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Issue 1, 2015
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A thermally regenerative ammonia-based battery for efficient harvesting of low-grade thermal energy as electrical power

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Abstract

Thermal energy was shown to be efficiently converted into electrical power in a thermally regenerative ammonia-based battery (TRAB) using copper-based redox couples [Cu(NH3)42+/Cu and Cu(II)/Cu]. Ammonia addition to the anolyte (2 M ammonia in a copper-nitrate electrolyte) of a single TRAB cell produced a maximum power density of 115 ± 1 W m−2 (based on projected area of a single copper mesh electrode), with an energy density of 453 W h m−3 (normalized to the total electrolyte volume, under maximum power production conditions). Adding a second cell doubled both the voltage and maximum power. Increasing the anolyte ammonia concentration to 3 M further improved the maximum power density to 136 ± 3 W m−2. Volatilization of ammonia from the spent anolyte by heating (simulating distillation), and re-addition of this ammonia to the spent catholyte chamber with subsequent operation of this chamber as the anode (to regenerate copper on the other electrode), produced a maximum power density of 60 ± 3 W m−2, with an average discharge energy efficiency of ∼29% (electrical energy captured versus chemical energy in the starting solutions). Power was restored to 126 ± 5 W m−2 through acid addition to the regenerated catholyte to decrease pH and dissolve Cu(OH)2 precipitates, suggesting that an inexpensive acid or a waste acid could be used to improve performance. These results demonstrated that TRABs using ammonia-based electrolytes and inexpensive copper electrodes can provide a practical method for efficient conversion of low-grade thermal energy into electricity.

Graphical abstract: A thermally regenerative ammonia-based battery for efficient harvesting of low-grade thermal energy as electrical power

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Publication details

The article was received on 05 Sep 2014, accepted on 18 Nov 2014 and first published on 18 Nov 2014


Article type: Paper
DOI: 10.1039/C4EE02824D
Citation: Energy Environ. Sci., 2015,8, 343-349
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    A thermally regenerative ammonia-based battery for efficient harvesting of low-grade thermal energy as electrical power

    F. Zhang, J. Liu, W. Yang and B. E. Logan, Energy Environ. Sci., 2015, 8, 343
    DOI: 10.1039/C4EE02824D

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