Energy and the New Reality Volume 1 Energy

Energy and the New Reality, Volume 1: Energy Efficiency and the Demand for Energy Services Chapter 5: Transportation Energy Use L. D. Danny Harvey harvey@geog. utoronto. ca Publisher: Earthscan, UK Homepage: www. earthscan. co. uk/? tabid=101807 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.

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 - Light duty vehicles (LDVs: cars, SUVs (sport utility vehicles) and light trucks) - Inter-city rail and buses - Passenger aircraft - Freight transport

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

Figure 5. 2 a Breakdown of transportation energy use (overwhelming oil products) in OECD countries in 2005

Figure 5. 2 b Break down of transportation energy use (overwhelmingly oil products) in non-OECD countries in 2005

Figure 5. 3 a Variation in world passenger-km movement of people Source: Gilbert and Pearl (2007, Transport Revolutions: Moving People and Freight Without Oil , Earthscan, London)

Figure 5. 3 b Variation in world tonne-km movement of freight Source: Gilbert and Pearl (2007, Transport Revolutions: Moving People and Freight Without Oil, Earthscan, London)

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)

Figure 5. 5 Growth in the number of passenger and commercial vehicles worldwide (close of 1 billion by now)

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)

Reminder (from Chapter 1) • Secondary energy is the energy at the point of use (i. e. , electricity , gasoline) • Primary energy is the energy as it is found in nature, used to produce secondary energy (i. e. , coal used to generate electricity, crude oil refined into gasoline or diesel fuel) • Typically: 1. 25 units oil produces 1. 0 units gasoline or diesel fuel • 2. 5 -3. 0 units of coal or natural gas produces 1. 0 units of electricity (40 -33% efficiency)

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. 0 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

From Table 5. 3, primary-energy intensities of different modes of travel between cities • Gas guzzling car (12 litres/100 km, 1 person) 4. 64 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

From Table 5. 4: The complete energy picture for transportation involves • On-site fuel or electricity use (operating energy) • 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) per km, divided by the number of vehicles using the infrastructure over its lifetime (to get MJ/vehicle-km) (this is a different kind of embodied energy)

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)

Photo taken near Villabassa, northern Italy

Role of urban form and good urban planning

Figure 5. 8 Relationship between private transportation energy use and urban density Source: Newman and Kenworthy (1999, Sustainability and Cities: Overcoming Automobile Dependence, Island Press, Washington)

Newark, Ohio Source: Visualizing Density (2007)

Ontario somewhere? Houses are closer together but the “wormwood” street pattern and lack of intermixing of different land uses hardwires high transport energy use Source: www. whichmortgage. ca/article/ottawa-writer-on-the-scourge-of-sprawl-181614. aspx

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 it 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)

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%

Aside: New policies announced by the Ontario government in May 2016 and under review until Sept 2016 • Requiring “pre-zoning” along transit corridors to guarantee dense development if cities want to get future transit funding. • Ensuring that at least 60 per cent of all new residential developments in municipalities are in existing “built-up” areas. • Substantially increasing employment density so greenfield spaces within cities can’t be eaten up by things such as sprawling warehouses. • Requiring municipalities to provide “transparent” calculations to show they are properly using land to meet smart growth targets. Source: www. thestar. com/news/gta/2016/05/10/ontario-setting-new-rules-to-end-era-of-suburban-sprawl-across-gta. html

Role of choice of automobile among the existing fleets, and recent trends

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

Figure 5. 10 Risks posed by different cars Source: Ross and Wenzel (2002, An Analysis of Traffic Deaths by Vehicle Type and Model, ACEEE)

Figure 5. 11 b Car/light truck fuel economy trend Source: Zachariadis, T. (2006, Energy Policy 34, 1773– 1785, http: //www. sciencedirect. com/science/journal/03014215)

Figure 5. 12 a Trends in automobile mass Source: Zachariadis, T. (2006, Energy Policy 34, 1773– 1785, http: //www. sciencedirect. com/science/journal/03014215)

