Carlos Benavides

A Microgrid Energy Management System Based on the Rolling Horizon Strategy

A novel energy management system (EMS) based on a rolling horizon (RH) strategy for a renewable-based microgrid is proposed. For each decision step, a mixed integer optimization problem based on forecasting models is solved. The EMS provides online set points for each generation unit and signals for consumers based on a demand-side management (DSM) mechanism. The proposed EMS is implemented for a microgrid composed of photovoltaic panels, two wind turbines, a diesel generator and an energy storage system. A coherent forecast information scheme and an economic comparison framework between the RH and the standard unit commitment (UC) are proposed. Solar and wind energy forecasting are based on phenomenological models with updated data. A neural network for two-day-ahead electric consumption forecasting is also designed. The system is tested using real data sets from an existent microgrid in Chile (ESUSCON). The results based on different operation conditions show the economic sense of the proposal. A full practical implementation of the system for ESUSCON is envisioned.

Energy management system for a renewable based microgrid with a demand side management mechanism

A novel energy management system for a renewable based microgrid is proposed. It provides on-line set points for each generation unit, operation modes for a water supply system, and signals for consumers based on a demand side management mechanism. The smart microgrid is composed of photovoltaic panels, a wind turbine, a diesel generator, a battery bank, and a water supply system. The energy management system (EMS) minimizes the operational costs while supplying the water and electric load demands. It considers a two days ahead prediction of the weather conditions. Also, a neural network for a two days ahead electric consumption forecasting is designed. The system is implemented and tested using a real data set from a reference location. Results show the economic sense of the set points and management, for a practical implementation of the system in a specific location in Chile.

Prospective randomized study of T-tube versus biliary stent for common bile duct decompression after open choledocotomy.

The T-tube has been the alternative of choice for decompression following common bile duct (CBD) exploration. The development of laparoscopic surgery has suggested using a biliary stent as an alternative to the T-tube following choledochotomy. The purpose of this prospective randomized study was to compare clinical results obtained from patients who underwent open CBD exploration using a biliary stent versus those from patients with a T-tube for decompression. Between September 2000 and June 2002 a total of 81 patients were randomly assigned to a biliary stent or a T-tube as the decompression method following choledochotomy. An open CBD exploration was performed when CBD stones were suspected, in both elective and emergency settings. The length of the postoperative hospital stay was 6.8 ± 4.7 days for patients with the T-tube and of 5.2 ± 3.3 days for, patients with the biliary stent (p = 0.19). Postoperative complications were observed in 13 patients (30 %) with the T-tube and in 4 patients (11% ) with the biliary stent (p = 0.03). One patient with a biliary stent was reoperated because of an intraabdominal abscess, and another patient was reoperated because of biliary peritonitis following T-tube removal. Three patients (7%) with a biliary stent and one patient (3%) with a T-tube were rehospitalized. There were no deaths. The T-tube and biliary stent were removed 27.1 ± 10.8 days and 34.9 ± 12.9 days after surgery, respectively (p = 0.24). The biliary stent is a safe alternative to the T-tube as a biliary decompression method following an open CBD exploration.

A framework to identify Pareto‐efficient subdaily environmental flow constraints on hydropower reservoirs using a grid‐wide power dispatch model

Hydrologic alteration due to hydropeaking reservoir operations is a main concern worldwide. Subdaily environmental flow constraints (ECs) on operations can be promising alternatives for mitigating negative impacts. However, those constraints reduce the flexibility of hydropower plants, potentially with higher costs for the power system. To study the economic and environmental efficiency of ECs, this work proposes a novel framework comprising four steps: (i) assessment of the current subdaily hydrologic alteration; (ii) formulation and implementation of a short-term, grid-wide hydrothermal coordination model; (iii) design of ECs in the form of maximum ramping rates (MRRs) and minimum flows (MIFs) for selected hydropower reservoirs; and (iv) identification of Pareto-efficient solutions in terms of grid-wide costs and the Richard-Baker flashiness index for subdaily hydrologic alteration (SDHA). The framework was applied to Chiles main power grid, assessing 25 EC cases, involving five MIFs and five MRRs. Each case was run for a dry, normal, and wet water year type. Three Pareto-efficient ECs are found, with remarkably small cost increase below 2% and a SDHA improvement between 28% and 90%. While the case involving the highest MIF worsens the flashiness of another basin, the other two have no negative effect on other basins and can be recommended for implementation.

