AskPablo: Let’s talk about H2, baby… (and EEStor)

Hypercar.gifI frequently get ask about H2, and I’m not talking about the Hummer H2 (that 8 mpg thing is dead to me), I’m talking about hydrogen. By the way, many tractor-trailers that you see on the highway get around 5 mpg, which is pretty good considering the huge load that they carry. This week I’ll be writing all about the problem of energy storage and other energy-related issues that we are facing in our carbon-constrained society.
Hydrogen is the most abundant element, and accounts for 75% of the mass of the universe. Hydrogen is found in concentrations of only 1 ppm in our atmosphere because it is actually so light that it can escape our atmosphere, however it does make up about 1/8th (by weight) of each H20 molecule. Many people make the mistake of calling hydrogen a fuel. Unlike hydrocarbon-based fuels, hydrogen does not naturally occur in any usable concentrations and must therefore be created chemically, or by electrolysis. I consider hydrogen more of an energy storage medium than a fuel. Unfortunately the problem of storing hydrogen is the major obstacle keeping us all from driving Hypercars. Hydrogen is very light but also takes up a lot of space. In addition to these two problems it has a very low energy density (around 286 kJ/g, or 68 kCal/g) so, even if you give up your entire trunk space, you would have trouble going anywhere even close to 300 miles on a single tank.

Aside from this huge issue there are other stigmas associated with hydrogen, tracing back to the Hinderberg accident. The fated blimp was actually coated in a substance very similar to rocket fuel and was ignited by static electricity. In fact, if you look back at the footage of the accident you will notice that the blimp stayed fairly level as it burned, proving that the fire was actually burning the explosive outer skin and not the hydrogen contained within. Because of this horrendous accident many people still think that a hydrogen fuel-cell vehicle is a bomb-on-wheels. However, since hydrogen is so light, any rupture of a fuel tank would result in its immediate heavenward departure, whereas a gasoline leak will make a nice carbeque.
While I am hopeful that a good storage system will be developed and we will be able to transition to a sustainable hydrogen economy I think we are still several years away from large-scale market availability of my dream car. What about other energy storage solutions? Well, the Toyota hybrid system uses batteries that store energy generated by a gasoline engine and regenerative braking but what else? Some people have increased the fuel economy of their Prius by converting it into a plug-in hybrid, where the batteries are charged by either solar power or grid power. Another option is to add solar panels to the roof rack or body panels to help keep the batteries charged. I have actually considered doing this to my non-hybrid vehicle to boost my fuel economy by offsetting the power draw by my AC, stereo, and lights.
My newest hope for vehicle-based energy storage though are capacitors. There is a very interesting article on Treehugger about the new EEStor capacitors. Benefits of these new capacitors over lead-acid batteries include almost unlimited charge cycles (without physical degradation), does not contain large amounts of toxic chemicals or heavy metals, it will be cost-competitive with batteries once production volumes are ramped up, and they can be fully charged in a matter of minutes, not hours. Unfortunately EEStor is very secretive and does not yet have a website. I will be watching closely as this new technology develops and will let you know of any major developments. It would be great if Toyota were to incorporate this technology in its hybrids to eliminate the need for chemical batteries. I would also like to see Toyota to make all of their hybrid vehicles plug-in and make it easier to install aftermarket photovoltaic cells.
Well, that’s all for this week. I hope that you learned something. I look forward to seeing your discussions on this topic and your questions for next week.
Pablo Paster, MBA
Sustainability Engineer

5 responses

  1. Hydrogen has a low Volumetric energy density, but an incredibly high gravimetric energy density. I think this distinction is important when mentioning the problems associated with hydrogen storage.
    Adam St. John
    Queen’s University Fuel Cell Research Centre.

  2. I think hydrogen explosions happen frequently enough – most commonly they are associated with charging lead-acid batteries – to demonstrate that hydrogen can be pretty dangerous stuff. Depending on hydrogen to dissipate before it can explode seems a fairly risky design strategy.

  3. Good one Pablo. It is also worth mentioning that gasoline stations have thousands of fires and several explosions every year, allowing for a fairly straightforward risk management calculation: e.g. deaths or injuries per vehicle mile driven with gas a fuel. And it is significant, which is why many states ban “self service” dispensing of gasoline.
    As a tangent to you excellent post, we already have a hydrogen economy in the US. I forgot the cite but have heard several times that the existing H2 market is over 9 million tons per year in the US alone. A very big chunk of that goes to the refining of gasoline, which is (depending on ones’ viewpoint) largely a hydrogen carrier. That exhaust plume you see in cold weather is water from combusted hydrogen, much of which was added at the refinery. I imagine if much of that 9 million tons of H2 were dirverted from refineries to H2 fuel cell vehicles. Dreaming my bu__.

  4. I hope there never will be a hydrogen economy, and that isn’t because I am a fan of the ICE – I’m not – or because I assume that it is dangerous.
    The one thing that wasn’t mentioned is the efficiency of hydrogen as enery storage.
    Huge amounts of electricity are needed to get hydrogen from any substance, including water.
    You would get four times LESS electricity out of hydrogen than from a battery if both “storage devices” were loaded with the same amount.
    Nice idea, but too inefficient.
    It’s better than burning oil products though, provides the hydrogen isn’t derived from them (which contain hydrogen atoms)

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