A numerical study on effects of the injection direction of the pilot diesel fuel on combustion and emissions under two-stroke dual-fuel marine engine-like conditions is presented in this paper. It is found that the injection direction of the pilot fuel has significant effects on the methane start of combustion as well as flame propagation direction which leads to different heat transfer trends to combustion chamber walls and flame-wall interaction. Furthermore, the injection direction of the pilot fuel changes the methane combustion intensity which leads to different trends for emission formation.
In the context of the expansion of the scale of electric vehicles and the increase in renewable energy generation, smart orderly charging of electric vehicles is an effective means to improve economic and environmental benefits. Smart orderly charging of electric vehicles can not only reduce the impact of electric vehicle charging on the grid but also provide new dispatching resources for power system regulation, thereby avoiding the waste of large amounts of renewable resources, and reducing users’ charging costs and related investments in the power sector. Therefore, this paper focuses on the analysis of the basic elements of the implementation of smart orderly charging of electric vehicles, the research composition of smart orderly charging, and the smart orderly charging incentive measures based on demand-side management. The result that first identifies the user groups and characteristics of smart orderly charging of electric vehicles, and divides its business model into two stages. Secondly, the important components of the research on smart orderly charging are highlighted, such as the determination of influencing factors and the selection of charging load forecasting methods. Thirdly, smart orderly charging incentive measures based on demand-side management is proposed in terms of technology and economy, etc. And the last section summarizes the paper and looks forward to future research directions.
Collective intelligence (CI) is a form of distributed intelligence emerging from collaborative problem solving and decision making. It has the advantages of simple communication and less need of data transfer and computationally extensive central decision making systems. This work implements CI in demand side management (DSM) of a hypothetical urban area in Stockholm, created based on the representative residential buildings in the city. A simple platform and algorithm are developed for modelling CI-DSM, considering the timescales of 15min for communication and applying or disapplying adaptation measures. According to the results, CI increases the autonomy of the system and decreases the heating demand of buildings effectively, consequently increasing the demand flexibility based on climate conditions. CI results in decreasing the energy demand considerably, decreasing the total heating demand over a year by around 50%.
For the purpose of effective utilization of hot dry rock resource, a double-stage Organic Rankine Cycle (ORC) power generation system is established in present work. Six kinds of organic working fluids are selected for thermodynamic calculation. The results indicate that the evaporation temperature of double-stage ORC system affects performance parameters of system. Compared with single-stage ORC system, double-stage ORC system can improve net output power by 8.44% to 12.20%. The thermal efficiency of double-stage ORC system reduces maximally by 0.81%. The results also show that exergy efficiency is related to the type of organic working fluids. The organic working fluid flow in double-stage ORC is higher than that in single-stage ORC. When R601, R601a and R600 are used as working fluids, the required mass flow rate is small. The double-stage ORC system can effectively reduce the outlet temperature of heat source in the evaporator, ranging from 12.51 to 14.07â„ƒ.
In the utilization of hot dry rock, the temperature of hot dry rock production well will vary with running time. A thermodynamic model of serial Organic Rankine Cycle (ORC) is established in present work. According to specific selection criteria, six kinds of organic working mediums are selected for calculation. The parameters such as thermal efficiency, net output power, exergy efficiency and working medium flow are obtained. The results indicate that when dry hot rock injection well temperature is constant, dry hot rock production well temperature decreases with the increase of running time, which causes descend of thermal efficiency, net output power, exergy efficiency and working medium flow of serial ORC system. As value of k (ratio of temperature difference (inlet and outlet of heat source) in HT-stage ORC evaporator to temperature difference (inlet and outlet of heat source) in serial ORC system) rises, thermal efficiency, net output power, and exergy efficiency of serial ORC system firstly rise and then decrease, but working medium flow firstly descends and then rises. Maximum thermal efficiency, net output power, exergy efficiency and minimum working medium flow are obtained under the same k. By comparing the 6 selected organic working mediums, R600 presents the better thermodynamic performance.
A higher penetration of renewable energy poses challenges to the operation of the power system. However, compared with the traditional power flow analysis, dynamic power flow models are more realistic. On the other hand, though the holomorphic embedding (HE) method and its variants, such as the fast and flexible holomorphic embedding method (FFHE) have shown a great potential in the traditional power flow analysis, there is no research on the dynamic power flow based on the HE method. Therefore, this paper proposes a dynamic power flow model considering the primary frequency regulation based on the FFHE method, which is based on the HE method but shows a better performance than the original HE method. The case study shows that the proposed model can obtain a dynamic power flow solution with the same accuracy as the result obtained from the Newton Raphson iteration, and the calculation efficiency is higher.
