DLR.de • Chart 1
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Hybrid sensible/thermochemical storage of solar energy in
cascades of redox-oxide-pair-based porous ceramics
Christos Agrafiotis, Andreas Becker, Lamark deOliveira,
Martin Roeb, Christian Sattler
Institute of Solar Research
DLR/ Deutsches Zentrum für Luft- und Raumfahrt/
German Aerospace Center
Linder Höhe, 51147 Köln, Germany
DLR.de • Chart 2
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Outline:
• Solar Energy Storage in air-operated
Solar (Tower) Thermal Power Plants
(STPPs)
• ThermoChemical Storage (TCS)
principles and redox oxide pairs
• Some new ideas on redox-oxidebased porous ceramics for TCS in
STPPs
• From laboratory to solar testing
• Conclusions, current and future work
DLR.de • Chart 3
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Air-operated CSP Plants (Solar Tower Jülich/STJ)
• HTF: Air at atmospheric pressure,
heated up to about 700ºC and then
powering a steam generator.
• Sensible heat storage : TES by
temperature increase (cp ∆T)
• Latent heat storage : TES by phase
transition (∆ hsl)
• Thermochemical storage : TES by
chemical reaction (∆ hR)
7m x 7m x 6m
S. Zunft, et al.:SolarPACES, (2009); (2010); JSEE (2011); Energy Procedia, (2014).
DLR.de • Chart 4
> 14 ECERS, Toledo, Spain > Agrafiotis, Becker, deOliveira, Roeb, Sattler > June 21-25, 2015
From TES with sensible heat to hybrid sensible-thermochemical
storage with redox oxides
MO2x+1→ MO + xO2
Increase the volumetric storage density
instead of the storage volume: “coat with/
make of” honeycombs with redox oxide
General Atomics: GA–C27137: THERMOCHEMICAL
HEAT STORAGE FOR CONCENTRATED SOLAR
POWER THERMOCHEMICAL SYSTEM REACTOR
DESIGN FOR THERMAL ENERGY STORAGE ;
Phase II Final Report, 2011
DLR.de • Chart 5
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
• A cascade of different redox oxide
materials can be combined with
various porous structures along as
well “across” the reactor/heat
exchanger.
HTF flow when discharging
Cascaded ThermoChemical Storage (CTCS)
F. Dinter, M. Geyer, R. Tamme, Springer-Verlag, Berlin, (1991); Michels and Pitz-Paal, Solar Energy, 81 829–837, 2007.
TCS reactor/heat exchanger with spatial variation of functional materials and porosity in three dimensions, (C. Agrafiotis and R. Pitz-Paal, Patent Application Filed 2013).
DLR.de • Chart 6
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Tests Scale Evolution (single-oxide or cascaded testing)
TGA
Lab-scale
furnace test rig
Solar receivers
DLR.de • Chart 7
> 14 ECERS, Toledo, Spain > Agrafiotis, Becker, deOliveira, Roeb, Sattler > June 21-25, 2015
TGA (DSC) rig: Cyclic reduction – oxidation protocol
weight change (vs. stoichiometric) = f(T)
101
Tplateau reduction
100
1200
t=1 hr
1000
800
98
Tredox = ? oC
t=1 hr
97
600
96
Tplateau oxidation
400
95
94
MexOy oxidized
Air
MexOy reduced
Ar
200
93
MexOy: Tplateau reduction > Tredox > Tplateau oxidation
0
92
0
100
200
300
400
500
600
700
800
900
Time (min)
Reaction
Tred (oC) Max.
wt.
