2020
Authors
Lopes, JAP; Madureira, AG; Matos, M; Bessa, RJ; Monteiro, V; Afonso, JL; Santos, SF; Catalao, JPS; Antunes, CH; Magalhaes, P;
Publication
WILEY INTERDISCIPLINARY REVIEWS-ENERGY AND ENVIRONMENT
Abstract
The decarbonization of the economy, for which the contribution of power systems is significant, is a growing trend in Europe and in the world. In order to achieve the Paris Agreement's ambitious environmental goals, a substantial increase in the contribution of renewable sources to the energy generation mix is required. This trend brings about relevant challenges as the integration of this type of sources increases, namely in terms of the distribution system operation. In this paper, the challenges foreseen for future power systems are identified and the most effective approaches to deal with them are reviewed. The strategies include the development of Smart Grid technologies (meters, sensors, and actuators) coupled with computational intelligence that act as new sources of data, as well as the connection of distributed energy resources to distribution grids, encompassing the deployment of distributed generation and storage systems and the dissemination of electric vehicles. The impact of these changes in the distribution system as a whole is evaluated from a technical and environmental perspective. In addition, a review of management and control architectures designed for distribution systems is conducted. This article is categorized under: Energy Infrastructure > Systems and Infrastructure Energy Infrastructure > Economics and Policy
2020
Authors
Valka, K; Roseira, C; Campos, P;
Publication
INDUSTRY AND HIGHER EDUCATION
Abstract
As the ongoing evolution in the higher education sector changes the roles of universities, entrepreneurial practices become more prominent in their agendas. The literature on academic entrepreneurship focuses predominantly on the commercialization of research and less on other intrapreneurial activities-namely those performed by non-academic employees. To fill this gap, this study aims to provide a comprehensive understanding of the factors that influence universities' faculty members and non-academic staff to engage in intrapreneurial activities. The article analyzes Latvian university employees' perceptions of 13 organizational, individual, and environmental factors and how they influence intrapreneurial behavior. Regarding the organizational factors, the results show that higher trust in managers, more available resources for innovative ideas, less formal rules and procedures, and greater freedom in decision-making can lead to higher levels of intrapreneurial behavior. With regard to individual factors, intrapreneurial behavior is associated with an employee's initiative, but is not correlated with risk-taking and personal initiative. As to external factors, while environmental munificence is positively correlated with innovativeness, dynamism and unfavorable change influence employees' engagement in intrapreneurial activities.
2020
Authors
Martinez, SD; Campos, FA; Villar, J; Rivier, M;
Publication
ELECTRIC POWER SYSTEMS RESEARCH
Abstract
Power systems will face important structural changes in the near future due to the empowerment of consumers, who may resort on self-consumption, and reduce their purchases of electricity from the grid. The avoided costs of purchasing energy, as compared to the investment costs of installing their own self-generation capacity, could be one of the drivers of the consumers' decision making. The system expansion will therefore result from the interaction of the traditional market agents, maximizing their profits by investing in and operating centralized generation assets, and the new active consumers, minimizing their expenses while meeting their energy needs. This paper presents a Nash equilibrium model that considers centralized and behind-the-meter distributed generation expansion, by representing the operation and investments decisions of both types of agents with their own conceptually different strategies. To simplify the resolution, the equilibrium model is transformed into an equivalent minimization problem from its Karush-Kuhn-Tucker conditions. The model application to Spain-like system case example allows to assess the impact of the network access-tariff (whether being mainly volumetric-based or power-based) and the impact of the big industrial market power on the generation expansion, for the time horizon 2019-2037.
2020
Authors
Silva, F; Alonso, AN; Pereira, J; Oliveira, R;
Publication
DAIS
Abstract
The performance and scalability of byzantine fault-tolerant (BFT) protocols for state machine replication (SMR) have recently come under scrutiny due to their application in the consensus mechanism of blockchain implementations. This led to a proliferation of proposals that provide different trade-offs that are not easily compared as, even if these are all based on message passing, multiple design and implementation factors besides the message exchange pattern differ between each of them. In this paper we focus on the impact of different combinations of cryptographic primitives and the message exchange pattern used to collect and disseminate votes, a key aspect for performance and scalability. By measuring this aspect in isolation and in a common framework, we characterise the design space and point out research directions for adaptive protocols that provide the best trade-off for each environment and workload combination.
2020
Authors
Naversen, CO; Helseth, A; Li, BS; Parvania, M; Farahmand, H; Catalao, JPS;
Publication
ELECTRIC POWER SYSTEMS RESEARCH
Abstract
Continuous-time optimization models have successfully been used to capture the impact of ramping limitations in power systems. In this paper, the continuous-time framework is adapted to model flexible hydropower resources interacting with slow-ramping thermal generators to minimize the hydrothermal system cost of operation. To accurately represent the non-linear hydropower production function with forbidden production zones, binary variables must be used when linearizing the discharge variables and the continuity constraints on individual hydropower units must be relaxed. To demonstrate the performance of the proposed continuous-time hydrothermal model, a small-scale case study of a hydropower area connected to a thermal area through a controllable high-voltage direct current (HVDC) cable is presented. Results show how the flexibility of the hydropower can reduce the need for ramping by thermal units triggered by intermittent renewable power generation. A reduction of 34% of the structural imbalances in the system is achieved by using the continuous-time model.
2020
Authors
Nunes, LJR; Pereira da Costa, JTP; Godina, R; Matias, JCO; Catalao, JPS;
Publication
ENERGIES
Abstract
The biomass industry is growing due to the current search for greener and more sustainable alternatives to fossil energy sources. However, this industry, due to its singularity, presents several challenges and disadvantages related to the transportation of raw materials, with the large volumes that are usually involved. This project aimed to address this internal logistics situation in torrefied biomass pellets production with two different biomass storage parks, located in Portugal. The main park receives raw material coming directly from the source and stores it in large amounts as a backup and strategic storage park. The second park, with smaller dimensions, precedes the production unit and must be stocked daily. Therefore, a fleet of transport units with self-unloading cranes is required to help to unload the biomass at the main park and transport the raw material from this park to the one preceding the production unit. Thus, the main goal was to determine the dimensions of the fleet used in internal transportation operations to minimize the idle time of the transport units using a methodology already in use in the mining and quarrying industry. This methodology was analyzed and adapted to the situation presented here. The implementation of this study allows the elimination of unnecessary costs in an industry where the profit margins are low.
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