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Publications

Publications by CPES

2017

An application of a multi-criteria decision support system to assess energy performance of school buildings

Authors
Bernardo, H; Gaspar, A; Antunes, CH;

Publication
CISBAT 2017 INTERNATIONAL CONFERENCEFUTURE BUILDINGS & DISTRICTS - ENERGY EFFICIENCY FROM NANO TO URBAN SCALE

Abstract
This work presents a multi-criteria classification system considering multiple, conflicting and incommensurate evaluation aspects influencing energy efficiency in school buildings. The multi-criteria ELECTRE TRI method is used to classify energy performance of school buildings into categories of merit using the IRIS software. The alternatives under evaluation are assigned to predefined ordered categories according to their absolute performance and not in comparison with the performance of other alternatives. Each alternative is assessed using reference profiles defming the boundaries of the categories in which the alternatives should be sorted. The model was applied using a set of performance indicators obtained in the framework of a research and development project aimed at assessing the energy performance of a sample of Portuguese school buildings. IRIS allowed inferring robust conclusions by indicating the range of categories for each alternative, considering the decision maker's preferences, captured by the parameters of ELECTRE TRI. (C) 2017 The Authors. Published by Elsevier Ltd.

2017

An approach for energy performance and indoor climate assessment in a Portuguese school building

Authors
Bernardo, H; Antunes, CH; Gaspar, A; Pereira, LD; da Silva, MG;

Publication
SUSTAINABLE CITIES AND SOCIETY

Abstract
The main goal of this paper is to present a set of well-defined and structured procedures to establish guidelines for the application of an integrated assessment of energy performance and indoor climate in schools. Increasing the knowledge about how energy is consumed in schools is a way to enhance the awareness of school managers (board of directors) about the importance of improving energy efficiency and reducing energy costs. The proposed methodology helps to identify major energy consuming equipment in school buildings and potential energy conservation measures. The assessment of indoor climate identifies potential corrective measures to problems related to indoor air quality and thermal comfort, also supporting the study of further energy conservation measures associated with ensuring environmental quality. Results of a case study showed that the expected energy consumption reduction is about 11.2% due to a better usage of daylighting and 4.5% due to the reduction of fresh air flow rates, while extending the ventilation operation time. In addition, there is a considerable non-calculated potential for energy savings and improvement of indoor environmental conditions in school buildings, promoting students and teachers productivity and wellbeing.

2017

Evaluation of fault levels and power supply network impedances in 230/400V 50Hz generic distribution systems

Authors
Hernando-Gil, I; Shi, H; Li, F; Djokic, S; Lehtonen, M;

Publication
2017 IEEE Manchester PowerTech

Abstract

2017

Quantification of Additional Reinforcement Cost from Severe Three-Phase Imbalance

Authors
Ma K.; Li R.; Hernando-Gil I.; Li F.;

Publication
IEEE Transactions on Power Systems

Abstract
This letter is an enhancement to our previous paper that quantifies additional reinforcement costs (ARCs) for low-voltage assets under moderate degree of three-phase imbalance. The original formulas cause an overestimation of the ARCs under severe imbalance. This letter first quantifies the threshold of the severe degree of imbalance (DIB), below which the original formulas are applicable. Then, the ARC formulas are extended to account for the whole range of DIB. Case studies demonstrate that when the asset loading level is below 33.3% (50%) for a feeder (a transformer), the DIB never exceeds the threshold and the original ARC formulas are applicable; otherwise, the DIB can exceed the threshold and the extended formulas yield correct ARCs.

2017

Evaluation of Fault Levels and Power Supply Network Impedances in 230/400 v 50 Hz Generic Distribution Systems

Authors
Hernando-Gil I.; Shi H.; Li F.; Djokic S.; Lehtonen M.;

Publication
IEEE Transactions on Power Delivery

Abstract
In this paper, typical strengths, fault levels, and source impedances are thoroughly analyzed and calculated for the study of quality of supply in 230/400 V 50 Hz distribution systems. Considering all the disparity in distribution network design, this study is based on a comprehensive database containing typical arrangements and equipment in U.K./European systems, as well as on fully documented generic network models supplying four residential load subsectors in the U.K., i.e., from metropolitan to rural areas. Thus, this paper proposes an alternative method for determining reference values of network supply impedances and short-circuit fault levels at different points and locations of the medium-to-low voltage distribution system. The aim of this study is to provide a wider range of benchmark values than those stipulated in the IEC 60725 Standard, which only defines a single-reference threshold of public supply impedances for all types of distribution systems and residential customers. In order to assist network operators in the planning and design of their distribution systems, these values are further disaggregated and classified in this paper according to network/demand type.

2017

An improved reliable PSO based parameter extraction method applied to GaN HEMTs for mm-Wave applications

Authors
Hussein A.S.; Jarndal A.H.;

Publication
2017 International Conference on Electrical and Computing Technologies and Applications Icecta 2017

Abstract
An improved and efficient parameter extraction method applied to GaN high electron mobility transistors (HEMTs) is presented. The aim is to extract reliable values for the generally distributed small-signal model to accurately describe the device at mm-wave range. A modified version of hybrid extraction technique combining particle-swarm-optimization and direct fitting has been implemented. S-parameters fitting has been used to validate the model under various bias conditions. The results indicate a very good agreement between model and simulation up to 60 GHz.

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