Global warming -- Check my math/reasoning please.

Factual Questions
1

I’ve been reading some articles about a research paper.
(links are to an article in NRC (Dutch, soft paywall), Arstechnica and the research paper is from Nature (paywall))

The conclusion of this research seems to be that electric cars and efficient electric heating are a net benefit when some part of the used electricity has low carbon emissions.

That can’t be right. (tell me where I am making a mistake!)

For the purpose of this thread I’ve created a simple model of a country:
in this country 1/3 of all energy is consumed by transportation, 1/3 is consumed heating houses and 1/3 is used generating electricity. The goal is to do this with 0 emissions, and reduce emissions as efficiently as possible along the way (to 0 emissions).

If this country converts 50% of its electricity generation to something with zero emissions they will have reduced their carbon footprint by 1/6. Then they replace 50% of their cars with EVs. Again 1/6 reduction! Wait, where does that power come from?
How is it beneficial for their emissions to start to use more electricity? As long as not ALL generated power is “Green” this makes 0 sense to me. Electrical cars (EV) use about as much power as a normal household so the extra power needed is not insignificant. In these articles/research the electrical power is treated as if it is just there, ignoring that that power has to be generated somehow.
In the articles/research they calculate with whatever “mix” is available(in my example 50% renewable) Then they conclude electrical cars are 50% cleaner. Here I stop understanding basic math. We have to add capacity to allow for all that extra power: this comes 100% from conventional generation. If you don’t plug in your car, the coal-fired plant has to burn less coal. Not 50%, 100% of the extra power comes from the least clean source, the one you could close if demand was just a little less. If you lose the electrical cars you can lose the coal plant. This remains true until all generated power has better thermal efficiency as a car. Introducing the electrical cars is carbon neutral in the bad sense: It is great for air quality in cities, for the planet: meh.
I hope I’m missing something. (All kinds of policy and subside is based on me being wrong) Can someone explain what I’m missing?

Some fun figures:
Thermal efficiency of
internal combustion engine(ICE): 20-35%
Coal fired power plant 35%
combined cycle gas plant 60%

electrical losses
in transportation 5%
in charging 7%
in discharging 15%
(numbers are rounded-- I think fairly)
That leaves an EV on roughly the same efficiency as an ICE)

This is not an argument against EVs: Some R&D in charging infrastructure and production has to be done now, ahead of sufficient renewable sources. I just want to emphasize that they should be treated as such (R&D) not as a meaningful measure to reduce carbon emissions now. Our main focus should lie with replacing all conventional production of electricity with zero carbon alternatives, insulating houses, improving efficiency of transportation (hybrids? smaller cars? public transport?)

2

Even if all of the electricity powering your car came from coal, coal plants are enough more efficient than car engines that it’s still a net positive. But it won’t all come from coal. Windmills are sometimes shut off when demand is low. Increase the demand at those times, and you can keep the windmills running. This works especially well with loads like charging a car’s batteries, that don’t have to be done at a specific time, and can be smart-metered to when there’s excess capacity.

3

There is also the energy cost of transportation of the gas to the gas station, since it relies on ground road transportation rather than pipes or trains, as well as the energy spent driving to a gas station rather than charging at home or work.

4

The most persuasive argument for electric transportation vehicles is that it is the most fungible of all alternatives to petrochemical-powered vehicles; wherever we can produce electricity, it can be used for transportation, and as those sources change over time (more solar, clean natural gas, propane, 4th gen nuclear fission, eventual nuclear fusion) the cars will work the same. This will require massive improvements to our electric power distribution infrastructure, but we are overdue for that anyway from both and efficiency and security perspective.

The problem, however, is that the material resources need to built electric motors and electrochemical batteries are the Achilles heel; copper, lithium, and the various rare earth minerals need to build powerful magnets and catalysts are limited in availably and very polluting to mine. We’re going to have to figure out how to do more with less; both more efficient use of materials (or alternatives like superconducting quenched carbon…if it can actually be produced) and fewer vehicles overall.

