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Power Science

How Artificial Leaves Could Generate Clean Hydrogen 101

Posted by Soulskill
from the leaving-well-enough-alone dept.
An anonymous reader writes "At Imperial College London, researchers have embarked on a £1m project to study, and eventually mimic, photosynthesis. Part of the 'artificial leaf' project involves working out exactly how leaves use sunlight to make useful molecules. The team then plans to build artificial systems that can do the same to generate clean fuels such as hydrogen and methanol. These would then be used in fuel cells to make electricity or to directly power super-clean vehicles."
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How Artificial Leaves Could Generate Clean Hydrogen

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  • by blueg3 (192743) on Wednesday August 12, 2009 @01:26PM (#29040811)

    If you get it by removing the same quantity of carbon from the air (which is what photosynthesis does), it's carbon-neutral. It's clean because it doesn't contain things other than methanol, and the combustion products of methanol are relatively harmless.

  • by TigerNut (718742) on Wednesday August 12, 2009 @01:34PM (#29040943) Homepage Journal
    One of the combustion products of methanol is formaldehyde, and that's not harmless.

    Linky to Wikipedia [wikipedia.org]

  • Re:New Idea? (Score:5, Informative)

    by Rei (128717) on Wednesday August 12, 2009 @01:36PM (#29040993) Homepage

    He was correct. Certain steps in the photosynthetic process are very efficient, but the fact that only part of sunlight is photosynthetically active, the fact that plants don't process all light that hits them, and that not all energy they produce goes into biomass, generally limits the total biomass yield to 3-6%. Food crops generally yield between a fraction of a percent and a couple percent of the solar energy that hits them as food, but practical growth limitations make that even lower (by a good margin). To give an example of how that comes into play, sugarcane is a rare photosynthesis exception, at about 8% efficiency turning sunlight to biomass, but only 0.13% solar efficiency [wikipedia.org] to ethanol. That's 4000 liters per hectare of 225W/m^2 insolation land. That's 7.1e13 joules of solar energy to prduce 9.36e10 joules of ethanol. Awful efficiency, no?

  • Re:New Idea? (Score:3, Informative)

    by MyLongNickName (822545) on Wednesday August 12, 2009 @01:41PM (#29041053) Journal

    Here is a link to one of the few intelligent articles I found written on the subject. link [cornell.edu]

  • by squoozer (730327) on Wednesday August 12, 2009 @03:41PM (#29042831)

    I would guess that they are intending to use the methanol on a fuel cell rather than a regular internal combustion engine. Fuel cells produce essentially nothing but co2 and water. It should also be fairl easy to put a catalytic converter on the exhaust to remove any traces of methanol. Over all I think methanol could be a great fuel.

  • Re:New Idea? (Score:4, Informative)

    by Rei (128717) on Wednesday August 12, 2009 @06:20PM (#29044747) Homepage

    1/3rd as much power huh? in terms of joules or BTUs, yes, but where one power source is coming from the ground, the other is coming from power plants, and we don't have those power plants!

    1) Hydrogen isn't "coming from the ground".
    2) We *do* have those power plants, according to the DOE.

    Also, the local grids (last mile) can't handle that extra load...

    3) Since when? Even a full recharge to a Volt every night -- 8kWh plus a little more for conversion losses (say, 9kWh total) -- can be done on a single normal 110V socket in 6 hours. How exactly is that going to tax the local grids?

    Also off-peak is NOT considered "night time" but varies by region and time of year. in the summer, off-peak is typically midnight to 5AM. but BEVs take 8-10 hours to charge, oops.

    "Oops yourself". First off, "Off peak" generally starts at around 11:00 and ends at around 6:00. 12 to 5 is just somewhat deeper of an off-peak than 11 to 6, but you're definitely not going to overload the grid. Secondly, 8-10 hours on even a 110V/15A socket (and a 110V/15A will *not* overload the grid) is 48 to 60 miles range per day. Only a small fraction of the US population drives that much. If you want to talk, say, dryer socket-level charging, even 100 miles of range is just over four hours.

    Also, once we move to fast charge, it will NOT be stady, stable off-peak loads.

    That's not how fast charge works. Commercial fast chargers tend to have battery banks that they draw from. The banks are trickle charged (and ideally, smart-charged).

    Also, if you read the link's data, they are NOT storing H2, they're making it as part of a catalytic process.

    A) What link are you talking about?
    B) Hydrogen cannot be made "in a catalytic process". It's an energy sink, not a source.

    It's only kept in short term, low pressure tanks for 12-36 hours.

    Doesn't matter. It's still hugely expensive. So is large-scale hydrogen production and compression equipment.

    These types of tanks are CHEAP

    They absolutely are not. Hydrogen tanks are typically composite (since they embrittle metals). Often carbon fiber with a polymer lining. Show me a large, cheap carbon fiber tank and I'll show you a living unicorn.

    efficient

    Nonsense. Electrolysis is 50-80% efficient (with the more efficient systems being more expensive due to lower throughput), and you generally lose 10-20% of the remaining energy in compression. Then you have the fuel cells at 40-60% efficiency (you can get slightly higher in the lab, but that's only under controlled conditions, with pre-compressed oxygen rather than uncompressed air). Or you have an H2 ICE generator, at ~40% efficiency.

    and have extremely little leakage

    Hydrogen leaks through steel at about 100 times the rate propane does (which is positively a leaker compared to gasoline). It is the easiest chemical on the world to leak, bar none.

    EV batteries contain toxins, rare chemicals, and though the most recent technologies are highly recyclable, its a messy expensive process, not to mentoin LiIon pack failure and fires...

    Wrong on every front. One, the types of batteries mainly being used for EVs today are lithium iron phosphate and manganese spinels. Neither of these are toxic. You can legally just throw them straight in the trash. Two, they contain no "rare chemicals" (fuel cells do, however! They use platinum). Three, the recycling process is neither "messy" nor "expensive"; most packs are having their recycling costs included in the purchase price. Four, LiP and LiMnO2 cells have almost no fire risk, unlike the LiCoO2 cells that most people are familiar with from laptops and cell phones (only Tesla is using those).

    I also read the DOE result when it came out recently, and there are a few things you should note: 1) the study completely ignored local grid distribution, and was a statement of average available energy across the USA (total poewr p

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