Abstract

Solar heating is a clean and promising way for space heating, however, the demand for low-temperature heat in non-heating seasons is very little, which also cause the extremely high cost of space heating. A flexible solar heating system is proposed in this paper, besides supplying heat in winter, it can upgrade low-temperature heat to process steam through a heat pump in nonheating seasons. The thermodynamic performance of the proposed system using in a textile mill is investigated. The system consists of a solar collector with an area of 120 m2 , a storage tank with a capacity of 50 kW and an ammonia compression-absorption heat pump with a capacity of 30 kW. The yearly natural gas saving and CO2 emission reduction of the proposed system reaches 4957.64 m3 and 5941.3 kg in total. The economic analysis turns out the investment would be recovered in 7.87 years, which is 54.13% less than that of the solar space heating system without an HP (14.17 years). Furthermore, the influences of the solar collector area, the capacity of the storage tank and heat pump on the proposed system are carried out.

Abstract

Load margin is a critical index of voltage security of power systems, which reflects the ability of maintaining system voltage stability when disturbances occur. Nowadays natural gas units (NGUs) are widely used in power system. However the gas supply and the constraints of natural gas systems (NGSs) are not considered in existing load margin determination methods of power systems. In this paper, a load margin determination method for integrated electricity-gas system (IEGS) based on continuation multi-energy flow (CMEF) is proposed. Firstly, a multi-energy flow model with IEGS security constraints is built. Secondly, a load growth parameter is introduced and added to the proposed CMEF. Then, the multi-energy flow solution curve is tracked by a prediction-correction process. Finally, the WSCC 9-bus EPSs combined with 6-node NGSs is employed as a test system to illustrate the impact of NGSs static constraints and natural gas supply on the load margin. Numerical results verify the effectiveness of the CMEF.

Abstract

Due to the inherent degradation of materials and the influence of various operating conditions such as load, temperature, and fuel supply, the health state of the solid oxide fuel cell (SOFC) will be inevitably degraded, resulting in system fault or even failure. The state of health (SOH) estimation and remaining useful life (RUL) predicition are beneficial to the maintenance of the SOFC systems, such as preventing unplanned shutdown, which is of great significance for ensuring the safety, reliability, and economy. Therefore, based on the framework of the data-driven and degradation model, this paper develops a method for SOH estimation and RUL prediction for SOFC. Finally, the framework was validated using longterm experimental data from a 1-cell stack.

Abstract

The application of diesel methanol dual fuel (DMDF) technology to diesel engines reduces nitrogen oxides (NOX) and particulate matter (PM) emissions, but increases hydrocarbons (HC), carbon monoxide (CO) and nitrogen dioxide (NO2) emissions in exhaust gas. The traditional diesel oxidation catalyst (DOC) under DMDF mode has the function to simultaneously reduce HC and CO, as well as to make NO2 be converted to nitrogen monoxide (NO). The modified DOC in this study is used to achieve high NO2 emission, which is favor for oxidation of carbon deposited on diesel particulate filter (DPF), and to improve its activity at low temperatures. All the tests were carried out on the DMDF engine bench. The effect of the property of DOC, the methanol substitution ratio (MSR), the DOC inlet temperature and the methanol dosing on the various emissions and temperature in cs16exhaust gas was studied. Results show that the addition of CeO2-ZrO2-La2O3-Pr2O3 promoters to DOC facilitates the formation of NO2 and improves its lowtemperature activity. The NO2 emission and the NO2/NOX increase as the MSR increases with the DOC inlet temperature from 170°C to 280°C. Compared to pure diesel mode, the high NO2/PM ratio after the DOC at DMDF mode means that the performance of passive regeneration for DPF can be improved. Meantime, the high exhaust temperature downstream of the DOC at DMDF mode is beneficial for the passive regeneration. But the temperature-rise of exhaust at DMDF mode is limited at high loads. The DMDF mode at low loads can improve the fuel economy caused by the active regeneration.

