Scale Effect on Producing Gaseous and Liquid Chemical Fuels via CO2 Reduction

Producing chemical fuels from sunlight is a sustainable way to utilize solar energy and reduce carbon emissions. Within the current photovoltaic-electrolysis or photoelectrochemical-based solar fuel generation system, electrochemical CO2 reduction is the key step. Although there has been important progress in developing new materials and devices, scaling up electrochemical CO2 reduction is essential to promote the industrial application of this technology. In this work, we use Ag and In as the representative electrocatalyst for producing gas and liquid products in both small and big electrochemical cells. We find that gas production is blocked more easily than liquid products when scaling up the electrochemical cell. Simulation results show that the generated gas product, CO, forms bubbles on the surface of the electrocatalyst, thus blocking the transport of CO2, while there is no such trouble for producing the liquid product such as formate. This work provides methods for studying the mass transfer of CO, and it is also an important reference for scaling up solar fuel generation devices that are constructed based on electrochemical CO2 reduction.

Influences of Dielectric Constant and Scan Rate to Hysteresis Effect in Perovskite Solar Cell: Simulation and Experimental Analyses

In this work, perovskite solar cells (PSCs) with different transport layers were fabricated to understand the hysteresis phenomenon under a series of scan rates. The experimental results show that the hysteresis phenomenon would be affected by the dielectric constant of transport layers and scan rate significantly. To explain this, a modified Poisson and drift-diffusion solver coupled with a fully time-dependent ion migration model is developed to analyze how the ion migration affects the performance and hysteresis of PSCs. The modeling results show that the most crucial factor in the hysteresis behavior is the built-in electric field of the perovskite. The non-linear hysteresis curves are demonstrated under different scan rates, and the mechanism of the hysteresis behavior is explained. Additionally, other factors contributing to the degree of hysteresis are determined to be the degree of degradation in the perovskite material, the quality of the perovskite crystal, and the materials of the transport layer, which corresponds to the total ion density, carrier lifetime of perovskite, and the dielectric constant of the transport layer, respectively. Finally, it was found that the dielectric constant of the transport layer is a key factor affecting hysteresis in perovskite solar cells.

Theoretical and Methodological Features for Gas-condensate PVT Fluid Modelling with Limited Data

Majority of gas-condensate reservoir discoveries in Dnieper-Donets Basin (Ukraine), is characterized by limited composition only up to C5+, phase behavior studied by non-equilibrium, so called differential condensation PVT experiment, combined with the uncertainty in condensate production allocation to individual wells, makes the direct application of the results in modern PVT modeling software not possible. The new method, based on the Engler distillation test (ASTM86) for definition of pseudo-components combined with synthetic creation of liquid saturation curve for CVD experiment, was proposed and successfully applied for different gas-condensate reservoirs in the area of study. The quality control (QC) of the PVT model is further performed by applying material-balance method on a single-cell simulation model for exported black-oil PVT formulation when needed. The method proved being useful for modeling of multiple gas-condensate reservoirs of Dnieper-Donets Basin with different potential condensate yields varying from 30 to 700 g/m3 and as an example presented for two reservoir fluids with 108 and 536 g/m3. Results of numerical simulation studies were within the engineering accuracy in comparison to historically observed values. The investigation showed that a representative fluid model can be create in the cases when no detailed fluid composition or required laboratory experiments are available. PVT model can be efficiently validated and QC-ed by performing material-balance type numeric simulation constructed with one cell. However, the proper fluid sampling and PVT cell laboratory experiments are still major requirements for precise reservoir fluid characterization and equation of state (EOS) modeling.

Particle-in-cell Simulation of 3He Enrichment in Solar Energetic Particle Events

3He enrichment is one distinctive feature of impulsive solar energetic particle events. This study is designed to investigate the process of plasma wave–particle resonance, which plays a key role in selectively accelerating heavy ions. We apply a 1.5 dimensional particle-in-cell simulation to model the electron-beam–plasma interaction that generates electron and ion cyclotron waves, namely proton and 4He cyclotron waves, whose dispersions are dependent on the magnetization parameter α = ω pe/Ωce and the temperature ratio τ = T e /T p . The background particles, e.g., 3He and 4He, resonate with the excited cyclotron waves and experience selective heating or acceleration. Specifically, the resonant modes of 3He ions lead to a more effective acceleration rate compared to those of the 4He ions. The simulation results provide a potential solution for understanding the abundance of heavy ions in the solar wind.