loss ( %)
2BaO2 +ΔH→ 2BaO+O2
690
‐9.45
2Co3O4 +ΔH→6CoO +O2
870
‐6.64
6Mn2O3 +ΔH→4Mn3O4 +O2
950
‐3.38
1030
‐10.01
4CuO+ΔH→2Cu2O+O2
Temperature (oC)
Weight change (%)
99
DLR.de • Chart 8
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
TGA: Co3O4 /CoO
oo
oo
O -loaded30
Cordierite
foam
985-785 C,
C, 55 C/min;
long-term cycling
3 4
Co3OCo
powder,
cycles:
985-785
C/min
4
1000
101
101
800
101
100
1000
100
100
Weight
(%)
Weight change
change (%)
0
99
98
800
9798
9697
600
0
Temperature (ooC)
Weight change (%)
99
Temperature
( C)
Temperature
(oC)
• Co3O4 can operate in a quantitative,
cyclic and fully reversible reduction/
oxidation mode within 800-1000oC
(950oC).
• As powder, coated on honeycombs/
foams or shaped in foams.
1000
1200
102
102
102
-1000
95
96
94
400
95
93
6.69 %
-2000
9294
200
9193
Co3O4 made foams, cycles 1-30
Weight change (%)
Foam, 30
ppi,powder
No 1
Coating
Weight change
(%) Coated cordierite foam 3, loading 64% (overall);
Cycles 1-30:
Temperature
90
92
0
400500
800
1000 1200
1500
1600
Time (min)
Time (min)
(min)
Agrafiotis, Roeb, Schmücker, Sattler, Solar Energy, Parts I, II, III (2014), (2015).
Temperature
calculated per mass of loaded powder
0
2000
2000
2400 2500 2800
DLR.de • Chart 9
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
TGA: Mn2O3/Mn3O4
1200
101
Mn22O33, 10oC/min
T = 1000 oC
100
o
T = 1000 oC
1000
o
Weight change (%)
Trdxn
= 950
= 950
C C
99
800
T = 870 oC
Tox==780
780oCoC
Wt loss:
3.68 %
Wt loss:
3.70 %
98
600
Wt re-gain:
3.51 %
400
97
96
Tdwell oxidation:
200
900oC
750oC
720oC
o
690ooC
650oooC
C
650
Weight change (%)
Temperature
95
0
100
200
300
400
500
600
Time (min)
700
800
900
0
1000
Temperature (oC)
• Mn2O3: reduction fast, stoichiometric;
but large temperature “gap” between
reduction (950oC) - oxidation (780690oC) !!
• Very narrow temperature range (690750oC) within which Mn2O3 reoxidation is significant.
• Mn2O3 re-oxidation is slow and needs
extended dwell at the optimum
temperature (range) for completion.
• Can be also achieved with slow rates
and no dwell as shown below.
DLR.de • Chart 10
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
TGA: Other oxides
• CuO/Cu2O: reduction temperature
very close to m.p. of Cu2O (shrinkage
and sintering); could not work
reproducibly even for few (5 cycles).
• BaO2/BaO: BaO reacts with CO2
present in air to BaCO3
• Perovskites: loose/gain (little) weight
continuously with T (perhaps plus in a
cascade but ∆H also very low):
Reaction
2 Co3O4 + ΔH → 6 CoO + O2 6 Mn2O3 + ΔH → 4 Mn3O4 + O2 ΔH (kJ/mol)
Tred
(oC) Tox o
( C) 202.5
895 875 31.9
950
720
101
Wt loss:
1.35 %
100
1200
Wt re-gain:
0.6 %
98
800
97
o
96
Temperature ( C)
Weight change (%)
99
95
400
94
93
La SrFeO3
Weight change (%)
Temperature
92
0
100
200
300
Time (min)
400
500
0
600
• Favourable Ts for oxidation but entire
cascade needs T > 950oC during reduction
DLR.de • Chart 11
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Furnace test rig: “Visualization” of Hybrid Sensible-TCS
vs. Sensible-only storage effect
1200
1200
Coated vs. non-coated honeycombs
Co3O4-Coated honeycombs
Temperature (C°)
(C°)
Temperature
2
800
800
Total Co3O4 coated mass = 98 g
O2 concentration
50
50
40
40
5000 sccm
2500 sccm
Difference between Sensible
370 sccm
and Thermchemical effect
600
600
30
30
400
400
20
20
200
200
10
10
00
00
200
200
400
