Joshua Clarke

Comparison of genetic algorithm to particle swarm for constrained simulation-based optimization of a geothermal power plant

The performance of a genetic algorithm is compared with that of particle swarm optimization for the constrained, non-linear, simulation-based optimization of a double flash geothermal power plant. Particle swarm optimization converges to better (higher) objective function values. The genetic algorithm is shown to converge more quickly and more tightly, resulting in a loss of solution diversity. Particle swarm optimization obtains solutions within 0.1% and 0.5% of the best known optimum in significantly fewer objective function evaluations than the genetic algorithm.

A passive house with seasonal solar energy store: in situ data and numerical modelling

This paper presents parametric analysis of solar collector area and solar energy storage volume for a passive house in Galway, Ireland. Using the simulation tool Transient System Simulation Tool (TRNSYS), a model was developed to represent a 215 m2 home built to Passivhaus standards and incorporating a 10.6 m2 solar thermal collector and a 23 m3 solar thermal storage tank. This model was validated through comparison with data collected in situ from the operation of the home over the period of 1 year. Once validated, the model was used to investigate the effect of varying solar collector area and solar energy storage volume on the fraction of heat demand met by solar energy. Results indicate that increasing collector area from 10.6 to 20 m2 could increase total solar fraction from 0.47 to 0.63, decreasing fossil-fuel-derived energy demand at the home under study by a further 30%.

Thickness ratio effects on quasistatic actuation and sensing behavior of laminate magnetoelectric cantilevers

In this work, the magnetoelectric cantilever composed of a layer of Galfenol and a layer of PZT-5H is studied for novel applications such as surgical ablation tools and cutting tools for machining applications. For developing a suitable model for the magnetoelectric cantilever, an energy based approach for the non-linear constitutive behavior of the magnetostrictive material and linear piezoelectric constitutive equations will be coupled with Euler Bernoulli model for composite beams. The cantilever is held in a uniform magnetic field and the magnetic field is measured by a Gaussmeter. The tip-deflection of the cantilever is detected by a laser triangulation sensor. The piezoelectric response can be studied with low noise preamplifier. Four PZT-5H layers with different thickness are separately bonded on the top of the same Galfenol layer and characterized to study the thickness ratio effects on the quasistatic actuation and sensing behavior of the composite cantilever.

Hybrid TiO2 Solar Cells Produced from Aerosolized Nanoparticles of Water-Soluble Polythiophene Electron Donor Layer

Hybrid solar cells (HSCs) with water soluble polythiophene sodium poly[2-(3-thienyl)-ethyloxy-4-butylsulfonate] (PTEBS) thin films produced using electrospray deposition (ESD) were fabricated, tested, and modeled and compared to devices produced using conventional spin coating. A single device structure of FTO/TiO2/PTEBS/Au was used to study the effects of ESD of the PTEBS layer on device performance. ESD was found to increase the short circuit current density () by a factor of 2 while decreasing the open circuit voltage () by half compared to spin coated PTEBS films. Comparable efficiencies of 0.009% were achieved from both device construction types. Current-voltage curves were modeled using the characteristic solar cell equation and showed a similar increase in generated photocurrent with an increase by two orders of magnitude in the saturation current in devices from ESD films. Increases in are attributed to an increase in the interfacial contact area between the TiO2 and PTEBS layers, while decreases in are attributed to incomplete film formation from ESD.

Design and fabrication of a microscale magnetoelectric surgical tool

Magnetoelectric materials made from magnetostrictive and piezoelectric constituents are best suited for selfsensing actuators. The relationship between applied magnetic field (force), tip displacement (deflection) and current output (sensing signal) is necessary for the development of self-sensing actuator systems. The dynamic behavior of the constituent magnetostrictive materials and piezoelectric materials independent of each other are well-understood. The coupled dynamic force-strain-sensing behavior of magnetoelectric materials as selfsensing actuators is largely unexplored and provides the motivation for our work in this area. This paper presents theoretical and experimental analysis of the dynamic behavior of a Metglas/PVDF magnetoelectric laminate composite. Experimental results for the mechanical and electrical behavior of a 15mm × 30mm × 75μm Metglas/PVDF cantilever beam across the frequency spectrum are compared to those predicted by an equation of motion developed using the principle of virtual work and Hamiltonian principle. The theoretically developed model predicts the observed displacement and sensing current within 35% and 20% respectively. A parametric analysis is presented to determine the optimum design parameters of the composite for self-sensing actuation.

Static and dynamic characterization of a magnetoelectric cantilever cutting tool

A magnetoelectric self-sensing cantilever actuator is under investigation for use as a remotely driven self-sensing actuator. The cantilever is fabricated from Galfenol and Lead Zirconate Titanate strips as a laminate composite. An applied magnetic field generates strain in the magnetostrictive layer, thereby creating a bending moment in the composite and generating an electrical signal in the piezoelectric layer. A force-deflection model and equation of motion for the self-sensing magnetoelectric material in cantilever configuration is developed in this paper. An equivalent mass and stiffness matrix derived for the cantilever in terms of generalized coordinates is used to predict the bending behavior of the cantilever in its linear range of operation. In addition, the electrical boundary condition of the piezoelectric layer is varied to determine its influence on the actuation properties of the cantilever tool. Cantilever specimens measuring 40mm x 20mm and 20mm x 10mm are excited using a remote magnetic field of up to 2.8x104 A/m and free tip displacements of 200μm and 60 μm are observed, respectively. The model predicts the slope of the magnetic field/tip displacement curve with an error of 7% and 33%, respectively. The sensing current generated by the smaller specimen is 5x10-7 A.

Dynamic Characterization of a Magnetoelectric Cantilever for Actuation and Sensing

This article continues our work to develop magnetoelectric materials as self-sensing actuators. Our research is directed at developing a two-segment cantilever device with closed-loop control. The actuator under study is fabricated as a laminated composite of the magnetostrictive material Iron-Gallium (Galfenol) and a Lead-Zirconate-Titanate piezoelectric material (PZT-5H). The mechanical and electrical characteristics of a single-segment cantilever are modeled using the equation of motion developed from variational principles in earlier work and are compared with experimental data from other groups. Additionally, parametric analysis is performed to determine the effect of varying the thickness fraction of the piezoelectric layer on the frequency response characteristics of the actuator. When applied to the dynamic behavior of the actuator, the model predicts behavior that closely resembles experimental results published by other groups. Parametric analysis of the piezoelectric layer thickness fraction indicates that the design of a magnetoelectric cantilever self-sensing actuator can be optimized by varying the thickness fraction.Copyright