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Abstract The Renewable energy power generation capacity has been rapidly increasing in China recently. Meanwhile, the contradiction between power supply and demand is becoming increasingly more prominent due to the intermittence of renewable energies. On the other hand, on the mitigation of carbon dioxide (CO2) emissions in China needs immediate attention. Power-to-Gas (PtG), a chemical energy storage technology, can convert surplus electricity into combustible gases. Subsurface energy storage can meet the requirements of long term storage with its large capacity. This paper provides a discussion of the entire PtG energy storage technology process and the current research progress. Based on the comparative study of different geological storage schemes for synthetic methane, their respective research progress and limitations are noted. In addition, a full investigation of the distribution and implementation of global PtG and CO2 capture and storage (CCS) demonstration projects is performed. Subsequently, the opportunities and challenges of the development of this technology in China are discussed based on techno-economic and ecological effects analysis. While PtG is expected to be a revolutionary technology that will replace traditional power systems, the main issues of site selection, energy efficiency and the economy still need to be adequately addressed. Additionally, based on the comprehensive discussion of the results of the analysis, power-to-gas and subsurface energy storage implementation strategies, as well as outlook in China are presented.

The power transformer is important equipment for energy conversion and transmission in the power grid and its failure will bring significant economic losses to the power system. The hot-spot temperature is a primary factor affecting the reliability and service life of power transformers. In order to calculate the temperature distribution of oil-immersed transformer windings accurately, it is required to solve a multi-physical problem, in which the magnetic field and the fluid-temperature field are coupled. In the simulation of multi-physical field of transformer, many studies usually omit the turn-to-turn insulation of windings to simplify the oil-immersed transformer model. The purpose of this paper is to investigate the effect of the turn-to-turn insulation of windings in oil-immersed transformers on the simulation results. First, a 2D axisymmetric transformer model was established in ANSYS to study the effect of low-voltage winding turn-to-turn insulation on the magnetic field simulation results. The differences of eddy current losses in the simulation were also calculated in terms of the magnetic field simulation results. It is found that the turn-to-turn insulation does not affect the magnetic field distribution in evidence from the simulation results. Besides, the values of the magnetic field and eddy current loss appear significant differences only at both ends of the low-voltage winding. Second, the fluid-temperature field of the transformer was solved in Fluent and the turn-to-turn insulation was the controlled objective in the solution process with consideration of the difference in winding losses. The simulation results show that the turn-to-turn insulation of the winding does not change the oil flow distribution in simulation. The simulation model with turn-to-turn insulation appears a gradient in the temperature distribution of the discs and a rise in the overall temperature distribution. Moreover, this paper analyzes the possible reasons for the differences in the simulation results of the magnetic and temperature fields caused by the turn-to-turn insulation. Some results and conclusions in this paper can be used in related studies and designs.

Abstract One characteristic of railway stations in China is that the entrance hall, ticket office, integrated waiting hall and auxiliary space are all concentrated in a large span of space, forming a unified whole space. However, the multi-function fusion in such a large space results in a series of acoustic problems, such as long reverberation time, high environmental noise and poor language articulation. Therefore, it is necessary to study the acoustic environment of railway stations in China. In this study, the sound field characteristics of the typical railway station are studied to reveal its law of sound propagation. Next, subjective evaluation and objective experiments are carried out to study the acoustic environment and comfort in the waiting hall. Finally, based on the comparative analysis of various influential factors, such as sound source and sound field, this paper advances some suggestions for the acoustical design of high-speed railway stations.

Oil shale is a kind of potential alternative energy source for petroleum and has attracted the attention of energy researchers all over the world. Borehole hydraulic mining has more prominent advantages than both conventional open-pit mining and underground mining. It is very important to attempt to use the borehole hydraulic mining method to exploit underground oil shale. The nozzle is the key component of borehole hydraulic mining and reasonable mining parameters are also crucial in exploiting underground oil shale efficiently. The straight cone nozzle and the oil shale of Huadian area will be taken as the research objects. The self-developed, multifunctional, experimental device can test both the jet’s performance as well as the breaking of oil shale by the high-pressure water jet using the straight cone nozzle and varying structural parameters. Comprehensive analysis of the results of an orthogonal experimental design, including range analysis and variance analysis, demonstrate the optimal structural parameters of a straight cone nozzle as follows: the outlet diameter is 4 mm, the length to diameter ratio is 2.5, and the contraction angle is 60°. In addition, in order to maximize the efficiency of borehole hydraulic mining for Huadian oil shale, the non-submerged jet should be placed parallel to the oil shale bedding. These results can provide scientific and valuable references for borehole hydraulic mining of oil shale.

