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The empirical literature is very far from any consensus about the appropriate model for oil price forecasting that should be implemented. Relative to the previous literature, this paper is novel in several respects. First of all, we test and systematically evaluate the ability of several alternative econometric specifications proposed in the literature to capture the dynamics of oil prices. Second, we analyse the effects of different data frequencies on the coefficient estimates and forecasts obtained using each selected econometric specification. Third, we compare different models at different data frequencies on a common sample and common data. Fourth, we evaluate the forecasting performance of each selected model using static forecasts, as well as different measures of forecast errors. Finally, we propose a new class of models which combine the relevant aspects of the financial and structural specifications proposed in the literature (“mixed” models). Our empirical findings suggest that, irrespective of the shape of the loss function, the class of financial models is to be preferred to time series models. Both financial and time series models are better than mixed and structural models. Results of the Diebold and Mariano test are not conclusive, for the loss differential seems to be statistically insignificant in the large majority of cases. Although the random walk model is not statistically outperformed by any of the alternative models, the empirical findings seem to suggest that theoretically well-grounded financial models are valid instruments for producing accurate forecasts of the WTI spot price.

Recent problems about fossil fuels and environmental pollution carried to an even great interest about alternative energy sources and green-energy. Conversion of biomass in energy through biochemical and thermochemical process is one of the most promising and sustainable solution and, among thermochemical processes, pyrolysis is one of the most investigated. Different setting of parameters allow obtaining various types of pyrolysis processes, resulting in a different distribution in product yield. Before designing the simulation, Authors collected some literature data about existing biomass pyrolysis plant and products obtained through different kind of this process. Layout of simulation is based on a pilot-plant located in Caltagirone (Sicily). The simulation is developed in this paper through CHEMCAD software. The work has two aims: 1. Try to enhance percentage of bio-oil production modifying operative parameter; 2. Give a preliminary parameters and results to improve the process in a real plant. Authors show a synthesis of real pyrolysis plant showing type, steam and dimension of biomass and describing operative parameters as heating rate, residence time and maximum temperature reached during the process. Moreover, there is an overview of the entire production cycle, with a description of equipment such as type of reactor, heat exchangers and equipment of gas washing section, until obtaining of final products. Process is simulated in CHEMCAD through a K-Reactor block able to reproduce the reaction that occurs during pyrolysis. After products are discharged from the reactor, solid particles are collected in a tank whereas gas fraction carry on towards the other section of the plant to be treated. Through gas washing section and cooling process, condensable fraction is obtained and liquid phase is separated from gaseous fraction. To check reliability of results, the percentages of three products are compared with the ones collected through literature researches and there is a matching between them. Proceedings of the 26th European Biomass Conference and Exhibition, 14-17 May 2018, Copenhagen, Denmark, pp. 1131-1136

Abstract Solar radiation can be considered as one of the most suitable energy source to be used for cooking food. It is therefore important to promote advancement in solar cooking systems, in particular as concerns their efficiency and cooking times. In this work, we designed, realized and tested a novel low-cost solar cooker that uses a high-performance light-concentrating Fresnel lens, which is able to concentrate onto a small focal area a large amount of solar radiation. The radiation is then reflected by a mirror towards a cooking surface, where a pot can be located. The cooker has a geometrical concentration ratio of 40.97. In order to characterize the thermal performance of the cooker, we carried out several outdoor tests with a dedicated test setup, using water and silicone oil as absorbing media. Respect to other solar cookers, results show that the proposed cooker is able to reach high temperatures with good efficiency and reduced heating times: 3 kg of water can reach 90 °C in around 30 min, while 3 kg of silicone oil can be taken from 40 to 170 °C in less than one hour.