Getting back to the o.p., while it is certainly desirable to develop and implement zero carbon emitting power production, we also need to consider methods we can deploy in the very near term that may not have zero carbon emissions but will at least produce energy with a substantially lower carbon footprint while allowing for a transition to future carbon-free energy sources. We also need to consider the cradle-to-grave emissions and cost; many nuclear fission power production advocates like to promote the fact that the fission process itself produces no carbon emissions, but there are substantial extra energy costs in separation, enrichment and fuel production for the once-thru cycle, high embedded carbon in pressurized and boiling water reactors with thousands of tons of steel and concrete, large transportation carbon footprints, and of course the other downsides that have plagued the nuclear power industry into not being competitive including the uranium mining and resulting environmental pollution, spent fuel handling and disposal, and plant retirement costs including the disassembly and removal of radioactive materials.

This doesn’t mean that nuclear fission power production shouldn’t be part of a future energy portfolio, and in fact it is unavoidable, but it does argue for the development of better fuel cycles requiring less processing and enrichment and with partial or ‘complete’ burnup of actinides, less protective infrastructure and elaborate “fail-safe” systems, and more modular design that doesn’t require such expensive site-specific modification. And we also need to have an array of other sources in our portfolio, as well as mechanisms to encourage or subsidize investment (particularly in photovoltaic solar power for which production costs have dropped so low that there is actually too much competition for market stability) and better methods for bulk energy storage of surplus power to be available in peak hours. And, of course, investment in controlled nuclear fusion with realistic timelines and goals.

Stranger

5

A coal fired plant is roughly as efficient as a very efficient car(around 35% thermal efficiency) . Until you take into account that you lose 5% of that energy before it reaches your house, then before you start powering the the electrical motor you lose another 20%. Then your motor is not 100% efficient: call it 95%: Putting the coal plant + EV on par with a normal car. Still great for reducing smog/noise in urban areas, but polar bears don’t care about that.

About the smart metering. Does that exist where you live?
As an engineer I love the idea:we could (should!) use the EVs to store excess power and feed it back when needed. We only need to develop some standards for communicating that stuff to the car and its charger:) while still guaranteeing you have enough range in the morning.

6

As long as both the electricity plant and the car are reliant on fossil fuel I think that is a wash.

7

The numbers I’ve seen put a significantly higher efficiency on the coal plant (mostly because they can operate at higher temperatures), and while both have losses in transportation, they pale in comparison to the inefficiencies of the respective heat engines.

It’d take me a while to dig out my environmental physics textbook, though.

8

It appears that there are around four thousand fossil fuel power plants in the US. I suspect each of these can store a rather large amount of source fuel on site. By contrast, there are around a hundred million vehicle fueling stations, each of which can typically store maybe a few score to a couple hundred thousand gallons of fuel for sale.

This means that the cracked fuel for vehicles has to first be moved in large quantities to distribution depots, then regularly shipped out to individual filling stations, as opposed to being shipped once, in large amounts, to the generating facilities.

Fuel trucks add traffic to the roads, causing a little more fuel to be used by concurrent road traffic, and are somewhat to a lot less efficient than rail cars going to the generating plant.

So, no, I do not believe that it is wash.

9

Many operating coal plants are supercritical coal plants (higher temps) and have efficiency in the 40-45 % range.

Here is a ready reference for you : Supercritical coal plant - Energy Education

10

Welcome back!
Though perhaps you never left. But it has been a while since I had the pleasure of one of your posts. Your contributions are always appreciated.

11

The energy density of gasoline is very high compared to car batteries.

I own a Tesla and in the short time I have owned it, I have had 3 flat tires one of them needing tire replacement. Electric cars are heavy and weight of the battery they have to lug around beats the energy needs of transporting gasoline from storage to fuel stations.

12

Looking around, it seems as though the low-end model 3, with a supposed range of 260 miles, contains the energy equivalent in gasoline that would get my '05 Focus about 55 miles. So my pretty good little car, driven by a person who does a bit of hypermiling, is still wasting 5 times as much energy as an electric car.

