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The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3. Electric-field-driven enhancement of the pyroelectric response (as large as − 550 μC m−2 K−1) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert lowgrade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm−3, 526 W cm−3 and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting.
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Energy scavenging from ultra-low temperature gradients
Thermal energy harvesting from natural resources and waste heat is becoming critical due to ever-increasing environmental concerns. However, so far, available thermal energy harvesting technologies have only been able to generate electricity from large temperature gradients. Here, we report a fundamental breakthrough in low-grade thermal energy harvesting and demonstrate a device based on the thermomagnetic effect that uses ambient conditions as the heat sink and operates from a heat source at temperatures as low as 24 °C. This concept can convert temperature gradients as low as 2 °C into electricity while operating near room temperature. The device is found to exhibit a power density (power per unit volume of active material) of 105 μW cm −3 at a temperature difference of 2 °C, which increases to 465 μW cm −3 at a temperature difference of 10 °C. The power density increases by 2.5 times in the presence of wind with a speed of 2.0 m s −1 . This advancement in thermal energy harvesting technology will have a transformative effect on renewable energy generation and in reducing global warming.
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- Award ID(s):
- 1738689
- PAR ID:
- 10098924
- Date Published:
- Journal Name:
- Energy & Environmental Science
- Volume:
- 12
- Issue:
- 3
- ISSN:
- 1754-5692
- Page Range / eLocation ID:
- 1008 to 1018
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1039/c8ee03084g
