— by Tom Owens —

Last month, I wrote an opinion piece in OrcasIssues that tried to describe the impact (CO2 production) of new electric loads (including EV’s) here in the San Juans. To understand this, we must know what type of fuel is used by the plant meeting the new load. The key to my view is that electric generating plants are dispatched (brought on and off line) on the economics of their variable cost (mostly fuel cost). This is electric industry standard practice. At any given time, the low cost plants are being used to their maximum capacity. Any new demand (EV or other) would be served by the next most expensive plant that was not operating at full capacity.

The clean generators (hydro, solar, wind, nuclear) all have very low variable cost. The dirty generators (natural gas and coal) all have higher variable cost. In my view, most of the time in the current NW Power Pool mix of generating plants, the plant that meets the new load would be a coal fired generator. If total load is low, this power could come from natural gas fired plants. Natural gas is displacing coal fired generation in the US, partly because of the lower cost of natural gas (thanks in part to fracking). This could change in the future, but for now, natural gas is generally cheaper than coal in our region.

The question this conclusion raised was “Compared to a vehicle running on gasoline, how clean (from a CO2 point of view only) is the new LEAF electric vehicle running on OPALCO electricity?”

I asked OPALCO for their calculations on this comparison; which they willingly provided and were kind enough to discuss with me. The “economic dispatch” concept took a beating but they listened. Their calculations and conversion factors lead OPALCO to the conclusion that a new LEAF is 200x, 40x, 5x or 3x as clean as gasoline vehicles (on E10 fuel) that get varying mpg. Their range of answers seemed to be based on which mix of generating capacity that they feel the electric energy would come from to charge the electric car. For example, the 200x result seems to compare a 10 mpg truck against a new LEAF running on a BPA mostly hydro mix of generation. These numbers would be correct if you identify the vehicles you are comparing, ignored the fact that the electric system is interconnected and if the concept of “economic dispatch” is incorrect. I would recommend comparing same size vehicles and using the resources that would be economically dispatched to meet the new load from our interconnected system.

So using OPALCO’s conversion factors and some US Energy Information Agency (EIA) data we can get some good but not perfect answers (good enough for ball park answers) to our question. For example, I have not tried to track down the CO2 cost of finding, transporting, refining and delivering the fossil fuels (gasoline, coal or natural gas) that are involved here or looked at the transmission and distribution system loses on the electric side. I use the “economic dispatch” concept to determine which generation resource the LEAF’s energy is coming from.

First let’s looks at a gasoline vehicle (using 10% ethanol fuel) going 1000 miles and getting 35 mpg (city):

CO2 production – 18.95 lbs. CO2/gallon – EIA including ethanol
28.6 gallons of gasoline consumed going 1000 miles at 35 mpg
CO2 produced —– 541 lbs. CO2

A new LEAF traveling 1000 miles using OPALCO energy from the incrementally dispatch plant:

4 miles/kwh – OPALCO’s number – this could be lower or higher.
Coal generation CO2 production – 2202.2 lbs. CO2/ Mwh – OPALCO
Nat Gas generation CO2 production – 981 lbs. CO2/Mwh – OPALCO
NWPP Blended CO2 production – 1132 lbs. CO2/Mwh – OPALCO
CO2 produced:
Coal ————- 550 lbs. CO2
Natural Gas —- 245 lbs. CO2
NWPP Blend —– 283 lbs. CO2

If you buy the “economic dispatch” approach, you could conclude from this that a gasoline vehicle at 35mpg traveling 1000 miles will emit about the same amount of CO2 as the LEAF traveling 1000 miles running on electric energy generated by coal (541 lbs. vs 550 lbs.). If the gasoline powered vehicle gets better than 35 mpg, it is cleaner that the LEAF. If the gasoline powered vehicle gets less than 35 mpg, the LEAF is cleaner. So the LEAF wins (from a CO2 emissions point of view) against lower mpg vehicles and loses against higher mpg vehicles (think Prius), 35 mpg being the break-even point.

If the LEAF was using electricity generated by combined cycle natural gas plants, it is about twice as clean as the 35 mpg gasoline car (541 lbs. vs 245 lbs.). So here, the LEAF wins, getting even better as the mpg of the compared gasoline vehicle goes down. Unfortunately, natural gas generated electricity is less expensive than coal generated electricity. The natural gas plants would likely already be on line. This would force the coal plants to take the new load. However, it could happen, at times, that the natural gas plant is used for the new load. In that circumstance this comparison is valid for the times natural gas is the fuel used to generate the electricity.

Some would take the view that the new LEAF is not really responsible for all the additional CO2 emitted to charge up the battery. The reasoning being that everyone already on the system has put the new load (the LEAF) onto the highest demand plant (coal) so everyone all should share in the additional CO2 produced. This would lead us to use a blended (from a power generation point of view) to calculate the LEAF’s share of the load. A good approximation of this blend (since I could not find WECC data) would be the North West Power Pool (NWPP) blend. Using a BPA blend (mostly hydro) is invalid because the BPA system is not isolated from the other systems in the WECC.

If you believe in the NWPP blended approach then the LEAF would be using coal, natural gas, hydro, solar, wind and oil plants in the NWPP. It would be cleaner than the 35 mpg gasoline car (541 lbs. vs 283 lbs.). Here the LEAF wins but it is not pollution free and not as good as a LEAF on natural gas generated electricity. However, it is important to realize that new CO2 production would actually be 550 lbs. So, someone has to stand up and take credit for the remaining 267 lbs. (550 – 283). This is simply a “who gets the blame” game. The atmosphere gets the whole 550 lbs.

So, pick your approach. At least you can see that there is a negative environmental impact for each use of electric energy, including Electric Vehicles. If the LEAF impact is less that the gasoline power vehicle, the net impact is positive. If the LEAF impact is greater than the gasoline power vehicle, the net impact is negative.

The good news is that the impact of conserving or producing a bit of energy with solar cells has the same quantitative CO2 impact but in the opposite direction. Here we are not involving a LEAF, just conserving or producing clean energy. It is positive for the environment.

This all raises yet more questions, “What are the other benefits of buying an electric vehicle?” “How does OPALCO (and all of us as owners) benefit if you buy an “EV?” Next time….

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