Solar-assisted integrated biogas solid oxide fuel cell (SOFC) installation in wastewater treatment plant: Energy and economic analysis

A unique cogeneration system integrating a biogas fed Solid Oxide Fuel Cell (SOFC) and a Concentrating Solar Thermal (CST) system for a reference Waste Water Treatment Plant (WWTP) in Italy is proposed. Biogas - which is locally in the WWTP from the anaerobic digestion (AD) of the collected sludge - can be used to produce electricity using SOFC power modules. The thermal power recovered from the SOFC exhaust stream is used to meet part of the digester thermal load. However, the rest heat loads are provided by using the integration with the CST system and an auxiliary boiler. Energy analysis is performed to determine the effect of using the solar heating system on the system performance. Also, the economic performance is evaluated through a cash-flow analysis and the calculation of the Levelized cost of electricity (LCOE). It is observed that installing 300 m2, 700 m2, 1100 m2 of solar collectors could cover 8%, 18% and 30% of total digester heat load, respectively. Results show an overall beneficial effect of the solar installation, both from an energy and economic standpoint of view. For all the scenarios analyzed, the LCOE is lower than the grid electricity price and, with increasing solar integration, the value is further reduced showing that, despite the investment return time, the electricity production during the entire system lifetime is competitive against grid electricity prices

The museum of errors/horrors in Scopus

Recent studies have shown that the Scopus bibliometric databases is probably less accurate than one thinks. As a further evidence of this fact, this paper presents a structured collection of several weird typologies of database errors, which can therefore be classified as horrors. Some of them concern the incorrect indexing of so-called Online-First paper, duplicate publications, and the missing/incorrect indexing of references. A crucial point is that most of these errors could probably be avoided by adopting some basic data checking systems. Although this paper does not provide a quantitative and systematic analysis (which will be provided in a future publication), it can be easily understood that these errors can have serious consequences such as: (i) making it difficult or even impossible to retrieve some documents, and (ii) distorting bibliometric indicators/metrics relating to journals, individual scientists or research institutions. Our attention is focused on the Scopus database, although preliminary data show that the Web of Science database is far from being free from these errors. The tone of the paper is deliberately provocative, in order to emphasize the seriousness of these error

Experimental results and strength model identification of pure iridium

Intense and high energy proton beams are impacted with fixed materials (targets) in order to produce new particles and secondary beams at CERN. In some of these targets, the requirement of reaching high yield production of secondary particles points out to the use of high density materials. The interaction of the beam with the atoms and nuclei of these materials produce extremely fast depositions of energy, highly soliciting them from thermo-structural point of view due to subsequent rise of temperature and pressure waves. Iridium is a good candidate material since exhibits very high density, high melting point, good strength and stability at high temperature, and resistance to thermal shock. The main goal of this study is the investigation of the mechanical behaviour at different temperatures and strain-rates in tensile loading condition of pure iridium. A series of tests at room temperature at different strain-rates (from 10-3 s-1 up to 104 s-1) was performed in order to obtain information about strain and strain-rate sensitivity of the material. In addition, a series of tests at different temperatures in both quasistatic and high strain-rate loading conditions was performed in order to obtain information about the thermal softening of the material (from room temperature up to 1250 °C). The experimental data were used to identify a strength model able to predict the material behaviour over wide ranges of variation of the variables of interest

Topology optimization for heat transfer enhancement in Latent Heat Thermal Energy Storage

Performance of a Latent Heat Thermal Energy Storage depends strongly on the spatial layout of high conductive material and phase change material. Previous design studies have explored a limited design space and have rarely taken advantage of any formal optimization approach. This paper presents a topology optimization framework of a Thermal Energy Storage system involving phase change. We solve the Stefan problem for solidification with a fixed grid finite element method based on the apparent heat capacity technique, while the topology optimization problem is formulated using a density-based method. This approach allows to identify design trends that have been rarely investigated in the past. Firstly, we explore the inherent trade-off between discharged energy and required time for complete discharge. We obtain very different designs and highly varying performances at selected Pareto points. Secondly, by comparing results obtained in two and three dimensions we observe that 3D designs allow superior performances by presenting features that are not apparent in 2D. Thirdly, we propose a formulation of the design problem that yields a nearly constant thermal power output during the entire discharge process. If the maximum discharge time is sufficiently large, the optimized design presents fins that are disconnected from the internal tube

