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The goal of this Master thesis project was to design a methodology that helps to analyze a set of indicators that can support the decision-making process, by identifying energy strategies with a temporal horizon 2030-2050 in Cuba. Several sources of data and methodologies were used to fulfill the objective. The energy planning model created by Madrazo during her Ph.D. thesis was used as the main tool in this project. The hourly demand and the wind and solar capacity factors have been used as input data for this model. A post-processing module was created in R code, with the objective of analyzing the behavior of the six technical indicators that the model offers as output. The Principal Component Analysis (PCA) method was used as an exploratory method to identify cluster that later allowed studying in detail the particular characteristics of these indicators. Different graphics were used to visualize the performance of the technical indicators under different conditions, which allows us to propose the best energy strategies to ensure a secure and sustainable energy transition. The methods of “Levelized cost of energy” (LCOE) and the costs associated with the "engineering process design" allowed to assess the economic feasibility of some scenarios of energy transition identified as interesting for decision making. The current cost of the Cuban electro-energetic system was estimated and compared with the costs obtained for future scenarios simulated. After analyzing the behavior of the indicators in detail, it was identified as the most suitable transition scenario for Cuba, where 150% demand is covered by 90% intermittent energy and 10% wind energy. Also, no backup will be required under these conditions, which represents a considerable saving from the current costs required by an electric generation with fossil resources. The energy storage needs will be 0.05 TWh, and the “concrete towers” and “VOSS” technologies can be used in order to minimize installation and operation costs of these facilities.

This study assesses factors that utilities must address when they integrate intermittent renewable technologies into their power-supply systems; it also reviews the literature in this area and has a bibliography containing more than 350 listings. Three topics are covered: (1) interface (hardware and design-related interconnection), (2) operability/stability, and (3) planning. This study finds that several commonly held perceptions regarding integration of intermittent renewable energy technologies are not valid. Among fmdings of the study are the following: (1) hardware and system design advances have eliminated most concerns about interface, (2) cost penalties have not occurred at low to moderate penetration levels (and high levels am feasible); and (3) intermittent renewable energy technologies can have capacity values. Obstacles still interfering with intermittent renewable technologies are also indentified.

Planning electricity supply is important because power demand continues to increase while there is a concomitant desire to increase reliance on renewable sources. Extant research pays particular attention to highly variable, low-carbon energy sources such as wind and small-scale hydroelectric power. Models generally employ only a simple load levelling technique, ensuring that generation meets demand in every period. The current research considers the power transmission system as well as load levelling. A network model is developed to simulate the integration of highly variable non-dispatchable power into an electrical grid that relies on traditional generation sources, while remaining within the network’s operating constraints. The model minimizes a quadratic cost function over two periods of 336 hours, with periods representing low (summer) and high (winter) demand, subject to various linear constraints. The model is numerically solved using Matlab and GAMS software environments. Results indicate that, even for a grid heavily dependent on hydroelectricity, the addition of wind power can create difficulties, with system costs increasing with wind penetration, sometimes significantly.

With the increasing share of renewable sources in the energy mix, there is a need to balance energy production from weather-dependent sources, such as wind turbines and photovoltaics. This is also a current global trend associated with climate policy. In Poland, there has been a significant increase in energy production from renewable sources, leading to a duck curve phenomenon mainly in the case of photovoltaics, which requires balancing this production through various measures. One possible way to achieve this is energy storage installation. This article identifies the need for energy storage to ensure the stability of electricity production from low-flexibility sources like coal-based power plants. For this purpose, a methodology has been developed to determine the daily minimum energy storage capacities which would also allow for the integration of other stable (though less flexible) energy sources, such as nuclear power. In the case of Poland, energy storage has been estimated to require, as a median value, approximately 6 GWh of additional storage capacity, which is equivalent to twice the planned capacity of the Młoty Pumped Storage Power Plant.

Renewable energy sources (RESs) such as wind and solar are frequently hit by fluctuations due to, for example, insufficient wind or sunshine. Energy storage technologies (ESTs) mitigate the problem by storing excess energy generated and then making it accessible on demand. While there are various EST studies, the literature remains isolated and dated. The comparison of the characteristics of ESTs and their potential applications is also short. This paper fills this gap. Using selected criteria, it identifies key ESTs and provides an updated review of the literature on ESTs and their application potential to the renewable energy sector. The critical review shows a high potential application for Li-ion batteries and most fit to mitigate the fluctuation of RESs in utility grid integration sector. However, for Li-ion batteries to be fully adopted in the RESs utility grid integration, their cost needs to be reduced.

As a research result, characteristic indicators of the efficiency of using various heat sources in combined heat supply systems were determined. During the study, various schemes for integrating heat accumulators in heat supply systems were considered. Water was used as a battery, which also acts as a coolant. Mathematical modeling of processes in combined heat supply systems using intermittent heating is carried out. The characteristic operating modes of the elements of heat supply systems that take into account the operating modes of heat consumers are determined. Mathematical modeling was carried out using a software package that allows to obtain the distribution of heat power of the heat supply system by its main elements and its characteristic operation modes. According to the research results, a coefficient of thermal power reduction and a coefficient of efficiency of using the heat accumulator volume were proposed. These coefficients allow to evaluate the efficiency of heat sources and the efficiency of using the volume of the heat storage tank. Based on the obtained data, the task was set to optimize the daily load of the heat source, taking into account the installation of the storage tank. The research results can be used for the reconstruction of heat supply systems of buildings with a two-period operation mode (operation duty) using both traditional and renewable heat sources. This will significantly increase the efficiency of the use of elements of the heat supply system, even out the daily heat generation schedule and increase the service life of the main equipment

An economic and environmental evaluation of active distribution networks containing lithium ion batteries (Li-ion), sodium sulfur batteries (NaS) and vanadium redox flow batteries (VRB) was carried out using the EnergyPLAN software. The prioritization schemes of the combination of energy storage systems and intermittent energy systems were studied technically and economically based on some specific situations of the grid integrated with wind power. The results suggest that the technical and economic optimal intermittent energy-storage capacity ratio was 2:1 in predetermined energy system scenarios. Li-ion batteries storage system performed the best in critical excess electricity production (CEEP) absorption, energy saving and emission reduction while NaS batteries storage system was the most competitive among the three due to its cheaper costs.

A new architecture of the inverter used in the convertion of electric energy generated by renewable energy sources is studied in this paper. The distinctive features of this inverter is the special block which compensates pulsing of the current with double frequency, characteristic for these inverters. The switching of electronic keys is realized using the method TCM In this block, like in the inverter, which assures the switching at the voltages near to zero (ZVC). The proposed algorithm of controlling the electronic keys permits to increase the work frequency up to hundreds of kHz. Electronic keys operate at variable frequency, which changes during the work cycle both slowly and by jump. The assurance of admissible heat regime is performed using forced cooling air flux and by convection. The increase of releasing process of the heat is assured by original construction of radiators which forms the turbulent mode of cooling air flux. These changes of the architecture of the inverter have allowed the minimization of mass, sizes and price indicators. It has been manufactured a functional laboratory sample with output power of 2kW the voltage of direct current of 450V or 48 V and output alternating voltage of 230V, with sizes 175mmX35mmX30mm.