Publisher: Earthscan, UK Homepage: earthscan.co.uk/?tabid=101807

1. Energy and the New Reality, Volume 1:Energy Efficiency and the Demand for Energy ServicesChapter 5: Transportation Energy Use L. D. Danny Harveyharvey@geog.utoronto.ca This material is intended for use in lectures, presentations and as handouts to students, and is provided in Powerpoint format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see www.earthscan.co.uk for contact details. Publisher: Earthscan, UKHomepage: www.earthscan.co.uk/?tabid=101807

2. Transportation Energy Use, Outline • Trends in movement of people and goods • Energy use by different modes of transport • Role of urban form and infrastructure • Role of vehicle choice today • Technical options for reducing energy use in - Cars and light trucks - Inter-city rail and buses - Passenger aircraft - Freight transport

3. Technical options for cars & light trucks • Downsizing • Drive-train efficiency (thermal, mechanical, transmission) • Reduced loads (requiring the engine to do less work) • Hybrid electric vehicles (HEVs) • Plug-in hybrid electric vehicles (FCVs) • Fuel cell vehicles (FCVs)

4. Issue with fuel cell vehicles • Cost and performance of fuel cells • Constraints on supply of precious-metal catalysts • Difficulties with on-board processing of hydrocarbon fuels • Difficulties with on-board storage of hydrogen and development of H2 supply infrastructure

5. Figure 5.1 Proportion of different fuels usedfor world transportation Source: Gilbert and Pearl (2007, Transport Revolutions: Moving People and Freight Without Oil, Earthscan, London)

6. Figure 5.2a Breakdown of transportation energy use in OECD countries in 2005

7. Figure 5.2b Break down of transportation energy usein non-OECD countries in 2005

8. Figure 5.3a Variation in world passenger-km movement of people Source: Gilbert and Pearl (2007, Transport Revolutions: Moving People and Freight Without Oil, Earthscan, London)

9. Figure 5.3b Variation in world tonne-km movement of freight Source: Gilbert and Pearl (2007, Transport Revolutions: Moving People and Freight Without Oil, Earthscan, London)

10. Figure 5.4 Historical variation in world passenger-km transport by aircraft Source: Gilbert and Pearl (2007, Transport Revolutions: Moving People and Freight Without Oil, Earthscan, London)

11. Figure 5.5 Growth in the number of passenger and commercial vehicles worldwide

12. Figure 5.6 Historical variation in the number of cars per 1000 people Source: Gilbert and Pearl (2007, Transport Revolutions: Moving People and Freight Without Oil, Earthscan, London)

13. Figure 5.7 Breakdown of total travel in USA Source: Gilbert and Pearl (2007, Transport Revolutions: Moving People and Freight Without Oil, Earthscan, London)

14. From Table 5.1, energy intensities of different modes of travel within cities • Gas guzzling car (20 litres/100 km), one person: 6.5 MJ/person-km (7.8 MJ/p-km primary energy) • Energy efficient car (8 litres/100 km), 4 persons: 0.65 MJ/person-km (0.78 MJ/p-km primary energy) • Diesel bus, typical US loading: 1-2 MJ/person-km • Light rail: 0.8 MJ/person-km of electricity, 2 MJ/person-km primary energy • Heavy rail: 0.4 MJ/person-km electricity, 1.0 MJ/person-km primary energy • Walking: 0.13 MJ/person-km food energy • Bicycling: 0.1 MJ/person-km food energy

15. From Table 5.3, primary-energy intensities of different modes of travel between cities • Gas guzzling car (12 litres/100 km, 4 people) 1.16 MJ/person-km • Fuel efficient car (6 litres/100 km, 4 people) 0.58 MJ/person-km • Intercity bus: 0.28 MJ/person-km • Diesel train: 0.2-0.5 MJ/person-km • High speed electric train: 0.2-0.4 MJ/person-km • Air: 0.6-1.5 MJ/person-km

16. From Table 5.4: The complete energy picture for transportation involves • On-site fuel or electricity use • Upstream energy use in producing and supplying the fuel or electricity (this and on-site energy give primary energy use for the operation of the vehicle, which is what is given in the preceding two slides) • The energy used to make the vehicle (embodied energy), averaged over the total distance travelled during the lifetime of the vehicle • The energy used to make and maintain the infrastructure for the vehicles (roads, rail lines, airports), averaged over the total distance travelled during the lifetime of the vehicle

17. Some prominent results from Table 5.4: • Vehicle+infrastructure embodied energy for urban light and heavy rail, interurban car and interurban rail is about ½ the direct+upstream operating energy use • Embodied energy for short air travel (trips of 390 km) exceeds the operating energy • For international air travel (average distance of 7500 km), the aircraft embodied energy is important (about 40% of the operating energy)

18. Figure 5.8 Relationship between private transportationenergy use and urban density Source: Newman and Kenworthy (1999, Sustainability and Cities: Overcoming Automobile Dependence, Island Press, Washington)

