Review of pyroelectric thermal energy harvesting and new MEMs-based resonant energy conversion techniques (original) (raw)
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Development of MEMS based pyroelectric thermal energy harvesters
Proceedings of …, 2011
The efficient conversion of waste thermal energy into electrical energy is of considerable interest due to the huge sources of low-grade thermal energy available in technologically advanced societies. Our group at the Oak Ridge National Laboratory (ORNL) is developing a new type of high efficiency thermal waste heat energy converter that can be used to actively cool electronic devices, concentrated photovoltaic solar cells, computers and large waste heat producing systems, while generating electricity that can be used to power remote monitoring sensor systems, or recycled to provide electrical power. The energy harvester is a temperature cycled pyroelectric thermal-to-electrical energy harvester that can be used to generate electrical energy from thermal waste streams with temperature gradients of only a few degrees. The approach uses a resonantly driven pyroelectric capacitive bimorph cantilever structure that potentially has energy conversion efficiencies several times those of any previously demonstrated pyroelectric or thermoelectric thermal energy harvesters. The goals of this effort are to demonstrate the feasibility of fabricating high conversion efficiency MEMS based pyroelectric energy converters that can be fabricated into scalable arrays using well known microscale fabrication techniques and materials. These fabrication efforts are supported by detailed modeling studies of the pyroelectric energy converter structures to demonstrate the energy conversion efficiencies and electrical energy generation capabilities of these energy converters. This paper reports on the modeling, fabrication and testing of test structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermalto-electrical energy harvesters.
Development of MEMS based pyroelectric thermal energy harvesters
Energy Harvesting and Storage: Materials, Devices, and Applications II, 2011
The efficient conversion of waste thermal energy into electrical energy is of considerable interest due to the huge sources of low-grade thermal energy available in technologically advanced societies. Our group at the Oak Ridge National Laboratory (ORNL) is developing a new type of high efficiency thermal waste heat energy converter that can be used to actively cool electronic devices, concentrated photovoltaic solar cells, computers and large waste heat producing systems, while generating electricity that can be used to power remote monitoring sensor systems, or recycled to provide electrical power. The energy harvester is a temperature cycled pyroelectric thermal-to-electrical energy harvester that can be used to generate electrical energy from thermal waste streams with temperature gradients of only a few degrees. The approach uses a resonantly driven pyroelectric capacitive bimorph cantilever structure that potentially has energy conversion efficiencies several times those of any previously demonstrated pyroelectric or thermoelectric thermal energy harvesters. The goals of this effort are to demonstrate the feasibility of fabricating high conversion efficiency MEMS based pyroelectric energy converters that can be fabricated into scalable arrays using well known microscale fabrication techniques and materials. These fabrication efforts are supported by detailed modeling studies of the pyroelectric energy converter structures to demonstrate the energy conversion efficiencies and electrical energy generation capabilities of these energy converters. This paper reports on the modeling, fabrication and testing of test structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermalto-electrical energy harvesters.
Pyroelectric energy conversion: Optimization principles
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000
In the framework of microgenerators, we present in this paper the key points for energy harvesting from temperature using ferroelectric materials. Thermoelectric devices profit from temperature spatial gradients, whereas ferroelectric materials require temporal fluctuation of temperature, thus leading to different applications targets. Ferroelectric materials may harvest perfectly the available thermal energy whatever the materials properties (limited by Carnot conversion efficiency) whereas thermoelectric material's efficiency is limited by materials properties (ZT figure of merit). However, it is shown that the necessary electric fields for Carnot cycles are far beyond the breakdown limit of bulk ferroelectric materials. Thin films may be an excellent solution for rising up to ultra-high electric fields and outstanding efficiency.
Thermal Energy Harvesting Using Pyroelectric and Piezoelectric Effect
Journal of Physics: Conference Series, 2016
This paper presents a prototype of a thermal energy harvesting mechanism using both pyroelectric and piezoelectric effect. Thermal energy is one of abundant energy sources from various processes. Waste heat from a chip on a circuit board of the electronic device involves temperature differences from a few degrees C to over 100 • C. Therefore, 95 • C of a heat reservoir was used in this study. A repetitive time-dependant temperature variation is applied by a linear sliding table. The influence of heat conditions was investigated, by changing velocity and frequency of this linear sliding table. This energy harvesting mechanism employs Lead Zirconate Titanate (PZT-5H), a bimetal beam and two neodymium magnets. The pyroelectric effect is caused by a time-dependent temperature variation, and the piezoelectric effect is caused by stress from deformation of the bimetal. A maximum power output 0.54 μW is obtained at an optimal condition when the load resistance is 610 kΩ.
