Abstract

The performance of membraneless microfluidic fuel cells can be predominated by the air‐breathing cathode, making it essential to understand the effect of nano‐ and micro‐structures on the oxygen transport and reaction. For the first time, pore‐scale Lattice Boltzmann Method (LBM) models have been developed to simulate the oxygen transport in air-breathing cathode based on reconstructed structures. The underneath electrolyte microchannel is also considered. A modified LBM model is used to handle the numerical instability caused by large diffusivity ratio (104) between the gaseous and dissolved oxygen. The oxygen is found to penetrate into the microchannel. The distribution of oxygen and reaction rate suggest the nano‐ and micro‐structures can affect the oxygen transport and electrochemical reaction.

Abstract

Climate change, energy security, and individual communities increasingly necessitate using urban modeling and management systems in handling complex challenges of emergent and connected systems. Urban Systems Design attempts to address these issues as a comprehensive framework which can simultaneously evaluate the important metrics of resilience, economy, sustainability, and human well-being. Building upon the Urban Systems Design framework, our study explores different ways of studying scaled problems, evaluation, energy supply and demand, and how best to employ these methods, using the Sumida Ward of Tokyo, Japan as a test case. The proposed evaluation methods can be utilized by city planners and citizens to diagnose existing characteristics of an urban area and to better decide between options for transforming it.

Abstract

Injections of pressurized carbon dioxide in natural gas hydrates have attracted a number of attentions because it can simultaneously serve as a means of methane gas exploitation and greenhouse gas sequestration. It has been found that gas recovery could be significantly enhanced by adding small molecules gases such as nitrogen or hydrogen into injected gas mixture. In this work, the Raman spectroscopy, gas chromatography and charge coupled device were used to study the effect of injecting small molecule gases on the methane hydrate decomposition.

Abstract

CO2 capture and utilization (CCU) technology has been widely adopted to reduce the greenhouse effect. The emerging chemical looping technology applied in the syngas production and gas-solid separation process has attracted widespread attention. In this research, a novel combined chemical looping reforming (CLR) process with CCU is realized in one system with CaO and Fe2O3 as the CO2 and oxygen carriers, respectively. The effects of operating parameters (i.e. Fe2O3/Al2O3 weight ratio, CO2 carrier feed ratio, CH4 feed concentration and reforming temperature) on the reforming performance are investigated through the experiments in a fixed bed reactor. The results show that these operating factors have significant impacts on the reforming reactivity. 2.5 times of CaCO3 simulation amount has the lowest CO2 releasing, 60wt% Fe/Al material obtains the highest H2 and syngas yields, 4.5% CH4 is beneficial for maintaining higher and more stable CH4 conversion and syngas purity, and 850 oC seems to be more suitable for combined CLR. The interaction between oxygen carrier and CO2 carrier is identified and discussed. The optimization for the operating conditions of this combined CLR process would provide an alternate pathway for efficient and clean syngas production.

Abstract

The SUD Provence-Alpes-Côte d’Azur Region in southern France recently redefined its objectives concerning the decarbonization of its territory and especially of its energy system as a response to guidelines specified in different national climate-energy laws and plans, which establish targets to reach a low-carbon scenario by 2050. Thus, a TIMES-SUDPACA bottom-up optimization model representing the energy sector of Région SUD was developed in order to analyze the impact that these policies might have, and to propose alternative policies that might lead the region to achieving its energy transition. The decarbonization of Région SUD presents different challenges than for the rest of France, such as risks to the electricity supply due to a nonlooped electricity grid that affects the east of the region, and a high level of renewable potential, but low local energy production. The first results from the model show that with the use of available local renewable resources and a reduction in demand, decarbonization of Région SUD might be possible for some sectors, such as residential and commercial, but that the energy transition of the transport sector will require more accurate policies.

Abstract

The integration of large scale wind farms has brought new challenges to the transient stability assessment (TSA) problem and difficult measurement of data results in fewer samples. In order to assess the state of the system in the case of small sample data, a deep residual learning (DRL) algorithm that can train deeper neural networks to avoid gradient vanish and gradient explosion is proposed. Firstly, the original input features are constructed by using the data to describe the dynamic characteristics of the power system. Secondly, the DRL trained is applied to the TSA problem. Finally, Compared with the plain convolutional neural networks, the proposed DRL achieves the higher accuracy, moreover, it has the highest unstable F1-score and stable F1-score. Case studies on the modified IEEE New England 39-bus system with wind farms integration exhibit the effectiveness of the proposed algorithm.