Abstract

Caliber ratio and caliber-depth ratio as two important structural parameters for the combustion chamber design directly affect the in-cylinder air motion and the fuel-air mixture distribution, which further influence the combustion process. This paper is presented to study the effects of these two important parameters on combustion and emission characteristics of a diesel engine. Results showed that increasing the caliber ratio increased ISFC (Indicate specific fuel consumption) value and soot emissions, while decreased the NOx emissions. A first decrease then increase trends were obtained for both ISFC and soot emissions as the increase of the caliber-depth ratio and the turning points were all located near the ratio of 4.0, which was just opposite to NOx emissions variations. In additions, for both caliber ratio and caliber-depth ratio variations, the proportions of NOx and soot emissions in the near wall region and central region were the greatest, respectively, and mainly contributed to the variations of NOx and soot emissions.

Abstract

The chemical reaction of biodiesel in combustion is more complex than traditional hydrocarbon fuels because of the existence of saturated and unsaturated fatty acid methyl or ethyl esters. In this study, a series of molecular dynamics simulation with reactive force field is performed to investigate the combustion and pyrolysis of the extensively tested biodiesel surrogate fuel, i.e., methyl butanoate. By analyzing the time dependence and spatial distribution of intermediates and stable products, the chemical reaction mechanism is elucidated. The formation of nitrogen oxides during methyl butanoate combustion under fuel-air conditions is studied for the first time by reactive force field. In the pyrolysis simulation of pure methyl butanoate, the performance of CHO-2008 and CHO-2016 is tested in terms of the transferability and capability. The reactive molecular dynamics can be employed as an effective method for chemical reaction modelling of biodiesel combustion both qualitatively and quantitatively.

Abstract

This paper deals with the feasibility of using perceptron learning model to build an empirical model for the reliability evaluation of medium voltage electrical distribution networks. The main idea is to develop a novel reliability evaluation algorithm, by training the perceptron on a restricted sample set, and replace the conventional system state evaluation methods by a simpler calculation, which can quantitatively analyze the reliability and component importance of distribution networks. The proposed approach is illustrated by case studies.

Abstract

With the development of industrial Internet of Things (IoT) for smart grid, the amount of data in end user side increases sharply. However, the digitizing also brings great possibility for energy theft. Inspired by the good performance of deep learning models and the computation efficiency of the convolutional neural network (CNN), in this work, we present a deep CNN based energy theft detector. By learning the statistical pattern in the customers’ consumption pattern, the detector is supposed to make correct classification. In reality, the whole dataset tends to have a small portion of energy theft data. To overcome such data imbalance, data of malicious consumption behavior is synthesized according to the predicted energy theft patterns. The experiment is conducted on the open source dataset. The proposed method is compared with the support vector classifier (SVC)-based method. The results show that the proposed method is more robust against the changes of non-malicious consumption behavior and can achieve better classification performance. Moreover, accelerated by GPU, the proposed method is more suitable for real time detection.

Abstract

Well-to-wheel analysis can be used to quantitatively compare the impact electric vehicles has on global warming with conventional internal combustion vehicles. In this study, we performed a well-to-wheel analysis in Korea in 2030. Furthermore, we evaluated the impact of the WTW standard from the perspective of the government, the manufacturer and the consumer. The government adjusts the penalty rate to present a new GHG standard scheme for the same amount of WTW greenhouse gases, and the vehicle market shares move from PHEVs and BEVs to HEVs and ICEVs depending on the manufacturer’s suggested retail price and consumer choice.

Abstract

A hierarchical scheduling model of a district heating system which consists of residential energy stations, heat exchange stations and heating consumers was developed in this paper. . Firstly, the optimal scheduling model of the energy station with combined heat and power (CHP) unit and the heat pumps was proposed. The optimal scheduling of the energy station is conducted to decide the output of different heating equipment of the heating system to minimize the operational cost of the energy station while meeting the varying heating loads. Secondly, the heat exchange station model was developed by utilizing the heat balance principle of the heat exchanger. Finally, a model to simulate the thermal characteristic and energy consumption of the buildings was proposed. The resistor-capacitor (RC) network is used to model the thermal characteristics of the building, in which the thermal inertia of the building and the adjustment of the radiator are considered. Consumers can take active controls on their radiators, which can both reduce the heating cost and meet their comfort requirements. Numerical studies demonstrate that the proposed strategy can contribute to the operational cost reduction of energy station and heating consumers, while guarantee the consumers’ temperature comfort level.