Figure 5. 12 b Trends in automobile acceleration and top speed Source: Zachariadis, T. (2006, Energy Policy 34, 1773– 1785, http: //www. sciencedirect. com/science/journal/03014215)

Figure 5. 12 c Trends in engine power and power/displacement Source: Zachariadis, T. (2006, Energy Policy 34, 1773– 1785, http: //www. sciencedirect. com/science/journal/03014215)

Figure 5. 14 Fuel Use vs Speed

Physics of Automobile Efficiency

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

An automobile engine does work of various kinds – the work done is the output of the engine, and the fuel used is the input. The basic relationship for any machine is: Work Done (output) = Efficiency x Fuel Input Rearranging the above, Fuel Use = Work Done / Efficiency There are 3 efficiencies that need to be multiplied together to get the overall drive train efficiency, and 4 kinds of work that need to be added to get the total work requirement.

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) Fuel Input x Engine Thermal Efficiency x Engine Mechanical Efficiency - Auxiliaries x. Transmission Efficiency = 3 loads

Options to Improve the Fuel Economy of Cars and Light Trucks, Part 1 – Increase all the efficiencies in the drive-train chain • 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)

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)

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%

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 – now becoming commonplace • Energy use if we go from 70% to 88% is multiplied by 70/88 = 0. 795, a savings of about 20%

Combining the savings from different steps in the drive train: • 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%

To see this, note that overall efficiency = wheel energy/fuel energy Thermal efficiency = pistons/fuel Mechanical efficiency = drive shaft/pistons Transmission efficiency = wheels/drive shaft and so when you multiply the 3 efficiencies, everything cancels out except that you end up with wheels/fuel, which is the overall efficiency

Options to Improve the Fuel Economy of Cars and Light Trucks, Part 2 – Reduce Loads • Reduced tire rolling resistance through higherpressure 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

Comparing Figures 5. 15 and 5. 16 • The energy flow to the wheels increases from 14. 8% to 22. 7% of the fuel input (due to an improved efficiency chain) – so the overall efficiency is multiplied by 1. 534 • The loads on the wheels (due to reduced rolling and aerodynamic resistance and reduced vehicle weight) drop from 429. 9 k. J/km to 298. 0 k. J/km, so the required work that need to be supplied to the wheels is multiplied by 0. 693 • As fuel requirement = Load/Efficiency, new fuel requirement relative to the old one will be 0. 693/1. 534 = 0. 451 • That is, the fuel requirement is reduced by 55%

Future Prospects for LDVs (light duty vehicles – cars, SUVs, pickup trucks) • More efficient conventional vehicles • Alternative drive-trains

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)

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

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

Figure 5. 17 Gasoline-battery hybrid electric vehicle (HEV) (parallel drive-train option)

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

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

Figure 5. 18 Specific power and specific energy of different batteries

Figure 5. 19 Battery cost vs battery power: energy ratio 60

Figure 5. 21 Gasoline savings with PHEVs as a function of electric driving range for US driving patterns

Fuel Cell Vehicles • A fuel cell is an electrochemical device that produces electricity, water and heat • It requires a hydrogen-rich fuel • There had been some effort to develop systems to convert gasoline on-board into a hydrogenrich fuel that in turn would be fed to the fuel cell, but these efforts have largely been abandoned

• Instead, pure hydrogen fuel would be stored on board the vehicle • The major issues are: - How to store the hydrogen - How to build up a hydrogen-distribution infrastructure - What energy sources would be used to make hydrogen - Cost of fuel cells and of hydrogen fuel

Attractions of hydrogen FCVs • Zero pollution emissions • Much lower noise • The hydrogen could be produced by electrolysis (splitting) of water using electricity supplied from renewable wind, solar or hydro sources of energy • Thus, zero greenhouse gas emissions and sustainable energy supply

Options for Onboard Storage of H 2 • As a gas compressed to 700 atm pressure – over 3 times the volume and 1. 4 times the weight of gasoline+tank in a gasoline-powered vehicle with the same driving range - energy equiv to 10% that of the stored hydrogen would be needed for compression • As liquid hydrogen, at 20 K (= -253ºC) – just over 2 times the volume but half the weight of the gasoline+tank - energy equiv to 1/3 that of the stored hydrogen would be needed for liquefaction (possibly reduced to 20% in the future) • As a metal hydride – almost 4 times the weight but only 80% of the volume of gasoline+tank. More mining and processing of metals needed.

