Solar Hydrogen Update

24th November 2009

Updates

-Carver’s reactor- Reactor fitting- Mirrors- Improvements on model

- Reactor models discussion- Mechanistic studies- Kinetic data

- Feasibility of annular configuration

H2 O2

Reactor

Carver’s ReactorReactor setup

PumpPump

FeedTank

Issues• Extra pumps• Extra inventory

H2 O2

Reactor

Carver’s ReactorReactor setup

Pump

FeedTank

Issues• Limited feed tank opening

H2 O2

Reactor

Carver’s ReactorReactor setup

Pump

FeedTank

Issues• Rate of gases separate from liquid• Might need a hydrocyclone for gas-liquid separation

MirrorFrom Optical Mechanics Inc. Quotation is yet to receive

Mirror

Reaction Kinetics

H2O H2 ½ O2+

Semiconductor hν+ Semiconductor (e-, h+)

2H+ H2+ 2e-

+ 2h+H2O ½ O2+2H+

k1

k2

k3

How fast is the hydrogen generation ?• This rate might overcome the low efficiency performance• Mechanistic study get help from chemistry ?• Study on the reaction rate can be obtained from the current reactor• This would improve the reactor model

Annular ConfigurationSpoken to Prof. James R Taylor (Imperial College Physics Dept.)

• Energy loss ~10 db/km• Could Si or quartz as fibre material• It is feasible and worth investigating in future

Annular Configuration

Fibre optic coated with photo-anode at the outer surface

Hollow fibre membrane

Cathode

Lens in focusing the light

Focusing task

• Setting up carver’s reactor for preliminary testing

• Should we get new burette?

• Improve on the current reactor model

• Run the plasma deposition unit for photo-anode

characterisation

Light Intensity - Spectra:

PBR1 – Low intensity LED array PBR2 – High intensity LED array

Sartorius reactor – Cool white fluorescent lightsCulture reactor – Cool white fluorescent lights

Light Intensity – Spectral matches:

CC-124 absorption to LED emissionCC-124 absorption to fluorescent emission

Pumps – Watson Marlow:

Peristaltic 300 series - £1222.00

Peristaltic 500 series - £603.00

Flow up to 2l/minMicroprocessor or manual controlBrushless DC motor2 year warranty5.6kg, 233x230x132mm

Flow up to 4.5l/minFixed speed pumpAC motor gearbox2 year warranty11kg, 360x170x140mm

Pumps – KNF Neuberger:

Liquid Diaphragm Pump, NF30 series - £114.06*

Gas Diaphragm Pump, modified NMP830 - £182.73*

General:•Oscillating displacement pump•DC motor•Mounted in any position•Oil/maintenance free•Weight ≈ 500g

Flow:•Around 0.3l/min for liquid pump•Around 2l/min for gas pump•Flow rate adjusted by changing input voltage – 4 lead DCB (brushless) motor for optimum control

Modification:•NMP830 gas-tight•Aluminium head•EPDM diaphragm and valves•G1/8 threaded port (Swagelok connection)•Designed for He pumping

Pumps – KNF Neuberger:

Modified Liquid Diaphragm Pump, NMP015 series

Solar simulator (Fessehaye) reactor:•NMP015 may be modified to be gas-tight (expensive)•Stainless steel/aluminium head•EPDM diaphragm and valves•“Low algal death rates”

MSc/PhD Students:

Stephanie Hoarau (SEF):•Develop MIMS system•Develop filtration systemAnnalisa (University of Milan)

FZ

• Design – flat panel bioreactor

• Update on instrumentation and data analysis

Flat Panel design:• gravitational flow• Cleaning• Probes• Support

Assembling the system:

•16-Bit, 250 kS/s M Series, Integrated BNC, External Power

•16 differential BNC analog inputs (16-bit, 250 kS/s)

•4 BNC analog ouputs (16-bit, 833 kS/s), 48 digital I/O (32 clocked, 8 BNC), and 32-bit counters

•NI Signal Streaming for sustained high-speed data streams over USB; OEM version available

•Compatible with LabVIEW, ANSI C/C++, C#, Visual Basic .NET and Visual Basic 6.0

•NI-DAQmx driver software and NI LabVIEW SignalExpress LE interactive data-logging software

NI USB-6229 BNC

Fe2O3: spray pyrolysis

• Effect of Sn doping on:

– Electrochemical properties

– Morphological properties

Undoped Fe2O3: 10 layers

Current-voltage characteristics of Undoped Fe2O3 films under light and dark conditions

-0.5

0

0.5

1

1.5

2

2.5

3

-0.4 -0.2 0 0.2 0.4 0.6 0.8

Applied Potential (V)

Curr

ent D

ensi

ty (A

.m-2

)

Dark

Light

Cycles: 1Scan Rate: 0.01 V.s-1

Step Potential: 0.01 V

Layers: 10C.A. Pressure: 50 psi

Undoped Fe2O3: 20 layers

Current-voltage characteristics of Undoped Fe2O3 films under light and dark conditions

-0.5

0

0.5

1

1.5

2

2.5

-0.4 -0.2 0 0.2 0.4 0.6 0.8

Applied Potential (V)

Curr

ent D

ensi

ty (A

.m-2

)

Dark

Light

Cycles: 1Scan Rate: 0.01 V.s-1

Step Potential: 0.01 V

Layers: 20C.A. Pressure: 50 psi

Doped Fe2O3: 10 layers

Current-voltage characteristics of Sn doped Fe2O3 films under light and dark conditions

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

-0.4 -0.2 0 0.2 0.4 0.6 0.8

Applied Potential (V)

Curr

ent D

ensi

ty (A

.m-2

) Dark

Light

Cycles: 1Scan Rate: 0.01 V.s-1

Step Potential: 0.01 V

Layers: 10C.A. Pressure: 50 psi

Doped Fe2O3: 20 layers

Current-voltage characteristics of Sn doped Fe2O3 films under light and dark conditions

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

-0.4 -0.2 0 0.2 0.4 0.6 0.8

Applied Potential (V)

Curr

ent D

ensi

ty (A

.m-2

) Dark

Light

Cycles: 2Scan Rate: 0.01 V.s-1

Step Potential: 0.01 V

Layers: 20C.A. Pressure: 50 psi

Doped Fe2O3: 15 layers

Current-voltage characteristics of Sn doped Fe2O3 films under light and dark conditions

-0.1

0

0.1

0.2

0.3

0.4

0.5

-0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Applied Potential (V)

Curr

ent D

ensi

ty (A

.m-2

)

Light

Dark

Cycles: 1Scan Rate: 0.01 V.s-1

Step Potential: 0.01 V

Layers: 15C.A. Pressure: 50 psi

Undoped Fe2O3: 15 layers

Doped Fe2O3: 20 layers

On-going work

• Effect of Sn-doping– Lower/higher doping concentrations

• Film thickness measurements

• Quantum efficiency measurements – Effective H2 yields

CO2 Reduction Mechanism

• CO2 + e- CO2-

– CO2- + H+ + e- HCOO-

– CO2- + H2O + e- HCOO- + OH-

– CO2- + H+ + e- CO + OH-

– CO2- + H2O + e- CO + 2OH-

Low CO2 concentration in aqueous systems

Feed CO2 in gas phase through gas diffusion electrodes along with steam

PEC Reactor Development