1. A Global Perspective on the Role of Solar Energy as a Primary Energy Source Present Primary Power Mix Future Constraints Imposed by Sustainability Theoretical and Practical Energy Potential of Various Renewables Challenges to Exploit Renewables Economically on the Needed Scale Nathan S. Lewis, California Institute of Technology Division of Chemistry and Chemical Engineering Pasadena, CA 91125 http://nsl.caltech.edu

2. Mean Global Energy Consumption, 1998 GasHydro Renew Total: 12.8 TW U.S.: 3.3 TW (99 Quads)

3. Energy From Renewables, 1998 10 -5 0.0001 0.001 0.01 0.1 1 ElectHeatEtOHWindSolar PVSolar Th.Low T Sol HtHydroGeothMarine Elec Heat EtOH Wind Sol PV SolTh LowT Sol Hydro Geoth Marine TW Biomass 5E-5 1E-1 2E-3 1E-4 1.6E-3 3E-1 1E-2 7E-5

4. (in the U.S. in 2002) 1-4 ¢ 2.3-5.0 ¢ 6-8 ¢ 5-7 ¢ Today: Production Cost of Electricity 6-7 ¢ 25-50 ¢ Cost, ¢/kW-hr

5. Energy Costs Brazil Europe $0.05/kW-hr www.undp.org/seed/eap/activities/wea

6. Energy Reserves and Resources Reserves/(1998 Consumption/yr) Resource Base/(1998 Consumption/yr) Oil 40-78 51-151 Gas 68-176207-590 Coal 2242160 Rsv=Reserves Res=Resources

7. Abundant, Inexpensive Resource Base of Fossil Fuels Renewables will not play a large role in primary power generation unless/until: –technological/cost breakthroughs are achieved, or –unpriced externalities are introduced (e.g., environmentally -driven carbon taxes) Conclusions

8. “It’s hard to make predictions, especially about the future” M. I. Hoffert et. al., Nature, 1998, 395, 881, “Energy Implications of Future Atmospheric Stabilization of CO 2 Content adapted from IPCC 92 Report: Leggett, J. et. al. in Climate Change, The Supplementary Report to the Scientific IPCC Assessment, 69-95, Cambridge Univ. Press, 1992 Energy and Sustainability

9. Population Growth to 10 - 11 Billion People in 2050 Per Capita GDP Growth at 1.6% yr -1 Energy consumption per Unit of GDP declines at 1.0% yr -1

10. Energy Consumption vs GDP GJ/capita-yr

11. 1990: 12 TW 2050: 28 TW Total Primary Power vs Year

12. M. I. Hoffert et. al., Nature, 1998, 395, 881 Carbon Intensity of Energy Mix

13. CO 2 Emissions for vs CO 2 (atm) Data from Vostok Ice Core

14. Projected Carbon-Free Primary Power

15. “These results underscore the pitfalls of “wait and see”.” Without policy incentives to overcome socioeconomic inertia, development of needed technologies will likely not occur soon enough to allow capitalization on a 10-30 TW scale by 2050 “Researching, developing, and commercializing carbon-free primary power technologies capable of 10-30 TW by the mid-21 st century could require efforts, perhaps international, pursued with the urgency of the Manhattan Project or the Apollo Space Program.” Hoffert et al.’s Conclusions

16. If we need such large amounts of carbon-free power, then: current pricing is not the driver for year 2050 primary energy supply Hence, Examine energy potential of various forms of renewable energy Examine technologies and costs of various renewables Examine impact on secondary power infrastructure and energy utilization Lewis’ Conclusions

17. Nuclear (fission and fusion) 10 TW = 10,000 new 1 GW reactors i.e., a new reactor every other day for the next 50 years Õ2.3 million tonnes proven reserves; 1 TW-hr requires 22 tonnes of U Õ Hence at 10 TW provides 1 year of energy Õ Terrestrial resource base provides 10 years of energy ÕWould need to mine U from seawater (700 x terrestrial resource base) Carbon sequestration Renewables Sources of Carbon-Free Power

18. Carbon Sequestration

19. Hydroelectric Geothermal Ocean/Tides Wind Biomass Solar Potential of Renewable Energy

20. Hydroelectric Geothermal Wind Biomass Solar Potential of Renewable Energy

21. Hydroelectric Gross: 4.6 TW Technically Feasible: 1.6 TW Economic: 0.9 TW Installed Capacity: 0.6 TW

22. Geothermal Mean flux at surface: 0.057 W/m 2 Continental Total Potential: 11.6 TW

23. Wind 4% Utilization Class 3 and Above 2-3 TW

24. Solar: potential 1.2x10 5 TW; practical 600 TW Energy in 1 hr of sunlight  14 TW for a year

25. Solar Land Area Requirements 3 TW

26. Solar Land Area Requirements 6 Boxes at 3.3 TW Each

27. Light Fuel Electricity Photosynthesis Fuels Electricity Photovoltaics H O O H 2 2 2 sc M e e M CO Sugar H O O 2 2 2 Energy Conversion Strategies Semiconductor/Liquid Junctions