Figure 5. 25 Ballard 85 -k. W fuel cell for automotive applications Source: Little (2000, Cost Analysis of Fuel Cell System for Transportation, Baseline System Cost Estimate, Task 1 and 2 Final Report to Department of Energy, Cambridge)

Figure 5. 27 Fuel cell-battery hybrid vehicle

Figure 5. 28 Efficiency of fuel cell vs output Box 5. 1, at the end of this file, contains Figures 5. 29 and 5. 30 Source: Kromer and Heywood (2007, Electric Powertrains: Opportunities and Challenges in the U. S. Light-Duty Vehicle Fleet, Laboratory for Energy and the Environment, MIT)

Thus, • A hydrogen FCV would operate at a typical efficiency of ~ 60%, which is more than three times the efficiency (17%) of a typical ICE gasoline-engine vehicle today • This in turn reduces the amount of energy (as H 2) that needs to be stored on the vehicle for a given driving range by over a factor of 3 • This in turn is critical because any system of onboard hydrogen storage will be bulky and/or heavy in relation to the amount of energy stored • The high efficiency also greatly reduces the amount of wind or solar power that would need to be installed in order to produce enough hydrogen to replace petroleum for transportation

Problems • Fuel cells suitable for use in cars need to be able to operate at low temperature (120ºC) • Low-temperature fuel cells require precious-metal catalysts (Pt and ruthenium) in order to operate (these catalysts are also needed in 3 -way catalytic converters, but would not be needed for such in H 2 FCVs) • Supplies of Pt are quite limited – the availability of Pt could be a significant constraint on the long-term viability of H 2 FCVs

Figure 5. 31 Distribution of Exploitable Pt Resources

Rough scenario calculation: • A vehicle fleet reaching 5 billion (which would result from a human population of 10 billion with European levels of car ownership) and consisting entirely of FCVs would have a cumulative Pt demand by 2100 equal to the upper limit of the estimated amount of Pt that could be mined • This leaves no room for other uses of Pt (such as in jewelry and electronics)

4 ways of using solar-energy to power cars • Using solar electricity to charge batteries • Using solar electricity to make H 2 for use in a fuel cell • Using solar energy to grow biomass that is converted to methanol and used in a fuel cell • Using solar energy to grow biomass that is converted into ethanol and used in an ICE

Steps, solar energy to battery • PV modules, 15% efficiency • DC to AC conversion, 85% • Transmission of electricity, 96% (say) • Battery charging, 95% • Drive train (motor, transmission), 87% Overall sunlight to wheels energy transfer: 10. 1%

Steps, solar energy to H 2 Fuel cell • PV modules, 15% efficiency • PV to electrolyzer coupling, 85% • Production of hydrogen by electrolysis and compression to 30 atm, 80% • Transmission 1000 km at 30 atm pressure, 98% • Compression from 30 to 700 atm pressure, 90% • Fuel cell (generates electricity), 50% or better • Drive train (motor, transmission), 87% Overall sunlight to wheels energy transfer: 3. 9%

Steps, solar energy to methanol to fuel cell (methanol is another candidate as a fuel for fuel cells) • • Photosynthesis, 1% efficiency Biomass to methanol, 67% Transport of methanal, 98% (say) Fuel cell to produce electricity, 45% (less than using H 2) • Drive train (motor, transmission), 87% Overall sunlight to wheels energy transfer: 0. 26%

Steps, solar energy to ethanol, used in an advanced ICE • Photosynthesis, 1% efficiency • Biomass to ethanol, 67% • Transport, 98% (say) • ICE, 20% • Drive train, 87% Overall sunlight to wheels energy transfer: 0. 11%

