Abstract

The free-piston engine linear generator (FPELG) has the high thermal efficiency and simply structure. Thus, it is investigated by many researcher groups. However, many researchers main focused on the FPELG characteristics from the simulation results. Therefore, in the paper, the piston dynamics and the combustion characteristics of the gasoline FPELG from the experimental results were investigated. The experimental results demonstrated that the piston TDC is 32.2mm, the peak velocity is 5.3m/s and the frequency is 32.8Hz. And it is found that the optimal ignition timing of the free-piston engine is between 27.5 mm and 28 mm.

Abstract

Participation in demand response (DR) has been explored for many large energy using assets based on day-ahead markets. However, little is known about the use of multiple energy markets or DR for open canal systems. In this article, we propose the use of multiple flexible energy markets to enable DR for open canal systems in the Netherlands, where many large pumping stations are used for flood mitigation. We observed that the Dutch market is not yet rewarding DR, with relatively low-priced fixed-price contracts. However, when applied to the German market scenario, a cost saving of 13% was found. In conclusion, the method of combining two flexible energy markets seems successful. However, more simulations and research are needed to explore the full potential.

Abstract

The paper presents the gas permeability of marine sediments in the Shenhu Area of South China Sea. The sediments were obtained at the depth of 1600m below sea level. The solid density and volume weighted mean diameter of the sediments were 2.421 g/cm3 and 6.491 μm, respectively. The gas permeability of the marine sediments was measured by steady state method with confining pressures of 2MPa, 5MPa, 8MPa, 10MPa, 15MPa, 20MPa, 23MPa. The effective gas permeability of the sediments decreased from 2.638 × 10-16 m2 to 0.872 × 10-16 m2 as the confining pressure increased from 2 MPa to 23 MPa. The porosity of the sediments decreased from 41.82 % to 29.54 % as the confining pressure increased from 0 to 23 MPa. The gas permeability of the sediments was determined to be 1.535 × 10-16 m2 with confining pressure of 15 MPa and the porosity of 32.00 %. The longitudinal deformation of the sample was very sensitive to the confining pressure, and the compressibility of the sample in the radial direction was not obvious. The particle size term in the classical Kozeny-Carman equation was revised by a correction factor (N), and the experimental results fitted well with the curves when N value was 2.40. The reference group experiments indicated that the measurement results were reproducible.

Abstract

CO2 capture from high operating temperatures are of special interest as it is economically appealing over low temperature CO2 capture process in Post-combustion capture. This work contributes to the estimation of new and complementary density data for CO2 confined in ‘L’ shaped carbon slit pores at high temperatures and pressures. CO2 adsorption capacities in ‘L’ shaped carbon slit pores of heights 20Å, 31.6Å, 63.2Å, 94.85Å and 126.5Å at 673.15 K and 873.15 K over a pressure range of 500 kPa to 4000 kPa are predicted by Grand Canonical Monte Carlo simulations. Elementary Physical Model is employed to model CO2 at these temperatures and pressures both in bulk and confined phase. CO2 adsorption capacities and the unique structural properties of the confined CO2 at all the condition mentioned above has been estimated in presence of the wall-fluid interactions and the fluid-fluid interactions. The Steele wall potential is used to model the wall-fluid interactions inside carbon-based adsorbents that have a slit shaped geometry.

Abstract

Solar energy driven hydrogen production has gradually become a hotspot in the study of solar energy utilization. Chemical-looping cycle provide a possibility to produce hydrogen under a lower temperature and atmospheric pressure. Here, a honeycomb reactor is proposed to make the hydrogen production process is carried out at 600 oC. Experiments are performed via an endothermic NiO reduction reaction with methane. NiO is made into porous honeycomb chambers, realizing the integration of OC and reactor. The performances of hydrogen production are experimentally examined at the methane flow rate of 300-600 ml/min. The results show that the increasing of methane inlet flow rate of the reaction can make the hydrogen production is gradually advanced. But there is an optimal value, once the flow rate is excessive, it will have an inhibitory effect on the hydrogen production. Also, methane always maintains a high conversion rate as long as the oxygen content of OC is not deficient. Additionally, 15 cycles reaction are performed. The chemical-looping cycle hydrogen production process in the honeycomb reactor is proved to be extremely stable.

