Demand response (DR) control can effectively relieve balancing and frequency regulation burdens on conventional generators, facilitate integrating more renewable energy, and reduce generation and transmission investments needed to meet peak demands. Electric water heaters (EWHs) have a great potential in implementing DR control strategies because: a) the EWH power consumption has a high correlation with daily load patterns; b) they constitute a significant percentage of domestic electrical load; c) the heating element is a resistor, without reactive power consumption; and d) they can be used as energy storage devices when needed. Accurately modeling the dynamic behavior of EWHs is essential for successfully designing DR controls. In this paper, a new partial differential equation (PDE) physics-based model is developed to capture the detailed temperature profiles at different tank locations, which is validated against field test data for more than 10 days. The developed PDE model is compared with the one-mass and two-mass models, and shows better performance in capturing water thermal dynamics for benchmark testing purposes.

A phase-field approach to the dynamics of liquid-solid interfaces that evolve due to precipitation and/or dissolution is presented. For the purpose of illustration and comparison with other methods, phase-field simulations were carried out assuming first order reaction (dissolution/precipitation) kinetics. In contrast to solidification processes controlled by a temperature field that is continuous across the solid/liquid interface (with a discontinuous temperature gradient), precipitation/dissolution is controlled by a solute concentration field that is discontinuous at the solid/liquid interface. The sharp-interface asymptotic analysis of the phase-field equations for solidification [A. Karma and W.-J. Rappel, Phys. Rev. E 57, 4323 (1998)] has been modified for precipitation/dissolution processes to demonstrate that the phase-field equations converge to the proper sharp-interface limit. The mathematical model has been validated for a one-dimensional precipitation/dissolution problem by comparison with the analytical solution.

Polyolefin separators are the most common separators used in rechargeable lithium (Li)‐ion batteries. However, the influence of different polyolefin separators on the performance of Li metal batteries (LMBs) has not been well studied. By performing particle injection simulations on the reconstructed three‐dimensional pores of different polyethylene separators, it is revealed that the pore structure of the separator has a significant impact on the ion flux distribution, the Li deposition behavior, and consequently, the cycle life of LMBs. It is also discovered that the homogeneity factor of Li‐ion toward Li metal electrode is positively correlated to the longevity and reproducibility of LMBs. This work not only emphasizes the importance of the pore structure of polyolefin separators but also provides an economic and effective method to screen favorable separators for LMBs.

We report an investigation of growth kinetics and transition from thin to thick films during metal oxidation. In the thin film limit (<20 nm), Cabrera and Mott's theory is usually adopted by explicitly considering ionic drift through the oxide in response to electric fields, where the growth kinetics follow an inverse logarithmic law log(dl/dt) ∝ 1/l. It is generally accepted that Wagner's theory, involving self-diffusion, is valid only in the limit of thick film regime (>1 μm) and leads to parabolic growth kinetics dl/dt ∝ 1/l, where l is the oxide film thickness. Theory presented here unifies the two models and provides a complete description of oxidation including the transition from thin to thick film. The range of validity of Cabrera and Mott's theory and Wagner's theory can be well defined in terms of the Debye–Hückel screening length. The transition from drift-dominated ionic transport for thin film to diffusion-dominated transport for thick film is found to strictly follow the direct logarithmic law log(dl/dt) ∝ −l that is frequently observed in many experiments.