Pyroelectric energy converter for harvesting waste heat: Simulations versus experiments
International Journal of Heat and Mass Transfer, 2012
This paper is concerned with numerical simulations of a pyroelectric converter for direct energy conversion of waste heat into electricity. The simulated prototypical device consisted of a hot and cold source separated by a series of vertical microchannels supporting pyroelectric thin films made of co-polymer P(VDF-TrFE) and undergoing the Olsen cycle. A piston was used to vertically oscillate a working fluid back and forth between the thermal sources. The experimental device was instrumented with thermocouples and a pressure sensor. The two-dimensional transient mass, momentum, and energy equations were solved numerically using finite element methods to determine the local and time-dependent temperature at various locations inside the device microchannels. The operating frequency varied from 0.025 to 0.123 Hz and the working fluid was 1.5 or 50 cSt silicone oil. Good agreement was found between the simulated and experimentally measured local mean temperatures for both working fluids at all operating frequencies considered. The local temperature swings were underestimated slightly for 50 cSt silicone oil and significantly more for 1.5 cSt silicone oil. Overall, this study confirms our previous numerical results. Moreover, this numerical model could be used to design and operate the next generation of pyroelectric energy converters based on oscillatory convective heat transfer.
Pyroelectric materials and devices for energy harvesting applications
Energy Environ. Sci., 2014
This review covers energy harvesting technologies associated with pyroelectric materials and systems. Such materials have the potential to generate electrical power from thermal fluctuations and is a less well explored form of thermal energy harvesting than thermoelectric systems. The pyroelectric effect and potential thermal and electric field cycles for energy harvesting are explored. Materials of interest are discussed and pyroelectric architectures and systems that can be employed to improve device performance, such as frequency and power level, are described. In addition to the solid materials employed, the appropriate pyroelectric harvesting circuits to condition and store the electrical power are discussed.
Large harvested energy with non-linear pyroelectric modules
Nature
Coming up with sustainable sources of electricity is one of the grand challenges of this century. The research field of materials for energy harvesting stems from this motivation, including thermoelectrics1, photovoltaics2 and thermophotovoltaics3. Pyroelectric materials, converting temperature periodic variations in electricity, have been considered as sensors4 and energy harvesters5–7, although we lack materials and devices able to harvest in the joule range. Here we develop a macroscopic thermal energy harvester made of 42 g of lead scandium tantalate in the form of multilayer capacitors that produces 11.2 J of electricity per thermodynamic cycle. Each pyroelectric module can generate up to 4.43 J cm−3 of electric energy density per cycle. We also show that two of these modules weighing 0.3 g are sufficient to sustainably supply an autonomous energy harvester embedding microcontrollers and temperature sensors. Finally, we show that for a 10 K temperature span these multilayer cap...
Cyclic energy harvesting from pyroelectric materials
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2011
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/cm 3 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/cm 3 obtained from standard PZT.
Simulations of a prototypical device using pyroelectric materials for harvesting waste heat
International Journal of Heat and Mass Transfer, 2008
This paper is concerned with directly converting waste heat into electricity using pyroelectric materials. A prototypical pyroelectric converter is simulated by solving the two-dimensional mass, momentum, and energy equations using finite element methods. The pumping power and the electrical power generated are estimated from the computed pressure, temperature, and velocity. The results show that the energy efficiency increases as the density and specific heat of the working fluid and of the pyroelectric material decrease. Moreover, the power density increases as the density and specific heat of the working fluid increase and those of the pyroelectric material decrease. One can reasonably achieve an energy efficiency of 40% of the Carnot efficiency and a power density of 24 W/L of pyroelectric materials.
Journal of Physics D: Applied Physics, 2020
Low efficiency is the main drawback of many MEMS thermal energy harvesters. Recently, energy harvesting micro-devices that operate using the pyroelectric effect gained attention due to their potential superior performance. Operation of these devices is based on the cyclic motion of a pyroelectric capacitor that operates between a high temperature and a low temperature reservoirs. In this paper, we investigate the dynamics of oscillations of a pyroelectric capacitor self sustained by thermally actuated bimetal micro-cantilevers, a topic which is so far underinvestigated. In addition to highlighting key thermodynamic aspects of the operation, we explore conditions for self-sustained oscillations and discuss the viability of operation at the mechanical resonance frequency. The analysis is presented for a new design inspired by the device proposed in Refs.[1, 2], where in contrast, our proposed design boasts the following features: The pyroelectric capacitor remains parallel to the heat reservoirs, by virtue of its symmetric support by two bimetallic cantilever beams; In addition, the cyclic operation of the device does not require physical contact, thus lowering the risk of mechanical failure; To adjust the damping force imparted by the surrounding gas, the thermal reservoirs are equipped with trenches. To study the dynamic operation of the device, we developed a physically based reduced order, yet accurate, model that accounts for the heat transfer between and within the different components, and for the various forces including the gas damping force. The model is embedded within an optimization algorithm to produce optimal designs over the range 26 − 38 • C of temperature difference between the two reservoirs. The corresponding range of harvested power density is 0.4-0.65 mW /cm 2 .