Steady Energy

Yuqi Wang, Xin Yu, Yin Mengfei, Jianlong Wang, Qi Gao, Yang Yu, Tinghai Cheng, Z. Wang

Abstract Triboelectric nanogenerator (TENG), as a renewable energy harvesting technology, has been verified as an effective approach for converting mechanical energy into electric energy. In a natural environment, the unsteadiness of TENG energy harvesting restricts the application and development of TENG. From this perspective, a gravity triboelectric nanogenerator (G-TENG) is developed for the first time to convert natural wind energy into steady electric energy, achieving the steady harvesting of natural wind energy. The G-TENG mainly comprises an energy input module, energy storage module, and energy output module. Random wind energy is transmitted from the input module to the storage module and converted into gravitational potential energy. Steady electric energy is ultimately obtained from the output module. The standard deviation (ISD) of the short-circuit current peaks is under 0.31 μA. Additionally, the fluctuation degree (IFD) of the short-circuit current peaks is defined to describe the steady output capability of TENG. IFD of the G-TENG can reach 2.3%. A steady current is thus achieved by the G-TENG in a natural environment. This research provides essential guidance for the steady harvesting of natural energy by the TENG.

E. Erdem, K. Kontis, L. Yang

Lixun Chi, Huai Su, E. Zio, Meysam Qadrdan, Jing Zhou, Li Zhang, Lin Fan, Zhaoming Yang, F. Xie, Lili Zuo, Jinjun Zhang

The reliability analysis of IESs (Integrated Energy Systems) is a complicated task because of the complex characteristics of different subsystems and the multi-scale dynamics that develop therein. To effectively address such problems, this paper proposes a systematic framework to analyse the reliability of energy supply in IESs, considering the dynamics of IESs and the inter-relationships among uncertainties. First, based on the linepack-based performance analysis model of IES, a quasi-steady-state model is established to model the dynamic behaviours in IESs, properly accounting for practical engineering and operational strategies. Then, considering the inter-correlations among different uncertainty sources and time-dependent relationships of each variable, a model that combines the statistical structure of copula with the machine learning method of stacked autoencoder (CSML) is adopted to establish the timely multivariate joint distributions for variables. Monte Carlo simulation combined with Order Statistics is used for assessing supply reliability. Case studies are performed on a realistic IES that combines an IEEE-15 power system with an 18-node natural gas pipeline network. The efficiency and accuracy of the quasi-steady-state model are validated. The reliability evaluation results show that the inter-correlations among variables and time-dependent relationships of each variable have great effects on the system reliability assessment. The consideration of linepack can significantly improve the supply reliability of IES whereas the management strategy of linepack may lead to some risky points.

Jia Su, H. Chiang, Yuan Zeng, N. Zhou

The steady-state security region of the integrated energy system (IES) is a useful tool for rapid security assessment and security evaluation of the integrated energy system. A complete characterization of the IES steady-state security region is derived. The derivation is under the nonlinear and non-convex AC power flow model, the gas flow model, and the uncertainty of renewable energy without any linear simplification. Then a novel and robust computation scheme to compute the IES steady-state security region is proposed and shown to eliminate the estimation errors of the existing methods. It is shown that the IES steady-state security region is non-convex and composed of several disjoint components. Numerical studies are conducted to show that the IES steady-state security regions obtained from the existing methods can be inaccurate, while the proposed characterization gives an exact estimation of the IES steady-state security region that significantly improves the previously proposed methods.

B. Low, T. Berger, R. Casini, W. Liu

This series of papers investigates the dynamic interiors of quiescent prominences revealed by recent Hinode and SDO/AIA high-resolution observations. This first paper is a study of the static equilibrium of the Kippenhahn–Schlüter diffuse plasma slab, suspended vertically in a bowed magnetic field, under the frozen-in condition and subject to a theoretical thermal balance among an optically thin radiation, heating, and field-aligned thermal conduction. The everywhere-analytical solutions to this nonlinear problem are an extremely restricted subset of the physically admissible states of the system. For most values of the total mass frozen into a given bowed field, force balance and steady energy transport cannot both be met without a finite fraction of the total mass having collapsed into a cold sheet of zero thickness, within which the frozen-in condition must break down. An exact, resistive hydromagnetic extension of the Kippenhahn–Schlüter slab is also presented, resolving the mass-sheet singularity into a finite-thickness layer of steadily falling dense fluid. Our hydromagnetic result suggests that the narrow, vertical prominence Hα threads may be falling across magnetic fields, with optically thick cores much denser and ionized to much lower degrees than conventionally considered. This implication is discussed in relation to (1) the recent SDO/AIA observations of quiescent prominences that are massive and yet draining mass everywhere in their interiors, (2) the canonical range of 5–60 G determined from spectral polarimetric observations of prominence magnetic fields over the years, and (3) the need for a more realistic multi-fluid treatment.