Conclusion: • Direct use of renewably-based electricity to recharge batteries makes far better use of the renewable electricity than using it to make H 2 to for use in a fuel cell (extra steps mean extra losses) • The land area required to convert sunlight to H 2 and drive a given distance is ~ 20 times less than growing biomass to make methanol for use in a fuel cell, or ~ 40 times less than growing biomass to make ethanol • This is largely because the efficiency of PV modules (~15 % or more) is vastly greater than the efficiency of photosynthesis (~ 1%)

Thus, the best bet seems to move to plug-in hybrid vehicles that are recharged with solar- or wind-generated electricity, with maybe a small amount of hydrogen as a range extender in order to eventually get completely off of fossil fuels, unless fully electric vehicles with adequate range can be developed Liquid biofuels would be a distant second best as a range extender, but might be needed if problems with H 2 cannot be resolved Swapping the battery for a freshly charged battery every 100 -200 km might be another solution In any case, the underlying vehicle should be as efficient as possible to minimize the electricity and/or hydrogen or biofuel requirements.

Future Prospects

Figure 5. 34 Fuel-efficient cars

Updated Information: 2011 Argonne National Lab study, fuel and electricity energy intensity for compact cars

Updated information: Impact of vehicle choice from the 2011 Argonne National Lab study

Key points from the previous 2 slides: • An advanced HEV – running solely on gasoline – could be made about 3 times more efficient than a conventional vehicle today (this could come about by reducing loads by 50% and increasing drive train efficiency by 50%, as 0. 5/1. 5=0. 33) • The PHEV when running on fuel requires a bit more than an HEV – because it has larger and hence heavier batteries • The energy required to drive a given distance using electricity from the battery is about one third of that using fuel – so we are reducing the energy requirements per km by about a factor of nine when driving off of the battery, compared to a conventional vehicle today • If 2/3 of the driving of a vehicle that is 3 x more efficient using fuel is shifted to grid electricity, the fuel requirement is also reduced by a factor of nine • Switching from today’s pickup truck to an advanced mid-size HEV reduces the fuel requirements by a factor of 5 - solely using gasoline as the energy source.

Recent Electric Vehicle (PHEV and BEV) Developments

From a 2015 paper by GM engineers, comparing the 1 stgeneration Chevy-Volt (a GM product) with 3 anonymous PHEVs Source: http: //www. hybridcars. com/study-shows-chevy-volt-can-burn-less-gas-than-any-other-phev/

Updated version (2015) of an earlier slide Source: http: //www. hybridcars. com/study-shows-chevy-volt-can-burn-less-gas-than-any-other-phev/

EPA label: Note that the “effective” mpg on electricity is about 3 times that for gasoline – because a MJ of electrical energy in the battery can be used 3 times more efficiently than a MJ of gasoline energy Source: http: //www. hybridcars. com/study-shows-chevy-volt-can-burn-less-gas-than-any-other-phev/

Data for recent PHEVs – there is an inconsistency – where is it? 2016 Hyundai Sonata 2016 Ford Fusion Energi 2014 Honda Accord Engine (k. W) 115 105 Motor (k. W) 50 88 124 Battery (k. Wh) 9. 8 7. 6 6. 7 Max EV speed (kph) 121 129 105 All-electric range (km) 39 34 21 Total range (km) 965 885 917 Electricity use (MJ/km) 1. 10 1. 16 0. 89 Electricity use (k. Wh/km) 0. 31 0. 32 0. 25 Fuel use (MJ/km) 2. 55 2. 69 2. 22 Charge rate (k. W) 3. 3 6. 6 Charge time (hrs) ~ 3 hr ~ 2. 5 hr ~ 1 hr

Falling costs of battery packs for electric vehicles X X=target announced by Tesla in 2016 Source: Nykvist and Nilsson (2015, Nature Climate Change 5: 329 -332)

On Battery-Electric Vehicles http: //www. youtube. com/watch? v=t 6 Vzhl 1 ht o. M&list=PLa. SHX 1 Y 3 k. E 0 yq. Rjn. Ox. Ip 9 f. BEm. Zbkb 0 q. U (parody of “Surrey with the Fringe on Top” from the musical “Oklahoma”, http: //www. youtube. com/watch? v=Ss 1 CXo 8 QMi 8)

