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Donald Griggs
Columbia SC USA
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Regarding: "... in most regions nighttime charging increases GHG emissions, and nighttime charging can also increase health costs in some regions due primarily to increased air pollution from coal-fired power plants." While it might seem that answering the question, "Where did these 2 AM electrons come from that charged my Nissan Leaf?" would be important, that assumes that a coal power plant is (figuratively) throwing another shovelful of coal on the fire when charging starts. I'd understood that the great majority of US coal plants are operated in a continuous baseload mode, and don't attempt to be load-following plants. Especially since the US (shamefully) has no nationwide carbon tax, it makes economic sense for the utility to run these plants continuously at near full capacity, and the design itself of the typical coal plant doesn't facilitate load-following. Isn't a much more relevant question: 1) "If 1000 car buyers in my area chose a Leaf over an HEV Prius, what would the difference in CO2 emissions be? Since (as I understand it) the great majority of the increased-load generation is provided by peaking natural gas plants or renewables (or mid-merit gas plants) then late-night charging would not seem to meaningfully contribute to greater CO2. Two further questions might be: 2) How will the emissions balance likely change in future? In Q1 of 2015, 75% of new US generation capacity was in renewables. (Will this trend continue?) 3) Did the study consider the substantial emissions costs in refining gasoline? I confess I did not pay to buy the original study. I know they did mention that other pollutants are at play besides CO2, but I don't know if refinery and distribution CO2 costs were included in their CO2 comparison. Of course, the Leaf/Prius dichotomy was necessary simplification. A real-world new-car buyer who might be persuaded to buy a Leaf because of the battery EV credits might well have chosen, absent those credits, something other than a HEV Prius, and that probability-spread would have included dirtier vehicles. Maybe an absolutely rational credits policy would have rewarded both Leaf and Prius buyers to some extent, but isn't the real policy question "Did my state get a reasonable environmental bang for my taxpayer bucks?" rather than "Does a Leaf always result in lower carbon than any other choice?" As to the late-night charging question, I'm only a layman. Are my assertions and logic reasonable? ========================== Load following plants. New generation mix:
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Jul 20, 2015