Flow simulations in porous media with immersed intersecting fractures

A novel approach for fully 3D flow simulations in porous media with immersed networks of fractures is presented. The method is based on the discrete fracture and matrix model, in which fractures are represented as two-dimensional objects in a three-dimensional porous matrix. The problem, written in primal formulation on both the fractures and the porous matrix, is solved resorting to the constrained minimization of a properly designed cost functional that expresses the matching conditions at fracture-fracture and fracture-matrix interfaces. The method, originally conceived for intricate fracture networks in impervious rock matrices, is here extended to fractures in a porous permeable rock matrix. The purpose of the optimization approach is to allow for an easy meshing process, independent of the geometrical complexity of the domain, and for a robust and efficient resolution tool, relying on a strong parallelism. The present work is devoted to the presentation of the new method and of its applicability to flow simulations in poro-fractured domains

Carbon recovery and re-utilization (CRR) from the exhaust of a solid oxide fuel cell (SOFC): Analysis through a proof-of-concept

In the context of the paradigm of Carbon Recovery and Re-utilization (or CRR), this work investigates the role of electrochemical generators (such as high-temperature fuel cells) to perform CRR as a practical secondary effect. In fact, the solid oxide fuel cell (SOFC) operating principle is inherently beneficial toward CO2 separation from the exhaust gas since the fuel is electrochemically oxidized resulting in no N2 mixing at the anode (fuel) electrode. An oxy-combustor downstream the fuel cell will complete the residual fuel (mostly H2 and CO) oxidation to yield a stream that contains only H2O and CO2. After water condensation and further drying, the captured CO2 is fed to a photobioreactor that can fix carbon into microalgae. In this work, results of the first SOFC-based poly-generation system with complete CO2 recovery in the form of fast-growing biomass (micro-algae) are presented, as developed in the EU-funded project SOFCOM (GA 278798, www.sofcom.eu). The overall plant layout is described, and results on the performance of the proof-of-concept plant units are provided

Robust and Efficient Globally-Asynchronous Locally-Synchronous (GALS) digital design

Process and operating condition variability creates a huge problem for current and future digital integrated circuits, because it forces them to operate at a speed, voltage and hence power and energy consumption which is very far from the optimum. System on Chip (SoC) architectures are born to meet some of the microelectronic trends. A single integrated chip contains an entire system with one or more central processors, several other chip-set, memories, and interfaces. The bottleneck of this approach are the interconnections between the various components. A global asynchronous communication is particularly suitable for this purpose because it removes most of the variable delays of the synchronous operation. At the same time, there is always the need to optimize the speed or power consumption of the computation and the Razor approach has been built for this purpose (trying to go below the synchronous safe operation). So the goal of my work was to implement a new Globally-Asynchronous Locally-Synchronous (GALS) architecture that combines Safe Razor modules connected by flexible asynchronous communication channels. In such architecture, both computation and communication are executed without the margins required by the synchronous worst-case methodology achieving better performance. The thesis makes two contributions to the state of the art: 1. Safe-Razor: a metastability-robust adaptive clocking inside each synchronous GALS module. 2. M-of-N PID code: an efficient Delay-Insensitive (DI) protocol for the asynchronous communication between the GALS module

Large-deflection and post-buckling analyses of laminated composite beams by Carrera Unified Formulation

The Carrera Unified Formulation (CUF) was recently extended to deal with the geometric nonlinear analysis of solid cross-section and thin-walled metallic beams (Pagani and Carrera, 2017). The promising results provided enough confidence for exploring the capabilities of that methodology when dealing with large displacements and post-buckling response of composite laminated beams, which is the subject of the present work. Accordingly, by employing CUF, governing nonlinear equations of low- to higher-order beam theories for laminated beams are expressed in this paper as degenerated cases of the three-dimensional elasticity equilibrium via an appropriate index notation. In detail, although the provided equations are valid for any one-dimensional structural theory in a unified sense, layer-wise kinematics are employed in this paper through the use of Lagrange polynomial expansions of the primary mechanical variables. The principle of virtual work and a finite element approximation are used to formulate the governing equations in a total Lagrangian manner, whereas a Newton-Raphson linearization scheme along with a path-following method based on the arc-length constraint is employed to solve the geometrically nonlinear problem. Several numerical assessments are proposed, including post-buckling of symmetric cross-ply beams and large displacement analysis of asymmetric laminates under flexural and compression loadings