www.dlr.de Slide 1 High Temperature Thermochemical Energy Storage: Operation Modes of a 10kW Pilot Reactor based on CaO/Ca(OH) 2 M. Schmidt, M. Linder, C.Roßkopf, M. Haas, M. Linder, A. Wörner, A. Thess German Aerospace Center (DLR), Cologne, Germany
www.dlr.de Folie 2 High Temperature Thermochemical Energy Storage Applications - Decoupling of solar radiation from eletricity production - Flexibility of conventional power plants - Reutilization of industrial waste heat
www.dlr.de Slide 3 High Temperature Thermochemical Energy Storage Limestone as a promising storage material - Cheap raw material (70$ per ton) - Environmental friendly and nontoxic - Production in industrial scale - Additional chemical potential with the reaction with water vapor
www.dlr.de Slide 4 Thermochemical Energy Storage Reaction System CaO/ Ca(OH) 2 Temperature [ C] 10 727 636 560 496 441 394 352 315 charging step - endothermal 1 Ca(OH) 2(s) CaO (s) + H 2 O (g) Ca(OH) 2(s) + H p gas [bar] 0,1 0,01 CaO (s) H 2 O (g) 0,001 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 Temperatur 1000 / T [1/K]
www.dlr.de Slide 5 Thermochemical Energy Storage Reaction System CaO/ Ca(OH) 2 Temperature [ C] 10 727 636 560 496 441 394 352 315 discharging step storage - exothermal 1 H 2 O (g) Ca(OH) 2(s) CaO (s) + H 2 O (g) Ca(OH) 2(s) + H p gas [bar] 0,1 0,01 CaO (s) - Very high energy density 0,4 kwh/kg - Adjustability of charge and discharge temperature - Possibility to transform heat - Loss free storage of chemical potential 0,001 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 Temperatur 1000 / T [1/K]
www.dlr.de Slide 6 Material Properties - CaO/Ca(OH) 2 Chemical properties: Thermophysical properties: F.Schaube et al. (2012).A thermodynamic and kinetic study of the de- and rehydration of Ca(OH) 2 at high H 2 O partial pressures for thermochemical heat storage. Thermochimica Acta 538(2012) 9-20 C. Roßkopf et. al (2014) Investigation of Nano Coated CaO Ca(OH) 2 Cycled in Thermochemical in a Thermochemical Heat Storage, submitted
www.dlr.de Slide 7 Pilot Reactor - 10kW, 25kg Ca(OH) 2 plate heat exchanger Reaction Bed Heat Conduction Heat Flux vreaction Bed HTF HTF
www.dlr.de Slide 8 Pilot Reactor - 10kW, 25kg Ca(OH) 2 plate heat exchanger Reaction Bed CaO (s) + H 2 O (g) Ca(OH) 2(s) + H Heat Conduction 510 C Heat Flux vreaction Bed HTF HTF
www.dlr.de Slide 9 Charging Mode 520 1,2 500 1 480 0,8 460 0,6 440 0,4 Pressure [bar] Temperature [ C] Dehydration of Ca(OH)2 at 100mbar vapor pressure T_air_in T_R_03 T_R_05 T_R_11 T_R_12 T_air_out p_reactor 420 0,2 400 0 0 50 100 150 200 250 Time [min] 300 350 400 450
www.dlr.de Slide 10 Discharging Mode hydration of CaO at 1 bar vapor 550 500 Temperature [ C] 450 400 T_air_inlet T_R_01 T_R_05 T_R_11 T_R_13 350 300 0,00 20,00 40,00 60,00 80,00 100,00 120,00 140,00 160,00 180,00 time [min]
www.dlr.de Chart 11 Heat Generation Mode Hydration of CaO, starting temperature of 350 C 1,00 490 0,90 470 0,80 450 0,70 Temperature [ C] 430 410 390 0,60 0,50 0,40 0,30 Conversion T_air_inlet T_air_outlet Conversion 370 0,20 350 0,10 330 0,00 0,00 50,00 100,00 150,00 200,00 250,00 time [min]
www.dlr.de Slide 12 Next Steps Separation of Power and Capacity Capacity HTF Process integration: HTF Process integration: P_reactor ~ $ Capacity ~ A_hex ~ $$$
www.dlr.de Slide 13 Next Steps Separation of Power and Capacity Pilot Plant in 2015 Capacity: 100 kwh ~ 250 kg Ca(OH) 2 Reactor: 10 kw ~ 25 kg/h
www.dlr.de Slide 14 Summary - Thermochemical energy storage with CaO/ Ca(OH) 2 demonstrated in kw scale - Peak power of 8 kw - Charging at 450 C - Discharging at 490 C and 545 C - Demonstration of moving bed pilot plant scheduled for beginning of 2015
German Aerospace Center (DLR), Cologne, Germany Institute of Technical Thermodynamics Thermo-chemical Systems matthias.schmidt@dlr.de