Abstract Energy sources, like hydro and wind power, present uncertain nature, characteristic that affects the electric power systems operation planning. Such factors require using methodologies capable to handle these uncertainties in interconnected hydro-thermal-wind power systems operation. This work proposes a computational model for the day-ahead unit commitment problem for interconnected hydro-thermal-wind power systems, considering the uncertainties related to wind power, water inflow, and energy demand, employing the Robust Optimization (RO). The optimization model consists in a three-level mixed integer linear programming problem, which is resolved using a two-stage decomposition approach, solved using the column-and-constraint generation algorithm. The model is validated using the 30 nodes IEEE and the 33 nodes Brazilian test system. The model proposed proved to have an operating cost proportional to the level of uncertainty and the methodology employed provides a preventive view of what may occur during the hydro-thermal-wind systems operation, allowing the central system operator to take certain actions in order to ensure reliable operating conditions. In addition, the model allowed the identification of important aspects related to computational costs, such as the verification that constraints that couple the problem in time and space significantly impact the simulation times of the problem. sources nature planning hydrothermalwind thermal dayahead day ahead inflow demand RO. RO . (RO) threelevel three twostage two stage approach columnandconstraint column constraint algorithm 3 conditions addition costs (RO

Abstract Variable renewable energies are leading the energy transition and power system flexibility has become a global priority. Incorporating short-term assessment into long-term planning is essential to capture the operational characteristics of generation and address flexibility issues. This paper presents a novel model for generation and transmission expansion planning with economic dispatch. In the generation expansion planning, the capacity expansion is optimized. In the economic dispatch problem, power plant operation, hydropower generation, and line transmission power flow are optimized. The model is a mixed-integer linear programming problem solved in MATLAB using Gurobi toolbox. A model is proposed to optimize the reservoir of hydropower systems and run-of-river. A case study for supplying Brazilian demand in 2050 is presented. A scenario with greenhouse gas emission costs and no deficit is proposed. This study has shown that the current penalty cost for loss of load is not sufficient to avoid a deficit. It is possible to supply 2050 demand, without large reservoirs or deficits, with a 5.5% curtailment, using 13% of total storage capacity, however; peaking power plants are required. priority shortterm short term longterm long issues optimized operation mixedinteger mixed integer toolbox runofriver. runofriver run river. river run-of-river 205 presented deficits 55 5 5.5 curtailment 13 however required 20 5. 1 2

Abstract. - In Mexico the development of remote laboratories is incipient, in 2020 the National Council of Humanities, Sciences, and Technologies (CONAHCYT) created a network of virtual laboratories with nine of its public research centers in order to create a virtual space that enables the development of experimental and research activities in a distance modality. However, access to virtual laboratories is limited only to its members, and the platforms are still under development. With this motivation, this article presents a multi-institutional project for the design, development, and implementation of a pico-hydraulic system for small-scale power generation for teaching and training purposes with the aim of responding to the current need for distance or virtual teaching of practical knowledge due to the coronavirus disease (COVID‑19) caused by the SARS-CoV-2 virus. For the development of the system, technological innovation tools (QFD, TRIZ) were used, with which the design requirements were obtained considering the users (students and teachers) and the renewable energy-related competence of the curricula. Finally, the satisfaction of the users (students and teachers) with the use of the designed system shows the advantage of including it as part of the practical activities of the subjects to improve the development of power generation, transformation, and transmission system projects.

