[en] Highlights: • The measured shafting vibration data signal of the hydroelectric generating set is acquired through EMD. • The vibration signal waveform is identified and purified with EMD to obtain approximation coefficient of various fault signals. • The multi-fractal spectrum provides the distributed geometrical or probabilistic information of point. • EMD provides the real information for the next subsequent analysis and recognition. - Abstract: The vibration signal analysis of the hydraulic turbine unit aims at extracting the characteristic information of the unit vibration. The effective signal processing and information extraction are the key to state monitoring and fault diagnosis of the hydraulic turbine unit. In this paper, the vibration fault diagnosis model is established, which combines EMD, multi-fractal spectrum and modified BP neural network; the vibration signal waveform is identified and purified with EMD to obtain approximation coefficient of various fault signals; the characteristic vector of the vibration fault is acquired with the multi-fractal spectrum algorithm, which is classified and identified as input vector of BP neural network. The signal characteristics are extracted through the waveform, the diagnosis and identification are carried out in combination of the multi-fractal spectrum to provide a new method for fault diagnosis of the hydraulic turbine unit. After the application test, the results show that the method can improve the intelligence and humanization of diagnosis, enhance the man–machine interaction, and produce satisfactory identification result.

[en] Highlights: • Constructed a variety of wetlands with different plants and substrates • Explored the purification of wetlands on rainwater • The purification efficiency of wetland with Reed and Zeolite • Wetland with Reed and Zeolite can effectively purify initial rainwater. In order to promote the construction of the Sponge City and strengthen the utilization of rainwater resources, this paper attempts to design a wetland that can effectively purify the rainwater. The rainwater quality of Zhengzhou was monitored to provide actual data for follow-up studies. A variety of wetlands with different plants and substrates were constructed to analyze the purification of wetlands on rainwater. The wetland with optimal parameters was selected to ensure the effluent can be reused. The average concentrations of Chemical Oxygen Demand (COD), Total Nitrogen (TN), Nitrate Nitrogen (NO₃⁻-N) and Ammonium Nitrogen(NH₃-N) in the initial rainwater were 140.25 mg/L, 13.31 mg/L, 5.77 mg/L and 6.82 mg/L, respectively. The experimental results show that the efficiency of COD purification in each wetland is great, and the differences between wetland are small. Compared with other substrates (gravel, activated carbon, vermiculite), zeolite effectively enhanced the purification effect of wetland on ammonia nitrogen. The purification efficiency of wetland with reed and zeolite is the best, and the removal efficiency of COD, TN, NO₃⁻-N and NH₃-N is 86.54%, 89.46%, 95.87% and 80.88%, the nitrogen removal efficiency of this wetland is greatly improved. Based on various reuse standards in china, wetland with reed and zeolite can effectively purify initial rainwater, and the effluent can be used to urban miscellaneous water, landscape water and industrial water. This study has important reference significance and practical value for the construction of rainwater wetland in the process promoting the Sponge City.

[en] Highlights: • Water is scarce in the nine coal-fired energy bases of the north and west China. • The water footprint of coal and power production in the nine bases is evaluated. • The virtual water flow along with the energy products transfer is also analyzed. • Water stress in the energy bases is keeping increasing in the past and future. • The comprehensive countermeasures are proposed to ensure water and energy security. -- Abstract: In the past decades, the nine major energy bases in north and west China produced increasing amounts of coal and coal-fired power to meet rapidly growing energy demand. However, the poor water resources condition has become a bottleneck for sustainable development. In this study, the water footprint of coal and power production is evaluated, and the flow of virtual water arising from the transport of energy products is quantified. The results show that total coal and power production increased continuously from 2006 to 2015. The annual total water footprint was as much as 1.29 billion m³; it showed an initially increasing trend that peaked in 2013, after which it decreased. After 2013, the water footprint decreased primarily as a result of improvements in water-saving technologies. The results also indicate that increasing amounts of virtual water (as much as 0.87 billion m³ in 2015) embedded in energy products flowed from the north and west water deficient areas to the southeast water-rich areas of China, causing severe water scarcity in the major energy producing regions. Unfortunately, based on our estimates, water stress will continuously increase during the 13th Five-Year Plan period (2016–2020). This study finds that water-saving measures alone are not sufficient to relieve the water shortage and to guarantee water security. Comprehensive countermeasures, including an adjustment to the industrial structure, the physical transfer of water, regulation of the virtual water trade and policy and planning changes, are also necessary.

