thermal source. This scale model was produced for experimental activity. A measuring chain was made to analyze the thermal field in various types of soils, by varying the electrical current through the line source. The physical model was recreated using a finite volume calculation software. Analysis of the different field system configurations were completed and we have studied a model for the improvement of the design method

Analysis of the main anthropogenic sources’ contribution to pollutant emissions in the lazio region, italy

Most cities worldwide suffer from serious air-quality problems, which have received increasing attention in the past decade. The most probable reason for the air-quality problems is the urban population growth, combined with a change in land use due to increasing urban areas. The emission of air pollutants is caused by different anthropogenic processes which can be categorized into the sources of urban traffic, industry, and domestic heating. Dispersion and dilution of air pollutants are strongly influenced by meteorological conditions, especially by wind direction, wind speed, turbulence, and atmospheric stability. With an increasing number of people living in cities, there is the need to examine the correlation between air pollution, local climate, and the effects these changes have on global climate. New interdisciplinary research studies are needed to increase our understanding of the interactions among these aspects. The aim is to analyze the pollutant condition in Rome and the other provinces of the Lazio region with qualitative and quantitative analysis, in order to understand which are the main pollutant sources and what is the correlation of habits of the population on air pollutant emissions

How Cool Pavements and Green Roof Affect Building Energy Performances

The urban heat island effect amplifies the global warming phenomenon with sensible aftermaths on the building energy consumptions. The absence of green areas, open water channels as well as the lack of free unsurfaced spaces creates a sort of urban cap and a heat reflection effect, from the bottom upwards, which persists in the early hours of the night. This heating effect exacerbates the use of air conditioners which, if on one hand helps to cool houses, on the other hand rejects outside hot air hindering the cooling effect of nighttime air. The aim of this study is to analyze the effects of urban heat island mitigation techniques on the building energy performances, such as cool pavements and green roofs. Measured temperatures were used to calibrate a model of a densely populated district in Rome by means of ENVI-met software. It was subsequently carried out an energy analysis through the use of TRNSYS in order to study the energy behavior of a reference building in its urban context in function of the variation of the boundary conditions

Retroreflective materials for building's façades: Experimental characterization and numerical simulations

The urban heat island (UHI) is one of the most studied phenomenon in the last years. Its main effect is associated with the air temperature increase in the cities compared to the rural areas. In order to reduce the air temperature difference between urban and rural areas, several mitigation techniques have been studied. One of the solutions chosen to face the UHI phenomenon consist in the adoption of innovative building envelope materials. Among them, high reflective and cool materials represent a valid solution to achieve this objective. These materials are characterized by high solar reflectance (high ability to reflect solar incident radiation) and high thermal emittance (high ability to emit heat in the infrared wavelength). In the last years, the adoption of a new kind of materials, called retro-reflective materials (RR), used as building envelope coating, is spreading with the purpose of reducing both the façades solar loads and the amount of solar radiation entrapped within the urban fabric. Retro-reflective materials have a particular surface conformation that allows to reflect the solar radiation back in the same direction of the incident radiation. In this case the temperature of the surfaces inside an urban canyon, defined as the space between building that line up continuously on both sides of the street, should have lower values compared with the case with common construction materials. Consequently, also the air temperature inside the urban canyon have low values with significant advantages on outdoor thermal comfort and on building thermal energy demands. Usually, most of the building energy simulation tools consider construction material with a constant and perfectly diffusive solar reflectance. For this reason it is very hard to simulate retro-reflective materials behaviour, since they present an angular dependence of their optical-radiative response. In this work the directional dependence of solar reflectance of a retro-reflective sample material is investigated with the main purpose to assess its impact on façades solar loads and on the building thermal energy demands. The directional reflectance was measured with an experimental setup developed at Roma Tre University. A numerical analysis was subsequently carried out to evaluate the differences in surface solar loads and in thermal energy demands for three Italian cities during cooling and heating season

Solar cooling system for buildings: Thermal analysis of solid absorbents applied in low power adsorption system Energy and Buildings

In the last 50 years the thermal solar panels have been developed mainly for the production of sanitary hot water, but also as an additional source for heating plants. Actually, during the summer season, there is a surplus of thermal energy which can be used as an interesting solution to produce cold by using a simple adsorption system; this can contribute to the air cooling problem with low COP values. The most beneficial adsorbent both for its thermal/physical and low cost is the silica gel, a polymer of silicon dioxide, commonly used for its dehydrating properties, especially in the preservation of electronic material. In this study, a performance thermodynamic balance of a small size system has been made (about 2 kW), adequate to cool an apartment of 70–80 m2 and a TRNSYS simulation has been made to assess in what conformation (surface, storage volume, etc.). A new generation solar power plant is able to guarantee a continuous operation during the summer period. The use of an adsorption system would be favored further in climates in which the solar energy is available, for example in the Arab countries and in some Central Africa countries

Urban Overheating Mitigation Strategies Opportunities: A Case Study of a Square in Rome (Italy)

It is well-known that the occurrence of urban heat islands (UHI) is related to climate change and urbanization. Urban locations experience local overheating throughout the summer, which is uncomfortable and it has a detrimental impact on buildings ability to consume energy. In this study, a methodology was developed to assess the urban heat island effect in a localized urban area and to evaluate the effects of different kind of mitigation strategies. The numerical model was developed using the ENVI_met tool and it was calibrated with weather data and albedo measured inside the examined area and near the simulated domain. The procedure adopted overtaking the limit of the software in reproducing accurate weather conditions without calibration. Finally, combination of extensive mitigation strategies (cool pavements, greenery, grass pavers) with local strategies (shading) were investigated. An experimental and numerical investigation of a square in Rome was exanimated to evaluate the possible solution for mitigating outdoor air temperatures. Results of the paper affirm that an intervention on the pavement albedo and the increase of vegetation inside the square, lead to an improvement of the air thermal conditions. In particular, the application of the grass pavers would lead to the greatest benefits. A maximum decrease in the air temperature of 1.2 °C was obtained through the application of cool material, while the reduction reaches up to 2.88 °C when a grass paver is applied. The improve of the vegetation can bring to a maximum decrease of 1.46 °C, while the use of shading projecting roof allows a reduction up to a maximum of 2.07 °C