• Energy Research

This paper presents a dynamic droop control scheme for islanded microgrids dominated by intermittent renewable energy sources, which is able to perform desirable power sharing in the presence of renewable energy source fluctuation. First, allowable maximum power points of wind generator and PV generator are calculated in different wind speed and insolation ranges. Then, piecewise droop relationships between distributed generators are built. Finally, the dynamic droop control is proposed to perform power sharing according to wind speed and sunlight information from local sensors. The dynamic droop controller of each DG unit is activated through local logic variable inferred by wind speed and solar insolation information. Simulation results are given for validating the droop control scheme. The proposed dynamic droop scheme preserves the advantage of conventional droop control method, and provides flexibility and effectiveness in the presence of the renewable energy sources fluctuation.

The Netherlands policy on electricity steers towards a carbon neutral power generation in 2050. Among the studies that focus on long term power system research, none use the starting point of a 100% renewable power system in 2050. It is unknown if such a system is technically feasible given the variability of wind and solar. The generation patterns of intermittent renewables differ continuously, causing the remaining power sources in the system to mitigate the variable IRES generation. Additionally, it is also unknown to what extent the energy only market can incentivise investment. By using the PLEXOS electricity market model, the dispatch of CO2 low generation portfolios and the market prices and net profits of generators can be determined in various scenarios. These scenarios vary on demand changes, capacity factors for wind and solar and primary fuel prices. The results show a great sensitivity of an energy only market under the combination of a demand growth and a meteorological year of low capacity factors, resulting in blackouts and high wholesale market prices. Storage and intermittent renewables, however, do not benefit enough from a scenario with a high annual market price. ; Complex Systems Engineering and Management (CoSEM)

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.

International audience; The possibility to dry heat-sensitive timber with solar energy or residual energy from industrial processes with low exergy content, may be of double interest: the use of energy sources with very low price and the reduction of thermal pollution. The important issue when using such energies is to adapt the process control to the availability of the energy. Additionally, there is a major concern that this energy saving could be done at the detriment of drying quality or drying time. This paper proposes a numerical investigation of the possibility to use intermittent energy source to dry wood drying by comparing different strategies.

Modeling tools and technologies that will allow reaching decarbonization goals in the most cost-effective way are imperative for the transition to a climate-friendly energy system. This includes models which are able to optimize the design of energy systems with a large number of spatially distributed energy generation sources coupled with adequate short, medium, and long duration storage technologies. Solar photovoltaic and wind energy are likely to become the backbone in a future greenhouse gas neutral energy system and will require low-cost, geographically independent storage technologies in order to balance their intermittent availability. As an alternative to lithium-ion batteries and hydrogen systems, thermal energy storage coupled with a power block (e.g., Carnot batteries, pumped thermal storage, etc.) could be a promising option. Therefore, the current study aims to investigate the influence of renewable generation profiles coupled with alternate storage options (i.e., Li-ion and hydrogen cavern) on the installed capacity of electric-to-thermal-to-electric systems using a 100% renewable electricity system in Germany as a case study. The analyses reveal that Carnot batteries complement established and near-future storage technologies, as they could fill the gap between daily storage such as batteries and seasonal storage such as hydrogen salt caverns. Furthermore, Carnot Batteries could offer multiple options for heat integration further increasing their potential.

When the supply of intermittent renewable energies like wind and solar is high, the electricity price is low. Conversely, prices are high when their supply is low. This reduces the pro t potential in renewable energies and, therefore, incentives to invest in renewable capacities. Nevertheless, we show that perfect competition and dynamic pricing lead to efficient choices of renewable and fossil capacities, provided that external costs of fossils are internalized by an appropriate tax. We also investigate some properties of electricity markets with intermittent renewables and examine the market diffusion of renewables as their capacity costs fall. We show that the intermittency of renewables causes an S-shaped diffusion pattern, implying that a rapid build-up of capacities is followed by a stage of substantially slower development. While this pattern is well known from the innovation literature, the mechanism is new. Moreover, the S-shaped pattern is followed by another acceleration phase towards the end of the diffusion process. We also find that technology improvements such as better storage capabilities have substantial effects not only on the speed of market penetration, but also on its pattern. Finally, fluctuations of energy prices rise with the share of renewables. If regulators respond with a price cap, this leads to a faster market diffusion of renewables.

The purpose of this work is to quantify the energetic interest of convective and intermittent drying process of natural products. This drying mode has been achieved within a climatic blower. This laboratory device permitted us to achieve several tests for different conditions of drying for apples, carrots and peppers. This study permitted to appreciate the capacity of the model to describe the different drying periods. In the continuous case, a variation of the air velocity permitted us to find the most economic velocity for the drying of thin layer products. In the intermittent case, the numerical simulation profiles give us more information on what happens really to the product during periods of stop. Besides, the drying kinetics at the retaking increases with the air temperature. Then, we gain in energy and in global drying time.

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.

Wind energy is an increasingly important renewable resource in today’s global energy landscape. However, it faces challenges due to the unpredictable nature of wind speeds, resulting in intermittent power generation. This intermittency can disrupt power grid stability when integrating doubly fed induction generators (DFIGs). To address this challenge, we propose integrating a Li-ion battery energy storage system (BESS) with the direct current (DC) link of grid-connected DFIGs to mitigate power fluctuations caused by variable wind speed conditions. Our approach entails meticulous battery modeling, sizing, and control methods, all tailored to match the required output power of DFIG wind turbines. To demonstrate how well our Li-ion battery solution works, we have developed a MATLAB/Simulink R2022a version model. This model enables us to compare situations with and without the Li-ion battery in various operating conditions, including steady-state and dynamic transient scenarios. We also designed a buck–boost bidirectional DC-DC converter controlled by a proportional integral controller for battery charging and discharging. The battery actively monitors the DC-link voltage of the DFIG wind turbine and dynamically adjusts its stored energy in response to the voltage level. Thus, DFIG wind turbines consistently generate 1.5 MW of active power, operating with a highly efficient power factor of 1.0, indicating there is no reactive power produced. Our simulation results confirm that Li-ion batteries effectively mitigate power fluctuations in grid-connected DFIG wind turbines. As a result, Li-ion batteries enhance grid power stability and quality by absorbing or releasing power to compensate for variations in wind energy production.