19. Compact urban form with different land uses (residential, retail, offices, schools and daycare centres, medical) intermixed reduces transportation energy requirements by: • Reducing the distances that need to be travelled • Making is more practical and economical to serve the reduced travel demand with high-quality (i.e., rail-based) public transit • Increasing the viability of walking and bicycling Once people start using transit, there is a further reduction in travel demand (in the distances travelled) because people start planning their trips to be more efficient (i.e., combining errands in one trip)

20. Bicycling+walking share (in terms of number of trips taken) in selected cities in 2001: • Amsterdam, 52% • Copenhagen, 39% • Hong Kong, 38% (another 46% by public transit) • Sao Paulo, 37% • Berlin, 36% • New York, 9% • Atlanta, 0%

21. Importance of Choice of Car/Truck (fuel use is given for city driving) • Pickup truck, 16 to 26 litres/100 km • SUV, 8 to 26 litres/100 km • Minivan, 11 to 21 litres/100 km • Large car, 11 to 26 litres/ 100 km • Mid-size car, 9 to 24 liters/100 km • Subcompact car, 8 to 21 litres/100 km • Subcompact hybrid, 6 litres/100 km • 2-seater, 7 to 29 liters/100 km

22. Figure 5.9a Mix of vehicles purchased in the US in 1975 Source: Friedman et al (2001, Drilling in Detroit: Tapping Automaker Ingenuity to Build Safe and Efficient Automobile,Union of Concerned Scientists)

23. Figure 5.9b Mix of vehicle purchased in the US in 2000 Source: Friedman et al (2001, Drilling in Detroit: Tapping Automaker Ingenuity to Build Safe and Efficient Automobile,Union of Concerned Scientists)

24. Figure 5.10 Risks posed by different cars Source: Ross and Wenzel (2002, An Analysis of Traffic Deaths by Vehicle Type and Model, ACEEE)

25. Types of automobiles • Spark ignition (SI) – runs on gasoline, with power output reduced by reducing the flow of fuel and throttling (partially blocking) the airflow, causing a major loss of efficiency at part load (which is the typical driving condition) • Compression ignition (CI) – runs on diesel fuel, which is ignited by compression without the need for spark plugs. More efficient than SI engines due to absence of throttling, high compression ratio and lean fuel mixture (high air:fuel ratio) • Internal combustion engine (ICE) – refers to engines where combustion occurs in cylinders. Both SI and CI engines are ICEs

26. Pollution controls • SI engines use 3-way catalytic converters to oxidize (add oxygen to) CO and hydrocarbons in the exhaust while reducing (removing oxygen from) NOx • This requires a stoichiometric air:fuel ratio • Until recently, 3-way catalytic converters could not reduce NOx in diesel exhaust because of the excess oxygen • Recent advances that entail the use of ammonia have solved this problem • Much stricter (and comparable) emission standards can be expected for both gasoline and diesel vehicles in the future.

27. However .... • Stricter pollution controls require ultra-low S concentrations in the fuel (~ 10 ppm, vs 10-250 today in gasoline and 10-500 ppm today in diesel fuel) • Achieving the very low S content in fuels increases refinery energy use by about 1.5%, and the stricter pollution controls for diesel trucks (at least) would increase fuel use by 4-10%

28. Figure 5.11a Fuel Economy Trend Source: Zachariadis, T. (2006, Energy Policy 34, 1773–1785, http://www.sciencedirect.com/science/journal/03014215)

29. Figure 5.11b Car/light truck fuel economy trend Source: Zachariadis, T. (2006, Energy Policy 34, 1773–1785, http://www.sciencedirect.com/science/journal/03014215)

30. Figure 5.12a Trends in automobile mass Source: Zachariadis, T. (2006, Energy Policy 34, 1773–1785, http://www.sciencedirect.com/science/journal/03014215)

31. Figure 5.12b Trends in automobile acceleration and top speed Source: Zachariadis, T. (2006, Energy Policy 34, 1773–1785, http://www.sciencedirect.com/science/journal/03014215)

32. Figure 5.12c Trends in engine power and power/displacement Source: Zachariadis, T. (2006, Energy Policy 34, 1773–1785, http://www.sciencedirect.com/science/journal/03014215)

33. Figure 5.13 Auto Loads vs. Speed

34. Figure 5.14 Fuel Use vs Speed

35. Figs 5.15-5.16 Energy flow in a typical present day car (8.9 litres/100 km, 26.4 mpg) (left) and advanced vehicle (4.0 litres/100 km, 58.4 mpg) (right)

36. Options to Improve the Fuel Economy of Cars and Light Trucks, Part 1 • Improve engine thermal efficiency (fraction of fuel energy supplied to the pistons, through combustion) • Improve engine mechanical efficiency (fraction of piston energy transferred to the drive shaft) • Improve the transmission efficiency (fraction of drive shaft energy transferred to the wheels)