A scenario for the future • Accounts for typical projections of population and economic growth in 10 different world regions, with corresponding increases in per capita distances travelled • Starts from existing vehicle fleets and usage in each world region • Assumes achievement of the Argonne Lab fuel intensities (MJ/km) for new vehicles by 2035 (slow) or 2045 (fast) with a further reduction of 0. 5%/yr thereafter, in recognition of the fact that the Argonne study was conservative in some respects • Accounts for normal rates of stock turnover (vehicle replacement)

The scenario also assumes • A transition from conventional vehicles to some combination of PHEVs and BEVs by 2100 • A transition from fossil fuels to either biofuels or H 2 for the fuel portion of PHEVs by 2100 – So, by design, the scenarios achieve zero oil use and hence zero CO 2 emissions by 2100, but we can look at what happens during the transition, the relative importance of different factors, and the implications in terms of land requirements for biofuels or renewable electricity requirements to produce C-free H 2

Scenario for changing share in the total vehicle stock of different LDV drivetrains (derived from a scenario for changing market shares of new vehicles) Source: Harvey (2014, Energy Policy 54: 87 -103)

Hypothetical slow (solid lines) and fast (dashed line) transitions to biofuels or hydrogen for the fuel (non-battery) component of transportation 1. 0 0. 9 0. 8 Market Share 0. 7 0. 6 Fossil fuels 0. 5 Biomass in biomass-intensive 0. 4 Hydrogen in H 2 -intensive 0. 3 0. 2 0. 1 0. 0 2000 2020 2040 2060 Year Source: Harvey (2014, Energy Policy 54: 87 -103) 2080 2100

Global fossil fuel use by LDVs, Low GDP scenario, Fast Transition Source: Harvey (2014, Energy Policy 54: 87 -103)

Reductions in global biofuel use by LDVs, Low GDP scenario, Fast transition Source: Harvey (2014, Energy Policy 54: 87 -103)

Inter-City Rail Transport • French TGV (Train à grand vitesse) • German ICE (Inter-city express) • Japanese Shinkansen

Recall: • Energy use to move people by cars is ~ 2. 5 MJ/person km with 1 person per car, and projected to be ~ 1 MJ/person-km with advanced future vehicles (~ 0. 25 MJ/person-km if you pack 4 people into the car) • The energy required in today’s high speed trains is ~ 0. 08 to 0. 15 MJ/person-km

Figure 5. 37 Energy intensity for successive generations of the German Intercity Express (ICE) high-speed trains Source: Kemp (2007, T 618 – Traction Energy Metrics, Lancaster University, Lancaster, www. rssb. co. uk)

Figure 5. 38 Shinkansen energy use

Caveats: • The savings are not quite as large as they appear to be, because high speed trains use electricity which will typically be generated at an efficiency of only 35 -40% • So, divide the (electrical) energy use by the train by (0. 35 to 0. 4 times the transmission and transformer efficiencies) to get fuel use at the powerplant that generates the electricity • Compare this with the amount of crude oil needed to produce the gasoline energy that is saved when people switch to trains. This will be the saved gasoline divided by the efficiency in making gasoline from oil, about 0. 85

Caveats (continued): • The energy requirements for high speed trains increase rapidly with increasing speed beyond about 300 km per hour • The absolute time savings over a given distance gets smaller and smaller for each additional increment of speed • Faster trains increase total transportation demand – so some of the passengers on the train are people who would not have travelled at all • Thus, careful market analysis is required to determine if the introduction of high-speed trains really does save energy

Aircraft Energy Use

Major types of aircraft • Turbojet • Turbo fan (popularly called “jets”) • Turbo prop All three have, as their core, a gas turbine (the gas turbines now used to generate electricity using natural gas were derived from aircraft turbines developed for the military)

In a true “jet”, all of the air thrown behind the aircraft passes through the turbine, where combustion of fuel occurs. This is found only in military fighter jets

