Sustainable energy storage in chemical fuels for CO 2 neutral energy generation: a plasma perspective Richard van de Sanden Dutch Institute for Fundamental Energy Research, P.O.Box 1207, 3430 BE Nieuwegein, The Netherlands Conférence de l Institut Coriolis pour l Environnement de l École Polytechnique 2013
The TeraWatt Challenge (15 TW) see also : M.I. Hoffert et al. Nature 385, 881 (1998) R.E. Smalley, MRS Bulletin 30 412 (2005)
2013 Energy Burning fossil fuels CO 2! World population (Billion) 10 8 6 4 2 Oil Population 0 0 500 1000 1500 Year 2000 2500 3000
The Terawatt challenge Prim. Energy Consumption [Quadrill. Btu] 1000 800 600 400 200 Non-OECD OECD 2000 2010 2020 2030 2040 8 6 4 2 World Population [Billion] U.S.. Energy Information Agency Annual Energy Outlook 2011 DOE/EIA-0383(2011)
The Terawatt challenge Prim. Energy Consumption [Quadrill. Btu] 1000 800 600 400 200 Non-OECD OECD 2000 2010 2020 2030 2040 40 30 20 10 World CO 2 Emission [Gt] U.S.. Energy Information Agency Annual Energy Outlook 2011 DOE/EIA-0383(2011)
The TeraWatt Challenge Sustainable, CO 2 neutral, energy infrastructure essential see also : M.I. Hoffert et al. Nature 385, 881 (1998) R.E. Smalley, MRS Bulletin 30 412 (2005)
Contents The TeraWatt Challenge: CO 2 neutral energy supply Sustainable Energy Generation Storage and Transport of Energy: Solar Fuels Solar Fuels from CO 2 and H 2 O: conversion processes Water splitting CO 2 activation Plasma activation of CO 2 Conclusions and Outlook
Sustainable energy - is there enough? More sustainable energy than global energy demand The big sources: solar wind biomass geothermal ocean/wave hydro
Sustainable energy future ITER: 2020 first plasma Commercial: 2040? Transport: need for fuels (air transport)
Solar power generation: DoE Sunshot
Solar power generation: Economy of scale Price-experience curve of silicon PV modules (combined effects of innovation, experience and scale) Grid parity ~1 /W p Clear economy of scale
Grid parity in Europe 2025 From 2020 a significant fraction is sustainable!
However. German solar and wind energy Sustainable power generation is booming but it is inhomogeneous and intermittent with time-scales ranging from minutes to months Solution: Mismatch between supply and demand Energy storage
Sustainable energy - storage needed Storing energy: mechanical electrical electro-chemical chemical water reservoirs chemical batteries Artificial chemical fuel stored heat
Storing and Transport of Energy Presently: 85% of the global energy is transported by fuels Carbon containing fuels (hydrocarbons, alcohols, etc.) generated from CO 2 and H 2 O to store sustainable energy: Solar Fuels
Solar Fuels Large potential to contribute to a CO 2 neutral energy infrastructure Storage and transport of sustainable energy in chemical bonds: close to present infrastructure Large efforts world wide on Solar Fuels:
Solar Fuels Large potential to contribute to a CO 2 neutral energy infrastructure Storage and transport of sustainable energy in chemical bonds: close to present infrastructure Large efforts world wide on Solar Fuels: Basically splitting H 2 O or activating CO 2 using direct solar (heat & light) or sustainably generated electrical energy End product carbon containing fuels: Solar Fuels
Fuel processing from H 2 O Basically production of H 2 : By splitting H 2 O: 1) H 2 O H 2 + ½ O 2 H 2 production main activity globally Hyundai i35 first commercial car on H 2 + fuel cell
Fuel processing from H 2 O or CO 2 Basically production of H 2 or CO : By splitting H 2 O: 1) H 2 O H 2 + ½ O 2 or activating CO 2 : 1) CO 2 CO + ½ O 2 Cars fueled by wood or coal gas during WWII
Fuel processing from CO 2 and H 2 O: syngas Production of syngas H 2 and CO : By splitting H 2 O: 1) H 2 O H 2 + ½ O 2 2) followed by a reverse watershift reaction H 2 + CO 2 H 2 O + CO (endothermic) or activating CO 2 : 1) CO 2 CO + ½ O 2 2) followed by a watershift reaction CO + H 2 O CO 2 + H 2 (exothermic) Syngas: by means of Fisher-Tropsch process carbon containing fuels
