Continuous electrochemical heat engines

Poletayev, Andrey D.; McKay, Ian Salmon; Chueh, William C.; Majumdar, Arun

doi:10.1039/c8ee01137k

Cited by 71 publications

(51 citation statements)

References 36 publications

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“…The η E of DTCC reaches 2.8% at 70 °C and 3.52% at 90 °C (Fig. 4a), which is among the highest efficiency of the existing direct energy conversion technologies in this temperature range 6,11–14,37–39 . Notably, the η E of the DTCC is catching up with that of the solid-state TE with a figure of merit value of 1 (ref.…”

Section: Resultsmentioning

confidence: 91%

“…4Device performance and demonstration. a Heat-to-electricity conversion efficiency ( η E ) versus temperature differential, and b ratio of η E to η Carnot versus volumetric power density for DTCCs and the best-reported TECs including TGCs (blue triangle) 6–9 , RFB-based TEC (violet diamond) 14 , TRABs (green square) 12,13 , and TRECs (orange circle) 10,11,37–39 . c Electrochromic smart window powered by the stacked DTCCs in hot water.…”

Section: Resultsmentioning

confidence: 99%

“…Yet, the introduction of ammonia stream is a serious concern regarding the leakage, stability, and safety. Recently, continuous electrochemical heat engine has also been conducted in the form of redox flow battery (RFB) with flowing electrolytes in redox reactions at different temperatures, which achieves an η E of 1.8% (15% of η Carnot ) 14 .…”

Section: Introductionmentioning

confidence: 99%

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Direct thermal charging cell for converting low-grade heat to electricity

et al. 2019

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Efficient low-grade heat recovery can help to reduce greenhouse gas emission as over 70% of primary energy input is wasted as heat, but current technologies to fulfill the heat-to-electricity conversion are still far from optimum. Here we report a direct thermal charging cell, using asymmetric electrodes of a graphene oxide/platinum nanoparticles cathode and a polyaniline anode in Fe2+/Fe3+ redox electrolyte via isothermal heating operation. When heated, the cell generates voltage via a temperature-induced pseudocapacitive effect of graphene oxide and a thermogalvanic effect of Fe2+/Fe3+, and then discharges continuously by oxidizing polyaniline and reducing Fe3+ under isothermal heating till Fe3+ depletion. The cell can be self-regenerated when cooled down. Direct thermal charging cells attain a temperature coefficient of 5.0 mV K−1 and heat-to-electricity conversion efficiency of 2.8% at 70 °C (21.4% of Carnot efficiency) and 3.52% at 90 °C (19.7% of Carnot efficiency), outperforming other thermoelectrochemical and thermoelectric systems.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Direct thermal charging cell for converting low-grade heat to electricity

et al. 2019

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“…TREC systems use different electrochemical cells whose electrode reactions have suitable temperature coefficients, [12,14,15] while TEC devices are usually made by symmetric electrodes and a redox couple in the electrolyte. [13,16,17] Recently, using two flow batteries [18] and a temperature gradient between them, a new TEC device has been reported, which has shown an unprece-dent efficiency of 1.86 % but low power density. TREC and TEC result less expensive, easily scalable [13] and exhibit higher energy efficiencies [12,14,19] compared to ORC and SST systems.…”

Section: Introductionmentioning

confidence: 99%

Thermally Regenerable Redox Flow Battery

et al. 2020

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The efficient production of energy from low-temperature heat sources (below 100°C) would open the doors to the exploitation of a huge amount of heat sources such as solar, geothermal, and industrial waste heat. Thermal regenerable redoxflow batteries (TRBs) are flow batteries that store energy in concentration cells that can be recharged by distillation at temperature < 100°C, exploiting low-temperature heat sources. Using a single membrane cell setup and a suitable redox couple (LiBr/Br 2), a TRB has been developed that is able to store a maximum volumetric energy of 25.5 Wh dm À 3 , which can be delivered at a power density of 8 W m À 2. After discharging 30 % of the volumetric energy, a total heat-to-electrical energy conversion efficiency of 4 % is calculated, the highest value reported so far in harvesting of low-temperature heat.

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“…In thermogalvanic systems, which are electrochemical analogues of solid-state thermoelectric devices, entropy changes inherent in redox reactions are used to couple a flow of ions to a flow of heat for energy harvesting purposes 10 . Recent advances in this concept include both thermally regenerative and continuous electrochemical heat engines, in which forced convection of redox-active fluids allows for decoupling of ionic and thermal transport lengths that may lead to higher efficiencies than are achievable by solid-state thermoelectrics 11,12 . In addition to leveraging the fundamental reaction entropy, thermo-electrochemical systems that leverage the interaction of electrochemical driving forces and other phase transitions have also been deployed successfully 13,14 .…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Redox Refrigeration

McKay

Kunz

Majumdar

2019

Sci Rep

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The high conformational entropy change of the Fe(CN)63−/4− redox reaction can be used as the basis for a compact electrochemical refrigerator. This device is comparable to a liquid version of a Peltier cooler, with two distinct advantages: (1) the entropy change per carrier (1.5 mV/K) of the electrochemical refrigerant is more than 5 times larger than that of state-of-the-art solid thermoelectric materials; and (2) the liquid electrolyte can be advected continuously away from the cooling junction, so that Joule heating in the bulk element does not diminish the delivered cooling effect. In this work, we use infrared microscopy to visualize the thermal aspects of Fe(CN)63−/4− redox, and compare the estimated cooling to calculated values with and without electrolyte flow. While the temperature differences achieved in a single cell are small (~50 mK) and not enhanced by electrolyte flow, the cooling power density (~0.5 W/cm3) is high when normalized to the small electrode volume. Non-dimensional figures of merit are proposed to identify electrochemical redox species for maximizing the cooling effect.

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Continuous electrochemical heat engines

Abstract: Direct electrochemical heat engines enable the use of novel redox-active fluids and optimization of both power and efficiency for broad-spectrum heat harvesting.

Cited by 71 publications

References 36 publications

Direct thermal charging cell for converting low-grade heat to electricity

Direct thermal charging cell for converting low-grade heat to electricity

Thermally Regenerable Redox Flow Battery

Electrochemical Redox Refrigeration

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