1. PERFORMANCE AND ECONOMIC OUTLOOK
MI Gillespie
DemcoTECH Engineering, Modderfontein, Johannesburg, 1645 South Africa
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
PERFORMANCE AND ECONOMIC OUTLOOK
OF A MEMBRANELESS ALKALINE ELECTROLYSER

2. Technology Principle 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 3500mA.cm-2 and 2.5mm Electrode Gap)
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,

3. Technology Comparison – Capabilities
Broad comparison of membrane separation and membraneless separation
Membraneless Technologies (DEFTTM)
Capabilities:
High current density capability (±3500mA.cm-2 increased alkaline technology threshold limit)
Compact stack volume
High purity separation
Inexpensive stack materials
Low operating costs (replace electrodes only)
Compatible with renewable energy sources (flow is only requirement)
Membrane Technologies
Capabilities:
High current density capabilities (±2000mA.cm-2)
Compact stack volume
Ultra high purity separation
Efficient performance

4. Technology Comparison – Challenges
Broad comparison of membrane separation and membraneless separation
Membraneless Technologies (DEFTTM)
Challenges:
Improvement in pump parasitic load (CFD Optimisation)
2. Improvement in operating cell potential (Catalyst Research Focus)
Rapid knock-out of product micro-bubbles (Solution Found)
Raising operating temperatures and pressures (Commercial Pilot Plant Focus
Membrane Technologies
Challenges:
Expensive technology
Membrane longevity and stability
Reduction in PGM materials and stack cost
High back diffusion of gas (specifically at high current densities)

5. 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
Variable Flow Velocity Range
m.s-1
0.03-1
Variable Temperature Range °C
40-80

6. Experimental Results
Relationship of Electrode Gap, Current Density and Flow Velocity:
AS:
Electrode Gap
CONSEQUENCE:
Cell Potential or
Current Density
but
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,

7. Lower potential range detail
Experimental Results
A comparison of tested catalytic combinations
Lower potential range detail
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,

8. Performance Comparison
Current performance data in comparison to existing technologies
Stable
performance
demonstrated at
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,

9. Technology Scalability
Scalability easily achieved by means of the conventional filter press design assembled into stack modules.
Commercial Scale Electrolysis Stack:
Electrode Cross Sectional Area:- 633 cm2
Design Current Density: mA.cm-2
Hydrogen Mass Flow Rate:- 2 kg H2/ 24 hrs
Hydrogen Volumetric Flow Rate: NL/ 24 hrs
Electrolytic Volumetric Flow Rate Required:- 5 L/s
Pressure Drop (Simulated & Confirmed):- ~3.62 kPaç

10. Commercial Feasibility
Construction of a “commercial output” pilot plant to determine the membraneless technologies operation in conjunction with:
Fully automated operation at pressure (10 Bar)
DynaSwirl® Vortex Gas-liquid separation system
New non-noble catalysts for improved efficiencies
Gas purities at low flow velocities (±0.03 m.s-1) as initially simulated with Ansys® CFD software and demonstrated experimentally
Higher reactive area and flow friendly porous electrodes
High operational potential at enhanced pressures and temperatures

11. 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
Volumetric Flow Requirement
L.s-1 5
2.5 (DEFTTM CONCEPT)
0.017 (IMPROVED CONCEPT)
Current Pump Parasitic Load
(72% pumping efficiency)
% of Total HHV%
35 HHV%
HHV% (DEFTTM CONCEPT)
HHV% (IMPROVED CONCEPT)
Electrolytic Fluid System Capacity L
± 77.06
± 40 (DEFTTM CONCEPT)
± 10 (IMPROVED CONCEPT)

12. 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:
PARAMETER
UNIT
CURRENT PLANT COST
FUTURE PLANT COST
Cost per H2
US $ / kg H2
< (DEFTTM CONCEPT)
< (IMPROVED CONCEPT)
Operational Cost Inclusions:
Frequent Electrode Replacement
De-ionised water production
Electrolyte solute annual replacement
Consumables for pump maintenance
Gas Conditioning Maintenance
Inclusion of CAPEX, OPEX and R&D Additional Costs
Inclusion of CAPEX and OPEX costs calculated on a mass production scale and method
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
B. J. Ivy, Summary of Electrolytic Hydrogen Production, Milestone completion report, National Renewable Energy Laboratory, 2004, NREL/MP

13. System Capital Cost Comparison
Comparison of capital costs of similar production output electrolysis systems available on the market
TECHNOLOGY SUPPLIER
TECHNOLOGY TYPE
HYDROGEN OUTPUT
(kg H2/day)
HHV% EFFICIENCY
CAPITAL COST1.(US $/kg H2)
Current Commercially Available Neighbourhood Generators
(3 Quotations)
PEM / Advanced AWE
DEFT Membraneless and Future Concept
Membraneless 2
35 (CURRENT DEFTTM)
58.9 (DEFTTM TARGET)
70.7 (IMPROVED CONCEPT TARGET)
9.55 (CURRENT CAPEX)
(DEFTTM FUTURE CAPEX)
(IMPROVED CONCEPT CAPEX)
1. Capital costs only, with cost per mass unit hydrogen calculated by amount of hydrogen generated in a 10 year life of plant

14. Project Outcomes Target goals for research and development
Successful demonstration of technology in a “commercial scale” application (In Progress)
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
Improved concept development (Future work)
Global partnership with a corporation for the commercialisation of affordable and simple yet effective hydrogen generators for low cost hydrogen production

15. on our commercial development
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