Impacts of low harm fracturing fluid on fossil hydrogen energy production in tight reservoirs

The polymer fracturing fluid has been gradually used in the fossil hydrogen energy field. However, its impacts on the fields are still unclear. In this study, a series of experiments were conducted to solve the problem. First, a new method called the pressure transmission test (PTT) was used to evaluate the permeability damage induced by polymer fracturing fluid. Then several rock properties were tested to reveal rock potential damage induced by the aqueous fracturing fluid, after that the interactions between polymer fracturing fluid and rock were discussed in detail. Results showed that the average permeability pollution is 10.6. Permeability and X-ray diffraction (XRD) tests stated that the core is easier to be blocked by particles in the formation or fracturing fluid residue. Blocking and scanning electron microscope (SEM) tests showed that the nanoscale polymer would stick on the rock surface, and reduce the pore size. Our work provides a new method to evaluate the impact of polymer fracturing fluid on tight reservoirs. Moreover, the mechanism of permeability damage caused by the polymer fracturing fluid was also revealed.     

Effect of organic loading on a novel hydrogen bioreactor

This study investigated the impact of six organic loading rates (OLR) ranging from 6.5 gCOD/L-d to 206 gCOD/L-d on the performance of a novel integrated biohydrogen reactor clarifier systems (IBRCSs) comprised a continuously stirred reactor (CSTR) for biological hydrogen production, followed by an uncovered gravity settler for decoupling of solids retention time (SRT) from hydraulic retention time (HRT). The system was able to maintain a high molar hydrogen yield of 2.8 mol H₂/mol glucose at OLR ranging from 6.5 to 103 gCOD/L-d, but dropped precipitously to approximately 1.2 and 1.1 mol H₂/mol glucose for the OLRs of 154 and 206 gCOD/L-d, respectively. The optimum OLR at HRT of 8 h for maximizing both hydrogen molar yield and volumetric hydrogen production was 103 gCOD/L-d. A positive statistical correlation was observed between the molar hydrogen production and the molar acetate-to-butyrate ratio. Biomass yield correlated negatively with hydrogen yield, although not linearly. Analyzing the food-to-microorganisms (F/M) data in this study and others revealed that, both molar hydrogen yields and biomass specific hydrogen rates peaked at 2.8 mol H₂/mol glucose and 2.3 L/gVSS-d at F/M ratios ranging from 4.4 to 6.4 gCOD/gVSS-d. Microbial community analysis for OLRs of 6.5 and 25.7 gCOD/L-d showed the predominance of hydrogen producers such as Clostridium acetobutyricum, Klebsiella pneumonia, Clostridium butyricum, Clostridium pasteurianum. While at extremely high OLRs of 154 and 206 gCOD/L-d, a microbial shift was clearly evident due to the coexistence of the non-hydrogen producers such as Lactococcus sp. and Pseudomonas sp.     

Thermodynamic analysis of a new double-pressure condensation power generation system recovering LNG cold energy for hydrogen production

Cold energy during the LNG regasification process is usually applied for power generation, but the electricity demand varies with the time. Therefore, a thought that transforming electrical energy into hydrogen energy by PEM electrolyzer is put forward to adjust the adaptability of power output to electricity demand. This paper proposes a new double-pressure condensation Rankine cycle integrated with PEM electrolyzer for hydrogen production. In this system, seawater is used as the heat source, and binary mixed working fluids are applied. Meanwhile, multi-stream heat exchanger is introduced to improve the irreversibility of heat transfer between LNG and working fluid. The key system parameters, including seawater temperature, the first-stage condensation temperature, the second-stage condensation temperature, and outlet temperature of LNG, are studied to clarify their effects on net power generation, hydrogen production rate and energy efficiency. Furthermore, the hydrogen production rate is as the objective function, these parameters are optimized by genetic algorithm. Results show that seawater temperature has positive impact on the net power output and hydrogen production rate. The first-stage condensation temperature, the second-stage condensation temperature, and outlet temperature of LNG have diverse effects on the system performance. Under the optimal working conditions, when the LNG regasification pressure are 600, 2500, 3000 and 7000 kPa, the increasing rate for optimized net power output, hydrogen production rate and energy efficiency are more than 11.68%, 11.67% and 8.88%, respectively. The cost of hydrogen production with the proposed system varies from 1.93 $/kg H2 to 2.88 $/kg H2 when LNG regasification pressure changes from 600 kPa to 7000 kPa.     

