WindFuels – Competitive Transportation Fuels From Wind Energy and Waste CO 2
It is essential for the market to help drive the dramatic cut needed in CO2 emissions to prevent a climate disaster in this century. We show that the economics for producing clean liquid hydrocarbons and alcohols from water and waste CO2 on wind farms improved by an order of magnitude between 2002 and 2008, and we present the scientific and technological basis for another factor-of-two improvement in these economics. Wind energy is by far the most competitive renewable energy resource in many regions. The perceived challenge is getting wind energy from good sites to where and when it is needed, both for the transportation sector and for the power grid. Efficient conversion of wind energy and waste CO2 into clean, stable, liquid fuels – also called WindFuels – solves these problems. Annual WindFuels production per land area in good wind regions should exceed biofuels production density in fertile farming areas by a factor of five. First, water and renewable electrical power are fed into an electrolyzer, which produces the required hydrogen. Then waste CO2 (from coal power plants) and the renewable hydrogen are piped into a novel Reverse Water Gas Shift (RWGS) process, which permits practical reduction of CO2 to the CO needed at efficiencies approaching theoretical limits. The renewable CO and H2 are then fed into a novel Renewable Fischer-Tropsch Synthesis (RFTS) process. There they are converted into mostly mid-alcohols (ethanol, propanol, and butanol) and other valuable chemicals. These fuels may then be readily stored and distributed by conventional means – pipelines and tanker trucks. The electrolyzer also produces a huge amount of oxygen, which may be sold if market conditions warrant, or it may be utilized in novel processes to improve the plant efficiency. From basic thermodynamics, one readily calculates that the theoretical maximum chemical efficiency of synthesis of ethanol from H2 and CO2 is 80.1% without utilization of the excess heat released from the Fischer Tropsch Synthesis (FTS) reactor. If this excess heat is also converted in an ideal heat engine, the theoretical combined-cycle efficiency limit is ~90%. One advantage of ethanol may be appreciated by noting that its synthesis from H2+CO2 results in 1.5 molecules of water per carbon atom in the fuel, while the synthesis of alkanes or alkenes results in 2 molecules of waste water per carbon atom in the fuel. Previously, fossil-based FTS efficiencies for environmentally attractive fuels, such as ethanol and propanol, have usually been under 40%. The need for very efficient recycling of the large amounts of H2, CO, and CO2 in the byproducts from mid-alcohols FTS has possibly been the strongest argument against mid-alcohols FTS compared to gasoline, lubricants, and diesel. A novel plant design is presented, validated by many simulations, that permits order-of-magnitude reduction in energy penalties associated with the major separations in a fully recycled mid-alcohols plant compared to previously published designs. The example wind-driven RFTS plant size chosen for illustration and simulated in detail assumes 250 MW mean input electrical power. It achieves 72% FTS-plant higher heating value (HHV) efficiency in production of mid-alcohols and other products from H2 and recovered (waste) CO2, or about 60% net HHV efficiency when including the electrolyzer at expected near-term performance. At least eight separate, substantial innovations in the system design combine to permit this major advance in RFTS efficiency and cost effectiveness. It is worth pointing out that as recycle efficiency and byproduct utilization both approach 100%, which is the primary thrust in the RFTS optimization, catalyst selectivity and activity both become much less important. Catalysts never affect the thermodynamics – only the kinetics of the various pathways. Hence, further development of catalysts will have limited effect on system efficiency in a plant with 95% recycle efficiency, though of course it will influence profitability by changing the product mix.
Economic Analysis of Hydrogen Production from Wind: Preprint
The purpose of this analysis is to determine the cost of using wind energy to produce hydrogen for use as a transportation fuel. This analysis assumes that a market exists for 50,000 kg of hydrogen per day produced from wind at the wind site; only production costs to the front gate are included, no delivery or dispensing costs are included. Three different scenarios are examined: near term, which represents 2005 currently available technology; mid term, which represents technological improvements and price reductions in the next 5-10 years; and long term, which is representative of the best technology gains and price reductions surmised by industry at this point, and represents the next 10-25 years.
Low-temperature water–gas shift reaction over gold deposited on TiO2
Gold exhibits very high catalytic activities, comparable with that of a 
conventional Cu/ZnO/Al 
 2 
O 
 3 
 catalyst, for forward and 
reverse water–gas shift reactions when supported on titanium oxide 
by the deposition–precipitation method.