Solar Fuels CO 2 Hydrogenation Methane Methanol Air Captured CO 2 CO 2 Solar energy conversion: H 2 O H 2 + ½O 2 RWGS H 2 CO CO FT Fuel CO 2 CO + ½O 2 water WGS H 2 Courtesy Wim Haije (ECN) FT=Fischer-Tropsch reaction (R)WGS=(reverse) watergas shift
Gas-to-liquid from syngas: Fisher-Tropsch Shell Qatari plant (2009) Methane reformation: CH 4 + H 2 O CO + 3H 2 C-fuels Investment of 19 B$; Revenue 4 B$/yr Large scale proven However still based on fossil fuels Ref. Bloomberg
Current Energy generation infrastructure Electricity grid Sun Wind Sun or Wind Energy Plant Gas (or fossil) Plant Fossil Water Liquid fuels or raw materials for industry Gas buffer Gas grid Fossil current infrastructure of energy system
Towards the Renewable Energy infrastructure Indirect Electricity grid Sun Wind Sun or Wind Energy Plant Direct Solar Fuel Plant CO2 Gas (or fossil) Plant Fossil Water Liquid fuels or raw materials for industry Gas buffer Gas grid Fossil Solar Fuels Production from CO 2 and H 2 O using sustainable energy fitted in our current infrastructure
Full Sustainable Energy Infrastructure Indirect Electricity grid Sun Wind Sun or Wind Energy Plant Direct Solar Fuel Plant CO2 Gas Plant Water Liquid fuels or raw materials for industry Gas buffer Gas grid Solar Fuels Production from CO 2 and H 2 O as storage using intermittent sustainable energy
Contents The TeraWatt Challenge: CO 2 neutral energy supply Sustainable Energy Generation Storage and Transport of Energy: Solar Fuels Solar Fuels from CO 2 and H 2 O: conversion processes Water splitting CO 2 activation Plasma activation of CO 2 Conclusions and Outlook
Solar Fuels CO 2 Hydrogenation Methane Methanol Air Captured CO 2 CO 2 Solar energy conversion: H 2 O H 2 + ½O 2 RWGS H 2 CO CO FT Fuel CO 2 CO + ½O 2 water WGS H 2 Courtesy Wim Haije (ECN) FT=Fischer-Tropsch reaction (R)WGS=(reverse) watergas shift
Solar energy conversion (direct & indirect) Courtesy Wim Sinke (ECN) Man-made, articifical Solar (modified) natural, living European Science Foundation, Science Policy Briefing 34 (Sept. 2008) Photosynthetic Micro organism (> 5%) Biomass (< 1%) Primary and secondary biofuels
Solar energy conversion (direct & indirect) Courtesy Wim Sinke (ECN) Man-made, articifical (modified) natural, living Solar European Science Foundation, Science Policy Briefing 34 (Sept. 2008) Thermochemical Conversion (> 5%) Photosynthetic Micro organism (> 5%) Biomass (< 1%) Primary and secondary biofuels
Thermochemical using CSP (direct) Concentrated solar power (CSP) CeO 2 + sunlight CeO 2-x + 1/2x O 2 CO 2 + CeO 2-x CO + CeO 2 Or based on ZnO, Fe 3 O 4 Nanostructured Cyclic, materials solar + to catalysis CO efficiency: essential 3-4% Steinfeld group (ETH Zurich), Science 330 1798 (2010)
Solar energy conversion (direct & indirect) Courtesy Wim Sinke (ECN) Man-made, articifical Photocatalytic Nanodevices (> 5%) (modified) natural, living Solar European Science Foundation, Science Policy Briefing 34 (Sept. 2008) Thermochemical Conversion (> 5%) Photosynthetic Micro organism (> 5%) Biomass (< 1%) Primary and secondary biofuels
Direct photocatalytic conversion of H 2 O The challenge Which approach is most promising? Nanostructured materials and catalysis essential But also photon management: plasmonics, etc. Courtesy Roel van de Krol (HZ Berlin)
Photocatalytical splitting of water Different anorganic materials Graetzel, Nature, 414, 15 Nov. (2001) 338. Direct sunlight into hydrogen Science 331 746 (2011) 1-3% 2H 2 O 2H 2 + O 2 Nanostructured materials and catalysis essential
Water splitting Photo-electrochemical cells: generation of solar H 2 Courtesy Kevin Sivula
Watersplitting using electrochemical cell For large scale deployment: Elements of hope Nocera group (MIT): basically tandem a-si solar cell with Co based catalyst 2H 2 O 2H 2 + O 2
