• Energy Research
• Restricted close
• engineering and technology close
• IR close
• CA close

Abstract The kinetics of methane hydrate decomposition was studied using a semibatch stirred-tank reactor. The decomposition was accomplished by reducing the pressure on a hydrate slurry in water to a value below the three-phase equilibrium pressure at the reactor temperature. The data were obtained at temperatures from 274 to 283 K and pressures from 0.17 to 6.97 MPa. The stirring rates were high enough to eliminate mass-transfer effects. Analysis of the data indicated that the decomposition rate was proportional to the particle surface area and to the difference in the fugacity of methane at the equilibrium pressure and the decomposition pressure. The proportionality constant showed an Arrhenius temperature dependence. An estimate of the hydrate particle diameters in the experiments permitted the development of an intrinsic model for the kinetics of hydrate decomposition.

Abstract Thermal energy storage (TES) systems are growing to a relevant role in solar cooling applications. Hence, high energy density is a desirable property of the TES system. Phase change materials (PCM) helps to increase this characteristic. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly of three parts: heating system, cooling system, and different storage tanks. Two identical storage tanks based on the shell-and-tubes heat exchanger, one of them including 196 squared fins in the bundle of the tubes and the other without, were experimentally tested. Hydroquinone was selected as the storage material, having a latent heat of 205 kJ/kg and a phase change temperature between 168 and 173 °C. The aim of this paper is to test experimentally, and compare the average effectiveness of the TES systems analyzed using PCM for solar cooling and refrigeration applications. It was found out that for the same tank configurations (shell-and-tubes) even changing drastically the dimensions of the tank or the number and the diameter of the tubes, the average effectiveness curve proposed in the literature fits well with the results showed here.

<div class="section abstract"><div class="htmlview paragraph">The introduction of new light-duty vehicle emission limits to comply under real driving conditions (RDE) is pushing the diesel engine manufacturers to identify and improve the technologies and strategies for further emission reduction. The latest technology advancements on the after-treatment systems have permitted to achieve very low emission conformity factors over the RDE, and therefore, the biggest challenge of the diesel engine development is maintaining its competitiveness in the trade-off “CO₂-system cost” in comparison to other propulsion systems. In this regard, diesel engines can continue to play an important role, in the short-medium term, to enable cost-effective compliance of CO₂-fleet emission targets, either in conventional or hybrid propulsion systems configuration. This is especially true for large-size cars, SUVs and light commercial vehicles.</div><div class="htmlview paragraph">In this framework, a comprehensive approach covering the whole powertrain is of primary importance in order to simultaneously meet the performance, efficiency, noise and emission targets, and therefore, further development of the combustion system design and injection system represent important levers for additional improvements. For this purpose, a dedicated 0.5 dm³ single-cylinder engine has been developed and equipped with, a state-of-the-art Euro 6 combustion system, and an advanced common rail fuel injection system (FIS) offering higher flexibility in terms of injection strategy and higher quantity accuracy. Three injector nozzles with different hydraulic flow rates (HF) have been selected and employed for the overall combustion process optimization.</div><div class="htmlview paragraph">The optimization has been performed by means of an extensive DoE-based test campaign in which the engine and FIS operating parameters have been parametrized with the aim to carry out a proper combination in terms of HF and injection strategy. The results at partial load conditions evidence significant advantages in applying an advanced injection pattern, while the HF reduction can significantly improve the smoke emission and combustion noise without fuel consumption penalties. Therefore, a proper combination and optimization of the HF and injection strategy can provide low noise and engine-out smoke while maintaining the rated power performance targets.</div></div>

About 25 million tons of food go wasted or lost in Iran which has socio-economic and environmental consequences for both the country and the households. The main objective of this research is to develop a model to examine the relationship between FCM components and the amount of FW of households in Tehran city, with a focus on urban women. By means of a structural model, this study provides a novel approach to exploring relationships between the food-related behavior of urban households and waste control (n = 1197). Besides, this study is the first attempt to quantify food waste in Iran at the household level. According to the adopted self-reporting procedure, in Tehran, every consumer wastes about 27.6 kg of edible food annually. It is found that households with better food consumption management (FCM (have a lower level of food waste. Moreover, the results have proved that other determinants such as demographic factors, economic power, information use, ability, and motivation have direct and indirect significant effects on FCM as well as on the amount of food waste generation. The findings suggest that the above-mentioned determinants are crucial and should be considered when developing a strategically sustainable food waste prevention plan.

