More "Miles Per Acre" From Bioelectricity Than Ethanol

CarnegieScience writes "Scientist calculate that, compared to ethanol used for internal combustion engines, bioelectricity used for battery-powered vehicles would deliver an average of 80% more miles of transportation per acre of crops, while also providing double the greenhouse gas offsets to mitigate climate change."

Comments

Oy.

[schmidt349]

The problem with using biomass to generate electricity to run cars is that you've got to get the electricity into the car and store it there, usually in a lithium-ion battery. That whole process probably diminishes your efficiency by an order of magnitude. If this guy's taken all that into account, well, so far so good. But I think we're going to need literally quantum advances in energy storage technology (think molten salts and carbon nanotube supercapacitors) before we can get fossil fuels completely out of our transportation system.

The real advantage of producing ethanol right now is that you can just mix it into gasoline and sell the combination fuel (E85) for use in most post-2004 model year cars. It doesn't require a total revamp of the energy distribution network for vehicles.

Re:Oy.

[Kjella]

But I think we're going to need literally quantum advances in energy storage technology (think molten salts and carbon nanotube supercapacitors) before we can get fossil fuels completely out of our transportation system.

True, but if oil becomes very expensive and electricity very cheap but batteries still expensive, there are many ways to extend electrics and hybrids. Imagine long-distance lanes where the car is more like a one-car train driving "on the grid" only using the battery at intersections (to avoid the heavy crossings) and where you exit with full charge to get to your final destination. That would increase the range and possible user base hugely, you could actually take fairly long trips where such lanes exists etc. We manage it for electric trains and trams so I see no reason why we shouldn't manage it with cars. Will it work today? No. But give it another 50 years when we've REALLY exhausted most of the natural oil resources and things will change.

mpg is 1/d^2, mpa is 1/d...

[jeffb (2.718)]

...now all we need is a fuel that comes in the form of a long string, and we can finally express fuel efficiency as a dimensionless number.

BTW, 20 miles per gallon works out to 3.4409911e+10 inverse acres. Or, to look at it another way, one gallon per 20 miles is 2.9061395e-11 acres, or about 0.12 square millimeters. That's the diameter of the imaginary thread of gasoline that your vehicle is gobbling, Pac-Man-like, as you drive down the highway.

Drop in replacements

[LordKazan]

We can get fossil fuels out of our energy system right now with drop in non-fossil replacements like Algal Oil [ see my discussion of it in this thread http://tech.slashdot.org/comments.pl?sid=1225951&cid=27864987 ]

Those who say it cannot be done...

[Judebert]

I'm driving a home-converted electric car right now. I didn't even choose my components for efficiency, and according to my kill-a-watt meter, I'm still running more than twice as efficient as an internal combustion engine.

There have been several studies comparing overall efficiency, including power transmission losses. The EV wins every time.

Re:Pretty low standards Corn Ethanol

[Rei]

The real blow-it-out-of-the-water numbers are when you eliminate "bio" from the equation, period. Corn yields 300-450 gallons of ethanol per acre. Sugarcane, about 550-850 gallons or so. Switchgrass can theoretically yield over 1000 gallons per acre and algae 5000, although those numbers are likely to get way smacked down by reality (especially the algae numbers). But let's just go with them. CAFE average is ~24mpg, and you get less mpg on ethanol, but hey, let's just say our cars get 40mpg. The average driver goes 12k miles per year, so corn can support 1.3 drivers/acre, sugarcane 2.3 drivers/acre, switchgrass 3.3 drivers/acre, and algae a way-over-optimistic 16.7 drivers/acre.

A compact linear fresnel reflector solar thermal generating station produces about 1MW nominal capacity for every 4 acres and has about a 20% capacity factor (in non-optimal sites). That's an actual MW per 20 acres, or 488,288,000Wh/acre-year. The Volt and Tesla Roadster both use about 200Wh/mi, so let's go with a more pessimistic 300Wh/mi after losses and with less efficient designs. That's 121.7 drivers per acre. I.e., it beats the pants off even the highly speculative numbers for algae. And it uses no water or fertilizer -- and we use *way* too much water as it is.

If you want land efficiency, converting the sun directly to electricity and using that electricity directly rather than having the intermediary stage of "plants" is the way to go. And we farm too darn much of this planet as it is already.

Re:Pretty low standards Corn Ethanol

[john.r.strohm]

Of course, the obvious NEXT questions are annoying things like:

1. What kind of numbers do you get with nuclear and/or fusion reactors, instead of biomass reactors or cornfields?

It is worth mentioning that the MIT Nuclear Engineering senior project recently was the engineering design of a fusion reactor to produce hydrogen for automotive fuel. One of the reasons given for producing hydrogen rather than electricity is that we don't have anything remotely resembling a power grid in the Northeast that could handle the output of a commercial-size fusion reactor.

And their design was apparently conservative: you could build it, starting TODAY.

2. How do you distribute the electricity from your biomass reactor or your solar field to the cars? See previous paragraph about power grid issues.