A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. In traditional pyroelectric energy harvesting methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions. Although the energy harvested during each period of the heating cycle is small, the accumulated total energy over time may exceed traditional methods. Three materials are studied: a commonly available soft lead zirconate titanate (PZT), a pre-stressed PZT composite, and single-crystal PMN-30PT. Radiation heating and natural cooling are used such that, at smaller cyclic frequencies, the temporal rate of change in temperature is large enough to produce high power densities. The maximum power density of 8.64 μW/cm3 is generated with a PMN-30PT single crystal at an angular velocity of 0.64 rad/s with a rate of 8.5°C/s. The pre-stressed PZT composite generated a power density of 6.31 μW/cm(3), which is 40% larger than the density of 4.48 μW/cm3 obtained from standard PZT.

Effects of dimensional cavity parameters, height, and orifice diameter, on synthetic jet peak velocities are investigated numerically and experimentally, utilizing two piezoelectric composite diaphragms, Bimorph and Thunder Õ . The system is modeled using a RNG -" model with a mesh generated using a tri-pave unstructured scheme and the diaphragms are modeled as moving boundaries. The model compares within 15% for a Bimorph but underpredicts the results for Thunder Õ by more than 30%. For a Bimorph, both cavity parameters are relevant with the orifice diameter having a higher effect. For Thunder Õ however, only orifice diameter is found to be statistically significant.

Piezoelectric composites with a characteristic initial curvature and accompanying residual stresses are capable of enhanced performance, relative to flat actuators. This paper utilizes Rayleigh-Ritz techniques with revisions regarding the effective in-plane resultant force and the effective bending moment. The Rayleigh-Ritz technique is based on the assumption that the stable geometric configuration developed in the actuator after manufacturing is the configuration that minimizes the total potential energy. This energy is a function of the displacement field which can be approximated by either a four-term model or a 23-term model. In this case, Thunder ® , a composite of steel, polyimide adhesive, PZT, and aluminum is constructed with varying geometries so that three-dimensional surface topology maps are measured. Numerically, the four-coefficient model produces results that are not comparable to experimental data. The 23-coefficient model generally shows good agreement with the data for all studied actuators. In the case of actuators with a length to width ratio of one, simulations are close to experimental results. In the case of length to width ratios different to unity, the model accurately predicts the devices' shape. It is further demonstrated that the curvature of the devices seems to follow the rolling direction of the stainless steel layer, challenging the isotropy assumption.

This paper considers energy harvesting using pyroelectric materials such as PZT-5A and thin-films. A simple model is used to predict the power generated based on the measured temperature of the material as a function of time. The measured and predicted results are presented and compared. In particular, the measured peak power density for a PZT-5A sample was 0.23 μWcm−2 for a maximum temperature rate of approximately 15 °Cs−1. The predicted peak power density under the same boundary conditions for thin-film lead scandium tantalate was over 125 μWcm−2. The power density is shown to be highly dependent upon the surface area and the pyroelectric coefficient, underlining the importance of maximizing these parameters.

No abstract