1,720,972 research outputs found
High-efficiency cogeneration systems for the food industry
No full textThe combined production of electricity and heat is a promising solution when energy inputs, whether fossil or renewable, are to be minimised and can be also economically rewarding if heat and electricity are produced through high efficiency processes. In this framework, featuring a large thermal and electric demand, the industry sector has seen widespread adoption of cogeneration systems to produce process heat/cool along with electricity. Among the variety of areas to be potentially conveniently matched to cogeneration applications, this study focuses on the food industry based on a collection of data derived from an extensive experimental campaign in a facility specialised in confectionery products and presently served by a combustion engine-based cogeneration unit. In the paper, a comparative analysis is conducted with the help of GateCycle software: CHP technologies based on gas turbine and steam power plant with both condensing and backpressure turbine are considered and properly designed as alternatives. The simulation of the energy flows allows for the estimate of specially defined performance indicators referring to relevant energy, economic and environmental quantities. Results display that, among the possible alternatives, the adoption of a 1.69 MW gas turbine-based cogeneration unit would perform better from an energy, environmental and economic perspective, given the favourable indicators it shows
Selection of metal hydrides for a thermal energy storage device to support low-temperature concentrating solar power plants
No full textMetal hydrides have become more and more significant both as hydrogen storage devices and as basic elements in energy conversion systems. Besides the well-known rare earth hydrides, magnesium alloys are very promising in the field of thermal energy storage for concentrating solar power plants. There is interest in analysing the performances of such materials in this context; for this purpose, a numerical model to describe hydrogen absorption and desorption processes of a metal hydride has been connected to a model elaborated with the help of Cycle-Tempo software to simulate a CSP plant operation. The integration of this plant with four metal hydride systems, based on the combination of two low-temperature hydrides (LaNi5, LaNi4.8Al0.2) and two high-temperature hydrides (Mg, Mg2Ni) has been studied. The investigation has taken into account CSP overall performances, transfer surfaces and storage efficiencies, to determine the feasibility of designed plants. Results show that the selection of the optimal hydrides must take into account hydride operation temperatures, reaction enthalpies, storage capacities and kinetic compatibility. In the light of the calculated parameters, a solar ORC plant using R134a as the working fluid is a valuable choice if matched to a storage system composed of LaNi5 and Mg2Ni hydrides
High temperature metal hydrides for energy systems Part B: Comparison between high and low temperature metal hydride reservoirs
No full textImpact and costs of proposed scenarios for power sector decarbonisation: An Italian case study
Full text linkIn the face of ever more ambitious global energy challenges, the European Union has set striving climate targets for 2030, planning to increase renewable energy penetration in the electricity generation as a key measure towards a clean energy transition. To respond to the challenge of keeping the increase in power sector costs, that inevitably arises when a profound reconfiguration of the electricity generation sector is expected, to the lowest possible, this paper aims to quantify the economic burden associated with the reduction of direct CO2 emissions through a comparative assessment of various alternatives proposed for 2030 ranked in terms of their cost-effectiveness. A sensitivity analysis is also applied to the main economic and energy parameters that make up CO2 mitigation costs to include those uncertainties that characterise future projections. The impact of electricity generation shares on CO2 mitigation costs is assessed thus providing a basis for the definition of alternative configurations for the Italian electricity sector capable to achieve the desired environmental performance with a limited economic impact. Finally, results reveal that those scenarios based largely on natural gas and solar source are characterized by high mitigation costs, while energy efficiency is essential for a virtuous and clean electricity sector along with the use of all available sources in appropriate shares, both renewable and non-renewable, to pursue the highest environmental objectives in a cost-effective manner. Although related to the Italian case, the methodology provided in this study can be applied to any other electricity sector to ultimately evaluate the economic burden arising from possible different configurations
An innovative oxygen production technology for advanced IGCC power plants
No full textIntegrated Gasification Combined Cycle (IGCC) power plants represent one of the most appealing options to produce electricity from coal with interesting plant efficiency and low environmental impact. Usually, these power plants are equipped with oxygen-blown gasifiers which have two main advantages with respect to air-blown reactors: high values of cold gas efficiency and an N2 deprived syngas. In this paper an innovative process is studied: magnetic air separation process. In this process a magnet activates oxygen’s paramagnetic properties to retain oxygen while releasing other gases, allowing oxygen to be captured. Magnetic field gradient interaction creates body force on oxygen and traps oxygen while allowing nitrogen to continue freely; enriched oxygen is drawn from the domain during off state. According to the technical literature, the main targets for this process are: lower cost than currently-used cryogenic separation systems; continuous high yield oxygen separation from air (99% pure O2) for feeding a coal gasification system. One of the advantages of the magnetic separation method in comparison with other separation technologies is a significant reduction of specific energy consumption for the production of oxygen. In fact, the only energy needed to power the process is the energy for the generation of the magnetic field and for the pumping of the gases. The aim of this paper is also to compare three different oxygen production technologies for oxidant supply to the gasification island. An IGCC power plant has been modelled considering: (i) a cryogenic distillation Air Separation Unit (ASU) based on a pumped liquid oxygen cycle; (ii) an innovative oxygen separation system based on open gradient magnetic field (magn-AS, magnetic air separation). An overall heat and material balance has been estimated to evaluate plant performances and compare the two options; the thermodynamic analysis shows a promising improvement of the overall plant performance for the IGCC power plants equipped with these innovative technologies nonetheless several key issues deserve a more in depth analysis to assess the real potentialities of these technologies
High temperature metal hydrides for energy systems Part A: Numerical model validation and calibration
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
High-Efficiency Cogeneration Systems: The Case of the Paper Industry in Italy
Full text linkIn January 2011, the introduction of high-efficiency cogeneration in Europe radically modified the incentive scheme for combined heat and power (CHP) plants. Since then, the techno-economic feasibility of new cogeneration plants in different areas of application (industry, service, residential, etc.), along with the definition of their optimal operation, have inevitably undergone a radical change. In particular, with reference to the Italian case and according to the most recent ministerial guidelines following the new EU regulation, in the event that cogeneration power plants do not reach an established value in terms of overall efficiency, their operation has to be split into a CHP and a non-CHP portion with incentives proportional to the energy quantities pertaining to the CHP portion only. In the framework of high-efficiency cogeneration, the present study compares different CHP solutions to be coupled with the paper industry that, among all the industrial processes, appears to be the best suited for cogeneration applications. With reference to this particular industrial reality, energy, environmental, and economic performance parameters have been defined, analysed, and compared with the help of GateCycle software. Among the proposed CHP alternatives, results show that gas turbines are the most appropriate technology for paper industry processes
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