Solar Hydrogen Project Group Update 21 st July 2009.

Solar Hydrogen Project

Group Update

21st July 2009

CC-124 growth kinetics model Bojan Tamburic

Error caused by O2 bubble evolutionData outliers ‘brushed’

Fit Logistic (Sigmoid) curve of the form:

)tr(t 0e1

KOD(t)

)tr(t 0e1

1H(t)

H(t)KOD(t)Let

‘Guess’ initial r and t0 rangeMinimise the total least squared error of r and t0

Fix r and t0 valuesUse linear optimisation to recover K

K)OD(,twhene1

KOD(t) )tr(t 0

So K is the maximum attainable OD

t0 and r tell us something about the growth rate – but not easy to visualiseBiologists typically use doubling time – not really appropriate for logistic curve

Gradient at t0 – maximum growth rate

Regression coefficient = 0.98

Plan:1. Fit logistic curves to existing growth kinetics data2. Obtain new data to investigate the effects of light intensity, agitation

and CO2 sparging on growth kinetics, but:• Sartorius reactor under modification• Algae appear to be contaminated• Need about 2 months of data collection to obtain ‘good’ results

Solar Hydrogen Project: SD

• Fe2O3 work:

– First stage of comparative study of different types of Fe2O3:

• Old EPFL CVD – Voltammetry– Impedance – Transient photocurrent measurements

Solar Hydrogen Project: SD

• Photocurrent transients:

– Measured with 0.1M NaOH, solution = water or 80:20 water/MeOH

– Set potential to 0.6 V, V = -0.1V– Chopped at ~3 Hz, recorded photocurrent

transients at 10-5 s resolution

Fe2O3 (EPFL): NaOH-H2O

-1.0E-05

0.0E+00

1.0E-05

2.0E-05

3.0E-05

4.0E-05

5.0E-05

-0.5 -0.25 0 0.25 0.5 0.75 1

Potential vs qre / Volts

cd /

Acm

-2

Dark 450 nm

Fe2O3 (EPFL): NaOH-H2O/MeOH

-1.0E-05

0.0E+00

1.0E-05

2.0E-05

3.0E-05

4.0E-05

5.0E-05

-0.50 -0.25 0.00 0.25 0.50 0.75 1.00

Potential vs qre/ Volt

cd /

Acm

-2

Dark 450 nm

Fe2O3 (EPFL): 0.6V

-5.00E-06

0.00E+00

5.00E-06

1.00E-05

1.50E-05

2.00E-05

2.50E-05

4.8 4.9 5 5.1 5.2 5.3 5.4 5.5

t / s

cd

/ A

cm

-2

Water Water/MeOH

Fe2O3 (EPFL): 0.1V

-8.0E-06

-6.0E-06

-4.0E-06

-2.0E-06

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

4.8 4.9 5 5.1 5.2 5.3 5.4 5.5

t / s

cd

/ A

cm

-2

Water Water-MeOH

Fe2O3: EPFL

-1.0E-05

0.0E+00

1.0E-05

2.0E-05

3.0E-05

4.0E-05

5.0E-05

-0.5 -0.25 0 0.25 0.5 0.75 1

Potential vs qre / Volt

cd /

Acm

-2

Water-MeOH

Water-1.500E-05

-1.000E-05

-5.000E-06

0.000E+00

5.000E-06

1.000E-05

1.500E-05

2.000E-05

4.8 4.9 5 5.1 5.2 5.3 5.4 5.5

t / s

cd /

Acm

-2

Water Water/MeOH

-1.00E-05

-8.00E-06

-6.00E-06

-4.00E-06

-2.00E-06

0.00E+00

2.00E-06

4.00E-06

6.00E-06

8.00E-06

1.00E-05

4.8 4.9 5 5.1 5.2 5.3 5.4 5.5

t / s

cd /

Acm

-2

Water Water-MeOH

-1.500E-05

-1.000E-05

-5.000E-06

0.000E+00

5.000E-06

1.000E-05

1.500E-05

2.000E-05

4.8 4.9 5 5.1 5.2 5.3 5.4 5.5

t / s

cd /

Acm

-2

Water Water/MeOH

Conclusions

• Preliminary (and not concluded yet)

– In the absence of MeOH see cathodic “dark” current, even at 0.6 V.

– As applied potential is increased, the photocurrent becomes increasingly transient

– As applied potential is increased the cathodic “dark” current increases (relative to the photocurrent)

Photo-electrochemical Reactor Modeling:

Week 3 Update

Zachary Ulissi

Reactor Design: Original & Wedges

Reactor Design: Extra Post

Reactor Design: Small Wedge

Reactor Design: Extra Post

Mass Transfer In the Laminar Regime

(300 ml/min liquid flow)

Goal: 2 A/m2

Mass Transfer Limit for Laminar Flow

Goal: 2 A/m2

Mass Transfer Limit for Laminar Flow

Goal: 2 A/m2

Insufficient Mixing!

Laminar Diffusion Completed