太阳能热化学制氢技术研究进展

总结了目前国内外太阳能制氢方法的研究现状,经过分析比较,确定太阳能热化学制氢具有极大的潜在发展空间.同时详细介绍了该方法的最新进展,对该方法研究中存在的问题提出了合理的改进建议.     

Optimization of self-regulated hydrogen production from photovoltaic energy

The use of photovoltaic energy (PV) for the production of hydrogen by using autonomous modular self-regulated systems is studied. Results are compared with those obtained for controlled systems. It was proved that for small and low-cost applications, it is possible to eliminate any control system with yields as high as 91.2% in the PV-electrolyzer interface for a sunny day. Self-regulated systems are thus an excellent, safe, cheap and environmentally friendly alternative for applications in isolated sites, especially in emerging countries.     

The future of hydrogen energy: Bio-hydrogen production technology

The widespread use of non-renewable energy has caused serious environmental problems such as global warming and the depletion of fossil fuels. Hydrogen, as a well-known carbon-free gaseous fuel, has become the most promising energy carrier for future energy. Hydrogen has an excellent mass-basis calorific value and no carbon atom contained, which makes it to be an attractive fuel for various power devices (like the internal combustion engine, gas turbine, and fuel cell). Nowadays, the production of hydrogen is still predominated by fossil-based techniques, which is considered undesirable due to low conversion efficiency and release of greenhouse gases. It is necessary to find green and sustainable hydrogen production routes with low energy consumption and cost. In this paper, the different hydrogen production technologies via fossil routes or non-fossil routes are reviewed in general, and it is found that bio-hydrogen production has certain environmental advantages and broad prospects compared with other hydrogen production technologies. Then, the characteristics and research status of different bio-hydrogen production technologies are discussed in depth. It is found that each bio-hydrogen production technique has its own advantages, challenges, and applicability. The economic analysis of bio-hydrogen energy is also performed from the aspects of production, storage, and transportation. The results show that bio-hydrogen production technology could be a good possibility way for producing renewable hydrogen, which is of high efficiency and thus competitive over other hydrogen production methods both in economics and environmental benefits.     

An innovative technology of directional propagation of hydraulic fracture guided by radial holes in fossil hydrogen energy development

Conventional hydraulic fracturing fails to develop low permeability reservoirs of fossil hydrogen energy that are not located in the direction of maximum principal in-situ stress. A new technology of fracture propagation guided by radial holes is proposed, which can realize directional propagation of hydraulic fracture along radial holes in fossil hydrogen energy development. In order to verify this new technology, a model of radial holes combined with hydraulic fracturing is established by the ABAQUS extended finite element method. Simulation results show that radial holes play a guiding role in fractures propagation. The influence extent of seven factors on the directional propagation of hydraulic fracture is listed as follows (from strong to weak): azimuth of radial holes > horizontal in-situ stress difference of fossil hydrogen reservoir > injection rate of fracturing fluid > Young's modulus of rock > permeability of fossil hydrogen reservoir > Poisson ratio of rock > viscosity of fracturing fluid. True tri-axial experiment is carried out to verify the accuracy of numerical simulation, and the result is consistent with numerical model, which indicates that numerical simulation is reliable.     

非化石能源制氢技术综述

在现今的经济社会和未来的低碳经济中H2将发挥重要作用.非化石能源制氢是化石能源短缺和温室气体排放等约束下的可持续制氢路径.综述了可再生电力电解制氢、核能制氢、太阳能制氢和生物质能制氢等四种非化石能源制氢技术的工作原理、流程设备和技术特点,最后对我国未来非化石能源制氢的路线选择进行了评论.     

