Abstract

Lithium-ion batteries of electric vehicles have shorter life and lower safety in high-temperature environment, and battery packs need to be cooled to ensure that they operate in a suitable temperature range. In this study, two different cooling schemes were compared. With the maximum temperature and maximum temperature difference of a battery pack as indices, the thermal characteristics of the battery pack at a high discharge rate were studied by conducting a CFD simulation under fin forced convection cooling and composite cooling (fin and phase change material). The results showed that the maximum temperature and maximum temperature difference of the battery pack at high discharge rates can be significantly reduced under fin forced convection cooling (at low air flow rates) and composite cooling. Under the composite cooling, the system is simpler, and the uniformity between the batteries is better.

Abstract

Clean coal technology is a key way to ensure the energy security and sustainable development of China. Supercritical water gasification of coal is a representative clean coal technology, which can be integrated within thermal power plants. In this study, adapted layouts of power generation system based on supercritical water gasification of coal were proposed to further enhance the system energy efficiency. Models of adapted systems were developed by Aspen Plus, and their performance was simulated. The results showed that the efficient system layout increased the energy efficiency by 8.72%- pts to 48.24% in contrast to its comparison layout. This improvement is mainly due to the 40% decrease of exergy destruction in superheater of the systems through adaption, as well as higher inlet parameters of turbine.

Abstract

In this study, we conducted a techno-economic analysis to estimate the deployment of zero-emission technologies (electricity and hydrogen) in Japanese transportation sector, considering the deep-decarbonization target by 2050. We used TIMES-Japan energy system analysis framework, which is following a whole-system approach. Results of calculations for energy demand of passenger and freight transportation by cars, buses, trucks, trains, airplanes, and ships are discussed after giving special attention to the capacities of low-emission technologies including renewables, nuclear, CCS, and hydrogen import in the supply side of energy system. Results of the calculations for the main scenario showed that zero-emission technologies would cover 75.6% of transportation energy demand in Japan by 2050, in order to achieve the 80% emission reduction target for the whole energy system.

Abstract

Microstructured surfaces have been found to be energy efficient and cost effective through enhancement of heat transfer, drag reduction and anti-fouling in areas such as thermal engineering, fluid mechanics, microelectronics and transportation. However, their use with the condensation phenomenon has yet to receive considerable attention. Therefore, based on a new approach to recover energy in humid environments, the influence of different geometries manufactured on stainless steel inserts via micro-wire electro discharge machining (µ-WEDM) on condensation was analysed. The experimental work was carried out in a chamber with a high percentage of relative humidity (% RH) comparing the geometries against an unstructured surface. The experimental results showed a differential temperature (ΔT), 26% higher than the unstructured surface. Thus, it is reasonable to believe that this experimental study could be used in the design of energy recovery systems to enhance condensation heat transfer.

Abstract

In this study we investigate the impact of Geopolitical Risk (GPR), US Economic Policy Uncertainty (EPU), St. Louis Fed Financial Stress Index (STLFSI), and market volatility (VIX) on the prices of US and Brazilian ethanol and Malaysian palm oil. By applying quantile autoregressive and quantile causality methods we can illustrate the dynamic relation between uncertainty and biofuel prices. Our results show that all measures of uncertainty influence ethanol and palm oil prices in both the lower and upper tails of the distribution. Furthermore, uncertainty seems to impact both U.S. and Brazilian ethanol prices price in a similar fashion, even if there are clear differences in the impact pattern. In the case of U.S. ethanol price, the results imply a slightly symmetrical impact pattern, with weak indications that uncertainty is triggering changes in price returns in the lower, towards the extreme, tails of the distribution. There are also clear indications that uncertainty impacts ethanol returns in the upper tails of the distribution, with a slight shift towards the middle quantiles. The results suggest that U.S. ethanol prices are more affected by uncertainty when the market conditions are positive rather than negative. In the case of Brazilian ethanol prices, the analysis also displays a symmetrical uncertainty impact pattern in both the lower and the upper tails of the distribution. However, unlike the other biofuel prices, there are indications that uncertainty also affects prices in the middle quantiles. Uncertainty has a stronger impact on Malaysian palm oil prices both near the middle quantiles as well as in the upper and extreme tails of the distribution. These results may indicate a sensitivity to uncertainty near normal market conditions and to large and extreme positive returns. Our results provide valuable insights into the price dynamics of biofuels. This knowledge is important for the transition to a sustainable energy system, especially in sectors not easily electrified such as aviation, shipping and certain types of industrial processes. Furthermore, our results also have implications for the financial sector and for risk management strategies.

