Andres Emiro Diez Restrepo

The growing demand for efficient and sustainable energy storage has intensified interest in green materials known for their high-power density. In this work, we evaluated the electrochemical and electrical performance of coin-cell supercapacitors with activated carbon electrodes from palm kernel shell. Two activated carbons were obtained using KOH and ZnCl₂ as activating agents at 700 °C and then superficially modified with nitric acid. The KOH-activated carbon electrodes showed the highest specific surface area (1181 m² g⁻¹) and the best electrochemical behavior, reaching an average gravimetric capacitance of 56. ± 9.2 F g⁻¹. The coins were characterized electrically by series and parallel arrangements, yielding specific energy and specific power densities of 2.6 Wh kg⁻¹ and 475 W kg⁻¹, and 1.8 Wh kg⁻¹ and 353 W kg⁻¹, at 0.001 A and 0.75 V for parallel and series arrangements, respectively.

Multimodal electric transport systems demand substantial active and reactive energy, making power-quality management essential for ensuring efficient and reliable operation. This paper analyses reactive-energy transport in mass-transit networks and introduces a unified current-based framework that enables a consistent interpretation of the conventional power factor under harmonic distortion, fundamental unbalance, and short-term load fluctuation, without modifying its original definition. The framework enables a consistent assessment of compensation needs, independent of billing schemes, and is aligned with the way modern compensation equipment is specified and controlled. Applied to the Metro de Medellín system, field measurements and digital simulations show that traditional reactive-energy limits fail to distinguish between harmful and beneficial operating conditions, leading to disproportionate charges under the former Colombian regulation. Beyond this case, the proposed framework is directly applicable to other electric-mobility systems—including railways, trams, trolleybuses, and electric-bus networks—providing clearer technical signals for compensation planning and offering a comprehensive basis for future regulatory approaches that integrate multiple power-quality phenomena.

This paper presents an electrical infrastructure planning method for transit systems that operate with partially grid-connected vehicles incorporating on-board batteries. First, the state-of-the-art of electric transit systems that combine grid-connected and battery-based operation is briefly described. Second, the benefits of combining a grid connection and battery supply in Bus Rapid Transit (BRT) systems are introduced. Finally, the planning method is explained and tested in a BRT route in Medellin, Colombia, using computational simulations in combination with real operational data from electric buses that are currently operating in this transit line. Unlike other methods and approaches for Battery Electric Bus (BEB) infrastructure planning, the proposed technique is system-focused, rather than solely limited to the vehicles. The objective of the technique, from the vehicle’s side, is to assist the planner in the correct sizing of batteries and power train capacity, whereas from the system side the goal is to locate and size the route sections to be electrified. These decision variables are calculated with the objective of minimizing the installed battery and achieve minimum Medium Voltage (MV) network requirements, while meeting all technical and reliability conditions. The method proved to be useful to find a minimum feasible cost solution for partially electrifying a BRT line with In-motion Charging (IMC) technology.

In preparation for the electric mobility technological transition in Colombia, an impact assessment of the electric power system is required, considering the increasing loading that must be able to be managed in the future. In this paper, a plug-in electric vehicle (PEV) charging simulation methodology is developed in order to dimension the impact of this type of load on power grids. PEV electric properties, user charging behaviors, geographic location, trip distances, and other variables of interest are modeled from empirical or known probability distributions and later evaluated in different scenarios using Monte Carlo simulation and load flow analysis. This methodology is later applied to the transmission network of Antioquia (a department of Colombia) resulting in load increases of up to 40% on transmission lines and 20% on transformers in a high PEV penetration scenario in 2030, increases that are well within the expected grid capacity for that year, avoiding the need for additional upgrades.

El objetivo de este trabajo es analizar el consumo energético de un sistema de transporte público de pasajeros de tracción eléctrica desde una perspectiva sistémica, a partir de la simulación con Dinámica de Sistemas. Como caso de estudio se usan los datos de la Empresa de Transporte Masivo del Valle de Aburrá. Este análisis considera un arquetipo clave para el planteamiento de la hipótesis dinámica: los límites del crecimiento. Los resultados obtenidos en las simulaciones mostraron cómo el uso de la capacidad de la infraestructura eléctrica, con la incorporación de nuevos proyectos de expansión, puede limitar su capacidad de operar ante contingencias. Se concluye que la planificación debe tener en cuenta que los esfuerzos realizados para expandir el sistema tienen éxito en etapas iniciales, pero cuando éstos llegan a los límites del crecimiento, comienzan a perder efectividad. Por lo tanto, el rendimiento comienza a ser decreciente, afectando la capacidad de oferta del servicio de transporte.

Se estudia la aplicación de sistemas de compensación basados en ultra capacitores en el sistema de potencia del Metro de Medellín. Los sistemas de compensación basados en ultra capacitores permiten mejorar la eficiencia energética de sistemas ferroviarios, al evitar que parte de la energía regenerada en frenados sea disipada en forma de calor, logrando al mismo tiempo estabilizar la tensión de alimentación. Con la implementación de estos sistemas también se aprovecha mejor la infraestructura de alimentación eléctrica, permitiendo expansiones de la línea y/o incremento de la flota del sistema, con menores inversiones. Para la aplicación estudiada se efectuó un diagnóstico del sistema de alimentación para evaluar los requerimientos y beneficios de implementar un compensador. El diseño del sistema compensador fue asistido por computador, usando un modelo digital que se describe en este trabajo. Finalmente se presentan los resultados obtenidos en operación real del dispositivo.