1,720,981 research outputs found
Calculation of the incidence angle modifier of a Linear Fresnel Collector: The proposed declination and zenith angle model compared to the biaxial factored approach
No full textSince their first appearance as a contribution by Professor Francia at the University of Genova, Italy, the Linear Fresnel Collectors (LFC) demonstrated to be an engineering efficient technology for medium to high temperature solar applications. The strength of the LFC concept is related to the simple mirror motion law, to the compactness of the mirror fields (power to land surface ratios), to the lowest resistance to wind, to the system intrinsic scalability. To perform reliable LCOE analyses, robust performance simulation tools are needed. The Authors developed to this aim a 3D ray-tracing model, able to account for shading, blocking, and end effects as a function of LFC geometry, including primary and secondary mirror curvatures. In this paper, a new approach is implemented to reduce huge yearly ray-tracing datasets and provide very compact analytical equations for fast hourly performance simulations. The present model introduces new Incidence Angle Modifier (IAM) correlations based on the declination and zenith angles. The new model demonstrated to fit subhourly 3D ray-tracing data all year long with an overall error lower than 1.5%, well below the best IAM factored models here compared as a general criticism to the biaxial factored approach related to Fresnel applications. (C) 2021 Elsevier Ltd. All rights reserved
Solar Fresnel modelling, geometry enhancement and 3D ray tracing analysis devoted to different energy efficiency definitions and applied to a real facility
No full textDespite their few installations, Linear Fresnel Collectors (LFC) represent a very promising technology for efficient solar energy exploitation at medium to high temperatures thanks to their lowest land area per electric energy ratio. Their first appearance was in the ’60, thanks to Professor Giovanni Francia realizations at the University of Genova, Italy. This research aims to determine the performance of a LFC and perform parametric studies through 3D ray-tracing simulations. The in-house developed code accounts for all geometrical parameters of the mirrors and receiver assembly, including mirror dimensions, curvature and distance, primary mirror optical errors, receiver aperture area and elevation, secondary mirror compound parabolic shape. The present study includes a detailed investigation on shading, blocking and end effect issues while introducing 6 different different optical and energy efficiency definitions. A parametric analysis is applied to the distance between mirrors and the receiver height. After the code validation against Tonatiuh, the calculations are performed to analyse in details the performance of a real LFC plant in Morocco. The peak optical efficiency of the test case plant has been estimated up to 87% but it is demonstrated the selection of the efficiency definition is crucial for performing successful geometry optimizations
The MAKE-IT project: Manufacturing Agents in a Knowledge-based Environment driven by Internet Technologies
No full textMAKE-IT (Manufacturing Agents in a Knowledge-based Environment driven by Internet Technologies) is a research project whose objective is the definition and the implementation of "small" software architectures that can be taken into account as agents - which can perform simple rule-based actions while performing a quite heavy and complex coordination. The main field of application of the MAKE-IT agents is the workflow management of information in small or medium-sized manufacturing enterprises, specifically when their information system is based on the Microsoft Windows architecture
SKED: An Integrated Decision Support System For Scheduling Problems
No full textThe aim of the decision support system SKED described in this paper is to provide a tool for automatic and manual scheduling. The scheduling model dealt with is characteristic of a large class of situations in manufacturing environments. The system utilizes a scheduler module based on a heuristic event-driven approach to find feasible solutions to the problem instances. Two modules allow the user to manage information about problems, and to examine and modify their solutions by means of an highly interactive graphical interface
The effects of subgingival irrigation with antimicrobial agents on periodontal disease
No full textThis report evaluates the role of local pharmacotherapy by subgingival irrigation to enhance clinical and microbiological periodontal status. This kind of chemical therapy is not a substitute to scaling and root planing, but possibly could increase its beneficial effects
Laser in periodontology: theoretical-experimental approach. 1. The laser system: definition, function, classification
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Reduced scale experimental modelling of distributed thermal response tests for the estimation of the ground thermal conductivity
No full textThe knowledge of the ground thermal properties, and in particular the ground thermal conductivity is fundamental for the correct sizing of the Ground Coupled Heat Pump (GCHP) plant. The Thermal Response Test (TRT) is the most used experimental technique for estimating the ground thermal conductivity. This paper presents an experimental setup aimed to realise a suitable scale prototype of the real borehole heat exchanger (BHE) and the surrounding ground for reduced scale TRT experiments. The scaled ground volume is realised with a slate block. Numerical analyses were carried out to correctly determine suitable geometric and operational parameters for the present setup. The scaled heat exchanger, inserted into the block, is created with additive technology (3D printer) and equipped with a central electrical heater along its entire depth and with temperature sensors at different radial distances and depths. Present measurements highlight the possibility to reliably perform a TRT experiment and to estimate the slate/ground thermal conductivity with an agreement of about +12% with respect to measurements provided by a standard commercial conductivity meter on proper cylindrical samples of the same material and onto 10 different portions of the slate block
Simulation and design of a large thermal storage system: Real data analysis of a smart polygeneration micro grid system
No full textThe Smart Polygeneration Microgrid (SPM) at the Savona Campus of the University of Genoa consists of several renewable and traditional electrical and thermal generating units integrated with electric batteries; buildings and facilities are connected by an electrical grid and a district heating network. Thermal and electrical power flows are managed by a proper Energy Management System (EMS) which includes models for all the SPM components ensuring operational costs minimization in compliance with networks constraints. The present study focuses on the integration of a thermal energy storage (TS) system in the SPM: to this aim, a new thermal storage model based on a stepped two-zone approach has been built inside the dynamic EMS solver. The TS is conceived for recovering additional heat from two 65kWel cogenerative gas turbines (CGT), thus minimizing the operation time of the backup gas heaters (GH): the analysis is aimed at inferring the best TS size in terms of different key parameters, expressed through properly defined economic and energy criteria, including overall energy consumption, reduced greenhouse emissions, minimum payback period. The model is applied to energy demand data (heat and electricity) as measured at 15 min time steps along 2 years. The present dynamic analysis shows that an optimized size TS based on sensible heat can increase the CGT operation hours up to 34% yearly and reduce the equivalent CO2 emissions by 4%
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