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Abstract The hydrodynamic performance of a fixed Oscillating Water Column (OWC) wave energy device under various wave conditions and geometric parameters was tested experimentally in a wave flume. The measured water surface elevation at the chamber center, the air pressure in the chamber of the OWC device and the hydrodynamic efficiency are compared well with the published numerical model results in Ning et al. (2015). Then the effects of various parameters including incident wave amplitude, the chamber width, the front wall draught, the orifice scale and the bottom slope on the hydrodynamic efficiency of the OWC device were investigated. It is found that the opening ratio e (e = S0/S, where S0 and S are the cross-sectional areas of the orifice and the air chamber, respectively) has a significant influence on the maximum hydrodynamic efficiency of the OWC device. The optimal efficiency occurs at the opening ratio of e = 0.66%. Although bottom slope has little influence on the resonant frequency, the optimal hydrodynamic efficiency increases with the increase of bottom slope. A proper bottom slope can provide a work space in the OWC chamber almost independent on the sea wave conditions. The spatial variation of the water surface inside and outside the chamber was also examined. And the results indicate that the water motion is highly dependent on the relative wave length λ/B (where λ is the wave length and B is the chamber width). Seiching phenomenon is triggered when λ/B = 2 at which the hydrodynamic efficiency is close to zero.

Abstract A pilot-scale anaerobic co-digestion research study is presented to elucidate the feasibility of developing anaerobic digestion (AD) as an effective disposal method for municipal biomass waste (MBW) in China, focusing on biogas production and greenhouse gas (GHG) reduction. Food waste, fruit–vegetable waste, and dewatered sewage sludge were co-digested in a continuous stirred-tank reactor for biogas production. Stable operation was achieved with a high biogas production rate of 4.25 m3 (m3 d)−1 at organic loading rate of 6.0 kgVS (m3 d)−1 and hydraulic retention time of 20 d. A total of 16.5% of lipids content was beneficial to the biogas production of the feedstock without inhibition to anaerobic digestion. Compared with the landfill baseline, GHG reduction is an important environmental benefit from MBW digestion. Therefore, anaerobic co-digestion is a promising alternative solution for MBW because it contributes significantly to the sound management of municipal solid waste in China.

Solar−coal hybrid power generation (SCHPG) system is one of the interesting solutions for solar power generation. This research aims to find a more viable integration mechanism of solar energy into a coal‐fired thermal power plant in terms of techno‐economic and ecology perspective. Performance of the 300 MW SCHPG system in the nominal and part‐load condition is analyzed under three different integration mechanisms. Numerical simulation of 300 MW SCHPG system is investigated under four different cases using a thermal balance approach. Operation modes of fuel‐saving (FS) and power‐boosting (PB) are considered for each case. Among the proposed cases, Case 4 is obtained as a good operation performance, which is recommended as the main case. The solar energy in Case 4 is used for evaporating feedwater and steam superheating, and steam reheating. Results show that the optimal aperture area of the heliostat solar field is 330 330 m2, and the minimum levelized cost of electricity is 0.1847 USD kWh−1. In Case 4, thermal efficiency is increased by 7.19% with standard coal consumption reduced by 45.3 g kWh−1 compared to a reference power plant. In the SCHPG system, coal consumption is reduced by 26.8 tons h−1 in FS mode, whereas power output is increased 30 MW h−1 in PB mode.

Ion exchange resins are employed extensively in the nuclear industry to remove the radioactive contaminants such as neutron activation products and fission products which may have leaked from fuel elements. The spent radioactive ion exchange resins have been produced during the operation of the nuclear facilities in the nuclear industry. The resins loaded with radioactive nuclides could not be regenerated and reused. These waste resins should be properly treated and disposed in order to minimize their potential hazard to the environments. In this paper, different technologies used for the treatment and disposal of spent radioactive resins were summarized and compared, including immobilization (such as cementation, bituminization and plastic solidification), advanced oxidation processes (such as incineration, pyrolysis, acid boiling degradation, the Fenton or Fenton-like reaction, supercritical water oxidation and plasma technology) and super compaction. Some supplementary methods, such as acid stripping, microbial conversion treatment and high integrity container were also mentioned. The principle of treatment methods, their characteristics and applications were briefly introduced, the future research directions were discussed.

Abstract The flow induced motion (FIM) and energy conversion of cylinders with different cross sections are investigated using two-dimensional unsteady Reynolds-Averaged Navier–Stokes simulations in the Reynolds number range of 10,000 30,000. The initial and upper branches of vortex induced vibration (VIV), transition from VIV to galloping, and galloping branch are clearly observed in the amplitude and frequency responses. The FIM responses of PTC-cylinder and Q-trapezoid I are stronger than the other cylinders. The maximum amplitude of 3.5D is achieved and 16 vortices are captured in one cycle in the fully-developed galloping branch. The optimum regime for energy harvesting is the VIV upper branch. And the PTC-cylinder and Q-trapezoid I have better performance on energy harvesting in FIM than other cylinders. The maximum energy efficiencies of 45.7% and 37.9% are achieved for Q-trapezoid I and PTC-cylinder respectively. Contrarily, the vibration of Q-trapezoid II (quasi-trapezoid cylinder with the short edge as the windward side) displays a quite different character with low amplitude and high frequency, and the vortex pattern is a constant 2S in the test Re range.