Abstract

An automotive exhaust thermoelectric generator (AETEG) has a non-uniform temperature field among thermoelectric modules (TEMs), resulting in current mismatches of TEMs and lower energy output of the AETEG. In order to implement high maximum power point tracking efficiency of the AETEG, a distributed thermoelectric energy recovery system consisting of three parallel thermoelectric generators and lithium iron phosphate (LiFePO4) battery pack is proposed. In addition, a two-level energy harvesting strategy is developed to efficiently recover more automotive exhaust energy, and guarantee the safety of the proposed system under the modified Highway Fuel Economy Test (HWFET) driving cycle. The proposed strategy aims to achieve the lower power loss of DC/DC converters and keep the battery pack working at the optimal point. When the initial SOC of LiFePO4 battery pack is 10%, the charging energy has been increased by 174013J and the efficiency of DC/DC converters has been raised of 2.4% than PI control.

Abstract

With the intermittent and unstable renewable power feeding into the district energy systems (DES), the reliability of the system need to be accurately evaluated is of great significance. In order to predict the probability of system operational state in the design stage, in addition to provide the reasonable distributions of the input parameters, the transmission of the uncertainty in the analytical model need to clarify. In this paper, taking photovoltaic systems for example, the method to quantify the meteorological parameters distributions in the uncertainty analysis was proposed. And then the transmission of the uncertainty in the theoretical model and data-driven model were compared. The Back Propagation Neural network model (BP model) was selected as example. The BP model shows high accuracy than theoretical model, meanwhile, it also shows lower uncertainty. The results indicated that the data-driven model is more suitable for estimating the system output in the design stage. The research will provide guidance for system modeling by using data-driven model.

Abstract

As one of the cleanest energy source, liquefied natural gas(LNG) plays an essential part in the world energy market. This study proposes to utilize the LNG cold exergy and low-temperature waste heat with a three-stage traveling-wave thermoacoustic engine(TWTAE) coupled with linear alternators(LA). Numerical simulation is conducted to optimize the performance of this system. The effect of multiple factors of both the looped thermoacoustic engine(TAE) and the LA has been investigated. The three-stage traveling-wave thermoacoustic electric generator (TWTAG) operating with 4 MPa Helium under a temperature difference of 110-500 K is able to extract 15 kW acoustic power while the output electric power is nearly 13 kW. The overall exergy-to-acoustic efficiency is 44.2% while the heat-to-electric efficiency is nearly 40%.

Abstract

As the increasing complains of the electric passenger car owners about the lower pure electric mileage under real-road driving condition than the regulation standard test result, the annual real-road energy consumption characteristics of 20 MPV electric passenger cars in Chinese city, Shenzhen, have been investigated to analyze the effect factors causing the energy consumption difference between these two results. Results showed that the annual variations of realroad energy consumption rate of each month were agreed with the variations of air conditioning using duration. The highest and lowest energy consumption rates were obtained in July and March, which increased the energy consumption rate of whole vehicle about 24% in the maximum extent. The difference of the energy consumption between real-road and regulation standard test was attributed to the effects of air conditioning using and driving condition (driving velocity and acceleration distribution), which have been qualified in this paper.

Abstract

The present study examines the feasibility of Solid Oxide Fuel Cell (SOFC) assisted Vapor Absorption Refrigeration System (VARS) for refrigerated transport to replace the conventional TRU, where the heat generated from SOFC can be used to run the VARS. The study investigates and compares the GHG emissions from SOFC assisted VARS, diesel, and natural gas (NG) engine powered TRU, and cryogenic transport refrigeration systems. The operational and production related emissions were considered here to find out the total GHG emissions from the above-mentioned systems. Hydrogen fueled SOFC was considered in this work, and four different hydrogen (H2) production methods (solar based electrolysis, windbased electrolysis, biomass gasification, and NG reforming) were studied to calculate the hydrogen production related emissions. The analysis was then applied to systems for chilled and frozen products over a 10-hour vehicle operation. Finally, to select an optimum system configuration, both environmental and economic aspects were be considered. The mass intensity of the various fuels to obtain the required amount of refrigeration load in the different systems was calculated. The result showed that the considered novel SOFC-VARS emitted considerably lower amounts of GHG (50- 75 % reduction) compared to diesel and natural gas (NG) fueled TRUs, and cryogenic transport refrigeration systems.