Resumen. - En México el desarrollo de laboratorios remotos es incipiente, en 2020 el Consejo Nacional de Humanidades, Ciencias y Tecnologías (CONAHCYT) creó una red de laboratorios virtuales con nueve de sus centros públicos de investigación con el fin de crear un espacio virtual que permita el desarrollo de actividades experimentales y de investigación en la modalidad a distancia. Sin embargo, el acceso a los laboratorios virtuales está limitado sólo a sus miembros y las plataformas aún están en desarrollo. Con esta motivación este artículo presenta un proyecto multi-institucional para el diseño, desarrollo e implementación de un sistema pico-hidráulico para la generación de energía a pequeña escala con fines de enseñanza y capacitación con el objetivo de responder a la necesidad actual de enseñanza a distancia o virtual de conocimientos prácticos debido a la enfermedad coronavirus (COVID-19) causada por el virus SARS-CoV-2. Para el desarrollo del sistema se utilizaron herramientas de innovación tecnológica (QFD, TRIZ), con las que se obtuvieron los requisitos de diseño teniendo en cuenta los usuarios (alumnos y profesores) y las competencias relacionadas con las energías renovables de los planes de estudio. Finalmente, la satisfacción de los usuarios (alumnos y profesores) sobre el uso del sistema diseñado muestra la ventaja de incluirlo como parte de las actividades prácticas de las asignaturas para mejorar el desarrollo de proyectos de sistemas de generación, transformación y transmisión de energía.

Abstract The benefits of complementarity between renewable energy sources have been presented as having a positive impact, but it has been neglected in generation expansion planning studies. In this paper the complementarity between renewable energy sources and regions of Brazil is characterized and the correlation coefficients are analyzed. A methodology is also proposed to optimize the complementarity between the sources, reducing the energy storage requirements. The methodology is applied to the Brazilian case to meet the projected demand for 2050 with a 100% renewable system and the complementarity is analyzed. The characterization of the data allowed us to propose five solar regions, four wind regions, three hydro regions and a region to represent the biomass. It was possible to find complementarity (negative correlation) of: 0.97 between hydro regions; 0.86 between wind and hydro regions and; 0.96 between biomass and hydro. The proposed methodology allowed us to know which regions and their respective technologies best benefit the electrical system, being the North for solar and the Northeast for wind. Finally, it was possible to reduce the demand for water storage with sources and regions that complement the seasonal hydro drought period. impact studies analyzed requirements 205 100 negative 097 0 97 0.9 086 86 0.8 096 96 Finally period 20 10 09 9 0. 08 8 2 1

Resumen El propósito de este trabajo es presentar dos juegos de inversión, con información completa e imperfecta en tres etapas, que permita la identificación del equilibrio de los jugadores en un mercado oligopólico. La reestructuración del mercado de energía trajo consigo la aparición de nuevos competidores convirtiendo al sector en un escenario con alto riego e incertidumbre, como consecuencia de la volatilidad de la demanda, competencia entre agentes, los precios de la electricidad y de los combustibles, dificultando de esta forma la toma de decisiones en relación con la inversión en la generación de la electricidad. Esta propuesta aplica como metodología la teoría de juegos que ayuda a la toma de decisiones en una estrategia de competencia imperfecta. Se concluye que cuando hay suficiente información tanto para el titular como el potencial entrante, la mejor opción es invertir, pero cuando la información es asimétrica, la mejor opción para el Potencial Entrante es invertir.

Abstract This paper aims to present two investment games with complete and incomplete information in three stages that allow identifying equilibria games of the players in the oligopoly market. The restructuring of the power market brought with it new competitors' appearance to become a sector with high risk and uncertainty due to demand, electricity, oil price volatility, competence between firms, among others, thus making it difficult to make decisions regarding investment in electricity generation. This proposal applies the games theory methodology that helps making-decisions in an imperfect competence market. This study shows that when the firms have enough information, the best option for the incumbent and potential entrants firms is to invest. When the information is asymmetric, the best option for Entrants Potential firm is to invest.

