Brisse, Annabelle

Hauch, Anne

Schiller, Günter

Vogt, Ulrich

Zahid, Mohsine

English

Institute of Transport Research:Publications

 17th World Hydrogen Energy Conference, Brisbane, Australia 15 – 19 June 2008 HIGHLY EFFICIENT, HIGH TEMPERATURE, HYDROGEN PRODUCTION BY WATER ELECTROLYSIS (HI2H2) A. Brisse1, A. Hauch2, G. Schiller3, U. Vogt4 & M. Zahid1 1EIfER  Emmy-Noether-Strasse 11, D-76131 Karlsruhe (Germany) annabelle.brisse@eifer.org   2Risø-DTU, Frederiksborgvej 3999, DK-4000 Roskilde (Denmark),  3DLR, Pfaffenwaldring 38-40, D-70569 Stuttgart (Germany), 4EMPA, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland),  EXTENDED ABSTRACT The wide variety of energy sources, including renewables, which can be used to produce hydrogen, makes the hydrogen more and more attractive as an energy vector. A way to transform renewable and other non-fossil sources of energy into hydrogen is water electrolysis. The specific targeted research project “Highly Efficient, High Temperature, Hydrogen Production by Water Electrolysis” (Hi2H2) was launched in 2004 in the frame of the European Framework Program 6. The aim of the project was to demonstrate the feasibility of hydrogen production by high temperature water electrolysis using currently available Solid Oxide Fuel Cells (SOFC) technology. Coupled to renewable energy sources, this technology may meet the present environmental and economical request. The Hi2H2 project is a consortium of four European research laboratories - EIFER (coordinator) and DLR in Germany, Risø-DTU in Denmark, and EMPA in Switzerland, bringing together skills and experience in the field of material science, electrochemistry, and renewable energy.  In order to determine the best operating conditions of the Solid Oxide Electrolyser Cells (SOEC) under High Temperature Electrolysis (HTE) mode, several experiments have been realized at different scales, from the cells and single repeated units (SRU) to the stack. Results obtained were then used to make the technical and economical analysis of the hydrogen production by high temperature water electrolysis.         A. Brisse, A. Hauch, G. Schiller, U. Vogt & M. Zahid  17th World Hydrogen Energy Conference, Brisbane, Australia 15 – 19 June 2008 Introduction The uniqueness of the concept is to perform water electrolysis at a rather high temperature, between 700 and 900°C. High temperature electrolysis of steam (HTE) is expected to consume less electrical energy as compared to electrolysis at low temperature as consequence of the more favourable thermodynamic and electrochemical kinetic conditions for the reaction (Dutta, 1990). Thermodynamic conditions are more favourable in the sense that the molar Gibbs energy of the reaction (ΔG) drops from ~1.23 eV (237 kJ.mol-1) at ambient temperature to ~0.95 eV at 900°C (183 kJ.mol-1), while the molar enthalpy of the reaction (ΔH) remains essentially unchanged (ΔH ~1.3 eV or 249 kJ.mol-1 at 900°C) (Larminie & Dicks, 2003). A significant part of the energy required for an ideal (loss free) HTE can thus be provided by heat.  Experimental Two types of planar SOFC designs with up to 100 cm2 active area were considered: an electrode (ceramic-metal compound) supported and a porous metal substrate supported Solid Oxide Electrolyser Cell (SOEC), based on advanced ceramic materials and stainless steels. Low cost industrial manufacturing techniques (like screen printing and tape casting) are applied with commercial, high volume, stainless steels to produce the ceramic component. Performances of these SOECs were measured as a function of both the operating temperature and the percentage of humidity of the inlet gas. As expected the performance of the cell increases with increasing the operating temperature but also with increasing the humidification level. Very high performances were achieved using electrode supported SOEC’s made at Risø - DTU. So far, no SOEC’s have been reported to have better initial performance at similar operating conditions. A record-breaking performance was reached at 950°C, where steam electrolysis was operated at a current density of -3.6 A.cm-2 and a cell voltage of only 1.48 V (Jensen et al, 2007) (Fig. 1). These current densities were obtained at very high electrical efficiencies which would correspond to a production rate of hydrogen of 1.34 kg.m-².h-1.  00.20.40.60.811.21.41.6-4 -3 -2 -1 0 1 2 3i [A/cm2]Cell voltage [V]850°C50 vol.% H2O/50 vol.% H2950°C70 vol.% H2O/30 vol.