In commercial “jet” aircraft, most of the air thrown behind the jet bypasses the turbine, as it is accelerated by a big fan attached to the turbine (this is what you see when you look at a the engine of a commercial jet)

A third option is for the turbine to drive a propeller that is in front of the turbine

The performance of an aircraft is represented by the specific air range, which is the distance that can be travelled per MJ of fuel energy used. It depends on 3 factors: • The amount of thrust produced by the engines per kg of fuel used • The aircraft drag for a given velocity • The aircraft weight

The thrust generated by the engine is equal to the product of mass x velocity of the air thrown behind the engine Doubling the mass of air thrown and cutting its speed in half gives the same thrust, but much less kinetic energy (which varies with v 2) needs to be added in this case Thus, the engine needs to do less work while producing the same thrust

This is why turbofan aircraft were developed • The larger the bypass ratio, the greater the amount of air that is thrown behind the engine, but the less it needs to be accelerated • This tends to make the engine more effective • However, this requires a larger engine casing, which increases the drag and weight • Thus, there is an optimal bypass ratio, which is where we are now – not much further improvement can be expected

Figure 5. 40 a Trends in thrust specific fuel consumption (fuel consumption per unit of thrust generated – smaller is better) Source: Babikian et al (2002, Journal of Air Transport Management 8, 389– 400, http: //www. sciencedirect. com/science/journal/09696997)

Figure 5. 40 b Trend in lift/drag ratio (larger is better) Source: Babikian et al (2002, Journal of Air Transport Management 8, 389– 400, http: //www. sciencedirect. com/science/journal/09696997)

Figure 5. 40 c Trend in ratio of empty weight to maximum allowed take-off weight (smaller is better). Source: Babikian et al (2002, Journal of Air Transport Management 8, 389– 400, http: //www. sciencedirect. com/science/journal/09696997)

Observations from the previous figures: • The big improvement has been in thrust specific fuel consumption (TSFC) – decreasing by about 50% for long-haul aircraft from 1959 to 1998, achieved in part through development of engines with larger bypass ratios • Turboprop aircraft have about 20% smaller TSFC than turbofan aircraft • No trend in lift/drag ratio – improvements in overall aerodynamics have offset the impact of fatter engines with larger bypass ratios • A slight upward trend in ratio of empty to full weight – related in part of extra in-flight entertainment systems

The energy requirement per passenger-km under cruising conditions is equal to the reciprocal of the (specific air range x seating capacity). It is shown by the coloured (solid) symbols in the next figure

Figure 5. 40 d Aircraft energy intensity (MJ used per available seat-km) Source: Babikian et al (2002, Journal of Air Transport Management 8, 389– 400, http: //www. sciencedirect. com/science/journal/09696997)

Other factors affecting energy use per km travelled by air travel: • Distance – the most energy-intensive part of the flight is the takeoff. On longer flights, this energy use is spread over more kms, reducing the average energy use per km • The airborne efficiency – related to distance flown (and thus flying time) to the shortest distance between the starting and ending points • The ground efficiency – the ratio of flying hours to total hours (including taxiing)

Figure 5. 41 a Ground efficiency for different aircraft and distances travelled Source: Babikian et al (2002, Journal of Air Transport Management 8, 389– 400, http: //www. sciencedirect. com/science/journal/09696997)

Figure 5. 41 b Airborne efficiency for different aircraft and travel distances Source: Babikian et al (2002, Journal of Air Transport Management 8, 389– 400, http: //www. sciencedirect. com/science/journal/09696997)

Figure 5. 42 Energy intensity averaged over the entire flight (including taxiing, waiting to take off, circling before landing) Source: Babikian et al (2002, Journal of Air Transport Management 8, 389– 400, http: //www. sciencedirect. com/science/journal/09696997)

See Figure 5. 37 d again – note the difference between energy intensity while cruising (solid symbols) and overall flight energy intensity (open symbols)

Prospects for the future • Weight reductions in a given class of aircraft through increasing use of C-fibre composite materials • 10 -25% further improvement in engine efficiency • Net result: overall reduction in fleet average energy use per passenger-km of 20 -25% from 1995 to 2030 seems to be quite feasible • Shifting from turbofan (“jet”) to the latest turboprop aircraft for distances up to 1000 km also reduces energy use • The most efficient aircraft will still be many times as energy intensive as high-speed trains

