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Comment by scrrr | Hacker News Reader

I was ignorant towards this issue and don't know much about electric cars. But the electricity has to be produced somewhere, right? Transporting electricity isn't free either. What about building batteries? Would we have less emissions if all cars switched to electric? What about other technologies like for example hydrogen?

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Yes. A powerplant is much more efficient in converting fuel to energy than a car engine. A car engine wastes most of the energy on heat. Powerplants usually include systems to capture excess heat and convert it to energy.

There have been many studies done on the effective MPG of a tesla roadster, and of course they differ based on their assumptions, but all of the ones I have seen show the roadster getting over 100 effective mpg.

The hydrogen technology has one big problem. It does not exist. Well to be fair to them, it does exist but not in a consumer product. You cannot buy an ordinary street legal hydrogen car now. But you can get an electric one.

If hydrogen ever takes off it will still have a similar issue as the electric -- the hydrogen would still have to be generated somewhere (usually by taking it from water) and that would require electric power.

Hydrogen does have some theoretical benefits over electric (such as more high density energy storage), but currently electric technology is advancing much faster. It is widely suspected that some of the proponents of hydrogen support hydrogen only as a way to remove support from electric.

We have a cheap and infinite source of electricity, it's called nuke power. The main obstacle to its adoption, as well as the source of its cost, is NIMBYism. That problem goes away once you decouple generation and transmission. Build nuke plants at the ends of the earth and ship huge quantities of hydrogen back to civilization.

Transportation and storage of hydrogen is a problem too. Most metals become brittle when they're exposed to hydrogen. This is one of the big hinderances to using hydrogen as a fuel.

http://en.wikipedia.org/wiki/Hydrogen_embrittlement

Producing the energy is much more efficient, but then to store it in a car battery is inefficient. A good battery is about 60% efficient, which must be multiplied by electricity generation efficiency to get the total efficiency of fuel->electricity->storage->retrieval->motion.

According to an alternative energy researcher's presentation about his research there isn't even enough lithium to make batteries for all the cars, so it's an imaginary scenario.

Napkin calculuation:

A Tesla Roadster has a 53 kwh battery. Assuming 1kg lithium per kwh (a Chevy Volt uses 1.4kg of lithium per kwh [1]) that's 50kg of lithium per car. Assuming that we need around 1 billion cars in the world [2], that's 50 million tonnes of lithium. The total lithium reserve of the world is less that 10 million tonnes [3].

Note that this is not even counting trucks, buses, motorcycles, scooters and all the cars that people in developing countries are going to want, and assuming that we can perfectly recover lithium from old cars.

The researcher recommended power lines on all big roads, and bicycles for the rest.

[1] http://gigaom.com/cleantech/what-the-looming-lithium-squeeze...

[2] http://en.wikipedia.org/wiki/Automobile

[3] http://en.wikipedia.org/wiki/Lithium

Reserves is a kind of dodgy term. Never trust a table stating what the reserves are, unless it's something well-studied like oil (which will have dozens of different charts, depending on what you mean by "reserves"). Like oil, lithium will keep being produced as long as the price keeps rising, as new reserves are found or uneconomic reserves become economic.

It's more a question of price, how quickly it rises, and what the alternatives are.

Unless the reserves turn out to be at least 20x larger than that table, all electric lithium-ion is not going to happen. Are you saying that that table is off by 2000%?

Sure, it's not a fixed reserve but a smooth price curve. That doesn't mean a lot in practice; people aren't going to pay millions to extract every last bit of lithium from the earth. The point is that lithium-ion batteries for cars are most likely not going to be the long term solution. The same applies to solar panels and fuel cells that have rare materials in them by the way.

I could imagine driverless cars reducing the total number of vehicles we need to own as a species by an order of magnitude, perhaps more. That might help.

Just to note that lithium is not like oil: the lithium is not consumed in making the batteries, so if it turns out to be useful it'll be worth gathering even from low quality sources.

Also, sea water is 1-2ppm lithium -- expensive but plenty of it to extract.

Electric cars can run on power from hydroelectric, wind, geothermal, tidal, solar, and nuclear sources, which is enough benefit by itself to switch from ICEs. But even if every power plant burned the same gas we put in our cars, switching would still lower emissions because power plants are more efficient than car engines and transporting electricity is more efficient than transporting gas.

Hydrogen is a dead end IMHO. Fuel cells are expensive and have many limitations, plus containment and transfer are still unsolved problems. Batteries are improving fast enough now (notwithstanding popular sentiment from people wanting Moore's Law speeds) that hydrogen will never catch up.

One of the arguments is that by switching the power source to electricity, we can focus on improving our methods of generating electricity, and everything dependent on it will benefit. For example, if we were able to create cars that could got 1000 miles on a gallon of gas, how long would it take to phase out all existing cars?

One of the most exciting technologies in electric cars is regenerative braking or KERS (Kinetic Energy Recovery System). As the name says: breaking fuels the batteries (some of the solutions don't even use the batteries but are totally mechanical-based, which make them even more 'pure' - there's a Porsche model using that). In hybrid cars the energy could be recovered from the combustion engine heat, exhaust gases heat, etc. I suppose, in future, we'll be able to extract/recover some energy from almost everything (like radio or A/C) making the cars super efficient.

Interesting idea. I wonder what the efficiency gain of using the exhaust fumes with a generator would be vs. that of using it for a turbocharger (the main use of exhaust fume power currently in cars, lets the fuel burn more completely by pushing compressed air into the cylinder).

I wouldn't say that a turbocharger allows fuel to burn more completely, if that's what you meant. A turbocharger uses energy in the exhaust to spin a turbine, which is connected to an impeller, compressing air going into the engine. More air allows more fuel, and together you get a bigger bang in a smaller space - the engine behaves like it's larger than it is, burning more air and fuel then it would otherwise. A turbocharged car can still burn fuel inefficiently, and they often do run rich (injecting more fuel than will be burned) in order to avoid pre-ignition and to cool the cylinders.

From Wikipedia:

A turbocharger may also be used to increase fuel efficiency without any attempt to increase power. It does this by recovering waste energy in the exhaust and feeding it back into the engine intake. By using this otherwise wasted energy to increase the mass of air, it becomes easier to ensure that all fuel is burned before being vented at the start of the exhaust stage. The increased temperature from the higher pressure gives a higher Carnot efficiency.

http://en.wikipedia.org/wiki/Turbocharger

You're probably right that most cars aren't tuned to do that, though.

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