Energy management in microgrids with renewable energy sources: A literature review

Renewable energy sources have emerged as an alternative to meet the growing demand for energy, mitigate climate change, and contribute to sustainable development. The integration of these systems is carried out in a distributed manner via microgrid systems; this provides a set of technological solutions that allows information exchange between the consumers and the distributed generation centers, which implies that they need to be managed optimally. Energy management in microgrids is defined as an information and control system that provides the necessary functionality, which ensures that both the generation and distribution systems supply energy at minimal operational costs. This paper presents a literature review of energy management in microgrid systems using renewable energies, along with a comparative analysis of the different optimization objectives, constraints, solution approaches, and simulation tools applied to both the interconnected and isolated microgrids. To manage the intermittent nature of renewable energy, energy storage technology is considered to be an attractive option due to increased technological maturity, energy density, and capability of providing grid services such as frequency response. Finally, future directions on predictive modeling mainly for energy storage systems are also proposed

Sizing stand-alone hybrid generation for seasonal irrigation pumping

Abstract. This paper studies the generation to feed three stand-alone existing pumping systems in the province of Zaragoza (Spain), in the same area but with different consumption and irrigation needs. All of them are used only for half the year. We look for the optimal size of the generation mix, both economically and in reducing emissions. For simulation and optimization the program used is HOGA (Hybrid Optimization by Genetic Algorithms). It is considered diesel generation, photovoltaic and wind as well as storage. As renewable resources are almost identical in the three locations, the magnitude of energy demand and schedule are the distinctive parameters of each facility. We considered how to choose the optimum angle of the PV array, the preference between the solar and wind and the desirability of whether or not the diesel generator. The results show the importance of seasonality and time consumption profile to determine the generation mix and to choose the optimum inclination of the field of photovoltaic conversion. Results also show that most emissions reductions are not always obtained by removing the genset

Optimizing daily operation of battery energy storage systems under real-time pricing schemes

Modernization of electricity networks is currently being carried out using the concept of the smart grid; hence, the active participation of end-user consumers and distributed generators will be allowed in order to increase system efficiency and renewable power accommodation. In this context, this paper proposes a comprehensive methodology to optimally control lead-acid batteries operating under dynamic pricing schemes in both independent and aggregated ways, taking into account the effects of the charge controller operation, the variable efficiency of the power converter, and the maximum capacity of the electricity network. A genetic algorithm is used to solve the optimization problem in which the daily net cost is minimized. The effectiveness and computational efficiency of the proposed methodology is illustrated using real data from the Spanish electricity market during 2014 and 2015 in order to evaluate the effects of forecasting error of energy prices, observing an important reduction in the estimated benefit as a result of both factors: 1) forecasting error and 2) power system limitations

Utilization of synthetically generated hourly wind speed data in the optimization of Wind-Batteries stand-alone systems

Abstract. This paper shows a study of the influence of the type of wind data in the optimization of Wind-Batteries standalone systems. We have considered two types of input data for the wind speed: 1) measured wind speed hourly data for a whole year and 2) monthly average wind speed data. When using the second type of data, we generate synthetically the hourly wind speed data of the year, and we force a certain number of consecutive days of "calmness" (in this case wind speed lower than 3 m/s) in the month of most time of calmness (generally December or January in Zaragoza). The results show that, using monthly average wind speed data, if the number of consecutive days of forced calmness is adequate, the optimal system found by the optimization tool is the same as the one obtained using the measured wind speed hourly data. Thus, the method of generating wind speed hourly data synthetically is validated to be used in the optimization of Wind-Hybrid systems

Energy arbitrage in PV-PHS systems

In this paper, we use MHOGA software for the evaluation of adding pumped hydro storage (PHS) for energy arbitrage in utility-scale PV generating systems. PHS is used for electricity price arbitrage, pumping water from the lower reservoir to the upper reservoir with the PV generation during hours of low electricity price and generating electricity by means of the stored water with the turbine during hours of high price (during these hours the PV generator also injects its production to the grid). The control strategy creates setpoints for the use of the pump and the turbine, trying to obtain the maximum benefits from the electricity sold to the grid, maximizing the net present value (NPV). An example of application is shown, obtaining conclusions about the economical viability of the PV-PHS system compared to the PV-only system: in the case studied in this work, it is not worth to add PHS to the PV system

