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Comment by choxi | Hacker News Reader

If 100% of cars on the road (globally) were electric, how much would that impact global warming?

According to the Union of Concerned Scientists, 20% of all emissions are tailpipe from cars. Maybe 30% for all vehicles including trains etc.

That's a significant percentage. If the oil demand drops, theres probably another 5-10% that could reduce.

So we're looking at probably a 30-35% drop in emissions.

As an owner of an electric (recently bought), I'm fascinated by how amazingly agile my relatively-inexpensive Ford Focus is. If everyone drove an electric for a day, many would likely decide to go electric purely for performance reasons.

But you have to account for the fact that much/most of the electricity used by EVs is generated in ways that produce carbon emissions. And even if we specify that it all comes from "zero-emissions" sources there's still an environmental cost that comes with manufacturing, and mining/processing materials, for cars, batteries, wind turbines and solar panels, nuclear and hydropower, etc.

Which is not to say it isn't an improvement, just that it oversimplifies things only to look at one side of the balance sheet.

> much/most of the electricity used by EVs is generated in ways that produce carbon emissions

This is highly dependent on where you live. At the extreme, North Dakota [1] gets 75% of its electricity from coal burning. But in California, the mix is 35% Natural Gas, 25% Renewable, 10% hydro, 10% nuclear [2], so nearly half of the electricity is carbon-neutral. If huge places like California go electric, they will take other places along with them.

But even in the unlikely scenario of a primarily coal-based grid in the future, the efficiency increase that comes from the centralization of combustion at the coal plant (as opposed to in the vehicle) still results in lower well-to-wheels CO2 emissions [3].

[1] http://www.ndenergyforum.com/expert-facts/

[2] http://www.energy.ca.gov/almanac/electricity_data/total_syst...

[3] http://mydocs.epri.com/docs/CorporateDocuments/SectorPages/P...

And can we hope for snowball effect, if cars were to be all electric, maybe people perspective on ecology, green areas, air pollution would change too. Unleashing more desire and efforts into planting trees and plants. Etc etc

>According to the Union of Concerned Scientists, 20% of all emissions are tailpipe from cars.

The only USC source I could find[1] says that 20% of US emissions are tailpipe emissions, but the question was about global emissions. Globally transport makes up 14% of emissions according to the IPCC.[2]

[1] http://www.ucsusa.org/clean-vehicles/car-emissions-and-globa...

[2] https://www.epa.gov/ghgemissions/global-greenhouse-gas-emiss...

I don't know about globally, but in California the carbon emissions from light vehicles are the largest component of the emissions inventory, and the only component that is growing. If entire fleet was electrified and entire grid converted to renewable, that would knock ~25% off emissions.

Including commercial vehicles? It would be a truly significant change, but at this point, probably too little too late. Still, it would be a shocking change, and it would also potentially greatly reduce city pollution around world, reduce deaths and illness from related effects.

http://www.ucsusa.org/clean-vehicles/car-emissions-and-globa...

According to the IPCC, transportation accounts for 14% of global greenhouse gas emissions,[1] and according to the EPA it's 27% of US emissions.[2] Obviously road-based transport is only one part of transport, which also includes ships, trains, and planes.

[1] https://www.epa.gov/ghgemissions/global-greenhouse-gas-emiss...

[2] https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas...

The interesting question, at least for now, is how it would impact air quality in cities. Electric cars are not as eco-friendly as you might think, their production is very energy intensive and currently at least electricity comes in large parts from fossil fuels.

However, inner city air quality is pretty bad, with particulates and NOx killing thousands every year. Electric cars have the immediate benefit that they move pollution somewhere else.

You still get some fine particle emissions from the wear of rubber tires and road surface, and the brake pads. But this might be a small fraction compared to what gas engines emit.

Those particles are much bigger than what the ICE produces, which makes them less dangerous.

This is where EVs also have an advantage because they scrub their brake pads much less.

