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The electro-hydraulic servo pump control system (EHSPCS) is a volume control system that uses a permanent magnet synchronous motor (PMSM) with a fixed displacement pump to directly drive and control the hydraulic cylinder. The energy transmission law of the system is very complicated due to the transformation of electrical, mechanical and hydraulic energy as well as other energy fields, and qualitative analysis of the energy transfer efficiency is difficult. Energy transfer analysis of the EHSPCS under different working conditions and loads is proposed in this paper. First, the energy flow transfer mechanism was analyzed, and the mathematical and energy transfer models of the key components of the system were established to explore the energy characteristic state transition rule. Second, a power bond diagram model was built, its state equation and state matrix were deduced, and a system simulation model was built. Finally, combined with the EHSPCS experimental platform, simulation experiments were carried out on the dynamic position following and steady-state position holding conditions of the system, and the variation rules of the power of each energy characteristic state and the system energy transfer efficiency under different loads were obtained. The research results provide a foundation for the study of power matching and energy-saving mechanism of the EHSPCS.

As a relatively mature technology, biomass molded fuel (BMF) is widely used in distributed and centralized heating in China and has received considerable government attention. Although many BFM incentive policies have been developed, decreased domestic traditional fuel prices in China have caused BMF to lose its economic viability and new policy recommendations are needed to stimulate this industry. The present study built a regionalized net present value (NPV) model based on real production process simulation to test the impacts of each policy factor. The calculations showed that BMF production costs vary remarkably between regions, with the cost of agricultural briquette fuel (ABF) ranging from 86 US dollar per metric ton (USD/t) to 110 (USD/t), while that of woody pellet fuel (WPF) varies from 122 USD/t to 154 USD/t. The largest part of BMF’s cost composition is feedstock, which accounts for up 50%–60% of the total; accordingly a feedstock subsidy is the most effective policy factor, but in consideration of policy implementation, it would be better to use a production subsidy. For ABF, the optimal product subsidy varies from 26 USD/t to 57 USD/t among different regions of China, while for WPF, the range is 36 USD/t to 75 USD/t. Based on the data, a regional BMF development strategy is also proposed in this study.

We analyzed the peak spring tidal current speeds, annual mean tidal power densities ( T P D ) and annual energy production ( A E P ) obtained from experiment 06.1, referred as the “HYCOM model” throughout, of the three dimensional (3D), global model HYCOM in an area covering the Baja California Pacific and the Gulf of California. The HYCOM model is forced with astronomical tides and surface winds alone, and therefore is particularly suitable to assess the tidal current and wind-driven current contribution to in-stream energy resources. We find two areas within the Gulf of California, one in the Great Island Region and one in the Upper Gulf of California, where peak spring tidal flows reach speeds of 1.1 m per second. Second to fifth-generation tidal stream devices would be suitable for deployment in these two areas, which are very similar in terms of tidal in-stream energy resources. However, they are also very different in terms of sediment type and range in water depth, posing different challenges for in-stream technologies. The highest mean T P D value when excluding TPDs equal or less than 50 W m−2 (corresponding to the minimum velocity threshold for energy production) is of 172.8 W m−2, and is found near the town of San Felipe, at (lat lon) = (31.006–114.64); here energy would be produced during 39.00% of the time. Finally, wind-driven currents contribute very little to the mean T P D and the total A E P . Therefore, the device, the grid, and any energy storage plans need to take into account the periodic tidal current fluctuations, for optimal exploitation of the resources.

Car-sharing services are developing at an ever-increasing pace. Taking into account the reduction of carbon dioxide emissions and pursuit of the sustainable development of transport, implementing electric cars in car-sharing fleets is being proposed. On the one hand, these types of vehicles are referred to as emission-free, but on the other hand, their environmental friendliness is questionable due to the emission of carbon dioxide during the production of energy to power them. Although many scientific papers are devoted to the issue of reducing emissions through car sharing, there is a research gap concerning the real production of carbon dioxide by car-sharing vehicles during car-sharing trips. To fill this research gap, the objective of the article was to analyze the actual level of carbon dioxide emissions from combustion and electric vehicles from car-sharing systems produced when renting rides. The test results showed that the electric car turned out to be significantly less emitting. The use of electric vehicles in car-sharing fleets can reduce carbon dioxide emissions from 14% to 65% compared to using cars with internal combustion engines. However, the key role during car-sharing trips is played by the driving style of the drivers, which has been omitted from the literature to date. This should be properly regulated by service providers and focus on the proper use of energy from electric vehicle batteries, especially at low temperatures. The article provides support for operators planning to modernize their fleet of vehicles and fills the research gap concerning car-sharing emissions.

