CHAPTER 8 TRANSPORTATION ENERGY TECHNOLOGIES

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1 CHAPTER 8 TRANSPORTATION ENERGY TECHNOLOGIES 1

2 Student Presentation Topics in this Unit Overview of transportation energy Battery electric vehicles (EVs) Hybrid electric vehicles (HEVs) Fuel cells and fuel cell vehicles (FCVs) 2

3 Readings of Interest Larminie, J and Dicks, J (2000). Fuel Cell Systems Explained. Chapter 2, Efficiency and Open Circuit Voltage. John Wiley, Chichester, West Sussex. Burns, L et al (2002); Vehicle of change: hydrogen fuel cell cars could be the catalyst for a cleaner tomorrow Scientific American, v287:n4, pp Available through CU Library System Kreith, Frank et al (2002), Legislative and Technical Perspectives for Advanced Ground Transportation Systems., Transportation Quarterly v. 56 no1 (Winter 2002) p (pdf in website) Iqbal Husain, ElectricandHybridVehicles:DesignFundamentals(2003). CRC Press, Boca Raton, FL. 3

4 Some Observations about Transportation Energy Along with electricity, the other big target 27% of total US energy consumption in 2000 May overlap increasingly with electric generation in future Battery electric vehicles Fuel cell vehicles Plug in hybrid electric vehicles Vehicle to grid systems 4

5 Options for Reducing Energy Use and CO2 Emissions Shift to battery or hybrid drivetrains Shift to alternative fuels Shift to fuel cell vehicles Make systemic changes (mostly in Unit 11 on systems issues ) Shift passengers and freight to more efficient modes Rationalize use of transportation system 5

6 Alternative Pathways to Carbon Emission Free Transportation Name: Adopt Battery Electric Adopt Hydrogen Approach Innovative onboard energy storage technologies Continue use of carbon, but offset emissions Phase out free-ranging mechanized transport Description: Carbon-free electricity provided to battery powered fleet Carbon-free hydrogen provided to fuel cell vehicles Carbon-free compressed air, spinning flywheels, etc. Sequester CO2 and/or expand use of bio-fuels Expand use of electric catenary or drastically reduce mechanized transport Notes: 1) This list is EXHAUSTIVE (to the best of our knowledge); 2) ALL of these options are VERY challenging! 6

7 Trend in US Energy/CO2 Levels 2.4 Relative growth (1970 = 1.00) Freight Passenger All Trans. All Energy ResComm Industrial 7

8 US Energy Consumption by End Use Energy [EJ/year] Freight Passenger All Trans. ResComm Industrial

9 Battery Electric Vehicles (EVs) History Early prototypes ca s 1970s: GM prototypes, <130km range, 130 kmh (80 mph) top speed 1990s: Saturn EV1, <150km range, 150 kmh (90 mph) top speed, very good acceleration, approx leased Also, growth of Limited Use Vehicles GEM Limited-Use Electric Vehicle 9

10 EV Powertrain Note that source charger is not onboard vehicle Modern EVs convert DC to AC 10

11 Some Vehicle Design Considerations Same criteria apply to EVs and HEVs as to ICEVs Maximum Range: distance between refueling (for ICEV) or recharging (for EV) Maximum Gradability: steepest incline that the vehicle can climb at a given speed Maximum Velocity Maximum Acceleration (e.g. time to go from 0 to 100 k/h) Example: Saturn EV1: Curb weight: 920 kg plus 400 kg batteries Lead acid batteries: 55 wh/kg, ~$125/kwh Charge requirement: wh/kg km 11

12 Maximum range for a representative lead acid battery EV in km on a single charge, as a function of mass of batteries installed 12

13 Vehicle cost as a function of range for EV 13

14 Overview of Hybrid Vehicles (HEVs) 1970s: first standards for HEVs published by USDOE First on US market was Honda Insight (1998) Currently marketed by many major makers in US market, elsewhere Combines best features of ICE and EV technology: High energy density, long range of ICE High starting torque, low emissions of EVs Currently emerging: plug in hybrids w/ 20 or 60 mile electric range 2005 Toyota Prius Courtesy of philglaserphotography.com 14

15 Growth in US Hybrid Sales

16 Hybrid Electric Drivetrain Design Source: Kreith et al (2002) 16

17 Use of Atkinson Cycle in HEVs Type of ICE used in Prius, Ford Escape Cycle invented by James Atkinson in 1882 Optimizes efficiency at the expense of power Two alternatives for implementation: 1. All 4 cycles of 4 stroke engine happen in single revolution of crankshaft: greater expansion ratio than compression ratio 2. Intake valve is held open longer, effectively reducing compression / increasing expansion >> See animation at ; also 17

18 Comparing Toyota Prius to VW Diesel Jetta, Toyota Echo Compare to VW Jetta Diesel Eng Size MaxPr Power/L Economy [MPG] cc [kw] City Hwy Overall Prius Prius Jetta [kg] City Hwy Overall Prius Echo (auto) Echo (man) Compare to Toyota Echo Gasoline ICEV 18

19 Take home points on electric & hybrid vehicles 1. The weakness of the EV is the cost and weight of batteries. new battery technology is becoming lighter and cheaper In the future, EVs may be able to break into markets where costs are currently prohibitive 2. HEVs can compete for market share by compromising between EVs and ICEVs 19

20 Reasons for Interest in FCVs 1. Greater potential efficiency than internal combustion engine (ICE) 2. Eliminate emissions at the tailpipe 3. Allow a wide range of initial energy sources, including non fossil and renewable 4. Allow more flexibility in vehicle design 5. Easier to store/distribute hydrogen than electricity Prototype Fuel Cell Bus University of Delaware,

21 Figure Schematic of hydrogen fuel cell function, showing anode, cathode, and proton exchange membrane 21

22 Figure Exploded view of a fuel cell stack, made up of alternating units of fuel cells and bipolar plates 22

23 A New Vision for Fuel Cell Vehicles Most current fuel cell vehicles are retrofitted ICEVs In the future, FCVs might be designed from the ground up Energy is transmitted from the fuel cell to the wheels using electricity No fixed draft shaft, transmission, etc. More flexibility about how to lay out vehicle Example GM HyWire fuel cell concept car 23

24 Practical Consideration of Fuel Cell Efficiency Nernst equations provide theoretical model of performance Are most accurate at high temps At low temps, benefits of raising pressure are greater than predicted Not captured by Nernst equations:,, are partial pressures of H 2,O 2,andH 2 O, resp. Decline in,, risein as H2, O2 move thru FC, leads to decline in current density Tradeoff between high throughput and high efficiency In general actual efficiency is well below predicted maximum, due to limitations in materials technology 24