Power plants are also much more efficient than the thousands of internal combustion engines they'd be replacing. It's still not ideal, but it's better than the current situation, and it's easily improved (to great effect) by replacing coal plants with cleaner sources.

Are they still more efficient if you factor in the whole chain of fuel->wheel rotation? Converting electricity to battery charge, to movement surely shaves off at least 15%.

They are. Remember that you also have to factor in the whole chain of crude oil underground -> wheel rotation if you want a proper comparison. Transporting and refining gasoline isn't free either.

Car engines have pretty bad efficiency. You're looking at something like 25-30% typically, and that's peak efficiency. Car engines usually run well off peak efficiency because they're not at optimal RPM or power output, and then you lose even more when braking. Add on another substantial portion for refining and transport.

A modern power plant can be 60% efficient or more. You lose about 6% in transmission, and then another 5-10% in the rectifier, battery, inverter, and motor.

> They are. Remember that you also have to factor in the whole chain of crude oil underground -> wheel rotation if you want a proper comparison. Transporting and refining gasoline isn't free either.

Do you? I mean... we're still going to refine petroleum if we go to electric cars completely, if only for industrial purposes. Even then I think it's going to be a while before anybody proposes electric passenger jets or electric cargo freighters, so there's still going to be refining and oil exploration. I am not really sure it is correct to assign 100% of the cost of that to cars.

Who said anything about assigning 100% of the cost to cars? You break it down into a per-gallon figure, and use that to assign the cost to cars.

It's the same thing with electrics. You don't assign the entire energy lost in the power grid's wiring to EVs. You assign them the percentage loss on the energy they consume.

To obtain a gallon of gasoline costs a certain amount of energy which implies a certain amount of emissions attributable to that gallon. If you're looking at the entire efficiency of a gasoline car in terms of miles per unit of CO2 emitted, you need to account for that. The same goes for a kilowatt-hour of electricity and accounting for the miles-per-CO2 of an EV.

If you factor in the chain from crude, you also have to factor in the mining and transportation of coal. I don't think that's usually done when calculating the CO2/kWh.

It needs to be if you want to make a meaningful comparison. If you search for the lifecycle emissions of coal you'll find this accounted for. That search will also give you non-zero values for things like nuclear and wind, which is also useful. (Although a bit hard to say for sure, since in a hypothetical world powered exclusively by nuclear or wind, the values would be lower.)

The power generation is far more centralised, meaning economies of scale/size can apply both to efficiency of the generators (they can operate optimally all the time) and to infrastructure around them, e.g. for a hypothetical CO2 capture system, it is almost certainly easier and cheaper to apply huge versions to 100 power stations than to try miniaturise to fit to 100 million individual cars.

~14% of total emissions are from transportation. If there were somehow 100% adoption of electric cars, including replacement of all existing cars on the road, you'd see a reduction of around that amount.

https://www.epa.gov/ghgemissions/global-greenhouse-gas-emiss...

No, you'd likely not see anywhere near the 14% reduction. Electricity has to come from somewhere. In a lot of US states that "somewhere" contains a significant fraction of coal and gas.

This is true, but centralized power generation is a lot more efficient then creating the power individually at the point of consumption like ICE cars do today. I believe that an ICE motor is something like 30% fuel efficient, Electric something like 80-90% and a combined cycle blah blah gas turbine is more like 60-70%. So no, it won't be the full 14% but it won't be a few points either, probably safe to say 5-10% reduction.

That's not safe to say either. I've read that EVs take more energy to manufacture as well.

A very good heuristic is to compare their total $ costs for purchase and use, and then think about what sorts of externalities that doesn't cover. I've found over and over again that $ cost pretty much equals energy and therefore pollution cost, less the externalities. But the externalities are really super important, and of course, engine efficiencies and where in the cycle the energy is liberated from it's chemical bonds is important.

"Transportation" includes ships, planes, trains and trucks. Less than half of that 14% corresponds to passenger cars.

I've gone though this before... If you break this down into passenger vehicles, the percentage gets much smaller.

