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[en] The steam condensation on the inside wall of containment and film evaporation on the outside wall of containment are very important phenomena during passive containment cooling system (PCS) heat removal process. The GOTHIC8.0 code was used to simulate condensation and evaporation heat removal processes in this paper. The code prediction results were compared and evaluated based on experimental data of condensation and evaporation tests. The results show that the condensation model in GOTHIC can simulate steam condensation heat transfer process quite well. The film evaporation rate from GOTHIC model is lower than that from evaporation test. Although GOTHIC model is conservative to analyze containment response during design benchmark accident, it is suggested that further work should focus on making code development to better simulate film evaporation phenomenon. (authors)
[en] Highlights: • It solves the problem of maritime spatio-temporal forecasting for the first time. • A new method EEMD-SOM-BP is proposed for maritime forecasting of solar irradiation. • An asymmetric four-parallel structure of SOM is proposed to mine data features. • Three experiments are performed to determine the optimal settings of EEMD-SOM-BP. - Abstract: Owing to a shortage of fossil fuels and environmental pollution, renewable energy is gradually replacing fossil fuels in the power systems of hybrid ships. To exploit fully solar energy by the successful day-ahead scheduling of ships, this work proposes a new day-ahead spatio-temporal forecasting method. Ensemble empirical mode decomposition (EEMD) is used to extract data features and decompose original historical data into several frequency bands. After the original data are processed, data from the four land weather stations that are closest to the ship and self-organizing map-back propagation (SOM-BP) hybrid neural networks are used to forecast the solar radiation received by the ship in the next 24 h. Multiple comparative experiments are implemented. The results show that the EEMD-SOM-BP spatio-temporal forecasting method can accurately forecast the solar radiation on a ship that is sailing along a navigation route.
[en] Highlights: • Methods is outlined to improve the efficiency of heat-induced solar thermionic converter. • Optimization of materials and structure is summarized for photon-enhanced thermionic converter. • Combined systems with thermionic energy converters is proposed for concentrating solar power. • Roadmap of thermionic energy conversion for concentrating solar power is brought forward. - Abstract: Concentrating solar power (CSP) is a mainstream of solar energy utilization, and thermionic emission is a potential way to convert concentrated solar radiation into power with a theoretical efficiency of 50–70%, surpassing both Shockley-Queisser limit and photo-thermal limit. This literature attempts to provide a comprehensive understanding of and an insight into solar thermionic energy conversion. The fundamentals of electron emission from electrodes and electron transport in vacuum gap are presented, as well as the state of the art of solar thermionic energy conversion technologies, including heat-induced thermionics and photon-enhanced thermionics. The former is driven by thermal energy, whereas the latter takes advantage of both quantum photon energy and thermal energy. Burgeoning research indicates that photon-enhanced thermionic conversion is a promising technology for concentrating solar power due to the high efficiency and simple operating mode. Now, it is important to develop novel materials and coating technologies to facilitate electron emission and reduce space charge effect in interelectrode vacuum. Structural design of thermionic converters and top–bottom configuration of solar-electricity systems are suggested for practical applications.
[en] Highlights: • The energy output characteristics of the solar hybrid CCHP system are defined in a clear perspective. • The particle swarm optimization (PSO) algorithm is adopted to find the optimum design parameters. • The design features and the performance of solar hybrid systems under five different operation strategies are analyzed. • The comparison between the hybrid system and the conventional system is given. - Abstract: The hybridization between conventional combined cooling heating and power (CCHP) systems and solar systems has been considered as a good solution to the urgent energy and environment issues. This study develops the mathematical model of a CCHP system hybridized with PV panels and solar thermal collectors. The particle swarm optimization (PSO) algorithm is adopted to find the optimum values of design parameters. Based on the energy output characteristic of the solar hybrid CCHP system, five operation strategies of the conventional CCHP system are adjusted and applied for the solar hybrid CCHP system. The simulation work of the hybrid CCHP systems based upon a hotel building in Atlanta is carried out to find an appropriate design scheme. The results show that the hybrid CCHP system under the FEL-ECR mode is the best choice. Besides, its PESR, CO2ERR and ATCSR can reach 36.15%, 53.73% and 4.16%, respectively. Compared with a conventional CCHP system, the hybrid CCHP system achieves better energy-saving and CO2 reduction performance. However, the hybrid CCHP system consumes more annual total costs because of its high initial investment.
[en] The increasing demand for electricity has pushed more effort to focus on renewable energy sources to satisfy the consumer. The renewable energy sources are playing a major role in the generation of electricity. Out of all the renewable energy sources, solar has emerged as one of the best sources of energy since it is clean, inexhaustible and eco-friendly. However, the voltage generated by the solar cell is not sufficient for any consumer load and it is also variable. Therefore, it is necessary to implement DCDC converters for regulating and improving the output voltage of the solar panel. In order to extract the maximum output from the PV (Photovoltaic) panel, a comparative analysis of various MPPT (Maximum Power Point Tracking) algorithms is proposed in this paper. The proposed enhanced adaptive P and O(Perturb and Observe) algorithm is modeled and implemented with a high gain DC-DC converter. The converter investigated in this paper consists of a single power electronic switch (MOSFET) for its operation, which leads to reduction of switching and conduction losses. The proposed converter has less ripple content and a high conversion ratio. A simulation study of the proposed power electronic converter powered by PV source is carried out in MATLAB/SIMULINK and the results are validated using an experimental setup. (author)
[en] Highlights: • Integration model is first proposed for dynamic temperature distribution of DHN. • A new integrated heat and power dispatch for wind power integration is proposed. • Integration model is embedded into the IHPD to truly use thermal inertia of DHN. • Stored heat and heat storage rate of DHN are quantitatively calculated. • Supply and return temperature at HS are optimised for operation regulation of DHS. - Abstract: Utilizing the thermal inertia of a district heating network (DHN) for thermal storage is considered an effective energy-saving method for improving the operational flexibility of combined heat and power (CHP) generation units for wind power integration in an integrated heat and power dispatch (IHPD) system. However, to truly utilize the thermal inertia of the DHN, the supply and return temperatures at the heat source are both necessary to regulate the district heating system (DHS) for wind power integration, whereas the heat output of CHP is not able to do that. Therefore, a new IHPD model that considers the thermal inertia of the DHN was formulated to improve the flexibility of CHP units for wind power integration, in which the first proposed integration model was used to completely simulate the dynamic temperature distribution of the DHS. The optimised supply and return temperatures at the heat source were then obtained to guide the operation regulation of DHS for wind power integration in actual engineering applications. Moreover, the stored thermal energy and the thermal storage rate of the DHN were quantitatively calculated to determine the thermal state of DHN. To analyse the effects of the proposed IHPD model, the approach was compared with a conventional heat and power dispatch model through a case study based on a real DHS. The results demonstrate the advantages of the proposed model in terms of wind power integration, energy saving and operation regulation of DHS.
