Getting back to PNNL grid capacity report after the holiday ...
I originally posted the digest summary of the PNNL report to address the capability of the grid to cover a surge in electric vehicles. The report also addresses other issues such as emissions and gasoline usage changes due to the use of electrics, with a stated set of assumptions for the model they ran.
russ_waters said:
According to the wiki on coal power, it is loaded at 67%, so that's quite a bit of headroom for extra night generation. But anyway - it's your article that says there would need to be a lot more coal power generation...
You're right about the latter, the [PLAIN]http://energytech.pnl.gov/publications/pdf/PHEV_Feasibility_Analysis_Part1.pdf" model assumes a lot of coal plants will run harder to meet the theoretical nationwide PHEV demand.
russ_watters said:
So a 27% reduction in pollution,
That figure is the reduction only in green house gasses (CO2), nationwide, not all pollution for which the story is much more complicated. Here's the emissions chart from the [PLAIN]http://energytech.pnl.gov/publications/pdf/PHEV_Feasibility_Analysis_Part1.pdf" report. The top row is the ~dozen US grid segments. CNV=California/Nevad, ERCOT=Texas, etc.
Note in some grid segments heavy in natural gas power (versus coal) like California and Texas the reduction in CO2 would be 40%, while the heavy coal midwest stays about flat. Other pollutants like organic compounds (VOC), e.g. benzene, and CO fall nearly 100%. Particulates and SOx would go up over most of the country. However, in urban areas all emissions types fall drastically.
Some comments about the assumptions in the PNNL report. Amazingly to me, their model rules out the use of gas based "Peaking Plants" because according to PNNL they wouldn't be economic:
PNNL 2007 said:
Peaking plants (combustion turbines). These plants are designed for a relatively short run time. Typical capacity factors for combustion turbines are in the 0.15 to 0.20 range. Although the capacity factor could be increased to some degree, the significantly higher operating costs are unlikely to make combustion turbines a viable resource for PHEVs.
I doubt that assumption holds now w/ US natural gas discoveries and falling gas prices, but even if PNNL is still right in 2009, a consequence of that assumption is that national policy in a PHEV equipped country could by fiat call for more natural gas electric generation from the utility operators, or to use only low sulphur coal, or more and better coal scrubbers, at the cost of a couple more cents per kWh for the PHEVs.
So instead of peaking gas, PNNL assumes that mainly coal and gas boiler plants would be dispatched to meet the difference:
PNNL 2007 said:
The remaining marginal generation capacity [for charging cars] consists of coal-fired thermal plants, natural-gas-fueled steam plants, and combined cycle plants. Not considered as marginal capacity for the valley-filling are nuclear, conventional hydro power, and renewable energy capacities because these are already fully utilized. Nuclear capacity is normally operated at its maximum capacity. Wind and solar generators are fully utilized whenever the resource is available. Conventional hydro generation is limited by finite water resources.
brackets mine.
russ_watters said:
[...] mostly covered by regenerative braking and the lack of idle consumption
Where's that 'mostly' coming from? The electric drive train is more efficient than an ICE at nearly any operating point.
russ_watters said:
In other words, if you switch from a 25 mpg car to a 30 mpg car, you get the exact same environmental benefit as switching to a full electric!
I'm guessing when you say 'hybrid' there you mean with no plugin as in the current Prius. This report only addresses Plug-in Hybrid Electric Vehicles (PHEVs), not fully electric vehicles. Either way, the overall environmental benefits for a 20% efficiency improvement for an ICE vehicle and a PHEV are not the same.
russ_watters said:
And if you switch to a hybrid, you get a much better environmental benefit than if you buy an electric car! I don't see in the article a statement about what how much of each (coal and natural gas) would be added under their calculations, but it doesn't really matter: the 27% pollution reduction is the bottom line either way.
The generation mix matters as demonstrated by the Texas and California regions. Coal throws off twice as much CO2 as natural gas and all of the SOx.
russ_waters said:
As far as I'm concerned (and I've repeated this many, many times), until we get rid of our coal power plants, the environmental benefit of switching to electric cars is marginal at best.
In addition to the emissions benefits, PHEVs per the report would cut petroleum imports by 52%.