Abstract

Some industrial parks in China have completed the construction of green composite energy network and obtained the green building identification certification. However, after several years of operation, their renewable energy system has room to be updated. After combing the domestic and foreign studies, the current situation and prospects of the energy system in an industrial park in Tianjin, China are analyzed. Eight strategies were proposed from the three aspects of expanding photovoltaic area, upgrading photovoltaic equipment and improving management. The energy output, economic impact and environmental effects were calculated for each scenario. Results displayed that using the photovoltaic system upgrading strategy proposed in this paper, the renewable energy use of the integrated energy park can be effectively improved and enhance its demonstration significance in the whole society.

Abstract

R290, as an effective and environmentally friendly refrigerant, has great potentials in the application of air-conditioning. In this paper, the performance of inverter air conditioner (AC) using R290 is compared theoretically with that of other refrigerants. Moreover, the performance of a split AC was experimentally studied in both summer and winter condition with different ambient temperature. The results show that: In winter condition, the system EER varies from3.78 to 2.79 as the ambient temperature changes from 12℃ to -12℃；in summer condition, the system EER decreases from 2.26 to 1.91 as the indoor temperature increase from 29℃ to 43℃. The discharge temperature of inverter AC using R290 is far lower than that of R32. However, there is still great potential for improvement of supply air temperature control. This study provides reference for optimization of inverter AC using R290.

Abstract

Large airports generate enormous amount of CO2 due to frequent landings and takeoffs (LTOs) of airplanes and energy consumption. To advance carbon neutrality, the carbon emissions of airports need to be assessed. This paper evaluated the carbon emissions of airports and the contribution of airplanes in the LTO cycle in China Mainland in 2019 before the COVID-19 pandemic, and completed a simple distance matching analysis in the case of direct air carbon capture and sequestration (DACCS) application. It was found that the total CO2 emissions from airports in China Mainland in 2019 added up to about 153.52 million tons and the CO2 emissions from LTOs about 16.25 million tons. Approximately 90% of airports are within 5 km of the nearest sequestration sinks.

Abstract

Transportation is a big energy consumer especially for high-speed railway and air transport. This paper firstly compares passenger turnover and energy consumption between high-speed railway and air transport. Secondly, air transport mainly uses aviation kerosene, which has a relatively large impact on the environment, while high-speed railway is based on electricity. Moreover, this paper proposes a plan to provide electricity for high-speed railway derived from wind and solar energy. By comparison, it is concluded that high-speed railway is more environmentally friendly and more energy-efficient than air transport.

Abstract

To improve the accuracy of power system short-term load forecasting and energy utilization efficiency, based on Variational Mode Decomposition (VMD), Least Squares Support Vector Machine (LSSVM), and Slime Mould algorithm (SMA), a combined load forecasting model of VMD-SMA-LSSVM is proposed. First, the load signal was decomposed by VMD. For the decomposed sub-sequences, a combined algorithm based on slime mold optimization algorithm and least square support vector machine algorithm is used to predict respectively. Then, the predicted results of each sub-sequence were superposed and reconstructed to get the final predicted value. By comparing it with other machine learning models and other decomposition methods., this research results show that the load prediction results based on this method have more excellent prediction effects than methods.

Abstract

The wider or even full adoption of electric vehicles and renewable energy sources threatens conventional power systems and affects energy reliability. Residential air conditioning (AC) systems can serve as significant demand flexibility resources by shifting electricity consumption between different periods. However, coordinating multiple diverse and dispersed ACs with different dynamics and capacities in residential buildings is still a grand challenge. Existing studies mainly focused on fixed-speed air conditioners with on-off states only. Moreover, most control strategies are centralized and face user privacy and computational and communicational overhead concerns.
This study proposed a consensus-based distributed control strategy to allocate the demand response tasks fairly to multiple inverter air conditioners. First, a mathematical model with lumped thermal parameters is established to describe inverter air conditioners’ thermodynamic and electrical behaviors. Then, a combination of weighted consensus and average consensus-based modification algorithms is adopted to prioritize the DR-participation rate of inverter air conditioners with different capacities and dynamics. The control variable is the temperature setpoint of each inverter air conditioner. Finally, a building with five inverter air conditioners is simulated under a virtual demand response signal. Simulation results validated the effectiveness of the consensus-based distributed control scheme, which is scalable with the plug-and-play feature. As a result, the inverter air conditioners could effectively and efficiently respond to external DR signals.