Lowering the amount of excess air is believed to increase the density of the air-fuel mixture and help improve the combustion rate for compression ignition engines. This paper proposes an approach of adding a throttle body at the intake pipe to control the excess air ratio with reduction of air supply to achieve a better balance between the power, emissions and fuel efficiency at medium and low load of a natural gas dual-fuel diesel engine converted from a conventional diesel engine. Various experiments in both pure diesel and dual-fuel mode under intermediate engine speed are performed with the proposed critical method of excess air ratio control. The experimental results reveal that better excess air ratio is very beneficial for the power output and brake specific energy consumption in dual-fuel combustion under medium and low load conditions. Moreover, the substitution rate can reach as high as 40% under low load conditions with throttle control.

The properties of brushless DC motor (BLDCM) are similar to the fractional, slot-concentrated winding of permanent-magnet synchronous machines, and they fit well for electric vehicle application. However, BLDCM still suffers from the high commutation torque ripple in the case of the traditional square-wave current control (SWC) method, where the current vector rotates asynchronously with back-EMF. A current optimizing control (COC) method for BLDCM is proposed in the paper to minimize the commutation torque ripple. The trajectories of the three phase currents are planned by the given torque and the optimized result of the copper loss and motor torque equations. The properties of COC are analyzed and compared with that of SWC in the stationary reference frame. The results show that the way of making the current vector rotate synchronously with back-EMF (back-Electromotive Force) can minimize the modulus and velocity of the current vector in the commutation region, and reduce the torque ripple. Experimental tests obtained from an 82 W BLDCM are done to confirm the theoretical findings.

It is critical and challenging to develop high performance transition metal phosphides (TMPs) electrocatalysts for oxygen evolution reaction (OER) to address fossil energy shortages. Herein, we report the synthesis of Co2P embedded in N-doped porous carbon (Co2P@N-C) via a facile one-step strategy. The obtained catalyst exhibits a lower overpotential of 352 mV for OER at a current density of 10 mA cm−2 and a small Tafel slope of 84.6 mV dec−1, with long-time reliable stability. The excellent electrocatalytic performance of Co2P@N-C can be mainly owed to the synergistic effect between the Co2P and highly conductive N-C substrate, which not only affords rich exposed active sites but also promotes faster charge transfer, thus significantly promoting OER process. This work presents a promising and industrially applicable synthetic strategy for the rational design of high performance nonnoble metal electrocatalysts with enhanced OER performance.

Energy storage technology plays a significant role in the pursuit of the high-quality development of the electricity market. Many regions in China have issued policies and regulations of different intensities for promoting the popularization of the energy storage industry. Based on a variety of initial conditions of different regions, this paper explores the evolutionary process of electricity market players considering energy storage technology. The trilateral evolutionary game model is adopted to analyze the strategies of the power plant, the power grid, and the government. After assigning the model according to an actual situation, each equilibrium point corresponds to a real electricity market situation. The results indicate the following: (1) In the process of stabilizing, the role of “Advanced Imitators” leading the strategy of building energy storage changes between the power plant and the power grid. (2) In Eastern, Middle, and Southern China, the power plants and power grids on a greater-than-medium scale will choose to build energy storage without governmental regulations, due to the abundant net profit. (3) In the northeast of China, power plants with a medium-or-lower scale will choose not to build energy storage because of the relatively low on-grid price, and small power grids can make enough profits by operating energy storage facilities. (4) In Northern China, the large power plants and the medium power grids will choose to build energy storage due to the high electricity sale price and the resulting high profit. (5) In Western China, the small power plants and power grids cannot afford to build energy storage due to the low electricity price. The results lead to valuable policy suggestions for the local governments of China in promoting energy storage in the future. To meet the goal of energy storage popularization, regional electricity market plans need relevant policies based on its existing conditions, offering suitable external conditions for adding energy storage.