Compressed air energy storage (CAES) could play an important role in balancing electricity supply and demand when linked with fluctuating wind power. This study aims to investigate design and operation of a CAES system for wind power at design and off-design conditions through process simulation. Improved steady-state models for compressors, turbines and the CAES system for wind power were developed in Aspen Plus ® and validated. A pseudo-dynamic model for cavern was developed in Excel. Compressor and turbine characteristic curves were used in model development for process analysis. In the off-design analysis, it was found that the CAES system for wind power at variable shaft speed mode utilise more excess wind energy (49.25MWh), store more compressed air (51.55×10 3 kg), generate more electricity (76.00MWh) and provide longer discharging time than that at constant shaft speed mode. Economic evaluation based on levelized cost of electricity (LCOE) was performed using Aspen Process Economic Analyser ® , it was found that LCOE for the CAES system for wind power at variable shaft speed mode is lower than that at constant shaft speed mode. Research presented in this paper hopes to shed light on design and operation of the CAES system for wind power and cost reduction.

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Reservoir fracture evaluation is an important research topic in the coalfield. In recent years, complex resistivity (CR) has been widely used in oil logging and achieved good results, such as permeability evaluation, water saturation (Sw) prediction, and aquifer identification. Therefore, the method has the potential to evaluate coal seam fracture. In the experiment, the real part R and imaginary part X of bituminous and anthracite coal with different Sw were measured by the impedance measuring instrument, then the Double Cole-Cole model was used to fit experimental data and analyze conductive mechanism. The main results are as follows: (1) the dispersion of CR parameters Reρ and Imρ is closely related to the metamorphism degree, frequency, and Sw; (2) induced polarization is the fundamental reason for the variation of coal samples’ complex resistivity parameters with frequency change; and (3) the Double Cole-Cole model agrees well with the experimental data, and the model parameters m1 and τ2 are strongly correlated with Sw. The parameters m1 and τ2 can be used to evaluate the Sw of fractures in coal seams and thus to evaluate the effect of hydraulic fracturing.

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