Abstract

With the rapid development of data centers, data center servers generate a lot of heat when working, and timely heat discharge is beneficial to the normal operation of servers. To reduce the energy consumption of the data center cooling system, a water-air hybrid cooling heat sink is designed and its structure is optimized to meet the memory and chip cooling demand but meanwhile without discharging heat to the atmosphere. When taking the chip temperature, memory temperature, outlet air temperature, and pressure drop as target variables, the heat sink structure optimization is done by analyzing their effect on server cooling performance. Also, the optimal required air inlet speed is explored based on obtained optimized structures. The results show that the optimal duct number is 2, the optimal duct width is 35 mm, the optimal distance between ducts is 14 mm, the optimal heat sink width is 41 mm, and the fin height is 1.5 mm. The optimal required inlet air speed is 4 m s-1 when the air inlet temperature is 25 °C.

Abstract

Methane seepages from natural process or gas hydrate dissociation are proposed to cause adverse effect of climate change. The ultimate fate of methane leakage from the deep sea is less understood. Here, a systematic investigation of dissolved methane intensity, characteristic of pore fluid migration, metallogenic features of the sediment, and evolutions of biological communities in different methane seeping areas was conducted by high-resolution image, pore fluid geochemical analysis, and lithologic and surface analysis of the sediment. Results indicate that with high methane flux, biogeochemical progresses dominated by AOM in sediments, excess methane emissions to seawater and the methane metabolic communities dominate. While at low methane fluxes, AOM co-exists with OSR. This work reveals the dynamic marine methane cycle mechanism in different seepage intensities.

Abstract

Methane (CH4) is a powerful greenhouse gas with a stronger greenhouse effect than carbon dioxide. The ocean is the largest CH4 reservoir in the world and plays an important role in adjusting climate change. Water column CH4 distribution and sea-to-air in the marine CH4 seeping areas are crucial to finger the ultimate fate of marine CH4. In this research, we investigated the distribution of dissolved CH4 and environmental factors in the water column, and calculated the sea-to-air flux in the “Haima” cold seep area. The results showed that the surface dissolved CH4 concentration ranged from 0.50 to 53.20 nM, and the sea-to-air flux was 38.56 μmol/m2/d. Compared with previous studies, it was higher than that on the general ocean surface but lower than that in the estuary area. In addition, the vertical distribution showed that the CH4 concentration in the surface layer was lower than that in the bottom layer, and the maximum value appeared at about 150 m. By PCA analysis, it can be found that SO42- and TOC were important factors affecting the dissolved CH4 concentration. In conclusion, understanding the CH4 emissions in cold seep areas is of great significance for coping with global warming.

Abstract

A thorough analysis of the solar energy potential and the utilization cost is necessary to form a public consensus on the active adoption of solar energy in Seoul. This study strives to answer two questions: How much solar energy can all the building rooftops in Seoul produce, and how does the feasibility of rooftop solar energy change, depending on the future development in economic and technological factors until 2050. The research simulates rooftop solar energy production in Mapo District of Seoul and combines it with future scenarios analysis, considering the technological advance in solar PV production systems and the change in economic factors such as wholesale electricity tariff and systems management cost. The study adopts the Ladybug tool, an energy modeling tool connected to a 3D CAD interface of the Rhinoceros program, to simulate hourly rooftop solar energy production in each season based on a digital map and weather data of Seoul. The simulation shows that 72% of the Mapo District’s total building electricity consumption in 2020 could have been covered by rooftop solar energy if solar PV panels covered every building rooftop. The three scenarios of benefit-cost analysis project that rooftop solar energy will start to play a crucial role in carbon mitigation between 2026 and 2044. However, the scenarios indicate that the explosive growth of PV panel installation would mean both the exponential increase of benefits and the escalation of costs, resulting in a slower expansion of the technology and higher costs for users. The research result also implies that increasing the supply of rooftop solar energy is not the sole essence of bringing solar city development to realization. As the transition to green energy involves uncertainty, a precise prediction of the potential amount of the source and consideration of the technological and economic usability will help achieve a feasible energy supply plan aiming for a slight burden on consumers in urban areas.

Abstract

Over-discharging is easier to occur at low temperatures. In this paper, the degradation characteristics were investigated by discharging to 2.75-0 V at 0°C and discharging at constant voltage for 0 and 2 hours, respectively. The results show that capacity fades linearly except for the 0 V-2 h cell that fades at an accelerated rate. The fade rates increase with decreasing discharging voltage. Besides, both the longer time of constant voltage and the lower discharging voltage contribute to loss of lithium inventory, loss of active materials, and internal resistance increase.

