The Green Hype about electric vehicles

Transcription

1 The Green Hype about electric vehicles Many news articles are now proclaiming that battery electric vehicles (BEVs) like the Nissan Leaf and plug-in hybrid electric vehicles (PHEVs) like the Chevy Volt are green vehicles, implying that they will reduce greenhouse gas (GHG) emissions. The Green Car Journal awarded the Chevy Volt the 2011 green car award. But are BEVs and PHEVs really green? According to the U.S. Department of Energy, the answer is no for many parts of the country, since more than half of all US electricity is currently generated by burning coal, the dirtiest (highest carbon content) fuel. As shown in Figure 1 below 1, the DOE projects that BEVs with 100 miles range will generate 230 grams/mile of CO 2 -equivalent of GHG emissions with the average US electric generation grid mix in the 2035 to 2045 time period, more than a fuel cell electric vehicle (FCEV) running on hydrogen made from natural gas which generates only 200 grams/mile, the lowest GHG emissions before clean fuels derived from solar, wind or biomass become available and affordable. A PHEV with 10 miles all-electric range (AER) will also produce 230 grams/mile of CO 2 -equivalent GHGs, and a PHEV with 40 miles AER like the Volt will generate 270 grams/mile. Figure 1. Well-to-Wheels greenhouse gas emissions for a variety of mid-size vehicles using the average US grid mix, projected for the 2035 to 2045 time frame (except for the top bar for today s gasoline car.) 1 Chart taken from the draft 2010 DOE hydrogen and fuel cell program plan at

2 In addition, the Argonne National Laboratory GREET 1.8d model 2 that estimates the total well-to-wheels GHGs for a wide variety of alternative vehicles shows that PHEVs using the average US grid mix will consistently increase GHGs compared to hybrid electric vehicles(hevs) without any grid charging. Figure 2 shows the Argonne GREET estimates of GHGs using the average US grid mix in 2020 as a function of the all-electric range for PHEVs running on three different fuels: diesel, E-85 3 and hydrogen made from natural gas 4. In all three cases, the lowest GHG emissions are for AER=0, which is a hybrid electric vehicle (HEV) without using any grid electricity. In other words, it is better to operate a PHEV as an HEV in terms of GHG emissions with these three fuels that have lower GHGs than a gasoline HEV 5. Plugging in these vehicles to charge car batteries with the average US grid mix in 2020 will always increase GHGs. Note also that the hydrogen-powered FCEV and an E-85 HEV both have lower GHGs than a BEV 6 (yellow square plotted at AER=70 miles) 2 The Greenhouse gases, regulated emissions and energy use in transportation model, by the Argonne National laboratory, available at 3 E-85 is a mixture of 15% ethanol with 85% gasoline. 4 The model assumes that the hydrogen is used in a fuel cell electric vehicle (FCEV); since FCEVs are electric vehicles, they can also be operated as PHEVs by adding extra batteries. In fact, the Ford Motor Company has built and road-tested a plug-in FCEV based on the Ford Edge platform. 5 Some readers may be surprised to see diesel fuel in this cleaner category since diesel has a reputation as a dirty fuel due to emissions of NOx and particulate matter (PM) pollution. But producing diesel fuel from crude oil generate less GHGs than producing gasoline, and diesel compression-ignition engines have higher fuel economy that gasoline spark ignited engines. 6 Note that the estimated BEV GHGs is higher in 2020 (257 grams/mile) than the DOE estimates for the 2035 to 2040 time period at 230 grams/mile. This is due to the 2010 Annual Energy Outlook forecast for the average US grid mix, which projects the percentage of US electricity coming from coal will decrease from 54.7% in 2007 to 54.1% in 2020 and to 52.5% by 2035, the last year of the AEO projection and the percentages of renewables will increase from 2.4% to 6% to 7.7% in those three years. 2

3 Figure 2. WTW GHGs for PHEVs as a function of all-electric range (AER) in 2020 assuming the average US grid mix In some parts of the country such as Illinois with most electricity made by burning coal, a PHEV40 like the Volt will not only generate more GHGs than an HEV, but the Volt operating in Illinois will also generate slightly more GHGs than a conventional (non-hybrid) gasoline ICV as shown by Figure ES.1 from Amgad Elgowainy and his colleagues at the Argonne National Laboratory 7, and a BEV charged by the average US grid mix will generate more GHGs than a gasoline HEV like the Toyota Prius. 7 Amgad Elgowainy, J. Han, L Poch, M. Wang, A Vyas, M. Mahalik, A. Rousseau, Well-to-Wheel Analysis of Energy Use and Greenhouse Gas Emissions of Plug-in Hybrid electric vehicles. Report # ANL/ESD/10-1 available at 3

4 PHEV-40 BEV Gasoline conventional (nonhybrid) car Gasoline HEV In California, with its lower percentage of coal electricity, plugging in a PHEV40 like the Volt will decrease GHGs slightly as shown in Figure 6.12 (next page), also from Elgowainy et al. Thus a gasoline HEV operating in California generates approximately270 grams/mile of CO 2 -equivalent GHGs, while a PHEV-40 like the Volt would generate approximately 245 grams/mile of GHGs, but this would still be more than a FCEV operating on hydrogen made from natural gas at 225 grams/mile 4

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