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Publicações

Publicações por José Villar

2017

Towards a simplified approach for modeling policymaker's decisions in the power sector

Autores
Domenech, S; Villar, J; Campos, FA; Rivier, M;

Publicação
International Conference on the European Energy Market, EEM

Abstract
Plenty of literature exists about how to model liberalized electricity generation markets for the medium and long terms, contributing to the analyze and understanding of those markets, helping companies to plan cost-efficient shortterm market strategies and/or long-term generation capacity investments, and supporting regulators and policymakers in policy decisions and market designs. However, those models do not explicitly consider the impact on investment decisions, mix of technologies and wholesale market prices; of policy decisions but as an external passive input to the model. This paper reviews existing approaches to model policy decisions in such a context, and provides a theoretical modeling framework that explicitly considers the interaction of policymakers' decisions with the generation investment and operation, and customers' response in a liberalized power system. Such kind of model, based on bi-level optimization, contributes to the longterm assessment of some policy decisions in the electricity sector. © 2017 IEEE.

2015

Assessing low voltage network constraints in distributed energy resources planning

Autores
Calvillo, CF; Sanchez Miralles, A; Villar, J;

Publicação
ENERGY

Abstract
Many efforts are being devoted towards achieving optimal planning and operation of DER (Distributed Energy Resources). However, during the planning process, not all relevant thermal constraints of the distribution network are considered; some works claim that they must be taken into account, while others follow the single-node approach. This paper assesses the effects of the distribution network thermal constraints in DER planning, using a deterministic linear programming problem to find the optimal DER planning and operation. Three case studies with different network topologies under several DER implementation scenarios are analyzed. A DC load flow is used to estimate the required network reinforcements to accommodate optimal DER investments, if any. Reinforcement costs are then calculated to assess the net benefit compared to limiting DER investments and operation, according to the network thermal limits. Results suggest that there is no significant economic advantage in limiting DER investments and line flows, compared to reinforcing the low voltage network to allow the larger flows that result from an unconstrained network problem.

2018

Flexibility products and markets: Literature review

Autores
Villar, J; Bessa, R; Matos, M;

Publicação
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
This paper reviews flexibility products and flexibility markets, currently being discussed or designed to help in the operation of power systems under their evolving environment. This evolution is characterized by the increase of renewable generation and distributed energy resources (including distributed generation, self-consumption, demand response and electric vehicles). The paper is an attempt to review and classify flexibility products considering its main attributes such as scope, purpose, location or provider, and to summarize some of the main approaches to flexibility markets designs and implementations. Main current literature gaps and most promising research lines for future work are also identified.

2014

Use of renewable energy systems in smart cities

Autores
Sanchez Miralles, A; Calvillo, C; Martín, F; Villar, J;

Publicação
Green Energy and Technology

Abstract
Renewable energy sources (RES) used in small-scale distributed generation systems are a promising alternative for additional energy supply toward smarter and more sustainable cities. However, their proper integration as new infrastructures of the smart city (SMCT) requires understanding the SMCT architecture and promoting changes to the existing regulation, business models, and power grid topology and operation, constituting a new challenging energy supply paradigm. This chapter addresses the use of renewable energy systems on small scale, oriented to distributed generation (DG) for households or districts, integrated in an SMCT. In this context, the main renewable energies and companion technologies are reviewed, and their profitability investigated to highlight their current economic feasibility. A simplified architecture for SMCT development is presented, consisting of three interconnected layers, the intelligence layer, the communication layer, and the infrastructure layer. The integration and impact of distributed renewable energy generation and storage technologies in this architecture is analyzed. Special attention is paid to the grid topology for their technical and efficient integration, and to the business models for facilitating their economic integration and feasibility. © Springer International Publishing Switzerland 2014.

2016

Vehicle-to-grid profitability considering EV battery degradation

Autores
Calvillo, CF; Czechowski, K; Söder, L; Sanchez Miralles, A; Villar, J;

Publicação
Asia-Pacific Power and Energy Engineering Conference, APPEEC

Abstract
The electrification of the transportation sector is likely to contribute reducing the global dependency on oil and is expected to drive investments to renewable and intermittent energy sources, by taking advantage of it energy storage capacity. In order to facilitate the EV integration to the grid, and to take advantage of the battery storage and the Vehicle-to-Grid (V2G) scheme, smart charging strategies will be required. However, these strategies rarely consider all relevant costs, such as battery degradation. This work analyses the profitability of bidirectional energy transfer, i.e. the possibility of using aggregated EV batteries as storage for energy which can be injected back to the grid, by considering battery degradation as a cost included in the proposed strategy. A mixed integer linear problem (MILP) for minimizing energy costs and battery ageing costs for EV owners is formulated. The battery degradation due to charging and discharging in the V2G scheme is accounted for in the model used. Two case studies of overnight charging of EVs in Sweden and in Spain are proposed. Results show that given current energy prices and battery costs, V2G is not profitable for EV owners, but if battery prices decrease as expected, the V2G will be present in the medium term. © 2016 IEEE.

2014

Wind and solar integration with plug-in electric vehicles smart charging strategies

Autores
Villar, J; Diaz, CA; Gonzalez, P; Campos, FA;

Publicação
International Conference on the European Energy Market, EEM

Abstract
Combining large penetration of Plug-in Electric Vehicles (PEVs) and generation from Renewable Energy Sources (RES) seems a promising solution for energy cost saving and emission reduction. Indeed, RES generation increases instability grid problems due to its intermittency and lack of correlation with final energy usage. But the energy storage of the PEVs connected to the grid, controlled with smart charging and generating strategies, can compensate these uncertainties: energy surplus at low demands and high RES production (strong wind or sunshine) can be returned from PEVs to the grid at larger demand periods, and even provide regulation services. This paper analyses the combined impact of PEVs and RES penetration in the current Spanish power system with a detailed hydro-thermal Unit Commitment (UC) model for energy and reserve. Different charging strategies (from plug-and-charge to V2G with regulation) and wind and solar power penetration are tested with a full year simulation with weekly water management. Simulations show how PEVs smart charging strategies adapt PEVs operation to the existing generation structure, contributing efficiently to higher RES penetration rates, decreasing emissions and system operation costs. © 2014 IEEE.

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