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Hydrogen vehicles aren't too eco-friendly in terms of carbon emissions, according to an in-depth new study.  (Source: Web Wombat)
Study indicates plug-ins feature a lower emissions life than gas vehicles, but hydrogen vehicles feature greater emissions

The hydrogen vehicle movement appears stalled.  The push to use the diatomic gas as auto fuel never exactly made it off the ground due to a lack of infrastructure -- production, distribution, and storage facilities.  However, for a time automakers like Toyota and Honda were pushing ahead with testing of hydrogen fuel cell vehicles. 

Even this year, news leaked that GM was considering launching a commercial fuel cell vehicle in 2015, despite lack of support for the hydrogen movement from U.S. President Barack Obama.  However, of late, the big automakers like Toyota and Honda have backed off the effort to push hydrogen vehicles onto the market.

A new study might put another road block in front of the prospect of a near term commercial hydrogen vehicle release, while giving the plug-in vehicle movement a nice boost.  The study was authored by Ryan McCarthy at the University of California, Davis and published in the Journal of Power Sources. The ground-breaking study, entitled "Determining marginal electricity for near-term plug-in and fuel cell vehicle demands in California: Impacts on vehicle greenhouse gas emissions", examines the emissions impact of hydrogen and plug-in vehicles versus their gas counterparts.

Lowering carbon emissions to fight warming, along with high fuel prices and global-political instability, has been a key driving factor for the adoption of hybrids and alternative fuels.  The new study, though, judged hydrogen vehicles to be an utter failure at that objective, in their current state.  The study concluded, "All of the pathways except for [fuel cell vehicles] using hydrogen from electrolysis reduce [greenhouse gas] emissions compared to ICEs and [hybrid electric vehicles]."

It doesn't dissuade further research into hydrogen vehicles; it simply indicates they are unlikely to be ready for showtime anytime soon.  It points out that steam methane reforming is a promising emerging method of hydrogen production that may one day allow hydrogen driven vehicles to actually live up to their emissions promises.

In the near term, the study finds that plug-in electric vehicles are the best option in terms of lowering carbon emissions.  Despite using electricity mostly generated by "relatively inefficient steam- and combustion-turbine plants" the well-to-wheel carbon impact of EVs is still significantly lower than hybrids.

While by no means the definitive study on the topic, the new work does much to fill in the gap in knowledge about what exactly the true impact of green vehicles are.  While the topic of on-the-road emissions has been well researched, there's been much less progress in examining the full lifetime impact of vehicles.  Now, that lifecycle has been examined in depth and EV advocates can put another feather in their caps, while hydrogen advocates are once again handed another setback.

The study may play a crucial role in forming the policy of California's Low Carbon Fuel Standard, an effort to reduce the carbon impact of transportation.  And given that President Barack Obama's Environmental Protection Agency has embraced California's emissions policy, the new study could have a profound impact on the course of regulations and the auto market nationally, as well.



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RE: electrolysis...
By Hoser McMoose on 1/2/2010 10:32:33 AM , Rating: 2
quote:
Shouldn't this also be true for electric vehicles? Electricity powers the car or makes the hydrogen that powers the car.

The difference is in the efficiency of things. A Li-Ion cell can manage better than 95% charge/discharge efficiency, so you're losing VERY little power from your wall socket to your wheels.

With hydrogen and electrolysis from water you're only about 60% efficient, so you're taking a big hit there. Then you put that hydrogen through a fuel cell that, optimistically, might be 70% efficient (current hydrogen fuel cells are at about 50%). So wall-socket to wheels you've lost more than half your energy.


RE: electrolysis...
By Solandri on 1/2/2010 2:58:17 PM , Rating: 4
Thing is, in the grand scheme of things, neither is a very efficient means of converting energy into transport. If that's what we were primarily worried about, we'd all be using trains and subways (rail is super-efficient for transportation, easily exceeding 10x what a car can manage in energy consumed per passenger-mile).

Hydrogen is competing as an energy storage medium. Even with all the problems of compression and lower efficiency, 400 lbs of hydrogen storage gets you a lot more energy (and thus range) than 400 lbs of Li-ion batteries. Measured by weight or volume, batteries absolutely suck as an energy storage medium. They Chevy Volt's 375 lb. battery gives it a whopping 40 mile range. You can go 40 miles on ~10 lbs of gasoline with a 25 mpg car. Current hydrogen storage systems would (after efficiency losses) yield the same range with about 25-50 lbs of fuel + storage equipment.

This is why I keep harping on the difference between energy for static applications vs. for transportation. For static applications, efficiency is usually your primary concern. For transportation, energy storage density becomes much more important since you have to carry your energy with you. The Volt's battery is basically a 375 lb. monstrosity designed to carry around less than $1 worth of electrical energy. Yeah gasoline is 3x more expensive per unit energy applied to the road, but it weighs nearly 40x less. Other technologies encounter similar problems, e.g. CNG, where a tank which stores enough methane to give your car a 150 mile range fills your entire trunk.


RE: electrolysis...
By Penti on 1/7/2010 11:47:46 PM , Rating: 2
Actually the acceptable figure is 25% grid-to-wheel efficiency. 70% for hydrolysis, 90% for compressing the hydrogen, 40% for the fuel cell. This is not something new, we already knew all this.

Adding in a fossil fuel powered power station for this makes it extremely bad, even from natural gas. Say you convert 1kW of natural gas to 0.5kW of electricity then uses that to produce 0.315kW of compressed hydrogen, that is then only used to an efficiency of 40-50% by the fuel cell giving 0.126kW to 0.1575kW to run the car on which is enough for half a kilometer. Running directly on natural gas would have been enough for a kilometer at least.
If that where an electric car you would have put around 0.45kW in the battery enough to drive 1.5 kilometer. So the electric vehicle here demands a bit more then half the fuel of CNG cars, Hydrogen powered fuel cell demands twice as much. It doesn't matter how many nuclear reactors you build if your gonna use hydrogen for transportation, it would be astronomical and as astronomically stupid. Even if you do it with thermochemical process built into high-temperature reactors (instead of just cooling of the heat). The world would need such a ridiculous amount of reactors that we can't possibly build them.


RE: electrolysis...
By H24U on 1/30/2010 8:59:01 PM , Rating: 2
Actually it is 85% ELECTROLYSIS NOT HYDROLYSIS. 2 different things, and that includes compression and 60% for the fuel cell vehicle. Get the facts straight.

With less than 20% of the southwest desert we could provide the whole nation (and more) with both solar electricity and hydrogen for transportation.

Paul Staples
h24u@hygen.com
707-667-5329


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