Direct photocatalytic conversion of CO 2 The challenge To tailor the catalyst to optimally use the solar spectrum for activating the catalyst η = 0.0148% Difficult to activate CO 2 by photocatalysis CO 2 + 2H 2 O CH 4 + 2O 2 Nanostructured materials and catalysis essential Roy, Varghese, Paulose, Grimes, ACSNano 4, 1260 (2010)
Solar energy conversion (direct & indirect) Courtesy Wim Sinke (ECN) Man-made, articifical PV conversion + Electrolysis (> 20%) Photocatalytic Nanodevices (> 5%) (modified) natural, living Solar European Science Foundation, Science Policy Briefing 34 (Sept. 2008) Thermochemical Conversion (> 5%) Photosynthetic Micro organism (> 5%) Biomass (< 1%) Primary and secondary biofuels
Watersplitting using PV & electrolyser Efficiency >> 20 % Efficiency 70-80 % sustainable energy 2H 2 O 2H 2 + O 2 Advantage: separate optimization possible Current bottleneck: use of scarce materials (a.o. Pt) * H 2 generation from steam reformation <1 /kg
Watersplitting using PV & electrolyser Efficiency >> 20 % sustainable energy Efficiency 70-80 % > 8 /kg * >16 /kmol 2H 2 O 2H 2 + O 2 Advantage: separate optimization possible Current bottleneck: use of scarce materials (a.o. Pt) * H 2 generation from steam reformation <1 /kg
Electric energy conversion: electrolysis Electrical energy to CO > 10% Electrochemical Conversion K.P. Kuhl et al., Energy Environ. Sci. 5 7050 (2012)
Electric energy conversion: electrolysis Electrical energy to CO > 10% Difficult to activate CO 2 due to solubility Electrochemical Conversion K.P. Kuhl et al., Energy Environ. Sci. 5 7050 (2012)
Contents The TeraWatt Challenge: CO 2 neutral energy supply Sustainable Energy Generation Storage and Transport of Energy: Solar Fuels Solar Fuels from CO 2 and H 2 O: conversion processes Water splitting CO 2 activation Plasma activation of CO 2 Conclusions and Outlook
Solar energy conversion (direct & indirect) Man-made, articifical Solar Solar to electricity + Plasma conversion PV conversion + Electrolysis (> 20%) Photocatalytic Nanodevices (> 5%) Thermochemical Conversion (> 5%) Courtesy Wim Sinke (ECN) Solar Fuels (modified) natural, living European Science Foundation, Science Policy Briefing 34 (Sept. 2008) Photosynthetic Micro organism (> 5%) Biomass (< 1%) Primary and secondary biofuels
Solar Fuels CO 2 Hydrogenation Methane Methanol Air RWGS CO Captured CO 2 CO 2 Conversion: Electrocatalysis Photocatalysis Thermocatalysis Plasma activation H 2 CO FT Fuel water WGS H 2 Direct plasma activation of CO 2 Courtesy Wim Haije (ECN) FT=Fischer-Tropsch reaction (R)WGS=(reverse) watergas shift
Plasmachemical activation of CO 2 Thermodynamics Why plasma? Higher energy density medium Exploit the nonequilibrium?? Concentrating the energy input on degrees of freedom which are essential for CO 2 dissociation!! Energy efficiency: ~ 41% Alex Fridman (Drexel Univ., US) Plasma-chemical Conversion
What is plasma? Gaseous medium composed of : Atoms Molecules Radicals Ions (negative, positive) Electrons T 1 ev T electron T gas 1 atm p All possibly in the excited state (internal energy!) Nonequilibrium medium nonequilibrium distributions (non-maxwellian, non-boltzmann) Used abundantly in e.g. materials processing *1 ev = 11600 K
Electric energy conversion: plasmachemical Thermodynamics Why plasma? Higher energy density medium Exploit the nonequilibrium?? No use of scarce materials: free electrons and electric field do the job Energy efficiency: ~ 41% Large scale possible (15 TW!!) Plasmachemical Conversion
Plasmas and large scale Hüls reactor H 2 and carbon black production from coke and natural gas thermal arc reactors Acetylene production from coke and natural gas in Hüls arc reactor But also note that many large scale industries heavily depend on plasma technology: IC, display, coatings, solar, etc.