28. Global: Top Down Requires Large Areas Because Inefficient (0.3%) 3 TW requires ≈ 600 million hectares = 6x10 12 m 2 20 TW requires ≈ 4x10 13 m 2 Total land area of earth: 1.3x10 14 m 2 Hence requires 4/13 = 31% of total land area Biomass Energy Potential

29. Land with Crop Production Potential, 1990: 2.45x10 13 m 2 Cultivated Land, 1990: 0.897 x10 13 m 2 Additional Land needed to support 9 billion people in 2050: 0.416x10 13 m 2 Remaining land available for biomass energy: 1.28x10 13 m 2 At 8.5-15 oven dry tonnes/hectare/year and 20 GJ higher heating value per dry tonne, energy potential is 7-12 TW Perhaps 5-7 TW by 2050 through biomass (recall: $1.5-4/GJ) Possible/likely that this is water resource limited Challenges for chemists: cellulose to ethanol; ethanol fuel cells Biomass Energy Potential Global: Bottom Up

30. 19501960 1970 1980 1990 2000 5 10 15 20 25 Efficiency (%) Year crystalline Si amorphous Si nano TiO 2 CIS/CIGS CdTe Efficiency of Photovoltaic Devices

31. Cost/Efficiency of Photovoltaic Technology Costs are modules per peak W; installed is $5-10/W; $0.35-$1.5/kW-hr

32. SOLAR ELECTRICITY GENERATION Develop Disruptive Solar Technology: “Solar Paint” Grain Boundary Passivation Interpenetrating Networks while Minimizing Recombination Losses Challenges for the Chemical Sciences Increase  Lower d

33. The Need to Produce Fuel “Power Park Concept” Fuel Production Distribution Storage

34. Photovoltaic + Electrolyzer System

35. O2O2 A H2H2 e-e- cathode anode Fuel Cell vs Photoelectrolysis Cell H2H2 anode cathode O2O2 Fuel Cell MEA Photoelectrolysis Cell MEA membrane MO x MS x e-e- H+H+ H+H+

36. Need for Additional Primary Energy is Apparent;Optionality is Needed Scientific/Technological Issues Provide Disruptive Solar Technology: Cheap Solar Fuel Inexpensive conversion systems, effective storage/distribution systems Policy Issues Energy Security, National Security, Environmental Security, Economic Security Consensus: PCAST, DOE BESAC (Secure Energy Future), DOE H 2, NRC/NAS, Chu, Smalley, Kohn, Heeger Will there be the needed commitment? Is Failure an Option? Summary

37. Global Energy Consumption

38. Carbon Intensity vs GDP

39. Matching Supply and Demand Oil (liquid) Gas (gas) Coal (solid) Transportation Home/Light Industry Manufacturing Conv to e - Pump it around Move to user Currently end use well-matched to physical properties of resources

40. Matching Supply and Demand Oil (liquid) Gas (gas) Coal (solid) Transportation Home/Light Industry Manufacturing Conv to e - Pump it around Move to user If deplete oil (or national security issue for oil), then liquify gas,coal

41. Matching Supply and Demand Oil (liquid) Gas (gas) Coal (solid) Transportation Home/Light Industry Manufacturing Conv to e - Pump it around Move to user If carbon constraint to 550 ppm and sequestration works -CO 2

42. Matching Supply and Demand Oil (liquid) Gas (gas) Coal (solid) Transportation Home/Light Industry Manufacturing Conv to e - Pump it around Move to user as H 2 If carbon constraint to <550 ppm and sequestration works -CO 2

43. Matching Supply and Demand Oil (liquid) Gas (gas) Coal (solid) Transportation Home/Light Industry Manufacturing Pump it around If carbon constraint to 550 ppm and sequestration does not work Nuclear Solar ? ?

44. Quotes from PCAST, DOE, NAS The principles are known, but the technology is not Will our efforts be too little, too late? Solar in 1 hour > Fossil in one year 1 hour $$$ gasoline > solar R&D in 6 years Will we show the commitment to do this? Is failure an option?

45. US Energy Flow -1999 Net Primary Resource Consumption 102 Exajoules

46. Tropospheric Circulation Cross Section

47. Primary vs. Secondary Power Hybrid Gasoline/Electric Hybrid Direct Methanol Fuel Cell/Electric Hydrogen Fuel Cell/Electric? Wind, Solar, Nuclear; Bio. CH 4 to CH 3 OH “Disruptive” Solar CO 2 CH 3 OH + (1/2) O 2 H 2 O H 2 + (1/2) O 2 Transportation Power Primary Power

48. Challenges for the Chemical Sciences CHEMICAL TRANSFORMATIONS Methane Activation to Methanol: CH 4 + (1/2)O 2 = CH 3 OH Direct Methanol Fuel Cell: CH 3 OH + H 2 O = CO 2 + 6H + + 6e - CO 2 (Photo)reduction to Methanol: CO 2 + 6H + +6e - = CH 3 OH H 2 /O 2 Fuel Cell: H 2 = 2H + + 2e - ; O 2 + 4 H + + 4e- = 2H 2 O (Photo)chemical Water Splitting: 2H + + 2e - = H 2 ; 2H 2 O = O 2 + 4H + + 4e - Improved Oxygen Cathode; O 2 + 4H + + 4e - = 2H 2 O