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The coordination of electricity and natural gas systems has ever been intensifying due to a growing share of natural gas-fired generating units in electricity production. Accordingly, concerns of the interrelationship between the coupled electricity and natural gas markets are emerging. Given this background, an Integrated Energy System (IES) with gas turbines, combined heat and power systems (CHP), distributed generation units, power-to-gas (P2G) facilities and multi-energy storage systems (ESSs) is first described. The operation strategy for the IES is investigated in a low-carbon context. Then, the Copula method is employed to model the joint probability distribution of electricity and natural gas prices. An optimal operation strategy of the IES is proposed to minimize the total operating cost, with the interdependence structure of electricity and natural gas prices well taken into account. Finally, a solution approach and case studies are presented, and the effectiveness of the proposed method demonstrated.

In the applications of heating generation based on the solid oxide fuel cells (SOFC) technology, a high-accuracy performance of flow measurement is of great importance. Due to the advantage of non-invasive no-moving-parts construction and bi-direction measurement, ultrasonic flow meter, where viscothermal dissipation and asymmetric acoustic modes cannot be overlooked, may be a promising method in the SOFC-based applications. The present paper mathematically formulates asymmetric linear disturbance dynamics in terms of velocity and temperature disturbances based on the conservations of mass, momentum and energy. An iterative calculation procedure, which is similar to Galerkin method, is presented. Numerical analysis of asymmetric acoustic features (phase velocity and attenuation coefficient) are comprehensively given under the effects of viscothermal dissipation and shear flow convection. In the end, flow measurement performance of asymmetric acoustic modes is literally discussed. Numerical study shows that viscothermal dissipation affects the cut-on frequency of acoustic modes and couples nonlinearly with shear convection when the flow Mach number is large. These parameters impose significant influences on measurement performance. Each acoustic mode has inherent measurement derivation which can be theoretically used to compensate the acoustic flow measurement error. Apparent prediction error may occur if the viscothermal dissipation is taken out of consideration.