Abstract

Since 2021, energy prices in the international market have risen sharply, and the contradiction between supply and demand of electricity and coal in China has continued to be tight, resulting in power cuts and power rationing, which has slowed down China’s efforts to reduce carbon emissions. In order to improve the self-power supply capacity, stability and low carbon economy of microgrid, a capacity allocation method of optical storage microgrid system based on power limit conditions considering carbon trading profit is proposed. Firstly, an energy storage system is ntroduced to construct the topology structure of the integrated optical storage microgrid system. By settingthe upper limit of the load demand power in the configuration model and considering the carbon trading profit, an economic capacity allocation model with the maximum net income of the system operation as the optimization objective is established. Combined with the operation control strategy of energy storage battery work priority and the optimal configuration algorithm based on grey Wolf optimization algorithm, the optical storage micro-grid capacity configuration scheme considering carbon trading profit under the condition of power restriction is solved.

Abstract

This paper investigates the combustion performance of a new biomass heating stove. Firstly, a typical structure of a house is used as the design object for load calculation; then the stove structure is designed for experimental system design, and the results of the simulation and experiment are compared with the corresponding working conditions to test the model, and the model is used to analyze the factors influencing the pellet accumulation resistance, and the influence law of the pellet parameters on the accumulation resistance is obtained. The combustion characteristics of biomass pellets are investigated and combined with static stacking characteristics and dynamic combustion characteristics, firstly, a combustion model is established and the size range of feasible biomass pellets is initially determined by measuring the combustion efficiency in terms of the percentage of volatilization analysis during the pellet combustion process; subsequently, the volatilization analysis cloud at the central interface of the stove is changed and the morphological parameters of the pellets in the model are changed to obtain the influence of the size change of the pellets in this range on the volatilization The effect of the change in particle size on the volatilization of the particles in this range is then obtained.

Abstract

This paper proposed and implemented a novel method to rapidly generate building energy modeling for existing buildings with measured energy data by integrating the prototype building energy model and automatic model calibration. The generated models were applied for retrofit analysis with uncertainty. First, a prototype model for shopping mall buildings was proposed to generate a baseline EnergyPlus model based on the building’s basic information, including vintage, climate zone, total floor area, and percentage of each function type. Next, an automatic calibration algorithm was implemented to calibrate the baseline model based on the monthly electricity and natural gas usage data. Monte Carlo sampling was applied to generate 1000 combinations for fourteen parameters. Multiple solutions that meet the calibration criteria can be found. Moreover, the calibrated energy models were used to evaluate the energy-saving potential of several energy conservation measures. 29 EnergyPlus models that meet the calibration criteria are found. The lighting power density in those 29 models ranges from 11.4 to 14.9 W/m2 with an average of 13.1 W/m2; while the chiller COP ranges from 3.45 to 4.79 with an average of 4.00. The electricity energy saving percentage of replacing lights with LED lights ranges from 1.9% to 11.7% with an average of 6.1%; while the electricity energy saving percentage of chiller replacement ranges from 1.6% to 14.1% with an average of 8.4%. The results show a high level of uncertainty when the actual lighting power density and chiller cop information is unknown.

Abstract

The pipeline is a low-carbon and economical transportation mode in the downstream supply chain of petroleum products. At present, due to the lack of research on multi-product pipeline pricing strategies, the unreasonable pricing strategy has resulted in low utilization of pipeline capacity. This phenomenon causes the problem of high energy consumption of petroleum products transportation. Therefore, this paper aims to improve pipeline turnover and promote the low-carbon transportation market from the perspective of pipeline pricing optimization. We propose an integrated framework for multi-product pipelines, coupling the pricing strategy and logistics optimization model. This framework is used to simulate the pricing behavior of the pipeline carrier and the corresponding logistics planning behavior of the oil shipper. We simulate and display 10 pipeline pricing schemes for two regions in China with distinctly different logistics structures, and analyze the benefits of the new strategy in both economic and environmental terms. The results show that the well-performing schemes can increase pipeline carriers’ revenue by 11.41 million CNY per month, significantly improve the competitive advantage of long-distance pipelines, and reduce carbon emissions by 272 tons. In turn, recommendations for policymakers are provided at four levels. In conclusion, the new pricing strategy will help reverse the disadvantageous situation of the pipeline in the competitive market and promote the petroleum product logistics industry to reduce carbon emissions.

Abstract

With the rapid development of natural gas industry, the optimal design is a key factor in improving the economic, environmental and social performance and efficiency of the natural gas supply chain. Therefore, it is necessary to conduct a comprehensive review of natural gas supply chain optimization problems to formulate future development plans. In this paper, we review the relevant literature on natural gas supply chain optimization, summarize the research progress of natural gas supply chain design optimization methods from the aspects of overall supply chain optimization, market operation and pricing mechanism optimization, pipe network transportation system optimization, and discuss the impact of natural gas market policy changes on supply chain optimization. Finally, the shortcomings of current research and the direction of future development are discussed.