Clean energy conversion is a core approach and development trend to tackle climate change, while the severe drawbacks such as supply deficiency and cost increase restrict regional sustainable development. This paper employs a natural experiment of coal-to-gas conversion of the Chinese government to study the effect of such policy on regional sustainable development, as well as the underlying mechanism. Based on a city-level dataset from 2006 to 2019, this paper measure green total factor productivity (GTFP) using data envelopment analysis (DEA) combined with the Malmquist‒Luenberger productivity index. Then, this paper evaluates the impact of the CTG policy in pilot cities using the Difference-in-Difference (DID) with Propensity Score Matching (PSM) approach. This paper finds that the CTG policy increased the GTFP of the pilot cities by 2.25% (0.0229/1.02). A series of robustness tests confirmed the findings. Subsequent mechanism analysis shows that the CTG policy increases the GTFP of pilot cities mainly by increasing technical efficiency. In addition, the mechanism of the CTG policy's impact differs between central and noncentral cities. In particular, the CTG policy increases the technological innovation indicator (TC) of provincial capital cities by 2.35% while it increases the technical efficiency indicator (EC) of other cities by 1.89%, which proves the Porter effect in provincial capital cities. Finally, several implications are provided for policymakers to promote other types of renewable energy.

There are few empirical studies concerning the impact of information communication technology (ICT) on energy intensity in developing countries. We introduce an expanded STIRPAT model and China's provincial data samples during 2003–2012 to fill this gap. This paper applies the Driscoll–Kraay econometric method to assess the long-term impact of ICT investment on energy intensity and employs a panel error correction model to explore the short-term influence. The results indicate that the ICT investment significantly reduces energy intensity in the long-run, while it does not in the short-run at a nationwide level. Concerning the regional diversities of China, the impact of the ICT investment on energy intensity is significantly negative in western and central regions, while is insignificant in the eastern sample. Furthermore, the negative impact grows as the ICT investment increases in central provinces. Additionally, the short-term energy intensity reduction effect exists only in eastern regions, while it does not in central provinces. The ICT investment increases the energy intensity in the short-run in the western sample.

Abstract As distributed generations (DGs) are occupying an increasing proportion in active distribution network, the fluctuation of bus voltage becomes severe because of their intermittent and stochastic characteristics. Energy Storage System (ESS) can be adopted as an effective means to mitigate this fluctuation. This paper proposes a methodology for the optimal allocation of ESSs based on the novel optimal affine power flow (OAPF) approach. Affine models of wind turbine generation (WTG), photovoltaic (PV) system, and ESS are built while considering uncertainty characters of their power outputs. The objective function is set to minimize the capital investment of ESSs and the penalty costs of bus voltage fluctuations. The complex affine arithmetic based distribution power flow is used to ensure that constraints on power flow limits, voltage limits, and ESS operational limits are satisfied. The optimization problem is solved by an improved immune genetic algorithm (IIGA). The proposed approach is verified via a modified IEEE 33-bus system with a high penetration of DGs. Results show that the optimal allocation of ESSs can satisfy both the technical and economic requirements under such an uncertain environment.

In order to effectively develop the benefit evaluation model of prefabricated houses in seasonal frozen soil areas, and improve the comprehensive benefits of prefabricated buildings, this paper proposes a life cycle benefit evaluation model for prefabricated buildings in seasonally frozen regions. According to the climatic characteristics of the area, the impact of the seasonally frozen regions is listed as an evaluation index in the construction stage for comprehensive analysis. The 16 indicators that affect the comprehensive benefits of prefabricated buildings are grouped by the nearest neighbor element analysis method. Fuzzy cluster analysis and analytic hierarchy process are used to filter out the most influential index group to calculate the index weight. Then the model proposed in this paper is compared with the existing model to test the validity of the model. The research results show that research and development costs weight is 0.23, design cost weight is 0.10, construction cost weight is 0.22, resource consumption weight is 0.25, building demolition cost weight is 0.04, and seasonal freezing effect weight is 0.16. The calculation result passed the consistency test and the expert scoring result conformed to the normal distribution, which proved the accuracy of the conclusion. It is proposed that the calculation result of the comprehensive benefit score of the model is 1.8% lower than the previous results, which proves the validity of the model. The model can speed up the efficiency of comprehensive benefit evaluation of prefabricated buildings thereby improving the development level of prefabricated buildings.