Restless Waters: Fossil Fuel Emissions Conditioning a Reduction in Hydroelectric Resources in Chile

Climate change may result in a significant reduction of hydroelectric resources, worrying countries that are heavily dependent on it like many in Central and South America, where most electricity demand is met through hydropower generation. The impact in Chile was described, but Chile can serve as an example for the entire region, where climate change and GHG emissions have become a public concern. Preliminary analyses of the evolution of GHG emissions in the region show the great impact of electricity generation. The need for more accurate analysis and models for various countries in the region is clear. Specifically, mitigation and adaptation strategies should be carefully designed, exploiting potential synergies. Future development of the hydroelectric infrastructure should be analyzed, along with other water usage patterns in the areas of irrigation, drinking water, and industrial processes. The cooptimization of water and energy is therefore envisioned as a path to follow. This must also be considered in the energy market design and its revisions.

Using probabilistic analysis to improve greenhouse gas baseline forecasts in developing country contexts: the case of Chile

ABSTRACT In this paper, initial steps are presented toward characterizing, quantifying, incorporating and communicating uncertainty applying a probabilistic analysis to countrywide emission baseline forecasts, using Chile as a case study. Most GHG emission forecasts used by regulators are based on bottom-up deterministic approaches. Uncertainty is usually incorporated through sensitivity analysis and/or use of different scenarios. However, much of the available information on uncertainty is not systematically included. The deterministic approach also gives a wide range of variation in values without a clear sense of probability of the expected emissions, making it difficult to establish both the mitigation contributions and the subsequent policy prescriptions for the future. To improve on this practice, we have systematically included uncertainty into a bottom-up approach, incorporating it in key variables that affect expected GHG emissions, using readily available information, and establishing expected baseline emissions trajectories rather than scenarios. The resulting emission trajectories make explicit the probability percentiles, reflecting uncertainties as well as possible using readily available information in a manner that is relevant to the decision making process. Additionally, for the case of Chile, contradictory deterministic results are eliminated, and it is shown that, whereas under a deterministic approach Chile’s mitigation ambition does not seem high, the probabilistic approach suggests this is not necessarily the case. It is concluded that using a probabilistic approach allows a better characterization of uncertainty using existing data and modelling capacities that are usually weak in developing country contexts. Key policy insights Probabilistic analysis allows incorporating uncertainty systematically into key variables for baseline greenhouse gas emission scenario projections. By using probabilistic analysis, the policymaker can be better informed as to future emission trajectories. Probabilistic analysis can be done with readily available data and expertise, using the usual models preferred by policymakers, even in developing country contexts.

Perioperative chemotherapy in locally advanced gastric cancer in Chile: From evidence to daily practice.

92 Background: Gastric cancer is the leading cause of cancer death in Chile, with mortality rate of 26.7/100.000 in men, placing the country among the highest mortality rates worldwide. For locally advanced gastric cancer, a multimodality treatment is recommended, but in Chile, the treatment covered by the public health insurance, which assists more than 70% of the patients, is surgery alone. We conducted an observational study to assess efficacy and toxicity of perioperative chemotherapy (CT) in public hospitals in Chile (NCT01633203). Methods: Patients with locally advanced, operable gastric carcinoma, defined as presence of invasion of serosa or beyond (cT > 3 AJCC 2002) and/or lymph node metastasis (cN+) without distant metastasis (M0), were offered to receive preoperative CT with Epirubicin+Cisplatin+Capecitabine (ECX) regimen for 3 cycles followed by curative surgery with D2 lymphadenectomy. Staging abdominal CT scan was mandatory, laparoscopy was recommended. Patients with gastric retention, severe...

VIPoma pancreático: Caso clínico

Neuroendocrine tumors are uncommon, including VIPoma that produces vasoactive intestinal polypeptide. We report a 45-year-old female presenting with a history of diarrhea lasting three months. An abdominal CAT scan showed a solid tumor in the body of the pancreas. A fine needle aspiration biopsy of the tumor was compatible with a neuroendocrine tumor. The patient was subjected to a partial pancreatectomy, excising a 4 cm diameter tumor. The pathological study was compatible with a neuroendocrine carcinoma. There was no regional lymph node involvement. During the postoperative period the results of serum vasoactive intestinal polypeptide were received. These were 815.9 pg/ml before surgery and normalized after the operation.