This paper presents a control method based on active disturbance rejection control (ADRC) for both the primary and secondary control layers in a hybrid DC/AC microgrid (MG). A DC bus inside MG includes a wind turbine generator, photovoltaic panels, a fuel cell and battery energy storage. Maintaining the DC link voltage under various scenarios is made possible by applying an energy management system (EMS) based on the deviation in the state of charge of the battery and using a fuel cell as a backup. Through a voltage source inverter, the DC bus of the MG is connected to the AC side, which supplies AC loads. Using the proposed ADRC-based control strategy for the inverter, the voltage, frequency, and power flow within the MG would be effectively controlled. In order to demonstrate the effectiveness of the proposed method, a comparison between the ADRC and PI controller has also been implemented in different scenarios, proving the superiority of the suggested controller over classical approaches.

Investigations show that most simulations on solar parabolic trough collectors reported in the literature are one-dimensional or at least with a variety of simplifications. Indeed, for this collector type, due to the complex heat transfer elements as well as two-phase flow through the tubes, etc., such simplifications make the model fail to give an acceptable estimation of the circumferential temperature distribution of the walls, thermal stresses, heat losses, vapor volume fraction, etc. In this article, a detailed three-dimensional numerical modeling of solar parabolic trough collectors is presented. The results of this model are also compared to those given by an axisymmetric model and a one-dimensional nodal model to highlight the impacts of such a rigorous model on the accuracy of the final results. The results demonstrated that although the axisymmetric and nodal models show acceptable accuracy in predicting the temperature and enthalpy for the flow, they are quite incapable of precisely calculating the vapor volume fraction and heat loss rates. The discrepancy in the distribution of vapor volume fraction in different sections of the absorber tube causes significant temperature heterogeneity in the solid walls.

A control technique of multilevel converter topologies based on Direct Lyapunov Control method is presented in this paper for integration of Distributed Generation (DG) resources into the power grid. The compensation of instantaneous variations in the reference current components in ac-side and dc-voltage variations of cascaded capacitors in dc-side of the interfacing system are considered properly, which is the main contribution and novelty of this work in comparison with other control strategies. The proposed control technique provides the continuous injection of active power in fundamental frequency from DG sources to the grid. In addition, reactive power and harmonic current components of loads are provided with a fast dynamic response; thereby, achieving sinusoidal grid currents in phase with load voltages, while the required power from load side is more than the maximum capacity of interfaced converter, is possible. Simulation results confirm the effectiveness of the proposed control strategy in DG technology during dynamic and steady-state operating conditions.

Electric vehicles (EVs) are considered a substitute for fossil-fueled vehicles due to rising fossil fuel prices and accompanying environmental concerns, and their use is predicted to increase dramatically shortly. However, the widespread use of EVs and their large-scale integration into the energy system will present several operational and technological hurdles. In the energy industry, an innovative solution known as the EVs smart parking lot (SPL) is introduced to handle EV charging and discharging electricity and energy supply challenges. This paper investigates social equity access and mobile charging stations (MCSs) for EVs, where the owner of MCSs is the EV parking lot. Accordingly, a new self-scheduling model for SPLs is presented in this paper that incorporates scheduling of the MCSs as temporary charging infrastructures while considering social equity access and optimizes SPL energy generation and storage schedule. The main objectives of this research are to (i) develop MCSs accessibility measures and quantify the equity impacts of MCSs locations by modeling prioritized demand based on several indices; (ii) determine the optimal set-points of SPL components (i.e., combined heat and power (CHP), photovoltaic system, electrical and heat-energy storage, and MCSs) to manage electrical peak demand and to maximize the economic benefits of SPLs. Results indicate that the proposed demand prioritization function model can meet the required EV charging demands for prioritized events, and the self-scheduling model for SPLs satisfies the charging demand of the EVs in the SPL location. Also, the social equity access to the EV charging stations is satisfied by analyzing the operation of MCSs around the prioritized demand of the prioritized events and social equity access indices.