Abstract

Liquid organic hydrogen carriers (LOHCs) have taken a spotlight as a possible alternative for hydrogen (H2) storage and transportation compared to more conventional methods such as pressurized H2 and liquified H2. In an increasingly alternative energy supply, efficiency of commercial scale H2 release from LOHC systems is paramount for a viable H2 economy. This work presents a process design for a novel process intensification strategy which combines two conventional LOHC chemicals (benzene and dibenzyl toluene) in a dehydrogenation process utilizing a shared heat source. Using rigorous Aspen Plus process simulation it has been demonstrated that this process design allows for an increased hydrogen release yield of 18.7 %, when compared to systems which utilizes a single LOHC chemical. Strategy of temperature cascade dehydrogenation using different LOHC combinations, coupled with identification of process integration viability, specifically in utilization of waste heat can very likely prove to be an important pathway to a more efficient hydrogen economy.

Abstract

The Bohai Bay Coastal Zone is the third largest economic zone in China, with environmental problems having become a constraint to economic growth in this region. This paper first estimates the CO2 emissions in Bohai Bay Coastal Zone from 2012 to 2015. Then it constructs directional distance function and assumes two scenarios to evaluate the regional differences of carbon emission performance in this zone. The result indicates that, first of all, the CO2 emissions intensity in Bohai Bay Coastal Zone is decreasing year by year. And taking energy consumption structure as the indicator can determine CO2 emissions performance more accurately and effectively. Under the two different scenarios, Hebei, Liaoning and Shandong Province have significant differences, which mean that these provinces have great potential in CO2 emissions reduction and energy consumption structure is the key factor. While Beijing and Tianjin City, at the advanced level of CO2 emissions reduction, have shown few differences under the two scenarios. At last, it gives proposal, such as upgrading industrial structure, investing for researches of low-carbon technologies, levying carbon taxes to achieve CO2 emissions reduction goal.

Abstract

Stirling engines, especially free-piston Stirling engines (FPSE), have drawn more attention with the advantages of high thermal efficiency, constant power output, the flexibility to use any heat source as input and low noise. Acoustic impedance match is critical to the overall performances of a free-piston Stirling generator (FPSG). Based on thermos-acoustic theory, the acoustic impedance characteristics of the FPSE and the linear alternator are calculated and analyzed individually. And the acoustic impedance of the FPSE and the linear alternator are then well matched. In the calculation, the FPSG output the electric power of 6223.2 W with the thermal-to-electric efficiency of 38.3% at the heating temperature of 900 K. The acoustic match approach would be helpful for designing FPSGs.

Abstract

In this paper, a novel approach is proposed to build model for a multi-heterogeneous energy power generation system(MHEPGS) including wind power, solar power and hydro power. The exergy flux, exergy flow potential, exergy flow potential difference and exergy resistance are firstly defined based on exergy theory. The exergy equivalent model for the MHEPGS is constituted by exergy source series with the exergy resistance, which are represented by exergy flow potential and exergy resistance from the angle of force and resistance. Result show that the equivalent exergy model can correctly reflect the output of the MHEPGS.

Abstract

Line loss in power distribution system occupies one fifth to one quarter of the total power loss in power systems. Different from the line loss in transmission system, distribution line loss is closely related to the load characteristics and economic types of power users. And the proportion of line loss caused by management problems is significant. Hence the traditional physical model of line loss is not suitable for distribution line loss analysis. To analyze line loss of low-voltage distribution system accurately, a big-data method based on MSApriori association rule mining algorithm is proposed in this paper. Based on the operational data of more than 20,000 distribution stations and the detailed data of 1.8 million power users in Shanghai, a line loss analysis method based on big data is proposed in this paper. The relationship between the line loss and its influencing factors is analyzed from the perspectives of user type, user number, power supply volume, reactive power shortage, and transformer type. The association factors obtained from the analysis are helpful to further guide the reduction of line loss.

