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Publications

Publications by João Tomé Saraiva

2005

Long term marginal prices - Solving the revenue reconciliation problem of transmission providers

Authors
Braga, ASD; Saraiva, JT;

Publication
15th Power Systems Computation Conference, PSCC 2005

Abstract
This paper describes a model to perform transmission expansion planning studies together with the computation of Long Term Marginal Prices along the planning horizon. The model includes four criteria and adopts a Simulated Annealing based algorithm to solve the problem. The algorithm also provides Long Term Marginal Prices reflecting both investment and operation costs, thus being able to conveniently address the Revenue Reconciliation Problem that would arise if short-term approaches were used. The paper includes a case study based on the 400/220/150 kV Portuguese transmission system to illustrate the application of the proposed algorithm and highlight its potential.

2012

Transmission Expansion Planning - A Multiyear Dynamic Approach Using a Discrete Evolutionary Particle Swarm Optimization Algorithm

Authors
Rocha, MC; Saraiva, JT;

Publication
2ND EUROPEAN ENERGY CONFERENCE

Abstract
The basic objective of Transmission Expansion Planning (TEP) is to schedule a number of transmission projects along an extended planning horizon minimizing the network construction and operational costs while satisfying the requirement of delivering power safely and reliably to load centres along the horizon. This principle is quite simple, but the complexity of the problem and the impact on society transforms TEP on a challenging issue. This paper describes a new approach to solve the dynamic TEP problem, based on an improved discrete integer version of the Evolutionary Particle Swarm Optimization (EPSO) meta-heuristic algorithm. The paper includes sections describing in detail the EPSO enhanced approach, the mathematical formulation of the TEP problem, including the objective function and the constraints, and a section devoted to the application of the developed approach to this problem. Finally, the use of the developed approach is illustrated using a case study based on the IEEE 24 bus 38 branch test system.

2012

Evaluation of the Impact of Wind Generation on the Electricity Market Prices and on the Profitability of New Wind Investments

Authors
Pereira, AJ; Saraiva, JT;

Publication
2ND EUROPEAN ENERGY CONFERENCE

Abstract
This paper describes a Dynamic Model of the electricity sector that can be used to simulate the evolution of some key variables on the long term, namely the evolution of the electricity price, of the demand and of the capacity factors of the technologies in the generation mix. This model can be used in different ways and by several agents, for instance to estimate the impact on the electricity price of the increasing presence of renewable power stations, namely using wind power and PV systems. In several countries these stations are paid feed-in tariffs with a fixed price but in some cases this scheme is under discussion and there are opinions that payments determined by the market price are more adequate and would bring fewer costs to final consumers. Such a change has to be carefully evaluated given that the presence of renewable stations bidding at an infra marginal price will affect the price itself. The model described in this paper can be used in a profitable way both by governmental agencies when preparing or studying alternative remuneration schemes to renewable stations or by promoters themselves to get more insight to the profitability of their investments, namely if the fixed feed-in tariffs in force in several countries are changed.

2011

Photodynamic Antimicrobial Chemotherapy in Aquaculture: Photoinactivation Studies of Vibrio fischeri

Authors
Alves, E; Faustino, MAF; Tome, JPC; Neves, MGPMS; Tome, AC; Cavaleiro, JAS; Cunha, A; Gomes, NCM; Almeida, A;

Publication
PLOS ONE

Abstract
fischeri Background: Photodynamic antimicrobial chemotherapy (PACT) combines light, a light-absorbing molecule that initiates a photochemical or photophysical reaction, and oxygen. The combined action of these three components originates reactive oxygen species that lead to microorganisms' destruction. The aim was to evaluate the efficiency of PACT on Vibrio fischeri: 1) with buffer solution, varying temperature, pH, salinity and oxygen concentration values; 2) with aquaculture water, to reproduce photoinactivation (PI) conditions in situ. Methodology/Principal Findings: To monitor the PI kinetics, the bioluminescence of V. fischeri was measured during the experiments. A tricationic meso-substituted porphyrin (Tri-Py(+)-Me-PF) was used as photosensitizer (5 mu M in the studies with buffer solution and 10-50 mu M in the studies with aquaculture water); artificial white light (4 mW cm(-2)) and solar irradiation (40 mW cm(-2)) were used as light sources; and the bacterial concentration used for all experiments was approximate to 10(7) CFU mL(-1) (corresponding to a bioluminescence level of 10(5) relative light units - RLU). The variations in pH (6.5-8.5), temperature (10-25 degrees C), salinity (20-40 g L(-1)) and oxygen concentration did not significantly affect the PI of V. fischeri, once in all tested conditions the bioluminescent signal decreased to the detection limit of the method (approximate to 7 log reduction). The assays using aquaculture water showed that the efficiency of the process is affected by the suspended matter. Total PI of V. fischeri in aquaculture water was achieved under solar light in the presence of 20 mu M of Tri-Py(+)-Me-PF. Conclusions/Significance: If PACT is to be used in environmental applications, the matrix containing target microbial communities should be previously characterized in order to establish an efficient protocol having into account the photosensitizer concentration, the light source and the total light dose delivered. The possibility of using solar light in PACT to treat aquaculture water makes this technology cost-effective and attractive.

2002

Solving the Revenue Reconciliation Problem of Distribution Network Providers Using Long-Term Marginal Prices

Authors
Ponce De Leao, MT; Saraiva, JT;

Publication
IEEE Power Engineering Review

Abstract
We describe an integrated methodology to compute long-term marginal prices in distribution networks. Long-term marginal prices are considered the most interesting and economically sound way of allocating network costs to users. Additionally, they inherently deal with the revenue-reconciliation problem, as they generally do not require other large supplementary tariff terms. The proposed methodology uses fuzzy sets to model uncertainties in load forecasts and considers several criteria to guide the identification of solutions. At the end, there is a final decision-making step to select the most adequate expansion plan according to the preferences of the decision-maker.

2011

Discrete evolutionary particle swarm optimization for multiyear transmission expansion planning

Authors
Da Rocha, MC; Saraiva, JT;

Publication
17th Power Systems Computation Conference, PSCC 2011

Abstract
This paper presents a discrete approach, based on an improved integer version of the evolutionary particle swarm optimization (EPSO) algorithm, to solve the dynamic transmission expansion planning (TEP) problem. TEP corresponds to a mixed integer optimization problem that typically aims at identifying a schedule for transmission additions along an extended planning horizon considering operation and investment costs as well as a reliability index to measure the ability the system has to convey electricity from generation to consumers. After detailing the mathematical formulation of the TEP problem, this paper describes the enhanced EPSO algorithm and details its application to the TEP problem. The paper also includes a Case Study based on the IEEE 24 bus / 38 branch system to illustrate the application of the developed procedure.

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