Small-Scale Power Generation and Storage Using Piezoelectric Films

2011 ◽  
Author(s):  
Theodore Hatch ◽  
John Styrvoky ◽  
Jared Barton ◽  
Hualiang Zhang ◽  
Gayatri Mehta ◽  
...  
Keyword(s):  
Power Output ◽  
Polyvinylidene Fluoride ◽  
Bluff Body ◽  
Piezoelectric Materials ◽  
Buck Converter ◽  
Small Scale ◽  
Super Capacitor ◽  
Wind Speeds ◽  
Silver Ink ◽  
Piezoelectric Films

Piezoelectric materials have many applications including sensors, actuators, and motors. However, the ability of piezoelectric films to generate electricity from wind power has only recently been advanced. Piezoelectric films harvest wind energy by means of a layer of polyvinylidene fluoride (PVDF) that upon deformation generates an internal electrical voltage across two silver-ink electrodes. These films are allowed to freely flap in an airflow to cause deformation and thus electricity generation. A single small film (4.14 cm (1.63 in) × 1.63 cm (0.64 in) × 0.15 cm (0.06 in)) is tested at various wind speeds. The output of the film may be enhanced with the addition of a bluff body (in this case, a cylinder) upstream from the film. The vortex shedding from the cylinder produces a wake that can enhance the vibrations of the piezoelectric device, which in turn optimize voltage and/or power output. Voltage and power output is recorded across varying load resistances. The method of storing useful energy from the piezoelectric films is also of particular interest. Preliminary experiments using a LTC3588-1 energy harvester to various configurations of supercapacitors and Li-ion batteries are conducted. The LTC3588-1 is comprised of an efficient rectifier with a buck converter to allow the chip to efficiently charge the super capacitor while only requiring a small input to begin charging.

The Effect of the Configuration of the Amplification Device on the Power Output of a Piezoelectric Strip

2012 ◽  
Author(s):  
Jesse M. McCarthy ◽  
Arvind Deivasigamani ◽  
Sabu J. John ◽  
Simon Watkins ◽  
Floreana Coman
Keyword(s):  
Aspect Ratio ◽  
Power Output ◽  
Polyvinylidene Fluoride ◽  
Leading Edge ◽  
Wind Speeds ◽  
Start Up ◽  
Piezoelectric Strip ◽  
Power Measurements ◽  
System 1 ◽  
Leaf Parameters

We investigated the behaviour of a polyvinylidene-fluoride piezoelectric strip (‘stalk’) clamped at the leading edge, and hinged to an amplification device (‘leaf’) at the trailing edge. Flutter of this cantilevered system was induced within smooth, parallel flow, and an AC voltage was generated from the PVDF strip. A polypropylene, triangle comprised the leaf. Two leaf parameters were varied so as to quantify their effect on the power output of the system: 1) the area, and 2) the aspect ratio. It was found that the highest power output was realised with the 2nd-largest leaf across a range of wind speeds, but the variation in power measurements was large. Thus, the 3rd-largest leaf was found to give the highest power output with the lowest power variation. This leaf area was then fixed and the aspect ratio varied. It was found that the largest aspect ratio-leaf rendered the highest power output, but had a relatively high start-up wind speed.

Experimental Study and Optimization of a 2.44 Meter Vertical Axis Wind Turbine

2011 ◽  
Author(s):  
Brad Nichols ◽  
Timothy Dimond ◽  
Josh Storer ◽  
Paul Allaire
Keyword(s):  
Wind Tunnel ◽  
Power Output ◽  
Vertical Axis ◽  
Chord Length ◽  
Small Scale ◽  
Physical Parameters ◽  
Wind Tunnel Testing ◽  
Wind Speeds ◽  
The Given ◽  
Tunnel Testing

