Abstract

Climate change involves research in a number of fields and disciplines such as environmental science, energy, social science et al. in general. As research in these areas advances rapidly, it is critical to keep abreast of emerging trends and critical turns of the development of the collective knowledge. This article provides a review of recent research on climate change with a particular focus on drives of energy sector. Visual analytics of the literature provides a valuable, timely, repeatable and flexible approach in addition to traditional systematic reviews so as to track the development of new emerging trends and identify critical evidence. It concludes with a summary of key lessons offered by the energy sector as well as suggestions for future research.

Abstract

In this research, thermal decomposition characteristics of cellulose with electron injected air were investigated in a laboratory scale reactor based on the principle of the groundbreaking organic substance reduction device ERCM (Earth-Resource-CeramicMachine), which was developed by a Japanese venture company. A 12 V voltage electron generator as the key part, was adopted to inject electrons into the air for accelerating the thermal decomposition of carbonaceous materials during the ERCM process. A modified fixed bed reactor was adopted to investigate the effects of different parameters including the on/off of electron injection into the air and the thermal decomposition temperatures (350-500O C) on the decomposition degree (volume reduction rate) and the syngas generation of pure cellulose. It was found that the thermal decomposition reaction was more accelerated with the electron-ON case than that with the electron-OFF case. In addition, it was shown that the volume reduction rate of cellulose in the electron-ON case was higher by 4.4% to 18.3% than that in the electron-OFF case. These results suggest that electron injected air may accelerate the thermal decomposition of solid wastes.

Abstract

The partial blockage in gas pipeline due to solid deposition is one of the major risks for the pipelines transportation system. Determining the location and severity of blockage is the key to mitigate or remove it with a high efficiency. In this year, the pressure pulse wave method has been considered as a promising method for blockage detection for their operational speed, maneuverability, and long detection range. However, the application results of this method showed the low accuracy of detecting blockages in pipelines. In this work, a series of tests was performed in a 106 m pipelines with a 22 mm pipe diameter, the experimental result indicated that the blockage location predications based on pressure pluse wave method have an acceptable accuracy. The cross-sectional shape of the blockage will greatly affect the intensity of the reflect wave. It is necessary to consider the cross-sectional shape when calculating the blockage percentage.

Abstract

Microalgae-based biomass are an emerging technology and an alternative source to biofuels. It has a high lipid content and is composed of other biocompounds which is essential for high-valued products. The biorefinery concept is a means to efficiently convert microalgae into biofuels and other high-value products. However, biorefineries require large capital investments that must be wisely planned and decided across the lives of the investments. This study proposes a multi-period multi-objective mixed integer non-linear programming (MINLP) model that simultaneously maximizes net present value (NPV) and minimizes greenhouse gas (GHG) emissions through optimal investment scheduling and operational decisions of an algal biorefinery. The model capabilities are demonstrated through an illustrative case study and scenario analysis.

Abstract

In this paper, we present three-dimensional (3-D) large eddy simulations (LES) of the thermally-induced oscillatory flow inside a full-scale quarter-wavelength standing-wave thermoacoustic engine (TAE). The TAE comprises a hot buffer, a stack and a resonator. Compressible nonlinear governing equations together with the equation of state are solved by the computational fluid dynamic (CFD) solver with the optimal node number and time step size. Numerical results show that self-excited acoustic oscillations occur inside the TAE, undergoing exponential growth, saturation and limit-cycle processes. It is also found that fundamental-mode standing-waves dominate the limitcycle acoustic oscillations while higher-order harmonics coexist. The velocity profiles in the radial direction are highly affected by the Stokes number, displaying Poiseuille flow patterns in the stack channels and Richardson’s annular effects in the resonator. The vortex shedding at the stack ends contributes to kinetic energy and heat losses as presented by the three-dimensional vorticity and time-averaged mass flux contours. The developed 3-D LES framework in this study provides high-fidelity simulations of thermoacoustic oscillations, deepening the understanding of multi-dimensional thermoacoustic effect and various nonlinear phenomena in the large-amplitude regime.

