High Temperature Thermochemical Water Splitting for Mass Production of Hydrogen Fuel

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1 High Temperature Thermochemical Water Splitting for Mass Production of Hydrogen Fuel Dr. William A. Summers Program Manger, Energy Security Directorate June 11, 2009 Fifth International Hydrail Conference University of NC at Charlotte, Charlotte, NC

2 Outline Large Scale Hydrogen Production Use of Advanced Nuclear Reactors Thermochemical Water-Splitting Solar-driven Hydrogen Production Summary 2

3 Hydrogen as a Transportation Fuel Hydrogen demand for all light-duty vehicles in U.S. by 2050 [1] 110 million tons per year Energy content (HHV) = 13 Quad Current avg. U.S. electricity demand = 450 GW th = 450 GW th How will this hydrogen be produced? Multiple hydrogen production options will be needed Similar energy sources as electricity generation Natural gas, coal (with CO 2 C&S), renewables (wind, solar), nuclear Renewable energy alone will not be adequate [1] National Academy of Engineering Report (2004) 3

4 Current industrial hydrogen market is already significant World H 2 consumption is 42 million tons/yr major users are refineries and fertilizer (ammonia) plants represents 200 GW th of power (5.7 Quad) U.S. produces 9 million tons/yr 1.1% of primary energy (5% of U.S. natural gas usage) Sufficient to power 60 million fuel cell vehicles Equals energy output of 40 nuclear power plants Rapidly growing hydrogen demand in refineries in order to process heavier, higher sulfur crude oils Development of tar sands and oil shale will require additional H2 4

5 Hydrogen Production Options Hydrocarbons from fossil fuels Current method for 98% of hydrogen production Serious environmental and supply concerns Biomass New hydrocarbons produced from solar energy Large land area requirements; limited capacity Water-Splitting Clean and sustainable Needs large energy input to break H-O bonds Requires cost effective, clean primary energy at large scale 5

6 Nuclear Water-Splitting Simple Concept Powerful Impact WATER Heat and Electricity Water- Splitting Process HYDROGEN Nuclear Plant Oxygen Secure Clean Economical 6

7 One View of a Nuclear Hydrogen Future Centralized Nuclear Hydrogen Production Plant Water Heat O 2 High Capacity H 2 Pipeline Industrial H 2 Users H 2 Modular Helium Reactor Thermochemical Process H 2 O H 2 + ½ O 2 Hydrogen Fueled Future Time of Day/Month H 2 Storage Distributed Transport Power Fuel 7

8 Advanced reactors are necessary for high temperature operation Helium Gas-Cooled Reactor Modular Design Underground silo installation Capable of high temp operation (1000 C) Refractory-coated fuel Passive safety Attractive economics Source: General Atomics 8

9 Water-Splitting Options with Nuclear Energy Efficiency* Peak Temp, C Electricity Water Electrolysis 25% Electricity Heat Steam Electrolysis 40-50% Heat Thermochemical 40-50% * HHV H 2 / Nuclear Heat 9

10 DOE s Nuclear Hydrogen Initiative FOCUS: Hydrogen production technologies that are compatible with nuclear energy systems and do not produce greenhouse gases; Baseline technologies include SI, HyS and HTE OBJECTIVE: By 2019, operate the nuclear hydrogen production plant to produce hydrogen at cost competitive with other alternative transportation fuels MAJOR PROGRAM MILESTONES FY2008 FY2009 Commence testing of HTE and SI Integrated Lab-Scale Experiments; Complete HyS electrolyzer stack testing Select hydrogen production technology to be coupled with the NGNP (2005 EPACT requirement) FY10-11 Resolve technical barriers to scale-up of selected technology FY14-16 FY2019 Demonstrate at pilot-plant scale (>1 MW) Demonstrate commercial-scale hydrogen production system for use with advanced nuclear reactors 10

11 Thermochemical water-splitting Series of coupled chemical reactions Water consumption only; all intermediates regenerated Thermal input only (pure cycles) Thermal plus one or more electrochemical steps (hybrid cycles) Extensively studied in 1970s Over 3000 potential cycles have been suggested with 115 cycles reported in literature Thermodynamics dictate high temperature (>800 C) Potential for high plant thermal efficiency; maximizes conversion of nuclear or solar energy into hydrogen 11

12 Technology is still in early stages High chemical-to-hydrogen weight ratios lead to large recycle flows and equipment sizes Major design challenges due to corrosive chemicals, impurities, reactant separation, high temperature heat exchange, and high capital costs Must be scalable to very large capacities (>1000 MW) Plant must be designed for 40+ years of operation Currently in lab-scale development stage 12