Energy efficient dissociation using plasma? Can it be done energy efficiently? Cost of plasmas expensive energy-wise: Creating electron-ion pair typically > 30 ev!* electrons electric field collisions ionization *1 ev = 100 kj/mol
Energy efficient CO 2 dissociation with plasma? CO 2 potential Can it be done energy efficiently? Cost of plasmas expensive energy-wise: Creating electron-ion pair typically > 30 ev!* Dissociation energy CO 2 5.5 ev, but more is needed to get dissociation by direct electron impact (dissociative branch) If electrons must do the job directly: no energy efficient dissociation possible!!
Optimal vibrational state CO 2 dissociation electrons electric field collisions Vib. Energy [cm -1 ] 3000 2000 1000 vibrational excitation ν 2 ν 2 Can we controle this? ν 1 ν 3 (4.26 µm: IR) Rusanov et al. Usp. Fiz. Nauk. 134 185 (1981)
Electron energy loss in CO 2 plasma electrons electric field collisions vibrational excitation Electron energy loss depends on reduced electric field depends on average electron energy Rusanov et al. Usp. Fiz. Nauk. 134 185 (1981)
V-V exchange and VT relaxation electrons electric field collisions vibrational excitation V-V relaxation much faster than V-T relaxation for low v number: leads to T vib > T gas Rusanov et al. Usp. Fiz. Nauk. 134 185 (1981)
Nonequilibrium effects: Treanor distribution electrons T electron > T vib > T gas electric field collisions vibrational excitation Treanor like distribution: overpopulation of higher vibrational states leads to lower activation energies, faster kinetics Rusanov et al. Usp. Fiz. Nauk. 134 185 (1981)
Energy efficient dissociation using plasma? Can it be done energy efficiently? electrons Cost of plasmas expensive energy-wise: Creating electron-ion pair typically > 30 ev! electric field Additionally use radical O (!) CO 2 CO + O followed by CO 2 + O CO+ O 2 so overall CO 2 CO + ½O 2 (ΔH=5.5 ev) (ΔH=0.3 ev) (ΔH=2.9 ev) collisions radical chemistry A.V. Eletskii, B.M. Smirnov, Pure. Appl. Chem. 57 1235 (1985)
Energy efficient dissociation of CO 2 Can it be done energy efficiently? Yes if the following plasma aspects are considered: Create nonequilibrium plasma with T electron > T vib > T gas Low mean electron energy (1-2 ev) to excite dominantly lower vibrational states and sufficient ionization degree (>10-5 ): Vibrational pumping (nonequilibrium effect!) and low V-T relaxation takes care of high population of vibrational states required for efficient dissociation and fast kinetics Re-use atomic oxygen to dissociate aditionally CO from CO 2 (high p, low conversion!)
Energy efficient dissociation of CO 2 Can it be done energy efficiently? Yes if the following plasma aspects are considered: Create nonequilibrium plasma with T electron > T vib > T gas Engineering specs to choose plasma: Low mean electron energy (1-2 ev) to excite dominantly lower vibrational states and sufficient ionization degree (>10-5 ): Use kinetics, time scales of relaxation Vibrational pumping (nonequilibrium effect!) and low V-T relaxation takes care of high population of vibrational states required for efficient dissociation and fast kinetics Design electric field configuration Re-use atomic oxygen to dissociate aditionally CO from CO 2 High pressure to minimize wall losses (high p, low conversion!)