Vertical axis wind turbines (VAWTs) have long been considered a viable source for alternative energy; however, limited published research has contributed to limited technological advancement in these machines. Slower advancements are due, in part, to their complex aerodynamic models which include wake effects, vortex shedding, and cyclical blade angles of attack and Reynolds numbers. VAWTs are believed to hold several advantages over their more popular and better studied horizontal axis counterparts, including a simpler design and better efficiencies in lower wind speeds. They may have a unique niche in standalone applications at moderate wind speeds such as on an island, a remote military installation, or an inland farm. Currently, no published design standards or criteria exist for optimizing the physical properties of these turbines to maximize power output. A 2.44 m tall VAWT prototype with variable physical parameters was constructed for wind tunnel testing. The purpose of the experiment was to maximize the turbine’s power output by optimizing its physical configuration within the given parameters. These parameters included rotor radius, blade chord length, and pitch offset angle. The prototype was designed as a scaled-down model of a potential future VAWT unit that may be used to sustain a small farm or 2–4 houses. The wind tunnel consisted of a 2.74 m by 1.52 m cross section and could produce maximum wind speeds of 3.56 m/s. The turbine prototype consisted of three sets of interchangeable blades featuring two airfoils of varying chord length. Spokes of varying length allowed for rotor radii of 190.5, 317.5, and 444.5 mm. The pitch offset of the blades was varied from 0°–20° with a focus on the 10°–16° range as preliminary results suggested that this was the optimal range for this turbine. Ramp-up and steady-state rotational speeds were recorded as the blades were interchanged and the turbine radius was varied. A disk brake provided braking torque so that power coefficients could be estimated. This study successfully optimized the turbine’s power output within the given set of test parameters. The importance of finding an appropriate aspect ratio and pitch offset angle are clearly demonstrated in the results. A systematic approach to small scale wind tunnel testing prior to implementation is presented in this paper.

Scavenging Wind Energy From Fluttering Membranes With Piezoelectric Materials

2012 ◽  
Author(s):  
Edwar Romero ◽  
Visvanatha Sundararajan ◽  
Nellie Bonilla ◽  
Christian Martinez ◽  
Amilcar Rincon
Keyword(s):  
Wind Energy ◽  
Piezoelectric Material ◽  
Large Scale ◽  
Piezoelectric Materials ◽  
Energy Generation ◽  
Small Scale ◽  
Wind Speeds ◽  
Wind Energy Generation ◽  
Aeroelastic Flutter ◽  
Working Principle

Although wind power is a highly researched area for large scale energy production, there are also opportunities for small scale applications. The present investigation proposes a fluttering membrane with flexible piezoelectric material for wind energy generation. The working principle of this approach is based on aeroelastic flutter using a MFC piezoelectric material for energy harvesting. It has been observed that the addition of flaps at the trailing edge has the advantage to decrease the critical speed at which fluttering occurs. This allows energy generation at lower wind speeds. The addition of the flaps decreased the fluttering speed from 14.8mph to 7mph. An average voltage output as high as 232mV was obtained, while a power output of 65.5μW was found at 17.5mph.

Aerodynamic Design and Optimization of a Small Scale Wind Turbine

2014 ◽  
Author(s):  
G. Kröger ◽  
U. Siller ◽  
J. Dabrowski
Keyword(s):  
Wind Turbine ◽  
Power Output ◽  
Rotor Blade ◽  
Residential Buildings ◽  
Speed Ratio ◽  
Small Scale ◽  
Substantial Part ◽  
Optimized Design ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds

Small scale wind turbines can meet a substantial part of the electricity demand of residential buildings and facilities in isolated areas. It is a curious fact, however, that for many of these systems the actual power output has been dramatically overestimated. This can be partially explained by the very high rated wind speeds at which the design power output applies. The current work depicts the pathway to an aerodynamically optimized design of a small scale horizontal axis wind turbine in the 1kW class, optimized for wind speeds between 3.5 m/s and 5.5 m/s, a typical range of the energetic average of urban wind speeds. The aerodynamic stability of the blade has been a particular focus leading to a nearly constant efficiency over a range of wind speeds. The rotating speed of the system is adjusted to the optimal tip speed ratio at wind speeds up to maximum power via active control of the aerodynamic torque of the rotor blades. This is realized by adapting the generator torque to the current wind speed guaranteeing optimal efficiency and power output. The rotor blade optimization has been conducted unconventionally, in a turbomachinery-inspired 3D-blade design optimization campaign, using high-fidelity compressible CFD. This approach is described in detail, focussing on geometry parametrization and the numerical model with reasonable boundary conditions. Finally, the aerodynamic performance of the rotor blade is assessed at different wind speeds and pitching angles.