% H21.49V at -3.59 A.cm-2Fuel cell modeElectrolyser mode Fig. 1: Kinetics of a Risoe solid oxide cell as an electrolyser cell and as a fuel cell at different temperatures and steam partial pressures in the inlet gas to the cell (Jensen et al, 2007). A. Brisse, A. Hauch, G. Schiller, U. Vogt & M. Zahid  17th World Hydrogen Energy Conference, Brisbane, Australia 15 – 19 June 2008 Durability tests of up to 2500 hours were performed with single cells. The tests demonstrated that a maximum degradation of 2%/1000h occurs at current densities between 0 and -0.5 A/cm2, temperatures between 800 and 950°C, and a steam percentage of up to 70 vol.%.  Cells were then assembled by stacking single repeated units (SRU). The SRU’s are composed of a SOEC and metal alloy interconnect plates to ensure electrical contact and gas distribution between cells. Protective coatings of the interconnects were developed and validated during the project to face the corrosive operating conditions (high temperature and oxidizing atmosphere). Durability tests of SRU’s demonstrated that detrimental corrosion of the interconnect can be hindered using protective coatings. However, in-situ impedance spectroscopy measurements revealed that the electrical conductivity of these coatings has to be further improved. The passivation/activation phenomenon observed by Risø-DTU on the cells was clearly attributed to a silica deposition at the interface between the electrolyte and the hydrogen electrode, originating from the glass seal. A new sealing pre-treatment procedure was developed to avoid the initial passivation/activation process (Hauch et al, 2007). The last development consisted of the assembly of two electrolyser stacks of 250 and 600 cm2 active areas. The first stack (of 250 cm2 active areas) was tested for more than 3500h at 800°C and -0.3 A/cm² leading to an average degradation rate during the first 2000 h of about 14 %/1000h (Fig. 2). After 2000 hours, the steam content was increased, leading to an improvement of the stack performance. Thereby, the degradation rate was reduced to 6 %/1000h.  0 1000 2000 3000 40000,51,01,545678Voltage, VTime, h cell1V cell2V cell3V cell4V cell5V overallV Fig. 2: Stack and cells voltage evolution during the test. Gas conditions before 2000 h are 1 Nl/min H2 + 0.5 Nl/min N2 at the hydrogen electrode side, 7.5 Nl/min at the oxygen electrode side, and 50 vol.% of steam. After 2000 h, nitrogen flow was stopped and the steam constant was increased to 70 vol.%. Based on the achieved results, a techno-economical analysis was made to predict the hydrogen production cost. A cost of around 2 €/kg was calculated assuming an average electricity price of 0.05 €/kWh and an endothermal operation mode using a water 50 vol.% Steam 70 vol.% Steam A. Brisse, A. Hauch, G. Schiller, U. Vogt & M. Zahid  17th World Hydrogen Energy Conference, Brisbane, Australia 15 – 19 June 2008 vapour source at 200°C. This study also revealed that an increase in the temperature of the water source would not decrease the hydrogen cost significantly because the main factor influencing the hydrogen production cost is the electricity price. Conclusions The excellent results obtained within the project have demonstrated that hydrogen can be produced through water electrolysis with extremely high efficiencies, greater than 90%. As a comparison, typical low temperature electrolysers have an average efficiency of about 60-70 %. The consequence is a possible strong lowering of the production cost of hydrogen. The high efficiency also ensures that energy is not wasted in the process. References Dutta S., (1990), “Technology assessment of advanced electrolytic hydrogen production”, International Journal of Hydrogen Energy, 15, pp. 379-386. Hauch A., S.H. Jensen S.H., Bilde-Sorensen J.B., and Mogensen M., (2007), “Silica Segregation in the Ni/YSZ Electrode”, Journal of the Electrochemical Society, 154, pp. A619-A626.  Jensen S.H., Larsen P.H., and Mogensen M., (2007), “Hydrogen and synthetic fuel production from renewable energy sources”, International Journal of Hydrogen Energy, 32, in press. Larminie J., and Dicks A., (2003), “Fuel Cell Systems Explained”, 2nd Ed. John Wiley & Sons, p 371.  Web site: http://www.hi2h2.com Project coordinator name: Mohsine ZAHID (EIfER) Partners     Germany Denmark Switzerland Germany  BRIEF BIOGRAPHY OF PRESENTER Mrs Brisse has a background in materials science & electrochemistry, especially for high-temperature systems. Her field of expertise concerns ceramics elaboration and characterization for Solid Oxide Fuel Cells. Her PhD work, realised at the Atomic Energy Commission in France, was awarded in 2007 as the best PhD work in the field of ceramics materials by the French Society for Ceramics. Since one and a half year, Mrs Brisse is responsible of the high temperature electrolysis activity at the European Institute for Energy Research in Germany.  