37. Methods to improve engine thermal efficiency • Leaner fuel:air mixture (but worsens NOx emissions) • Variable compression ratio (currently fixed) – saves 10-15% if combined with supercharged downsized engine • Direct injection gasoline – fuel sprayed directly into cylinders at high pressure – saves 4-6% • Variable stroke (switch between 2-stroke operation during acceleration and 4-stroke operation at high speeds) – saves 25% • Resultant fuel use would be 0.85 x 0.95 x 0.75 = 0.60, a savings of 40% (best case)

38. Methods to improve engine mechanical efficiency • Aggressive transmission management – running at optimal gear ratio at all times, which makes the engine operate at the torque-rpm combination that maximizes the engine efficiency for any given driving condition. • Smaller engines (most of the time the engine operates at a small fraction of its peak power). 10% smaller saves 6.6% in fuel because the engine on average will operate more efficiently • Variable valve control instead of throttling of air flow in gasoline engines – saves up to 10% • Reduced friction through better lubricants and other measures – 1-5% savings • Automatic idle-off when stopped – saves 1-2%

39. Increasing the transmission efficiency • As noted above, the way in which the transmission is operated affects the engine mechanical efficiency • The transmission itself is another source of energy loss, which can be reduced • Typical transmission efficiencies today: - automatic, 70-80% - manual, 94% • Future automatic: 88% with continuously variable transmission • Energy use if we go from 70% to 88% is multiplied by 70/88 = 0.795, a savings of about 20%

40. Combining the savings from different steps: • Certainly do not add the savings, because the savings from each successive step applies only to the remaining energy use, not to the original energy use • Instead, multiply the individual factors representing the reduction in fuel use in each step • Thus, if improved engine thermal efficiency, engine mechanical efficiency and improved transmission efficiency save 40%, 10% and 20%, respectively, then multiply 0.6 x 0.9 x 0.8 to get the overall fuel requirement • In the above example, this would be 0.432 – a savings of 56.8% • The factor of 0.432 would be multiplied by a further factor to represent the effect of reduced loads, giving an even larger potential savings

41. Options to Improve the Fuel Economy of Cars and Light Trucks, Part 2 • Reduced tire rolling resistance through higher-pressure tires • Reduced aerodynamic resistance through changes in car shape • Reduced vehicle weight (affects energy use during acceleration and when climbing hills) • Reduced vehicle accessory loads

42. Comparing Figures 5.15 and 5.16 • The energy flow to the wheels increases from 14.8% to 22.7% of the fuel input • Thus, for the same energy flow, we need only 14.8/22.7 = 0.652 as much fuel (a savings of 34.8%) • The loads on the wheels (due to reduced rolling and aerodynamic resistance and reduced vehicle weight) drop from 429.9 kJ/km to 298.0 kJ/km, so the fuel requirement from this alone would be multiplied by 298.0/429.9 = 0.693 (a savings of 30.7%) • The overall fuel requirement is multiplied by 0.652 x 0.693 = 0.452 (a savings of 54.8%, which is < 34.8+30.7) • Cross-check: the ratio of fuel inputs at the tops of the two figures is 1302/2882 = 0.452

43. Alternative vehicle drive trains • Hybrid gasoline-electric or diesel-electric vehicles (HEVs) • Plug-in hybrid electric vehicles (PHEVs) • All-electric or battery electric vehicles (BEVs) • Fuel cell vehicles (FCVs)

44. Hybrid electric vehicles • Use the engine to supply average power requirements and to recharge a battery, with the battery used to meet peak requirements (acceleration, hill climbing) • This allows downsizing of the engine, thereby reducing friction losses • It also allows the engine to operate closer to the torque-rpm combination that maximizes its mechanical efficiency

45. Other energy savings in HEVs occur through: • Regenerative braking – using vehicle kinetic energy to recharge the battery • Elimination of idling when stopped • Shifting power steering and other accessories to more efficient electric operation • However, the Toyota Prius is not much more fuel-efficient than a 1993 Honda Civic – because the technology has largely gone into giving better acceleration rather than improving fuel economy

46. Figure 5.17 Gasoline-battery hybrid vehicle (parallel drive-train option)

47. PHEVs • The idea here is to recharge the battery from the AC power grid (i.e., by plugging it in when parked) and using the battery until the battery energy drops, then switching to the gasoline (or diesel) engine • This requires batteries with greater storage capacity than in HEVs, giving 40-60 km driving range on the battery • Since most trips are shorter than this, a large portion of total distance travelled could be shifted to electricity in this way

48. PHEVs (continued) • The key issues are the cost of the battery, the mass of the battery (cars with heavier batteries will need more energy for acceleration and climbing hills), the amount of energy stored (usually represent in Wh), which determines the driving range, and the peak power output from the battery (W), which determines how fast the vehicle can accelerate • The key battery performance parameters are thus: specific energy, Wh/kg, and specific power, W/kg

49. Figure 5.18 Specific power and specific energy of different batteries

50. Figure 5.19 Battery cost vs battery power:energy ratio 60