In general, public transportation has lower carbon emission intensity than private Public Transportation and Efficiency ▪ Despite incentives for carpool lanes and toll breaks over recent years, single occupancy vehicles remain the most popular mode of transportation USA Relationship between prices of oil and gasoline (USA) USA Peak Oil USA Crude Oil Production and Importation, 1910-2012 World Oil Production + Population Bumpy Plateau of Peak Oil? Peak Oil ▪ Once global peak oil has passed, half of oil ever available will have been extracted and consumed ▪ Production will then enter decline, and cost will increase ▪ Another reason to transition to alternative fuels for transportation Alternative Fuels for Transportation ▪ The USA Department of Energy has set a “30 by 30” goal – 30% of gasoline use from alternative fuels by 2030 ▪ Alternative Energy Sources for Transportation – Natural Gas – Hydrogen – Electric – Hybrid – Biofuels (Biodiesel, Ethanol) Alternative Fuels – Natural Gas ▪ Extracted from oil wells, coal beds, natural gas fields, and landfills – Made of hydrocarbons and releases CO2 (like other fossil fuels) ▪ Compared to gasoline, considered ‘clean burning’ for transportation – Produces 80-90% fewer aerosols – Emits 12% less greenhouse gases ▪ Low density presents transport challenges – Many USA pipelines near capacity Natural Gas Buses in LA 2012 Honda Civic (Natural Gas) Alternative Fuels – Natural Gas ▪ The three countries with the highest number of vehicles powered by natural gas in 2010 were Pakistan, Iran, and Argentina ▪ In the USA, 110,000 vehicles were powered by natural gas (1 in every 2500) Alternative Fuels – Natural Gas ▪ Number of natural gas vehicles has increased greatly for certain regions in the past 15 years Alternative Fuels – Natural Gas ▪ Represents cleaner alternative to petroleum, but still a non-renewable resource Alternative Fuels – Hydrogen ▪ 2003 State of the Union – “A simple chemical reaction between hydrogen and oxygen generates energy, which can be used to power a car producing only water, not exhaust fumes. With new national commitment, our scientists and engineers will overcome obstacles by taking these cars from the laboratory to the showroom so that the first car driven by a child born today could be powered by hydrogen, and be pollution free.” ▪ Technology has not progressed on this optimistic timeline Alternative Fuels – Hydrogen ▪ Storage – Hydrogen has the lowest energy content per unit volume of any fuel ▪ Need to store a lot in the vehicle which presents technical challenges ▪ Cost – Fuel cells require extremely expensive compounds ▪ Many components cost more than their weight in gold – $30,000 for platinum Alternative Fuels – Hydrogen ▪ Reliability – Fuel cells are extremely sensitive to external temperature and moisture ▪ Production – Hydrogen is not an energy source, but an energy carrier – Earth has no recoverable deposits of hydrogen – Over 95% of hydrogen generated today derives from fossil fuels ▪ Other means of production comprise an area of active research Toyota Mirai Alternative Fuels – Electric Vehicles ▪ Electric motors that require only recharging (not refueling) ▪ Challenges – Limited distance, speed – High recharge times, cost – Carbon footprint of batteries ▪ Benefits – Don’t emit greenhouse gases directly – Don’t release aerosols – Save consumer money on gasoline Prices and Ranges (2018) Tesla Model S Tesla Model 3 (from $35,000) Elon Musk and Tesla Roadster 2 Chevrolet Bolt: Plug-In Electric Ford Focus (Electric) 65 Hybrid Electric Vehicles ▪ Connect both gasoline powered engine and electric motor to the wheels – Gasoline engine charges battery – Gasoline engine shuts down when the vehicle stops – Use regenerative braking ▪ Hybrids improve fuel efficiencies by about 30% in city driving Toyota Prius at Mount Hamilton (November 2019) Chevrolet Volt: Plug-In Hybrid Biofuels ▪ Biofuels are produced from living materials ▪ Most modern engines have flexibility to combust mixtures of biofuels ▪ In theory, biofuels should produce no net greenhouse gases for same reason that human breathing produces no net greenhouse gases Ethanol ▪ Can be produced from sugarcane or maíz ▪ Ethanol has about a third less energy content per volume compared to gasoline ▪ E85 (85% ethanol, 15% gasoline) is less expensive than gasoline ▪ E85 has lower fuel efficiency than gasoline, helping to negate lower CO2 emissions upon combustion of same volume Biofuels ▪ In practice, biofuels have a large carbon footprint – Production ▪ Machinery, fertilizers, pesticides, and water – Transport ▪ Plant biomass has a low energy density – Processing ▪ Conversion from biomass to ethanol takes energy ▪ Diversion of food to fuels – Raises food prices Ethanol Stations in the USA Nuclear Powered Car? ▪ Benefits – High energy per volume ▪ Can travel far without needing to refuel ▪ Major challenges – Radiation exposure – Weight

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