Comment by danielweber | Hacker News Reader

Comment by danielweber | Hacker News Reader

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What is the comparison between using energy to generate liquid fuels from atmospheric CO2 (which would be carbon neutral) and trying to electrify the entire transportation sector?

Those Los Alamos guys [1] said in 2007 they could get it down to $3.40 a gallon. Okay, maybe they were wrong and/or optimistic. But, still, there is some price point at which it is break-even. What is it? Five dollars? Ten?

The advantages of this over electrifying everything are that we already have built up the infrastructure for liquid fossil fuels. There is no extra engineering to be done for storage and/or transport, and no environmental impact from building new facilities like battery factories or erecting more transmission towers.

In both technologies, you start with an energy source, and then distribute it to consumers who use the product up. Both are carbon-neutral once you get past the "have the centralized energy source" step.

[1] http://bioage.typepad.com/greencarcongress/docs/greenfreedom...

[2] http://www.nytimes.com/2008/02/19/science/19carb.html?_r=0

Where's the electricity coming from? If your answer is natural gas, or oil powered generators, then no, there isn't a price point where it will break even.

Now if you can answer that question with nuclear reactors or renewables of any kind, then your logic probably applies. Yet, I doubt it will ever be the main fuel powering our transportation.

From the linked pdf:

"We have limited our studies to nuclear power because its capital costs are lower than wind and solar-electric power, and it has significant environmental advantages over fossil energy sources, which are not carbon-neutral."

If that (huge) assumption is allowed for this technology, why not EVs?

You can paint a very rosy picture of any transport technology if you assume away fossil fuels.

If I already own a perfectly good ICE car, as most people do, it's much less wasteful to start feeding it synthetic gasoline than replacing the whole car with an EV. And the benefits are immediate.

Edit: Also, the energy density of hydrocarbons is unmatched. Synthetic kerosene could be used to run 747's; battery technology can't do that.

>If I already own a perfectly good ICE car, as most people do, it's much less wasteful to start feeding it synthetic gasoline than replacing the whole car with an EV

Actually this is incorrect. 75% of the energy used by a gasoline car is in the fuel it takes to drive it, and only 25% in manufacturing and disposal.

It's the same situation with incandescent lights. It's mathematically more efficient to throw out a perfectly good one and replace it with something more efficient.

>Synthetic kerosene could be used to run 747's; battery technology can't do that.

http://www.aviation.com/general-aviation/elon-musk-toying-de...

Probably because the existing inventory of ICE based rolling stock has something like a half life of 20 years.

It'd also be nice to have some time in on good carbon sequester techniques in large scale.

The entire point of the question I asked was: given energy source, what is the comparison between 1) sending out electricity to batteries, or 2) creating liquid carbon-neutral fuels.

Why doesn't natural gas count? It's increased usage is one of the key reasons the US's carbon output is down over 10% since 2005.

> "There are two basic factors that have contributed to lower carbon intensity (CO2/kilowatthour [kWh]) in the electric power sector: 1) substitution of the less-carbon-intensive natural gas for coal and petroleum, and 2) growth in non-carbon generation, especially renewables such as wind and solar."

http://www.eia.gov/environment/emissions/carbon/

It's impossible to win with converting a fossil fuel X into something and then to convert back to fossil fuel X, because of basic thermodynamics. If you want to convert fossil fuel X to something to convert to fossil fuel Y, you may be able to "win" over the current situation but you will very likely never get to get zero emissions in the system as a whole, because of the first step. It isn't necessarily impossible to burn X tons of CO2 and pull X+delta tons of CO2 out of the air, depending on the exact binding energies of the chemicals involved (which given that both are fuels, probably don't have an advantageous difference you can exploit), but you'll certainly be paying somewhere else to do it. And given that pulling CO2 out of the air at scale is quite challenging even on its own merits, it probably can't win in a practical manner.

If you're going to pull CO2 out of the air you pretty much have to be using a non-CO2-generating power source to do it if you want to net CO2 withdrawal.

But doesn't this equally apply to fully-electric vehicles as well?

No. Electric cars that charge on fossil fuels face the Carnot cycle loses exactly once, just like internal combustion ones. They are competing on what are details when compared to another cycle.

The back story for electricity is peer grid and arbitrage techniques. Power grid should be just like the internet - every endpoint can produce as well as consume services. Would this allow for grid defection? Don't know, but it will radically change the model for energy economics for sure.

But if you could guarantee that huge energy demand for nuclear reactors, then it would (economically) justify the scale-up that would allow nuclear to power a bigger share of transportation: they could just run at high loads all the time and simply use any excess to produce liquid fuel.

The Green Freedom link was interesting, thanks for sharing.

It looks like the $3.40 number is contingent on some advances in material science enabling more efficient electrolysis. I also think they under estimate the cost of a new PWR nuclear reactor.

An interesting idea related to this: Would high income people pay extra to buy gas from a carbon-neutral gas station? It could be designed and marketed as an environmental/elite gas station (something much better than the usual mini-mart).

Electric cars have an efficiency of about 70-80%, if you count the losses of electrical transmission, charging and the engine. A car engine < 40%, in mixed use about 20%. So even if you could generate fuel from electricity at close to 100% - which you probably can't - the electrical car is way more efficient. And of course, even with synthetic fuel, you have some level of pollution, as no combustion engine is perfect.

Except your electricity has to come from somewhere. If you are in the US, it will most likely be from some kind of hydrocarbon. You are just hiding the pollution, not removing it.

It is much easier to make those centralized power generation sources green than it is to make all of the cars on the road just a small margin greener. If you are in the US then those electricity has rapidly changed from dirty coal to cleaner gas and a growing percentage of renewable over the past decade.

You can make the centrals more efficient (to a point), but you are still burning hydrocarbons. And then you must apply the same electric efficiency as before. There are losses every time you convert the energy.

By the way, "a growing percentage of renewable over the past decade" is disingenuous. From ~9% renewable in 2002 to ~13% in 2013 is "a growing percentage", but not enough to make a difference in the discussion. https://en.wikipedia.org/wiki/Renewable_energy_in_the_United...

This is not green (electric) VS pollution (hydrocarbon). It's hydrocarbon -> electric -> car instead of hydrocarbon -> car. It's modifying a whole distribution network in the hope of achieving higher efficiency.

It's all the way up to 1/8 of all our power? That is definitely enough to make a difference, it means we're within quite minor scaling factors of having it take over.

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