Abstract

Barriers exist against the emergence of any new technology. For algal biorefineries, these barriers manifest in competition for resources, slow capacity growth, and the diminishing urgency of environmental issues, which worsen as the algae-based biofuel is diffused. Given the dynamic nature of the problem, a system dynamics model is developed with the objective of identifying areas for intervention that can promote diffusion with minimal negative feedback. The model contains four dynamic hypotheses, representing areas that hamper the diffusion of algae-based biofuel. These hypotheses are the economic, social, and environmental sectors that are affected by the operations of algal biorefineries. A sensitivity analysis of parameters revealed the strategies which ensured the successful propagation of the technology relied on good anticipation of market growth and the maximized energy yield growth from investments. This was compared to traditional solutions such as incentives for adoption and penalties against emissions, and linear models. The results indicated that the linear models failed to capture the dynamicism of the problem. The contribution of this study is a new perspective on managing the growth of algal biorefineries.

Abstract

Under middle-low wind speeds condition, which is in the middle and lower sections of MPPT wind speed field, efficiency of wind power system is very low. This restricts the utility of this type of wind energy resource. Based on the relationship between DFIG wind power system efficiency and DFIG rotor rotation speed, a new MPPT with dynamic matching method was introduced to enhance the power conversion efficiency, which includes a certain turbine kinetic energy accumulation and release cycle. This method transfers turbine kinetic energy from lower rotation speed to higher rotation speed to convert mechanical energy into electrical energy by generator, which has higher efficiency. Base on theoretical analysis and simulation, the new dynamic MPPT method is proven to exhibit totally higher electrical efficiency than conventional MPPT.

Abstract

The fuel utilized in spark-ignition aviation piston engine is undergoing a transformation from gasoline to heavy fuels (kerosene and diesel) for security reasons. To overcome the problem that kerosene is difficult to be ignited by spark but easy to cause engine knocking, in this paper, short-chain alcohols were used to blend with kerosene to improve fuel physical and chemical properties. Specifically, three kind of alcohols namely ethanol, n-propanol and n-butanol were blended with kerosene by volume fraction of 30%, 50%, 70%, respectively. Results indicated that alcohol/kerosene blends could reach higher brake thermal efficiency (BTE) (alcohol ratio ≥ 50%) compared to gasoline. The low energy density of alcohols led to the increase in brake special fuel consumption (BSFC). Excessive ratio of ethanol and n-propanol (70%) led to higher maximum pressure rising rate (MPRR). For the main gaseous emissions aspects, CO and NOx emissions of blend fuels decreased. However, the unburned hydrocarbons (UHC) and soot emissions were relatively higher. Notably, nbutanol/kerosene exhibited better emission characteristics, which have the lowest CO, UHC and soot emissions, compared with other blends. With the increase of alcohol proportion in blends, the downward trends of CO, UHC as well as soot emissions were more pronounced, while NOx emissions increased first and then decreased for ethanol/kerosene and n-propanol/ kerosene. N-butanol in 70% volume fraction led to extremely high NOx emissions.

Abstract

Industrial parks have shown an important development trend of employing distributed generations instead of traditional centralized power supply. This paper studies the planning method of power supply systems in industrial parks, considering demand side response based on day‐ahead real time pricing. An improved demand side response model is proposed to solve the imbalance of energy shifting and overwork of demand side response when price elasticity matrix is used. Furthermore, an optimal planning model is established, taking minimum total cost as the optimization objective, and solved by the GA‐PS algorithm. Additionally, two indexes, the ratio of distributed generation deficiency energy and the ratio of distributed generation deficiency hours, are proposed to characterize the complementary of multi‐energy. Finally, a case of a typical power supply system in an industrial park is given to validate the proposed method.

Abstract

This paper proposes a self-adaptive principle of current differential protection for AC transmission line in AC-DC hybrid power grid. By analyzing the post-fault transient characteristics of inverter-side AC current with commutation failure occurred, the principle is proposed by using the promoted instantaneous energy ratio of currents from line terminals. The principle eliminates the influence of commutation failure by constructing instantaneous energy of terminal currents using trigonometric method. Besides, based on the feature that zero-sequence network of inverter AC system is isolated from DC system, the principle promotes the sensibility in high resistance-ground fault situations by constructing self-adaptive criterion with promoted instantaneous energy of zero-sequence AC current. PSCAD/EMTDC simulations are provided to verify the reliability of proposed principle and the results show that the novel principle is unaffected from commutation failure and is suitable for AC transmission line protection in AC-DC hybrid grid.