• Energy Research

This paper analyzes the problems in electrical power systems with high penetration of photovoltaic systems, which must be considered in evaluating new projects with these generation sources. The study analyzes the characteristics of photovoltaic systems, their generated effects, and proposals for technological improvements. The features of electric motors and their affectation when they are fed from networks with power quality problems are also described. As a result, the variability in energy production, the difficulties in frequency regulation, the increase in harmonics, and the instability in generating reactive power, are the main problems caused by the massive use of photovoltaic systems. Regarding electric motors, it is shown that harmonics and voltage regulation are the power quality problems that most affect their operation. None of the studies conducted analyzes the direct influence that photovoltaic systems can have on the process of electric motors. Considering the growth prospects for using photovoltaic systems and the importance of electric motors, it is suggested that the scientific community develop research focused on this problem.

This study identifies the main factors affecting the electricity efficiency and productivity of the lead acid battery formation process. A representative sample of 12,286 battery formation processes, developed between June 2014 and June 2015, were used in a statistic analysis. As a result, an energy performance indicator was developed to assess the electricity consumption of battery formation. Given that there are several formation circuits in the formation area, an energy performance indicator was developed for each circuit. The influence of the operational practices, operational teams, workings shift starting time and technical condition of the circuits were analyzed. The influence of the operational practices and the technical conditions of the formation circuits were identified as the main factors affecting the productivity and the electricity consumption. These factors cause a time waste, affecting productivity between 2 and 5%, and increasing the electricity consumption. As a result it is recommended to improve maintenance and operational practices towards higher productivity and electricity efficiency.

This paper aims to present a procedure that allows identifying savings opportunities in a steel manufacturing company. The procedure based on the ISO 50001, 50004, and 50006 standards comprise the use of tools such as energy baselines, the goal line, energy performance indicators, the Pareto chart, and an energy review. As a result of the implementation of the procedure, it was possible to obtain the baseline, the goal line, and energy performance indicators that allow the control of energy consumption and efficiency of the company in general and of the area with the highest electricity consumption. It was possible to identify that there is a potential savings of up to 6% throughout the company and up to 13% in the area with the highest electrical energy consumption. From an energy review carried out in the area with the highest consumption, motors operating with low load and idle for long periods were identified, as well as a lack of maintenance. Besides, the replacement of traditional technology lamps by LED technology lamps was proposed. The procedure can be generalized in steel industries with similar characteristics, which is one of the sectors that consume the most energy worldwide.

<p>The copper rotor induction motor (CURIM) was recently introduced because it has lower rotor fusion losses than the aluminum rotor (ALRIM). Furthermore, with CURIM, it is easier to reach IE4 and IE5 efficiency levels. The CURIM is advantageous for compact motors, escalators, and electric vehicle applications. However, CURIMs present slip, power factor, temperature increase, and torque decrease problems that must be analyzed. This study compared the economic feasibility of using CURIM with ALRIM by applying discount techniques. A case study was carried out in a sugar company with a cyclical operation, where 5.5 kW motors will be installed in the intermediate conductors of the mill's feeders. The facility works three shifts between 3 and 6 months. The cost increase (DCI) of CURIM over ALRIM was between 1.1 and 1.5 times. With 3,600 h/year and 4,000 h/year of operation, the DCI greater than 10%, it was found that the payback is more than four years, and the net present value (NPV) grows linearly.</p>

Abstract Different methods have been developed to estimate the energy efficiency of induction motors. The accuracy of these methods vary with the load factor, the unbalanced voltage (UV) and harmonics. The feasibility of these methods for efficiency estimation in real-time were theoretically and experimentally assessed during the operation under different operational conditions (i.e. balanced sinusoidal voltage (BSV), harmonics, UV and harmonics with UV). Results show that for load factors over 80%, the air-gap method is applicable under any condition, while the slip method is only applicable under BSV or balanced harmonic voltage. Moreover, for load factors over 40%, the nameplate method is applicable under BSV. Other methods result in errors over 8% and optimization methods are not applicable for real-time monitoring. Electric systems generally operates with some degree of UV and harmonics, while induction motors mostly operate with load factors below 60%, limiting the use of these methods for real-time measurement.

This paper presents the application of a method to determine the output power, losses, and efficiency of induction motors, working in no-controlled conditions, in the presences of unbalanced and harmonics voltages. The method uses the steady state equivalent circuits, with some considerations for the analysis of motor performance, fed with unbalanced and harmonic voltages. The parameters of circuits are determined with low invasiveness, by applying a Bacterial Foraging Algorithm as technique of evolutionary search. With this, the efficiency and other operational parameters can be estimated at any operating point. The method was tested in a 12.6 kW motor working in an industrial network, with harmonics and voltage unbalanced.

Improving and managing the electricity efficiency in hotel facilities is essential to reduce the hotel operation costs and its environmental impacts. The data presented shows the evolution of the electricity consumption and management between 2013 and 2015 in two hotel facilities in Cuba (one beach hotel and one city hotel). The data additionally includes the daily measures used to develop control tools for an energy management system. The data presented in the article relates to the research study: Tools to improve forecasting and control of the electricity consumption in hotels Cabello et al., 2016, and it corresponds to the energy audits developed in one beach hotel (Hotel A) and one city hotel (Hotel B) in Cuba.

Microgrids have been proposed as a solution to the growing deterioration of traditional electrical power systems and the energy transition towards renewable sources. One of the most important aspects of the efficient operation of a microgrid is its topology, that is, how the components are connected. Some papers have studied microgrid topologies; however, these studies do not perform an exhaustive analysis of the types of topologies, their applications, characteristics, or technical advantages and disadvantages. The contribution of this paper is the integration of the most important functional properties of microgrid topologies in terms of reliability, efficiency, structure, costs, and control methods. The study analyzes 21 topologies divided into six classifications with their respective sub-classifications. The analysis was based on the characteristics of the current (AC or DC), the control mechanisms, the transition between the operating modes, and the operating costs. As a result of the evaluation, it was evidenced that SST-based completely isolated coupled AC topologies, completely isolated two-stage AC decoupled, and multiple microgrids show the best performances. In contrast, the use of two-stage and three-stage partially isolated AC decoupled topologies is not recommended because of their high operating cost and low efficiency and reliability.