Top Gear - S12 EP7 - 14th December, 2008 - Discussion
 

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ROFL! Gotta feel for the Morris Morina owners club after this one :-D

I thought James May did a brilliant review of the FCX clarity, he makes it seem almost like a good buy, but... I have not seen hydrogen fueling stations anywhere in NJ, second, and please bear with me you chemist and environmentalist freaks, if Hydrogen is the most abundant thing in the universe and you can even get it with a few solar panels and tap water... why in the living hell do I have to pay through the nose for it? if this thing was cheap enough I may consider it

on to the tesla test, I just knew this would happen, pretty good car, overpriced and battery power still needs to come along for it to be reasonable

More than a few solar panels, more like a solar garden if you want to fuel your car that way.
It takes 20 to 100 square meters with cheap panels to produce a kilogram of H2 per day, depending on the latitude (within US; for most part, 20 to 40).

Assuming you normally drive 12,000 miles a year, and the car is an efficient fuel cell hybrid, you'd need 200-250 kilos a year, somewhat less than 1 per day.

Still, such a solar garden is going to cost as much as the car itself, or more if you account for the electrolysis hardware, the compressor and the tankage.
Less space is required with more efficient solar panels, but they cost more.


Actually hydrogen today only costs about $2.5 per kg, which is roughly equivalent to an Imp. gallon in energy capacity. So it's around as much as gas, plus-minus depending on oil and natural gas price.

The cost would be higher if it was electrolyzed rather than extracted in petrochemical processes as today.

the biggest problem when looking at hydrogen as your fuel of the future is that it's terribly energy inefficient.

i will summarize some points that i found while reading my chemistry book:

at first glance hydrogen can produce a massive amount of energy per mass unit 120 MJ/kg that's really impressive and about 3 or 4 times better than petrol. but when we are talking about fuel in a car we have to look at how much energy it can produce per unit of volume and here hydrogen puts out a measily 2.8 GJ/m³ (that's 1000 litres) at 35 MPa in its gaseous state. (i don't have the exact number for petrol here as it's not written in the text, but when i look at the graph i have it's about 1/10th of petrol)

when hydrogen is a liquid things look a bit better, where we have about 8.5 GJ/m³ but that means cooling the hydrogen to 20 K (that's -423 °F and -253 °C) which takes in itself a huge amount of energy.

all numbers are taken from Housecroft and Sharpe, Inorganic Chemistry 2nd Edition (german version)

now the biggest problem probably is obtaining the hydrogen... the easiest way to obtain it is splitting water into Oxygen and Hydrogen. sounds good eh? but then you have to realize that this process needs energy too and in the end we are just recombining the 2 elements to form water again.

so the energy we invested in the first place will be produced again when burning the hydrogen so we end up neither gaining nor loosing energy. which is not very efficient right?

so in the end i think i will have to quote what nthfinity said once on this board (sorry i don't know the exact wording but it went something like this) "the future of transportation is not the car it will be something completely and radically new."

well sorry for being a freak but if something is the most abundant thing it doesn't mean that you can just pick it up lying around on the street.

as James said "it always sticks to something"

this is just a not complicated way of saying that hydrogen is an extremely reactive element and thus can only be found entrapped in a chemical bond with a different atom or whatever you like.

for example petrol or gas is just carbon with a huge amount of hydrogen in it. C6H14 - Hexane has roughly speaking 2 hydrogen atoms per Carbon atom. so now you can say that in oil (this is just an example) hydrogen is the most abundant element in petrol (petrol is made up of over 100 different alkanes (that's what you call these carbon chains with hydrogens attached to them))

so basically being ignorant and asking for a low price jsut because something is abundant is not going to get you anywhere, because you will have to pry the hydrogen out of it's already existing chemical bond.

hey if you have read until here then congrats to you :)

There is that issue, but it's not as big as it seems. A modern midsize car has at least 150 of total volume. Each cubic foot being 7.5 gallons, a 20-gallon fuel tank is just about 3 cubic feet, 2% of the car.

1/10 is about right. So if you had the car using compressed H2, the tanks would take 12% to 20% depending on the pressure (there are 70-MPa storage tanks on the market).
But then a 20-gal tank is for a 600-mile range, which you don't really need. These 20-gal tanks are there only because it costs very little to enlarge the tank. With half that capacity, the tank will take just 6%-10% of the car. It's not a big compromise.

Of course, tankage weight needs to be worked on, so that this tank doesn't weigh 200kg.


Yes, LH2 is pretty much out of the question for civilian non-aerospace applications. Energy loss is just the smaller of the problems. A bigger one is when you spill some LH2 on your car and it cracks apart there, due to a thermal shock. Or when you're about to drive after spending a week on an air trip, and find out the tank is empty, because LH2 has all evaporated... so you have to call a special emergency refueling vehicle.

OTOH, the military is already interested in liquid hydrogen. Fuel cells are not necessary. And cost is less of an issue there.


Actually the easiest way is steam reformation of natural gas. Electrolysis only sounds easy.


It's the same way with batteries. Of course there's no perpetuum mobile. We're running out of cheap portable fuel (oil), it will have to be central power plants (at first coal, later probably nuclear, by 22nd century possibly fusion), and simple power carrier.

http://www.blogcdn.com/www.autoblogg...kson_tesla.jpg

LOL ....someone is desperate for customers.

Yet another reason never to cite Top Gear as a factual source.

Actually, I was pretty convinced they faked the "running out of power" even when watching this.

It's not the first and not the second time Top Gear plays that scene.


The comment about 16 hours is somewhat ambiguous. It's 16 hours if you have the most basic household wiring, not designed for an electric stove, multiroom AC, or other high-power amenities. However, if you install some higher-amperage wiring, which costs between $100 and $300, then you can indeed recharge an electric car quickly, probably in the 3.5 hours he quotes.

you're right, range isn't much of a problem. it just goes down to the weight and how to find safe ways to store the hydrogen in a car when it crashes, oh the horror if actually one would explode. basically no chance of survival.


but that's completely beside the point. as with the natural gas it isn't "emission free" as you would like to have it. when you are reforming it you have CO2 emissions. so it isn't really "green"

i was simply saying that it wasn't an elegant way to solve the problem ;)