Abdulaziz Almutairi

High-responsivity reduced graphene oxide gel photodetectors for visible-light detection with a large detection area and an end-contact interface

Herein, the engineering and characterization of a photodetector using reduced graphene oxide gel (femtogel) as an active material are reported for the first time. The photodetector is engineered such that it contains a large detection area (interdigitated) and a femtogel–metal interface. The femtogel film is precisely placed between the interdigitated electrodes, which allows us to study the performance of the photodetector that has an end-contact interface. The femtogel width (channel) is controlled by adjusting the reactive ion etching processing time during the fabrication process. In addition, the thickness of the poly(methyl methacrylate) (PMMA) and electron-beam dose during the lithography process plays a significant role in initializing a window for etching the femtogel, which affects the channel width. In the visible range, a high responsivity has been achieved as high as 0.73 A W−1 at a low power intensity of 84 mW cm−2. Moreover, 3.4 s and 5.2 s are recorded as the time response of the photocurrent for growth and decay, respectively, in the proposed femtogel photodetector. This could open a new avenue for the fabrication of graphene-based photodetectors since placing graphene and its derivatives that are in liquid form between electrodes in a nanoscale detector is still a challenge in advanced nanofabrication.

Inclusion of Wind Generation Modeling into the Conventional Generation Adequacy Evaluation

Wind energy has become a significant portion of power generation resources, consequently its variability and uncertainty introduces various challenges for both the operation and planning of power systems. One of the great challenges of integrating wind energy in power systems can be seen from the reliability assessment perspective. Indeed, there is an ongoing recognized need to study the contribution of wind generation to overall system reliability and to ensure the adequacy of generation capacity. With respect to the evaluation of the reliability of power systems incorporating wind energy, a variety of criteria and techniques have been developed over the years. This paper is dedicated to reviewing the literature pertaining to generating system adequacy assessment in general and with regard to wind energy in particular. This paper firstly reviews the concepts and related aspects of generating system adequacy assessment, it also includes detailed description of the involved elements and the available widely commonly-used techniques. Then, it discusses the main issues arising when implementing wind generation into the adequacy assessment of generating systems. Moreover, the paper surveys the previously reported works that have proposed to involve wind generation into adequacy assessment.

Label-Free and Recalibrated Multilayer MoS2 Biosensor for Point-of-Care Diagnostics

Molybdenum disulfide (MoS2) field-effect transistor (FET)-based biosensors have attracted significant attention as promising candidates for highly sensitive, label-free biomolecule detection devices. In this paper, toward practical applications of biosensors, we demonstrate reliable and quantitative detection of a prostate cancer biomarker using the MoS2 FET biosensor in a nonaqueous environment by reducing nonspecific molecular binding events and realizing uniform chemisorption of anti-PSA onto the MoS2 surface. A systematic and statistical study on the capability of the proposed device is presented, and the biological binding events are directly confirmed and characterized through intensive structural and electrical analysis. Our proposed biosensor can reliably detect various PSA concentrations with a limit of 100 fg/mL. Moreover, rigorous theoretical simulations provide a comprehensive understanding of the operating mechanism of the MoS2 FET biosensors, and further suggests the enhancement of the sensitivity through engineering device design parameters.

Quantifying the impact of PEV charging loads on the reliability performance of generation systems

Plug-in electric vehicle (PEV) charging load represents a large and uncontrollable load that behaves far differently from a conventional load. This paper presents a methodology for evaluating the adequacy of the power capacity of systems that include PEV charging loads. A probabilistic analytical approach has been employed using an IEEE reliability test system. The PEV charging load is modeled based on the National Household Travel Survey and on currently available market data pertaining to PEV type and charging level. Also presented is the effect on the adequacy indices of each PEV load parameter, specifically penetration level, PEV type, and charging level. A further case study was conducted in order to evaluate the impact of the current time-of-use tariff in response to the expected increase in power demand due to the massive deployment of PEVs. The results show that the addition of PEVs significantly affects the generation reliability, and that higher charging levels and PEVs with greater battery capacity create a severe risk to generation reliability. Investigation of solutions that maintain reliability indices is therefore required.

Assessment of Germanane Field-Effect Transistors for CMOS Technology

Using self-consistent atomistic quantum transport simulations, the device characteristics of n-type and p-type germanane (GeH) field-effect transistors (FETs) are evaluated. While both devices exhibit near-identical off-state characteristics, n-type GeH FET shows ~40% larger on current than the p-type counterpart, resulting in faster switching speed and lower power-delay product. Our benchmark of GeH FETs against similar devices based on 2D materials reveals that GeH outperforms MoS2 and black phosphorus in terms of energy-delay product (EDP). In addition, the performance of GeH-based CMOS circuit is analyzed using an inverter chain. By engineering power supply voltage and threshold voltage simultaneously, we find the optimal operating condition of GeH FETs, minimizing EDP in the CMOS circuit. Our comprehensive study, including material parameterization, device simulation, and circuit analyses, demonstrates significant potential of GeH FETs for 2D-material CMOS circuit applications.

Effect of wind turbine parameters on optimal DG placement in power distribution systems

The notion of the “smart grid” has led stakeholders in the power industry to promote more efficient technologies to the network. Distribution systems are a favorite place to host most of these technologies including Renewable-based distributed generation (DG). Wind Turbine Generators (WTGs) in particular have proved their usefulness for supplying a fair portion of power demand; however, the power output of WTGs is mainly dependent on the stochastic nature of the sites wind speed in addition to the design parameters of WTGs. Furthermore, WTGs can only be suitably utilized when their capacities and locations are optimized in such a way to achieve certain goals. In this paper, the effect of wind generator design parameters, namely cut-in, cut-out, and rated wind speeds, on the problems of sizing and siting WTGs-based DGs is addressed. The probabilistic optimization model is used to minimize the systems annual energy losses, and the results reveal that the design parameters of WTGs must be carefully selected due to their strong effect on system losses and DG locations and capacities.

Statistical evaluation study for different wind speed distribution functions using goodness of fit tests

Modeling wind generation for use in many power system applications requires a massive database of historical wind speeds so that the stochastic nature of the wind at a particular site can be accurately analyzed. The alternative is to use reliable estimates of a probability distribution function (PDF) that can preserve the variable characteristics of wind speed and generate the desired synthetic data. This paper presents a statistical evaluation study for different collections of PDFs in order to find the best model to precisely reflect the variable characteristics of the wind at a particular site. The most commonly used PDFs, along with some advanced PDFs, have been verified against the observed wind data based on consideration of two well-known goodness of fit statistical tests. A further case study is conducted in order to evaluate the impact of sample size on the selection of the best-fit PDFs. From a variety of candidate PDFs, the results indicate that the Generalized Logistic and Dagum distributions are the PDFs that best maintain the main characteristics of the observed wind data.

Evaluation of the Generating Capacity Adequacy of the Saudi Arabian Central Operating Area

Abstract The goal of the study presented in this article was to evaluate the adequacy of the generation capacity of the Central Operating Area in Saudi Arabia. The generating capacity adequacy was evaluated to examine the ability of the generating capacity of the system to meet the total system demand. Over the last five decades, several probabilistic methods have been developed as a means of conducting such an evaluation. Three probabilistic simulation techniques were used for the evaluation of the designated system for this study: analytical, sequential, and non-sequential Monte Carlo. A variety of reliability indices, such as loss of load expectation and loss of energy expectation, were obtained.