Performance investigation of the crossflow water turbine by using CFD

Crossflow water turbines can be an alternative energy for the development of pico-hydro power plants. Multiple interactions that occur from the flow of fluid that collides with the blade is one of the advantages of the crossflow type so that this turbine has a high power coefficient. The power coefficient of a turbine is influenced by several factors, including the blade depth ratio and blade number. The objective of this research was to study the effect of blade depth ratio and blade number on the power coefficient of crossflow water turbines. This research was done in 2 dimensions method (2D) using ANSYS Fluent software. Variations of blade depth ratios used in this study were 10%, 20%, and 30%, while variations of the blade number were 16, 19, and 22. Each variation was tested at tip speed ratio (TSR) 0, 0.109, 0.218, 0.327, and 0.436 with a constant water velocity of 3 m/s. The results of this research indicated that the crossflow water turbine at TSR 0.436 with blade depth ratio of 10% and blade number of 16 generated the highest power coefficient, which was equal to 0.187

Controller development of a passive control ankle foot orthosis

This article focuses its efforts on the development of passive control foot orthosis featuring magnetorheological (MR) brake actuator. The MR brake was hypothesized as the ideal actuator due to it being able to generate actual braking torque according to the controller’s desire. Here, the EMG sensor was utilized as the signal input of the foot movement. Meanwhile, the output of controller was driven to the MR brake in the form of direct current (DC). Fuzzy logic control was employed as the control strategy. The performance of the controller was evaluated experimentally. From the experiment, the controller was observed as able to perform as expectation theorized, measured through the output voltage and sensor inputs. However, the MR brake torque continues to receive little acknowledgement which could be due to insufficient output torque

Performance prediction of serpentine type compact magnetorheological brake prototype

A magnetorheological brake (MRB) with serpentine flux type for ankle-foot orthosis (rehabilitation device) was assessed its performance regarding braking torque and dynamic range. This assessment was conducted based on a problem that the MRB did not generate sufficient braking torque for the orthosis device. The braking capability was appraised through analytical approached based on the prototype design. The magnetic circuit of the MRB design was firstly investigated its capability for generating magnetic flux at braking surface area using finite element method magnetic (FEMM) software. Governing equation was derived to determine the braking performance i.e. braking torque and dynamic range as a function of applied current. The main factors influencing the braking performance were magneto-induced shear stress, the clearance between rotor and stator, and braking surface area. Especially for shear stress, this factor was totally influenced by the magnetic flux generated within the braking area. These all factors were contained within the governing equation. Furthermore, the braking performances were determined by solving the governing equation according to the design parameters. As a result, the governing equation can be used for improving the MRB design to get a better braking performances

Disordered polymer antireflective coating for improved perovskite photovoltaics

Light management through low index medium, such as antireflective coating (ARC) provides practical solution to improve the efficiency of photovoltaics. However, a brute-force development of photonic structure on ARC is not necessarily useful, because of random scattering associated with impediment of light transmission. Here, we leverage the concept of disorder, rather than random, structured on ARC for improving efficiency without modifying original architecture of thin-film photovoltaics. We demonstrate a disordered polymer that leads to a total reflectance of 5% while demonstrating a high transmission of 94% across 300 to 820 nm wavelength. Next, we find that the arrangement of disordered points and line arrays constructing the polymer seems to be the key to control bandwidth performance of the ARC. Finally, we apply this into Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 perovskite, and through experiments with wave-optics and full-device simulation, show a 1.6-fold absorption gain leading to 19.59% power-conversion-efficiency by the disordered ARC.Ministry of Education (MOE)National Research Foundation (NRF)Accepted versionThis work is supported by the National Research Foundation, Prime Minister’s Office, Singapore under Energy Research Innovation Program (Grant number, NRF2015EWT-EIRP003-004 and NRF-CRP14-2014-03 and Solar CRP:S18-1176-SCRP), and Ministry of Education (MOE2016‐T2‐1‐052)