Hydrogen and synthetic fuel production from renewable energy sources”,

Technology assessment of advanced electrolytic hydrogen production”,

Highly Efficient High Temperature Hydrogen Production by Water Electrolysis (HI2H2)

HIGHLY EFFICIENT, HIGH TEMPERATURE, HYDROGEN PRODUCTION BY WATER ELECTROLYSIS (HI2H2) M. Zahid1, A. Brisse1, A. Hauch2, G. Schiller3& U. Vogt4 1European Institute For Energy Research (EIFER)  Emmy-Noether-Strasse 11, D-76131 Karlsruhe (Germany) zahid@eifer.uni-karlsruhe.de    2Risø laboratory, Technical University of Denmark (Risø DTU), Frederiksborgvej 399, DK-4000 Roskilde (Denmark),  3Deutsches Zentrum für Luft- und Raumfahrt (DLR), Pfaffenwaldring 38-40, D-70569 Stuttgart (Germany), 4Eidgenössische Materialprüfungs- und Forschungsanstalt (EMPA), Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland),  EXTENDED ABSTRACT The variety of energy sources which can be used to produce hydrogen makes hydrogen more and more attractive as an energy vector. A way to transform renewable and other non-fossil sources of energy into hydrogen is water electrolysis. The specific targeted research project “Highly Efficient, High Temperature, Hydrogen Production by Water Electrolysis” (Hi2H2) was launched in 2004 in the frame of the European Framework Program 6. The aim of the project was to demonstrate the feasibility of hydrogen production by high temperature water electrolysis using currently available Solid Oxide Fuel Cells (SOFC) technology. Coupled to renewable energy sources, this technology may meet the present environmental and economical requests. The Hi2H2 project is a consortium of four European research laboratories - EIFER (coordinator) and DLR in Germany, Risø DTU in Denmark, and EMPA in Switzerland, bringing together skills and experience in the field of material science, electrochemistry, and renewable energy.  In order to determine the best operating conditions of the Solid Oxide Electrolyser Cells (SOEC) in the High Temperature Electrolysis (HTE) mode, a number of experiments have been realized at different scales, from cells and single repeating units (SRU) to stack. Results obtained were then used to make the technical and economical analysis of the hydrogen production by high temperature water electrolysis.       M. Zahid, A. Brisse, A. Hauch, G. Schiller & U. Vogt  Introduction The uniqueness of the concept is to perform water electrolysis at a high temperature, between 700 and 900°C. High temperature electrolysis of steam (HTE) is expected to consume less electrical energy as compared to electrolysis at low temperature as consequence of the more favourable thermodynamic and electrochemical kinetic conditions for the reaction (Dutta, 1990).  Experimental Two types of planar SOFC designs with up to 100 cm2 active area were considered: an electrode (ceramic-metal compound) supported and a porous metal substrate supported Solid Oxide Electrolyser Cell (SOEC). Low cost industrial manufacturing techniques (like screen printing and tape casting) are applied to produce the advanced ceramic materials Performances of these SOECs were measured as a function of the operating temperature and the percentage of humidity of the inlet gas. As expected, the performance of the cell becomes better with increasing the operating temperature and the humidification level. High performances when achieved using electrode supported SOEC’s made at Risø  DTU. So far, no SOECs have been reported to have better initial performance at similar operating conditions. A record-breaking performance was reached at 950°C, where steam electrolysis was operated at a current density of -3.6 A.cm-2 and a cell voltage of only 1.48 V (Jensen et al, 2007) (Fig. 1). These current densities were obtained at high electrical efficiencies which would correspond to a production rate of hydrogen of 1.34 kg.m-2.h-1.  00.20.40.60.811.21.41.6-4 -3 -2 -1 0 1 2 3i [A/cm2]Cell voltage [V]850°C50 vol.% H2O/50 vol.% H2950°C70 vol.% H2O/30 vol.% H21.49V at -3.59 A.cm-2Fuel cell modeElectrolyser mode Fig. 1: j-V curves on the Risø solid oxide cell as an electrolyser cell and as a fuel cell at different temperatures and steam partial pressures in the inlet gas to the cell (Jensen et al, 2007). Durability tests of up to 2500 hours were performed with single cells. Some tests demonstrated that a degradation below 2%/1000h can be achieved at current densities down to -0.5 A/cm2, temperatures between 800 and 950°C, and a steam percentage of up to 70 vol.