Implementation of an alkali metal seeder for plasma temperature

Implementation of an alkali metal seeder for
plasma temperature control
D.C.M. van den Bekerom, N. den Harder, M.C.M. van de Sanden, G.J. van Rooij, FOM Institute DIFFER – Dutch
Institute for Fundamental Energy Research, Association EURATOM-FOM, PO Box 1207,343 BE Nieuwegein, the
Netherlands, www.differ.nl
Solar Fuels
The plasma-chemical reactor
The importance of energy storage:
Trade-off in conversion and energy efficiency:
Release energy
Demand
100
Microwave
Rotational excitation
90
Vibrational excitation
supersonic:
Radiofrequency (RF)
80
CCP:
ICP:
70
DIFFER & IPF
60
High CO2 flow (75 slm):
Low CO2 flow (11 slm):
50
40
30
Electron energy loss (%)
Store energy
100
Energy efficiency 
Supply
75
(100)
50
Other
modes
(001)
25
20
(010)
10
0
-1
0
0
0.1
1
1
10
10
10
Specific energy input (eV/molecule)
Time -›
Electronic excitation
CO2 neutral
energy cycle!
10
E/no
(10-16
Vcm2)
Controlling the reaction pathway
8
CO2 + 283 kJ/mol -› CO + ½O2
Two dissociation pathways:
• Electronic excitation (
Adding alkali-metals
CO(1S+) + O(1D)
6
CO(1S+) + O(3P)
)
The rates of the different pathways are
determined by the electron temperature.
• Charge is carried by
alkali ions
3B
2
)
• Gradual vibrational excitation (
• Alkali atoms have a
low ionization energy
1B
2
1S+
HEAT
For solar fuel synthesis, we start with
dissociating CO2:
U, eV
4
2
0
0.05
FELIX
v’’=0
0.1
0.15
0.2
rO-CO, nm
Implementation of the design
Particle balance:
I(t)
Recombination
Flow
Sheath
Where:
Ionization
Pin = input power
Γprod = particle production
Γloss = particle loss
Power balance:
ne = electron density
kB = Boltzmann’s constant
Te = electron temperature
Input
Ion losses
Vibrational
levels
Az = reactor base area
Ar = reactor lateral surface
V = reactor volume
kDR = Dissociative
recombination rate
k0 = rate factor
kvib = vibrational rate
kion = ionization rate
Future experiment
Free Electron
Laser
Uvib = vibrational energy
Uion = ionization energy
cs = sound speed
vth = thermal velocity
vflow = flow velocity
Thomson
Scattering
Laser Induced
Fluorescence

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