Resumen: En Ecuador, la energía hidroeléctrica excede el 90% de la energía eléctrica y el Complejo Hidroeléctrico Paute Integral es el más importante en generación eléctrica. Dadas las características de la infraestructura de este complejo, el despacho hidrotérmico de mediano plazo (MTHD, por sus siglas in inglés) es de gran importancia, ya que permitiría establecer reglas operativas que sin duda impactarían en el costo total de generación del sistema eléctrico del país. Es por esto que se presenta dos estudios de MTHD: el primero de tipo probabilístico con variables estocásticas para los caudales afluentes a las represas del complejo y para la carga a ser atendida. Este estudio se lo compara con un segundo modelo propuesto por el autor, el cual se basa en encontrar niveles óptimos diarios para cada represa bajo análisis realizando una simulación diaria del sistema. Al realizar la comparación de los dos modelos, en términos de reglas operativas son altamente coincidentes; sin embargo, en términos de energía producida por el Complejo Paute Integral, el segundo modelo, con mayor nivel de detalle, y mediante una efectiva coordinación de la operación entre centrales hidroeléctricas en cascada, logra aprovechar mejor el recurso hídrico y en consecuencia una mayor producción del complejo.

Abstract: In Ecuador, hydropower exceeds 90% of electrical energy and the Paute Integral Hydroelectric Complex is the most important in electricity generation. Given the characteristics of the infrastructure of this complex, the Medium-Term Hydrothermal Dispatch (MTHD) is of utmost importance, since it would allow establishing operational rules that would undoubtedly affect the total cost of generation of the country's electricity system. This is why two MTHD studies are presented: the first study is probabilistic with stochastic variables for the inflows to the complex's dams and for the load to be served. This study is compared with a second model proposed by the author, which is based on finding daily optimal levels for each dam under analysis by performing a daily simulation of the system. When comparing the two models, in terms of operational rules they are entirely coincident; however, in terms of energy produced by Paute Integral Complex, the second model, with a higher level of detail, and through effective coordination of the operation between hydropower plants in cascade, manages to make better use of the water resource and consequently a higher production of the complex.

Only 40% of Zimbabwe's population has access to electricity. The greater proportion of the power is generated from thermal stations, with some from hydro and solar energy sources. However, there is little investment in the use of wind for electricity generation except for small installations in the Eastern Highlands, as Zimbabwe generally has wind speeds which are too low to be utilised for electricity generation. This paper presents the use of vertical wind profile extrapolation methods to determine the potential of generating electricity from wind at different hub heights in Zimbabwe, using the Hellman and exponential laws to estimate wind speeds. The estimated wind speeds are used to determine the potential of generating electricity from wind. Mangwe district in Matabeleland South province of Zimbabwe was used as a test site. Online weather datasets were used to estimate the wind speeds. The investigation shows that a 2.5kW wind turbine installation in Mangwe can generate more than 3MWh of energy per annum at hub heights above 40m, which is enough to supply power to a typical Zimbabwean rural village. This result will encourage investment in the use of wind to generate electricity in Zimbabwe.Highlights • Wind power utilisation is low in Zimbabwe. • Vertical wind profile is estimated using extrapolation methods. • Online weather data for soil and water analysis tool was used. • Electricity can viably be generated from wind in Zimbabwe.Data Availability: On request from authors

ABSTRACT The present work aims to show the results obtained in the design and implementation of a rehabilitation project in the generation Unit # 1 of the Hanabanilla hydroelectric power station located in the mountain massif of Escambray of Villa Clara province, in order to improve the automatic regulation of the frequency of the National Electrical System. For this purpose, control algorithms implemented on the PLC that commands the speed governor or governor model HAUCK Hydraulik - Technik are used. These algorithms are novel because they adapt to the requirements of frequency regulation designed by the National Dispatch Office (NDO) for this plant, the only one of its kind in the country. In carrying out the project, technical, economic and efficiency requirements are taken into account in order to achieve an adequate and sustainable use of water, a resource of great value for mankind and the environment.