Choice of plasma 1-5mm http://www.pages.drexel.edu/~rp g32/research.htm Dielectric barrier discharge Surface discharge Non-thermal process (room temp) Throughput necessary (scale!) Scalable (stacked microreactors?) Essentially nonequilibrium Controle of EEDF Gliding arc DBD/Packed bed Catalytic reaction enhanced by Plasma catalysis. Microwave discharge Corona discharge http://www.jehcenter.org/electro/plasma/theory.html Courtesy Tomohiro Nozaki (Tokyo Institute of Technology)
(Sub-)atmospheric μwave discharge Sub-atmospheric CO 2 plasmas: CO 2 CO + ½O 2
Various nozzle positions/types explored 1 2 3 4 2 915 MHz Nozzle configurations/types: 1. Straight ( 26 mm) 2. Symmetric ( 26 mm: 5 mm & 10 mm throat) 3. Laval ( 26 mm: 5 mm throat) 4. Double nozzle (Laval/Cu exit nozzle of 5 mm) E010 or TM010 mode @ 3kW: E max = 27 kv/m Cavity (12.4 cm) Nozzle Positions I z = -3 cm II z = 0 cm I II III V IV z III z = 12.4 + 0 cm Engineering knobs to controle plasma IV z = 12.4 + 5 cm generation to obtian high power V efficiency z = 12.4 + 3 cm of CO 2 activation
Experimental Results: supersonic region CO produced at expense of CO 2 Energy efficiency: CO 2 CO + ½O 2 H = 2.9 ev η = H/E CO 80 70 Output flow [slm] 60 50 40 30 20 CO 2 CO 10 0 0 2000 4000 6000 8000 Power [W] O 2 10 mm symmetric nozzle at exit of RF cavity RF input power 3020-8010 W Gas pressure reaction chamber 190-250 mbar Expansion chamber 0.3..0.4 mbar Energy spent per CO 2 molecule 0.56..1.49 ev Constant CO 2 flow of 75 SLM
Experimental Results: supersonic region CO produced at expense of CO 2 CO 2 CO + ½O 2 η = H/E CO 80 70 Output flow [slm] 70 60 50 40 30 20 10 CO 2 CO Efficency [%] 60 50 40 30 20 10 η power Energy efficiency [%] Conversion efficiency [%] β diss 0 O 2 0 2000 4000 6000 8000 Power [W] 0 0 2000 4000 6000 8000 Power [W] Constant CO 2 flow of 75 SLM
Experimental Results: supersonic region CO produced at expense of CO 2 CO 2 CO + ½O 2 η = H/E CO Output flow [slm] 80 70 60 50 40 30 20 10 0 CO 2 CO 10 Power efficiency O 2 0 60% 0 2000 4000 6000 8000 0 2000 4000 6000 8000 Power [W] Power [W] Efficency [%] 70 60 50 40 30 20 η power Energy efficiency [%] Conversion efficiency [%] β diss Dissociation (@3.6kW) 11% Constant CO 2 flow of 75 SLM
Reported results on energy efficiency CO 2 CO + ½O 2 ΔH = 2.9 ev Energy efficiency η = ΔH/E CO Literature reports > 50% energy efficiency of CO 2 dissociation! Key is reduced electric field and energy per molecule! From A. Fridman, Plasma Chemistry (Taylor&Francis 2009)
CO 2 activation using plasma Efficiency > 20 % Efficiency 70-80 % sustainable energy CO 2 CO + ½O 2 Advantage: separate optimization possible * compare with electrolysis H 2 O > 16 /kmol
CO 2 activation using plasma Efficiency > 20 % sustainable energy Efficiency 70-80 % 97 kwh/kmol * @ η power =80% CO 2 CO + ½O 2 Advantage: separate optimization possible * compare with electrolysis H 2 O > 16 /kmol
Conclusions and Outlook Sustainable energy generation within reach : Clear economy of scale, hugh capacity deployed Next challenge: storing sustainable energy in solar fuels Cost effective CO 2 neutral energy infrastructure In line with the present energy infrastructure Several approaches are adopted: H 2 O splitting prominent, CO 2 activation still in infancy phase, direct and indirect Plasma activation of CO 2 approach highlighted: Nonequilibrium essential to obtain high energy efficiency Power efficiency obtained so far ~ 60% ; 80% within reach Next challenge: - diagnose the plasma (E/n gas, CO 2 (r,v), n e, etc.) - gas stream separation without energy penalty
Nonequilibrium: controlling complexity Directing Matter and Energy Five challenges for science and the imagination, Report Basic Energy Science Advisory Committee One of the five challenges directly linked with plasma science: How do we characterize and control matter away, especially very far away, from equilibrium?
Ackowledgements FOM-DIFFER (Solar Fuels) Waldo Bongers Adelbert Goede Martijn Pieter-Willem Groen FOM-DIFFER (Fusion) Tony Donne et al. Greg De Temmerman et al. Institute fur Plasmaforschung Jochen Kopecki Martina Leins Andreas Schulz Matthias Walker TU/e Richard Engeln Stefan Welzel Srinath Ponduri Florian Brehmer Ma Ming