arXiv subjects

Zhaojian Liang

Publications and source records attributed to Zhaojian Liang.

3 recordsLinked to original sources

arXiv2024

Characteristic time of transient response of solid oxide cells (SOCs) to changes in voltage/current: from theory to applications

The intermittency of solar and wind power can be addressed by integrating them with Solid Oxide Cells (SOCs). This study delves into the transient characteristics of SOCs and their dependence on dynamic heat and mass transfer processes. Non-dimensional analysis was used to identify influential parameters, followed by a 3-D numerical simulation-based parametric analysis to examine the dynamic gaseous and thermal responses of SOCs with varying dimensions, material properties, and operating conditions. For the first time, we proposed characteristic times to describe the relationship between SOC transients and multiple parameters. These characteristic times represent the overall heat and mass transfer rats in SOCs. Their effectiveness was validated against literature and demonstrated potential in characterizing the transient characteristics of other electrochemical cells. Besides, two examples are provided to illustrate how the characteristic times facilitate SOC design and control at minimal computational cost.

physics.flu-dyn↗

arXiv2024

Efficient Estimation of the Convective Cooling Rate of Photovoltaic Arrays with Various Geometric Configurations: a Physics-Informed Machine Learning Approach

Convective heat transfer is crucial for photovoltaic (PV) systems, as the power generation of PV is sensitive to temperature. The configuration of PV arrays have a significant impact on convective heat transfer by influencing turbulent characteristics. Conventional methods of quantifying the configuration effects are either through Computational Fluid Dynamics (CFD) simulations or empirical methods, which face the challenge of either high computational demand or low accuracy, especially when complex array configurations are considered. This work introduces a novel methodology to quantify the impact of geometric configurations of PV arrays on their convective heat transfer rate in wind field. The methodology combines Physics Informed Machine Learning (PIML) and Deep Convolution Neural Network (DCNN) to construct a robust PIML-DCNN model to predict convective heat transfer rates. In addition, an innovative loss function, termed Pocket Loss is proposed to enhance the interpretability of the PIML-DCNN model. The model exhibits promising performance, with a relative error of 1.9\% and overall $R^2$ of 0.99 over all CFD cases in estimating the coefficient of convective heat transfer, when compared with full CFD simulations. Therefore, the proposed model has the potential to efficiently guide the configuration design of PV arrays for power generation enhancement in real-world operations.

physics.flu-dyn↗

arXiv2024

A novel control strategy to neutralize heat source within solid oxide electrolysis cell (SOEC) under variable solar power conditions

The integration of a solid oxide electrolysis cell (SOEC) with a photovoltaic (PV) system presents a viable method for storing variable solar energy through the production of green hydrogen. To ensure the SOEC's safety and longevity amidst dramatic fluctuations in solar power, control strategies are needed to limit the temperature gradients and rates of temperature change within the SOEC. Recognizing that the reactant supply influences the current, a novel control strategy is developed to modulate heat generation in the SOEC by adjusting the fuel flow rate. The effectiveness of this strategy is assessed through numerical simulations conducted on a coupled PV-SOEC system using actual solar irradiance data, recorded at two-second intervals, to account for rapid changes in solar exposure. The results indicate that conventional control strategies, which increase airflow rates, are inadequate in effectively suppressing the rate of temperature variation in scenarios of drastic solar power changes. In contrast, our proposed strategy demonstrates successful management of the SOEC's heat generation, thereby reducing the temperature gradient and rate of variation within the SOEC to below 5 K/cm and 1 K/min, respectively.

physics.flu-dyn↗