RESUMEN El presente trabajo tiene como objetivo mostrar los resultados obtenidos en el diseño e implementación de un proyecto de rehabilitación en la Unidad # 1 de generación de la central hidroeléctrica Hanabanilla ubicada en el macizo montañoso del Escambray villaclareño, para mejorar la regulación automática de la frecuencia del Sistema Eléctrico Nacional. Para ello se emplean algoritmos de control implementados sobre el PLC que comanda el regulador de velocidad o gobernador modelo HAUCK Hydraulik - Technik. Estos algoritmos resultan novedosos ya que se adecuan a los requisitos de regulación de frecuencia diseñados por el Despacho Nacional de Carga (DNC) para esta central, única de su tipo en el país. En la realización del proyecto se toman en cuenta requisitos técnicos, económicos y de eficiencia en aras de lograr un uso adecuado y sostenible del agua, recurso de gran valor para el hombre y el medio ambiente.

Abstract This paper proposes a variant of the Colombian official methodology employed in the computation of firm energy (FE) produced by hydro power plants (MCREG). Firm energy is defined as the maximum electrical energy that a plant is able to continuously deliver under low hydrological conditions. This research establishes that for determining the FE, hydrological series should be annually decoupled in the MCREG optimization model to avoid the assumption that future hydrological events will occur in the same historical chronological order. Time series are randomly generated through multivariate and correlated normal distributions, whose parameters are estimated from historical inflow data. Additionally, it is also possible to model the intertemporal correlation between monthly inflows of hydro power plants. The proposed methodology (abbreviated as MDEF) is compared with MCREG. This comparison was done for two power plants (338 and 1000 MW) and the results indicate that EF obtained with MDEF is higher and less uncertain if a significant number of time series is considered.

Resumen Este artículo propone una variante a la metodología oficial colombiana para el cálculo de la energía firme (EF) de plantas de generación hidráulica (MCREG). La EF es la máxima energía eléctrica que es capaz de suministrar una planta de generación continuamente en condiciones de baja hidrología. En este trabajo, se plantea que, para determinar la EF, las series hídricas se modelen desacopladas anualmente para no suponer la ocurrencia de eventos hidrológicos futuros en el mismo orden cronológico histórico. Las series son generadas a partir de datos históricos de caudales empleando distribuciones normales correlacionadas. Aparte de la creación de series que reflejan la tendencia histórica, se ha logrado modelar la correlación temporal entre los caudales hídricos mensuales de plantas hidráulicas. La metodología desacoplada propuesta (abreviada como MDEF) se compara con la MCREG para dos plantas hidráulicas (338 y 1000 MW), y los resultados indican que la EF obtenida con la MDEF es mayor y menos incierta si el número de series sintéticas es significativo.

RESUMEN Este artículo presenta una técnica híbrida para resolver la programación del mantenimiento de las unidades de generación coordinado con el despacho hidrotérmico de mediano plazo. La solución se basa en el algoritmo genético de Chu-Beasley y en la técnica de programación lineal. Tiene en cuenta no linealidades derivadas del costo de los combustibles utilizados por las centrales térmicas. La salida del algoritmo genético es una propuesta de la semana de inicio del plan de mantenimiento de cada unidad de generación que minimiza el costo del despacho hidrotérmico. Las dos principales contribuciones de este trabajo son que propone un modelo matemático que coordina dos problemas que en la literatura se han resuelto de forma separada, y que aplica un algoritmo genético especializado que aún no ha sido utilizado para resolver el problema coordinado. El sistema de prueba para validar la metodología se compone de tres centrales hidroeléctricas y dos centrales térmicas dividas en 22 unidades de generación, teniendo en cuenta el mantenimiento preventivo, en un horizonte de planeamiento de un año (52 semanas). Esta metodología combina una técnica exacta con un algoritmo genético especializado, lo que favorece la convergencia.