AbstractCombustion instabilities represent a long known problem in combustion technology. The environment-friendly lean premixed gas turbines exhibit an increased risk of occurrence of thermo-acoustically induced combustion oscillations. In the present work the stability of a lean premixed swirl-stabilized combustor, experimentally studied at Technische Universität of Munich, has been investigated. The complex interaction between the system acoustics and the turbulent swirling flame is studied using unsteady CFD simulations with Flamelet-Generated Manifolds combustion model. Results were validated against experimental data. Perturbations are introduced in the system imposing a broadband excitation as inlet boundary condition. The flame response to the perturbation is then computed and described exploiting system identification techniques. The identified Flame Transfer Function (FTF) shows quantitative agreement with experiment for amplitude and phase, especially for the low frequency range. At higher frequencies the phase prediction slightly deteriorates while the gain is still well described. The obtained results are implemented into a finite element model of the combustor in order to analyze the stability of the system. Results are compared with available experimental data showing a satisfactory agreement. The advantage introduced by a more sophisticated model for FTF is further evidenced comparing the results with those obtained with analytical formulation found in literature.

Abstract The environmental concerns due to global warming are pushing A/C industries to new eco-friendly refrigerants in several fields. In this paper a model to simulate the dynamic evolution of the temperature inside an air-conditioned high-speed train compartment is presented. The dynamic modeling of both the reversible heat pump unit and the thermal loads of the cabin are presented, including the possibility of adapting the frequency of the compressor and the return air fraction for maintaining the internal comfort conditions. Under different dynamic load conditions (in terms of ambient temperature, solar radiation, train speed, number of passengers) the energy consumptions and the TEWI related to the use of new refrigerants, (like R1234yf and R1234ze), are calculated being the R134a a baseline for comparison.

One of the problems that must be dealt with in a deregulated electricity market is the estimation of the electric power quality of the supply and load. The presence of nonlinear, time-variant, disturbing loads connected to the electric network is responsible for the presence of periodic and nonperiodic disturbances on the line currents and voltages. The availability of indices for the quantification of such disturbances and the assessment of the responsibility for their generation is of utmost importance for the adoption of energy billing policies aimed at discouraging the insertion of uncompensated disturbing loads. This paper analyses a distributed measurement method for the evaluation of a global power quality index for the evaluation of periodic disturbances. The proposed index is validated by means of simulations of the IEEE industrial test system for harmonic modelling and simulation. Some experimental results obtained on a small low-voltage network are also reported.

In Europe, thanks to public subsidy, the production of electricity from anaerobic digestion (AD) of agricultural feedstock has considerably grown and several AD plants were built. When AD plants are concentrated in specific areas (e.g., Northern Italy), increases of feedstock' prices and transport distances can be observed. In this context, as regards low-energy density feedstock, the present research was designed to estimate the influence of the related long-distance transport on the environmental performances of the biogas-to-electricity process. For this purpose the following transport systems were considered: farm trailers and trucks. For small distances (<5 km), the whole plant silage shows the lowest impact; however, when distances increase, silages with higher energy density (even though characterised by lower methane production per hectare) become more environmentally sustainable. The transport by trucks achieves better environmental performances especially for distances greater than 25 km.

Abstract The paper investigates the technical feasibility of an air gasification process of a Solid Recovered Fuel (SRF) obtained from municipal solid waste. A pilot scale bubbling fluidized bed gasifier, having a feedstock capacity of about 70 kg/h and a maximum thermal output of about 400 kW, provided the experimental data: the complete composition of the syngas (including the tar, particulate and acid/basic gas contents), the chemical and physical characterization of the bed material and that of entrained fines collected at the cyclone. The experimental runs were carried out by reaching a condition of thermal and chemical steady state under values of equivalence ratio ranging from 0.25 to 0.33. The results indicate that the selected SRF can be conveniently gasified, yielding a syngas of valuable quality for energy applications. The rather high content of tar in the syngas indicates that the more appropriate plant configuration should be that of a “thermal gasifier”, with the direct combustion of the syngas in a burner ad hoc designed, coupled with an adequate energy-conversion device.