Closing the Carbon Cycle: Liquid Fuels from Air, Water and Sunshine
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Closing the Carbon Cycle: Liquid Fuels from Air, Water and Sunshine Klaus S. Lackner, [email protected] Co-authors: Eric Dahlgren, [email protected], Christopher Graves, [email protected], Christoph Meinrenken, [email protected], Tom Socci, [email protected]. Lenfest Center for Sustainable Energy, The Earth Institute, Columbia University 918 Mudd Building (MC 4711), New York, NY 10027 www.energy.columbia.edu This document was originally written as an application for the U.S. DOE funding opportunity “Energy Innovation Hub – Fuels from Sunlight” (DE-FOA-0000214). Participating in this application, the following have contributed to the material presented here: Lynden Archer, Cornell University Sanjoy Banerjee, City University of New York Marco Castaldi, Columbia University Menachem Elimelech, Yale University Vasilis Fthenakis, Columbia University Fernando Garzon, Los Alamos National Laboratory Tony Heinz, Columbia University Upmanu Lall, Columbia University Ah-Hyung (Alissa) Park, Columbia University James Sturm, Princeton University Alan West, Columbia University Hans Ziock, Los Alamos National Laboratory "Closing the carbon cycle: Liquid fuels from air, water and sunshine" Abstract This paper outlines proposed advancements of a coherent set of technologies for a solar-powered system that uses water and CO2 from ambient air to provide sustainable fuels to the world. These fuels would be synthetic liquid hydrocarbons that could power cars, trucks, aircraft, diesel-electric trains and generators, and heat residential and commercial buildings, without changes to current engine technology or fuel distribution infrastructure, and at costs competitive with fossil-based fuels. The explicit goal is to deliver an end-to-end solution for a complete sunlight-to-fuels system, including associated technologies for cost-efficient construction, operation and maintenance. This focus will aid cost-effectiveness and accelerate the transition to market. If desired, the system could also produce electricity, fresh water, and non-fuel hydrocarbons (e.g., plastics), thus further strengthening its economic viability. Fully developed, such a system could satisfy global demand for convenient fuel – yet would operate entirely on carbon recycled from the air, locally-available water, and sunlight. Our approach constitutes a new engineering paradigm: We abandon the economies of scale so common in the energy industry in favor of the mass production of small units. Rather than emphasizing breakthrough advances in component technologies, we believe that the greatest cost reductions will be achieved by a systems approach that exploits economies of mass production, plug- and-play standardization of interfaces, and the fast-paced design innovations that accompany production of small units in large numbers. To see the power of this approach, consider the fact that, kilowatt for kilowatt, a car engine is about fifty times cheaper than a power plant. The individual components of the cycle have been identified and proven feasible: solar panels to convert sunlight to electricity, water desalination, extraction of CO2 from the atmosphere, water electrolysis, and synthesis of a variety of liquid hydrocarbon fuels from CO2 and H2. An integration and implementation effort will merge these subsystems into a highly modular, cyberphysical system of small, interchangeable units, and provide the substantial advances in automation technology that are necessary for successful operation, maintenance, and control. This modular approach will allow for a focus on making the overall system economically viable and sidestep the difficulties of scaling to ever larger units. Furthermore, the high degree of modularity enables the system to continuously improve by leveraging the latest innovations. Indeed, breakthrough advances in component technologies can be incorporated into the system as they are realized. All research should ensure that the resulting technology is fully sustainable in all respects, including from a lifecycle and socioeconomic perspective. In summary, the envisioned solution will make transportation fuels both sustainable and affordable. K.S. Lackner et al. - ii "Closing the carbon cycle: Liquid fuels from air, water and sunshine" Table of Contents I. Introduction ........................................................................................................................... 1 II. System output - Liquid hydrocarbon fuels and their advantages ..................................... 5 II.1.1. Advantages of liquid vs. gaseous fuels .................................................................... 5 II.1.2. Present & future demand – energy supply from the sun .......................................... 6 II.1.3. Products from the proposed system – and who will use them ................................. 6 II.1.4. Additional applications - storage for intermittent renewables.................................. 7 III. The five subsystems ........................................................................................................... 8 III.1. Solar panels ..................................................................................................................... 8 III.1.1. Current state of the art.............................................................................................. 9 III.1.2. Remaining obstacles for integration to sunlight-to-fuels system ........................... 13 III.2. Desalination ................................................................................................................... 16 III.2.1. Current state of the art............................................................................................ 16 III.2.2. Remaining obstacles for integration to sunlight-to-fuels system ........................... 19 III.3. Carbon dioxide capture from air .................................................................................... 20 III.3.1. Current state of the art............................................................................................ 21 III.3.2. Remaining obstacles for integration to sunlight-to-fuels system ........................... 29 III.4. Water electrolysis .......................................................................................................... 30 III.4.1. Current state of the art............................................................................................ 32 III.4.2. Remaining obstacles for integration to sunlight-to-fuels system ........................... 36 III.5. Fuel synthesis ................................................................................................................ 39 III.5.1. Current state of the art............................................................................................ 39 III.5.2. Remaining obstacles for integration to sunlight-to-fuels system ........................... 43 IV. System integration and implementation ....................................................................... 46 IV.1. Overview and objective ................................................................................................. 46 IV.2. Making the system affordable and sustainable .............................................................. 47 IV.2.1. Economies of mass production vs. economies of scale ......................................... 49 IV.2.2. Mass manufacturing, automation and robotics ...................................................... 52 IV.2.3. Financial analysis................................................................................................... 53 IV.2.4. Lifecycle and socio-economic impact analysis ...................................................... 54 IV.2.5. Computational modeling and design optimization ................................................ 55 Bibliography ................................................................................................................................. 57 K.S. Lackner et al. - iii "Closing the carbon cycle: Liquid fuels from air, water and sunshine" I. Introduction Water in the ocean and carbon dioxide in air provide nearly unlimited sources of the atoms from which high performance fuels could be made, and sunshine is a plentiful, sustainable energy source that can be used to convert the essentially zero-energy compounds, carbon dioxide and water, into high energy carbon-rich fuels and oxygen. Biomass production is a natural implementation of such a process and it is the source of most of the hydrocarbon fuels available on Earth. In this process green plants collect CO2 from the air, water from the environment and use the energy in sunshine to convert the oxidized forms of hydrogen and carbon, i.e., H2O and CO2, into reduced forms, e.g. starch, that carry energy and which over geological times have been transformed into the world's fossil fuel deposits. The biofuel approach is an attempt to use this process to produce sustainable liquid hydrocarbons. However, this approach competes with agriculture and relies on photosynthesis, which seems to be limited to very low solar capture efficiency. We propose to improve on this concept with chemical and physical rather than biological means. Carbon dioxide, water, and sunlight as the energy source can be combined to create synthetic hydrocarbon fuels without a biological system [Graves et al.]. By advancing a coherent set of technologies we envision a complete system that uses seawater and atmospheric carbon dioxide for material inputs