Electric Plug-In Versus Electric Hybrid Comparison Google Fleet Study

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Eustace Harrington
8 years ago
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1 Georgia Institute of Technology Milwaukee School of Engineering North Carolina A&T State University Purdue University University of Illinois, Urbana-Champaign University of Minnesota Vanderbilt University Electric Plug-In Versus Electric Hybrid Comparison Google Fleet Study Perry Y. Li Professor and CCEFP Deputy Director University of Minnesota TB3: January 13, 2010

Vanderbilt University Electric Plug-In Versus Electric Hybrid Comparison Google Fleet Study

2 Methodology Google fleets Various conventional vehicles, hybrids and hybrids with plug-in conversions Including: Ford Escape, Toyota Prius, and others Two types of experiments: Fleet wise comparisons (free loaners for Google employees) RechargeIT experiment: Explicit, controlled experiments with planned trips Compare overall fuel usage, CO 2 footprint, cost.

comparisons (free loaners for Google employees) RechargeIT experiment: Explicit, controlled

3 GFleet-wise results... Downloaded from on 1/7/2010

4 Recharge-IT results Electricity usage: Escape PHEV: Wh/mile; Prius PHEV: 139.6Wh/mile Higher MPG (relative to GFleet) is apparently due to differences in drive cycles.

5 Efficiency Comparison Compare hybrid electric (HEV) vs plug-in (PHEV) Escape and Prius only PHEV uses both gasoline and electricity Gasoline heating value: W gas =32MJ/liter Arbitrage analysis question: Assuming electricity used is converted from gasoline. What does this conversion efficiency have to be for PHEV to utilize less fuel than HV?

=32MJ/liter Arbitrage analysis question: Assuming electricity used is converted from

6 Arbitrage Analysis Electricity Fuel Drive cycle Fuel 1 Plug in Hybrid Vehicle Hybrid Vehicle Drive cycle Assumption: Fuel 1 < Fuel Fuel-electricity generation Electricity Fuel - + Fuel 1 Plug in Hybrid Vehicle Drive cycle Equivalent Hybrid Vehicle

1 < Fuel Fuel-electricity generation Electricity Fuel - +

7 Results: For PHEV to be more efficient: E elect η gas elec W gas Break even efficiencies: GFleet (Prius): RechargeIT (Prius): RechargeIT (Escape): µ 1 MPG HV 1 MPG PHEV η gas elec =51% η gas elec =41% η gas elec =36.9% Less than Elect. generation efficiency from fossil fuel: 33%** * (downloaded 1/7/2010) * Electric and Hybrid Vehicle Research, Development, and Demonstration Program; Petroleum-Equivalent Fuel Economy Calculation

generation efficiency from fossil fuel: 33%** * http://cleantechnica.

8 Conclusion: Efficiency Drive train efficiency is not necessarily enhanced by plug-in If fossil fuel is used in electricity generation, off board electricity generation needs to be MORE efficient than on board IC engine to beat regular hybrids PHEV allows for diversity of electricity generation with no CO2 (nuclear, solar.) Bio-fuel also allows IC engine to use renewable fuel sources

efficient than on board IC engine to beat regular hybrids PHEV allows for diversity of

9 Emission CO2 Vehicle emission per fuel consumption: Prius: Hybrid 23.6 lb/gallon; PHEV lb/gallon Escape: Hybrid lb/gallon; PHEV lb/gallons Outlier? Emission should be in direct proportion to fuel usage Total emission per mile???? Depend on source of electricity and generation efficiency If electricity is generated by gas power plant, emission of PHEV will be WORSE since total fuel usage is worse. Conclusions: Unless electricity source is from renewable or nuclear, PHEV will have worse total emission than hybrids.

??? Depend on source of electricity and generation efficiency If electricity is generated by gas power plant, emission of PHEV will

10 Cost comparison - 1 Google s CA cost comparison (on 1/11/10): Gas Costco = $2.77 / gallon Average 2009 residential electricity cost: $0.152 / kwh

com/ (on 1/11/10): Gas price @ Costco = $2.

11 Cost comparison - 2 MN cost calculation: Electricity (2009 residential): $0.101 / KWh Gasoline: $2.65 / gallon (average 1/7/2010) Prius (HV): $5.48 per 100 miles Prius (PHEV): $2.83+$1.41=$4.24 per 100 miles Escape (HV): $8.22 per 100 miles Escape (PHEV): $5.40+$1.34=$6.74 per 100 miles

48 per 100 miles Prius (PHEV): $2.83+$1.41=$4.24 per 100 miles Escape (HV): $8.

12 Cost comparison - 3 CT cost calculation: Electricity (2009 residential): $0.202 / KWh Gasoline: $2.75 / gallon (average 1/11/2010) Prius (HV): $5.69 per 100 miles Prius (PHEV): $2.94+$2.82=$5.76 per 100 miles Escape (HV): $8.54 per 100 miles Escape (PHEV): $5.60+$2.69=$8.29 per 100 miles

69 per 100 miles Prius (PHEV): $2.94+$2.82=$5.76 per 100 miles Escape (HV): $8.

13 Conclusion: Cost Total cost depends on fuel cost and electricity cost Cost for operating PHEV is about the same or cheaper than HV Advantage for PHEV if fuel cost is high and electricity is low Advantage is not over-whelming. Location and temporal pricing differences make big differences Economic policy, rather than technologies, may determine cost advantages

electricity is low Advantage is not over-whelming.

14 Summary Google HEV and PHEV fleets provide data for comparing overall fuel / electricity economy of same vehicle chassis. To beat similar HEV, electricity consumptions by current PHEVs require that: electricity be generated from renewable/ nuclear source If using fossil fuels, generation must be more efficient (37-51%) than present day power-plants (33%) Emissions should follow similarly to well-to-wheel fuel usage Cost of energy depends heavily on location and date - may be slightly cheaper for PHEV than HEV.

source If using fossil fuels, generation must be more efficient (37-51%) than present day power-plants (33%) Emissions should

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