ZEV zero emission vehicles

The tree huggers, politically correct bureaucrats and politicians want the industry to offer us “zero emission” cars, at gunpoint if necessary.  This is one of those save-the-world proposals that does not have a snowball’s chance of succeeding.

First, electricity is not free, you have to make it, and that means fossil fuels, because those same tree huggers already stopped us from building safe, clean, fission power plants.  Instead they have us chase such chimera as hydrogen, solar power (economical only for isolated locations), and fusion (unproven except for nanoseconds), but I digress.  Every highway vehicle not tethered to a fixed route must carry it’s own energy supply.  We operate in an oxygen atmosphere therefore the vehicle need not carry its oxidizer, only the fuel.  This is fortunate, because the typical reaction involves 16 pounds of oxidizer for every pound of fuel!  Excuse me, 16 politically correct grams of oxidizer for every politically correct gram of fuel.  A  zero emission vehicles (ZEV) unfortunately, must carry not only the equivalent of 100 pounds of fuel to make a reasonable trip, but also the 1600 pounds of oxidizer (or other reagent) to react with the fuel, which they then can convert to 1700 pounds of reaction product to carry back to the recharging station.

Now, modern engines are about 25% efficient (35% if they are diesel).  The zero emission vehicle since it needs to carry 17 times as much propellant, (fuel plus oxidizer) must be at least 17 times as efficient to compete.  Let’s see, 17 times 25% is 425%.  That is to say for every kilowatt-hour used to charge the battery the motor must be able to do over 4 kilo-watt hours of work.  Am I missing something here?  No, I'm not.

I was explaining this to an electrical engineer.  He stopped me, momentarily, with “I’m not convinced the same limitations apply.”  He was sort of right.  In practice, ZEV is even less practical.  It takes a thousand pound battery pack to store as much energy as four pounds of gasoline, and it has to carry those 1,000 pounds all the time. (Not yet 17:1, but so far only 200:1)

 For the ZEV to hope to compete, it must have a propulsion system that can put out four times as much energy as what we put in.  If we could do that, it could charge its own batteries and would never have to recharge, perpetual motion.  Not only that, but we could use that technology to build power plants that put out four times more power than the fuel they use.  We could then cascade these, each one driving one four times as big and we could power North America with a single candle.  Better yet we could just tap a candle’s worth off anywhere in the system to power it.  Wow!  I hope you see I’m being facetious.

Meanwhile back here on planet Earth, the best fossil fuel power plant is about 42% efficient, so to get that one kilowatt we had to burn the equivalent of 2.3 kilowatts of fuel.  Even if the ZEV were perfect, 100% efficient that kilowatt-hour of stored energy would weigh 17 times as much as a kilowatt-hour of stored fuel.  So it could compete with engines that were 6% efficient.  Look out James Watt, the original one, 1736-1819, steam engine, teakettle, you know.

It would obviously be more productive to look for a way to take the reaction products out of the air, than to attempt to carry them around and reprocess them.  We could have huge un-power plants that take carbon dioxide out of the air.  Plants that absorb carbon dioxide from the air and turn it into something useful, like, umm... wood.

“Hydrogen,” I hear you crying, “hydrogen is the fuel of the future.  Fuel cells can turn hydrogen directly into electricity and the byproduct is pure water.  Hydrogen is the answer, not batteries, not only that, but hydrogen is the most abundant element in the universe, we’ll never run out.” 

Here’s a buck, go buy me some.  Sure it’s abundant, but it’s all being used.  Most of it is busy being water.  The rest is tied up in organic compounds, such as, uh, oil.  Just like electricity, before you can buy hydrogen someone has to make it and making hydrogen requires … electricity.  Yes, hydrogen is the fuel of the future, and it is every bit as promising today as it was 30 years ago.     

OH DEAR MY BAD

When I wrote this, about 15 years ago I made a mistake. I do not feel too bad, because over 100,000 people have seen it and nobody corrected me.
The air fuel ratio is 16:1, but the air is only 20% oxygen, so the oxydizer to fuel ratio is more like 3.2:1
SO

 A  zero emission vehicles (ZEV) unfortunately, must carry not only the equivalent of 100 pounds of fuel to make a reasonable trip, but also the 300 pounds of oxidizer (or other reagent) to react with the fuel, which they then can convert to 400 pounds of reaction product to carry back to the recharging station.

Now, modern engines are about 25% efficient (35% if they are diesel).  The zero emission vehicle since it needs to carry 4 times as much propellant, (fuel plus oxidizer) must be at least 5 times as efficient to compete.  Let’s see, 4 times 25% is 100%.  That is to say for every kilowatt-hour used to charge the battery the motor must be able to do over 1 kilo-watt hours of work.   Since nothing is 100% efficient this still explains why the best electric cars have half the range of the average conventional car. Limited, but practical for many applications, like Honolulu.  And maybe some day just as good.