AutoBlogGreen Q&A with Prof. Joan Ogden and Stephen Ellis- Hydrogen efficiency
AutoblogGreen: During Ben Knight's (VP of Honda R&D America) presentation, he talked about the efficiency of hydrogen in terms of well to wheel and tank to wheel efficiency. What would go into that measurement?
Dr. Ogden: You start with the raw materials, a feed stock like natural gas or crude oil which come out the ground and those have to be processed and transported, in the case of crude oil you take it to a refinery. The trucks take that to the refueling stations and there is energy consumption and emissions at each step in that process. Once it's in the car, it's used there and that's well to wheel. With hydrogen, let's start with hydrogen from natural gas. At the natural gas well you take it out, process it a little bit, compress it, stick in the pipeline, and take it to the hydrogen plant. There you convert it, compress the hydrogen, and either put that in a truck or send it out by pipeline.
The discussion continues after the jump.
AutoblogGreen: For the CNG to hydrogen efficiency shown in the chart, what process would that be based on?
Dr. Ogden: It would based on converting natural gas to hydrogen by steam reformation which is a well established process. Large scale reformers can be 75-80 percent efficient.
Stephen Ellis: It's been explained to me that while people think that the hydrogen is coming solely from the natural gas, there's actually a component of the water.
Dr. Ogden: A lot of the hydrogen in the process actually comes from the water. In steam reforming, you have CH4 (methane) and H20 (water) which when combined in the presence of the catalyst, separates some of the H from the water.
Stephen Ellis: That's something that's misunderstood, everyone thinks that it's just that "fossil fuel" that it's coming from, when in fact it's both. You're getting some of that efficiency from removing the hydrogen from the water.
Dr. Ogden: It's a very efficient process, and you get a lot of energy out in the form of hydrogen. If you look at the overall greenhouse gas emissions, well to wheel, let's compare gasoline-hybrid to a hydrogen fuel cell car, with the hydrogen from natural gas route,. Depending on the study, there's a roughly 40 percent reduction in emissions. It varies depending on the assumptions about the fuel economy of one car vs another, but for the case that Ben [Knight] looked at which is the current gasoline and current hybrid, you do better than the hybrid and much better than the gasoline car.
AutoblogGreen: How does the cost of hydrogen from steam reformation compare to gasoline?
Dr. Ogden: There's a couple of things you have to add on to the cost. If you produce hydrogen from large scale steam reforming, the cost is on the order of $1.00- $1.50/kg which is equivalent to $1.00- $1.50/gallon gasoline. You can use the hydrogen more efficiently, but then you have to compress the hydrogen and deliver it, which might add another $1.00/kg and then the cost of the refueling station. Most studies that have looked at doing this at a large scale would say that hydrogen would cost somewhere between $2.00-$4.00/kg, depending on whether it's a fossil or renewable source and the scale of production, but that's a ball-park number.
Now let's look at the efficiency. You can use hydrogen in a fuel cell car with more than twice the efficiency of a current gasoline car and almost twice as much as a hybrid car. So now that $2.00-$4.00/kg is actually equivalent to more like $1.00-$2.00/gallon for gasoline because of the fuel economy effect. In other words, if you fill up your tank enough to go 250 miles, with gasoline that might mean ten gallons, and with hydrogen that might mean 4kg, so it's less fuel that you have to use because you have a higher efficiency.
Stephen Ellis: Here's a real world application, the current fuel cell car, not the concept, has a tank capacity of about 3.75kg of hydrogen and that goes over 200 miles. If you left your house with 3 gallons of gasoline you'd think you were empty.
AutoblogGreen: So we're in the ball-park already today as far as fuel cost?
Stephen Ellis: Absolutely. And one of Ben's other points which sometimes gets missed is that the weight of the car is already quite a bit higher (3600 lbs) than comparison gasoline and hybrid cars, so as the weight is reduced it only gets better. So these high levels of efficiency as impressive as they are will get better over time. We mentioned previously some of the landfills and the gases coming off those, and Prometheus down in Irvine is one those making thousands of gallons of liquefied natural gas a week now. That's an example of what is typically thought of as a fossil fuel, but now bio-methane, becomes a renewable feed-stock for hydrogen and dispels the whole myth of natural gas in hydrogen production. Now if we bring that bio-methane to the efficiency equation, it gets even better. If you took the Honda home energy system and add a small anaerobic digester to process food waste, clean it up and feed it to the home energy station, you have a home energy station for electricity, heat and fuel for the car. If you think about where we started with a comment about making hydrogen from fossil fuel, now look at where we're at, it's a big difference, so you can see why I'm passionate about taking this on. I think that's an untold story.
With the biofuel side of that, the bio-methane, there's all these other approaches, will society alter what it does, such as how it deals with it's garbage? Today, you have companies like Waste Management, having you separate your trash from your recyclables and your green waste. Taking that further, now provides the feedstock and the opportunity to plants and anaerobic digesters in an economic manner. Now these economies are relevant to what might happen. It's not economic today but it becomes economic as the cost of these other energy sources is rising and then it makes sense to do it.
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