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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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Low-Grade Heat Utilization Through Ultrasound-Enhanced Desorption of Activated Alumina/Water for Thermal Energy Storage
Abstract Sorption thermal energy storage (TES) seems to be an auspicious solution to overcome the issues of intermittent energy sources and utilization of low-grade heat. Ultrasound-assisted adsorption/desorption of water vapor on activated alumina is proposed as a means of low-grade heat utilization through TES. The effects of ultrasonic power on the storing stage (desorption of water vapor) were analyzed to optimize the desorption and overall efficiencies. To determine and justify the effectiveness of incorporating ultrasound from an energy-savings point of view, an approach of constant total (heat plus ultrasound) input power of 25 W was adopted. To measure the extent of the effectiveness of using ultrasound, ultrasonic-power-to-total power ratios of 0.2 and 0.4 were investigated and the results compared with those of no-ultrasound (heat only) at the same total power. The regeneration temperature and desorption rate were measured simultaneously to investigate the effects of ultrasonication on regeneration temperature and utilization of low-grade heat. The experimental results showed that using ultrasound facilitates the regeneration of activated alumina at both power ratios without increasing the total input power. With regard to regeneration temperature, incorporating ultrasound decreases the regeneration temperature hence justifying the utilization of low-grade heat for thermal energy purposes. In terms of overall energy recovery of the adsorption thermal storage process, a new metric is proposed to justify incorporating ultrasound and any other auxiliary energy along with low-grade heat.
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- Award ID(s):
- 1703670
- PAR ID:
- 10291377
- Date Published:
- Journal Name:
- ASME 2020 Power Conference collocated with the 2020 International Conference on Nuclear Engineering
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1115/POWER2020-16802