Projection of average CO 2 emission per rpk (revenue passenger-km) for the US aircraft fleet Source: Schafer et al. (2016, Nat Clim Change 6: 412 -418)

Blended wing and body – reducing energy intensity by 20 -30%. Major infrastructural changes (in airports) would be needed Source: Vyas et al. (2013, ANL)

Freight Transport

Figure 5. 43 Freight transport modes

Figure 5. 44 Variation of freight energy intensity with distance transported, and difference between modes of transport Source: Skolsvik et al (2000 b, Study of Greenhouse Gas Emissions from Ships, Appendices, International Marine Organization, London)

Figure 5. 45 Variation freight energy intensity with capacity factor Source: Skolsvik et al (2000 b, Study of Greenhouse Gas Emissions from Ships, Appendices, International Marine Organization, London)

Prospects for reducing road freight transport energy intensity (that, reducing energy use per tonne-km of transport) • Improved diesel engine thermal efficiency (from 45% to 55%) • Hybrid diesel-electric trucks – 25 -45% savings for delivery vehicles in urban settings • Elimination of idling in heavy trucks (averages about 2400 hours/year) through use of auxiliary power units such as fuel cells for air conditioning and other loads (high-temp fuel cells, not requiring Pt catalysts, could be used)

Prospects for reducing road freight transport energy intensity (continued ) • Improved aerodynamics • Improved loading factor • Reduced speed

Aerodynamic Truck

Net result: A 50% or better reduction in the energy intensity of freight transport by new trucks is achievable over the next two decades. More time would be required to see this improvement over the entire fleet of trucks

Locomotives for Freight Trains • Ideal candidate for early application of fuel cells (on-board fuel storage and start-up time are not an issue) • Upfront costs less important than for passenger vehicles because fuel cost savings over a 20 -30 year lifespan are important

Figure 5. 46 Locomotive energy flow with a diesel engine used to generate electricity that in turn drives an electric motor

Figure 5. 47 Locomotive energy flow using a fuel cell to generate electricity that in turn drives an electric motor

Reducing the energy intensity of shipping • The International Maritime Organization has identified measures that could be phased in and which would reduce shipping energy intensity by 37% over 20 years and by 45% over 30 years • Small wind turbines on a vertical axis (Flettner rotors) fitted to ships and connected to propellers could potentially reduce the remaining energy requirement by 30 -40% (already used by the German wind turbine manufacture Enercon on the barges used to transport its offshore wind turbines to where they are installed)

Reducing the need to transport freight • The previous discussion has focused on the energy intensity of freight transport – the energy used to transport a given amount of freight a given distance • Globalization and free trade deals have caused global freight movement to increase much faster than the growth of the global economy

• This growth has depended on cheap fuel and unequal wages, worker benefits, and health, safety and environmental standards in different countries (and, in some cases, artificial exchange rates) • With the inevitable increase in fuel costs and a reduction in the differences between countries, the trend toward ever greater trade may very well be reversed, thereby contributing to reduced freight transportation energy use • Conscious effort by consumers to buy locallyproduced products can also contribute to this

Impacts of e-commerce • Allows greater transport distances and greater delivery frequencies (tending to increase energy use), but can also be used to improve the distribution system • Can result in greater use of packaging • Can result in reduced warehouse building area by facilitating just-in-time delivery, thereby reducing warehouse energy use • Can permit electronic grocery shopping and home delivery services

To maximize the energy savings from e-shopping and home delivery, a re-organization of the relationship between suppliers, distribution and collection centres, and retailers would need to occur. This might happen spontaneously from the need for improved logistics

Figure 5. 48 Flow of goods from producers to consumers at present (left) and as might occur with an energy-efficient e-commerce arrangement Source: Bratt and Persson (2001, European Council for an Energy Efficient Economy, 2001 Summer Proceedings 3, 480– 492)