PERFORMANCE AND ECONOMIC OUTLOOK OF A MEMBRANELESS ALKALINE ELECTROLYSER

MI Gillespie

DemcoTECH Engineering, Modderfontein, Johannesburg, 1645 South Africa

malcolm.gillespie@demcotech.com+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