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Publicações

2019

Analysis of Switch Automation Based on Active Reconfiguration Considering Reliability, Energy Storage Systems, and Variable Renewables

Autores
Santos, SF; Fitiwi, DZ; Cruz, MRM; Santos, C; Catalao, JPS;

Publicação
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS

Abstract
Economic development and changing lifestyles are leading to the extensive use of energy-intensive technologies by consumers. As a result, this has led to a dramatically increased demand for electricity. In addition, the consumers' increasing demand for a more reliable and uninterrupted energy supply is posing enormous challenge for service providers. This necessitates the development of novel solutions that should be at the system operators' disposal, particularly at distribution levels. One way to partly address this concern is by automating distribution systems and equipping them with intelligent technologies-a transformation to smart distribution systems. Such a transformation should improve system reliability and operational efficiency because such systems will be capable of operating and immediately restoring discontinued service to consumers. To facilitate this, it is necessary to replace manual switches by remotely controlled ones, improving the system restoration capability, which is one of the key features of smart grids. This paper presents a new framework to determine the minimal set of switches that have to be replaced or optimally allocated in order to automate the system. This is supported by a sensitivity analysis. Different topologies are also assessed taking into account various reliability indices and power losses in system operation following the system's automation. Such an optimization work is done under a massive integration of renewable energy sources and energy storage systems. All this simultaneously addresses the economic and functional requirements of the automated system, ultimately improving system's reliability. The standard IEEE 119-bus standard system is used as a case study, where different types of loads are considered (residential, commercial, and industrial).

2019

Dissolved Carbon Dioxide Sensing Platform for Freshwater and Saline Water Applications: Characterization and Validation in Aquaculture Environments

Autores
Mendes, JP; Coelho, L; Kovacs, B; de Almeida, JMMM; Pereira, CM; Jorge, PAS; Borges, MT;

Publicação
SENSORS

Abstract
A sensing configuration for the real-time monitoring, detection, and quantification of dissolved carbon dioxide (dCO(2)) was developed for aquaculture and other applications in freshwater and saline water. A chemical sensing membrane, based on a colorimetric indicator, is combined with multimode optical fiber and a dual wavelength light-emitting diode (LED) to measure the dCO(2)-induced absorbance changes in a self-referenced ratiometric scheme. The detection and processing were achieved with an embeded solution having a mini spectrometer and microcontroller. For optrode calibration, chemical standard solutions using sodium carbonate in acid media were used. Preliminary results in a laboratory environment showed sensitivity for small added amounts of CO2 (0.25 mg.L-1). Accuracy and response time were not affected by the type of solution, while precision was affected by salinity. Calibration in freshwater showed a limit of detection (LOD) and a limit of quantification (LOQ) of 1.23 and 1.87 mg.L-1, respectively. Results in saline water (2.5%) showed a LOD and LOQ of 1.05 and 1.16 mg.L-1, respectively. Generally, performance was improved when moving from fresh to saline water. Studies on the dynamics of dissolved CO2 in a recirculating shallow raceway system (SRS+RAS) prototype showed higher precision than the tested commercial sensor. The new sensor is a compact and robust device, and unlike other sensors used in aquaculture, stirring is not required for correct and fast detection. Tests performed showed that this new sensor has a fast accurate detection as well as a strong potential for assessing dCO(2) dynamics in aquaculture applications.

2019

Minha: Large-Scale Distributed Systems Testing Made Practical

Autores
Machado, N; Maia, F; Neves, F; Coelho, F; Pereira, J;

Publicação
OPODIS

Abstract
Testing large-scale distributed system software is still far from practical as the sheer scale needed and the inherent non-determinism make it very expensive to deploy and use realistically large environments, even with cloud computing and state-of-the-art automation. Moreover, observing global states without disturbing the system under test is itself difficult. This is particularly troubling as the gap between distributed algorithms and their implementations can easily introduce subtle bugs that are disclosed only with suitably large scale tests. We address this challenge with Minha, a framework that virtualizes multiple JVM instances in a single JVM, thus simulating a distributed environment where each host runs on a separate machine, accessing dedicated network and CPU resources. The key contributions are the ability to run off-the-shelf concurrent and distributed JVM bytecode programs while at the same time scaling up to thousands of virtual nodes; and enabling global observation within standard software testing frameworks. Our experiments with two distributed systems show the usefulness of Minha in disclosing errors, evaluating global properties, and in scaling tests orders of magnitude with the same hardware resources.

2019

Usability Evaluation of an Educational Robot for STEM Areas

Autores
Barradas, R; Lencastre, JA; Soares, S; Valente, A;

Publicação
CSEDU (2)

Abstract
This article describes the development cycle of an educational robot designed to act as an interdisciplinary teaching tool integrated into the curriculum of STEM areas (Science, Technology, Engineering and Mathematics). We focused on the creation of the alpha version of the prototype and its heuristic evaluation by three experts, with the objective of appraising both usability and potential design problems. After all the issues and suggestions from the experts have been resolved and implemented, a beta version was developed and evaluated in its usability by five representatives of end-users with different age ranges and robotics knowledge. The System Usability Scale score of 92.5 points - Best Imaginable - show a very stable and satisfactory robot, with almost no usability problems detected.

2019

Data management techniques

Autores
Bilas, A; Carretero, J; Cortes, T; Blas, JG; Férez, PG; Papagiannis, A; Queralt, A; Marozzo, F; Saloustros, G; Shoker, A; Talia, D; Trunfio, P;

Publicação
Ultrascale Computing Systems

Abstract

2019

Energy performance of buildings with on-site energy generation and storage - An integrated assessment using dynamic simulation

Autores
Bot, K; Ramos, NMM; Almeida, RMSF; Pereira, PF; Monteiro, C;

Publicação
JOURNAL OF BUILDING ENGINEERING

Abstract
The European Union aims to achieve a nearly zero energy balance in buildings by 2020. The present study takes into consideration the passive systems of the building, energy demand, and energy generated by the on-site photovoltaic and storage system, and how they interact in different scenarios. The study also considers the energy demand from the grid and the surplus of renewable energy. The software EnergyPlus was used and the parametric sensitivity simulation method was applied, taking into account blinds operation, ventilation strategies, HVAC operation schemes and battery storage capacity, in 96 scenarios. The results highlight that there is great variability between the considered scenarios, highlighting the importance of sizing methodologies for the passive systems and the use of optimized home management algorithms. It was found that the use of batteries with higher storage capacity increases the demand-supply from the on-site PV energy but decreases the amount of energy injected into the grid. The design of the PV and battery system based on yearly integrated simulations allows for an optimized solution. This study also emphasizes the importance of knowing the expected occupancy during the design phase, as a significant input to the sizing methodologies of the storage capacity and on-site generation.

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