PHEV caution

Replies to This Discussion

Permalink Reply by Forbes Bagatelle-Black on February 1, 2008 at 8:16am

Different studies come up with different results. A 2005 study by the American Council for an Energy Efficient Economy (ACEEE) suggests that given the power-makeup of the current US grid, a mass switchover to PHEVs would reduce C02 emissions by 15%. They say that the tipping point would be at 80% coal-fired power.

▶ Reply to This

Permalink Reply by John D. H. King on February 2, 2008 at 11:39am

Good points from Tom and Forbes,

I'll weigh in on this one with another perspective.

Don't let the perfect be the enemy of the good.

I strongly support plug-ins not because they are the final solution. They are the next logical step. Obviously, we need to clean up the current electricity grid no matter what is on the roads. We need more wind, solar, geothermal, sustainable hydro, and biomass/biogas.

Plug-in hybrid technology is a gateway technology that helps get us to all-electric drive. And if we had a lot of plug-ins and all-electric drive cars on the road... imagine how much that distributed storage would boost the storage capacity for all those renewables I just listed.

John

▶ Reply to This

Permalink Reply by Tom on February 19, 2008 at 9:35pm

I broadly agree to not let the perfect be the enemy of the good.

I also happen to like the concept of the PHEV. I just think the claims are overstated and in some ways dangerously misleading.

We still have decades to go to make dramatic improvements to average grid emissions factors. More important is the fact that marginal grid emissions factors could be very far from coming down. Remember that a marginal load generally incurs the marginal emissions factor.

For example, if a grid is 50% coal, 20% hydro, 10% wind, 10% solar, and 10% natural gas, what happens if the load on the grid increases? Let's say this grid originally delivers 100 units of juice per day (50 from coal, 20 from hydro, 10 from wind, 10 from solar, 10 from NG). Then load goes up to 120. Where does the new juice come from? Well, you could claim that in response we could increase solar and wind by 10 & 10. So now you've got 50 coal, 20 hydro, 20 wind, 20 solar, 10 NG. But you have to recognize that you may have had the choice to add the solar and wind anyway. If you did that and did NOT add the new load, then you could shut down 20 units per day from coal: 30 coal, 20 hydro, 20 solar, 20 wind, 10 NG perhaps. So it was not the additional load that greened the grid, it was a separate decision on how to deploy renewables.

That said I'm hopeful that some of the very preliminary modeling will pan out that suggests "synergy" between night-charging EVs and increased total wind penetration potential. If this proves true than eventually EVs could logically be associated with green grid electricity.

The bottom line is that it will take longer than most enthusiasts think for PHEVs/EVs to favorably contribute to GHG reductions. During the ramp up period they could cause higher net GHG emissions.

▶ Reply to This

Permalink Reply by Charlie Botsford on February 18, 2008 at 6:24pm

I thought the argument about pollution and electric vehicles was settled back in the 90's when the EV-1 was introduced. Even considering 100% coal-fired power plant production, the numbers I get are almost two to one in favor of EVs over gasoline-powered vehicles on CO2. Assume 40% coal to electricity efficiency, 10% loss for T&D, 7% loss at the charger, 6% loss at the battery (lithium is pretty good), and 5% loss at the motor. The overall conversion efficiency at the wheels is about 30%. I've heard typical efficiency numbers of 15 to 17.5% for gasoline powered vehicles. Where's the confusion? EVs and PHEVs ought to be all over the place to fight global warming, to say nothing of allowing wind and solar grid penetration as John suggests.
The only way to get rid of coal is to make it obsolete.

▶ Reply to This

Permalink Reply by Tom on February 19, 2008 at 9:23pm

I'm not saying that the paper I posted is the definitive source on this topic. Indeed the paper was influenced by the electric utility industry and would be expected to have some bias towards the use of electricity. Even so, that paper states "if a PHEV’s electrical charge comes from today’s coal power, the plug-in would have higher global warming pollution compared to a non-pluggable hybrid electric vehicle." Clearly a pure EV would be even less favorable under these conditions.

As for the "argument" having been "settled" in the 90s, I'd say that the analysis was not and is not settled. Technological changes shift the results of the analysis.

▶ Reply to This

Permalink Reply by Brad Juhasz on February 26, 2008 at 1:06pm

Found an article based on this report in USAToday...
http://www.usatoday.com/money/autos/environment/2008-02-25-plug-in-...

▶ Reply to This

Permalink Reply by Tom on March 16, 2008 at 7:26pm

Thanks, now I'm in great company: USA Today.

So they raise the question - that's about as much as one can expect from non-specialty media. It's clear that even some of the 'experts' cited in the article are having difficulty with some of the concepts. They still refer to a case in which some arbitrary incremental load (in this case an automobile that demands electricity) can somehow logically receive 100% allocation from the scarcest, fixed amount supply resources feeding the grid (solar, wind, hydro).

Find me a grid somewhere where I can go home at night, flick on the TV and say "no worries, all my electricity is zero carbon". Why me? Why not some other entity causing incremental load?

I guess I could buy RECs (a discussion for another thread), but if that's the answer then it needs to apply to automobiles charging from the grid.

▶ Reply to This