Potential of renewable hydrogen production for energy supply in Hong Kong

Hong Kong is highly vulnerable to energy and economic security due to the heavy dependence on imported fossil fuels. The combustion of fossil fuels also causes serious environmental pollution. Therefore, it is important to explore the opportunities for clean renewable energy for long-term energy supply. Hong Kong has the potential to develop clean renewable hydrogen energy to improve the environmental performance. This paper reviews the recent development of hydrogen production technologies, followed by an overview of the renewable energy sources and a discussion about potential applications for renewable hydrogen production in Hong Kong. The results show that although renewable energy resources cannot entirely satisfy the energy demand in Hong Kong, solar energy, wind power, and biomass are available renewable sources for significant hydrogen production. A system consisting of wind turbines and photovoltaic (PV) panels coupled with electrolyzers is a promising design to produce hydrogen. Biomass, especially organic waste, offers an economical, environmental-friendly way for renewable hydrogen production. The achievable hydrogen energy output would be as much as 40% of the total energy consumption in transportation.     

氢能开发和利用的研究

简述了氢能特点，介绍了氢的制取方法及贮运，论述了氢能在我国的开发和利用及发展方向。     

Toward the clean production of hydrogen: Competition among renewable energy sources and nuclear power

This study elucidates the competition among renewable and nuclear energy sources for the production of hydrogen. These involve the use of solar, wind, biological process, tidal, geothermal and nuclear power to generate hydrogen. A comprehensive economic model, the Taiwan General Equilibrium Model-Clean Energy (TAIGEM-CE) model, is used for forecasting. Based on certain assumptions, the analytical results reveal that the most promising means of generating hydrogen is using wind power. Geothermal power is the most sensitive to external investment as a source of power for producing hydrogen. Solar hydrogen also benefits greatly from investment. Production of biohydrogen will be favorable without external investment, and they are less sensitive to investment than other renewable energy sources. Based on the assumptions made in this study, nuclear energy is not as competitive as most renewable energy sources for hydrogen production.     

太阳能制氢技术及其进展

阐述了光解水制氢的原理,介绍了光解水制氢技术的现状,分析了目前光解水制氢技术存在的问题以及提高光解水效率的有效途径,指出了利用光热化学循环进行光解水制氢的新途径.     

Electrical energy production from the integrated aerobic-anaerobic treatment of organic waste by ORC

The energetic performance of an ORC system fueled by the heat generated from the integrated aerobic/anaerobic treatment of organic waste was analyzed. The temperature and heat content of the exhaust air arising from the aerobic treatment were increased by the combustion of the biogas produced by the anaerobic digestion of a fraction of the same waste. On the basis of the amount of excess air exploited in the process, for each tonne of organic waste treated, it was possible to produce from 30 to 90 kg of exhaust air per day with a mean temperature ranging from 330 to 340 K. By processing from 0.5% to 16% of the whole organic waste in an anaerobic digestion section instead of the aerobic one, it was possible to increase the exhaust air temperature from 340 to 510 K, leading to an increase in the ORC size from about 0.05 to about 1 W/tonne/year. The best energetic utilization of the biogas was achieved for ORC compression ratios from 1.5 to 2 and for maximum air temperatures from 335 to 340 K. In these conditions, by using a micro-ORC system (i.e. <15 kW), it was possible to convert about 20% of the energy content of the biogas into electrical energy.     

氢能制取和储存技术研究发展综述

综述了氢能制取和储存技术研究的最新发展现状。生物质制氢、太阳能热化学循环制氢、太阳能半导体光催化制氢、核能制氢等技术具有资源丰富、使用可再生能源的优点,能克服传统电解水制氢能耗高和矿物原料有限的缺点,成为提高制氢效率、实现规模生产的研究重点。加压压缩储氢技术的研究进展主要体现在改进容器材料和研发吸氯物质方面;液化储氢技术研发重点是降低能耗和成本;金属氢化物储氢技术正努力突破储氢密度低的难题。氢能制取、储存技术正在走向实用阶段,重点技术方向是以水为原料,实现大规模、经济、高效和安全地制氢储氢,推动氢能可持续和洁净的利用,促进能源安全。     

Effect of bioaugmentation on hydrogen production from organic fraction of municipal solid waste