400
600
600
Time
(min)
Time
(min)
800
800
00
1000
1000
concentration
O2Oconcentration
(%(%
in in
air)air)
2
Air flow rate = 5000 sccm
Temperatureat
atreaction
reactionzone
zoneend:
end
Temperature
Coated
5000 sccm
honeycombs
Non-coated
2500 sccm honeycombs
sccm
O370
concentration
1000
1000
60
60
DLR.de • Chart 12
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Solar furnace test rig: Receiver – storage modules
assembly; 1st tests: T along non-coated
storage module (sensible-only storage)
DLR.de • Chart 13
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Comparative testing of storage module and (SiC) receiver
types (190 slm)
3 Cordierite foams
30 ppi; L = 12 cm
1 Cordierite honeycomb
400 cpsi L = 12 cm
SiSiC honeycomb 3 SiSiC foams ReSiC honeycomb
90 cpsi; Schunk 10 ppi; ERBICOL 90 cpsi; Stobbe TC
Weight 1404 g Weight  246 g
Weight  584 g
Length = 15 cm Length = 12 cm
Length = 10 cm
DLR.de • Chart 14
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Comparative performance of SiC receivers tested
1500
Receiver: SiSiC foams
Receiver: SiSiC honeycomb
Air Flow: 190 slm
1400
1300
1200
Receiver: ReSiC honeycomb
1100
o
Temperature ( C)
1000
900
800
700
600
500
400
300
T1
T2
T3
T4
T5
T6
T7
T9
T8
200
100
0
0
100
200
300
Time (min)
400
0
100
T1
T1
T3
T4
T5
T6
T7
T9
T8
T3
T4
T5
T6
T7
T9
T8
Tcamera
200
300
Time (min)
400
0
50
100
150
200
Time (min)
T31030oC
T3930oC
T3930oC
T5 975oC
T5915oC
T5875oC
T6 725oC
T6755oC
T6775oC
250
DLR.de • Chart 15
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Conclusions:
• The construction modularity of the current state-of-the-art storage system in airoperated STPPs provides for implementation of concepts like cascades of
different redox oxide materials and spatial variation of solid material
porosity in three dimensions, to enhance utilization of heat transfer fluid and
storage of its enthalpy.
• However: limited variety of redox oxides available within the particular
temperature range. Co3O4: the most “reliable”, demonstrating full, quantitative
cyclability within a narrow temperature range (“model system”).
• Mn2O3: low cooling rates required for oxidation; large “temperature gap”
between reduction/oxidation temperature. This “disadvantage” though, can be
rendered to benefit within a cascaded structure.
• Relatively high reduction temperatures of both Co3O4 (Tred  895oC) and Mn2O3
(Tred  950oC ).
• Could be achieved in the solar furnace with currently available SiSiC honeycomb
receivers: capability of solar-heating incoming air to  1050oC, and two cordierite
foams downstream ( 8 cm) to  950oC demonstrated.
DLR.de • Chart 16
ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Acknowledgements:
• To EU for financing this work under
the MARIE CURIE ACTION IntraEuropean Fellowships (IEF) Call: FP7PEOPLE-2011-IEF, Grant 300194:
Thermochemical Storage of Solar
Heat via Advanced Reactors/Heat
exchangers based on Ceramic Foams
(STOLARFOAM)
• To DLR Programmdirektion Energie
(PD-E) for funding through Project
Thermochemical storage for CSPapplications
based
on
RedoxReactions – from materials to
processes (REDOXSTORE).
DLR.de • Chart 17
> ASME Power Energy 2015, San Diego, CA, U.S.A. > Agrafiotis, Becker, deOliveira, Roeb, Sattler > July 1st, 2015
Thank you for your attention !
• [email protected]
• [email protected]
• [email protected]