performance and economic outlook of a membraneless alkaline electrolyser mi gillespie demcotech...
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PERFORMANCE AND ECONOMIC OUTLOOK OF A MEMBRANELESS ALKALINE ELECTROLYSER
MI Gillespie
DemcoTECH Engineering, Modderfontein, Johannesburg, 1645 South Africa
[email protected]+27 11 608 4355
F van der Merwe & RJ Kriek
Electrochemistry for Energy & Environment Group, Research Focus Area: Chemical Resource Beneficiation, North-West University, Private Bag X6001, Potchefstroom, 2520 South Africa
Technology Principle
Technology Reference:- M.I. Gillespie, F. van der Merwe, RJ Kriek, Performance evaluation of a membraneless divergent electrode-flow-through (DEFT) alkaline electrolyser based on optimisation of electrolytic flow and electrode gap, Journal of Power Sources (2015) 293, 228 - 235
• DEFT TM “Divergent-Electrode-Flow-Through”.
• A liquid alkaline technology utilising the flow of solution through porous electrodes to create a
mechanism for gas separation
Flow is the only necessary requirement for high purity gas separation
(H2 purity ~99.83% @ 3500mA.cm-2 and 2.5mm Electrode Gap)
Technology Comparison – Capabilities
• Broad comparison of membrane separation and membraneless separation
Membraneless Technologies (DEFTTM)Capabilities:
1. High current density capability (±3500mA.cm-2 increased alkaline technology threshold limit)
2. Compact stack volume
3. High purity separation
4. Inexpensive stack materials
5. Low operating costs (replace electrodes only)
6. Compatible with renewable energy sources (flow is only requirement)
Membrane TechnologiesCapabilities:
1. High current density capabilities (±2000mA.cm-2)
2. Compact stack volume
3. Ultra high purity separation
4. Efficient performance
Technology Comparison – Challenges
Membraneless Technologies (DEFTTM)
Challenges:
1. Improvement in pump parasitic load (CFD Optimisation)
2. Improvement in operating cell potential (Catalyst Research Focus)
3. Rapid knock-out of product micro-bubbles (Solution Found)
4. Raising operating temperatures and pressures (Commercial Pilot Plant Focus
Membrane TechnologiesChallenges:
1. Expensive technology
2. Membrane longevity and stability
3. Reduction in PGM materials and stack cost
4. High back diffusion of gas (specifically at high current densities)
• Broad comparison of membrane separation and membraneless separation
Concept Demonstration
• Test-rig constructed for the purpose of demonstrating proof of concept and initial
optimisation of technology
• In operation since 2013
Specification Unit Value
Volumetric Flow Output NL/hr 63.6
Number of Electrode Pairs # 6
Electrode Diameter mm 30 porous circular
Electrode Gap Range mm 0.5-5.5
Variable Flow Velocity Range m.s-1 0.03-1
Variable Temperature Range °C 40-80
Experimental Results
• Relationship of Electrode Gap, Current Density and Flow Velocity:
-1000
0
1000
2000
3000
4000
1
2
3
4
5
2.02.5
3.03.5
0.075 m.s-1 Flow Velocity
0.1 m.s-1 Flow Velocity
0.15 m.s-1 Flow Velocity
0.2 m.s-1 Flow Velocity
Reference:- M.I. Gillespie, F. van der Merwe, RJ Kriek, Performance evaluation of a membraneless divergent electrode-flow-through (DEFT) alkaline electrolyser based on optimisation of electrolytic flow and electrode gap, Journal of Power Sources (2015) 293, 228 - 235
Electrode Gap
AS:
CONSEQUENCE:
Cell Potential Current Density
but
Flow velocity
or
Experimental Results
• A comparison of tested catalytic combinations
Reference:- M.I. Gillespie, F. van der Merwe, RJ Kriek, Performance evaluation of a membraneless divergent electrode-flow-through (DEFT) alkaline electrolyser based in optimisation of electrolytic flow and electrode gap, Journal of Power Sources (2015) 293, 228 - 235
Cell Potential (VDC)
1.5 2.0 2.5 3.0 3.5 4.0
Cur
rent
De
nsity
(m
A.c
m-2
)
0
500
1000
1500
2000
2500
3000
HH
V %
Eff
icie
ncy
30
40
50
60
70
80
90
RuO2/IrO2/TiO2 Anode, Pt Cathode @ 2.5 mm Electrode Gap, 70°C, 30 wt% KOH, 0.075m.s-1
Ni 200 Anode, Ni 200 Cathode @ 2.5 mm Electrode Gap, 70°C, 30 wt% KOH, 0.075m.s-1
SS 316 Anode, SS316 Cathode @ 2.5 mm Electrode Gap, 70°C, 30 wt% KOH, 0.075m.s-1
Theoretical HHV % Stack EfficiencyActual HHV % Stack Efficiency
219.99
474.40
977.09
1552.64
2270.14
2746.54
71.96% @ 2 VDC
75.05% @ 2 VDC
Cell Potential (VDC)
1.6 1.8 2.0 2.2 2.4 2.6
Cur
rent
De
nsity
(m
A.c
m-2
)
0
200
400
600
800
1000
HH
V %
Eff
icie
ncy
55
60
65
70
75
80
85
90
219.99
474.40
977.09
672.19
Lower potential range detail
Performance Comparison
• Current performance data in comparison to existing technologies
Stable
performance
demonstrated at
20 000 mA.cm-2
Reference:- M.I. Gillespie, F. van der Merwe, RJ Kriek, Performance evaluation of a membraneless divergent electrode-flow-through (DEFT) alkaline electrolyser based in optimisation of electrolytic flow and electrode gap, Journal of Power Sources (2015) 293, 228 - 235
Technology Scalability
• Scalability easily achieved by means of the conventional filter press design assembled into stack modules.
