Energy research geekery – The hydrogen economy

“System-level energy efficiency is the greatest barrier to development of the hydrogen economy”, Shannon Page, et al, Energy Policy, 37 (2009), pp 3325-3335

“In the wonderful future, all our cars will run on hydrogen” – as said by approximately every futurist for about thirty years. So where is this hydrogen economy then?

Hydrogen is an energy carrier, like electricity. You have to put energy in to make it, and then you get energy out at the other end, from fuel cells that make electricity to turn motors. Fuel cells are clean, therefore hydrogen is clean, right?

Wrong, says more of the Canterbury researchers. This all depends upon the overall system efficiency, on the whole chain from where the energy comes from and how many steps there are along the way from the original source to the final, useful energy.

For a car right now, we dig up some oil, pump that to a refinery, convert it to petrol, ship and truck it to the petrol station, burn it in combustion engine. The useful energy coming out of this chain, motion in your car, is about 25% of the energy in the original oil. That’s not great, but hey, it worked for the entire Twentieth Century, so don’t knock it.

For a different energy chain, say battery powered cars with the eleccy coming from wind turbines, the energy chain goes: wind turbine -> grid transmission-> car battery -> electric motor. Overall efficiency? 70% Hell yeah.

For a hydrogen version, the chain goes: wind turbine -> central electrolysis -> hydrogen pipeline -> compression -> fuel cell -> electric motor. There’s losses at each stage, so overall efficiency? 25%

So if you want to use hydrogen, then you’ll need three times as many wind turbines to power your car, at three times the price. That’s a non-starter.

Ref to Energy Policy‘s September 2009 NZ special edition.

17 thoughts on “Energy research geekery – The hydrogen economy

    1. I’m just waiting for the scientific breakthrough that allows us to extract hydrogen from water for free.

      This might be about as likely as a pony that emits hydrogen instead of methane. 🙂

      1. I’m waiting for a breakthrough that shows the Second Law of Thermodynamics is less of a law, and more of a guideline.

        I’m not prepared to stake the future of humanity on that breakthrough though.

        (Hydrogen gets produced in cow stomachs, it just all gets grabbed by the methanogens. I now know more about the contents of cow stomachs than I ever thought I would.)

        1. You can run cars on water, but the Evil Oil Companies have supressed the technology and murder anyone who rediscovers it. Also, the Second Law Of Thermodynamics was passed at the behest of Big Oil lobbyists.

          I was told this by hippies and TV3, so it must be true.

          1. *shhh*

            The hippies are on to us. Don’t mention the Secret Cabal or the hippies will make papier-mache masks of our heads and stand around with placards and leaflets. And then we’ll be, well, pretty much not bothered.

  1. I agree mostly.

    There are also hydrogen fueled internal combustion engines to consider as a possibility.

    Also, you only look at energy efficiency. There are a bunch of other factors, including:
    – energy density => weight and range
    – capital cost and depreciation
    – fueling/recharge time
    – embodied energy and mineral resources

    I’d also point out that H2 is an important feedstock in industry (even in NZ) and almost none of the worlds current production uses electrolysis.

    1. Hydrogen fueled ICEs have an annoying habit of burning hot enough to create lots of NOx. Fuel cell + electric motor has an efficiency of about 44%, ICE about 25%.

      True, there’s lots of other factors at play here, but end-to-end efficiency is a pretty fundamental one. And yes, hydrogen can be refilled rapidly, when compressed, but the fuel tanks are still huge. Capital cost? Fuel cells are just silly money and, despite the billions spent on research, and the research leaders (Ballard) have given up on trying to produce fuel cells for cars.

      Yes, most of the world’s H2 comes from cracking natural gas, but if we’re trying to do this without making more carbon emissions, then that route is right out.

      As for whether battery electric vehicles are feasible in numbers big enough to make a difference to the climate, you’ll have to wait till tomorrow’s post.

      1. http://www.informaworld.com/smpp/444613474-21394688/content~db=all~content=a789006285

        I reckon NZ is at least ten years away from removing fossil fuel from electricity generation, even given the political will. Since we don’t have that, make that 20.

        Then there’s the use of fossil fuel in static direct applications (heating) to remove.

        After that we may have enough electricity to consider running vehicles on it without just burning more coal/gas in power stations.

        My view is we should be aiming to reduce vehicle use to at least average developed world levels, basically through price pressure and environmental redesign.

  2. I keep hoping for some breakthroughs in solar concentrator hydrolysis, but that doesn’t seem to be going anywhere much.

    There are bacteria that dump out hydrogen, but that’s fussy.

    I’ve read that there is 10x more hydrogen in a tank of petrol than in a tank of compressed hydrogen, which makes it likely that synthesizing petrol from captured carbon, and chewing it up and running the car on the hydrogen and capturing the carbon, is likely to be a better plan than trying to run the cars on straight hydrogen. Plus side is we’ve already got the distribution infrastructure done.

    1. I had this great idea for storing and delivering hydrogen. You attach your hydrogen atoms to a long-chain molecular backbone, preferably creating a substance that was liquid at room temperature. If that long chain was also combustable, then it could contribute to the energy carried.

      Then I realised that I’d invented petrol.

  3. Yeah, the whole “hydrogen economy” hype really annoys me. The average person thinks it is “fuel from water” and has “zero emissions except steam” etc., and doesn’t understand any of the energy balance, or net emissions, etc.

    It scares me that policies are made based on PR-appeal of a specific battery technology (hydrogen fuel cells/engines), which, to date, has been one of the poorer options.

    Is your figure for 25% of the original energy content of the oil include all the fuel used in transit of the fuel, etc? While an interesting number, as far as efficiency goes, it’s not very meaningful unless compared to an alternate use of the energy in that oil. (How would using the oil directly in power plants, then distributing through the power grid to electric cars, compare?)

    -B.

    1. Yup, it’s well to wheel. Actually, for oil, transport through pipelines is very efficient, more than 98~ or so, coz the only losses are through viscosity. For natural gas, there’s lots of compression to be done, dropping efficiency to 96.5%. For hydrogen, there’s one metric fucktonne of compression, plus losses coz hydrogen always leaks, so it ends up at about 94%.

      The article has overall efficiency for burning natural gas in a power station, then transmitting the eleccy to cars – 37%. That’s better than burning the gas directly in cars – 23% (and a bugger to start on a cold morning, many NZ cars used to run off CNG). So yeah, if you’ve got lots of natural gas, no renewables, and are prepared to continue to screw up the world’s climate, then burning it will be just fine. Luckily, NZ’s biggest gas fields are running out right now, so there’s a choice we don’t have to worry about.

      1. But lots of oil used in may parts of the world is transported via tanker, etc., or so is my impression? And I think most gasoline distribution is via truck in the USA.

        So, back-of-envelope-wise, those numbers would suggest that burning fossil fuels in power plants to feed electric vehicles still beats refining fuel, distributing it, and burning in IC engines (for efficiency, and therefore also greenhouse gas emissions). And, at that point, one can provide the electric power from a mix of sources, hopefully transition to sustainable sources over time. (Not thinking of NZ’s particular case necessarily, but of, say, the USA’s and other developed nations.)

        -B.

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