1. Matthias Schmidt, Christian Roßkopf, Marc Linder, Antje Wörner
High Temperature Thermochemical Heat Storage: Operation Modes of a 10kW Pilot Reactor based on CaO/Ca(OH)2
Matthias Schmidt, Christian Roßkopf, Marc Linder, Antje Wörner
Welcome ladies and gentleman
I know it has been a long day already and iam giving the last talk…
we´ve all heard a lot
it’s a big challenge
since we are all working in energy research
conference dinner
Still hold on for 20 min
Interesting results of our ongoing experimentals with a pilot thermochemical heat storage reactor

2. Content
Introduction to thermochemical energy storage based on CaO/ Ca(OH)2
Material properties
Reactor design and test bench development
Experimental results of different operation modes
Summary and outlook

3. Thermochemical Heat Storage reaction system CaO/Ca(OH)2
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Temperature [°C]
Ca(OH)2(s)
exotherm
H2O(g)
CaO(s) + H2O(g) ⇌ Ca(OH)2(s) + ΔH
H2O(g)
CaO(s)
endotherm
Loss free storage of chemical potential
Adjustable storage temperature
Possibility of heat transformation
A gas solid reaction is always characterized through it´s Van´t Hoff plot
Left y-axis is the pressure of my reaction gas, in case of the calciumhydroxide system water vapor
Top x-axis the temperatur at which I need to supply or release heat

4. From a reaction system to a heat storage system operation principle
Process integration:
Gashandling
Reactor Design
Reaction
Material
Properties

5. Material Properties - CaO/Ca(OH)2
Chemical properties:
Reversible reaction ( °C)
Sufficiently fast rates of reaction
No chemical degradation observed
F. Schaube et al., Thermochimica Acta, 2012
Thermophysical properties:
Fine powder (d50 ~ 5 µm)
low permeability
Low thermal conductivity (0.1 – 0.4 W/mK)
commerical available Ca(OH)2
Ca(OH)2 (4 Cycl)

6. Pilot Reactor Design (10kW; 25 kg Ca(OH)2) indirectly operated fixed bed
Source: DEG Eingineering

7. Reaction Gas Handling vapor pressure holder(10mbar – 3bar)

8. Multifunctional Pilot Plant overall experimental set up for CaO/Ca(OH)2 reactor

9. Multifunctional Pilot Plant overall experimental set up for CaO/Ca(OH)2 reactor

10. Multifunctional Pilot Plant overall experimental set up for CaO/Ca(OH)2 reactor

11. Multifunctional Pilot Plant overall experimental set up for CaO/Ca(OH)2 reactor
M. Schmidt et al., Applied Thermal Energy 62 (2014)

12. Multifunctional Pilot Plant overall experimental set up for CaO/ Ca(OH)2 reactor
M. Schmidt et al., Applied Thermal Energy 62 (2014)

13. Charging Mode dehydration of Ca(OH)2 at ph2O = 100mbar

14. Buffer Storage Mode droping inlet temperature, hydration of CaO at 1 bar vapor
Tequilibrium = 490°C
@ (ph2O ~ 1bar)

15. Heat Generation Mode Hydration of CaO, starting temperature of 350°C
Cold - Start Up
If you think about a sensible or latent heat storage system the only possibility to get heat our of the system would be to lower the air inlet temperature
What we do is, we trigger ther chemical reaction through the supply of water vapor and therefore we can immediately increase our air outlet temperature
This is what we call heat generation, and is an outstanding advantage of a TCS-System since such a heat generation mode can be very useful if you think about start up procedures in different applications.

16. Summary and Outlook
CaO / Ca(OH)2 combines low material costs with high storage density
Reactor for 25kg (10 kWh) and 10 kW in operation
Charging at temperatures >400°C demonstrated
Discharging at adjustable temperatures ( °C) and in different operation modes possible
Development of integration strategies (CSP and other applications)
Performance evaluation through system modeling
Material modifications to improve conveyance

17. Thank you! Matthias Schmidt German Aerospace Center (DLR)
Institute of Technical Thermodynamics
Thanks to the european comission which partially founded this work through within the project tcs power
and thank you especially for your questions