ABSTRACT This paper presents a hybrid technique for solving the generation maintenance scheduling coordinated with middle term hydrothermal dispatch based on the Chu-Beasley genetic algorithm and linear programming. It takes into consideration the non-linearity derived from the cost of the fuel for thermal power plants. The output of the genetic algorithm is a proposal for the start week of the generation maintenance plan that minimises the hydrothermal dispatch cost. This work has two main contributions: on one hand proposing a solution that integrates hydrothermal dispatch and maintenance scheduling in a single model, therefore a new mathematical model and, on the other hand the proposed solution applies a specialised genetic algorithm that has not been applied before to solve this problem. The test system to validate the methodology is composed of three hydro plants and two thermal plants split into 22 generation units, considering three types of preventive maintenance, in a planning term of one year (52 weeks). This methodology combines an exact technique and a specialised genetic algorithm, which favours convergence.

ABSTRACT The Brazilian electricity energy matrix is essentially formed by hydraulic sources which currently account for 70% of the installed capacity. One of the most important characteristics of a generation system with hydro predominance is the strong dependence on the inflow regimes. Nowadays, the Brazilian power sector uses the PAR(p) model to generate scenarios for hydrological inflows. This approach does not consider any exogenous information that may affect hydrological regimes. The main objective of this paper is to infer on the influence of climatic events in water inflows as a way to improve the model’s performance. The proposed model is called “causal PAR(p)” and considers exogenous variables, such as El Niño and Sunspots, to generate scenarios for some Brazilian reservoirs. The result shows that the error measures decrease approximately 3%. This improvement indicates that the inclusion of climate variables to model and simulate the inflows time series is a valid exercise and should be taken into consideration.

RESUMO Estudou-se a otimização técnico-econômica da geração elétrica de pequenas centrais hidrelétricas (PCH) de baixa queda da Amazônia, objetivando contribuir para estudos hidro energéticos de PCHs. Curvas de permanência de vazões necessárias ao dimensionamento de PCHs foram simuladas com o Modelo Hidrológico Não-linear Simples com Fator de Ganho Sigmoidal (MSV). Devido a sazonalidade climática inerente à Amazônia, a geração hidrelétrica das PCHs foi considerada utilizando duas turbinas hidráulicas axiais em paralelo. Para a otimização técnica, com o programa CARTHA obtiveram-se curvas de carga das turbinas, para estudo da influência da regulagem e relação das potências das turbinas sobre a eficiência energética das PCHs. Conclui-se que PCHs dotadas de turbinas com regulagem dupla apresentam eficiência de 80%, com regulagem do rotor 72% e com regulagem do distribuidor 65%. Para a otimização econômica, estudaram-se três cenários de mercado: desaquecido, neutro e aquecido. Conclui-se que os melhores resultados técnico-econômicos foram obtidos para PCHs com potência total da ordem de 30MW, turbinas iguais, apenas com regulagem do rotor, mercado desaquecido, resultando em Período de Retorno de 1,7 anos e Rentabilidade de 222%.

ABSTRACT The technical and economic optimization of electricity generation by small hydropower plants (SHP) with a low head in the Amazon is studied, in order to contribute to hydro energy studies of these SHP. The flow duration curves (FDC) needed to design hydropower generation were simulated using the Nonlinear Hydrological Model Simple with Sigmoidal Gain Factor (SVM). Due to seasonality inherent to the Amazon, SHP generation was considered using two axial turbines operating in parallel. For technical optimization the CARTHA program was used to obtain the axial turbine load curves, allowing the study of the influence of the type of regulation and the relationship of the powers of the turbines on the energy efficiency of SHP. Plants with double regulation turbines presented an efficiency of 80%, for rotor regulation 72% and for distributor regulation 65%. Three market scenarios were studied for economic optimization: sluggish, neutral and hot. The best technical and economic results were obtained for SHP with total power on the order of 30MW, equal turbines equipped with rotor regulation only, sluggish market, resulting to the return period of 1.7 years and profitability of 222%.