Escenografía virtual de bajo coste para la docencia online [Low-cost virtual scenography for online teaching]

La escenografía virtual se está aplicando desde hace años en películas y en programas de televisión, logrando una sustancial mejora en la comunicación con los espectadores así como una reducción en los costes de producción. Un ejemplo es la sección del tiempo en los informativos de televisión, donde haciendo uso de croma key la persona que aparece en pantalla parece tener detrás un mapa, aunque el mapa realmente no está ahí. En el ámbito de la docencia tiene una clara aplicabilidad, y en algunas Universidades ya disponen de instalaciones en las que los docentes pueden preparar y grabar presentaciones para docencia online haciendo uso de escenografía virtual. Dadas las características y requisitos de las presentaciones docentes, en este artículo se presenta un sistema de bajo coste y portable cuyo objetivo es, fundamentalmente, la realización de presentaciones para la docencia online utilizando escenografía virtual, incluyendo la presentación de algunas de las herramientas informáticas que pueden utilizarse para la grabación de los vídeos y su posterior edición. [The virtual scenography has been applied for years in films and television programs, achieving a substantial improvement in communication with viewers as well as a reduction in production costs. An example is the weather section in television news, where using chroma key the person appearing on the screen seems to have a map behind, although the map is not really there. In the field of teaching has a clear applicability, and in some universities already have facilities in which teachers can prepare and record presentations for online teaching using virtual scenography. Considering the characteristics and requirements of teaching presentations, this article presents a low cost and portable system whose main objective is to make presentations for online teaching using virtual scenography, including the presentation of some of the computer tools that can be used for video recording and subsequent editing.

Electricity price arbitrage in utility-scale PV-plus-battery systems

In this paper, we use MHOGA software for the optimization of an AC-coupled utility-scale PV-plus-battery system. Batteries are used for price arbitrage, being charged with the photovoltaic (PV) generation during hours of low electricity price and discharged during hours of high price. The correct estimation of the battery lifetime has great importance in the calculation of the net present value, to do this advanced models for estimating the Li-ion battery lifetime (considering cycle and calendar ageing) are used. With present components costs, considering the Spanish SPOT price of 2021 with an expected increase of 1% annual, the AC coupled utility-scale PV-plusbattery isn’t economically viable comparing to the PV-only system. If electricity hourly price was multiplied by two, in certain cases adding battery to the PV system would be profitable

Utility-scale renewable hydrogen generation by wind turbines

In this paper, we use MHOGA software for the evaluation of a hydrogen generation system powered by wind turbines. We study the state of the art of the electrolyzers, obtaining the most important characteristics and costs of PEM electrolyzers. The optimization of a Wind-H2 system is performed, obtaining the best combination of components (wind turbines and electrolyzer) and control strategy for the hydrogen production. We will compare to the Wind-only system (wind farm which injects all the electricity produced to the gird). Two cases have been evaluated regarding the electricity price: Spanish SPOT price of 2019 and of 2021, with an expected increase of 1% annual. The Wind-H2 system can be competitive to the Wind-only system if the hydrogen sale price is 4.8 €/kg for the case of 2019 SPOT prices and 6.7 €/kg for the case of 2021 SPOT prices, considering 1% annual increase in the SPOT prices and 2% for the hydrogen price

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Propuestas para un aprendizaje activo y autónomo de estudios de ingeniería

El Espacio Europeo de Educación Superior (EEES) es una gran oportunidad para cambiar los viejos modelos de docencia en la universidad, centrados generalmente en la clase magistral. En este trabajo se propone una metodología, centrada en el estudiante, que elimina o reduce sustancialmente la clase magistral, aumentando la interacción del estudiante con el grupo y con el profesor, haciendo énfasis en el trabajo previo a las clases, así como en el aprendizaje basado en problemas (ABP) y en un planteamiento que acerca los contenidos al mundo profesiona