Forecasting of Tornadoes and Downbursts

2020 ◽  
Author(s):  
Djordje Romanic
Keyword(s):  
Chaos Theory ◽  
Prediction Models ◽  
Weather Prediction ◽  
Small Scale ◽  
Weather Forecasts ◽  
Wind Speeds ◽  
The Past ◽  
Extreme Wind ◽  
Extreme Wind Speeds ◽  
Numerical Weather Prediction Models

Tornadoes and downbursts cause extreme wind speeds that often present a threat to human safety, structures, and the environment. While the accuracy of weather forecasts has increased manifold over the past several decades, the current numerical weather prediction models are still not capable of explicitly resolving tornadoes and small-scale downbursts in their operational applications. This chapter describes some of the physical (e.g., tornadogenesis and downburst formation), mathematical (e.g., chaos theory), and computational (e.g., grid resolution) challenges that meteorologists currently face in tornado and downburst forecasting.

scholarly journals Canard optimization for enhancing the performance of small horizontal axis wind turbine at low wind speeds

2020 ◽  
Vol 37 ◽  
pp. 63-71
Author(s):  
Yui-Chuin Shiah ◽  
Chia Hsiang Chang ◽  
Yu-Jen Chen ◽  
Ankam Vinod Kumar Reddy
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Peak Performance ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Optimum Parameters ◽  
Low Wind Speeds

ABSTRACT Generally, the environmental wind speeds in urban areas are relatively low due to clustered buildings. At low wind speeds, an aerodynamic stall occurs near the blade roots of a horizontal axis wind turbine (HAWT), leading to decay of the power coefficient. The research targets to design canards with optimal parameters for a small-scale HAWT system operated at variable rotational speeds. The design was to enhance the performance by delaying the aerodynamic stall near blade roots of the HAWT to be operated at low wind speeds. For the optimal design of canards, flow fields of the sample blades with and without canards were both simulated and compared with the experimental data. With the verification of our simulations, Taguchi analyses were performed to seek the optimum parameters of canards. This study revealed that the peak performance of the optimized canard system operated at 540 rpm might be improved by ∼35%.

Geometric and Material Optimization of Vortex-Induced Vibration Micro Energy Harvesters for Localized Wind Environments

2012 ◽  
Author(s):  
Jesse J. French ◽  
Colton T. Sheets
Keyword(s):  
Energy Harvesting ◽  
Power Output ◽  
Fluid Velocity ◽  
Frequency Variation ◽  
Vortex Induced Vibration ◽  
Energy Harvesters ◽  
Wind Speeds ◽  
Material Optimization ◽  
Piezoelectric Energy ◽  
Wind Velocities

Wind energy capture in today’s environment is often focused on producing large amounts of power through massive turbines operating at high wind speeds. The device presented by the authors performs on the extreme opposite scale of these large wind turbines. Utilizing vortex induced vibration combined with developed and demonstrated piezoelectric energy harvesting techniques, the device produces power consistent with peer technologies in the rapidly growing field of micro-energy harvesting. Vortex-induced vibrations in the Karman vortex street are the catalyst for energy production of the device. To optimize power output, resonant frequency of the harvester is matched to vortex shedding frequency at a given wind speed, producing a lock-on effect that results in the greatest amplitude of oscillation. The frequency of oscillation is varied by altering the effective spring constant of the device, thereby allowing for “tuning” of the device to specific wind environments. While localized wind conditions are never able to be predicted with absolute certainty, patterns can be established through thorough data collection. Sampling of local wind conditions led to the design and testing of harvesters operating within a range of wind velocities between approximately 4 mph and 25 mph. For the extremities of this range, devices were constructed with resonant frequencies of approximately 17 and 163 Hz. Frequency variation was achieved through altering the material composition and geometry of the energy harvester. Experimentation was performed on harvesters to determine power output at optimized fluid velocity, as well as above and below. Analysis was also conducted on shedding characteristics of the device over the tested range of wind velocities. Computational modeling of the device is performed and compared to experimentally produced data.

