{"id":4721,"date":"2011-10-18T09:07:18","date_gmt":"2011-10-18T16:07:18","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=4721"},"modified":"2011-10-18T09:08:16","modified_gmt":"2011-10-18T16:08:16","slug":"4721","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/4721\/","title":{"rendered":"How Green was GFC Electricity?"},"content":{"rendered":"

The blog received several comments about the relative energy use of electric aircraft, and how NASA and the CAFE Foundation might have overstated the efficiency and low emissions for the electric aircraft in the competition.<\/p>\n

Reader Robert Swanson thought the conversion between kilowatt hours and gasoline created a discrepancy. \u201cThe discrepancy in performance of gasoline and electric powered aircraft is due to an absurd conversion factor between kWh and gallons of gasoline.\u00a0 The conversion should be calculated from the number of gallons of gasoline consumed by the engine driving the generator used to charge the batteries.\u201d<\/p>\n

Steven Crow added this objection.\u00a0 \u201cEven after reading the relevant pdf’s, it is far from clear to me how CAFE computed \u2018mileage\u2019 for the electric aircraft. The right way of doing it is clear enough: base the mileage on the fossil fuel used to charge the batteries. \u00a0Electric motors and batteries are not subject to Carnot efficiency limitations. \u00a0They can seem to be nearly 100-percent efficient until one looks at the power source that charged the batteries. That objection would disappear if CAFE used solar power to charge the batteries, but the rules appear to require diesel generators.\u201d<\/p>\n

Alan Soule, a CAFE board member and Charging Master for the event, drives a Tesla roadster which he will soon charge through solar panels on his house\u2019s roof \u2013 making him a very green motorist.<\/p>\n

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Alan Soule's chart showing relative CO2 emissions for different electric power sources, including NG (natural gas) and PV (photovoltaics)<\/p><\/div>\n

He says the following about the chart shown here.\u00a0 \u201cI have used the attached chart for talks that I have given on EV\u2019s.\u00a0 People just assumed that all power generation uses coal. Actually, about 50 percent of the electricity generated in the U.S. is from coal.\u00a0 California only has a few coal-fired plants and a relatively large proportion of renewable energy sources. Thus, in California, when you consider that the electric motors are around 90 percent efficient and the batteries store about 85 percent of the power that is input to the charger, the carbon \u2018footprint\u2019 of an electric vehicle is considerably less than [that of] an IC vehicle.<\/p>\n

\u201cAs I discovered…, the electric airplanes in the GFC were 50 percent more efficient than my electric vehicle, with the electric airplanes about the cleanest way to get around.\u201d<\/p>\n

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NASA Technology Chief Joe Parrish, Sonoma County Supervisor Mike McGuire, and CAFE President Brien Seeley cut the ceremonial gas hose to open first electric aircraft charging station in US<\/p><\/div>\n

CAFE\u2019s electric charging stations, the first in any U. S. airport, provide six outlets for as many aircraft, and are supplied with clean power from geothermal sites near Geyser Peak, one of the turnpoints on\u00a0 the Green Flight Challenge course.\u00a0 There was no need, in this case, for a coal\/natural gas, or Diesel conversion and GFC challengers flew on a near-pristine source of power.<\/p>\n

Otherwise, yes \u2013 there is work to be done to make even EVs cleaner and less dependent on carbon-based power sources.\u00a0 We all share the responsibility to make this part of a better future.<\/p>\n