Franco Cotana

Production of nanocrystalline cellulose from lignocellulosic biomass: Technology and applications

The use of renewables materials for industrial applications is becoming impellent due to the increasing demand of alternatives to scarce and unrenewable petroleum supplies. In this regard, nanocrystalline cellulose, NCC, derived from cellulose, the most abundant biopolymer, is one of the most promising materials. NCC has unique features, interesting for the development of new materials: the abundance of the source cellulose, its renewability and environmentally benign nature, its mechanical properties and its nano-scaled dimensions open a wide range of possible properties to be discovered. One of the most promising uses of NCC is in polymer matrix nanocomposites, because it can provide a significant reinforcement. This review provides an overview on this emerging nanomaterial, focusing on extraction procedures, especially from lignocellulosic biomass, and on technological developments and applications of NCC-based materials. Challenges and future opportunities of NCC-based materials will be are discussed as well as obstacles remaining for their large use.

Active cool roof effect: impact of cool roofs on cooling system efficiency

Cool roofs represent an acknowledged, relatively simple, and low-cost strategy to reduce cooling energy demand of buildings and mitigate urban heat island phenomena. The purpose of this paper is to study the coupled passive–active effect produced by such a technology, where the active effect consists of the cool roof capability to decrease the suction air temperature of heat pump external units, when these units are located over the roof. This “cooling” benefit produces an extra increase of the energy performance of the heat pump in cooling mode, given that it produces the decrease of the temperature lift between the source and the output. In order to study this twofold effect, an industrial building with an office area located in Rome, Italy, was continuously monitored in summer 2012. The main results showed that the cool roof allows to decrease the roof overheating up to 20°C. The office indoor air temperature also decreased, even if the same set-point temperature was kept constant during the whole campaign. The energy requirement for cooling decreased by about 34%. In order to investigate the “active” contribution, suction air temperature was monitored and a new simple analytical model is proposed in order to estimate the cool roof active effect.

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.

A New Geometry High Performance Small Power MCFC

Molten Carbonate Fuel Cells (MCFC) operate at temperatures ranging from 600 to 700°C; high temperatures allow to obtain low internal losses with large benefits in terms of generated electric power. A new geometry for small sized MCFCs is proposed in this paper. Cell thermofluidodynamic performance has been analyzed through a numerical code. Simulation results verified the suitability of the proposed cell design solutions. A stack consisting of three elementary units has been created in order to experimentally evaluate the proposed cell performance. [DOI: 10.1115/1.1782924]

Evaluation and Optimization of an Innovative Low-Cost Photovoltaic Solar Concentrator

Many researches showed that the cost of the energy produced by photovoltaic (PV) concentrators is strongly reduced with respect to flat panels, especially in those countries that have a high solar irradiation. The cost drop comes from the reduction of the expensive high-efficiency photovoltaic surface through the use of optical concentrators of the solar radiation. In this paper, an experimental innovative PV low-concentration system is analysed. Numerical simulations were performed to determine the possible reasons of energy losses in the prototype, primarily due to geometrical factors. In particular, the effect of the shadows produced from the mirrors on the prototype performances was analysed: shadows are often neglected in the design phase of such systems. The study demonstrates that shadows may affect the performances of a hypothetical optimized PV low-concentration system up to 15%. Finally, an economical evaluation was carried out comparing the proposed optimized system to a traditional flat PV panel.

Thermal behaviour and kinetic study of the olive oil production chain residues and their mixtures during co-combustion.

The kinetic behaviour of olive tree pruning (PR), two- (2PH) and three-phase (3PH) olive pomace and their blends was investigated under combustion condition using thermogravimetric analysis. PR was blended with 2PH and 3PH at different ratios (25:75, 50:50 and 75:25) and tested in the temperature range from ambient to 1000°C in order to evaluate the co-combustion behaviour. Results showed that the thermal degradation of all samples can be divided into three regions (drying, devolatilisation, char oxidation) with different combustion properties, depending on the percentage of PR. Significant interaction was detected between the fuels, and reactivity of 2PH and 3PH was improved upon blending with PR. The iso-conversional methods, Ozawa-Flynn-Wall and Vyazovkin, were employed for the kinetic analysis of the oxidation process. The results revealed that the activation energy of PR was higher than the one of 2PH and 3PH, and the minimum value was obtained for 25PR752PH sample.

Cool roofs as a strategy to tackle global warming: economical and technical opportunities

There is a growing consensus within the scientific community that the Earths climate system is unequivocally warming and it is very likely (according to the formal uncertainty language used in the AR4, the term “very likely” refers to >90% assessed probability of occurrence) due to the increase in anthropogenic greenhouse gas concentrations. Urgent solutions need to be adopted, which are environmentally sustainable, in order to tackle global warming in the short term. At present, the most accredited global warming mitigation methods are represented by the emissions reduction technologies. Such technologies include energy from renewable sources such as solar and wind. A potential alternative is to modify the Earths albedo by reflective surfaces (pavements and roofs), which are already employed to reduce building energy consumption and to mitigate heat island effects. In this paper a procedure is proposed which evaluates the influence of changes in the Earths albedo on the Earths temperature and, as a consequence, quantifies the high albedo surface size required to compensate or offset global warming from changes in CO2. Additionally, a technical-economical comparison is carried out here between the proposed albedo system and the main technologies for the production of electric and thermal energy from renewable sources in order to evaluate its effectiveness in terms of cost of carbon dioxide equivalent (CO2eq) emission reduction.

Traditional and Innovative Materials for Energy Efficiency in Buildings

This chapter shows the most recent and innovative contributions and research trends arounbd the wide issue of energy efficiency in buildings by means of passive techniques, such as new effective materials for building envelope optimization. In particular, cool materials will be dealt with by considering their capability to keep a surface cooler than other solutions when exposed to solar radiation. Then multifunctional materials such as thermal and acoustic insulation panels will be analyzed. Finbally, natural and biobased solutions for energy saving will be investigated. Each one of these topics will be studied by elaborating a first general assessment of each technique and then by analyzing the most recent contributions and research trends in order to provide a wide perspective of the question that is going to be addressed in this chapter.

Simulating the Thermal-Energy Performance of Buildings at the Urban Scale: Evaluation of Inter-Building Effects in Different Urban Configurations

Abstract The reduction of the energy use of buildings at the urban scale represents a key research and design topic with the purpose of developing specific methods for saving energy in buildings. These methods are often focused on the analysis of building thermal-energy behavior by considering the building as a stand-alone object. In this perspective, the thermal-energy behavior of two buildings in New York City is evaluated in this paper with varying urban contexts, in order to evaluate the Inter-Building Effect (IBE). The IBE analysis shows that the inaccuracy in neglecting the urban context in building modeling varies from 9.6 percent, to 71.9 percent. These results confirm that, in order to make accurate predictions about building thermal-energy performance in real urban contexts through dynamic simulation, the interaction between the building and the urban surrounding should be taken into account, in particular in dense urban areas.

A Cylindrical Molten Carbonate Fuel Cell Supplied with Landfill Biogas

A small size cylindrical Molten Carbonate Fuel Cell stack was installed at Giugliano landfill in Italy. The stack was constituted by 16-cells with a 300 W nominal power. Preliminary tests were performed in order to verify the possibility to supply the stack by the landfill biogas, characterized by low methane content (32%). Results showed that the proposed plant is able to correctly operate also when supplied with low methane content biogas.