Abstract

A comprehensive and detailed energy consumption inventory of crop production is of considerable significance to agricultural management because of the great changes in agricultural mechanization. In this study, a cost-input method was used to calculate the energy consumption of seven major crops in China from 2012 to 2018. Ten energy consumption phases of crop production were considered, including tilling, sowing, field management, harvesting, and treatment. The energy consumption of major crops in China increased by 25% over this time period, with indirect energy consumption accounting for a large proportion of the total, and direct energy consumption increasing rapidly. Of the grain crops, corn consumed the most energy in 2018, followed by rice and wheat. Among the oil crops, the total energy consumption of peanut was greater than that of rapeseed. There were differences in the energy consumption phases of crops per hectare and per unit yield. Considering the total energy consumption structure in 2018, the consumption of compound fertilizer was the highest, followed by nitrogen fertilizer use, mechanical tilling, mechanical harvesting, and mechanical sowing. The crops studied showed different life cycle energy consumption structures. Agricultural machinery operation was the prominent contributor to energy consumption for soybean and rice production, while chemical fertilizer was the primary contributor for cotton production; both contributed to the energy consumption for other crops.

Abstract

Tight oil energy occupies an increasingly important position for petroleum energy in the world. At present, most tight oil reservoirs have the problems of low formation pressure and difficult exploitation. Therefore, it is important to make reasonable management scenarios and forecasting for tight oil energy. Current research shows that natural gas flooding (NGF) can improve oil recovery for tight reservoirs, meanwhile, the oil field usually has abundant associated gas, which is suitable for natural gas flooding.
This paper mainly investigates NGF development for tight oil reservoirs in Ordos Basin, aiming to recycle the associated natural gas that has little commercial value to enhance oil recovery, and formulates reasonable development plan and forecasting. The PVT experiment is conducted to provide support for numerical simulation, which includes three parts: Firstly, the numerical model of tight reservoir is established. Then, sensitivity production parameters are analyzed. Finally, oil recovery and gas storage are studied.
The phase diagram of crude oil is obtained by PVT experiments, and the saturation-pressure line is obtained by composition model is well matched with the experimental data. Sensitivity analyses demonstrate that the recommended injection rate of single well is 4000-4500 m3/d and bottom hole pressure of production well is about 8 MPa. In the early stage of NGF, oil recovery is higher and gas storage effect is better, while oil recovery and gas storage effect are both poor in the later stage.
This paper is a combination of energy recycling and enhanced oil recovery. In this research, development scenarios and forecasting are applied in practical oil fields and provides support for subsequent development, which provides a reference for developing similar oil reservoirs. Meanwhile, it is expected that this research can be extended to the collaborative gas storage construction and oilfield development.

Abstract

This study investigates and compares the economic analysis of renewable energy-based systems incorporating photovoltaic (PV) panels, electrolyzer, fuel cell (FC), and a hydrogen tank for single houses in North America. Three systems consisting of PV/battery bank, PV/hydrogen, and PV/battery bank/hydrogen are simulated and optimized using the software HOMER. In this study, the electrolyzer produces green hydrogen using to the power obtained by the PV array; the generated hydrogen is stored in a hydrogen tank and powers the FC. Based on the results, the integration of 12 kW PV panels, 2.50 kW FC, 10 kW electrolyzer, 50 kg hydrogen tank, 2 kW converter, and 24 kWh of batteries is found to be the best configuration in Toronto, as it leads to the minimum net present cost (NPC) and levelized cost of energy (COE). Results show that while the battery bank can be used instead of the electrolyzer, FC, and hydrogen tank, the large batteries resulted in the highest NPC due to their high investment cost. Finally, the study is extended to Miami and Washington in the U.S., to check the validity of the conclusions with higher average annual solar radiation and to find their cost-effective configurations.

Abstract

The supercritical carbon dioxide (S-CO2) Brayton cycle is widely applied in energy conversion systems, the heat transfer characteristics of S-CO2 is an important factor affecting the cycle efficiency. The heat transfer characteristics of S-CO2 flowing upward in a vertical tube(d=4.57mm) is studied in this paper by experimental and numerical method. The numerical results are verified by experiments. And experiments are performed to analyze the parameter effects on heat transfer characteristics. The distributions of radial velocity and turbulent kinetic energy at different axial positions are obtained by numerical method to analyze the heat transfer mechanism. The results show that the effect of buoyancy flattens the velocity distribution, resulting in the weakening of turbulence intensity and the deterioration of heat transfer. Heat transfer deterioration occurs while q/G≥0.1kJ/kg. The heat transfer performance is better at higher mass flux or lower heat flux. Pressure and inlet temperature affect heat transfer only while the fluid state is near the pseudo-critical region. Based on the experimental data, a heat transfer correlation is proposed, the largest prediction deviation is less than 25%.