[en] Highlights: • Intense vibration in hydraulic turbine generator unit draft tubes leads to a run-out of the shafting of the unit. • It assessed the condition of the unit by extracting information concerning its vibration signal features. • An enhanced Hilbert Huang Transform (HHT) method with an energy-correlation fluctuation criterion was used. Intense vibrations in hydraulic turbine generator unit draft tubes lead to a run-out of the unit shafting and threaten its safe and stable operation. Correct maintenance is therefore important for the safe operation of such units. This study involves assessing the condition of the turbine generator unit by extracting the feature information of its vibration signals. Based on previous research, we present an enhanced Hilbert–Huang transform (HHT) method with an energy-correlation fluctuation criterion to extract feature information and effectively verify the method with simulated signals. An inspection application based on the signal from a vortex strip in the draft tube of a prototype turbine under suboptimal operating conditions indicates that this method is more effective than the traditional one, with a better component identification capability and better suited to the analysis of the complex and dynamic feature information of hydro turbines.

[en] Highlights: • The total coal consumption cap reduces coal output. • The cap facilitates adjusting the structure of energy consumption. • The cap has significant positive effects on the protection of water resources. • Total coal consumption exceeds the coal mining scale constrained by total water use. • A holistic approach to the challenges China faces related to water is critical. - Abstract: China’s coal-based energy supply inflicts destructive damage upon the ecological environment, though it has simultaneously safeguarded the rapid development of China’s economy in recent decades. To promote ecological recovery and accelerate the adjustment of its industrial structure, China is poised to fully implement a total coal consumption cap through the “13th Five-year Plan” (2016–2020). This study assesses the feasibility of this strategy from the perspective of water resources, exploring and predicting outcomes from 2012 to 2050. After first measuring the water resources demands for the life-cycle of coal, this study then analyzes the destructive effects on water resources from coal production through to consumption, before finally evaluating the water conservation synergy effects under different plans for capped coal consumption. The results reveal that implementing a total coal consumption cap could reduce the adverse effects on the water resources system due to coal mining, washing, conversion, and utilization by comprehensively promoting conservation and protection of water resources. The study directly compares the two cap strategies of “behave as usual” and “reinforced total consumption control,” finding that neither of these strategies can totally satisfy China’s existing requirements for water resources management. In future, China’s total coal consumption will exceed the feasible scale of coal mining as restrained by total water use limits, and the required quantity of water for conversion and utilization of coal will also exceed its water use limit. Therefore, to achieve coordinated progress between the development of the coal-related industry and sustainable utilization of water resources, the Chinese government urgently needs to further reinforce total coal consumption controls and actively popularize the application of water-saving technology. In addition, the study estimates the damage to water resources due to China’s coal consumption, determining the value of lost water resources per ton of coal consumption nationwide to be 52.76 yuan. If all of China’s coal enterprises could apply water-preserving mining technology and make full use of mine water for production, the loss of water resources nationwide per ton of coal consumption could be lowered to 40.91 yuan. Therefore, the study advocates the combination of a market price adjustment mechanism and a macro total control strategy to maximize the synergic benefits between energy and water resources in China.

[en] Highlights: • China focusing increasingly on joint operation of cascaded hydropower stations. • Investigating the increased power generation potential of joint cascade operation. • Dynamic programming algorithm and super-computing avoid dimensionality problem. • Optimizing reservoir operation yields greater gains than joint operation. • Growing water and energy demands require careful construction of station clusters. The completion of Shuibuya, the last hydropower station to be constructed in the Qingjiang cascade, signifies China's successful development of the world's largest mixed cascade hydropower generation system. Joint operation of such cascaded hydropower stations is considered necessary to improve hydropower output in China. In this study, two modeling methods – routine and optimal operations – were adopted, based on existing rules of reservoir operation, to determine the effects of joint operation. To investigate the realistic and potential effects, the two models were computed using observed runoff data (1951–2009). The potential effects were identified by comparing the total hydropower generation two single cascades and their cogeneration. Under the routine operational mode, the incremental power generation of joint operation would be 5.73 × 10⁸ kWh, an increase of 5‰ compared to isolated operation. However, even in isolation, if reservoir operation is optimized through the dynamic programming algorithm, the incremental power generation of the cascade would be 42.24 × 10⁸ kWh, which is seven times that of joint operation with routine reservoir operation (5.73 × 10⁸ kWh). The results showed that, under current reservoir operating rules, there is little room for improvement in hydropower generation, although joint operation could increase hydropower generation to a certain extent, especially in the reservoirs' refill and release stages. China must amend its existing operational mode for reservoirs to enhance the economic benefits of cascade hydropower stations. Furthermore, to meet increasing demands for both water and energy, carefully considered planning of constructing clusters of these stations is required.