Wait, what?

I'm seeing stuff in the news about some research done by MIT (usually a pretty good bunch) which claims to use some combination of voodoo, a catalyst and some solar energy to crack water into hydrogen and oxygen. The numbers in their press release, as reported by Scientific American, are:

• Energy input from a "five meters by six meters" photovoltaic array.
• A time period of "less than four hours".
• A total amount of stored hydrogen/oxygen fuel of "enough energy for the average American home", which he quotes as "30 kilowatt-hours". (Holy shit, the average American home uses 30 kWh/day?!)

OK, let's do the maths.

• 5m x 6m = 30m^2 photovoltaic array, at the peak commercially available efficiency of 20%, at peak solar power density of roughly 1kW/m^2, that's 6kW of solar panels.
• 6kW over four hours gives 24kWh of electrical energy from the sunlight.

He claims to generate enough hydrogen/oxygen fuel to generate 30kWh, with an input of 24kWh of electricity. Now, even assuming that the electrolysis process is 100% efficient, one of two things MUST be true:

1. The 'catalyst' that he's developed is consumed in the process and it costs more than 6kWh to produce the amount he's quoting, OR
2. The second law of thermodynamics "doesn't apply because this is chemistry not physics." If anyone uses this argument I will personally punch them in the nipples.

My initial reaction to this claim was "thou shalt not suffer a witch to live", but instead I'm going to err on the side of assuming the reporting article is wrong and it actually says "enough energy for the average American home in conjunction with changes to make the home more efficient" or something, which could easily mean that they're generating 10-15kWh of fuel from the 24kWh of solar energy, which is an attainable target if you accept the existence of a fancy new catalyst.

Still, however impossible the initial claims, efficient storage of solar energy in the form of hydrogen is one piece of the puzzle for long-term renewable small-scale solar baseline power. I'll be keeping my eye on this one.

Stop with the hydrogen already, it's stupid.

I love hydrogen, really I do. It's a prime ingredient in the biggest bombs we can make. It makes a wonderful bang when you fill a balloon with it and then poke it with a match. It burns clean, producing nothing but chemically pure DHMO. But for the love of god, stop with the 'hydrogen economy' crap. It's terribly inefficient. Don't take my word for it, go ask a physicist.

Electric transportation is the way of the future, and it's awesome, but we need to ditch this fixation on hydrogen. Fuel cells are good for two things: Sounding cool, and distracting the public from battery electric vehicles. This whole hydrogen thing was started by car manufacturers back in the late '90s so they could look like they were saving the environment while they continued to build lounge-room-sized SUVs, and it was encouraged by the U.S. government because they couldn't figure out how to appropriately tax EVs. Petrol taxes elegantly combine paying for road wear caused with an incentive for efficiency by the vehicle in a way that is nigh impossible with EVs. But I digress.

Let's face it, physics is not on the side of hydrogen. First, you have to generate the hydrogen, which today is generally done by processing 'natural gas', the primary source of which is fossil fuels. Yes, your hydrogen fuel cell car will run off dinosaur farts just like your old banger does now. The only carbon neutral sources of hydrogen are processing biogas (unlikely to ever provide the quantities required) and electrolysis of water, which in the very best case is still less than 50% energy efficient.

Next, once you have your supply of pure hydrogen, you have to store it. This bit is a pain in the ass. The main technologies we currently have for hydrogen storage are high pressure tanks, cryogenic storage, and storage as metal hydrides. Compressing hydrogen to between 350 and 700 bar. for high pressure storage requires a large energy input, which is wasted as heat when the hydrogen cools to ambient temperature after compression. Cryogenic storage requires similar energy inputs to both compress and cool the hydrogen. Metal hydride storage systems are safer than high pressure systems but are heavy and require heating to 120-200°C to release the stored hydrogen.

Now, you can get to the cool bit, which is recombining the hydrogen with oxygen to produce actual turning of wheels and so forth. The only problem is that by now, less than a quarter of the energy you had in the first place is still available to you in the form of hydrogen. 75% of that energy is gone.

Compare this with a battery electric vehicle running with nanophosphate lithium batteries. Charging and discharging the battery requires power electronics which are typically around 80-90% efficient. Other than that, energy losses are minimal. Overall, a hydrogen infrastructure would require around three times as much input power as a battery-based infrastructure. And that's terrible.