In the present study, the effect of bioaugmentation with three bacterial species (i.e. E. coli, Bacillus subtilis and Enterobacter aerogenes) on the hydrogen production from organic fraction of municipal solid waste was evaluated at different bacteria/sludge ratios (0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35 and 0.40). Cumulative hydrogen production, lag phases, and maximum hydrogen production rates were analyzed using modified Gompertz model. The highest cumulative and volumetric hydrogen production of 564.4 ± 10.9 mL and 1.61L_H2/L_substrate respectively was achieved for bioaugmentation with Bacillus subtilis at bacteria/sludge ratio of 0.25. The corresponding highest hydrogen yield was 43.68 mLH₂/gCarbo. For bioaugmentation with E. coli and Enterobacter aerogenes, the maximum cumulative hydrogen production of 423.4 ± 10.6 mL and 486.3 ± 10.6 mL respectively was obtained from bacteria/sludge ratio of 0.20. Corresponding highest hydrogen yields were 32.9 mLH₂/gCarbo and 37.1 mLH₂/gCarbo respectively. Bioaugmentation shortened the lag phases and improved COD removal. Volatile fatty acid generation was also improved with the bioaugmentation.     

隔膜特性对氢气电化学压缩能耗的影响

文章选取Nafion 211和Nafion 117膜作为电化学压缩隔膜,通过仿真建模方法研究了隔膜特性对电化学压缩机压缩性能的影响。研究结果表明:隔膜欧姆阻抗对电压效率影响显著,隔膜气密性对电流效率影响显著;与Nafion 117膜相比,将Nafion 211膜应用于电化学压缩机时,电化学压缩机能够获得更高的能量效率,当工作电流为0.5 A/cm^2,压缩比为3时,等温压缩效率最高可达到50%。将以Nafion 211膜为隔膜,工作电流为2 A/cm^2的电化学压缩机用于制氢厂的管束车充装,当气源压力为2 MPa,管束车压力由5 MPa充装至20 MPa时,平均能量效率为35%,综合平均电耗为2 kW·h/kg,比目前常用的机械往复式压缩机的电耗降低了30%以上。     

Effect of pre-treatment and hydraulic retention time on biohydrogen production from organic wastes

This study investigated the effect of pre-treatment and hydraulic retention time (HRT) on biohydrogen production from organic wastes. Various pre-treatments including thermal, base, acid, ultrasonication, and hydrogen peroxide were applied alone or in combination to enhance biohydrogen production from potato and bean wastewater in batch tests. All the pre-treated samples showed higher hydrogen production than the control tests. Hydrogen peroxide pre-treatment achieved the best results of 939.7 and 470 mL for potato and bean wastewater, respectively. Continuous biohydrogen production from sucrose, potato and bean wastewater was significantly influenced by reducing the HRT as 24, 18 and 12 h. Sucrose and potato showed similar behavior, where the hydrogen production rate (HPR) increased with decreasing the HRT. Optimum hydrogen yield results of 320 mL-H₂/g-VS (sucrose) and 150 mL-H₂/g-VS (potato) were achieved at HRT of 18 h. Bean wastewater showed optimum HPR of 0.65 L/L.d with hydrogen yield of 80 mL-H₂/g-VS at 24 h HRT.     

Safety analysis of leakage in a nuclear hydrogen production system

Due to its unique advantages, such as clean and pollution-free, hydrogen energy has gradually improved its energy transition position. Constructing nuclear hydrogen production systems is a necessary means to achieve large-scale hydrogen production, and the study of hydrogen leakage and diffusion behavior is critical to commercializing hydrogen production systems. In engineering practice, the distance between the hydrogen storage device and the nuclear power plant is an important indicator to measure the safety of nuclear hydrogen production. To study the influence of gas storage tank's own conditions and external environmental conditions on leakage diffusion, influencing factors such as wind speed, leakage direction, leakage diameter, leakage height, and leakage angle are discussed in the present study. By calculating severe working conditions combined with the above multiple factors, the longest distance of hydrogen diffusion is determined. Finally, peak overpressure impact generated by hydrogen explosion was evaluated, and the minimum separation distance required to avoid safety risks was predicted. The results demonstrate that when the wind direction is consistent with the leakage direction, and the leakage angle is 0°, the higher the wind speed, the larger the leakage diameter and the lower the leakage height, resulting in a longer diffusion distance. Under more extreme and severe working conditions, the diffusion distance of combustible hydrogen cloud can reach as far as 237 m. Once hydrogen diffusion explodes, the minimum separation distance required is about 338 m. This research provides an effective method for safety risk assessment of a nuclear hydrogen production system.