Development of a Moving Bed Pilot Plant for
Thermochemical Energy Storage with CaO/ Ca(OH)2
M. Schmidt1, M.Gollsch1, M. Grün2, F. Giger2, M. Linder1
1German Aerospace Center (DLR), Cologne, Germany
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 1
2Buhler AG, Utzwil, Switzerland
Thermochemical energy storage
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Folie 2
CSP
TCS
Chemical
Potential
Power
High Temperature
Thermal Energy
Thermochemical Energy Storage Limestone is a promising storage material
- Environmental friendly and nontoxic
- Production in industrial scale
- Cheap raw material (50€ per ton)
- Additional chemical potential with the
reaction with water vapor
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 3
Thermochemical Energy Storage Reaction system CaO/ Ca(OH)2
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 4
CaO(s) + H2O(g) ⇌ Ca(OH)2(s) + ΔH
charging step - endothermal
150
[kJ/kg]
discharging step - exothermal
Thermochemical Energy Storage Reaction system CaO/ Ca(OH)2
- Temperature range 400-700°C
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 5
CaO(s) + H2O(g) ⇌ Ca(OH)2(s) + ΔH
storage
500
T [°C]
s
300
1330
[kJ/kg]
- Very high energy density – 1330 kJ/kg
- Chemically stored energy is free of
losses
150
[kJ/kg]
700
400
=> Cheap storage capacity cost – 12,5 €ct./kWh
Material properties - CaO/ Ca(OH)2
Chemical properties:
> Grand Renewable Energy 2014 > Matthias Schmidt • Operation Modes of a High Temperature Thermochemical
Heat Storage System in kW-Scale > 28th July to 1st Aug 2014
www.DLR.de • Slide 6
F.Schaube et al. (2012).A thermodynamic and kinetic study of the de- and rehydration of Ca(OH)2 at high H2O partial pressures for thermo-
chemical heat storage. Thermochimica Acta 538(2012) 9 - 20
Thermophysical properties:
- Fine powder (d50 ~ 5 µm)
- Low permeability
- Low thermal conductivity (0.1 – 0.4 W/mK)
=> Complex reactor/heat exchanger design
- Fast reaction kinetics
- Cycle stability
Reactor operation
- Indirectly heated fixed bed
- Demonstration of 8kW thermal power
- Capacity of 10kWh (25 kg of Material)
- Charging and discharging at different
temperatures through adjustment of vapor
partial pressure
=> Upscaling is possible but
economically not reasonable
- Doping of Ca(OH)2 improved flowability (results of
WP2)
-> Indirect moving bed concept seems feasible
Schmidt et al. (2014) Experimental results of a 10 kW high temperautre thermochemical
storage reactor based on calcium hydroxide; Applied Thermal Engineering
M. Linder et al. Thermochemical energy storage in kW-scale based on CaO/ Ca(OH)2.
Energy Procedia, 42, 888-897, 2014
Detachement of power and capacity
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 8
Storage
Storage
R
R
α
x0
x0
r
x1
2h
Roßkopf et al. Improving powder bed properties for thermochemical storage by adding
nanoparticles;. Energy Conversion and Management 2014
- Coating of Ca(OH)2 by addition of
nano particles
-Increased distance between particles
=> enhanced flowability
=> gravity assisted moving bed seems possible
Assessment of reactor geometries
Final design of moving bed reactor
Ca(OH)2 / CaO
Conveyance of material to reactor inlet
container
550 l
load cells
rotary
valve
screw conveyor
with heating jacket
pressure
lock
reactor
Conveyance of reacted material from reactor outlet
rotary
valve
screw
conveyor
pressure
lock
Overall pilot plant design
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 14
Heat extraction of moving particles
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 15
150
170
190
210
230
250
270
290
0
20
40
60
80
100
120
140
160
180
200
0 10 20 30 40 50 60
Weig
ht
[kg
]
Tem
pera
ture
[°
C]
Time [min]
TR_25 TR_28 TR_31 TR_33
T_air_inlet T_air_outlet weight1 weight2
TR_25
TR_28
TR_31
TR_34
T_air_inlet
T_air_outlet
et
Material inlet
Current challenge… Moving bed under reaction conditions
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 16
0
0,5
1
1,5
2
2,5
3
350
400
450
500
550
60 70 80 90 100 110 120
Pre
ssu
re [
bar
]
Tem
pe
ratu
re [
°c]
Time [min]
TR_28 TR_31 TR_34 T_inlet T_outlet P_reactor
TR_25
TR_28
TR_31
TR_34
T_air_inlet
T_air_outlet
et
Material inlet
Summary
- Ca(OH)2 offers low cost storage capacity
- Fixed bed is working but upscaling is economically not viable
- Material improvements focused on flowabilty of fine powder
- Commissioning in first experiments on 10 kW/100 kWh realized
- Extracted sensible heat from the moving particles
- Performed dehydration reaction
Current work:
=> Optimization of plant operation
=> Operation at different charging and discharging temperatures
=> Possibility to utilize sensible heat
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 17
German Aerospace Center (DLR), Cologne, Germany
Institute of Engineering Thermodynamics
Thermochemical Systems
> SolarPACES 2015 > Matthias Schmidt • Development of a Moving Bed Pilot Plant for Thermochemical Energy
Storage with CaO/Ca(OH)2 > 16th Oktober 2015
www.DLR.de • Slide 18