Abstract

The pipeline blockage increases the resistance of water distribution networks. In this study, a new method based on machine learning was proposed to locate the blocked pipeline. Numerous block scenarios were simulated by the hydraulic simulation, considering various block sizes and user demands for each pipeline. The dataset of the pressure change rates on the nodes was used to train artificial neural network models. The influences of the dataset variables on the model performance were analyzed. Results showed that the proposed method can successfully locate the blocked pipeline using the measurement of one day.

Abstract

The mechanism researches on seabed methane fate are a critical part to reveal the global methane budget. Hydrate formation by natural gas bubbles in the course of seepage is an essential way for methane capture and fixation. Nevertheless, the hydrate phase equilibrium characteristics that affect the stability of hydrate formation during the bubble ebullition process are unclear. “Haima” cold seep is a typical active methane seeping environment associated with abundant methane hydrate, which necessitates unveiling the stability of methane hydrate formation. This work investigated the hydrate phase equilibrium conditions based on the in-situ water depth and practical ion categories and salinity. The results show that the strength of inhibition of methane hydrate in chloride salts of 3.45wt% salinity was in the order of Mg2+ > Na+ > Ca2+ > K+, Mg2+ > Ca2+ > Mn2+ > Ba2+. The mechanism of different ions categories effect on hydrate equilibria can be elucidated by the difference of charge and radius of the ions. Hydrate phase transition enthalpies was calculated by the Clausius-Clapeyron equation. The response law of hydrate phase transition enthalpy was almost consistent with the phase equilibrium change. This work have important reference value for the mechanism exploration about how hydrate formation characteristic is influenced by ions in “Haima” cold seep environment.

Abstract

The open centre turbine can be easily installed with a kite-like mooring system. It is promising to harvest the renewable marine resources due to its higher energy conversion efficiency, lower cost, and minimum impacts on the submarine environment. However, multi-devices deployment is still a great challenge due to the interaction between the mutual wakes. This work deals with the wake morphology and the multi-device configuration by applying the Computational Fluid Dynamic analysis. A fully resolved model reveals that most of the turbulence affects the wake within 2D axial distance (twice the turbine diameter), with a maximum radial amplitude of 1.6R. In the axial direction, after 2D, due to an induced “suction effect” by the annular geometry, the wake takes a cylindrical shape. For a 2 turbines array, a wheelbase of 2.5D and an interplane of 5D allow keeping the devices’ performances constant.

Abstract

This paper proposes a fault recovery strategy for AC/DC hybrid distribution networks (HDNs) to restore critical loads in face of extreme events, in which the flexible topology with islanding partition is integrated for multi-source synergy. The island partition-based recovery model maximizes the active power of restored loads as the objective function while considering the power flow constraints, radial topology constraints, and multiple sources’ constraints. Then, the proposed model is transformed into a mixed-integer second-order cone programming (MISOCP) formulation by linearization and convex relaxation, which can be solved effectively. Finally, the effectiveness of the proposed service restoration method is validated on a modified IEEE 33-node AC/DC test feeder.

Abstract

A quantitative energy supply system toward a Zero Carbon (herein after abbreviated as ZC) society in 2030 and 2050 derived from our design platform has been developed. Furthermore, the relationships between GDP and CO2 emissions have been clarified quantitatively under the various conditions by applying our proprietary system with the integration of newly developed input-output table and above-mentioned energy supply system. CO2 emissions from daily life field can approach ZC relatively easily by using the ZC power supply. However, it is not easy to reduce COâ‚‚ emissions from the manufacturing field to zero. The relationships between GDP and CO2 emissions in 2050 shall strongly depend on the industrial and social structure. By changing these structures under different conditions, the pathways to a bright future ZC society could be visualized.

