Development of a Moving Bed Pilot Plant for Thermochemical ...elib.dlr.de/103533/1/Matthias Schmidt-DLR-SolarPACES2015.pdf · Development of a Moving Bed Pilot Plant for Thermochemical

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



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




Thermochemical Energy Storage Reaction system CaO/ Ca(OH)2




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




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


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




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




Heat extraction of moving particles




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




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




[email protected]

German Aerospace Center (DLR), Cologne, Germany

Institute of Engineering Thermodynamics

Thermochemical Systems




Development of a Moving Bed Pilot Plant for Thermochemical ...elib.dlr.de/103533/1/Matthias Schmidt-DLR-SolarPACES2015.pdf · Development of a Moving Bed Pilot Plant for Thermochemical

Documents