[en] Power systems are currently facing several issues in order to evolve and integrate less carbon-heavy, and potentially more local, production. Prospective model-based analysis is a precious tool for exploring the possible long-term developments of these systems and comparing their advantages and disadvantages. However, to ensure relevance, it is important to reconcile the spatial and temporal phenomena that occur at various scales. Power system management depends on constantly maintaining a complex supply-demand balance. Meeting this challenge requires anticipating demand variations and power plant availability, combined with regulation systems to resolve remaining discrepancies. These regulations are activated in from a few seconds up to several hours. On shorter timescales, power systems show inherent robustness: the power grid creates an electromagnetic coupling between synchronous machines allowing them to share their inertia. This inertia, which takes the form of kinetic energy, is instantaneously available to face natural demand or supply fluctuations. To ensure that proposed long-term scenarios are consistent with the robustness requirements of power systems, which enable their management, this robustness must be assessed using prospective modeling. In this work, we propose an indicator, calculable within prospective studies, which assesses power system stability, namely its ability to return to synchronism after a perturbation. This indicator is based on an aggregated description of the transportation power grid and describes the electromagnetic coupling brought by the power grid. When combined with a bottom-up model from the MARKAL/TIMES family describing the French power system, this synchronism indicator, along with another indicator quantifying the available kinetic reserve, enables us to assess the consequences of renewable penetration, especially in terms of power system robustness. (author)
[fr]Les systemes electriques evoluent actuellement vers l'integration d'une production moins carbonee, eventuellement plus locale. Afin d'explorer les evolutions possibles de ces systemes sur le long terme, l'exercice prospectif s'appuyant sur des modeles est un outil precieux. Cependant, pour etre pertinent, il doit reconcilier des phenomenes spatiaux et temporels a des echelles variees. Ainsi, le fonctionnement du systeme electrique repose sur un equilibre offre - demande a chaque instant. Afin de corriger les fluctuations de la production ou de la consommation qui surviennent necessairement, les gestionnaires de reseau mettent en place un certain nombre de regulations dont les durees d'activation sont de l'ordre de quelques secondes a quelques heures. A des echelles de temps encore plus fines le systeme electrique presente une robustesse interne: le reseau electrique cree un couplage electromagnetique entre les machines synchrones qui leur permet de mutualiser leur inertie respective. Cette inertie, qui constitue une reserve d'energie cinetique, est instantanement disponible pour faire face aux fluctuations. Pour que les scenarios de long terme proposes ne soient pas en contradiction avec les exigences de robustesse du systeme electrique, qui permettront son operation, il est necessaire que l'evaluation de cette robustesse soit integree a la modelisation prospective. Dans ce travail, nous proposons un indicateur, calculable au sein des etudes de prospective, qui evalue la stabilite d'un systeme electrique, c'esta- dire son aptitude a revenir au synchronisme suite a une perturbation. Cet indicateur repose sur une description agregee du reseau de transport et traduit le couplage electromagnetique apporte par le reseau. Associe au modele bottom-up de la famille MARKAL/TIMES decrivant le systeme electrique francais, cet indicateur de synchronisme et un indicateur quantifiant la reserve cinetique disponible, nous permet d'evaluer les consequences de la penetration du renouvelable, notamment sur la robustesse du systeme electrique. (auteur)
[en] The use of a low-power solar network and standalone power plants is the most promising for the needs of the housing and utilities sector, small industrial enterprises, social and public health facilities, recreation areas, remote objects, and agricultural industries; this will make it possible to reduce the load on the energy system at peak moments, as well as to decrease losses when transporting electric energy in its elements. It is assumed that the minimum value of the unit cost of generated electric energy is used as the criterion for configuring and selecting the parameters of solar power equipment, which will make it possible to set up an economically feasible additional power supply to the consumer, since it excludes the use of storage devices and rearrangement of the power supply system.
[en] The thermal solar energy production is a promising and strongly growing sector. However, these technologies must be integrated to electric power systems, i.e. coupled with fossil-fired or biomass-fired plants, and the energy must be stored. This production can be either centralised or decentralised: this corresponds to different situations, different markets, different technologies and equipment (rows of mirrors to concentrate solar heat on a tube, linear Fresnel reflectors to concentrate solar heat on a tube, heliostats or mirrors which concentrate heat at the top of a tower, and parabolic disks which produce electricity with a Stirling gas engine at their focal point). This road-map focuses on electric power generation, and discusses key variables of the present market, proposes a vision for 2050, identifies objectives to be reached by 2015, and barriers to be removed, outlines the needs of demonstrators and their administrative framework.