It really blows my mind. We could replace every car on the planet with zero emissions, and still would put a tiny dent into the total percentage of pollution. We're winding up all these battery factories, spending millions on personal vehicle tech like it'll save the world, and the real majority of the problem doesn't seem to get any focus.

I just feel like it's sort of a distraction to keep us busy ignoring the real problem. It all feels sort of like a farce to me. But then again, I don't know what kind of new regulations and emissions controls are going into factories, ships, etc. I just feel like there probably isn't any regulation on the real polluters. They'll just keep getting tax breaks, while we'll undoubtedly get taxed for driving an old "polluter" car.

I suspect it'd be negligible. You still require a lot of energy for creating and disposing of the batteries, manufacturing the vehicles, and of course charging them. Most of that power (for the time being) comes from non-renewables[1]. I don't have data to back it up, but I suspect that the lifetime energy required to build a fully electric car is still greater than that of an efficient ICE car.

Furthermore, according to the EPA, 27% of greenhouse gas emissions are for transport[2], however there's no breakdown by things like airplanes vs trains vs cars.

IMO, if people really want to 'change the world', we need to shift away from automobiles, consumerism, plastics, and conspicuous consumption. Live close to work, ride a bicycle, stop buying McMansions.

[1]: https://www.eia.gov/energyexplained/?page=us_energy_home

[2]: https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...

We have that breakdown in California statistics and 91% of transport is private cars. Trains, planes, trucks, and off-road equipment is tiny.

Even so, electric cars are still less efficient, so we'd be worse off. There's at least one[1] study (of the batteries for the Ford Focus) which found that they resulted in 39% more CO2 emissions than the ICE version.

[1]: http://pubs.acs.org/doi/abs/10.1021/acs.est.6b00830

That requires you to assume a certain mix of energy used to manufacture the thing.

It reflects the current reality. We're not going to replace everything with nuclear power anytime soon.

True. However, while it is possible to make any kind of car with 100% renewable embodied energy, it is quite impossible to operate an ICE car on renewable.

that study is problematic because while they look at the cradle to gate cost of the electric drivertrain including battery, comparing to the ICE car drivetrain, they don't look at all the cost of Petrol + all the unaccounted for externalities that go into it's extraction and delivery. A good comparison would include the cost of electricity extraction both for the ICE car and the electric and then do the comparison. As it stands, this study tells us that Electric cars are more 'expensive' than ICE cars.

I'm confused by what you've written here.

When you say they "left out the petrol", are you assuming that a better analysis would assume that the petrol is never made in the first place?

I mean, that might be the wish but we don't yet live in a world where the gas will stay in the ground if we don't use it to fuel one automobile at the margin.

I think their point was that it seems unfair to count up all the of the embodied energy of an electric car's batteries, but to only count the potential energy of the ICE car's fuel.

Child has it. The way this study is written, we're asked to compare more or less the carbon impact of an empty gas tank and the battery pack. That seems a bit unrealistic to me. yes the drivetrain is different and therefore more costly, but when it comes down to it, looking at the examples in the paper, the comparison is between the battery pack and an empty gas tank. That seems disingenuous to the broader point of carbon emissions for the entire life-cycle of the vehicles, which presumably would include use.

Which approach is "more realistic" depends on whether you are evaluating the decision between an electric car and a gas car at the margin, or not.

If it's you as a consumer buying the next car to be produced, then it is entirely appropriate to compare it that way, because your single purchase will not change the entire life cycle.

Although the carbon emissions caused by the manufacturing of an electric car is greater than those for a gasoline car, the amount of carbon emissions for the total lifecycle of an electric car are on average half those of a gasoline car [1, Figure ES-2]. This is calculated using the average U.S. grid emission data. In a country such as Norway, where 98% of our grid is powered by hydro, the greenhouse gas emissions during the operation of an electric car is 99% less than that of a 2014 gasoline-powered car [1, Table 1].

The great thing about electric vehicles is that it makes it possible to greatly reduce emissions as the grid is transformed towards a larger share of reusable energy.

