Heat to Hydrogen by Reverse Electrodialysis—Using a Non-Equilibrium Thermodynamics Model to Evaluate Hydrogen Production Concepts Utilising Waste Heat

Simon B. B. Solberg, Pauline Zimmermann, Øivind Wilhelmsen, Jacob J. Lamb, Robert Bock and Odne S. Burheim ()
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Simon B. B. Solberg: Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
Pauline Zimmermann: Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
Øivind Wilhelmsen: Department of Chemistry, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
Jacob J. Lamb: Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway
Robert Bock: Federal Institute for Materials Research and Testing (BAM), 12205 Berlin, Germany
Odne S. Burheim: Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim, Norway

Energies, 2022, vol. 15, issue 16, 1-22

Abstract: The reverse electrodialysis heat engine (REDHE) is a promising salinity gradient energy technology, capable of producing hydrogen with an input of waste heat at temperatures below 100 °C. A salinity gradient drives water electrolysis in the reverse electrodialysis (RED) cell, and spent solutions are regenerated using waste heat in a precipitation or evaporation unit. This work presents a non-equilibrium thermodynamics model for the RED cell, and the hydrogen production is investigated for KCl/water solutions. The results show that the evaporation concept requires 40 times less waste heat and produces three times more hydrogen than the precipitation concept. With commercial evaporation technology, a system efficiency of 2% is obtained, with a hydrogen production rate of 0.38 g H 2 m − 2 h − 1 and a waste heat requirement of 1.7 kWh g H 2 − 1 . The water transference coefficient and the salt diffusion coefficient are identified as membrane properties with a large negative impact on hydrogen production and system efficiency. Each unit of the water transference coefficient in the range t w = [ 0 – 10 ] causes a −7 mV decrease in unit cell electric potential, and a −0.3% decrease in system efficiency. Increasing the membrane salt diffusion coefficient from 10 − 12 to 10 − 11 leads to the system efficiency decreasing from 2% to 0.6%.

Keywords: ion-exchange membranes; reverse electrodialysis heat engine; hydrogen; non-equilibrium thermodynamics (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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