Development of Rotary Engine Based Micro-DG/CHP System

2016 ◽  
Author(s):  
Richard L. Hack ◽  
Max R. Venaas ◽  
Vince G. McDonell ◽  
Tod M. Kaneko
Keyword(s):  
Distributed Generation ◽  
Power Output ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Pollutant Emissions ◽  
Small Scale ◽  
Rotary Engine ◽  
Chp System ◽  
Performance Results

Small scale Distributed Generation with waste heat recovery (<50 kW power output, micro-DG/CHP) is an expanding market supporting the widespread deployment of on-site generation to much larger numbers of facilities. The benefits of increased overall thermal efficiency, reduced pollutant emissions, and grid/microgrid support provided by DG/CHP can be maximized with greater quantities of smaller systems that better match the electric and thermal on-site loads. The 3-year CEC funded program to develop a natural gas fueled automotive based rotary engine for micro-DG/CHP, capitalizing upon the unique attributes engine configuration will be presented including initial performance results and plans for the balance of the program.

2D and 2.5D Numerical Simulations for Vortex-Induced Vibration (VIV) of a 1.5:1 Rectangular Cylinder

2021 ◽  
Author(s):  
Bowen Yan ◽  
Yangjin Yuan ◽  
Dalong Li ◽  
Ke Li ◽  
Qingshan Yang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Numerical Simulations ◽  
Phase Difference ◽  
Vortex Shedding ◽  
Lift Force ◽  
Small Scale ◽  
Aerodynamic Damping ◽  
Displacement Response ◽  
Wind Speeds ◽  
Rectangular Cylinder

The semi-periodic vortex-shedding phenomenon caused by flow separation at the windward corners of a rectangular cylinder would result in significant vortex-induced vibrations (VIVs). Based on the aeroelastic experiment of a rectangular cylinder with side ratio of 1.5:1, 2-dimensional (2D) and 2.5-dimensional (2.5D) numerical simulations of the VIV of a rectangular cylinder were comprehensively validated. The mechanism of VIV of the rectangular cylinder was in detail discussed in terms of vortex-induced forces, aeroelastic response, work analysis, aerodynamic damping ratio and flow visualization. The outcomes showed that the numerical results of aeroelastic displacement in the cross-wind direction and the vortex-shedding procedure around the rectangular cylinder were in general consistence with the experimental results by 2.5D numerical simulation. In both simulations, the phase difference between the lift and displacement response increased with the reduced wind speed and the vortex-induced resonance (VIR) disappeared at the phase difference of approximately 180∘. The work done by lift force shows a close relationship with vibration amplitudes at different reduced wind speeds. In 2.5D simulations, the lift force of the rectangular cylinder under different wind speeds would be affected by the presence of small-scale vortices in the turbulence flow field. Similarly, the phase difference between lift force and displacement response was not a constant with the same upstream wind speed. Aerodynamic damping identified from the VIV was mainly dependent on the reduced wind speed and negative damping ratios were revealed at the lock-in regime, which also greatly influenced the probability density function (PDF) of wind-induced displacement.

On turbulent separation in the flow past a bluff body

1992 ◽  
Vol 241 ◽  
pp. 443-467 ◽  
Author(s):  
A. Neish ◽  
F. T. Smith
Keyword(s):  
Large Scale ◽  
Bluff Body ◽  
Separated Flow ◽  
Small Scale ◽  
Supporting Evidence ◽  
Turbulent Regime ◽  
Trailing Edge ◽  
Flow Past ◽  
Starting Point ◽  
Turbulence Factor

The basic model problem of separation as predicted by the time-mean boundary-layer equations is studied, with the Cebeci-Smith model for turbulent stresses. The changes between laminar and turbulent flow are investigated by means of a turbulence ‘factor’ which increases from zero for laminar flow to unity for the fully turbulent regime. With an attached-flow starting point, a small increase in the turbulence factor above zero is found to drive the separation singularity towards the trailing edge or rear stagnation point for flow past a circular cylinder, according to both computations and analysis. A separated-flow starting point is found to produce analogous behaviour for the separation point. These findings lead to the suggestion that large-scale separation need not occur at all in the fully turbulent regime at sufficiently high Reynolds number; instead, separation is of small scale, confined near the trailing edge. Comments on the generality of this suggestion are presented, along with some supporting evidence from other computations. Further, the small scale involved theoretically has values which seem reasonable in practical terms.

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