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)

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.

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.

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.

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.

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.

Wonder if this could be done in space? A few months ago I read about the idea of solar energy being captured in space, and I struggled with the question of how to transport that energy to where we'd like to use it.

If the algae could grow in space, and this process could occur in space, then we could wastefully convert solar to oil in space, and spacecraft could use that oil in space.

Lot of if's and speculation there, but it's an interesting line of thought.

I think you'll find radiation to be an interesting additional challenge to add to the mix. That and the relative lack of local oxygen. I get what you're saying though, its a heck of a lot more rational to design and airdrop an algae plant on Mars than to expect oil wells to produce on Mars.

> I think you'll find radiation to be an interesting additional challenge to add to the mix.

Not as much in near-Earth orbit where we enjoy much of the Earth's magnetic field's protection. Astronauts come back with an elevated risk of cancer but not tremendously so.

> That and the relative lack of local oxygen.

Grow some photosynthetic algae too, which'll convert sunlight to oxygen.

I can't tell if you're joking, but photosynthesis rearranges carbon dioxide and water into sugars, releasing some of the oxygen from the water molecules.

And when you burn the algae sourced synthetic kerosene and algae sourced O2 in your rocket engine (or whatever you're doing with it) you'll run out of water. And its dumb to ship unprocessed water up into space if you can use cheap earth based refineries to ship the same weight of highly refined fuel. Keep those heavy refineries at the bottom of the gravity well unless you have a really good reason to hoist them up.

So that was the origin of my idea that this isn't going to scale in space "in general". I'm told Europa has a lot of water, other than the whole lack of sunlight thing, I could see Europa as the "fuel tank of the solar system" in the future. Maybe it could be economically viable to mine comets and turn them into fuel while they're near the sun? Or mine icy asteroids?

I think you're going to overall have more trouble finding water in space than energy.

The problem is that algae is biomass. Thanks to conservation of mass, whatever amount of biomass you bring down from space needs to come from somewhere, and space is famously devoid of mass, let alone anything for algae to consume. That means that the problem of algae farms in space becomes one putting algae food into orbit.

I'm not sure how effective launching literally tons of material into space will be.

Tons is an understatement.

You're forgetting the one plausible energy source, however: the gravitational energy that the biomass has in outerspace. If you could figure out how to capture the energy of millions of tons of material moving from orbit to the Earth's surface, that might be able to provide the large majority of the energy needed to bring it up there in the first place.

I wonder how efficient we could make space elevators.

>> how to transport that energy to where we'd like to use it

I've always thought that a rectenna[1] would be the most efficient way to send power from orbit down to Earth.

> I struggled with the question of how to transport that energy to where we'd like to use it

Lasers

Thus spoke our prophet:

Let me tell you one of my pet peeves: space solar power. Okay, the stupidest thing ever. If anyone should like space solar power, it should be me. I got a rocket company and a solar company. I should be really on it, ya know. But it's like, super obviously, not going to work because, ya know, if you have solar panels - first of all, it has to be better than having solar panels on Earth, so then you say, okay, solar panel is on-orbit, you get twice the solar energy - assuming that it is out of Earth's shadow - but you've gotta do a double conversion. You've gotta convert it from photon to electron to photon, back to electron. You've got to make this double conversion, so, okay, what's your conversion efficiency? Hmm. All in, you're going to have a real hard time even getting to 50%. [The solar cells are better.] It does not matter, put that cell on Earth then. See, that's the point I'm making. Take any given solar cell, is it better to have it on Earth, or is it better to have it on orbit? What do you get from being in orbit? You get twice as much sun - best case - but you've got to do a conversion. You've got to convert it the energy to photons - well, you have incoming photons that go to electrons, but you - you've gotta do two conversions that you don't have to do on Earth, which is you've got to turn those electrons into photons and turn those photons back into electrons on the ground, and that double conversion is going to get you back to where you started, basically. So why are you bothering sending them to bloody space. "I wish I could just stab that bloody thing through the heart." BTW - electron to photon converters are not free and nor is sending stuff to space. Then it obviously super doesn't work. Case closed. You'd think. You'd think case closed, but no. I guarantee it's gunna come up another ten times. I mean, for the love of God.

From: http://shitelonsays.com/transcript/elon-musk-panel-bta-2012-...

I always saw it as a very long-term solution. Once we have the lunar colonies, orbital space stations, asteroid mining, and the economic infrastructure to make interplanetary travel routine, we could begin building out SSP as a practically unlimited source of power. But, for the foreseeable future I have to agree with Musk. Considering how expensive launching stuff to orbit is right now almost any sort of terrestrial solar power coupled with an energy storage mechanism (e.g. pumped hydro, heat reservoirs for solar thermal) would be more cost-effective.

Isn't the point of solar in space, well, space? You get less efficiency, but you are not going to run out of deserts nearly as fast. So the ultimate scale is not limited.

Are we really running out of deserts anytime soon? Isn't the issue more the capital and labor intensity of harvesting energy from sunlight, and transporting that energy to places that actually need it?

Space exacerbates those two issues.

Can't we skip the conversion and use giant optical lenses to focus sunlight onto panels on earth? ;)

No, that doesn't work since the sun is not a point source.

Maybe it doesn't work for lenses but it seems it would work for mirrors: http://www.academia.edu/5185260/SUNBEAMS_FROM_SPACE_MIRRORS_...

Thanks for the good link!

Ok, here they produce 1-sun intensity by having a 10 km mirror at 1000 km height, focusing on a 10 km terrestrial array.

That's a similar angular diameter, 1/100, as the sun, so from the receiver's point of view it can appear as powerful as the sun. I'm surprised that the numbers work out like that.

Maybe you could create a huge "death ray" constellation with 10x solar intensity and whose ground track (all sats in the same ground track) was filled with liquid cooled solar panels. Over the ocean it would just kill everything in its path.

Nuclear. You want to generate a lot of heat and you don't have geothermal energy handy, you go nuclear.

You could make the whole facility mechanical - the heat from the reactor is used to heat the algae and use steam-driven pumps to create the pressure. Eliminate the electrical middleman.

You need a fair amount of hydrogen gas to run a hydrocracker, which is basically what this is. Industrially you get the hydrogen from natgas. Yeah yeah you can get methane from the output of a hydrocracker and hydrogen from methan but depending on the process its net overall hydrogen negative (think about it, how are you going to split a long chain hydrocarbon that has two H ends into two little ones thus a net of 4 H ends without a continuous input of hydrogen?)

So yeah you're mostly right but never going to get away from maybe 5% to 10% capacity driving steam turbines to electrolyze water and run the (insecure, of course) SCADA and hotel load for the humans running the plant etc.

A likely plant would look like two nuke generating plants backing each other up and 18 nukes cooking algae into diesel, roughly.

That's actually a cool idea. A nuclear plant that generates petroleum products! There might be power left over to feed into the grid, too.

I'm sure environmentalists would have a field day with this concept.

We just need cheaper and safer nukes (LFTR!)

http://dotearth.blogs.nytimes.com/2008/02/13/federal-lab-say...

The algae farms should make it carbon-neutral, at least.

Forget the energy content; there are already tons of uses for petroleum that don't require burning it for fuel.

So just get rid of the internal combustion engine...Surely that energy could be used in a more efficient way - such as filling up batteries for electric cars, and then power 10x more electric cars than oil-based cars.

Using algae to make ethanol seems a much easier way to go and uses little energy eg. algenolbiofuels.com