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Comment by AndrewDucker | Hacker News Reader

But is it better than turning that geothermal energy into electricity and transmitting it to a battery in an electric car?

Edit: To be clear, I'm not saying there isn't a need for oil. Just wondering what the efficiencies are for each route, and whether this process means that we don't even need electric cars any more (doubtful, but I thought I'd ask)

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Gasoline has tremendous energy density compared to other forms of storage. If you need that energy to be portable (like in a car or truck), you may still want to use petroleum. http://en.wikipedia.org/wiki/Energy_density

Right, but that doesn't mean anything when we're only getting ~16% efficiency in our ICE.

It means a lot. The Tesla Model S (a reasonable sedan) needs 85kwh to reach a 300+ mile range, and the drivetrain is probably about as efficient as electric cars will ever be. So realistically, we need 85-100kwh of power on board a reasonable car.

A single gallon of gasoline is ~33kwh of power. At 30mpg (easy for a sedan), 10 gallons (330kwh) is sufficient for a 300 mile range. So the Tesla is ~4 times as energy efficient as internal combustion, and unlikely to get any better.

Good thing we have been doing better than that for some time now.

>The MAN S80ME-C7 low speed diesel engines use 155 grams (5.5 oz) of fuel per kWh for an overall energy conversion efficiency of 54.4%

>The efficiency of a combined cycle gas turbine system can exceed 60%.

http://en.wikipedia.org/wiki/Diesel_engine#Fuel_economy

In fact, it's shameful how underutilized diesel engines are in this world. Same with stirling engines.

If you're allowed any scientific process regardless of engineering challenge and economics, thermally crack the crude down to hydrogen and pure carbon coke deposits, sequester the carbon for carbon credits, and pipe the H2 into fuel cells for near 100% efficiency.

(That's a marine engine though. Larger engines are more efficient.)

Maybe so, but 16% is misrepresentative of ICE's as a whole.

Gasoline is still way ahead. It still has ~40x the density of batteries. Even at 16%, it's still going to be about 6x as efficient as batteries, even if batteries + electric motors are at 100% efficiency.

A Toyota Camry car carries 17 gallons of fuel, which, at 6 lbs per gallon, is about 100 lbs. At 28 mpg, that's enough to travel 476 miles. The Tesla S carries a 900 lb battery which is enough to travel about 250 miles. In miles per lb, that's 4.7 for the Toyota, and 0.28 for the Tesla.

Obviously, there are a lot of other considerations than just miles per lb, but gasoline's energy density and portability are stellar.

Cars and trucks can easily be powered electrically, if the need arises (by frequently changed batteries, by induction, or as in trolley buses or trains)

I think planes, rockets and various military applications (e.g an infanterist carrying a zillion gadgets that have to be powered for hours) are the only examples of cases where this process might be beneficial.

It's basically time-shifting. Either you can turn this geothermal energy into electricity and have the consumer charge their car at home over a long period of time (hours) or you can turn it into a full tank of gasoline over a long period of time (hours), ship it to the consumer to fill their tank in a short period of time (minutes).

Either way, it takes a long time. The difference is the impact to the consumer of converting it to something useful for them (gas), or having them convert it to something useful (a charged battery). The consumer doesn't notice the gasoline taking a long time, to them it takes minutes.

Sure, that's better in the few scenarios when it is reasonable to do so. But electric engine technology is still very limited, and we're a long way from replacing all internal combustion engines with electrical. I doubt we'll seeing transatlantic passenger flights in electric airplanes any time soon.

The other huge advantage with oil is that it is a very efficient, stable and easy to transport store of energy. Transporting and storing 1MWh worth of energy using batteries is a serious undertaking compared to transporting and storing the equivalent in oil.

I'm petty sure I'm being pedantic, but to be clear: Electric engines (motors) are great. Highly efficient, simple, powerful, scalable both ways, and reliable. If you've got electricity available and want things to move, they're the way to go.

It's the batteries that are sub par, in many ways.

That's exactly why diesel locomotives have always been diesel generators connected to massive electric motors; the best of both worlds.

not just locomotives. the biggest earth-movers in the world are all electric vehicles powered by onboard generators.

http://www.wired.com/autopia/2013/10/worlds-largest-dumptruc...

Because you know what happens when you try to pass immense torque through a transmission? Bad things. Its why Elon fought for so long for a 2-speed transmission on the Roadster before giving up and opting for a lower top speed. Electric motors have a ridiculous amount of force they can put out.

http://en.wikipedia.org/wiki/Tesla_Roadster#Timeline

"Subsequent to completion of production car number one at Hethel, the company announced problems with transmission reliability. The development transmission, with first gear enabled to accelerate 0 to 60 mph (0 to 97 km/h) in 4 seconds, was reported to have a life expectancy of as low as only a few thousand miles. Tesla Motors' first two transmission suppliers were unable to produce transmissions, in quantity, that could withstand the gear-shift requirements of the high torque, high rpm electric motor. In December 2007, Tesla Motors announced plans to ship the initial Roadsters with the transmissions locked into second gear to provide 0 to 60 mph (0 to 97 km/h) acceleration in 5.7 seconds. The first production car was not delivered with this interim solution; P1 has both transmission gears enabled. According to the plan, the initial transmissions were to be swapped out under warranty when the finalized transmission, power electronics module (PEM), and cooling system became available. The EPA range of the car was also restated downward from 245 to 221 miles (394 to 356 km). The downward revision was attributed to an error in equipment calibration at the laboratory that conducted the original test"

DISCLAIMER: Tesla's final solution was a single-speed gearbox, combined with software and energy management upgrades. The electric motor will now run as high as 14K RPMs to achieve it's 125mph top speed while retaining it's 4 second 0-60 time.

I think you mean 4 second 0-60 time. A 4 second 1/4 mile would be a world record.

Thank you! Corrected.

Yes - if you don't have an electric car. Or if you're somewhere in Siberia at -40 degrees C where a) batteries stop working and b) you're 500km away from a power line.

If you don't have an electric car, it's probably cheaper to buy one than to pay for the gas made by this method, no?

That may work for cars, but not airplanes. And oil is also an important lubricant and plastic feedstock.

And a feedstock for herbicides, pesticides, (some) fertilizers, or on a meta level above those, its a feedtock for "human food".

Of course you could eat the algae straight, or feed it to hogs and then eat hogs, but variety being the spice of life its a perfectly valid alternative tech to turn sunlight into food.

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