13

There is also the fact that the electric generating plant is a point source, compared to hundreds of cars wandering about the roads. An effective pollution control system can be installed on the plant, and upgraded as better systems are developed. But pollution controls on cars aren’t very effective, are seldom maintained, and can’t easily be upgraded when scattered on hundreds of cars. (Assuming they aren’t stolen – in my neighborhood emails, there are reports a couple times a week of someone having their catalytic converter stolen out from under their vehicle.)

14

No. 100,000 not 100,000,000

15

More like half. For example, the EPA rated efficiency of the Tesla Model-3 is 26 kWh per 100 miles. The aveage American drives 16,550 miles per year, so allowing 7% inefficiency for charging, that’s 4600 kWh per year. The average household electricity usage is about 11,000 kWh.

I think you’ll find that the 20-35% efficiency for ICE is the maximum, not average. Car engines are hardly ever operating at optimal efficiency, while power plants usually are. Also, electric cars have other tricks to improve efficiency - they don’t waste any power when stopped in traffic, and they have regenerative braking.

Also, that “discharging” inefficiency is already part of the car’s efficiency number. I’m not sure about the charging, but let’s assume it’s not.

So a Tesla Model-3 requires 26 kWh per 100 miles. Factor in those inefficiencies, and you need 26 kWh/ 0.95 / 0.93 = 29.4 kWh per 100 miles at the power plant. Assuming 35% thermal efficiency coal plant, we need 29.4 kWh / 0.35 = 84 kWh of thermal energy per 100 miles. With the 60% efficient combined-cycle natural gas plant, it’s 49 kWh per 100 miles.

I’m not sure what you would consider to be an ICE equivalent of a Tesla Model-3, but I’d assume a Toyota Corolla at 34 mpg combined = 3.0 gallons per 100 miles. 1 gallon of gasoline contains 33.4 kWh of energy, so that’s 100 kWh per 100 miles. I.e. a Tesla model-3 + coal power plant has a 19% better thermal efficiency than a Toyota Corolla. The natural gas plant is 104% more efficient. So the claim of 50% more efficiency is plausible assuming a mix of these power plants.

And here I’m just using your numbers, I haven’t checked to see if those are correct.

This also ignores all the inefficiencies of producing gasoline. How much crude oil do you need to deliver 1 gallon of gasoline to the customer? Including transportation of crude oil, energy used by the refinery, and transportation cost of the refined gasoline? Of course fuel for power plants need transport as well, but not nearly as much processing, and all the transportation is in bulk, which improves efficiency.

16

p.s. If we instead assume a 52 mpg Toyota Prius, that seems more efficient than coal power plants, though not as good as natural gas. So if you live in an area where most of your electricity comes from coal, and don’t expect that to change for the next 10+ years (however long you plan to keep the car), then a Prius may be a more environmentally friendly choice than the Tesla.

17

My mistake. I thought the number seemed high.

Except, you have to factor in the extra fuel transportation/distribution step to the filling station for the Prius (most of which are not the plug-in model), so they still come out a little behind.

18

Well, yes and no. That works fine if the pollutants we’re talking about are sulfur oxides, or nitrogen oxides, or ozone. But nobody’s ever come up with a practical way to deal with the number one pollutant, the carbon dioxide.

19

That is not strictly true; there are a number of technologies in various states of development for the direct capture of CO[SUB]2[/SUB] suitable for point of emission carbon capture and sequestration like this one. However, in order to turn the carbon into a form that can be permanently sequestered requires significant energy input that detracts from the net energy output of the plant. And coal is already becoming as or more expensive than natural gas while the primary method for extracting coal (mountaintop removal which replaced the more dangerous longwall mining in the ‘Eighties) has become very unpopular with both conservationists and the people who are directly affected by pollution and landslides. The United States has large reserves of natural gas, and estimates of global natural gas reserves are enormous, so coal (“clean” or otherwise) is going away regardless.

Stranger

20

That’s why I said no practical way. There are plenty of impractical ways to do it.