An efficient multi-objective evolutionary approach for solving the operation of multi-reservoir system scheduling in hydro-power plants

This paper tackles the short-term hydro-power unit commitment problem in a multi-reservoir system ? a cascade-based operation scenario. For this, we propose a new mathematical modeling in which the goal is to maximize the total energy production of the hydro-power plant in a sub-daily operation, and, simultaneously, to maximize the total water content (volume) of reservoirs. For solving the problem, we discuss the Multi-objective Evolutionary Swarm Hybridization (MESH) algorithm, a recently proposed multi-objective swarm intelligence-based optimization method which has obtained very competitive results when compared to existing evolutionary algorithms in specific applications. The MESH approach has been applied to find the optimal water discharge and the power produced at the maximum reservoir volume for all possible combinations of turbines in a hydro-power plant. The performance of MESH has been compared with that of well-known evolutionary approaches such as NSGA-II, NSGA-III, SPEA2, and MOEA/D in a realistic problem considering data from a hydro-power energy system with two cascaded hydro-power plants in Brazil. Results indicate that MESH showed a superior performance than alternative multi-objective approaches in terms of efficiency and accuracy, providing a profit of $412,500 per month in a projection analysis carried out.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri

Evaluating the use of a Net-Metering mechanism in microgrids to reduce power generation costs with a swarm-intelligent algorithm

The micro-generation of electricity arises as a clean and efficient alternative to provide electrical power. However, the unpredictability of wind and solar radiation poses a challenge to attend load demand, while maintaining a stable operation of the microgrids (MGs). This paper proposes the modeling and optimization, using a swarm-intelligent algorithm, of a hybrid MG system (HMGS) with a Net-Metering compensation policy. Using real industrial and residential data from a Spanish region, a HMGS with a generic ESS is used to analyze the influence of four different Net-Metering compensation levels regarding costs, percentage of renewable energy sources (RESs), and LOLP. Furthermore, the performance of two ESSs, Lithium Titanate Spinel ( (LTO)) and Vanadium redox flow batteries (VRFB), is assessed in terms of the final $/kWh costs provided by the MG. The results obtained indicate that the Net-Metering policy reduces the surplus from over 14$ dollars of savings, when compared to a MG using a LTO system without Net-Metering

Proposal for a multidimensional staging system for chronic obstructive pulmonary disease

The severity of chronic obstructive pulmonary disease (COPD) is currently assessed using a single physiological measurement, the forced expiratory volume in 1s (FEV1). COPD, however, has complex effects on other aspects of respiratory function, and in many patients is associated with important systemic changes. We hypothesized that a multidimensional staging system for COPD could provide a more complete assessment of the disease's impact. We considered over 40 potential staging variables, evaluating them according to sensitivity to change, measured reproducibly, independence of the information they provide and prognostic value. We finally selected three: FEV1 (including arterial blood gas measurements when FEV1 falls below 35% predicted), Medical Research Council dyspnea scale and body mass index (BMI). Each measure correlates independently with prognosis in COPD, is supported by a significant body of literature and serves as a surrogate for other potentially important variables. We then used principal components analysis (PCA) to determine the degree of association between 30 of the potential variables measured in 813 stable COPD patients. Using PCA, six groups of measurements defined independent categories of patient information: pulmonary function (including FEV1), symptoms of cough and sputum, dyspnea, health status, bronchodilator reversibility and BMI. These include the three principal variables selected for the staging system. Although the staging boundaries were based on existing literature, they have proven useful in predicting survival. We conclude that a multidimensional grading system is useful to assess the impact of COPD.<br/