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Wednesday, August 01, 2007

Hydrogen vehicles - fair and balanced

The original post linked to a fairly biased article (reflecting to some extent my own skepticism) and we've seen the reply from Curly. So what's the real scoop on hydrogen for automobiles?

How it works
Hydrogen would most likely supply a fuel cell, basically generating electricity to power a vehicle. A fuel cell is like a battery that carries a recharging source (hydrogen, in this case), so it's range can potentially be greater than simply a battery powered car.

The efficiency problem
The primary means of getting hydrogen - which does not occur naturally - is to use electrolysis to separate water into H and O2 (many proponents believe nuclear power will supply the electricity). This process is only about 30% efficient, so 70% of the electricity used is lost in the process. If that electricity instead went right into a battery for an electric-driven car, we don't lose that energy. Zfacts has a nice illustration of this:
Here are two ways to drive on wind power.
1. Wind => electricity => Battery => motor turns wheels
2. Wind => electricity => hydrogen => Fuel Cell => motor turns wheels
Hydrogen just adds an extra step. And if you've seen Who Killed the Electric Car, you know that we can already produce an electric vehicle to serve most American drivers.

The supply problem
As noted, hydrogen doesn't naturally occur in a harvestable form (unlike oil - our primary vehicle fuel). Hydrogen must be extracted electrically (from water) or chemically (from natural gas). The latter means pointless dependence on fossil fuels, so let's focus on the electrical derivation. A lot of people note that we can eventually electrolize water to get hydrogen using renewably-generated electricity. But less than 10% of U.S. power generation capacity is currently renewable (and only a quarter of that is non-hydro). That's not counting the additional electricity we'll need to generate to make hydrogen.

On the other hand, an electric car can be powered off the existing grid. In fact, some studies have shown that it would be possible to convert almost every American car to electric without having to substantially expand electric generating capacity by simply charging cars during off-peak hours (at night). From Celsias:
A new study for the Department of Energy finds that “off-peak” electricity production and transmission capacity could fuel 84 percent of the country’s 220 million vehicles if they were plug-in hybrid electrics.
To be fair, a plug-in hybrid still has a backup combustion engine. But the gasoline reductions are still dramatic:
According to EPRI (Electric Power Research Institute), half the cars on U.S. roads are driven 25 miles a day or less. Consequently, a plug-in hybrid with a 25-mile all electric range could eliminate gasoline use in the daily commute of tens of millions of Americans.
The Size/Weight Problem
From Zfacts again, the problem with hydrogen fuel cells compared to conventional batteries:
The advantages of fuel cells might be that they hydrogen tank and fuel cell combination needed to drive 300 miles could be smaller cheaper and lighter than a battery pack needed to drive 300 miles. Right now, it's the other way around. (emphasis mine)
And every pound needed to move the car uses more energy.

The Infrastructure Problem
As Curly noted, hydrogen filling stations are the chicken/egg problem. Do you build thousands of stations first and then wait for cars to show? Or do you get a critical mass of cars? Such investments aren't cheap in any case. This study estimated it would cost between $100 and $500 billion to create the fueling infrastructure.

Contrast that with electricity, which is already present at every existing filling station in the country.

Summary
There are two major reasons why I'm a hydrogen opponent:
1) It takes resources away from readily available solutions to consumption of foreign oil and carbon emissions. Plug-in electric and then all-electric vehicles can be powered off existing electric capacity and the technology is already commercial.
2) It's outrageously expensive/wasteful. Even if we only need to convert 8-10% of filling stations to hydrogen to get critical mass, it would eventually require that we convert all stations. That's a big waste when we already have electricity everywhere. We also lose energy converting water to hydrogen with electricity, when we could use the electricity directly.

1 comment:

fine then, "curly" ... said...

I think that the tone of the previous article got me a bit riled up. I haven't read anything by this guy before, so maybe he's also in favor of electricity-as-solution like you are, mr. jff.
What I read was 'Hydrogen is not feasible, so status quo!' I never noticed him tip his hat towards electricity, nor wag his finger at non-renewables. In other words, all I saw was negativity, with no invitation towards a positive change (except a slight final nod towards hydrogen in large corps.)

Now, electricity is great. I want me an electrical hover car. I guess the next question I'd have on electricity vs. hydrogen relates to safety hazards in it's storage. What are hazards with electricity storage (batteries) vs hazards with hydrogen storage in fuel-cells? I'm pretty sure if you hit a gas-powered car hard enough, the sucker blows up ... what happens when you hit a battery-powered car? Battery acid? Is it caustic? What about hydrogen fuel-cells? I have no idea, seriously.