%.  Cells were assembled with an interconnect plate to build a serial repeating unit (SRU). This SRU was sealed with a glass seal. Protective coatings of the interconnect plates were developed and validated during the project. In order to account to the corrosive operating conditions (high temperature and oxidizing atmosphere). Durability tests of SRUs demonstrated that corrosion of the interconnect plate can be slowed down by the M. Zahid, A. Brisse, A. Hauch, G. Schiller & U. Vogt  use of protective coatings. However, in-situ impedance spectroscopy measurements revealed that the electrical conductivity of these coatings has to be further improved. An increase in the cell voltage was observed by Risø DTU during the first hundred hours of the durability test when a glass seal was used in the SRU. Thereafter the cell voltage decreased. The passivation/activation phenomenon was unambiguously attributed to a silica deposition, coming from the glass seal, at the interface between the electrolyte and the hydrogen electrode (Hauch et al, 2007). A sealing pre-treatment was developed to avoid the initial passivation/activation process (Hauch et al, 2008). The latest development consisted in the assembly of two electrolyser stacks of 250 and 600 cm2 active areas. The first stack (250 cm2 active area) was tested for more than 3500h at 800°C and -0.3 A/cm². The average degradation rate during the first 2000 h was about 14 %/1000h (Fig. 2). After 2000 hours, the steam content was increased, which improve the stack performance, and leaded to a lower degradation rate of 6 %/1000h.  0 1000 2000 3000 40000,51,01,545678Voltage, VTime, h cell1V cell2V cell3V cell4V cell5V overallV Fig. 2: Stack and cell voltage evolution during the test. Gas conditions before 2000 h are 1 Nl/min H2 + 0.5 Nl/min N2 at the hydrogen electrode side, 7.5 Nl/min at the oxygen electrode side, and 50 vol.% of steam. After 2000 h, the N2 flow was stopped and the steam content was increased to 70 vol.%. Based on the achieved results, a techno-economical analysis was made to predict the hydrogen production cost. A cost of around 2 €/kg was calculated assuming an average electricity price of 0.05 €/kWh, a cell operating voltage below the value of thermoneutral potential (1.3 V at 800°C) and a water vapour source at 200°C. The study also revealed that an increase in the temperature of the water source would not decrease the hydrogen cost significantly because the main factor influencing the hydrogen production cost is the electricity price. Conclusions Results obtained within the project have demonstrated that hydrogen can be produced through water electrolysis with higher efficiencies, greater than 90%. SOFC can be operated in the electrolysis mode with low operation voltages in the range of 1 to 1.3V. Cells are thus suitable for reversible operation. The estimated hydrogen production cost 50 vol.% Steam 70 vol.% Steam M. Zahid, A. Brisse, A. Hauch, G. Schiller & U. Vogt  indicates that the SOEC technology has the potential to be competitive with the other low temperature hydrogen production processes.  Acknowledgement We acknowledge the European Commission for supporting the project.  References Dutta S., (1990), “Technology assessment of advanced electrolytic hydrogen production”, International Journal of Hydrogen Energy, 15, pp. 379-386. Hauch A., S.H. Jensen S.H., Bilde-Sorensen J.B., and Mogensen M., (2007), “Silica Segregation in the Ni/YSZ Electrode”, Journal of the Electrochemical Society, 154, pp. A619-A626.  Hauch A., Ebbesen S., Jensen S.H., and Mogensen M., (2008), “Solid Oxide Electrolysis Cells – Microstructure and Degradation of the Ni/YSZ Electrode”, Journal of the Electrochemical Society, submitted.  Jensen S.H., Larsen P.H., and Mogensen M., (2007), “Hydrogen and synthetic fuel production from renewable energy sources”, International Journal of Hydrogen Energy, 32, in press. Larminie J., and Dicks A., (2003), “Fuel Cell Systems Explained”, 2nd Ed. John Wiley & Sons, p 371.  Web site: http://www.hi2h2.com Project coordinator name: Mohsine ZAHID (EIfER) Partners        

Fuel Cell Systems Explained”, 2nd Ed.

Highly Efficient High Temperature Hydrogen Production by Water Electrolysis (Hi2H2)

Highly Efficient High Temperature Hydrogen Production by Water Electrolysis (HI2H2)

Abstract

Similar works

Full text

Available Versions

Institute of Transport Research:Publications

Institute of Transport Research:Publications