The current study applies an energy-system model to explore energy supply options in meeting Tanzania's electricity demands projection from 2010 to 2040. Three economic scenarios namely; business as usual (BAU), low economic consumption scenario (LEC) and high economic growth scenario (HEC) were developed for modelling purposes. Moreover, the study develops a dry weather scenario to explore how the country's electricity system would behave under dry weather conditions. The model results suggests: If projected final electricity demand increases as anticipated in BAU, LEC and HEC scenarios, the total installed capacity will expand at 9.05%, 8.46% and 9.8% respectively from the base value of 804.2MW. Correspondingly, the model results depict dominance of hydro, coal, natural gas and geothermal as least-cost energy supply options for electricity generation in all scenarios. The alternative dry weather scenario formulated to study electricity system behaviour under uncertain weather conditions suggested a shift of energy supply option to coal and natural gas (NG) dominance replacing hydro energy. The least cost optimization results further depict an insignificant contribution of renewable energy technologies in terms of solar thermal, wind and solar PV into the total generation shares. With that regard, the renewable energy penetration policy option (REPP), as an alternative scenario suggests the importance of policy options that favour renewable energy technologies inclusion in electricity generation. Sensitivity analysis on the discount rate to approximate the influence of discount rate on the future pattern of electricity generation capacity demonstrated that lower values favour wind and coal fired power plants, while higher values favour the NG technologies. Finally, the modelling results conclude the self-sufficiency of the country in generating future electricity using its own energy resources.

En la actualidad, la matriz energética de Bolivia se encuentra desbalanceada debido a la producción primaria de energía, la cual se enfoca principalmente en la producción de hidrocarburos gaseosos. Sin embargo, el consumo es en cambio intensivo en hidrocarburos líquidos. Adicionalmente, el sistema eléctrico en Bolivia se caracteriza principalmente por la generación termoeléctrica, siendo que el país cuenta con un potencial para la generación hidroeléctrica. En este contexto, este trabajo referencia la evolución de la tendencia de la matriz energética de Bolivia y propone escenarios de mitigación basados en: a) la reducción del consumo de hidrocarburos líquidos; b) introducción de energías renovables y medidas de eficiencia energética en el sistema eléctrico nacional. La construcción de estos escenarios, se desarrolla metodológicamente mediante simulaciones tipo bottom-up para el periodo 20072025. Las estimaciones presentadas en este documento, se basan en resultados anteriores que los autores obtuvieron en el proyecto de Generación de Energías Renovables en América del Sur (REGSA), fundada por la Unión Europea.

Nowadays the Bolivian energy-mix is misbalanced due to the primary production of energy, which is focused in gaseous hydrocarbons, whereas the consumption is intensive in liquid hydrocarbons. At the same time the Bolivian electric system is mainly thermo, while the country present high hydro potential. In this framework this document makes reference to the trending evolution of the Bolivian energy-mix and proposes a mitigation scenarios based on the a) reduction of liquid hydrocarbons consumption; b) and introduction of renewable energies an energy efficiency measures in the electric system. Methodologically, the construction of such scenarios is developed by a bottom-up simulation for the time span 2007-2025. We based our estimations on previous results we obtained in the project Renewable Energies Generation in South America (REGSA), founded by the European Union.

El propósito del presente artículo es realizar una revisión y análisis contextual y de requerimientos básicos a tener en cuenta para implementar proyectos de Pequeñas Centrales Hidroeléctricas, para lo cual se realizó una recopilación de información y una revisión bibliográfica que permitió conocer la situación actual de la técnica a nivel nacional e internacional, así como las tecnologías más eficientes y aptas para su implementación. Por último, se plantean unas etapas y estudios de ingeniería a seguir para lograr con éxito el desarrollo de un proyecto de PCH y se definen las conclusiones pertinentes del análisis realizado.

The purpose of this article is to review and analyze the context and basic requirements to be considered to implement projects of Small Hydro Power, which was performed by collecting information and reviewing of the current state of technology in the country and worldwide, as well as the most efficient and suitable technologies for its implementation. Finally, it raises some stages and engineering studies to follow for successful development of an SHP project and defines the relevant conclusions of the analysis.