Abstract

The conversion of renewable hydrogen and recycled CO2 to valuable fuels in power-to-liquids (PtL) systems could help mitigate the negative effects of CO2 emissions. Within this context, methanol is a promising candidate, both as an energy carrier and a chemical feedstock. This paper is focused on renewable methanol production and its use in a PtL integrated system based on alkaline water electrolysis, high temperature solid oxide fuel cells, a thermal energy storage system and an organic Rankine cycle (ORC) engine. Detailed models of the main subsystems were developed and implemented by using Aspen Plus software. A comprehensive analysis via mass and energy balances was carried out to evaluate performance indexes of each section and of the overall plant for two different configurations: with and without the ORC engine

Abstract

To satisfy the demands for fast-response peak regulation in power grids, the development of multistage compressed air energy storage (MCAES) system has accelerated in recent years. However, because of system imperfections, such as redundant structures, excessive numbers of energy conversion stages, and lower total utilization rate, it is necessary to identify and mitigate the weaknesses of the system. Consequently, this study conducts the thermodynamic analysis of MCAES. First, the efficiency losses in the working processes of the MCAES are considered, and a system node is added based on existing modular models, making the model more robust. Second, the effects of process parameters on system performance metrics, including power generation efficiency and residual heat, are studied. Finally, the weighted correlation network analysis (WGCNA) is used to analyze the sensitivity of various equipment and process parameters to system efficiency under different structures. Through the weight comparison, the weak points are located, which provides detailed theoretical guidance for the structural design and equipment parameter selection of MCAES.

Abstract

GT-Suite software is used to build a marine biomass diesel engine-organic Rankine cycle system. The accuracy of the simulation models of marine biomass diesel engine and organic Rankine cycle are verified. On the premise of verifying the accuracy, the influence of pump speed on the combined system is studied under the operating condition of engine speed 2100 r/min, 100% load. After design of experiment (DOE), the artificial neural network (ANN) prediction model is built under the premise of engine speed 2100 r/min, 100% load. And the speed of pump is predicted to maximize the output power of the combined system. The result show that the output power of the optimized combined system is 2.5 percentage points higher than the primary engine.

Abstract

In recent years, due to the influence of extreme weather, it is difficult to meet the demand for heating in non-concentrated areas in China. How to solve the problem of heating in non-centralized heating areas has become a research hotspot. This paper first introduces the advantages of electric heating technology and the impact of electric heating equipment access to the distribution network. Then, taking the electric boiler as the typical electric heating equipment, aiming at the expansion cost of the distribution network lines and the lowest investment cost of the electric boilers, the planning model considering the electric heating equipment accessing the distribution network is constructed, and the corresponding algorithm is used to solve the problem. Finally, a planning scheme for considering the connection of electric heating equipment to the distribution network is proposed, and the feasibility of the proposed scheme is proved by a study case.

Abstract

Thermoelectric generators (TEGs) have been considered as a promising technology for waste heat recovery owing to energy depletion and environmental pollution. Properties of a thermoelectric module (TEM) affect the TEG system performance essentially. This research investigated the optimal operation conditions of a TEM under steady state by experiments to achieve superior performance. The impacts of clamping force and interface material thickness on the characteristics of a TEM with given heat and cold source temperature are analyzed in detail. Results indicate that increased pressing force diminishes the contact thermal resistance and enhances the heat conduction. The maximum stress that a module can withstand should also be taken into account. In addition, graphite layers material replaces the air gaps between interfaces on account of its compressibility, which conduce to higher thermal conductivity. However, the thermal resistance of graphite material increases with excessive thickness as well. From the analysis above, it can be concluded that the optimal operation conditions of the TEM in this test are the clamping force from 2.5 kN to 3.7 kN and the graphitic layers thickness of 0.8 mm.