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An energy-balanced analytic model for urban heat canyons: comparison with experimental data

The climate of high-density urban areas is often affected by the air temperature increase with respect to the neighbouring country-side. This phenomenon, known as the urban heat island (UHI) effect, is strongly influenced by the solar reflectance of building envelope and coating materials, and it is enhanced in the presence of built patterns that trap the solar and anthropogenic energy, usually referred to as urban heat canyons. An original method to quantify the urban heat canyon effect as a function of meteorological conditions, geometry, and surface properties is proposed. The goal is to provide a reliable tool to estimate the effect of the reflective properties of the canyon surfaces on the urban environment, in order to guide the choice of effective solution towards the UHI mitigation. An energy-balanced analytic model, specifically set-up to predict surface temperatures inside an urban canyon, is applied to a scale test facility located at the University of Perugia, Italy. The test facility is made of two twin arrays resembling urban canyons with different aspect ratios. Each canyon can be equipped with reflective films to quantify the radiative exchange variation. Preliminary results from the experimental facility monitoring and the analytic model validation are presented.

Environmental impact of an Italian wine bottle: Carbon and water footprint assessment

The food sector represents one of the major impacting sectors from an environmental point of view and, among all the products, wine emerges as one of the most studied by the literature. Single-issue approaches are commonly used, but a more comprehensive analysis is desirable, since a single indicator does not properly track the pressure on the environment. This paper presents a combined carbon and water footprint assessment, with a cradle to grave approach, for a protected designation of origin Italian red wine, and suggests a correlation among the two indicators across the life cycle phases. A total CF equal to 1.07±0.09kgCO2eq/bottle and a total WF equal to 580±30l/bottle were calculated for the studied product and a direct proportionality was found between the total CF and the sum of WFgrey(indirect) and WFblue.

Design and monitoring of an innovative geothermal system including an underground heat-storage tank

ABSTRACT The design, implementation, and setup of an innovative layout for geothermal heating and cooling systems are presented. An underground heat-storage tank, used as a thermal flywheel, decouples the utility side of the system (i.e., the heat pump) from the geothermal side (i.e., the boreholes). The innovative layout allows for a more efficient exploitation of the ground energy reservoir and a sensible reduction of investment costs. A pilot system has been realized for a commercial building near the city of Perugia, Italy. The design of the heat-storage tank, the heat exchangers, the monitoring system, and the operation modes were carefully studied. The heating performance monitoring shows that the innovative approach allows for a significant reduction of the ground heat exchangers, hence requiring for fewer and/or shorter boreholes (up to 75%) while still supplying the total energy need. The peak-power demand is covered taking advantage of the high thermal capacity of the water inside the tank, while the reduced-size geothermal boreholes are used with a higher duty cycle to independently provide the total energy need.

Carbon and energy footprint of the hydrate-based biogas upgrading process integrated with CO2 valorization

The present paper aims at assessing the carbon and energy footprint of an energy process, in which the energy excess from intermittent renewable sources is used to produce hydrogen which reacts with the CO2 previously separated from an innovative biogas upgrading process. The process integrates a hydrate-based biogas upgrading section and a CO2 methanation section, to produce biomethane from the biogas enrichment and synthetic methane from the CO2 methanation. Clathrate hydrates are crystalline compounds, formed by gas enclathrated in cages of water molecules and are applied to the selective separation of CO2 from biogas mixtures. Data from the experimental setup were analyzed in order to evaluate the green-house gas emissions (carbon footprint CF) and the primary energy consumption (energy footprint EF) associated to the two sections of the process. The biosynthetic methane production during a single-stage process was 0.962Nm3, obtained mixing 0.830Nm3 of methane-enriched biogas and 0.132Nm3 of synthetic methane. The final volume composition was: 73.82% CH4, 19.47% CO2, 0.67% H2, 1.98% O2, 4.06% N2 and the energy content was 28.0MJ/Nm3. The functional unit is the unitary amount of produced biosynthetic methane in Nm3. Carbon and energy footprints are 0.7081kgCO2eq/Nm3 and 28.55MJ/Nm3, respectively, when the electric energy required by the process is provided by photovoltaic panels. In this scenario, the overall energy efficiency is about 0.82, higher than the worldwide average energy efficiency for fossil methane, which is 0.75.