Another great trend is autonomous driving, which will enable a reduction in the number of cars by having cars as a service at a lower price. Fewer cars will mean that cars can be built better and last longer, as they can be more expensive. As long as these cars are electric and powered by renewable energy, the potential to reduce emissions compared with the current situation should be large.

[1] http://www.ucsusa.org/sites/default/files/attach/2015/11/Cle...

IIRC the biggest contributor to the transportation's emission are freight ships that cross the oceans. I wonder how they will be solved.. Maybe going all-electric will help people transform their mindset to no-emissions production (since cars live with people, frieghts ships don't), so it could be that this is an important cultural shift.

Oceanic shipping is a big emitter of pollutants that cause acid rain, mostly because its limits on sulfur in fuel are incredibly lax compared to those for cars/trucks. It's not a big CO2 emitter relative to land transportation.

https://www.quora.com/Is-it-true-that-the-15-biggest-ships-i...

It would probably impact city pollution much more than global warming, which means it will also impact healthcare costs (as in reducing them).

It's a good start. But, pollution can still be caused from brake dust and tire friction with the roads. Fixing the housing problem will yield significant gains, as that would reduce extremely long commutes to much shorter ones where people could walk.

Electric cars barely use conventional brakes. So brake dust would be reduced by at least a factor of 3.

That is completely dependent on the energy mix used to generate the electrical power. In case coal is used the effect on climate probably is worse than what we have now.

While it's dependent on the energy to generate, it adds several new possibilities. It's no surprise why Elon wants solar panels, home scale batteries, and electric cars together.

Plus, even if a few dozen coal plant powered electric cars aren't superior to hundreds of millions of gasoline engines burning gas (a point I would still challenge), it's easier to regulate a few dozen coal plants than it is to replace hundreds of millions of cars.

It's funny, the "coal makes electric cars worse" has become a popular anti-EV line from conservatives, but the reality is that the US is only 30% coal (no longer #1 source overall either)[1], electric cars in the US with our electric mix release far less carbon on average [2], and heck even burning natural gas in a plant is cleaner with less ghg impact than millions of gasoline burning engines [3]

[1] https://www.eia.gov/tools/faqs/faq.php?id=427&t=3

[2] https://www.afdc.energy.gov/vehicles/electric_emissions.php

[3] http://www.ucsusa.org/clean-vehicles/electric-vehicles/emiss...

You missed my point. Which is: If and only if the energy production for the EVs will be done through renewable sources, this grand plan works. But in Germany (where I live), we are experiencing huge problems with this approach.

The main issue: Power production fluctuates wildly throughout the year. But you need to have the capacity for the worst case (sometime in winter), which means an enormous surplus of energy in the summer. We cannot store this energy. And all these issues threaten the stability of the power grid.

Shutting down the nuclear power plants hurt us badly regarding the CO2 budget. All of the new renewable energy installations (solar and wind, mainly) have only achieved to offset the loss of the nuclear plants.

Other countries will have the same problems. Solutions are not in sight. It will be much, much more expensive that people now realize. Energy prices in Germany have gone up considerably since the early 2000s, precisely because of renewable energy.

Don't get me wrong, to save the planet this is what we must do. But currently, it is unclear how to do this in a short time, without lowering the standard of life for everyone.

0%, as there is no proof of man-caused global warming.

Manufacturing that many electric motors and (presumably) lithium ion batteries would have an enormous impact on the world, though, in terms of mining and refining the rare metals and elements required for these components. But even putting that aside, and assuming that batteries and motors could be produced for the same impact as combustion engines, the impact would still be zero percent for there is no provable scientific evidence that man is causing global warming. None. There are lots of theories, yes, and loads of simulations, stacks of papers written with funding by government grants, lots of charts & graphs (some with well-documented NOAA 'doctored' numbers), plenty of groupthink in the popular press, etc. but science is not a popularity contest. At one point in time it was settled-science that the world was flat. Groupthink does not equal proof. And it should not be actionable. This lack of proof is the state of scientific knowledge at this time.

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