The diesel methanol dual fuel (DMDF) engine is confronting with the problem of high unregulated emissions of methanol and formaldehyde, although it has better fuel consumption and lower regulated emissions. The previous studies on unregulated emissions of DMDF engine have focused on the measuring methanol and formaldehyde concentrations in the exhaust without distinguishing whether emissions come from leakage during valve overlap or incomplete combustion in the cylinder. In this study, a multi-dimensional computation fluid dynamics (CFD) model coupled with detailed chemical kinetic mechanism was developed to investigate the emissions of methanol and formaldehyde in DMDF engine by using CONVERGE. The model was validated against at 50% load of 1340r/min in a six-cylinder DMDF engine. The results show that the unburned methanol and formaldehyde in the cylinder are the main component of the total methanol and formaldehyde emissions, while the leakage of methanol can be negligible. This is due to the high air fuel ratio in the intake manifold and the low air inflow during the valve overlap period. Then the effects of different intake valve opening (IVO) and exhaust valve closing (EVC) on the unregulated emissions were investigated. It was found that increased valve overlap period can affected the leakage of methanol significantly. However, the increased leaking methanol still was negligible due to the very small mass ratio. Based on the above results, the total methanol and formaldehyde emissions of DMDF engine are hardly affected by the leakage of methanol, but are almost entirely derived from the unburned methanol and formaldehyde in the cylinder.
In this study the economic analysis of a 9kW variable speed compressor-based air source heat pump (ASHP) has been carried out. The HP system, developed with an aim to meet typical UK household heating demand for retrofitting application, was tested in the lab as per BSEN14511 standards at various constant definite heat load under steady state conditions. The thermodynamic performance of the HP is presented at nominal value of 9kW. The test house seasonal heating load demand was fulfilled at three constant water supply temperature (WST) of 35 oC, 45 oC, and 55 oC and the HP seasonal electric power consumption, cost, and carbon emissions were calculated. The HP average efficiency at supply temperatures of 35 oC, 45 oC, and 55 oC over the same ambient temperature conditions was found to be 363%, 291%, and 212% for meeting the house load demand completely by varying operating compressor speed. A comparative study of cost, carbon emission, and energy savings with other heating technologies, i.e. gas/oil boiler, electric heater is also conducted and presented.
Performance improvement of gas-steam combined cycle cogeneration (GSCCC) system has huge potential for energy conservation but puzzles researchers due to the implicitly coupled properties. Through the thermo-electric analogy method, this contribution builds the heat current model of a HRPG system and derives its heat transfer and conversion constraints. Benefiting from the heat current model, the linear topology equations could be separated from implicit nonlinear constraints, and hence a more stable hierarchical solution scheme for system simulation is developed. On this basis, the reasonable matching relation between parameters under off-design working conditions is achieved using the genetic algorithm. Experiment results with energy management platform shows the gas consumption could be decreased by 0.45%.
This study highlights the bio-based production of 2,3-butanediol (2,3-BDO) using a newly isolated strain for the bioconversion of organosolv-pretreated empty fruit bunches (EFB) of oil palm. The microbially produced 2,3-BDO has been considered similar in functionality and a more sustainable chemical than fossil-based chemical (1,4-BDO). As diol pretreated lignocellulosic biomass is hemicellulose-free and rapidly hydrolyzable, EFB was successfully converted into 40 g/L 2,3-BDO with 0.48 g/g-glucan (96% of the maximum theoretical yield). In addition, a comparative energy assessment revealed that 2,3-BDO bioproduction consumed >50 MJ/kg energy from the biomass, which was equivalent to the fossil energy consumption of 1,4-BDO industrial production but 39% reduced GHG emissions than the conventional processes. This finding demonstrates the cost-effectiveness and eco-friendly features for 2,3-BDO production using waste biomass derived from the exiting industry. Principally, by recycling the produced 2,3-BDO for replacing the used pre-treatment reagent (organosolv), the biorefinery can eventually become self-sustainable without the need of additional energy and chemicals.