Optimization of all numerical codes ported in the infrastructure and used for supercapacitors, PV and batteries. The scope of deliverable D3.2 is to report the new advances in the field of materials for energy that comes from the search of new methodologies and models that could be more efficient on the new generation of computer hardware for exascale. In this respect, deliverable D3.2 is a transversal deliverable that report the new advances related to activities described in task T3.2, T3.3 and T3.4. H2020

Vehicle speed prediction plays a critical role in energy management strategy (EMS). Based on the adaptive particle swarm optimization–least squares support vector machine (APSO-LSSVM) algorithm with BP neural network (BPNN), a novel closed-loop vehicle speed prediction system is proposed. The database of a vehicle internet platform was adopted to construct a speed prediction model based on the APSO-LSSVM algorithm. Furthermore, a BPNN is established according to the local high-precision nonlinear fitting relationship between the predicted value and error so as to correct the prediction value. Then, the results are returned to the APSO-LSSVM model for calculating the minimum fitness function, thus obtaining a closed-loop prediction system. Finally, equivalent fuel consumption minimization strategy (ECMS) based EMS was performed. According to the simulation results, the RMSE performance is 0.831 km/h within 5 s, which is over 20% higher than other performances. Additionally, the training time is 15 min within 5 s, which is advantageous over BPNN. Furthermore, fuel consumption increases by 6.95% compared with the dynamic-programming algorithm and decreased by 5.6%~10.9% compared with the low accuracy of speed prediction. Overall, the proposed method is crucial for optimizing EMS as it is not only effective in improving prediction accuracy but also capable of reducing training time.

In order to mitigate the power density shortage of current energy storage systems (ESSs) in pure electric vehicles (PEVs or EVs), a hybrid ESS (HESS), which consists of a battery and a supercapacitor, is considered in this research. Due to the use of the two ESSs, an energy management should be carried out for the HESS. An optimal energy management strategy is proposed based on the Pontryagin's minimum principle in this research, which instantaneously distributes the required propulsion power to the two ESSs during the vehicle's propulsion and also instantaneously allocates the regenerative braking energy to the two ESSs during the vehicle's braking. The objective of the proposed energy management strategy is to minimize the electricity usage of the EV and meanwhile to maximize the battery lifetime. A simulation study is conducted for the proposed energy management strategy and also for a rule-based energy management strategy. The simulation results show that the proposed strategy saves electricity compared to the rule-based strategy and the single ESS case for the three typical driving cycles studied in this research. Meantime, the proposed strategy has the effect of prolonging the battery lifetime compared to the other two cases.

Abstract Heat pipes have been extensively applied in the domain of energy conversion and heat recovery application. A novel radial heat pipe with internally finned condenser has been proposed to recover waste heat from air conditioning units. Full mathematical description and computational fluid dynamics model were developed to predict the loop flow and thermal performance in a single radial heat pipe, respectively. The research focuses mainly on the effects of input power, filling ratio, pipe diameter, and velocity of the cooling water on the thermal performance and entropy generation rate of this novel heat pipe. Numerical results illustrate that average reductions in total thermal resistance with utilization of fins approximately achieved 8.69% and 14.78% for fins nf = 4 and nf = 8, respectively. Similarly, entropy generation rate shows an average decrease of 19.4% and 37.5% for identical operations. Additionally, the effect of internally finned condenser on the multiphase fluid flow has been comprehensively analyzed, including the break of the condensed film, generation of bubbles and nucleation boiling. The results further indicate that incorporation of internal fins has a significant influence on enhancing thermal homogenization and waste thermal recovery efficiency of a radial heat pipe. Case results agreed well with experimental data within average deviation being no more than 10%.