13 Integration of HyS with a Nuclear Heat Source PBMR 350 C 950 C Primary Heat Transfer Loop Secondary Heat Transfer Loop 523 C 900 C 13

14 Hybrid Sulfur Thermochemical Process (HyS) Patent for Sulfur Cycle issued to Westinghouse Electric Corporation 1975 Two-compartment Diaphragm Cell Built 1977 Closed-loop Process Demonstration by (W) 1978 Solar-driven Process Design Completed by (W) 1983 Development Hiatus New Process Design work by (W) 2004 Updated Conceptual Design of HyS by SRNL 2005 Proof-of-Concept for PEM-based SDE * 2005 Pressurized, Elevated Temperature SDE Testing 2006 Continuous 100-hour Longevity Test 2007 Testing of 100 lph H 2 Multi-cell Stack 2008 * SO2-Depolarized Electrolyzer 14

15 HyS Process Chemistry The only 2-step, all-fluids thermochemical cycle based on sulfur oxidation and reduction; only S-H-O compounds SO H 2 O H 2 SO 4 + H 2 (1) (electrochemical; C) H 2 SO 4 H 2 O + SO 2 + ½ O 2 (2) (thermochemical; C) Net Reaction: H 2 O H 2 + ½ O 2 (3) 15

16 HyS Process Simplified Flowsheet Water = Hydrogen + Oxygen H 2 Product Electrolyzer System Power Generation H 2 SO 4 Thermal source 22% Electric 78% Power Thermal Energy Sulfuric Acid Decomposition (900 C) H 2 O, SO 2 O 2 By-product Sulfur Dioxide / Oxygen Separation H 2 O, SO 2, O 2 H 2 O Feed 16

17 SRNL s PEM Concept for SO 2 -Depolarized Electrolyzer Proton Exchange Membrane (PEM) Electrochemical Cell SO 2 oxidized at anode to form H 2 SO 4 and hydrogen ions Uses much less electricity than water electrolysis: 0.6 V versus V Requires efficient thermal step to regenerate SO 2 reactant PEM cell concept permits compact design, reduced footprint, and lower cost Leverages extensive R&D and advances being done for PEM fuel cells by auto companies and others 17

18 Single-cell Testing at SRNL Electrolyzer Test Facility 37 configurations tested to date Single cell 60 cm 2 electrolyzer Normal H2 output = lph SO 2 -depolarized electrolyzer Single Cell Electrolyzer (60 cm 2 active area) 18

19 Scale-up and Multi-cell Stack Testing 160 cm 2 plates 3-cell stack Tested up to 86 lph H 2 output 100 lph Stack installed in SRNL test facility 19

20 Solar-Powered HyS Hydrogen Plant Solar power Variable power Energy Thermal Storage Solar AVG power Solar auxiliaries Solar Electricity From Grid SO2 depolarized electrolyzer HyS auxiliaries HyS Process H2 (AVG) =100 TPD Continuous Operation 20

21 Central Receiver Test Facility at Sandia National Lab 21

22 Test Facility Capabilities at SNL Test Facility 5 MW total thermal power Peak flux to 260 w/cm 2 Illumination of target areas to 2,800 m 2 Successfully demonstrated falling particle receiver operation Could be used for HyS demonstration plant 22

23 Solar tower using Falling Particle Receiver Data: Intermediate fluid He Hot sand storage ~1000 C Cold sand storage ~600 C Hot helium 950 C AVG thermal power 329 MW (summer solstice) Helium also provides reboiler heat Yr 2025 design eliminates He loop He 82% 18% 23

24 Solar HyS Plant layout Year 2015 scenario Heliostats tower #1 859,000 m2 Heliostats tower #2 859,000 m2 Electrolysis cell room (red) 10,000 m2 (length 135 m, height 75 m) Total area approximately 1 sq. mile Year 2025 scenario Heliostats tower 1, m2 Electrolysis cell room (red) 10,000 m2 (length 135 m, height 75 m) 24

25 H2 production costs Year 2015 = 4.80 $/kgh2 Year 2025 = 3.19 $/kgh2 25

26 Summary A hydrogen economy will require mass production of hydrogen fuel Thermochemical water-splitting could supply large amounts of hydrogen with no greenhouse gases Advanced nuclear reactors combined with water-splitting processes are being developed by DOE for demonstration by Year 2020 The Hybrid Sulfur Process is a promising option being developed by Savannah River National Laboratory Concepts for a solar-driven HyS Process are also being investigated; on-sun demonstration could be done by 2012 Economics of water-splitting look promising; incentives still needed to accelerate commercialization 26

27 Thank You 27