Abstract

Internal combustion Rankine cycle (ICRC) with oxy-fuel is a novel concept to achieve zero carbon emission in theory due to the carbon dioxide capture system, and nitrogen oxides can be completely eliminated as intake of air is replaced by oxygen. In previous studies, traditional compression ignition engine coupled with ICRC system (CI-ICRC) shows great potential in brake thermal efficiency (BTE), emission characteristics and cycle performance through direct water injection (DWI). Since the CI-ICRC has been proved a feasible way to realize high efficiency and low emissions, a self-designed CI-ICRC prototype engines was established, series of experiments have been conducted focusing on the optimization of CI-ICRC engine including oxygen content, DWI temperature, DWI timing, etc. In this study, to further determine optimum DWI strategy, the effect of DWI pressure on cycle performance and emissions characteristics has been investigate. According to experimental results, under 320℃A DWI timing and constant mass of injected water, higher DWI pressure with shorter DWI pulse width reduces the direct impact of vapor on combustion so that shorter ignition delay and less HC emissions are obtained. With the increase of DWI pressure, the cycle performance and BTE of CI-ICRC prototype engine is improved due to the better atomization of water. The optimum BTE achieved within the prototype engine is 46.6%, with coefficient of variation close to 1% under 35MPa DWI pressure. But the NOX and soot emissions slightly increased as elevating DWI pressure. The experimental results can also be utilized in providing reference information for DWI utilization within other novel internal combustion engine concepts.

Abstract

With the development of renewable energy and the advancement of electric heating projects, the stable operation of grid has been affected. In this paper, LA is used as an auxiliary service provider to study the scheduling strategy for multiple time scales in thermal demand response. Then, a case verifies the effectiveness of the strategy. Through intraday or real-time scheduling, the load can be effectively reduced by 16.61% and 15.53%, and 406.5MWh and 405.9MWh of abandoned wind power were consumed respectively. All participants can benefit from both scheduling strategies. However, shortening the scheduling time interval cannot achieve better results in thermal demand response scheduling.

Abstract

Here we compare the biomass feedstock use, net CO2 emission, and cumulative radiative forcing of passenger cars and cargo trucks powered by different energy pathways. We consider the full lifecycle of the vehicles, including manufacture and operation. Our system boundaries include all fossil and biogenic emissions from technical systems, and the avoided decay emissions from harvest residue left in the forest. We find that the pathways using bioelectricity to power battery electric vehicles have strongly lower climate impacts, compared to the liquid-fuelled internal combustion pathways using biomethanol, DME, gasoline or diesel. The pathways using bioelectricity with carbon capture and storage (CCS) result in negative emissions leading to global cooling. These findings suggest that accelerating the current trend toward vehicle electrification, together with scaling up renewable electricity generation, is a wise strategy for climate-adapted transport.

Abstract

By the end of the century, all countries must reduce carbon dioxide emissions to zero. As a result of deep decarbonization and the highest greenhouse gas emissions pathways, this study examines the effects of climate change on our planet. It is necessary to build renewable power plants in order to keep the global temperature well below 2 centigrade degrees. Despite this, building new renewable power plants costs almost twice as much as stranded fossil fuel power plants. Based on different emission reduction targets, this study compares the costs of different mitigation strategies. When comparing mitigation strategies, indirect consequences such as socioeconomic costs and environmental costs should be taken into account.

Abstract

In this work, a numerical study is conducted to investigate the effects of hybrid nanofluid (Al2O3-Cu/water) on the thermal and hydraulic performance of a three-dimensional double-layer counterflow microchannel heat sink. The heat sink comprises a silicon block to which a constant heat flux of q = 1.0 MW/m2 is applied at the base. Different volume concentrations of alumina and copper nanoparticles are considered, with the Reynolds number varying between 200 and 1000. The conjugate heat transfer problem is solved numerically using the two-phase Eulerian-Eulerian model in ANSYS – Fluent environment. Experimental validation shows a good agreement between the numerical models and the experiment. Nanofluids exhibit higher heat transfer coefficients and pressure drops than the base fluid; however, nanoparticle hybridization has a minimal effect on the pressure drop.