Abstract

Assessing marginal abatement costs (MAC) of emissions can help a firm to mitigate emissions costeffectively. This study proposes a method to evaluate MAC, which combines strengths of bottom-up engineering methods and top-down economy-wide methods. A parametric directional distance function is employed to estimate MAC from economic perspective, and the abatement level is further incorporated to generate increasing curves, which is similar to the outcomes derived from engineering perspective. This method takes into consideration whether abatement level exceeds abatement potential with current production technologies so as to provide a more realistic estimation of MAC curve. The technique is illustrated through estimating carbon emission marginal abatement cost of petroleum processing and coking industry.

Abstract

The existing distribution system of Ethiopia has encountered frequent power outages. During this outage, the critical load of most firms in the country is supplied by diesel fuel. This study examines the feasibility of integrating solar PV system into an existing unreliable grid/diesel generator system for supplying the critical load of Kombolcha Industry Park (11°5′0″ N, 39° 44′ 0″ E), Ethiopia. The work was begun by collecting the load data, grid outage and meteorological data of the study site. Then, optimal design, modeling and techno-economic analysis of grid connected PV/diesel system has been carried out using HOMER Pro optimization software by exploring three different scenarios. Results showed that grid/PV/diesel systems are technically, economically and environmentally feasible for the selected location with the cost of energy 0.048 $/kWh. It is also found that the emissions in the optimized grid/PV/diesel systems for the locations decreased by 46%, compared to the existing grid/diesel system. This study will provide a helpful awareness to the concerned stakeholders and policy makers to implement gridconnected PV systems in the north central part of Ethiopia.

Abstract

Electric vehicle (EV) is an important demand response resource, which can optimize the operation of power grid by load shifting and vehicle to grid (V2G). Effective assessment of EV response capability is of great significance for optimizing grid operation and improving grid safety. Therefore, this paper proposes an EV response capability assessment method considering EV user’s demand. Firstly, the state of EV when plugged in is calculated based on trip chain. Then, an EV charging strategy is used to minimize load variance, considering EV user’s demand. Finally, the degree of EV charging demand relaxation and an EV response capability assessment method considering EV user’s demand are proposed. Case studies on power-transportation coupling system containing RBTS Bus6 and Beijing transportation system show that the proposed EV response capability assessment method is effective.

Abstract

Ethiopia is currently moving forward with various projects to raise the power generation capacity in the country. The progress observed in the recent years indicates this fact clearly and indisputably. The rural electrification program, the modernization of the power transmission system, and the development of wind farms are some worth mentioning. It is well known, wind power is globally embraced as one of the most important sources of energy mainly for its environmentally friendly characteristics, and also that once it is installed it is a source available free of charge. However, integration of wind power plant with an existing network has many challenges that need to be given serious attention. In Ethiopia a number of wind farms are either installed or under construction with a series of them are in plan to be erected in the near future. Ashegoda Wind farm (13°2’N, 39°6’E), which is the subject of this study, is the first large scale wind farm under construction with the capacity of 120 MW. The first phase of the 120 MW, which is 30 MW has been completed and is expected to be connected to the grid soon. This paper is concerned with the investigation of the wind farm interaction with national grid under transient operating condition. The main concern is the fault ride-through (FRT) capability of the system when the grid voltage drops to exceedingly low values because of short circuit fault and also the active and reactive power behavior of wind turbines after the fault is cleared. On the wind turbine side, a detailed dynamic modelling of variable speed wind turbine of a 1 MW capacity running with a squirrel cage induction generator and full-scale power electronics converters is done and analyzed using simulation software DIgSILENT PowerFactory. On the Ethiopian Electric Power Corporation side, after having collected sufficient data for the analysis, the grid network is modeled. In the model, FRT capability of the plant is studied by applying 3-phase short circuit on the grid terminal near the wind farm. The results show that the wind farm can ride from voltage deep within short time and the active and reactive power performance of the wind farm is also promising.