Abstract

Organic Rankine Cycles are a promising technology to generate power from low temperature heat sources and can therefore help to transform current energy systems into renewable ones. However, ORCs are often affected by a broad range of operating conditions; therefore detailed component models are required for the design process. This work validates a semi-empirical model of a twin-screw expander with experimental data from an Organic Rankine Cycle test rig. The results show a satisfying accuracy of the model.

Abstract

Fractured vuggy carbonate reservoirs usually develop several large-scale caves which are the main storage space of oil-gas. The volume and position of caves are important parameters for production guidance, but there are no effective well test methods of calculating the cave volume of multi-cave reservoirs yet. This paper establishes a multi fracture-vug composite model for fractured vuggy carbonate reservoirs, divides reservoirs into a couple of fracture-vug seepage zones according to the cave distribution, establishes a mathematical model through the coupling of seepage zones, and then obtains analytical solutions of the mathematical model using dimensionless and Laplace transformation. By plotting the standard log-log type curves, this paper analyzes the flow characteristics of the model. It is found that the pressure derivative of the inter-porosity flow segment from caves to fractures is presented as a V-shaped concave, the pressure and pressure derivative curves at the fracture flow segment take on the parallel lines with the slope of 0.5. A parameter sensitivity analysis indicates: the bigger the cave is, the steeper the V-shaped concave goes; the farther the distance between cave and wellbore is, the more hysteretic the V-shaped concave becomes. Finally, the triple fracture-vug model is applied to fit the buildup pressure data of well T40. We calculate that the volumes of cave 1 and cave 2 are 7489 m3 and 56324 m3 , the cave distances are 25.1m and 189.2m respectively.

Abstract

A system for methane hydrate-bearing sediment detection with pressure is designed, series of experiments for compressional wave response of hydrate-bearing sands are performed systematically in laboratory. Considering the difficulties in performing valid laboratory tests and in recovering intact hydrate bearing sediment samples. The system is designed to achieve in situ hydrate formation in bearing sediments and synchronous acoustic detection and signal analysis. The hydrate formation unit comprises a pressure chamber which is designed for pressure core analysis, a high-precision pump for gas injection. The ultrasonic test unit consists of a pulse transceiver, an A/D converter, an ultrasonic transducer, a signal amplifier and an oscilloscope. The influence factors, including hydrate saturation and formation process to P-wave velocity (Vp) and amplitude are investigated. The results show that Vp and amplitude both increase with the hydrate saturation. Vp exhibit relatively minor changes when hydrate saturation varies from 0% to 40% compared to the P-wave amplitude. However, there is a close relationship between the velocity of P-wave and the saturation of hydrate which could be the effective criterion for the hydrate formation in bearing sediments.

Abstract

Thermochemical energy storage (TCES) is a novel heat storage technology with high heat storage density and capability of large-scale energy storage for a long time. This work describes a composite material which has improved mechanical and reaction properties based on Ca(OH)2/CaO heat storage system. Heavy tar was used as a binder of CaO particles. The mechanical and heat transfer properties of the composite are enhanced due to the matrix carbon structure produced by tar calcination. The most suitable material (tar content of 15 wt%, calcinated in N2 at 850 °C) was tested for 30 dehydration/ hydration cycles. The cyclic test shows that the composite has good mechanical and reaction properties with a crushing strength value of > 11 N and molar hydration conversion of > 90 % after 30 cycles.

Abstract

The fuel cell is actually an energy conversion device which converts Gibbs free energy of reactants into electrical energy. And the remaining enthalpy changes and chemical overpotential loss will generate a lot of heat. However, the performance of fuel cell is strongly dependent on the operation temperature, therefore it is necessary to maintain the thermal balance of the whole system. This paper presents a graphical thermal model of proton exchange membrane fuel cell system based on energetic macroscopic representation and the thermal balance is analyzed using power chain. Then, the EMR-based control methodology is used to manage the operation temperature using inversion rules. Finally, the model is validated by MATLAB/Simulation.