Commercial Scale Electrolysis Stack:
1. Electrode Cross Sectional Area:- 633 cm2
2. Design Current Density:- 3 500 mA.cm-2
3. Hydrogen Mass Flow Rate:- 2 kg H2/ 24 hrs
4. Hydrogen Volumetric Flow Rate:- 24 183.8 NL/ 24 hrs
5. Electrolytic Volumetric Flow Rate Required:- 5 L/s
6. Pressure Drop (Simulated & Confirmed):- ~3.62 kPaç
Commercial Feasibility
• Construction of a “commercial output” pilot plant to determine the membraneless technologies operation in conjunction with:
1. Fully automated operation at pressure (10 Bar)
2. DynaSwirl® Vortex Gas-liquid separation system
3. New non-noble catalysts for improved efficiencies
4. Gas purities at low flow velocities (±0.03 m.s-1) as initially simulated with CFD
software and demonstrated experimentally
5. Higher reactive area and flow friendly porous electrodes
6. High operational potential at enhanced pressures and temperatures
Pilot Plant Specifications
• Comparison of current specifications and near term future targets
PARAMETER UNIT CURRENT SPECIFICATION TARGET SPECIFICATION
Operating Current Density mA.cm-2 3500 ±3500
Operating Cell Potential VDC 3.0 - 3.5 2.0 - 2.5
Volumetric Flow Requirement L.s-1 52.5 (DEFTTM CONCEPT)
0.017 (IMPROVED CONCEPT)
Current Pump Parasitic Load
(72% pumping efficiency)
% of Total Power @ HHV
%13% @ 35 HHV%
16% @ 58.9 HHV% (DEFTTM CONCEPT)
8.7% @ 70.7 HHV% (IMPROVED
CONCEPT)
Electrolytic Fluid System
CapacityL ± 77.06
± 40 (DEFTTM CONCEPT)
± 10 (IMPROVED CONCEPT)
Current and Future Costs
• Comparison of current costs and near term future estimates
• NREL (2009) H2 cost for a 2009 state-of-the-art forecourt system cost: $4.90A. to $5.70A. / kg H2 ($3.32A. /kg H2
electrolysis production cost)
• NREL (2004) H2 cost for a small neighbourhood system (~20 kg H2/day): $19.01B. / kg H2
• Cost (CAPEX+OPEX) estimates for a membraneless plant capable of producing 2 kg H2/day operating for a 10
year life of plant running on a renewable source of energy:
Operational Cost Inclusions:
1. Frequent Electrode Replacement
2. De-ionised water production
3. Electrolyte solute annual replacement
4. Consumables for pump maintenance
5. Gas Conditioning Maintenance
Reference:
A. Independent Review Panel, Current (2009) State-of-the-art hydrogen production cost estimate using water electrolysis, National Renewable Energy Laboratory, 2009,INREL/BK-6A 1-46676
B. J. Ivy, Summary of Electrolytic Hydrogen Production, Milestone completion report, National Renewable Energy Laboratory, 2004, NREL/MP-560-36734
1 Inclusion of CAPEX, OPEX and R&D Additional Costs
2 Inclusion of CAPEX and OPEX costs calculated on a mass production scale and
method
PARAMETER UNIT CURRENT PLANT COST FUTURE PLANT COST
Cost per H2 US $ / kg H2 11.071.< 6.622.(DEFTTM CONCEPT)
< 5.362. (IMPROVED CONCEPT)
System Capital Cost Comparison
• Comparison of capital costs of similar production output electrolysis systems
available on the market
1. Capital costs only, with cost per mass unit hydrogen calculated by amount of hydrogen generated in a 10 year life of plant
TECHNOLOGY SUPPLIER
TECHNOLOGY TYPE
HYDROGEN OUTPUT
(kg H2/day)HHV%
EFFICIENCYCAPITAL COST1.(US $/kg H2)
Current Commercially
Available Neighbourhood
Generators
(3 Quotations)
PEM / Advanced
AWE2.1 - 2.4
38.7 - 48.19.79 - 11.05
DEFT Membraneless
and Future ConceptMembraneless 2
35 (CURRENT
DEFTTM)
58.9 (DEFTTM
TARGET)
70.7 (IMPROVED
CONCEPT
TARGET)
9.55 (CURRENT CAPEX)
5.101. (DEFTTM FUTURE CAPEX)
3.271. (IMPROVED CONCEPT
CAPEX)
Project Outcomes
• Target goals for research and development
1. Successful demonstration of technology in a “commercial scale” application (In Progress)
2. Unlimited potential for technology to be investigated for use in alternate industries involved
in purification and for the electrolysis of salt water at a wide range of elevated temperatures
and pressures using renewable energy
3. Improved concept development (Future work)
4. Global partnership with a corporation for the commercialisation of affordable and simple
yet effective hydrogen generators for low cost hydrogen production
For updates on our commercial development
and research
please visit www.hydroxholdings.co.za
Thank you